Submerged arc welding process of Q345B seamless steel pipe

Q345B seamless steel pipe belongs to hot-rolled and normalized steel, and its main structure is ferrite + pearlite. Q345B seamless steel pipe has high hardness and strength, low plasticity and toughness, and has a certain hardening tendency. In the case of large thick plates and excessive cooling speed, cold cracks are prone to occur in welding; Q345B seamless steel pipes are welded with large technology during parametric welding, due to the excessive linear energy, Q345B seamless steel pipe is easy to cause thermal cracks, pores or thermal stress cracks in the heat-affected zone of the weld.

When welding Q345B seamless steel pipe with submerged arc welding, in addition to the correct selection of flux, welding wire and electrode, it is also necessary to clean the oil rust and moisture on the surface of Q345B seamless steel pipe before welding, and strictly control the drying temperature and time of flux and electrode. The use of short-arc welding and other measures during operation can prevent the generation of pores to a large extent, improve the welding quality of Q345B seamless steel pipes, and reduce the repair rate. Using a reasonable welding process can largely prevent the occurrence of welding cracks in Q345B seamless steel pipes.

Q345B seamless steel pipe welded joints have higher strength and lower plasticity and toughness. There is Widmanstatten structure in the welded joint of Q345B seamless steel pipe, which is prone to embrittlement and is the weak link in the joint. It is advisable to use low-energy welding during production.