Thermodynamic Simulations and Industrial Trials Applied to Inclusion Control of SAE 9254 Si-Mn Killed Steel
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DUCTION
STEEL cleanliness requires a precise control of amount, composition, shape, and size distribution of inclusions[1] Suito and Inoue[2] studied the relationship among steel, inclusion, and slag compositions at 1550 °C in regard of steels destined to the manufacture of steel cord and springs. According to Yang et al.,[3] inclusion control requires also precise control of oxygen, aluminum, and sulfur contents.
ERMANI VINICIUS DE OLIVEIRA LIMA, GUSTAVO HENRIQUE SOUSA, and JOAQUIM GONC¸ALVES COSTA NETO are with the Department of Product Engineering, ArcelorMittal Brasil, 35930-900 Joa˜o Monlevade, MG, Brazil. JOHNE JESUS MOL PEIXOTO and CARLOS ANTONIO DA SILVA are with the Department of Metallurgical Engineering and Materials, Federal University of Ouro Preto, Morro do Cruzeiro, 35400-000 Ouro Preto, MG, Brazil. Contact e-mail: [email protected] Manuscript submitted on March 07, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS B
According to Zhang et al.[4] the slag influence on steel cleanliness can be evaluated following the total oxygen steel content. Yang et al.[5] investigated the optimum CaO-SiO2-Al2O3-MgO slag composition in order to achieve inclusions amenable to spring manufacture from Si-Mn killed steel. According to Kang et al.,[6] the oxide inclusion composition should remain in the low melting point region for Si-Mn killed steels if deformability is to be achieved during hot rolling. Following Atkinson et al.,[7] oxides inclusions are fragile and more detrimental to steel resistance to cyclic mechanical stresses than manganese sulfide inclusions. Resistance to fatigue also increases when the inclusion average size decreases. Inclusions may be transformed and or removed by proper contact with a slag. Inclusions and slag are no different under equilibrium conditions, Kang et al.[6] Accordingly, Costa e Silva[8] present a general concept of Inclusion Engineering. Yang et al.[5] states that slag–steel interaction can be used to control inclusion plasticity; likewise, Mandal et al.,[9] state that inclusion features can be modified by treatment with synthetic slags.
Fig. 1—Production flowsheet for SAE 9254 steel, showing the metal and slag sampling scheme.
Table I. Summary of Slag Composition Slag Composition Base Scenario New Condition
average range average range
CaO
SiO2
MgO
Al2O3
FeO+MnO
CaO/SiO2
24.28 20 to 30 39.7 20 to 30
47.85 40 to 50 39.067 40 to 50
15.58 15 to 20 15.867 15 to 18
3.18 max. 4.0 1.767 max. 4.0
6 5.0 to 8.0 2.167 1.0 to 3.0
0.52 0.30 to 0.60 1.02 0.90 to 1.10
Fig. 2—Schematic section showing area of ASCAT analysis: (a) Lollipop sample, (b) billet, and (c) steel wire.
Not many work relating industrial processes parameters to inclusion features (ranging from ladle furnace treatment to steel cord) in Si-Mn killed steels are available in the literature. This work deals with the interaction of a SAE 9254 Si-Mn killed steel with slags from the CaO-SiO2-Al2O3-MgO system with binary
basicity ranging from 0.60 to 1.50. Both thermodynamic simulations as well as industrial tr
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