Causes and solutions of cracks in titanium plate and titanium steel composite plate

Crack is a common defect in titanium plate welding. Titanium weld cracks belong to cold cracks, mainly caused by hydrogen in the weld. The main source of hydrogen is the water and oil in the plate and welding wire, and the environmental humidity is the main reason for the hydrogen increase in the weld.

During welding, under the action of high temperature, a large amount of hydrogen is dissolved in the molten pool. During the cooling and solidification process of the weld, hydrogen is easy to escape due to the rapid reduction of solubility. If the cooling speed of the weld is too fast, the hydrogen cannot escape and remain in the weld, which will make the hydrogen in the weld in a supersaturated state, so the hydrogen should be vigorously diffused and promote further embrittlement in this area.

If there is a notch effect at this site, and the concentration of hydrogen is high enough, cracks may occur. Especially in the winter construction, the ambient temperature is low, and the water vapor is attached to the titanium plate, creating conditions for the hydrogen increase of the weld. Because the titanium plate is too thin (1.2mm), the steel plate is relatively "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 has no time to escape, and exists in the form of supersaturation in the weld, which eventually leads to the emergence of cracks.

Therefore, in the welding process of titanium steel composite plate, it is necessary to carefully clean the surface of the base material and welding wire, and keep the ambient temperature not lower than 5 ° C. In winter construction, the flame is used to preheat the base steel surface, one is to remove the moisture around the weld; The second is to increase the temperature of welds and reduce the cooling speed of welds.