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  • 1.
    Nabeel, Muhammad
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A study of micro-particles in the dust and melt at different stages of iron and steelmaking2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The dust particles generated due to mechanical wear of iron ore pellets and clusters formed in molten stainless steel alloyed with rare earth metals (REM) are considered in this study. Firstly, the influence of the characteristics of iron ore pellets, applied load on a pellet bed and partial reduction of the pellets on the size distribution of the generated dust was investigated. Secondly, REM clusters are investigated to evaluate the size distribution of the clusters. Also, an extreme value distribution (EVD) analysis has been applied for the observed REM clusters.

    The large sized pellets showed 10-20% higher wear rate than small sized pellets during wear in a planetary mill. Moreover, an increase of ~67% was observed in the friction and dust generation in the pellet bed as the applied load increased from 1 to 3 kg. Also, it was observed that a higher friction in the pellet bed can lead to an increased amount of airborne particles. The mechanical wear experiments of pellets reduced at 500 °C (P500) and 850 °C (P850) showed that P500 pellets exhibit ~16-35% higher wear rate than unreduced pellets. For the P850 pellets, the wear is inhibited by formation of a metallic layer at the outer surface of the pellets. The mechanism of dust generation has been explained using the obtained results.

    A reliable cluster size distribution of REM clusters was obtained by improving the observation method and it was used to explicate the formation and growth mechanism of REM clusters. The results show that the growth of clusters is governed by different types of collisions depending on the size of the clusters. For EVD analysis three different size parameters were considered. Moreover, using the maximum length of clusters results in a better correlation of EVD regression lines compared to other size parameters. Moreover, a comparison of predicted and observed maximum lengths of clusters showed that further work is required for the application of EVD analyses for REM clusters.

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  • 2.
    Nabeel, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Frykholm, R.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Influence of alloying elements on Ni distribution in PM steels2014In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 57, no 2, p. 111-118Article in journal (Refereed)
    Abstract [en]

    Powder metallurgical (PM) steels with elemental Ni additions exhibit non-homogenous microstructures with soft Ni rich areas, lean in C, after conventional sintering. Though, the exact correlation between the distribution of Ni and mechanical properties is not well known and depends on the conditions, e.g. the load state, it is desirable to be able to control the distribution of Ni since it plays a major role in the properties of Ni PM components. By introducing other alloying elements, the microstructure homogeneity of Ni containing PM steels, can be influenced. Thus, the effect of common alloying elements on the homogeneity of sintered microstructures has been investigated in the present work. It is found that additions of either C or Mo have minor effect on Ni distribution in the Fe-Ni system. However, addition of both C and Mo to Fe-Ni improves the Ni distribution. In addition, a strong interaction between Ni and Cu is observed and it enhances the Ni homogeneity. Furthermore, the influence of Cu is more pronounced in presence of C.

  • 3.
    Nabeel, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Glaser, Bjoern
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Characterization of Dust Generated during Mechanical Wear of Partially Reduced Iron Ore Pellets2017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 88, no 9, article id UNSP 1600442Article in journal (Refereed)
    Abstract [en]

    During reduction in a blast furnace (BF), the iron ore pellets undergo structural changes, which facilitate dust generation due to the mechanical wear/disintegration of the pellets. The generated dust decreases the permeability and productivity of the BF process. Thus, this study investigates the mechanical wear of iron ore pellets reduced at 500 degrees C (P500) and 850 degrees C (P850) and compares the results to the wear of unreduced pellets (P25). Moreover, the dust generated during the wear experiments is also characterized. It is found that pellets reduced at 500 degrees C exhibit a approximate to 16-35% higher wear rate than reference unreduced pellets. For the pellets reduced at 850 degrees C, the mechanical wear is inhibited by a formation of a metallic layer at the outer surface of the pellets. Further, the dust generated due to mechanical wear of reduced pellets contain 3-6 times higher amount of coarse particles (>20m) as compared to the dust from unreduced pellets. The obtained results are explained on the basis of the structural changes, which take place during the reduction of pellets.

  • 4.
    Nabeel, Muhammad
    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.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Evaluation of Dust Generation during Mechanical Wear of Iron Ore Pellets2016In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, no 6, p. 960-966Article in journal (Refereed)
    Abstract [en]

    Iron ore pellets undergo mechanical wear during handling, transportation and use in a blast furnace. This results in a loss of valuable raw materials and causes environmental problems in form of dust in off-gases from a blast furnace. Thus, this study is focused on the investigation of the mechanical wear of iron ore pellets and the dust formation. The characteristics of industrial pellets (such as size, weight, density and hardness) have been investigated. Moreover, the influence of pellet characteristics on the wear mechanism (sliding/abrasion and impact/collisions wear) and the characteristics of generated dust have been investigated. It was observed that the size of pellets can influence the wear rate under the given experimental conditions. The pellets with larger size (13.5 < d(eq) < 15.0 mm) showed 10-20% higher wear rate as compared to small sized pellets (9.5 < d(eq) < 12.50 mm). SEM studies of the dust generated during wear experiments inferred that larger contribution of impact/collisions in wear of pellets is the reason for the higher wear rate of large size pellets. Further, a relationship between the critical diameter of dust particles, which can be removed with off-gases from the blast furnace, and the velocity of off-gases in top part of blast furnace was developed.

  • 5.
    Nabeel, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Extreme Value Distribution of clusters in REM-alloyed stainless steelsManuscript (preprint) (Other academic)
    Abstract [en]

    An extreme value distribution (EVD) analysis has been applied for three dimensional (3D) investigations of clusters observed in REM alloyed stainless steel samples. The presence of observed unit areas without any clusters has been discussed. It has been shown that an increase of the observed unit area (AO) significantly improves the correlation of EVD regression lines. Moreover, three different size parameters were considered for EVD analysis. The results show that using the maximum length of clusters (LC) results in a better correlation of EVD regression lines by improving R2 value up to 0.9876 as compared to 0.9656 – 0.9774 for other size parameters. Moreover, a comparison of predicted and observed maximum lengths of clusters showed that there is need of further work on validation of EVD analysis. 

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  • 6.
    Nabeel, Muhammad
    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.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Friction forces and mechanical dust generation in an iron ore pellet bed subjected to varied applied loadsManuscript (preprint) (Other academic)
    Abstract [en]

    Iron ore pellets degrade and generate dust during transportation and handling as well as during the iron making process. This leads to material losses and effects the process efficiency in a negative manner. In order, to reduce the generation of dust it is important to understand the influence of process parameters on the dust formation. An experimental setup was used to measure the dust generation and friction forces caused by abrasion of iron ore pellets in a closed pack bed. A varied load of 1 to 3 kg was applied on the pellet bed but at a constant air flow rate to capture the airborne dust particles. It was observed that an increase of ~67% is observed in the friction and the dust generation in the bed as the applied load increased from 1 to 3 kg. Moreover, the evaluation of the particle size distribution of the generated dust showed that a higher friction in the pellet bed can lead to an increased amount of airborne particles. Moreover, it has been shown that in an air flow the morphology and the orientation of dust particles can influence the air velocity required to transport the particles upwards.   

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  • 7.
    Nabeel, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Friction Forces and Mechanical Dust Generation in an Iron Ore Pellet Bed Subjected to Varied Applied Loads2017In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 57, no 4, p. 656-664Article in journal (Refereed)
    Abstract [en]

    Iron ore pellets degrade and generate dust during transportation and handling as well as during the iron making process. This leads to material losses and effects the process efficiency in a negative manner. In order, to reduce the generation of dust it is important to understand the influence of process parameters on the dust formation. An experimental setup was used to measure the dust generation and friction forces caused by abrasion of iron ore pellets in a closed pack bed. A varied load of 1 to 3 kg was applied on the pellet bed but at a constant air flow rate to capture the airborne dust particles. It was observed that an increase of similar to 67% is observed in the friction and the dust generation in the bed as the applied load increased from 1 to 3 kg. Moreover, the evaluation of the particle size distribution of the generated dust showed that a higher friction in the pellet bed can lead to an increased amount of airborne particles. Moreover, it has been shown that in an air flow the morphology and the orientation of dust particles can influence the air velocity required to transport the particles upwards.

  • 8.
    Nabeel, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Glaser, Bjoern
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Characterization of dust generated during mechanical wear of partially reduced iron ore pelletsManuscript (preprint) (Other academic)
    Abstract [en]

    During reduction in a blast furnace (BF), the iron ore pellets undergo structural changes which facilitate dust generation due to the mechanical wear / disintegration of the pellets. The generated dust decreases the permeability and productivity of the BF process. Thus, this study investigates the mechanical wear of iron ore pellets reduced at 500 °C (P500) and 850 °C (P850) and compares the results to the wear of unreduced pellets (P25). Moreover, the dust generated during the wear experiments is also characterized. It was found that pellets reduced at 500 °C exhibit a ~ 16 to 35% higher wear rate than reference unreduced pellets. For the pellets reduced at 850 °C, the mechanical wear is inhibited by a formation of a metallic layer at the outer surface of the pellets. Further, the dust generated due to mechanical wear of reduced pellets contained 3 to 6 times higher amount of coarse particles (>20µm) as compared to the dust from unreduced pellets. The obtained results are explained on the basis of the structural changes which take place during the reduction of pellets. 

  • 9.
    Nabeel, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM).
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Formation and Growth Mechanism of Clusters in Liquid REM-alloyed Stainless Steels2015In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 55, no 11, p. 2358-2364Article in journal (Refereed)
    Abstract [en]

    REM-oxide clusters extracted from 253MA stainless steel grade samples from a pilot trial were investigated using a 2%TEA electrolyte. The samples were taken from liquid steel at different holding times after an addition of an appropriate amount of mischmetal. Thereafter, SEM in combination with EDS was deployed for three dimensional (3D) investigations of the characteristics of the extracted REM-oxide clusters. A reliable cluster size distribution (CSD) was obtained by improving the observation method and it was used to explicate the formation and growth mechanism of REM-oxide clusters. A correlation between morphology of clusters and their growth rate was found. This was used to divide the clusters into two different groups, which form and grow in accordance to different mechanisms. The results also show that the growth of clusters is governed by different types of collisions dependent up on size of the clusters. It has been concluded that for REM-oxide clusters turbulent collisions are the main controlling mode for the growth rate.

1 - 9 of 9
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