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

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:t8/5＜30 s的马氏体转变;60 s＜t8/5＜100 s的马氏体和贝氏体的混合转变;150 s＜t8/5＜600 s的贝氏体转变;t8/5＞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、t8/5减小，抗拉强度降低，HAZ韧性增加。在同一t8/5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。

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

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.