Q355B厚板表面结疤缺陷分析

Analysis of Surface Scarring Defects on Q355B Thick Plate

摘要: 通过金相分析，确定50 mm以上厚度Q355B钢板表面结疤缺陷出现于精轧环节，结合相关机理，确认是对应的400 mm铸坯从分切到热送装入加热炉的时间平均仅为7.4 h，入炉温度普遍高于550℃，处于热装裂纹敏感区，通过延长热送总时间至18 h以上，铸坯入炉温度降至450℃以上，Q355B表面结疤缺陷发生率从10%左右降至0.2%以下。

Abstract: Through metallographic analysis, it was determined that the surface scarring defects on Q355B steel plates with a thickness of over 50mm occurred during the finishing rolling process. Combined with relevant mechanisms, it was confirmed that the corresponding 400 mm cast billets had an average time of only 7.4 hours from cutting to hot delivery and loading into the heating furnace, with the temperature upon entering the furnace generally being higher than 550˚C, which is in the hot charging crack sensitivity zone. By extending the total hot delivery time to over 18 hours, the temperature of the cast billets upon entering the furnace was reduced to above 450˚C, and the occurrence rate of surface scarring defects on Q355B decreased from around 10% to below 0.2%.