Transformation Hardening
Transformation hardening occurs through rapid cooling of metals from high temperature, leading to a metastable, stressed microstructure.
Physicochemical Mechanism of Action
In transformation hardening, the metal is formed in a high-temperature state and then cooled very rapidly. This prevents the metal from transforming into its natural, more stable structure. The resulting microstructure is metastable and under stress.
Metallurgical Relevance & Risks in Welding
Transformation hardening can lead to increased hardness and toughness, which makes the material harder to machine. It can also lead to cracking and hot cracking if the metal is not treated correctly. This can be a problem especially with stiff steels like martensite.
Workshop Practice & Action Guidelines
To avoid or control transformation hardening, it's important to precisely regulate the cooling rate of the metal. For stiff steels like martensite, cooling should be slow to ensure a uniform hardness distribution. This can be achieved by choosing the right welding method and parameters.