Method for improving strength and toughness of high-strength steel for coal machine by utilizing ultra-fast cooling and steel plate self-tempering technologies

Abstract

The invention discloses a method for improving the strength and toughness of the high-strength steel for a coal machine by utilizing the ultra-fast cooling and steel plate self-tempering technologies. The method is characterized by comprising the following steps: heating a plate blank, performing rough rolling, performing finish rolling, performing ultra-fast cooling and performing steel plate self-tempering. Particularly, the soaking temperature and soaking time of the plate blank, the rough rolling initial rolling temperature, the rough rolling single-pass reduction ratio, the finish rolling initial rolling temperature, the finish rolling single-pass reduction ratio, the ultra-fast cooling initial cooling temperature, the ultra-fast cooling final cooling temperature, the ultra-fast cooling speed, the self-tempering stacking temperature, the self-tempering time and other parameters are controlled. Therefore, the produced high-strength steel for the coal machine has excellent combination of strength and toughness and the ductile transition temperature is below -60 DEG C. The hard phase content of the duplex structure can reach 30-40%, the tensile strength of the steel plate is 1200-1350MPa, and the yield ratio is lower and is about 0.80. By adopting the self-tempering treatment, the internal stress of the structure can be eliminated, so that the structure has 60-70% of soft phase, the plasticity index can be obviously increased and the elongation rate can reach 25%.

Description

Technical field: [0001] The invention relates to a technology for improving the strength and toughness of steel plates, and is a method for improving the strength and toughness of high-strength steel for coal machinery by using ultra-fast cooling and steel plate self-tempering technology. Background technique: [0002] In the traditional controlled rolling and controlled cooling process, due to the limited cooling control ability, more strain energy must be accumulated during the rolling process, which is mostly achieved by low temperature and high pressure, strong plastic deformation, two-phase zone rolling, etc., especially Especially in the stage of cooling control, the convective exchange coefficient of cooling water and hot steel plate is much greater than the thermal conductivity coefficient of steam and hot steel plate, the steam film is not easy to be broken, and the ideal cooling control effect cannot be achieved. At the same time, due to uneven cooling, it is easy ...

AI Technical Summary

Problems solved by technology

[0002] In the traditional controlled rolling and controlled cooling process, due to the limited cooling control ability, more strain energy must be accumulated during the rolling process, which is mostly achieved by low temperature and high pressure, strong plastic deformation, two-phase zone rolling, etc., especially In the stage of cooling control, the convective exchange coefficient of cooling water and hot steel plate is much greater than the thermal conductivity coefficient of steam and hot steel plate, the steam film is not easy to be broken, and the ideal cooling effect cannot be achieved.

At the same time, due to uneven cooling, it is easy to cause warping of the steel plate

From the perspective of performance indicators, the most common disadvantages of the traditional controlled rolling and controlled cooling process are the low elongation of the steel plate, no yield point, and poor plasticity

At present, the common way to solve the above defects is to make up for it through heat treatment process, but it increases the cost and prolongs the manufacturing cycle