Because of the low carbon content of low-carbon steel, manganese, silicon content is small, usually do not produce severe hardening due to welding or hardened tissue organization. Low carbon steel weld joints plasticity and impact toughness is good, welding, generally does not require preheating, temperature control and post-heat between layers, also without the use of post-weld heat treatment to improve the organization, the welding process does not have to take special measures for the process, weldability.

But in a few cases, the difficulties will arise when welding:

1) the use of high nitrogen content converter steel smelting old methods of production, impurity content and more, so cold brittle, aging increased sensitivity, reduced quality of welded joints, weldability.

2) boiling steel deoxidation incomplete, higher oxygen content, P and other impurities are unevenly distributed, localized content will be exceeded, the aging sensitivity and sensitivity to cold crisp big, hot cracking tendency increases.

3) The quality does not meet the requirements of welding, the weld metal in the carbon, sulfur content is too high, it will lead to cracks. When using an acid such as a factory Q235-A steel welding electrodes, due to the carbon content of the electrode coating ferromanganese too high, it will cause the weld thermal cracking.

4) Some welding method will reduce the quality of low-carbon steel welded joints. As electroslag welding, since the line energy, will HAZ coarse grain zone looks very coarse grains, causing a serious decline in the impact toughness, and must be normalized grain refinement after welding in order to progress impact toughness.

In short, low-carbon steel is the best part of the weldability, the most readily welded steel, all welding method can be applied to the welding of low carbon steel.