Effect of Posttreatment on Microstructure and Magnetic Properties of Si Steel Strips Prepared by Twin-Roll Continuous Ca
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I.
INTRODUCTION
AS a sort of near-net-shape technology, twin-roller continuous casting (TRCC) presents numerous advantages on the economical production of thin strips, such as low energy consumption, low equipment and operating costs, and rapid solidification. Furthermore, excellent properties of strips may be obtained due to the finer grain size, and little microsegregation on microstructure resulted from the rapid solidification process.[1–8] Si-steel, which is a soft magnetic material, has drawn considerable attention in current industry applications. However, the preparation of Si-steel strips is complicated and difficult because of its high demand using conventional methods such as the casting-rolling process. For a comparison, TRCC characterizes a cost effective and easily controllable manufacturing process on Si-steel preparation. Thus, producing Si-steel strips using TRCC technology has become both attractive and popular.[9–11] In our early works,[12] a series of Si steel strips with different Si content from 0.5 wt pct to 6.5 wt pct Si was successfully prepared by the TRCC process. According to the documents, a high Si content is necessary to improve the magnetic properties of Si steel. Unfortunately, our early works indicated that posttreatment was YU YI and SHAOQUN JIANG, Lecturers, and ZEHUA WANG, Professor, are with the College of Mechanics and Materials, Hohai University, Nanjing 210098, P.R. China. ZEHUA ZHOU, formerly Visiting Scholar, Department of Mechanical Engineering Technology, Purdue University, West Lafayette, IN 47906, is now Associate Professor, College of Mechanics and Materials, Hohai University. Contact e-mail: [email protected] WEIDONG HUANG, Professor, is with the State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, P.R. China. Manuscript submitted August 22, 2011. Article published online June 23, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS B
difficult to meet production demands and microcracks became inevitable for Si-steel strips by TRCC if the Si content was 4.5 wt pct or more. Thus, in this article, we focus on Si-steel strips with 3.0 wt pct Si content prepared by TRCC. Based on early works, the optimum parameters of the posttreatment were ascertained. Furthermore, the microstructure and magnetic properties of the strips before and after posttreatment were investigated and discussed. It is emphasized in this article that a sort of ordered-phase Fe3Si occurred after posttreatment, which might act as an important role on improving the magnetic properties of Si steel strips.
II.
EXPERIMENTAL PROCEDURE
For this process, 3.0 wt pct Si-steel was smelted in a medium-frequency induction furnace. The main other elements of the steel are as follows: C content is less than 0.05 wt pct, and Mn, P, and S contents are all less than 0.02 wt pct. The casting test was completed in an SLB-1 test continuous-casting mechanism. The pouring temperature was 1833 K (1560 C) and the main parameters of the mechanism were as follows: The diameter a
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