960 MPa级高强钢焊接热影响区连续冷却曲线的测定及焊接工艺评定

Determination of simulated SHCCT curves and welding procedure qualification of 960 MPa grade high strength steel

采用Gleeble-3800热模拟试验机进行模拟,并结合组织转变特征和显微硬度变化,测得了该钢的连续冷却转变曲线,并通过富氩气体保护焊焊接工艺,对该钢种进行了斜Y坡口焊接冷裂纹敏感性试验及焊接工艺评定。结果表明,该钢在热影响区存在如下类型的组织转变: t 8/5 <30 s的马氏体转变;60 s< t 8/5 <100 s的马氏体和贝氏体的混合转变;150 s< t 8/5 <600 s的贝氏体转变;t 8/5 >1 000 s的先共析铁素体、珠光体和贝氏体混合转变。在焊接过程中,960 MPa级高强钢焊接热影响区不存在软化现象,随着热输入、 t 8/5 减小,抗拉强度降低,HAZ韧性增加。在同一 t 8/5 水平下,板厚对抗拉强度、HAZ冲击吸收能量影响不大。对于8~15 mm厚的960 MPa级高强钢钢板采用70 kg级焊丝CHW-70C,OK13.29预热不低于80 ℃,采用90 kg级焊丝GM120预热温度不低于100 ℃,无冷裂纹产生。

The continuous cooling transition curve of 960 MPa grade high strength steel was measured by Gleeble-3800 thermal simulation test machine combined with the structural transformation characteristics and microhardness changes. And Y-groove welding cold crack sensitivity test and welding procedure qualification of the steel were carried out by the argon-rich gas shielded welding procedure. The results show that microstructure transformation of the steel in heat affected zone is as follows, martensite transformation of t 8/5 <30 s, mixed transformation of martensite and bainite of 60 s< t 8/5 <100 s, bainite transformation of 150 s< t 8/5 <600 s, pre-eutectoid ferrite, pearlite and bainite mixed transformation of t 8/5 >1 000 s. In the welding process, there is no softening phenomenon in the welded joint of 960MPa grade high strength steel. As the heat input decreases, t 8/5 decreases, the tensile strength decreases, and the HAZ toughness increases. At the same t 8/5 level, the plate thickness has little effect on tensile strength and HAZ impact energy. For the 960 MPa grade high-strength steel plate with 8~15 mm thickness, preheating temperature is not lower than 80 ℃ when using 70 kg grade welding wire CHW-70C, OK13.29, and preheating temperature is not lower than 100 ℃ when using 90 kg grade welding wire GM120, no cold crack is generated under the above conditions.