Technical Difficulties and Chemical Composition of SM490YB Steel Plate

Technical Difficulties For the SM490YB steel plate, the normalizing treatment not only refines and uniforms the structure, but also eliminates a large number of dislocations generated during the rolling process, and the decrease in the dislocation density offsets the fine-grain strengthening effect. Compared with the hot-rolled SM490YB steel plate, The strength of the normalized steel plate is significantly reduced by 61. The thickness of the ultra-thick wind power structure SM490YB steel plate for low temperature environment is 115 mm, and the yield strength at 1/2 of the plate thickness is required to be > 315 MPa, the tensile strength is 490 ~ 610 MPa, and the elongation is > 21%. ;

At the same time, due to segregation and inclusions in the SM490YB steel plate, the quality of the core of the continuous casting slab is relatively poor, and the grains are coarse due to the slow cooling rate of the core of the extra-thick steel plate, which makes it difficult to obtain the toughness of the core, especially the low temperature toughness. Guaranteed, specific requirement -50 ℃ longitudinal Charpy (V-notch) impact absorbed energy value> 41 J.

Comprehensively considering the strength, toughness and welding performance requirements of the ultra-thick wind power structure SM490YB steel plate used in low temperature environment, the composition design with low carbon equivalent and low S content is adopted, and microalloying elements such as Nb, V, Ti, Al are added to refine the grain and precipitation strengthening , Add Ni element to improve the low temperature impact toughness of SM490YB steel plate and increase the strength.

Researched and analyzed the influence of cooling rate on the microstructure and hardness of SM490YB steel plate, as well as the influence of heating temperature and holding time on the microstructure and properties. Using 370 mm thick continuous casting slab, a 115 mm thick steel plate with excellent low-temperature impact performance at -50 °C was successfully developed. The ultra-thick wind power structure SM490YB steel plate has excellent physical quality and comprehensive performance, which fully meets the construction needs of large-scale wind power units at home and abroad.