Carbon steel can be divided into low carbon steel, medium carbon steel and high carbon steel according to the carbon content. In the actual carbon steel welding process, the selection of appropriate welding materials, process parameters, and whether to take measures such as preheating and postheating are all key factors to ensure welding quality. Therefore, understanding the welding properties of various carbon steels is very important for subsequent welding work.
Welding Properties of Various Carbon Steels:
First, there is mild steel. Generally speaking, the carbon content in steel directly affects the quality of its welding performance. The carbon content of low carbon steel is between 0.10 and 0.25%. In addition to good plasticity and toughness, it also has good welding performance. And generally no preheating or special processing is required during welding. However, when the ambient temperature is lower than -5°C, proper preheating is required and alkaline welding rods are used for welding. In addition, when processing low carbon steel with high carbon and sulfur content, in addition to using high-quality low-hydrogen welding rods, measures such as preheating and postheating are also required to prevent the occurrence of hot cracks that directly affect the final welding quality.
Secondly, there is medium carbon steel. The carbon content of medium carbon steel is between 0.25% and 0.60%. Compared with low carbon steel, the welding performance of medium carbon steel is poorer. Moreover, medium carbon steel has a greater tendency to harden during welding, reduces its plasticity, and is prone to welding. Cracks, poor welding performance. Especially as the carbon content of medium carbon steel increases, the weldability will gradually deteriorate. When welding medium carbon steel, it is necessary to use an alkaline electrode with good crack resistance and set the preheating temperature to above 150°C. Heat treatment is also required after welding to eliminate stress and reduce the tendency of cracks.
Finally, there is high carbon steel. The carbon content of high carbon steel is between 0.60% and 1.70%. Compared with medium carbon steel, high carbon steel has worse weldability. This type of steel has a high carbon content and is more prone to hardening and crack sensitivity after welding. Therefore, its weldability is extremely poor and cannot be used to manufacture welded structures. Since high carbon steel parts have high hardness and wear resistance, the material itself needs to be heat treated, so it should be annealed before welding. In addition, high carbon steel weldments should be preheated before welding, and the preheating temperature should be controlled above 250 to 350°C. The interlayer temperature must be maintained not lower than the preheating temperature during the welding process, and the weldments must be insulated after welding. Slowly cool and immediately put into the furnace for stress relief heat treatment at 650°C. Because high carbon steel is a type with poor welding performance, its welding work is mainly welding repair.
Conclusion
In summary, after comparison, it is found that among these three types of steel, low carbon steel has good welding performance and generally does not require preheating and special process measures during welding. The welding performance of medium carbon steel is second, and preheating and post-weld heat treatment are required to prevent the occurrence of cracks. High carbon steel has the worst welding performance and is most prone to cracks during the welding process, requiring special welding processes and subsequent heat treatment. Therefore, understanding the welding properties of various carbon steels will help us make the right choice when welding.
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