500MPa级S500QL调质高强钢板在线直接淬火(DQ)工艺研究及应用

Research and application of on Line Direct-Quenching(DQ)Process for 500 MPa S500QL High Strength Quenching and Tempering Steel Plate

开发了低碳(C≤0.12%)Nb-V微合金化S500QL高强度钢板,使用120 t BOF+LF+VD的洁净钢冶炼工艺,采用两阶段控制轧制(第一阶段950~1070℃区间轧制,第二阶段开轧≤890℃、终轧≤850℃)及轧后以7~20℃/s的冷速在线直接淬火(DQ),经620~670℃,3min/(mm·T)回火生产了15~50 mm钢板。钢板组织为细化的粒状贝氏体+少量先共析铁素体,屈强比≤0.90、延伸率A≥19%,-50℃下冲击功≥100 J,满足市场需求。对DQ工艺钢板进行焊接裂纹敏感性试验及焊接接头性能检验,结果显示,采用该工艺生产的钢板具有良好的焊接性能。

Low carbon(C≤.12%)Nb-V microalloying S500 QL high strength steel plate has been developed.And15~50 mm steel plate are produced by two-stage controlled rolling(first stage rolling at 950~1070℃,second stage starting rolling at≤890℃and finishing rolling at≤850℃),on-line cooling direct-qenching(DQ)with 7~20℃/s after rolling,and tempering at 620~670℃for 3 min/(mm·T),clean steel smelting process with 120 t BOF+LF+VD.The steel plate has fine granular bainite+small amount of proeutectoid ferrite with yield-tensile strength ratio≤50.90,elongation A≥19%and impact energy at-50℃≥100 J to meet the market demand.And the welding crack sensitivity test and the welding joint property test of DQ process steel plate was carried out.The results show that the steel plate produced by this process has good welding property.