冷却工艺对超细晶贝氏体30MnTiB钢扁卷的影响

为了解决超细晶贝氏体30MnTiB钢热连轧后钢卷纵横向卷径差过大产生扁卷，导致大量废品的问题，设计了4种不同的冷却工艺，采用光学显微镜(OM)、热模拟试验机、高温拉伸试验机，对其显微组织、膨胀量、高温强度进行测量，结合4种不同冷却工艺下30MnTiB钢卷纵横向卷径超差的程度，分析了30MnTiB钢卷径超差现象产生的机理，结果表明：钢卷冷却后获得贝氏体组织，组织转变膨胀量较珠光体和马氏体转变大，转变温度越低，膨胀量越大，钢卷发生纵横向卷径超差越严重。钢卷在贝氏体转变温度区间内冷却时，采用较低冷速使钢卷前30 m在较低温度冷却提高内圈强度，30 m后采用较高温度冷却减小钢卷的膨胀力可有效解决贝氏体30MnTiB钢扁卷问题。

Effect of cooling processes on coil oval deformation of ultrafine bainite 30MnTiB steel

The longitudinal and transverse coil diameter difference of ultra fine 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.