Heat-Affected Zone
The heat-affected zone is the area of metal that is altered by welding without melting. Here the microstructure changes and affects mechanical strength.
Physical and chemical mechanism of action
The heat-affected zone (HAZ) develops from the thermal energy transferred into the surrounding metal during welding. In this zone, the atomic arrangement and structure of the material change without fully melting.
Metallurgical relevance and welding risks
The HAZ affects the mechanical properties of the weld, like its strength and toughness. A too-wide HAZ can cause a loss of toughness and make the weld more prone to cracking. It can also alter the appearance and chemical properties of the material.
Shop practice and action instructions
To create an optimal HAZ, it's important to carefully control the welding temperature and time. Too high a temperature can lead to too-wide a HAZ, while too low a temperature means the HAZ won't be properly transformed. Recommended welding parameters vary by material and application.