Cracking is a frequent defect in titanium plate welding. Titanium weld cracks are cold cracks, mainly caused by hydrogen in the weld. The source of hydrogen is mainly water and oil in the plate and wire, and the environmental humidity is the main reason for hydrogen increase in the weld.
Welding at high temperatures, a large amount of hydrogen dissolved in the molten pool, in the cooling and solidification process of the weld, due to the rapid decrease in solubility, hydrogen is very easy to escape. If the weld cooling rate is too fast, hydrogen can not escape in time to retain in the weld, will make the weld in the hydrogen in a supersaturated state, and therefore the hydrogen to try to diffuse, and promote further embrittlement of this region.
If there is a notch effect in this area and the hydrogen concentration is high enough, cracks may occur. Especially in winter construction, the ambient temperature is low, and water vapor adheres to the titanium plate, creating conditions for the weld to increase hydrogen. Due to the titanium plate is too thin (1.2mm), the steel plate is more "eat temperature", the temperature rises slowly, the corresponding titanium composite layer weld cooling speed is too fast, in the cooling process, the residual hydrogen in the weld can not escape in time, in the weld in the form of supersaturation, which ultimately leads to cracks.
If there is a notch effect in this area and the hydrogen concentration is high enough, cracks may occur. Especially in winter construction, the ambient temperature is low, and water vapor adheres to the titanium plate, creating conditions for the weld to increase hydrogen. Due to the titanium plate is too thin (1.2mm), the steel plate is more "eat temperature", the temperature rises slowly, the corresponding titanium composite layer weld cooling speed is too fast, in the cooling process, the residual hydrogen in the weld can not escape in time, in the weld in the form of supersaturation, which ultimately leads to cracks.
Therefore, in the welding process of titanium steel composite plate, the surface of the base material and welding wire should be carefully cleaned, and the ambient temperature should not be kept below 5℃. In winter construction, the flame should be used to preheat the steel surface of the base material, firstly, to remove the moisture around the weld; secondly, to increase the temperature of the weldment and reduce the cooling rate of the weldment.
