1. Products & Technique Management Department, Wuhan Iron & Steel Co., Ltd., Wuhan 430080, China;
2. Central Research Institute, Baoshan Iron & Steel Co., Ltd., Wuhan 430080, China
Abstract： The longitudinal and transverse coil diameter difference of ultrafine bainite 30MnTiB steel coil is too large after hot continuous rolling, resulting in many waste products. In order to solve this problem, four different cooling processes were designed. The microstructure, expansion amount and high temperature strength were measured by optical microscope (OM), thermal simulation test machine and high temperature tensile test machine. By combining with the degree of longitudinal and transverse coil diameter difference of 30MnTiB steel coil under four different cooling processes, the mechanism to cause diameter out of tolerance of 30MnTiB steel coil was analyzed. The results showed that the expansion of bainite transformation obtained after cooling was larger than that of pearlite and martensite transformation. The lower the transformation temperature, the greater the expansion, and the more serious the vertical and horizontal coil diameter deviation. During the cooling of steel coil in the range of bainite transition temperature, if the lower cooling rate was adopted for 30 m coil at beginning at lower temperature to increase the strength of inner ring, and then the higher cooling rate was used to reduce the expansion force of the coil, the problem of coil oval deformation of bainite 30MnTiB steel could be effectively solved.
2022, Vol. 40 
