CO_2保护焊对Q345钢接头组织及性能的影响

Influence of Automatic CO_2 Gas Protection Welding Process Parameters on Microstructure and Performance of Q345 Steel Joint

自动CO_2气体保护焊采用ABB焊接机器人,Q345钢板厚度为12 mm,开V形坡口,进行对接接头平板焊接工艺试验,研究了不同焊接工艺参数对焊接接头组织及性能的影响。结果发现,当送丝速度与焊接速度相匹配时,熔滴过渡方式为短路过渡,焊接飞溅小,焊缝连续性良好;表面无气孔、裂纹、咬边等焊接缺陷。随着送丝速度增大,焊接电流增大,接头有过热、氧化倾向,飞溅大,成形质量较差。接头组织为细小的铁素体﹑珠光体和少量贝氏体;送丝速度过大,导致热输入过大,铁素体呈粗大块状。Q345钢中厚板(厚12 mm)时,最佳焊接工艺参数:焊接电流为160 A,焊接电压为22 V,送丝速度为60 m/h,焊接速度为3~6 mm/s,气流量为18 L/min,接头硬度分布均匀,冲击断口韧窝较多,韧窝较深且分布均匀,表现出较好的韧性。

By using the automatic CO2 gas protection welding with ABB welding robot for 12 mm thick Q345 steel plate with V groove, butt joint welding process testing was carried out to understand effects of different welding process parameters on microstructure and properties of welding joint. The results reveal that with wire feeding speed matching with welding velocity, droplet exhibits short-circuit transi- tion with low spatter, so welding seam with desirable quality can be obtained. Absence of defects, such as gas hole, crack and undercut, can be observed in the surface of the joint. With increasing in feeding wire speed and welding current, the joint has the worse forming quality as a result of over-heating and oxidization tendency of joint leading to high spatter. When wire feeding speed is matched with welding velocity, microstructure of the joint is composed of fine white ferrite and black pearlite as well as a little uniformly distributed bainite. However, ferrite exhibits coarse bulky structure due to high heat-input with increasing in wire feeding speed. The optimized welding parameters for Q345 steel plate with 12 mm in thickness are presented as follows, current of 160 A, voltage of 22 V, feeding wire speed of 60 m/h, welding velocity of 3- 6 mm/s and gas flow of 18 L/rain, where hardness of the joint is distributed uniformly with good ductility.