Weldability Analysis of Q345R

Q345R steel is a low-alloy high-strength structural steel. It is currently the most widely used and used steel for pressure vessels in my country. It has good comprehensive mechanical properties and process properties and is suitable for important welded structures, especially pressure vessels. The general supply status is: hot rolling, cold rolling or normalizing treatment, etc.

The weldability of Q345R steel is better among low-alloy steels. Because it contains a certain amount of alloy elements, its hardenability and cold cracking tendencies are larger than those of low-carbon steel. When welding Q345R steel at room temperature, there is generally no hardened structure in the welding heat-affected zone, and its maximum hardness is usually less than 300HBS.

When welding at room temperature, the welding process is basically the same as that of low carbon steel. The tensile strength of Q345R steel is 460-640MPa. According to the requirements of equal strength, E50 type electrode should be used. When the welding current is increased, the cooling rate will be slower, so the hardness is lower, that is, the hardening tendency becomes smaller.

When welding Q345R steel at low temperature, hardened structure may appear, which is easy to produce welding cracks. Therefore, when welding Q345R steel at low temperature and thick plate, preheating measures should be taken to prevent cracks caused by hardened structure.