Forming Gas Diffusion Tightness
Backing gas diffusion tightness describes how well a material blocks backing gas and prevents it from diffusing into the weld. A high value means the gas is better contained.
Physico-Chemical Working Mechanism
Forming gas diffusion tightness refers to the ability of a material to block forming gas (like argon or helium). This is achieved through a dense surface structure or by chemically bonding the gas to the material.
Metallurgical Relevance & Welding Risks
A low diffusion tightness value causes too much forming gas to diffuse into the weld. This can lead to porosity and a poor shielding atmosphere, which alters the microstructure and reduces the strength of the weld. Additionally, it can cause hot cracking.
Workshop Practice & Instructions
To ensure good forming gas diffusion tightness, choose welding fixtures and tapes with a high diffusion tightness value. This can be achieved through special materials or processing techniques. Regularly check the integrity of the fixtures and replace them if they show signs of wear.