The causes and solutions of titanium plate welding cracks

I. Hydrogen is the primary cause of cold cracks in titanium welds. It mainly "intrudes" into the welding process through two channels: Firstly, the moisture and oil present on the plates and welding wires will release hydrogen during the welding process; Secondly, the environmental humidity acts as an accomplice, significantly increasing the hydrogen content in the weld.

During welding, high temperatures cause a large amount of hydrogen to dissolve into the molten pool. However, when the weld cools and solidifies, the solubility of hydrogen drops sharply. The hydrogen that should have escaped will be trapped in the weld if it encounters an overly rapid cooling rate, resulting in the hydrogen being in an oversaturated state. These "nowhere to escape" hydrogen will continuously spread, making the surrounding area vulnerable and laying a "time bomb" for crack formation.

1. Gap effect + High hydrogen concentration: Dual threats amplify risks
When there is a notch in the weld seam, local stress concentration will occur; and when the hydrogen concentration reaches a certain level, it will reduce the toughness of the material. These two factors "working together" will cause the probability of cracks to rise sharply, just like adding insult to injury to the already fragile weld seam.

2. Winter Construction: Special Challenges Arising from Low Temperatures
In winter, the temperature is low, and water vapor easily adheres to the surface of the titanium plate, creating favorable conditions for hydrogenation of the weld. Especially for the thin titanium plate with a thickness of only 1.2mm, due to its "heat absorption" property - the temperature rises slowly, it causes the cooling speed of the titanium composite layer weld to be too fast. During this rapid cooling process, the residual hydrogen in the weld has no time to escape and can only remain in the weld in an oversaturated state, eventually causing cracks.

II. Solving the Crack Problem
1. Surface cleaning: Prevent hydrogen "invasion" at the source
Before welding, it is essential to thoroughly clean the surface of the base material and the welding wire. This is a crucial step in reducing the hydrogen source. Mechanical cleaning (such as grinding) or chemical cleaning methods can be used to completely remove impurities such as moisture and oil from the surface, ensuring that the base material and the welding wire are clean and dry, laying a good foundation for the subsequent welding process.

2. Environmental Control: Creating an Appropriate "Welding Microclimate"
The welding environment temperature must not be lower than 5℃. This is an important prerequisite for preventing cracks from forming. During winter construction, when the ambient temperature is low, the base steel surface can be preheated by flames to deal with the situation: it can not only remove the moisture around the weld seam and reduce the source of hydrogen; but also raise the temperature of the weldment, slow down the cooling speed of the weld seam, and give hydrogen sufficient time to escape, avoiding over-saturation residue.

3. Process Optimization: Utilize parameter control to reduce risks
Reasonable adjustment of welding parameters is crucial for preventing cracks. For instance, appropriately adjusting the welding current, voltage and welding speed can effectively control the cooling rate of the weld. By optimizing the welding process and making the cooling process of the weld more stable, there will be sufficient time for hydrogen to escape, thereby reducing the possibility of crack formation at the process level.