Reasons for Cold Cracks in Welding Robot Steel

The reason for cold cracks in steel welding using welding robots is that during the process of steel welding, there is still a continuous occurrence of cold cracks in the steel. There are many reasons for this situation, generally related to the chemical composition, steel degree, preheating temperature, and cooling conditions of the steel. In order to minimize the occurrence of cold cracking in steel to a large extent, it is necessary to pay attention to the following technical points: first, when welding steel, attention should be paid to the moisture in the welding material, rust and oil stains at the weld groove, and environmental humidity. In general, the amount of hydrogen in the base metal and welding wire is very small, while the moisture in the electrode coating and the moisture in the air cannot be ignored, becoming the main source of hydrogen enrichment. Secondly, the solubility and diffusion ability of hydrogen in different metal structures are different, and the solubility of hydrogen in austenite is much greater than that in ferrite. Therefore, during the transition from austenite to ferrite during welding, the solubility of hydrogen suddenly decreases. At the same time, the diffusion rate of hydrogen is exactly the opposite, suddenly increasing when transitioning from austenite to ferrite. Then, under the action of high temperature during welding, a large amount of hydrogen is dissolved in the molten pool. During the subsequent cooling and solidification process, due to the sharp decrease in solubility, hydrogen is vigorously released. However, due to rapid cooling, hydrogen cannot escape in time and remains in the weld metal to form diffusive hydrogen