How is a steel structure normalized after welding?

• A. Quench in water.
• B. Heat above the critical temperature and cool in still air.
• C. Cool rapidly in air.
• D. Quench in oil.

Answer: (B)

Normalizing a welded steel structure means heating the steel to a temperature above the point where its structure becomes austenite (above the upper critical temperature) and then letting it cool in still air. This process refines the grain and produces a uniform, ductile microstructure of ferrite and pearlite, which helps relieve weld-induced residual stresses and improves toughness across the weld and heat-affected zone. Quenching in water or oil cools the metal too rapidly and typically forms hard, brittle structures like martensite, which is not desirable after welding. Cooling rapidly in air without first heating above critical may not relieve stresses or refine grain as effectively, while still air cooling after a high-temperature austenitizing treatment is the standard method to achieve a balance of strength and toughness.