THICK 420 MPA GRADE LOW YIELD RATIO LOW TEMPERATURE BRIDGE STEEL AND PRODUCTION METHOD

摘要

Disclosed is a thick 420 MPa grade low yield ratio low temperature bridge steel plate and a production method. In the present invention, processes such as rolling, cooling, and a tempering heat treatment performed on a 100 mm thick steel plate are appropriately controlled, so as to resolve the long-standing issue of unstable performance of a thick plate. A tempering heat treatment can improve low-temperature impact toughness of a steel plate; however, selecting an inappropriate temperature point for tempering can cause temper embrittlement that reduces the toughness of a steel plate. The invention has a low-carbon design to ensure favorable welding performance of a steel plate. Appropriate rolling and cooling, as well as a reasonable tempering heat treatment are applied to ensure uniformity of a steel structure and performance of the steel plate, thereby obtaining structural bridge steel having favorable performance indicators.