Bismuth substitution effect
Bismuth replaces lead in free-machining steels and improves chip formation through fine particle distribution. Reduces environmental impact.
Physical-Chemical Mechanism of Action
Bismuth is used in steels to improve chip formation. It disperses as fine particles and promotes uniform chip distribution. This leads to increased strength and toughness of the material.
Metallurgical Relevance & Welding Risks
The bismuth substitution effect improves the mechanical properties of steel alloys by promoting chip formation. However, too much bismuth can alter the microstructure and lead to uneven cooling, posing risks to weld quality.
Workshop Practice & Action Guidelines
Use a bismuth content of 0.5 to 1% when manufacturing free-cutting steels. Ensure even distribution and control cooling steps to avoid uneven microstructure. When welding, maintain a slow cooling rate (t8/5 > 20 s) to minimize the risk of stress formations.