Heat-affected zone
The heat-affected zone is the area of the material that is microstructurally altered by the welding heat without melting. Critical microstructural changes often occur here, which can affect component strength.
Physical and chemical mechanism of action
The heat-affected zone (HAZ) is the area of the material around the weld where the temperature is elevated but the material doesn't melt. In this zone, the atomic structure and microstructure of the material change due to thermal diffusion of atoms from the weld pool.
Metallurgical relevance and welding risks
The HAZ can cause various microstructural changes, such as the formation of martensite or austenite. These can affect the strength and hardness of the material and lead to cold cracks or hot cracks if not handled correctly. An overly large HAZ can also lead to a loss of toughness and a deterioration in mechanical properties.
Shop practice and action instructions
To minimize the negative effects of the HAZ, it's important to ensure proper welding temperature and time. Post-weld heat treatment (tempering) can help stabilize the microstructure and improve mechanical properties. For critical components, it's advisable to limit the HAZ with special welding processes like TIG or MIG.