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| Effect of superheat on macrosegregation of GCr15SiMn bearing steel ingot during solidification |
| ZHANG Tao, CHENG Guo-guang, HOU Yu-yang |
| State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China |
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Abstract Some solidification defects such as macrosegregation will occur during the solidification of GCr15SiMn steel ingots. The effect of superheat on the macrosegregation of GCr15SiMn ingot was analyzed. GCr15SiMn ingots of 1 kg were smelted by vacuum induction furnace. The solidification structure and macrosegregation of the steel ingot were obtained by acid erosion and OPA, respectively. The flow rule of molten steel was studied by ProCAST software. The results showed that at high superheat (70 ℃), a certain degree of negative segregation appeared in the lower part of the center, and serious positive segregation formed in the upper part of the center with porosity. The porosity range was smaller and the carbon distribution was more uniform at moderate superheat (50 ℃). In the case of low superheat (20 ℃) and extra-low superheat (-20 ℃), the porosity range was enlarged. Moreover, severe negative segregation was formed at the initial stage of solidification and severe positive segregation was formed at the end of solidification. The mechanism of superheat affecting segregation was that the heat convection was strong during solidification and solute floated upward at high superheat, causing serious positive segregation in the upper part of steel ingot. When the superheat was extra-low, a large number of crystals nucleated and remained at the bottom of the steel ingot in the early stage of solidification, and serious negative segregation formed at the bottom.
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Received: 27 May 2020
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2020, Vol. 30 
