微合金EH40型船板钢大热输入焊接接头组织和力学性能

Microstructures and mechanical properties of joints of microalloyed EH40 ship steel plate with high heat-input welding

通过拉伸、冲击、硬度力学试验和接头微观组织分析,对EH40船板钢大热输入埋弧焊的焊接性和接头性能进行了试验分析。结果表明,以热输入为40kJ/cm和60kJ/cm焊接,焊接热影响区粗晶区冲击吸收功值均最低,分别为116J和80.5J;焊接接头的强度均高于母材,焊接热影响区均未出现焊接软化区。当焊接热输入为40kJ/cm时,粗晶区组织主要为板条贝氏体、粒状贝氏体、少量的块状铁素体,而焊接热输入为60kJ/cm时,板条贝氏体明显减少,块状铁素体增多,并出现少量针状铁素体。Ti,Nb合金元素的碳氮化合物第二相粒子,在大焊接热输入时,很大程度上阻止粗晶区奥氏体晶粒的长大,改善了该区域的冲击性能。

The weldability of EH40 ship steel plate by submerged-arc welding with high heat-input was studied by the tensile test, impact test, hardness test and microstructure. Experiment results show that the impact absorbing energy value were 116 J and 80.5 J in the coarse grain zones with the high heat-input 40 kJ/cm and 60 kJ/cm. The strength of the welded joint was better than the one of the base metal and there wasn't soft zone in HAZ. The main macrostructures were lath bainite, granular bainite and a few block-like ferrite in the coarse grain heat affected zone with 40 kJ/cm, while less lath bainite and more block-like ferrite and a few acicular ferrite appear in the some zone with 60 kJ/cm. The toughness in the coarse grain heat affected zone is improved for the existing carbides and nitrides of Ti and Nb, which prohibit the original austenite grain from coarsening in high heat-input.