The occurrence of cracks in the titanium plate and the countermeasures

Titanium weld cracks are cold cracks, mainly caused by hydrogen in the weld. The main sources of hydrogen are moisture and oil in the sheet and welding wire, and environmental humidity is the main reason for the increase in hydrogen in the weld.

Under the action of high temperature during welding, a large amount of hydrogen dissolves in the molten pool. During the cooling and solidification process of the weld, the hydrogen easily escapes due to the rapid decrease in insolubility. If the welding seam cooling rate is too fast, hydrogen can not escape and remain in the welding seam, which will make the hydrogen in the welding seam supersaturated, so the hydrogen has to diffuse as much as possible and promote further embrittlement of this area.

If there is a notch effect in this part 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 hydrogenation of the weld. Because the titanium plate is too thin (1.2mm), the steel plate is relatively "hot" and the temperature rises slowly, and the corresponding titanium composite layer welding seam is cooled too fast. During the cooling process, the residual hydrogen in the welding seam is too late to escape. It exists in the form of supersaturation in the weld, which eventually leads to the appearance of cracks.

Therefore, during the welding process of the titanium steel clad plate, the surface of the base metal and welding wire must be carefully cleaned, and the ambient temperature must not be lower than 5°C. During winter construction, flames are used to preheat the base steel surface, one is to remove the moisture around the weld; the other is to increase the temperature of the weldment and reduce the cooling rate of the weld.
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