Microstructure evolution of nanostructured bainite in tempered zone during welding and regeneration has been analysed. The effect of welding heat input on microstructure and mechanical properties is investigated. Results show that cementite precipitation and nanostructured bainite regeneration occur in tempered zone. When heat input is reduced, the size and amount of cementite decrease, while the volume per cent of retained austenite increases. At the same time, the tensile strength in tempered zone increases with welding heat input decreasing. A welded joint of nanostructured bainitic steel with tensile performance almost the same as base metal is obtained by laser beam welding with regeneration.
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