Causes and solutions for cracks in titanium plates and titanium-steel composite plates
Cracks are a common defect in the welding of titanium plates. Titanium welding cracks are cold cracks, mainly caused by hydrogen in the weld. The source of hydrogen is mainly moisture and oil in the sheet and welding wire, and environmental humidity is the main reason for the increase in hydrogen in the weld.
During the welding process, a large amount of hydrogen is dissolved in the bath at high temperature. During the cooling and solidification process of the weld, hydrogen can easily escape due to the rapid decrease in solubility. If the weld cools too quickly, the hydrogen will not have time to escape and remain in the weld, which will oversaturate the hydrogen in the weld. Therefore, hydrogen will try its best to diffuse and cause further brittleness in the area.
If there is a notch effect in this area and the concentration of hydrogen is high enough, cracks may occur. Especially in winter construction, the ambient temperature is low, and water vapor is attached to the titanium plate, creating conditions for hydrogenation in the welds. Because the titanium plate is too thin (1.2mm), and the steel plate is relatively "temperature sensitive", the temperature rises slowly, and the corresponding titanium composite layer weld cools too quickly. During the cooling process, the residual hydrogen in the weld does not have time to escape, and it is present in the weld in the form of supersaturation, which eventually leads to the appearance of cracks. There are many causes and factors that cause cracks in the welding process, such as unreasonable structural design, improper process parameters, material problems, improper handling after welding, environmental and operating factors.
Therefore, in the welding process of titanium-steel composite panels, the surface of the base material and welding wire must be carefully cleaned, and the ambient temperature must not be lower than 5℃. During winter construction, a flame should be used to preheat the surface of the base steel to remove moisture from around the weld, increase the temperature of the weld, and reduce the cooling speed of the weld.
Titanium alloy welding cracks are the result of a combination of multiple factors, and each link needs to be systematically controlled. From material pretreatment, gas protection, parameter optimization to post-welding treatment, every step needs to be strictly controlled. In practical applications, it is recommended to conduct process evaluation and sample testing to ensure the quality of welding.
