Allotropic modification
Allotropic modifications are different crystal structures of the same element, which differ by temperature and pressure. For example, carbon occurs in nature as diamond (hard) and graphite (soft) as allotropes.
Physical-Chemical Mechanism of Action
A chemical element can adopt different crystal structures under various conditions such as temperature and pressure. These different structures are called allotropes.
Metallurgical Relevance & Welding Risks
In metallurgy, certain allotropes can form at specific temperatures or pressures, affecting the material's properties. For example, carbon in steel can exist as martensite or austenite, depending on cooling rate and alloying elements.
Workshop Practice & Instructions
When welding, it is important to ensure the correct allotropic modification. For example, with steel: Rapid cooling can produce martensite, making the material hard and crack-sensitive. Slow cooling forms pearlite, which is softer but less tough. The cooling rate should therefore be precisely controlled.