高强韧特厚桥梁钢板焊接热影响区的组织与性能

Microstructure and properties of heat affected zone in high strength and toughness heavy plate for bridge

采用Gleeble 3800试验机模拟60 mm特厚高强韧桥梁钢板热影响粗晶区(CGHAZ)的焊接热循环,通过金相分析、硬度测试和示波冲击试验研究了焊接热输入量E、二次峰值温度TP2对CGHAZ显微组织与性能的影响。结果表明,单道次焊接热模拟工艺条件下,随着焊接热输入量的增大,一次粗晶区(CGHAZ)组织由细板条贝氏体(LB)逐渐转变成粒状贝氏体(GB),而冲击吸收能量和显微硬度值随着焊接热输入量的增大而减小;焊接热输入量不大于50 k J/cm时,试验钢板具有较好的冲击性能,M-A组元粗化,冲击性能下降。在双道次焊接热模拟工艺条件下,E=30 k J/cm时,冲击吸收能量随着TP2的增大呈现出先上升后下降的趋势;TP2=750℃时,冲击性能最差,表现出临界粗晶热影响区脆化。

Thermal cycles of welding in coarse grain heat affected zone ( CGHAZ) of high strength and toughness heavy plate for bridge were simulated using a Gleeble 3800 simulator. Effects of heat input ( E) and second peak temperature ( TP2 ) on microstructure and properties of the CGHAZ were studied by means of metallographic analysis, hardness test and oscillography impact test. The results show that the microstructure of the coarse grain heat affected zone( CGHAZ) changes from fine lath-like bainite( LB) to granular bainite( GB) , while the microhardness and the impact absorbed energy reduce as the heat input increases under single pass welding condition. The tested steel plate has good impact property when the heat input is lower than 50 kJ/cm, and as the M-A constituent coarsening, the impact properties getting worse. The impact absorbed energy showing a downward trend after the first rise with the second top temperature ( TP2 ) increase under double pass welding condition. When the second peak temperature is 750℃, the tested steel plate gets worst impact absorbed energy and the critical coarse grain heat affected zone tends to be brittle.