Welding Process and Application of Q345 Steel Flat Bar

Welding Process and Application of Q345 Steel Flat Bar

Q345 steel flat bar has good comprehensive mechanical properties, low temperature impact toughness, cold stamping and machinability, and can be used to manufacture welded structures for large ships, railway vehicles, bridges, pipelines, etc., which requires not only good mechanical properties, but also good soldering properties. Q345 steel flat bar has a wide range of applications, and the welding-related structures mainly include various large combined gears, turbine rotors, turbine runners and various shafts. Q345 steel flat bar is low-alloy high-strength structural steel with high strength, high toughness, good corrosion resistance, good weldability and cold forming ability. Q345 steel is generally used in hot rolled state and has good comprehensive mechanical properties. Q345 steel has good toughness at low temperature, and the impact energy at -40 °C is greater than or equal to 27J. If it is used to improve the performance of the weld zone, once normalizing treatment can be carried out.

When we choose welding material, two aspects must be considered. First, there must be no defects in the weld, and second, the performance requirements should be met. The hot cracking and cold cracking tendency of the weld metal of Q345 steel flat bar is not big under normal conditions. Therefore, the main basis for selecting the welding material during Q345 steel welding is to ensure the strength, toughness, plasticity and other mechanical properties of the weld metal match with the base metal. Q345 steel is suitable for various welding methods. Selecting appropriate process parameters is mainly according to the thickness of the material, the structure of the product and the specific construction conditions. The choice of welding materials should be according to two aspects. We should ensure that the weld is free of defects and meet the performance requirements. When we weld Q345 steel, the welding material of the corresponding strength grade must be selected. The influence of fusion ratio and cooling rate must be considered at the same time. The influence of heat treatment on the mechanical properties of the weld must be considered. The determination of the welding line energy is mainly determined by the embrittlement and cold cracking in the superheated zone.

When we  weld Q345 steel with a low carbon, there is basically no strict limit on the line energy because this kind of steel is not sensitive to overheating. In addition, their hardening tendency and cold cracking sensitivity are not big. If you increase the plasticity and toughness of the overheated zone, the line energy is smaller and more powerful. When we weld Q345 steel with high carbon content, the carbon content of martensite is also high due to the increased tendency of hardening, the tendency of cold cracking is increased when the energy of small line is increased, and the embrittlement of overheated area becomes serious. Therefore, in this case, the line energy needs to be rather larger.

Q345 steel is one of the most widely used mechanical structures in industrial design and production, mainly used for engineering structure welding. Through the analysis of the welding process of Q345 steel, the appropriate welding materials, welding process and welding method should be selected according to the actual application in the welding process. At the same time, we should also pay attention to the problems that are easy to occur in the welding process. The prevention measures should be taken in consideration of various factors, and the welding should be carried out correctly to ensure the excellent welding quality. All of this provides a basis for us to better utilize the Q345 engineering structural steel.