Development And Application Of Two-Stage Cooling Processes For Laminar Cooling Of Hot-Rolled Layer

With the economic development slowing down,the overcapacity situation in the steel industry is even more prominent.In order to improve product efficiency and optimize product structure,technicians of steel enterprises are required to apply various methods to achieve quality reduction and reduction of steel products.As an advanced controlled cooling process in the hot rolling process,the two-stage cooling process can realize the control of the microstructure of the product by formulating reasonable process parameters,thereby obtaining the desired product performance.This article takes 1580 hot rolled coil production line of TangSteel as the platform,using the two-stage cooling process to conduct research based on C-Mn products,the product performance optimization and cost saving have been realized,and specific products for specific purposes have been developed in combination with actual market demands,which have been recognized by users.Through the performance optimization and development of C-Mn products and Nb and Ti microalloyed products,the effects of various parameters of the two-stage cooling process and the addition of alloying elements on the microstructure and properties of the products were studied.Adding Nb and Ti elements can effectively refine product structure,improve product strength,inhibit the formation of pro-eutectoid ferrite,reduce the diffusion distance of carbon,avoid the formation of large carbon-rich structures,improve the uniformity of the microstructure distribution of hot rolled products,which is conducive to improving the performance uniformity of the products.When the double-stage cooling process is applied,increasing the deformation of the austenite in the non-recrystallized zone,prolonging the air cooling time,and adding Si and Al elements can promote the formation of ferrite,thereby obtaining a higher proportion of ferrite.Extending the air cooling time and adding Si and Al elements will simultaneously promote the diffusion of C to the retained austenite,reduce the strength of the ferrite matrix,and help to optimize the plasticity of the product.However,prolonging the aircooling time for the products with higher C and Mn content will increase the secondary banded structure in combination with the influence of dendritic segregation.The double-stage cooling process and the bainite forming temperature coiling process can improve the phase transformation ratio of the high-hardenability steel such as the dualphase steel for cold rolling in the laminar cooling system of the hot-rolled layer,and improve the coil collapse problem.At the same time,combined with the reasonable control of the finishing temperature and the cooling rate of the layer,the band structure can be improved.Figure39;Table37;Reference 51.