Q345B厚钢板对接接头显微组织分析及力学性能测试

Microstructure and mechanical properties of butt joints of thick Q345B steel plate

为评价Q345B厚钢板焊接接头的力学性能,使用MAG焊和埋弧焊工艺对67 mm厚的试板进行焊接,并对焊接接头各区域进行金相组织分析及力学性能测试,包含拉伸、弯曲、常温冲击和低温冲击测试。结果表明,焊接工艺得到的焊接接头成形良好,缺陷较少,其中埋弧焊焊缝呈现粗大的柱状晶,为先共析铁素体和针状铁素体,MAG焊焊缝为先共析铁素体和针状珠光体,埋弧焊层间组织晶粒较均匀,为片状珠光体及铁素体;焊接接头屈服强度平均值为349 MPa,抗拉强度平均值为440 MPa,断后伸长率平均为29.3%;弯曲角90°时,不同位置的弯曲试样均未出现裂纹;除存在气孔的试样外,常温冲击吸收功大于100 J,低温冲击吸收能量大于65 J。总体来看,该工艺得到的焊接接头力学性能良好,能够满足技术要求。

In order to evaluate the mechanical properties of welded joint of thick Q345 B steel plate,67 mm thick plates was welded using MAG welding and submerged arc welding process,respectively,and the microstructure and mechanical properties of the welded joints were tested including tensile,bending,room temperature impact and low temperature impact test. The results show that the welded joint obtained in the welding process has good appearance and the defects are few,and the microstructure of SAW weld is coarse columnar grains of the first eutectoid ferrite and acicular ferrite. MAG weld is composed of first eutectoid ferrite and acicular pearlite,and microstructure of SAW weld interlayer is more uniform,consisting the lamellar pearlite and ferrite. The average yield strength and tensile strength of the welded joint are 349 MPa and 440 MPa,respectively,the average elongation is 29. 3%. The bending specimens at different positions are not cracked at the bending angle of 90°. In addition to the samples containing pores,the impact absorption energy at room temperature is higher than 100 J,and it is higher than 65 J at low temperature. In general,the joints have good mechanical properties and meet the technical requirements.