Guaranteed Hardness Limit in the Heat-Affected Zone
The guaranteed hardness limit in the heat-affected zone is a specified maximum value for Vickers hardness in that area. It ensures mechanical resistance and prevents brittle failure.
Physical-Chemical Mechanism of Action
The guaranteed hardness limit is determined by the thermal behavior of the metal during welding. At too high temperatures, the metal can transform into a harder phase such as martensite, which increases hardness but also susceptibility to cracking.
Metallurgical Relevance & Risks in Welding
Excessive hardness can lead to brittle failure and hot cracking. This can cause component damage and total failure. The guaranteed hardness limit therefore protects against these risks.
Workshop Practice & Instructions
To meet the guaranteed hardness limit, the weld volume and cooling steps must be precisely controlled. The maximum Vickers hardness in the critical area should not exceed the specified limit. For steels with high carbon content, careful control of cooling rate is essential.