大热输入焊接高强度低合金钢热影响区的晶粒细化

Grain refinement of heat affected zone of high strength low alloy steel by large heat input welding

研究了焊接热输入为110 kJ／cm三丝埋弧自动焊E36高强度低合金钢热影响区的晶粒细化行为；用自动图像分析仪测量了焊接热影响区诱导晶内铁素体形核夹杂物的大小、分布；用透射电镜观察了具有自细化行为晶内铁素体的形貌。结果表明，焊接热输人为110 kJ／cm三丝埋弧自动焊，焊接热输入对热影响区夹杂物的直径大小、分布几乎没有影响。E36高强度低合金钢中加入微量的Ti，能形成直径为0．2～0．8μm的MnO，TiO，SiO2，Al2O3与MnS组成的氧硫复合物。大热输入焊接时，氧硫复合物诱导热影响区的晶内铁素体形核，并促进晶内铁素体的感生形核，晶内铁素体及其感生晶内铁素体使热影响区粗晶区的晶粒细化，确保焊接热影响区粗晶区的强度与韧性不降低。

Refining grain behavior of the heat affected zone (HAZ) of E36 high strength low alloy steel was studied, when E36 steel was welded by three wires submerged arc welding with 110 kJ/cm large heat input. The sizes and distribution of the inclusions in HAZ which promote intra-granular ferrite nucleation were measured using the automatic image analyzer, and the figures of the intra-granular ferrite which has self refining grain behavior were observed using transmission electron microscopes with energy dispersive X-ray spectroscopy. The results indicate that the welding heat input has nearly no effect on the sizes and distribution of the inclusions in the HAZ, when heat input of three wires submerged arc welding is 110kj/cm. E36 high strength low alloy steel with mircoalloy Ti has oxide-sulfide complexes composed of such MnO, TiO, SiO 2, Al 2O 3 and MnS, and their diameter is 0.2-0.8 μm. The reasons of refining grain in the HAZ of E36 steel are that the small oxide-sulfide complexes inclusions induce the nucleation and sympathetic nucleation of intra-granular ferrite in the large heat input welding process, which makes the strength and fracture toughness values of coarse grains zone in the HAZ of E36 steel no decrease.