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Reasons and solutions for cracks in titanium plates and titanium steel composite plates

Cracks are common defects in titanium plate welding. Titanium weld cracks belong to cold cracks, mainly caused by hydrogen in the weld. The main sources of hydrogen are moisture and oil stains in the plates and welding wires, and environmental humidity is the main reason for hydrogen enrichment in welds.
During welding, a large amount of hydrogen dissolves in the molten pool under high temperature. During the cooling and solidification process of the weld, due to the rapid decrease in solubility, hydrogen is easily released. If the cooling rate of the weld seam is too fast, hydrogen will not have time to escape and remain in the weld seam, causing the hydrogen in the weld seam to be in a supersaturated state. Therefore, hydrogen needs to diffuse vigorously and promote further embrittlement in this area.
If there is a gap effect in this area and the concentration of hydrogen is high enough, cracks may occur. Especially during winter construction, when the ambient temperature is low, water vapor adheres to the titanium plate, creating conditions for hydrogenation of the weld seam. Due to the thin thickness of the titanium plate (1.2mm), the steel plate is relatively "warm" and the temperature rise is slow. The corresponding cooling rate of the titanium composite layer weld is too fast. During the cooling process, residual hydrogen in the weld cannot escape in time and exists in the form of supersaturation in the weld, ultimately leading to the appearance of cracks.
Therefore, during the welding process of titanium steel composite plates, the surfaces of the base material and welding wire should be carefully cleaned, and the ambient temperature should not be lower than 5 ℃. During winter construction, flame preheating should be applied to the base steel surface to remove moisture around the weld seam; The second is to increase the temperature of the welded parts and reduce the cooling rate of the weld seam.

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