Effect of gradient temperature rolling process on promoting crack healing in Q500 heavy plates

Zhao-hai Gao^1,2，Wei Yu²，Xu Chen¹，Bao-sheng Xie³，Qing-wu Cai¹

1. Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing2. National Engineering Research Center of Advanced Rolling, University of Science and Technology Beijing3. Hunan Valin Rolling Steel Sheet Co.Ltd

摘 要：To ensure the quality of heavy plate products as determined by ultrasonic inspection, it is necessary to effectively control defects such as cracks and shrinkage cavities in heavy plates. Generally, some defects such as large size cracks exist due to insufficient deformation in the center of traditionally rolled plates. Compared with the traditional rolling process, gradient temperature rolling(GTR) process can effectively increase deformation inside heavy plates. In this study, the effect of GTR on crack healing was analyzed through a comparison experiment with the uniform temperature rolling(UTR). The results show that the GTR process could increase the plastic strain inside the heavy plate and effectively promote the healing process of the preset cracks. The degrees of crack healing at the center and quarter thickness position of the steel plate via GTR were greater than twice those of the plate via UTR. The GTR process can significantly reduce the internal defects of heavy plates and improve the defect detection level of heavy plate products. Also, The GTR process results in the formation of new crystal grains in the crack region, which is crucial to crack healing.

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