Optimization of traveling magnetic field for horizontal continuous casting of thin slab containing tin phosphor bronze
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Tingju Li School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China (Received 19 January 2017; accepted 26 May 2017)
To improve the quality of horizontal continuous casting bronze thin slab, especially the end quality of the thin slab, three methods were proposed; (i) using silicon steel sheet at the ends of the traveling magnetic field (TMF), (ii) change in the length of TMF, and (iii) reduction in the ends current intensity of TMF. Then, the effect of these methods on the magnetic field, flow and solidification of thin slab was studied both numerically and experimentally. Results show that the use of silicon steel sheet is the best method to modify the magnetic field intensity distribution. Due to the electromagnetic field shielding effect of silicon steel sheet, when the silicon steel sheet with 150 mm length and 0.5 mm thickness was applied, the magnetic field intensity at the ends of TMF was reduced to about half of the original. However, the magnetic field intensity in the middle of TMF did not change, which assists the elimination of the strong flow of the melt at the ends of the mold and uniform the solidification shell of the melt. Then, the bronze thin slab can be successfully cast without any crack defects at the ends.
I. INTRODUCTION
Horizontal continuous casting of thin copper slab is an important production process for copper strips, which has the advantages of short steps, low production costs, and small footprint equipment. It is especially used for the production of hot-rolled tin phosphor bronze alloys.1,2 However, during the horizontal continuous casting process, the temperature gradient and cooling speed of a slab are found to be high, which cause segregation, center porosity, inclusions, and other defects. These defects exposed at subsequent processing seriously affect strip quality.3 Previous studies have shown that the flow of molten metal in a mold has a significant impact on the quality of the slab.4–7 Therefore, the traveling magnetic field (TMF) is used during horizontal continuous casting of thin tin phosphor bronze slab with dimensions of 16 655 mm. The schematic diagram of the casting is shown in Fig. 1(a). Some studies have shown that applying TMF during horizontal continuous casting of thin copper slab can improve the flow pattern and flow velocity of molten metal in the mold, as it significantly refined the grain structure and reduced the segregation and shrinkage defects of tin phosphor bronze slabs.8–11 However, during the course of industrial tests, it is found that there is strong melt circulation at the mold ends when the TMF Contributing Editor: Michael E. McHenry a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.241
is applied as the flow intensity in thin slab is too large. This will affect the solidification process of the molten metal at the mold ends and cause crack defects at the thin slab ends.12,13 Various previous studies have been focused on improving the quality of these slabs.14,15 In
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