Mechanical Analysis of Plastic Deformation and Research on Edge Crack in Vertical Rolling Process
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摘要: 钢坯边缘开裂是轧制工艺中的一个重要难题。本文建立了一种在立轧阶段对钢坯边缘裂纹扩展与闭合进行判断的能量分析模型，根据所提出的Γ-三次曲线函数狗骨模型，推导了对应的塑性流动速度场、应变速率场以及包含裂纹尺寸参数的总功率泛函表达式。基于功率最小化原理，数值求解了狗骨变形参数和轧制力，实现了对临界开裂点的计算。结合具体算例对所建立的计算方法进行了验证，并进一步研究了裂纹尺寸对立轧工艺参数和钢坯力学性能的影响。结果表明，开裂与钢坯边缘的变形程度有关，在一定压下量的前提下，增大立辊半径可以起到抑制边缘开裂、提高裂纹闭合率的作用。Abstract: The cracks appear on slab edge which is a significant quality problem faced in rolling process. In this paper, an energy analysis model for judging the growth and closure of edge crack in vertical rolling process is established. According to the proposed Γ-cubic function dog-bone model, the corresponding expressions of plastic flow velocity field, strain rate field, as well as total power functional with crack size parameters are derived. The calculation of critical crack point is achieved after dog-bone deformation parameters and rolling force are solved numerically by using the principle of minimum energy. Then, the established calculation method is verified by specific examples. Furthermore, the effects of crack size on rolling parameters and mechanical properties are studied. The results show that the growth of crack is related to the deformation degree of the slab edge. For the premise of width reduction requirement, increasing the radius of vertical rollers is advantage to control the edge crack and improve the crack closure rate. The research and analysis of this paper can be helpful for the promise of product quality and the optimization of rolling process.
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Key words:
- vertical rolling /
- edge crack /
- energy model /
- critical crack parameter
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图 6 立轧过程能量模型的计算流程图
Figure 6. Calculation flow chart of energy model in vertical rolling process
图 7 裂纹能量模型与Yun模型的轧制力预测对比
Figure 7. Comparison of rolling force calculated by crack energy model and Yun’s model
图 8 摩擦因子对轧后裂纹开口宽度的影响
Figure 8. Effects of friction factor on crack width after rolling
图 9 裂纹尺寸对（a）狗骨骨峰位置和（b）轧制力的影响
Figure 9. Effects of crack shape on (a) position of dog-bone peak and (b) rolling force
Process parameters as follows: No. 1：w0=0.735 m，∆w=0.038 m，h0=0.12 m，R=0.55 m，m=0.3； No. 2：w0=0.78 m，∆w=0.035 m，h0=0.11 m，R=0.475 m，m=0.3
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