SM490B Z-direction steel is a high-tech high-rise building structural steel, which requires good welding performance, comprehensive mechanical properties, and lamellar tear resistance.
The layered tear resistance of SM490B steel is evaluated by the reduction of area in the thickness direction test, which is mainly related to the sulfur content and inclusion content of SM490B steel. From the performance of the z-direction steel produced by the company, the reduction of area is related to the sulfur content. Negative correlation, that is: the lower the sulfur content, the higher the reduction of area, and the physical level of chemical composition and mechanical properties of SM 490B-Z25 steel is higher.
1) When the steel ingot is rolling 8~100mm thick steel plate (continuous casting slab rolling 8~80mm) thick steel plate, the appropriate carbon content is 0.38%~0.44%. When the carbon equivalent is lower than 0.38%, try to arrange rolling of thinner specification SM490B steel to prevent the strength performance from exceeding the lower limit of the standard.
2) In the case of appropriate carbon equivalent and rolling process, the performance of hot-rolled SM490B steel can meet the requirements of technical standards.
3) For steel used in high-rise building structures for important purposes, internal control standards should be established for composition and performance, and the lower limit (or close to the lower limit) of the performance value should be avoided.
4) At present, the z-direction steel of SM 490B produced by the company adopts microalloying (adding Nb, V) and normalizing treatment. It is hoped that the relevant units will not add microalloying elements during smelting and use controlled rolling during rolling. Conduct analysis and research to optimize the production process and reduce production costs while ensuring the performance of SM490B steel.
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