Heat Affected Zone Hardening Factor
The heat-affected zone hardening factor measures the relative hardness increase in the weld and surrounding area. It is crucial for assessing the risk of hydrogen cracking.
Physical-Chemical Mechanism of Action
The hardening factor indicates how much the hardness in the heat-affected zone (HAZ) is increased compared to the unaffected base material. This happens due to changed grain size and crystal structure.
Metallurgical Relevance & Risks in Welding
A hardening factor that is too high can lead to the formation of hydrogen cracks, especially in hard steels like martensite. This increases the risk of stress corrosion cracking and reduces the service life of the weld.
Workshop Practice & Action Guidelines
To minimize the hardening factor, ensure proper cooling. For hard steels, use controlled cooling methods such as post-weld heat treatment. For high-hardening materials (e.g., HSS), the maximum hardness in the HAZ should be limited to 500 HB or less.