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  • 1.
    Andersson, Margareta
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Appelberg, Jesper
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, Hiroyuki
    Tohoku University, Institute of Multidisciplinary Research for Advanced Materials.
    Kitamura, Shinya
    Tohoku University, Institute of Multidisciplinary Research for Advanced Materials.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Some Aspects on Grain Refining Additions with Focus on Clogging during Casting2006In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 6, p. 814-823Article in journal (Refereed)
    Abstract [en]

    Some ideas of how to study optimum conditions for implementation of grain refining in liquid steel processing with focus on how to avoid clogging are discussed. It is assumed that the inclusions most beneficial for grain refining are known from studies by physical metallurgists. The challenge for a process metallurgist is how to provide a homogeneous distribution of grain refiners at the onset of solidification. Four different ways of providing information to succeed with this are discussed. Thermodynamic modeling can be used to predict what additions to make to create potential grain refiners, if relevant thermodynamic data is available. Mathematical fluid-flow modeling can be used to study where to add potential grain refiners. It is discussed that the tundish is the most appropriate reactor to add grain refiners, since enough time is given to a complete mixing of the grain refiner into the steel before the steel enters the mold. By using the scanning laser microscopy technique it is possible to study which potential grain refiners has the lowest attraction forces between each other. This is important in order to minimise growth of inclusions when they collide during transport in the tundish, which can lead to the formation of larger inclusions that do not serve as useful grain refiners. Finally, it is suggested that laboratory experiments are carried out in order to study the tendency for nozzle clogging, before the use of grain refiners is tested in industrial scale.

  • 2.
    Appelberg, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, H.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    In situ studies of misch-metal particle behavior on a molten stainless steel surface2008In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 495, no 1-2, p. 330-334Article in journal (Refereed)
    Abstract [en]

    The use of misch-metal is widely spread among the stainless steel producers. Casting problems like clogging are common when using these additions. Information about Ce-La-Al-O particles formed due to the addition of misch-metal in the ladle is scarce in the open literature. The aim of this study is to increase the knowledge of the particle behavior and the particle characteristics in two stainless steels resulting from the addition of misch-metal. The in situ particle behavior has been studied using a Confocal Laser Scanning Microscope.

  • 3. Chen, J.
    et al.
    Su, Z. -J
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, J. -C
    Criterion for dendrite fragmentation of steel under imposition of linear traveling EMS2011In: 2010 International Conference on Advances in Materials and Manufacturing Processes, ICAMMP 2010, 2011, p. 84-91Conference paper (Refereed)
    Abstract [en]

    In the fragmentation theory of T. Campanella et al, the local remelting of dendrite arms is induced by the solute-rich fluid flow. Based on this theory, the effects of linear EMS intensity and solute content on CET of steel are investigated. The conclusions are as follows: The criterion for dendrite fragmentation under linear EMS is derived based on dendrite fragmentation theory by T. Campanella et al. And the criterion is verified with steel experiments. It is valid for steel under the Linear EMS. Investigation is carried out on relation between critical volume fraction of solid and solute content at the time of dendrite fragmentation (CET occurrence). It is concluded that critical volume fraction of solid is small with low EMS intensity and it decreases with the increase of solute content (C, Mn). The reason is that it causes that flow in the mushy zone becomes small which leads to CET occurrence difficult.

  • 4. Chen, J.
    et al.
    Su, Z. -J
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    He, J. -C
    Critical conditions for dendrite fragmentation of low carbon steel in travelling electromagnetic field2010In: Dongbei Daxue Xuebao/Journal of Northeastern University, ISSN 1005-3026, Vol. 31, no 12, p. 1717-1720+1732Article in journal (Refereed)
    Abstract [en]

    To investigate the effect of travelling electromagnetic field on dendrite fragmentation in solidification process, the 0.22 wt%~0.34 wt%C steel was tested for its solidifying behavior in travelling electromagnetic field. Observing the solidification structures of casting blanks under different magnetic flux density, the distributions of secondary dendrite arm spacing were investigated and the functional relationship between secondary dendrite arm spacing and cooling rate in solidification was discussed, as well as the effect of travelling electromagnetic field on the columnar-to-equiaxed transition (CET) position. The solidification rate and solid fraction when CET occurs were calculated. The critical conditions for dendrite fragmentation in travelling electromagnetic field is derived and verified by the testing results of low carbon steel. Thus, the relationship between the average velocity of the liquid-phase and the critical solid volume fraction when CET occurs was obtained.

  • 5.
    Janis, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Inoue, Ryo
    Tohoku Univ..
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Characteristics of Ti-Ce Complex Deoxidation Products in a Fe-20mass%Cr Alloy2009In: STEEL RES INT, ISSN 1611-3683, Vol. 80, no 6, p. 450-456Article in journal (Refereed)
    Abstract [en]

    The particle characteristics such as size distribution, composition and morphology have been studiedin an Fe-20mass%Cr alloy as a function of holding time at 1600°C. The alloy was deoxidised with Tiand Ce, followed by holding at 1600°C and cooling to 1400°C and quenching. The inclusion particleswere investigated on a surface of film filter with an open pore size of 0.05 or 5 μm after electrolyticextraction of the metal samples. Different electric charge and electrolytes (2%TEA and 10%AA) werecompared for extraction of the Fe-20mass%Cr alloy. 300 Coulombs with 10%AA was found mostsuitable for the electrolytic extraction of particles to determine the particle composition and sizedistribution. Most of the particles were found to be complex oxides containing Ti, Ce and Cr.Furthermore, the composition of the particles was found to change from a high Ce-content to a highCr-content with longer holding time at 1600°C.

  • 6.
    Janis, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Dissolution of Nitrides and Precipitation of an AusteniticPhase on the Surface of Fe-20%Cr alloys2010Report (Other academic)
    Abstract [en]

    New phases have been observed on surfaces of metal specimens duringcooling after heat treatment at 1200, 1300 and 1400 °C of an Fe-20mass% Cr alloywith different nitrogen contents (65, 248 and 490 ppm) and deoxidised by Ti andZr. These phases were assumed to be related to a phase transformation. Theanalysis of nitrogen content in matrix metal and new phase crystals was carried outbased on point analysis of nitrogen using SEM. According to obtained results itwas concluded that the nitrogen had been dissolved from the nitrides during 60minutes of heat treatment at high temperature and diffused in to the matrix. Theseareas of enriched nitrogen content were then transformed to a new phase duringcooling. This new phase was assumed to be austenite because the nitrogen is a wellknown element for promotion of austenite formation. The possibility of austeniteformation in Fe-20mass% Cr alloys with different nitrogen content was consideredand confirmed thermodynamically by using the Thermo-Calc software.

  • 7.
    Janis, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of Secondary Nitride Particles on Grain Growth in a Fe-20 mass% Cr Alloy Deoxidised with Ti and Zr2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 3, p. 476-483Article in journal (Refereed)
    Abstract [en]

    The pinning effects of different particles on grain growth were investigated in Fe-20 mass% Cr alloys deoxidised with Ti and Zr. More specifically, in-situ observations of the specimen surface were made during heat treatment at 1 200 and 1 400 degrees C in a High Temperature - Confocal Scanning Laser Microscope (HT-CSLM). Initially, primary and secondary particles were investigated using thermodynamic equilibrium calculations and the SEM/EDX observations. Thereafter, the pinning effect of secondary nitride particles on grain boundary migration and the kinetics of the grain growth process were investigated. It was found that secondary nitride particles generally have a considerable effect on the pinning of grain boundary migration during heating treatment. This is especially true for heat treatment at 1 400 degrees C. Despite that the pinning effect of TIN particles decreases due to dissolution of these particles, the implicit pinning effects of ZrO2, ZrO2-ZrN and ZrO2-ZrN-TiN particles appear. Thus, despite that TIN individually is ineffective in causing grain-boundary pinning at high-temperature, TiN is effective as a compound with ZrO2 and ZrN in pinning grain-boundaries at high temperatures. The changing of the uniformity of grain size distributions during grain growth at different N contents and temperatures was discussed based on the consideration of the geometric standard deviation of the grain size distribution (sigma(g)).

  • 8.
    Janis,, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of Primary and Secondary Particles on Grain Sizein a Fe-20mass% Cr Alloy Deoxidised with Ti and Zr2010Report (Other academic)
    Abstract [en]

    Because of the high and volatile Ni price in recent times, it becomesmore important to develop ferritic stainless steels with low level of Ni. Here,it is known that these steel grades usually contain oversized grains, which asa consequence leads to poor mechanical properties. One way to deal withthis problem is to control the microstructure and the size of grains in ferriticstainless steels. This would also make ferritic stainless steels morecompetitive in comparison to the more commonly used austenitic stainlesssteels. This study focuses on the grain refining effect of particles present in aferritic stainless steel. The particles were created by additions of Ti and Zr into a liquid Fe-20mass% Cr alloy, before the start of solidification. Aconstant O content (150 ppm) together with varying N contents (65, 248 and490 ppm) in the metal samples were used to vary the number, compositionand location of the precipitated particles. The grain sizes and particles werestudied in as-cast samples as well as for specimens heat treated for 60minutes at 1200 and 1400°C. It was found that the formation of particles isenhanced by an increased N content in the alloy. Based on SEMdeterminations, the precipitated particles were divided as primary (mainlyZr-oxides and Zr-nitrides) and secondary (mainly Ti-nitrides) particles andthe effect was studied for each of the types. An increased content of primaryparticles as “nucleators” for precipitation of α-ferrite during solidification ofthe melt lead to an increased formation of equiaxed small-size grains. Inaddition, an increased N content in the metal samples resulted in anincreased number of secondary particles, which are located near the grainboundaries. Therefore, the pinning effect of these particles on grain growthincreased at a holding temperature of 1200oC. However, most of the nitrideswere found to dissolve during heating and holding at a 1400 °C temperature.Thus, as a consequence, the pinning effect of these particles on grain growthdecreased rapidly with the holding time.

  • 9.
    Janis, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Inoue, Ryo
    Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan.
    Karasev, Andrey Vladimirovich
    Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan.
    Characteristics of Ti-Ce complex deoxidation products in Fe-20mass% Cr alloy2008In: Scanmet III: Proceedings of the 3rd International Conference on Process Development in Iron and Steelmaking, 2008, p. 163-172Conference paper (Refereed)
  • 10.
    Janis, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Inoue, Ryo
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effects of Nitride-Oxide Particles on Solidified Structure inFe-20mass%Cr Alloy Deoxidised with Ti/M (M = Zr or Ce)2010Report (Other academic)
    Abstract [en]

    The ratio of equiaxed grains on a cross section and average grain sizein Fe-20mass% Cr alloy deoxidised with Ti/M (M = Zr or Ce) were studiedas function of nitrogen content and particle characteristics such as sizedistribution, morphology and composition. Fe-20mass%Cr alloys weremelted at 1600ºC, deoxidised, cooled to 1400ºC followed by waterquenching. The particles were investigated on a surface of film filter afterelectrolytic extraction of metal samples with 10%AA electrolyte. It wasfound that the number of particles increases with increasing the N content.The as-cast solidification structure and grain size were clearly affected bythe number of oxide and oxide-nitride particles in Ti/Zr experiments. Theeffect in the Ti-Ce case was almost undetectable.

  • 11.
    Janis, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.
    Inoue, Ryo
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effects of Primary Oxide and Oxide-Nitride Particles on the Solidification Structure in a Fe-20 mass%Cr Alloy Deoxidised with Ti and M (M = Zr or Ce)2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 2, p. 221-229Article in journal (Refereed)
    Abstract [en]

    The ratio of equiaxed grains on a cross section and the size of equiaxed grains in a Fe-20 mass% Cr alloy deoxidised with Ti/M (M = Zr or Ce) were studied as function of nitrogen content and particle characteristics such as size distribution, morphology and composition. Fe-20 mass% Cr alloys were melted at 1 600 degrees C, deoxidised, and cooled to 1 400 degrees C followed by water quenching. Thereafter, the particles were separated from the matrix using electrolytic extraction using a 10%AA electrolyte and collected on a film-filter surface. The inclusion characteristics were determined using SEM. It was found that the number of particles increases with an increased N content. Furthermore, that the solidification structure was clearly affected by the number of primary oxide and oxide-nitride particles in the Ti/Zr deoxidation experiments. However, a similar effect could not be detected in the Ti/Ce deoxidation experiments.

  • 12.
    Janis, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, Hiroyuki
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    An experimental study on the influence of particles on grain boundary migration2010In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 45, no 8, p. 2233-2238Article in journal (Refereed)
    Abstract [en]

    The pinning effect of particles on grain boundary migration was studied in a Fe-20 mass % Cr alloy deoxidised with Ti and Zr. The different nitrogen contents (65, 248 and 490 ppm) were used to vary the number of precipitated inclusions. The specimens from equiaxed zones of metal samples with different particle densities were examined by in situ observations during a 60-min holding time at 1200 and 1400 degrees C in a Confocal Scanning Laser Microscope. The change of particles pinning effect on the grain growth was described by an average grain size, (D) over bar (A), and the ratio between the perimeter and area of grains, P-GB/A(G). It was found that the pinning effect of particles (mostly complex Ti-Zr oxynitrides) on grain growth decreased with a decreased nitrogen content in the metal. Furthermore, the effect of particles decreased with an increased temperature of treatment, due to the reduction of the number of particles on the grain boundaries.

  • 13. Lei, Hong
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Ji-Cheng
    Mathematical Model for Nucleation, Ostwald Ripening and Growth of Inclusion in Molten Steel2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 12, p. 1735-1745Article in journal (Refereed)
    Abstract [en]

    Numerical simulation is a powerful tool to investigate inclusion behavior in the molten steel Although many mathematical models have been developed to predict inclusion collision growth behavior in different metallurgical reactors the inclusion size distribution had to be obtained by experiment or assumption Thus a general nucleation-growth model which involves in chemical reaction homogeneous nucleation and growth kinetics is developed to investigate the inclusion nucleation Ostwald ripening Brownian collision-growth Stokes collision growth and turbulent collision-growth In order to speed up the calculation the deoxidation products are divided into two parts The first part only consists of embryos and directly numerical simulation is used to solve the differential equations The second part only consists of inclusion particles and particle size-grouping method is introduced to solve the related equations Numerical results showed that the predicted inclusion size distributions are consistent with previous experimental data With the increasing diffusion coefficient the peak value diameter keeps unchanged and the maximum number density decreases With the increasing turbulent energy dissipation rate the peak-value diameter and the maximum number density decrease under the assumption on floating-out of larger inclusions

  • 14. Li, Dewei
    et al.
    Su, Zhijian
    Chen, Jin
    Wang, Qiang
    Yang, Ying
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Marukawa, Katsukiyo
    He, Jicheng
    Effects of Electromagnetic Swirling Flow in Submerged Entry Nozzle on Square Billet Continuous Casting of Steel Process2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 7, p. 1187-1194Article in journal (Refereed)
    Abstract [en]

    In this study, a new method for swirling flow generation in submerged entry nozzle (SEN) in continuous casting of steel process has been proposed. A rotating electromagnetic field is set up around the SEN to induce swirling flow in it by the Lorentz force. And this kind of electromagnetic swirling flow in the SEN is proposed to use in square billet continuous casting of steel process. The effects of coil current intensity and nozzle structure on the flow and temperature fields in the SEN and mold are numerically simulated and verified by an electromagnetic swirling model experiment of low melting point alloy. The overall results of the study show that the magnetic flux density and the swirling flow velocity in the SEN increase with the increase of coil current intensity. The largest swirling flow velocity in the SEN can reach about 3 m/s when coil current intensity 500 A, frequency 50 Hz. The electromagnetic swirling flow in the SEN can reduce the impinging depth of the flow and increase the upward flow. An impinging flow near the mold corner can be observed. The flow field changes mentioned above result in a uniform temperature field in the mold, increase the meniscus temperature, effectively increase the temperature at the mold corner. The divergent nozzle used in this new process also reduces the impinging depth, increases the upward flow and makes the meniscus temperature increase significantly.

  • 15. Li, Dong-gang
    et al.
    Wang, Qiang
    Li, Guo-jian
    Lv, Xiao
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Ji-cheng
    Diffusion layer growth at Zn/Cu interface under uniform and gradient high magnetic fields2008In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 495, no 1-2, p. 244-248Article in journal (Refereed)
    Abstract [en]

    As a common phenomenon occurring in many material processes, diffusion may induce significant changes in composition and microstructure near the interface. In the present study, liquid/solid (Zn/Cu) interface diffusion experiments in high magnetic fields (up to 12 T) were conducted and the thickness changes of diffusion layer under different magnetic field conditions were examined. It was found that there were no noticeable effects of high magnetic fields on the formation of intermetallic phases at the interface. However, the magnetic flux density exerted a non-linear influence on the diffusion layer thickness. This phenomenon should be attributed to the effect of magnetic fields suppressing natural convection and inducing thermo-electromagnetic convection. In addition, the diffusion of Zn into Cu could be retarded by a magnetic field gradient. These results indicate that both the strength and the gradient of high magnetic fields can be used to control the diffusion behavior.

  • 16. Li, Donggang
    et al.
    Wang, Qiang
    Li, Guojian
    Ma, Xiaomin
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Jicheng
    Reactive Diffusion at the Liquid Al/Solid Cu Interface in a High Magnetic Field2011In: Materials and Manufacturing Processes, ISSN 1042-6914, E-ISSN 1532-2475, Vol. 26, no 6, p. 821-825Article in journal (Refereed)
    Abstract [en]

    The kinetics of the reactive diffusion at the liquid Al/solid Cu interface was investigated at T = 973 K, 1023 K, and 1073K in a high magnetic field of 11.5 T. During the annealing process, three stable compounds (delta, xi(2), and eta(2)) layers were formed at the interface of the couples, and a power function relationship between the mean thickness of the diffusion layers and the annealing time kept stable. Without magnetic field, the exponent of the power function for each compound layer was higher than 0.5, but it was close to or even smaller than 0.5 with a magnetic field. Compared with the field-free environment, the migration of the liquid/solid interface due to interdiffusion decreased in the presence of a magnetic field. A considerable decrease in the effective diffusion coefficient under a magnetic field provided a likely explanation for the experimental results.

  • 17.
    Liu, Qiang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Zhang, Hongwei
    Wang, Qiang
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of heat treatment on microstructure and mechanical properties of Ti-alloyed hypereutectic high chromium cast iron2012In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 52, no 12, p. 2288-2294Article in journal (Refereed)
    Abstract [en]

    The effect of heat treatment on the microstructure and mechanical properties of Ti-alloyed hypereutectic High Chromium Cast Iron (HCCI) containing Fe-17 mass%Cr-4 mass%C-1.5 mass%Ti was investigated. The size distribution and the volume fraction of carbides (M7C3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It was found that the number of fine secondary M7C3 carbides with a size below 1 μm increases with lower holding temperatures and shorter holding times during heat treatment. The number of coarse primary M7C 3 carbides with a size above 11.2 μm increases with increasing holding temperatures and longer holding times. In addition, the number of TiC carbides increases with increasing holding times, and martensite units are more refined at longer holding times and lower holding temperatures, respectively. Moreover, the volume fraction of martensite increases with increased holding times. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI.

  • 18.
    Liu, Qiang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Estimation of the Maximum Carbide Size in a Hypereutectic High Chromium Cast Iron Alloyed with Titanium2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 12, p. 2176-2183Article in journal (Refereed)
    Abstract [en]

    In this study, in order to obtain complete size distribution results, the maximum carbide size in a Fe-17 mass% Cr-4 mass% C hypereutectic High Chromium Cast Iron (HCCI) produced with different cooling conditions, titanium additions and heat treatment conditions was determined by using the statistics of extreme values (SEV) method. In addition, the shape factor, circularity, was estimated in order to classify the type of carbides (primary M7C3 carbides, TiC carbides and secondary M7C3 carbides). Compared to the smaller size carbides, such as TiC carbides and secondary M7C3 carbides, it was found that the slope of the extreme value distribution (EVD) regression lines is lower for the large sized carbides such as primary M7C3 carbides than for the smaller carbides. Moreover, it was found that the circularity value for the larger size carbides is higher than for the smaller carbides. Furthermore, the estimated and observed maximum carbide sizes were compared with each other for all carbide types. The characteristic of the different carbide types are summarized and classified based on the shape factor. Finally, the relationship between the carbide size distribution including the maximum carbides size and mechanical properties is discussed based on the combination of a size distribution analysis and a maximum size analysis.

  • 19.
    Liu, Qiang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Shibata, Hiroyuki
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Dynamic Precipitation Behavior of Secondary M7C3 Carbides in Ti-alloyed High Chromium Cast Iron2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 7, p. 1237-1244Article in journal (Refereed)
    Abstract [en]

    In-situ observations on the dynamic precipitation behavior of secondary carbides in Ti-alloyed High Chromium Cast Iron (HCCI) were performed by using a Confocal Laser Scanning Microscope (CLSM). Moreover, the detailed characterization of the microstructure before and after heat treatment was performed by using scanning electron microscopy (SEM). The secondary carbides, which precipitate from the matrix during heat treatment, were identified as M7C3 type carbides by using transmission electron microscopy (TEM). The number, size and volume of secondary carbides during heating, holding and cooling process were quantitatively evaluated based on the in-situ observation and SEM results. It was found that ferrite (alpha) and secondary carbides start to precipitate from the matrix at around 575 degrees C and 840 degrees C, respectively, during the heating process. In addition, the in-situ results showed that the number of secondary carbides increase with an increased heating temperature and time. Moreover, it was found that the size of these secondary carbides increase at higher temperatures and longer holding times. However, the number of secondary carbides increased with a decreased temperature. Finally, it was found that the volume fraction (similar to 5%) of secondary carbides was not changed to a large extent for the different heat treatment conditions being investigated.

  • 20.
    Liu, Qiang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhang, Hongwei
    Wang, Qiang
    Zhou, Xiangkui
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of cooling rate and Ti addition on the microstructure and mechanical properties in as-cast condition of hypereutectic high chromium cast irons2012In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 52, no 12, p. 2210-2219Article in journal (Refereed)
    Abstract [en]

    The effect of cooling rate and Ti additions on the mechanical properties and carbides characteristics such as morphology, size distribution and composition was studied in high-chromium cast irons containing Fe-17 mass%Cr-4 mass%C. Based on the size distribution, composition and morphology, M 7C3 type carbides were roughly classified into "primary M7C3 carbides" and "eutectic M7C3 carbides" with a 11.2μ m border size. Thereafter, the change of the solidification structure and especially the refinement of carbides size were determined. It was found that both the size and number values should be summarized systematically for primary M 7C3 carbides and eutectic M7C3 carbides, respectively. Also, TiC carbides with a high formation temperature can not only act as a nuclei of M7C3 carbides, but they also contain a Ti(C, N) core. In the as-cast condition, the bulk hardness of the cast irons increases with an increased Ti content. In addition, the wear loss increases with an increased Ti content. Neither the bulk hardness nor the wear loss did change too much with an increased cooling rate.

  • 21.
    Liu, Qiang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhang, Hongwei
    Wang, Qiang
    Zhou, Xiangkui
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Solidification and phase transformations of Ti-added hypereutectic high chromium cast irons2012In: 1st International Conference on Ingot Casting, Rolling and Forging, 2012Conference paper (Refereed)
  • 22. Liu, Tie
    et al.
    Wang, Qiang
    Zhang, Hong-Wei
    Lou, Chang-Sheng
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Ji-Cheng
    Effects of high magnetic fields on solidification microstructure of Al-Si alloys2011In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 46, no 6, p. 1628-1634Article in journal (Refereed)
    Abstract [en]

    The effects of high magnetic fields on the solidification microstructure of Al-Si alloys were investigated. Al-7.2 wt%Si and Al-11.8 wt%Si alloys were solidified in various high magnetic fields at different cooling rates. The secondary dendrite arm spacing (SDAS) of the primary Al dendrites and the lamellar spacing (LS) of the eutectics were measured. It was found that the application of a high magnetic field could decrease the SDAS of the primary Al dendrites in Al-7.2 wt% Si alloys and the LS of the eutectics in Al-11.8 wt% Si alloys. The effects of the high magnetic field on the SDAS decreased with increasing cooling rate. The decrease in the SDAS and LS can be attributed to the decrease of the solute diffusivity in the liquid ahead of the solid/liquid interface during the growth of the dendrite and eutectic. This decrease is caused by the high magnetic field which can damp the convection and avoid its contributions to the diffusion.

  • 23. Lou, Changsheng
    et al.
    Wang, Qiang
    Wang, Chunjiang
    Liu, Tie
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Jicheng
    Migration and rotation of TiAl3 particles in an Al-melt solidified under high magnetic field conditions2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 472, no 1-2, p. 225-229Article in journal (Refereed)
    Abstract [en]

    The effects of high magnetic fields on the migration and rotation of TiAl3 particles in an Al-7 wt.% Si alloy were studied. Without magnetic fields, the rod-like TiAl3 particles segregate at the lower part of the solidified structure. Under high uniform magnetic fields, these particles rotate to an orientation with their longitudinal axes parallel to the direction of the magnetic flux. The segregation of the particles reduces with the increase of the magnetic flux density. A negative gradient field enhances the effect of the uniform magnetic field. By altering high magnetic fields, Al-Si alloy samples containing homogeneously distributed and preferably aligned TiAl3 particles were prepared.

  • 24. Mu, W.
    et al.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of the inclusion size and sulfur content on the intragraunlar ferrite transformation in steels with Ti2O3 additions2015In: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015, Chinese Society for Metals , 2015, p. 767-771Conference paper (Refereed)
    Abstract [en]

    The effect of the inclusion size and the sulfur content on the intragranular ferrite (IGF) formation in steels with Ti2O3 additions was investigated. The nuclei inclusion is identified as a TiOx+MnS phase. TiOx was found to be the nucleation site for an intragranular ferrite formation. Also, the inclusion size increases from a range of 0.3 to 6.8μm to a range of 0.85 to 13.53μm after the addition of Ti2O3 powders into the molten steel. The probability of an IGF nucleation increases with an increased inclusion size. It is found that a 1.7μm inclusion size is large enough to be an effective nucleation site. It is also noted that the nucleation probability decreases with an increased sulfur content. The tendency of the probability of an IGF nucleation could fit the tendency of the area fraction of an IGF with an increased sulfur content.

  • 25.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Shibata, Hiroyuki
    Tohoku Univ, Inst Multidisciplinary Res Adv Mat, Aoba Ku, 2-1-1 Katahira, Sendai, Miyagi 9808577, Japan..
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    High-Temperature Confocal Laser Scanning Microscopy Studies of Ferrite Formation in Inclusion-Engineered Steels: A Review2018In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 70, no 10, p. 2283-2295Article, review/survey (Refereed)
    Abstract [en]

    The concepts of oxide metallurgy and inclusion engineering can be utilized to improve the properties of low-alloy steels. These concepts aim at controlling the formation of intragranular ferrite (IGF), often a desirable microstructure providing good mechanical properties without the need for expensive alloying elements. IGF formation is stimulated to occur at non-metallic inclusions and form an arrangement of fine, interlocking ferrite grains. A method that has contributed significantly to investigations in this field lately is high-temperature confocal laser scanning microscopy (HT-CLSM). HT-CLSM is suited for in situ studies of inclusion behavior in liquid steel and phase transformations in solid-state steel, where in particular, displacive phase transformations can be studied, since they provide sufficient topographic contrast. The purpose of the present report is to provide a brief review of the state of the art of HT-CLSM and its application for in situ observations of ferrite formation in inclusion-engineered steels. The scientific literature in this field is surveyed and supplemented by new work to reveal the capability of HT-CLSM as well as to discuss the effect of factors such as cooling rate and parent grain size on IGF formation and growth kinetics. The report concludes with an outlook on the opportunities and challenges of HT-CLSM for applications in oxide metallurgy.

  • 26.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of Sulfur Content on Inclusion and Microstructure Characteristics in Steels with Ti2O3 and TiO2 Additions2014In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, no 12, p. 2907-2916Article in journal (Refereed)
    Abstract [en]

    The effect of the sulfur content on the inclusion and microstructure characteristics of steels where Ti2O3 and TiO2 have been added was studied. Based on the microscopic examinations, it is found in the steel samples with Ti2O3 additions that the area fraction of intragranular ferrite decreases from 52.68% to 39.09% as the sulfur content increases from 0.009 mass.% to 0.030 mass.%. In the steel samples with TiO2 additions, this value also decreases from 49.05% to 36.26% as the sulfur content increases. The nucleant inclusion was identified as a TiOx+MnS phase based on SEM-EDS measurements as well as on equilibrium calculations with thermodynamic calculation software, Thermo-Calc. Also, TiOx was found to be the nucleation site for an intragranular ferrite formation. Moreover, the nucleation probability increases with an increased inclusion size. It is also noted that the nucleation probability decreases slightly with an increased sulfur content. The minimum size of TiOx+MnS inclusions for an IGF nucleation is about 0.85 mu m in the present samples. Furthermore, this minimum size of TiOx inclusions is shifted to a size of about 0.5 mu m by excluding the depth of a MnS layer. In addition, the effective nucleation size range of TiOx inclusions in the steels, where Ti2O3 and TiO2 had been added, is smaller than that of TiN+Mn-Al-Si-Ti-O inclusions in steel samples where TiN had been added.

  • 27.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Prediction of Intragranular Ferrite Nucleation in Steels with Ti-oxide and TiN AdditionsManuscript (preprint) (Other academic)
    Abstract [en]

    The present work provides a method to calculate the critical diameters of TiO, TiN and VN inclusions for IGF nucleation. It is noted that the critical diameters of TiO, TiN and VN inclusions for IGF nucleation were calculated to be 0.192, 0.355 and 0.810 μm. The calculation result was in agreement with the experiment data in the steels with TiN and Ti-oxide additions. Moreover, it is the first attempt to predict the critical diameters of inclusions in the steels containing different contents of Mn and S. The critical diameters were increased with the increase of Mn content. However, the S content does not have a direct effect on the critical diameters for IGF nucleation.

  • 28.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Shibata, H.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Inclusion and Microstructure Characteristics in Steels with TiN Additions2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 3, p. 339-348Article in journal (Refereed)
    Abstract [en]

    The quantitative analysis of inclusion and microstructure characteristics in the steels with TiN additions has been studied. The typical inclusion was detected to be a TiN+Mn-Al-Si-Ti-O+MnS phase. This identification was based on the measurements of scanning electron microscopy with energy-dispersive X-ray spectrometer (SEM-EDS), electron probe microanalysis (EPMA), which equipped wavelength-dispersive X-ray spectroscopy (WDS), and equilibrium calculations by using the commercial software Thermo-Calc. TiN was found to be the effective nucleation site for the formation of intragranular ferrite (IGF). Furthermore, the increased inclusion size led to the increased probability of IGF nucleation. In addition, this probability of IGF nucleation was slightly decreased with the increased sulfur content. This tendency could fit the tendency of the area fraction of IGF in the steels containing different sulfur contents.

  • 29.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, Hiroyuki
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Inclusion and Microstructure Characteristics in Steels with TiN AdditionsManuscript (preprint) (Other academic)
    Abstract [en]

    The quantitative analysis of inclusion and microstructure characteristics in the steels with TiN additions has been studied. The typical inclusion was detected to be a TiN+Mn-Al-Si-Ti-O+MnS phase. This identification was based on the measurements of scanning electron microscopy with energy dispersive X-ray spectrometer (SEM-EDS), electron probe microanalysis (EPMA) which equipped wavelength dispersive X-Ray spectroscopy (WDS) and equilibrium calculations by using the commercial software Thermo-Calc.. TiN was found to be the effective nucleation site for the formation of intragranular ferrite (IGF). Furthermore, the increased inclusion size led to the increased probability of IGF nucleation, and this probability of IGF nucleation was slightly decreased with the increased sulfur content. This tendency is in agreement with the tendency of the area fraction of IGF in the steels containing different sulfur contents. 

  • 30.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Prediction of intragranular ferrite nucleation from TiO, TiN, and VN inclusions2016In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 51, no 4, p. 2168-2180Article in journal (Refereed)
    Abstract [en]

    The current study presents a method to calculate the critical diameters of TiO, TiN, and VN inclusions for intragranular ferrite (IGF) nucleation in steels. Based on the calculation results, it was noted that the critical diameters of TiO, TiN, and VN inclusions for IGF nucleation were 0.192, 0.355, and 0.810 μm. The calculation results agreed with the experiment data of a minimum inclusion size for IGF nucleation in the actual steel samples. Moreover, the effects of Mn, C, and S contents on the critical diameters of inclusions were investigated. It was found that the critical diameters of TiO, TiN, and VN inclusions increased with the increasing Mn and C contents. In addition, it was found that S does not have a direct effect on the critical diameters of TiO, TiN, and VN inclusions. However, the increasing S content led to an increased amount of MnS precipitation in the actual steels. This is negative, since MnS is ineffective nucleation site for IGF nucleation. When the amount of MnS increases in steels, the area fraction of IGF slightly decreases. This fact has been investigated by in situ observation experiments.

  • 31.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. McMaster University, Canada.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Recent Aspects on the Effect of Inclusion Characteristics on the Intragranular Ferrite Formation in Low Alloy Steels: A Review2017In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 36, no 4, p. 309-325Article in journal (Refereed)
    Abstract [en]

    Intragranular ferrite (IGF), which nucleates from specific inclusion surfaces in low alloy steels, is the desired microstructure to improve mechanical properties of steel such as the toughness. This microstructure is especially important in the coarse grain heat affected zone (CGHAZ) of weldments. The latest review paper focusing on the role of non-metallic inclusions in the IGF formation in steels has been reported by Sarma et al. in 2009 (ISIJ int., 49(2009), 1063-1074). In recent years, large amount of papers have been presented to investigate different issues of this topic. This paper mainly highlights the frontiers of experimental and theoretical investigations on the effects of inclusion characteristics, such as the composition, size distribution and number density, on the IGF formation in low carbon low-alloyed steels, undertaken by the group of Applied Process Metallurgy, KTH Royal Institute of Technology. Related results reported in previous studies are also introduced. Also, plausible future work regarding various items of IGF formation is mentioned in each section. This work aims to give a better control of improving the steel quality during casting and in the heat affected zone (HAZ) of weldment, according to the concept of oxide metallurgy.

  • 32.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of Carbon Content on the Potency of the Intragranular Ferrite Formation2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 3, p. 311-319Article in journal (Refereed)
    Abstract [en]

    The effect of the carbon content on the potency of the intragranular ferrite (IGF) formation for each inclusion size is investigated in the present work. The TiN inclusion was detected to be the effective nucleation site for the IGF formation in the Fe-0.2 mass% C alloy and the Fe-0.4 mass% C alloy. It is noted that the potency of the IGF formation for each inclusion size is decreased with the increase of carbon content. Moreover, the critical diameters of the TiN, TiO, and VN inclusions in the steels with different carbon contents are calculated based on the classical nucleation theory. The calculated critical diameter is also found to be decreased with the increase of carbon content. This is in agreement with the experiment results. Finally, the decrease of the potency of IGF formation for each inclusion size is due to a larger amount of pearlite formation in the steel containing a higher carbon content, which is detected by differential scanning calorimetry (DSC) measurements.

  • 33.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Shibata, H.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ferrite Formation Dynamics and Microstructure Due to Inclusion Engineering in Low-Alloy Steels by Ti2O3 and TiN Addition2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 4, p. 2133-2147Article in journal (Refereed)
    Abstract [en]

    The dynamics of intragranular ferrite (IGF) formation in inclusion engineered steels with either Ti2O3 or TiN addition were investigated using in situ high temperature confocal laser scanning microscopy. Furthermore, the chemical composition of the inclusions and the final microstructure after continuous cooling transformation was investigated using electron probe microanalysis and electron backscatter diffraction, respectively. It was found that there is a significant effect of the chemical composition of the inclusions, the cooling rate, and the prior austenite grain size on the phase fractions and the starting temperatures of IGF and grain boundary ferrite (GBF). The fraction of IGF is larger in the steel with Ti2O3 addition compared to the steel with TiN addition after the same thermal cycle has been imposed. The reason for this difference is the higher potency of the TiOx phase as nucleation sites for IGF formation compared to the TiN phase, which was supported by calculations using classical nucleation theory. The IGF fraction increases with increasing prior austenite grain size, while the fraction of IGF in both steels was the highest for the intermediate cooling rate of 70 °C/min, since competing phase transformations were avoided, the structure of the IGF was though refined with increasing cooling rate. Finally, regarding the starting temperatures of IGF and GBF, they decrease with increasing cooling rate and the starting temperature of GBF decreases with increasing grain size, while the starting temperature of IGF remains constant irrespective of grain size.

  • 34.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, Hiroyuki
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ferrite Formation Dynamics and Microstructures in Inclusion Engineered Steels with Ti2O3 and TiN AdditionsManuscript (preprint) (Other academic)
    Abstract [en]

    The dynamics of intragranular ferrite (IGF) formation in inclusion engineered steels with Ti2O3 and TiN additions were investigated using in-situ high temperature confocal laser scanning microscopy (CLSM). Furthermore, the chemical composition of the inclusions and the final microstructures after continuous cooling was investigated using electron probe microanalysis (EPMA) and electron backscatter diffraction (EBSD), respectively. The results show that there is a significant effect of the chemical composition of the inclusions, the cooling rate and the prior austenite grain size on the phase fractions and the starting temperatures of IGF and grain boundary ferrite (GBF) formation. The fraction of IGF is larger in the steel with Ti2O3 addition compared to the steel with TiN addition after the same thermal cycle has been imposed. This is because the TiOx phase provides more potent nucleation sites for IGF than the TiN phase does. The fraction of IGF in the steels was highest after at an intermediate cooling rate of 70 ºC/min since competing phase transformations were avoided, however, the IGF was refined with increasing cooling rate. In addition, the IGF fraction increases and the starting temperature of GBF decreases with the increasing prior austenite grain size, however, the starting temperature of IGF keeps almost the value when the grain size changes.

  • 35.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, Hiroyuki
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Combination of in situ microscopy and calorimetry to study austenite decomposition in inclusion engineered steels2015In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArticle in journal (Refereed)
    Abstract [en]

    In situ high-temperature confocal laser scanning microscopy and differential scanning calorimetry studies of ferrite formation in inclusion engineered (Ti2O3 and TiN) steels have been performed. The applied methodology allows distinction between intragranular ferrite, grain boundary ferrite, and pearlite. The effect of the inclusions and cooling rates on the initiation of phase transformation and the final microstructure is discussed. It is concluded that the applied hybrid methodology could provide vital details of solid-state phase transformations within the field of inclusion engineering.

  • 36.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. McMaster University, Canada.
    Xuan, Changji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Uddeholms AB, Sweden.
    Shibata, H.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wetting and agglomeration behavior of inclusion and intragranular ferrite formation kinetics in steel with TiO2 addition according to inclusion engineering2017In: AISTech - Iron and Steel Technology Conference Proceedings, Association for Iron and Steel Technology, AISTECH , 2017, Vol. 3, p. 3027-3036Conference paper (Refereed)
    Abstract [en]

    The comprehensive study of inclusion and microstructure characteristics in steel with TiO2 addition has been presented in this work, including wetting behavior between TiO2 and pure Fe, evaluation of inclusion agglomeration tendency, effective nuclei inclusion identification and in-situ observation of intragranular ferrite (IGF) formation. The obtained results show that TiO2 is an effective additive because it is strong wetting with liquid iron and has obvious dispersion potency. Thereafter, the effective nuclei inclusion to induce IGF formation in steel with TiO2 addition is characterized as Ti3O5 phase. The kinetic study of IGF formation using high temperature confocal laser scanning microscope shows that the fraction of IGF increases as the cooling rate increases from 3.6 to 70 °C/min and with increasing prior austenite grain size. Furthermore, it is noted that IGF morphology is refined and the onset temperatures of IGF and GBF decrease with increasing cooling rate. Finally, the onset temperature of GBF formation is higher for the steel containing a smaller grain size, however, the onset temperature of IGF formation is independent of the grain size. This work aims to give a better control of the inclusion modification as well as improving the steel quality in secondary refining and casting process, according to the concept of inclusion engineering.

  • 37.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Liquid-solid interface free energies for metals from free-volume method and interface structural model2006In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 6, p. 795-800Article in journal (Refereed)
    Abstract [en]

    The thermodynamic approximate-expression for liquid-solid interface free energy which has its origin in the loss of configurational entropy due to the adjustment of the liquid to a boundary was derived. Triangular-square-pentagonal lattices were proposed for a structural model of the liquid-solid interface. Calculated values from the thermodynamic approximate-expression and the interface structural model showed a fair agreement with previous experimental data.

  • 38. Nakajima, Keiji
    Preface to the Special Issue on "Cutting Edge of Computer Simulation of Solidification and Casting"2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 12, p. 1723-1723Article in journal (Other academic)
  • 39.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Preface to the Special Issue on "Cutting Edge of Computer Simulation of Solidification, Casting and Refining"2014In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, no 2, p. 253-253Article in journal (Refereed)
  • 40.
    Nakajima, Keiji
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Hasegawa, H
    Khumkoa, S
    Hayashi, M
    Effect of catalyst on heterogeneous nucleation in Fe-Ni-Cr alloys2006In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 6, p. 801-806Article in journal (Refereed)
    Abstract [en]

    In order to elucidate the nature of heterogeneous nucleation, a differential scanning calorimetry (DSC) thermal analysis of Fe-Ni-Cr alloys (Ni + Cr content = 30 mass% (constant); Ni content: 7.5 to 29.3 mass%) containing TiN and Al2O3 was conducted. Then, special attention was paid to the difference in the phase of the primary crystal nucleated by the triggering effect of a catalyst (nucleating agent). The solidification and transformation mode appearing during cooling in these alloys is classified into three cases: F mode, FA mode, and A mode. The change of modes and the critical undercooling (Delta T) depend on the kind of catalyst used as well as on the chemical composition. In addition, in spite of the kind of primary crystal, the value of Delta T is always smaller in the order of TiN < Al2O3. These findings are the same as those for Fe-Ni alloy, although Fe-Ni-Cr alloys have the advantage that the increase of Cr content can trigger the crystallization of the primary crystal of the delta phase, which consequently can reduce Delta T and extend the region of low Delta T. The total concentration of catalyst molecules (C-1), as well as the interface free-energy ratio ((gamma(CL)-gamma(SC))/gamma(LS)), is one of the most significant factors in explaining undercooling for heterogeneous nucleation. (gamma(CL)-gamma(SC))/gamma(LS) is related to the kind of catalyst used and the chemical composition, and C-1 is related to the crystallized content of catalyst. As a matter of fact, the number of catalysts supplied to the solidification front has a practical effect on the control of the solidification-structure.

  • 41.
    Nakajima, Keiji
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Qiang
    Preface to the Special Issue on "Cutting Edge of Computer Simulation of Solidification, Casting and Refining"2017In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 36, no 4, p. 307-308Article in journal (Refereed)
  • 42.
    Nakajima, Keiji
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhang, Hongwei
    Oikawa, Katsunari
    Ohno, Munekazu
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Methodological Progress for Computer Simulation of Solidification and Casting2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 12, p. 1724-1734Article, review/survey (Refereed)
    Abstract [en]

    The dramatic progress made over the last 10 to 15 years in the field of computer simulation of solidification and casting is greatly due to the supports by academic as well as industrial research The driving force behind this undertaking was the promise of predictive capabilities that will allow process and material developments Here the recent works on modeling were summarized for the macrosegregation in the macroscale simulation and the Cellular Automaton the solidification path combined with the microsegregation the phase-field model in the meso-scale and micro-scale simulation

  • 43. Nomoto, Sukeharu
    et al.
    Minamoto, Satoshi
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Numerical Simulation for Grain Refinement of Aluminum Alloy by Multi-phase-field Model Coupled with CALPHAD2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 7, p. 1019-1023Article in journal (Refereed)
    Abstract [en]

    The multi-phase field method and CALPHAD (calculation of phase diagram) are applied to the study of the equiaxed solidifications in the Al-Ti-B and Al-Si-Ti-B systems by coupled with thermodynamic and diffusion databases. In these calculations, recalescence phenomenon is considered on the basis of the latent heat, and a plot of the seed density-radius distribution is obtained by calibration with experimental data. The calculated solidified-grain sizes are in quantitative agreement with the experimental measurements for various hypoperitectic compositions.

  • 44. Ono, Hideki
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Agawa, Shingo
    Ibuta, Toshio
    Maruo, Ryota
    Usui, Tateo
    Formation Conditions of Ti2O3, MgTi2O4, Mg2TiO4, and MgAl2O4 in Ti-Mg-Al Complex Deoxidation of Molten Iron2015In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, no 3, p. 241-251Article in journal (Refereed)
    Abstract [en]

    The relationships of the compounds in the Mg-Ti-Al-O system in equilibrium with molten iron are investigated at temperatures ranging from 1873 to 1973 K, and the thermodynamic calculations are conducted in avoiding Al2O3 or spinel MgAl2O4 formation and for inclusion control. The equilibrium relations between the compounds (Mg2TiO4, MgTi2O4, or MgAl2O4) and the composition of solutes in steel are clarified. The conditions are shown that the transformation of the stable compound from Mg-Ti spinel to Mg-Al spinel occurs at Mg contents ranging from 1 to 10 ppm by mass. It is also found, on the Mg-Ti spinel, the stable compound is transformed from inverse-spinel Mg2TiO4 to normal-spinel MgTi2O4 at Ti = about 60 ppm by mass. In addition, the stable compound is transformed from MgTi2O4 to Ti2O3 at Ti about 1000 ppm by mass.

  • 45. Ono, Hideki
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ibuta, Toshio
    Usui, Tateo
    Equilibrium Relationship between the Oxide Compounds in MgO-Al2O3-Ti2O3 and Molten Iron at 1 873K2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 12, p. 1955-1958Article in journal (Refereed)
    Abstract [en]

    It is important to determine the equilibrium relationship between the oxide compounds in MgO-Al2O3-Ti2O3 and molten iron to avoid Al2O3 or MgO Al2O3 formation and for inclusion control In this study we investigated the formation conditions of MgTi2O4 in preference to MgAl2O4 at 1 873 K The phase stability regions of MgAl2O4 and MgAl2O4 or Ti2O3 were determined at 1 873 K in MgO-Al2O3-Ti2O3 At a low titanium content of less than 0 1 mass% and when [mass ppm Mg]=3 MgAl2O4 forms at more than [massc%Al]=0 08 and the region of MgAl2O4 formation widens as the titanium content of the molten iron decreases Accordingly it is necessary to lower the Al content and to adjust the Ti content to an appropriate concentration range to form MgTi2O4 instead of MgAl2O4

  • 46. Ono, Hideki
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Maruo, Ryota
    Agawa, Shingo
    Usui, Tateo
    Formation Conditions of Mg2TiO4 and MgAl2O4 in Ti-Mg-Al Complex Deoxidation of Molten Iron2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 7, p. 957-964Article in journal (Refereed)
    Abstract [en]

    It is important to study the complex deoxidation equilibrium of molten iron in Ti-Mg-Al system from the view point of inclusion control. The equilibrium experiments between molten iron and TiOx-MgO-Al2O3 slag and the thermodynamic calculation on the complex deoxidation are conducted at 1973 K in the present study. The liquid phase region of TiOx-MgO-Al2O3 system in equilibrium with molten iron is clarified at 1973 K. The equilibrium compounds which are coexisted with the slag on the liquidus curve in the system are identified to be Mg2TiO4, and MgAl2O4. The equilibrium relation between the deoxidation products (Mg2TiO4 or MgAl2O4) and the composition of solute elements in steel is investigated, and the conditions that Mg2TiO4 forms instead of MgAl2O4 nor Al2O3 are examined in the complex deoxidation of Ti-Mg-Al system. When the aluminum content of molten iron is under 4 mass ppm, Mg2TiO4 forms over the wide concentration range. The concentration range of MgAl2O4 formation widens as the aluminum content of molten iron increases. It is necessary to increase Mg content and to decrease Al content in order to form Mg2TiO4 in the Ti-Mg-Al complex deoxidation of molten iron in the range Ti<0.01 mass%. However, it is difficult in the range of Ti>0.01 mass% to form Mg2TiO4.

  • 47. Shibata, Hiroyuki
    et al.
    Watanabe, Yusuke
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kitamura, Shin-ya
    Degree of Undercooling and Contact Angle of Pure Iron at 1 933 K on Single-crystal Al2O3, MgO, and MgAl2O4 under Argon Atmosphere with Controlled Oxygen Partial Pressure2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 7, p. 985-991Article in journal (Refereed)
    Abstract [en]

    Solid or molten oxides are considered to act as nucleation sites during continuous steel casting. The influence of the kind of oxide crystal and atmospheric oxygen partial pressure on the degree of undercooling and contact angle of pure molten iron on oxide substrates was measured by the sessile drop method. On Al2O3 and MgAl2O4 substrates, we found that the change in the degree of undercooling was dependent on the existence of a reaction layer and its thickness. On an MgO substrate, since no reaction layer formed, the degree of undercooling was small and was governed by the lattice misfit parameter. The equilibrium contact angle of a molten iron drop on the FeAl2O4 layer formed between the Al2O3 substrate and drop was about 100 degrees; a similar contact angle was obtained on MgAl2O4. The contact angle on MgO changed during observation due to the evaporation of Mg.

  • 48.
    Strandh, Jenny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eriksson, Robert
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A mathematical model to study liquid inclusion behavior at the steel-slag interface2005In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 45, no 12, p. 1838-1847Article in journal (Refereed)
    Abstract [en]

    The separation of non-metallic inclusions at the interface between the steel and the slag in the ladle, tundish and mold is an essential part of the production of clean steel. It is therefore, of great importance to have a deep understanding of the phenomena controlling the transfer of inclusions from the steel to the slag layer. In this work a mathematical model, derived from the equation of particle motion, have been used to study the transfer of liquid inclusions to slags. The effects of the drag, added mass, buoyancy and rebound force on the inclusion transfer are considered. The model relies, to a great extent, on the availability of accurate information of the magnitude of a number of physical properties of the involved phases. Among those properties, the interfacial tension between the phases and the slag viscosity were found to be the most critical. Due to the fact that the availability of experimentally obtained high-temperature physical property data, relevant to the industrial conditions, is scarce in the literature several different model descriptions have been used in this work to estimate these properties. The mathematical model has been used to investigate the separation of liquid non-metallic inclusions, of different size and composition, to a number of different industrial ladle slag compositions.

  • 49.
    Strandh, Jenny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eriksson, Robert
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Solid inclusion transfer at a steel-slag interface with focus on tundish conditions2005In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 45, no 11, p. 1597-1606Article in journal (Refereed)
    Abstract [en]

    The separation of non-metallic inclusions from the steel to the slag phase in the ladle during secondary steel making operations and in the tundish and mold during casting is very crucial to the production of clean steel. In this work a theoretical study of the separation of solid inclusions, alumina and others, at the steelslag interface applied to the actual conditions in the tundish has been carried out. The theoretical model is based on the equation of motion with the following forces acting on an inclusion as it tries to cross the interface between the metal and the slag; buoyant, added mass, rebound and drag force. A sensitivity analysis study was carried out in order to clarify which of the parameters in the model that had the largest influence on the inclusion displacement. The results showed that the interfacial tensions (sigma(MI), sigma(IS), sigma(MS)) and the slag viscosity (us) have the largest influence on the predicted displacement. It was also concluded that the overall wettability should be positive and that the slag viscosity should be as low as possible to obtain the most favorable conditions for inclusion transfer at the steel-slag interface.

  • 50. Su, Zhi-Jian
    et al.
    Chen, Jin
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Ji-Cheng
    Criterion for Dendrite Fragmentation of Carbon Steel under Imposition of Linear Travelling EMS2009In: STEEL RESEARCH INTERNATIONAL, ISSN 1611-3683, Vol. 80, no 11, p. 824-833Article in journal (Refereed)
    Abstract [en]

    In this study the columnar-to-equiaxed transition (CET) of carbon steel with 0.22-0.98 mass%C is investigated, based on the dendrite fragmentation theory of T. Campanella et al. The following conclusions are obtained: The criterion for dendrite fragmentation under linear EMS is obtained and verified by the 0.22-0.98 mass%C steel experiments. Investigation is carried out on the relation between the superficial velocity of the liquid phase and the actual velocity of the interdendritic liquid and the volume fraction of solid at the time of dendrite fragmentation (CET occurrence). At the same superficial velocity, the dendrite fragmentation critical volume fraction of solid is smaller in the case of high carbon steel. As a result, the CET occurrence is more difficult in the case of high carbon steel. Dendrite fragmentation induced by EMS is confirmed by the fragments of dendrite arms observed in the macrostructure. The length of dendrite fragmentation observed is about 1mm

12 1 - 50 of 78
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