关键词: 1 000 MPa级高强钢, 焊接接头, 力学性能, 热输入, 显微组织

Abstract: 1 000 MPa high-strength steel plate(thermo mechanical control process(TMCP) steel) for construction machinery is welded by metal active gas(MAG) welding method with GHS90 welding wire as filler material under three heat inputs, and effects of heat input on microstructure and properties of the weld joint are investigated by means of optical microscopy, scanning electron microscopy and transmission electron microscopy. The results show that the microstructure of weld metal consist prodominantly of lath martensite and lath bainite, a small amount of granular bainite and a few retained austenite for three kinds of heat input. The microstructure of the coarse grained heat affected zone(CGHAZ) consists of lath martensite, lath bainite, a small amount of granular bainite. When the heat input is increased, the lath of martensite and bainite is coarsened, the amount of martensite decreases graduslly, while the munber of granular bainite increases, and topographies of retained austenite is changed from thin film to block. With the increased of heat input, the low temperature impact toughness and the hardness of weld metal is reduced gradually, but the impact toughness of heat affect zone initially increases and then decreases. When the heat input is 15 kJ/cm, the welded joints with the combination of high strength and good toughness could be achieved.

Key words: 1 000 MPa grade high strength steel, heat input, mechanical properties, microstructure, welded joints