The study of desulfurization kinetics in grain oriented 3 percent silicon iron
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I.
INTRODUCTION
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Goss texture in grain oriented 3 pct Si-Fe is developed through a process called secondary recrystallization. The primary metallurgical reason causing secondary recrystallization has been attributed to the retardation of normal grain growth due to the inhibition force exerted by second phase particles and/or solute atoms. Manganese sulfide particles have been used extensively in conventional grain oriented 3 pct Si-Fe as the primary inhibition system. If the materials are not properly annealed, these MnS particles can be destabilized during the early stage of secondary recrystallization by desulfurization or particle coarsening, resulting in poor texture development. Once the Goss texture is developed, sulfur has to be removed from the strip to avoid the detrimental effect3 of sulfur on the core loss of the final product. For the above reasons, it is important to know the desulfurization kinetics during the final texture annealing in grain oriented 3 pct Si-Fe.
T.H. SHEN is Research Specialist with Allegheny Ludlum Steel Company, Research Center, Alabama and Pacific Avenues, Brackenridge, PA 15014. This paper is based on a presentation made at the symposium "Physical Metallurgy of Electrical Steels" held at the 1985 annual AIME meeting in New York on February 24-28, 1985, under the auspices of the TMS Ferrous Metallurgy Committee. METALLURGICALTRANSACTIONS A
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A . Desulfurization M o d e l
The sulfur in conventional grain oriented 3 pct Si-Fe is present as sulfide particles, such as MnS, which precipitate during the hot rolling. To remove sulfur from the material, the sulfide particles have to be dissolved into the matrix to allow sulfur to diffuse subsequently to the surface of the material. Benford3 first suggested the concept of the existence of a moving interface during the desulfurization process. Swift et al.~ further elaborated the idea by assuming desulfurization to be a two-stage process. As shown in Figure 1, the first stage of desulfurization contains two interfaces moving from two surfaces toward the center of the sheet sample. The sulfide particles dissolve in the outer region and sulfur diffuses through the concentration gradient to the surface. The inner region, which is bound by the two moving interfaces, is assumed to be a two phase region containing matrix and sulfide particles. The sulfide particles
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may coarsen and reduce the inhibition, but the sulfur concentration in this inner region remains unchanged. The desulfurization process is governed by Fick's second law. The init
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