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  • 1.
    Kellner, Hans
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Study of Non-metallic Inclusion in Alloy 8252017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    It is well known that inclusions affect the properties of steels and alloys. Therefore, it is important to understand what type of inclusions that exist and how they behave and especially with a focus on large size inclusions. Thus, the large size non-metallic inclusions in ferroalloy FeTi70R were investigated in two dimensions (2D) by using scanning electron microscopy (SEM) in combination with an energy dispersive technique (EDS). It was found that the FeTi70R ferroalloy contain complex oxide inclusions consisting mostly of CaO, SiO2 and TiOx. Furthermore, experimental trials were performed to investigate how these inclusions behaved when entering a melt. More specifically, a comparison between pure Fe and an Alloy 825 grade were made. These results determined the parameters effect on the transformation of the inclusions in the melt.

    The large size non-metallic inclusions in Alloy 825 during the ladle treatment were investigated during industrial trials by using both two dimensional (2D) and three dimensional (3D) microscopic investigations. The results showed that inclusions consisted of spherical oxides and clusters made up of oxides and nitrides. Further investigations found that the spherical inclusions were transformed from existing NMI in the FeTi70R ferroalloy and slag particles. As for the clusters, they originate from deoxidation products. Furthermore, small inclusions precipitated in the local zones around the added FeTi70R ferroalloy and titanium nitrides. Investigations also found that only Al2O3-MgO and TiN clusters exist after casting.

    Industrial trials were performed during the last period of the ladle treatment and using a combined electromagnetic (EMS) and gas (GS) stirring. The purpose to investigate the effect of different EMS directions on the agglomeration and on the removal of Al2O3-MgO and TiN clusters. The investigations were then performed in 3D after an electrolytic extraction of the metal samples. The results show that electromagnetic stirring in the upwards direction is best for the agglomeration of the Al2O3-MgO and TiN clusters. However, electromagnetic stirring in the downwards direction is more effective to remove clusters from the melt. This is in agreement with the theoretical predictions based on Stokes’, Brownian and Turbulent collisions. Also, the calculations showed that for Al2O3-MgO clusters with sizes <20 μm the Turbulent collision is the defining factor for agglomeration. However, both Stokes’ and Turbulent collisions are dominant for larger inclusions. For the TiN clusters, turbulent collisions is the dominant factor.

    Further investigations with more heats and stirring modes were done by using 2D microscopic investigations. More specifically, the number, size, composition and morphology of different inclusions were determined by using SEM in combination with EDS and Inca Feature analyses. The results show that the EMS in downwards direction with a 0.04 m3 min-1 gas flow rate promotes a general removal of Al2O3-MgO and TiN inclusions. Furthermore, that the upwards EMS direction promotes a drastically increase of inclusions having an equivalent size smaller than 11.2 μm. Moreover, the stirring with a 0.02 m3 min-1 gas flow rate has a better removal rate for both downwards and upwards stirring directions compared to the stirring with a 0.04 m3 min-1 gas flow rate. However, no influence on the inclusion composition and morphology could be seen from the different stirring modes.

  • 2.
    Kellner, Hans E. O.
    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.
    Memarpour, A.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of additions of FeTi70R alloy on inclusion characteristics in Fe-40Ni-20Cr steels2015In: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015, Chinese Society for Metals , 2015, p. 797-800Conference paper (Refereed)
    Abstract [en]

    It is well known that ferroalloys, which are used for alloying of different steels, contain different harmful non-metallic inclusions and impurities. As this can significantly affect the cleanliness of the steel (especially in production of high quality alloy steels), it is important to know what happens when ferroalloys are added to the melt. In this work, characteristics of non-metallic inclusions (such as composition, size and number) were investigated in the commercially produced FeTi70R ferroalloy (∼70% Ti), which is used in the steelmaking industry for deoxidation and alloying of different steel grades. It was found that this FeTi alloy contains some amount of complex oxides, which sizes can reach 50 - 150μm. A composition analysis of these complex inclusions showed that they contain mostly CaO (about 70%-98%) and TiOx-SiO2 (about 2%-28%). These large size inclusions can significantly decrease the cleanliness of the cast steels (especially by addition of FeTi alloys for a final correction of the steel composition before casting) and their final mechanical properties. Processes of transformation of these and other non-metallic inclusions, which are present in the FeTi70R ferroalloy, were investigated after immersion of this ferroalloy into a melt of a Fe or a Fe-40Ni-20Cr steel. Moreover, the non-metallic inclusions were investigated in samples taken at different moments during the industrial production of a Fe-40Ni-20Cr steel alloyed with the FeTi70R ferroalloy. The inclusions existing during the production were then compared to those that evolved during the immersion of a FeTi70 alloy in the Fe-40Ni-20Cr melt. This helps to understand what type of inclusions that formed when FeTi70R alloys are added to a Fe-40Ni-20Cr melt and to estimate the harmful effect of these non-metallic inclusions on the quality of this steel grade during commercial production.

  • 3.
    Kellner, Hans E O
    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.
    Memarpour, A.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Evolution of Non-Metallic Inclusions from FeTi70R Alloys during Alloying of Fe-40Ni-20Cr Steels2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArticle in journal (Refereed)
    Abstract [en]

    In this study, the composition, size, and number of large non-metallic inclusions (&gt;20μm) are investigated in a commercial refined FeTi70R alloy, which is used for deoxidation and alloying of different industrial high-quality steels. It is found that this ferroalloy contains different complex oxide inclusions, which sizes vary from 20 to 260μm. These different complex inclusions contain mostly CaO, SiO2, and TiOx. When adding FeTi70R alloy in the steel during the final stage of ladle treatment, these large size inclusions can significantly decrease the cleanliness and mechanical properties of steel. Therefore, the evolution and behavior of these inclusions after addition of this ferroalloy into the liquid iron or Fe-40Ni-20Cr steel are investigated in laboratory experiments. In addition, the results from the laboratory scale experiments are compared to results obtained from industrial heats using Alloy 825. A consideration of the evolution mechanism of large inclusions after an addition of a FeTi70R alloy helps to understand their behavior in the melt. It also helps to estimate their possible harmful effects on the quality of this steel grade during commercial production.

  • 4.
    Kellner, Hans E. O.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Dalarna University, Sweden.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sundqvist, Olle
    Memarpour, Arashk
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Estimation of Non-Metallic Inclusions in Industrial Ni Based Alloys 8252017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 88, no 4, article id UNSP 1600024Article in journal (Refereed)
    Abstract [en]

    It is well known that inclusions affect the properties of the steel and other alloys. The importance of understanding the behavior of the inclusions during production can never be overstated. This study has examined the main types of big size (> 10 mu m) inclusions that exist in Ni-based Alloy at the end of ladle treatment and after casting during industrial production of Ni based Alloys 825. Sources, mechanisms of formation and behavior of different type large size inclusions in Alloy 825 are discussed based on 2 and 3D investigations of inclusion characteristics (such as, morphology, composition, size, and number) and thermodynamic considerations. The large size inclusions found can be divided in spherical (Type I and II) inclusions and in clusters (Type III-V). Type I-A inclusions (Al2O3-CaO-MgO) originate from the slag. Type I-B inclusions and Type II inclusions consist of CaO-Al2O3-MgO and Al2O3-TiO2-CaO, respectively. Both types originate from the FeTi70R alloy. Type III clusters (Al2O3-MgO-CaO) are formed during an Al deoxidation of the Ni-based alloy. Type IV clusters (Al2O3-TiO2-CaO) formed from small inclusions, which are precipitated in local zones which contain high Ti and Al levels. These clusters are transformed to Type III clusters over time in the ladle. Finally, Type V clusters are typical TiN clusters.

  • 5.
    Kellner, Hans Erik Olof
    et al.
    KTH. Dalarna Univ, S-79188 Falun, Sweden..
    Karasev, Andrey Vladimirovich
    KTH.
    Sundqvist, Olle
    Sandvik Mat Technol AB, S-81181 Sandviken, Sweden..
    Jönsson, Pär Göran
    KTH.
    TiN Particles and Clusters during Ladle Treatments of Ni-based Alloy 825 using Different Stirring Modes2018In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, no 2, p. 292-298Article in journal (Refereed)
    Abstract [en]

    Today, titanium is often used in steelmaking not only for deoxidation but also for micro-alloying and alloying for a wide range of steel grades. Therefore, many studies are focused on investigations on the formation and behavior of Ti-containing non-metallic inclusions (such as oxides, nitrides and carbides) during production of different Ti-containing steels and their effect on final steel properties. This study has examined the behavior of TiN clusters and particles in the melt during the ladle treatment of Alloy 825 containing up to 1.2 wt% of Ti. The industrial trials were performed at the end of the ladle treatment by using argon gas in combination with electromagnetic stirring using an upwards or a downwards stirring direction. Metal samples were taken before and after ladle treatment to enable three-dimensional investigations of non-metallic inclusions and clusters. The composition, size and number of particles and clusters were determined after electrolytic extraction of the metal samples by using SEM in combination with EDS. It was found that agglomerations of TiN clusters and particles in the melt are faster during an upwards stirring in comparison to a downwards stirring. However, the removal of clusters from the melt is more effective when using a downwards stirring direction compared to when using an upwards stirring in combination with gas stirring. It was also found that the Turbulent collision is the dominant factor for the agglomeration of TiN particles in the melt.

  • 6.
    Kellner, Hans
    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.
    Sundqvist, Olle
    Sandvik Materials Technology.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of Stirring Mode on Non-Metallic Inclusions in Alloy 825 during Ladle TreatmentManuscript (preprint) (Other academic)
    Abstract [en]

    It is well known thatinclusions affect the properties of steels and alloys. Therefore, it is essentialto understand what types of inclusions that exist and how they behave duringthe production. This study has examined the behavior of Al2O3-MgOand TiN inclusions in the melt during the ladle treatment of Ni-based Alloy825. The effects of different directions of electromagnetic stirring (EMS) incombination with different gas flows were investigated based on two dimensionaldeterminations of the inclusion characteristics on a polished surface of themetal samples by using Inca Feature analysis. More specifically, the number,size, composition and morphology of different inclusions were determined byusing SEM in combination with EDS. The results show that the use of EMS in thedownwards direction in combination with a 0.04 m3 min-1gas flow rate promotes a significant removal of Al2O3-MgO and TiN inclusions. Furthermore, the use of an upwards EMSstirring direction promotes a drastical increase of the amount of inclusionshaving an equivalent size smaller than 11.2 µm. Also, the use of both stirringdirections in combination with a 0.02 m3 min-1 gasflow rate promote a ~20% to ~60% removal of Al2O3-MgO and TiN inclusions for most heats. No influence on the composition andmorphology could be seen from the different stirring modes.

  • 7.
    Kellner, Hans
    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.
    Sundqvist, Olle
    Sandvik Materials Technology.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of the Stirring Mode on the Behavior of Al2O3–MgO Particles and Clusters during Ladle Treatment of Ni-based Alloy 8252017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, article id 1700165Article in journal (Refereed)
    Abstract [en]

    It is well known that inclusions affect the properties of alloys. Therefore, the importance of understanding what inclusions exist and how they behave cannot be overstated. This study has examined the behavior of Al2O3–MgO particles and clusters in the melt during the ladle treatment of Alloy 825, who is a Ni-based Alloy. The effect of different stirring directions of electromagnetic stirring in combination with gas stirring is discussed based on three-dimensional investigations of the clustered particles. More specifically, the composition, size, and number of particles and clusters are determined after electrolytic extraction of metal samples by using SEM in combination with EDS. The results show that the agglomeration of Al2O3–MgO particles in the melt is faster for an upward induction stirring combined with a gas stirring in comparison to a downward stirring combined with a gas stirring. However, the total removal of clusters from the melt is more effective when using a downward induction stirring compared to when using an upward induction stirring, especially for large size clusters (>11.2 mm). The effect of the different stirring modes on the behavior of the Al2O3–MgO particles and clusters in the melt for the ladle treatment experiments agree with the theoretical predictions based on Stokes’, Brownian, and Turbulent collisions.

  • 8.
    Kellner, Hans
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Högskolan Dalarna.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sundqvist, Olle
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Investigations of TiN Particles and Clusters during Ladle Treatments of Ni-based Alloy 825 using Different Stirring Modes2017In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, no 2Article in journal (Refereed)
    Abstract [en]

    Today, Titanium is often used in steelmaking not only for deoxidation but also for micro-alloying and alloying for a wide range of steel grades. Therefore, many studies are focused on investigations on the formation and behavior of Ti-containing non-metallic inclusions (such as oxides, nitrides and carbides) during production of different Ti-containing steels and their effect on final steel properties. This study has examined the behavior of TiN clusters and particles in the melt during the ladle treatment of Alloy 825 containing up to 1.2wt% of Ti. The industrial trials were performed at the end of the ladle treatment by using argon gas in combination with electromagnetic stirring using an upwards or a downwards stirring direction. Metal samples were taken before and after ladle treatment to enable three-dimensional investigations of non-metallic inclusions and clusters. The composition, size and number of particles and clusters were determined after electrolytic extraction of the metal samples by using SEM in combination with EDS. It was found that agglomerations of TiN clusters and particles in the melt are faster during an upwards stirring in comparison to a downwards stirring. However, the removal of clusters from the melt is more effective when using a downwards stirring direction compared to when using an upwards stirring in dombination with gas stirring. It was also found that the Turbulent collision is the dominant factor for the agglomeration of TiN particles in the melt.

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