690 MPa grade high strength low alloy(HSLA)steel of 27 mm in thickness was welded by self-developed electrode of 4.0 mm in diameter without preheating.The effects of heat input on microstructure and mechanical properties of weld metal were studied and the mechanism of strength-toughness was revealed.The results show that heat input had significant effect on microstructure and mechanical properties of weld metal,which increased from 13 kJ/cm to 19 kJ/cm.With the increasing of heat input,tensile strength and hardness of butt joint decreased,-50 ℃ impact energy firstly increased and then decreased.Good strength-toughness was obtained under the heat input condition of 16 kJ/cm.The tensile strength of butt joint was 828 MPa,-50 ℃ impact energy of weld metal was 71～90 J,the average value was 80 J.The lower strength-toughness properties of weld metal under 13 kJ/cm and 19 kJ/cm heat input conditions were related with the formation of lath bainite and ferrite side plates,the formation of coarse M-A,respectively.Under the 16 kJ/cm heat input condition,good plasticity acicular ferrite was sufficiently formed and acicular ferrite and bainite were distributed in an interwoven pattern.Meanwhile,small and dispersively distributed M-A had no obviously negative effect on toughness of weld metal.Therefore,weld metal with excellent strength-toughness had been obtained.
关键词
690/MPa级HSLA钢/焊接热输入/焊缝金属/强韧化机理
Key words
690 MPa grade HSLA steel/heat input/weld metal/mechanism of strength-toughness properties
维普
万方数据