Q355B钢板火切后窄板料变形原因分析及控制措施

Cause analysis and control measures of narrow strip deformation of Q355B plate after flame cutting

针对Q355B钢板火焰切割(火切)后窄板料产生翘曲、侧弯等变形缺陷的问题,检测了Q355B钢板残余应力。结果表明:Q355B钢板火切后窄板料变形是成品钢板中存在较大残余应力和残余应力不均匀而导致的。因此,对不同轧制、冷却工艺生产的Q355B钢板的残余应力进行了检测,发现返红温度低是钢板残余应力显著增大、残余应力波动较大的主要原因。为此,提出了采用控轧不控冷工艺,控制钢板终轧温度在780~810℃,在确保钢板性能的前提下,避免了钢板因控冷产生较大的残余应力及残余应力波动。同时,针对采用不控冷工艺生产的Q355B钢板屈服强度不足或余量不够的问题,对Q355B钢板的C、Mn含量进行优化调整。采用上述措施后,保证了钢板力学性能,并将钢板残余应力控制在150 MPa以下,整板最大残余应力波动由182.3 MPa降至26.45 MPa,使钢板的不平度小于2 mm·m^(-1),满足了用户的要求。

The residual stress of Q355 B plate was detected to solve the problem of warping and side bending of narrow strip after the plate flame cutting.The results show that the deformation of narrow strip after Q355 B plate flame cutting is caused by large residual stress and uneven residual stress in finishing plate. Therefore, the residual stress of Q355 B plate produced by different rolling and cooling processes was detected, and it was found that the low self-tempering temperature was the main reason for the significant increase of residual stress and the large fluctuation of residual stress of the plate.Therefore, the process of controlled rolling without controlled cooling was proposed to control the finishing rolling temperature of the plate in the range of 780-810 ℃. On the premise of ensuring the performance of the plate, the large residual stress and residual stress fluctuation caused by controlled cooling were avoided.At the same time, aiming at the problem of insufficient yield strength or allowance of Q355 B plate produced by uncontrolled cooling process, the content of C and Mn of Q355 B plate was optimized and adjusted.After adopting the above measures, the mechanical properties of the plate were guaranteed, and the residual stress of the plate was controlled below 150 MPa. The fluctuation of the maximum residual stress of the whole plate was reduced from 182.3 MPa to 26.45 MPa, and the roughness of the plate was less than 2 mm·m^(-1), which meets the requirements of users.