Production method of large-thickness high-toughness yield strength 1100MPa-grade ultrahigh-strength steel plate

Abstract

The invention relates to a production method of a large-thickness high-toughness yield strength 1100 MPa-grade ultrahigh-strength steel plate. The production method comprises the technological processes of converter or electric furnace steelmaking, LF refining, VD or RH vacuum degassing, Ca treatment, continuous casting, casting blank slow cooling diffusion treatment, heating, rolling, steel plateslow cooling diffusion treatment, quenching and tempering. Slow cooling diffusion treatment is carried out by adopting casting blank and steel plate offline residual heat. The casting blank slow cooling diffusion starting temperature is controlled to be 600-700 DEG C, the diffusion time is longer than or equal to 48 hours, and the diffusion ending temperature is smaller than or equal to 300 DEG C; the diffusion starting temperature of the steel plate is greater than or equal to 300 DEG C and the diffusion time is greater than or equal to 24 hours. By means of the two slow cooling diffusion processes, the content of harmful gas in the finished steel plate is greatly reduced, distribution of different chemical elements is homogenized, generation of internal stress of the steel plate is reduced, and a good foundation is laid for improving the ultralow-temperature impact toughness of the steel plate and the uniformity of the performance in the thickness direction.

Description

technical field [0001] The invention relates to, in particular, a large-thickness, high-toughness, yield strength 1100MPa grade ultra-high-strength steel plate and a production method thereof. Background technique [0002] High-strength steel plates with a yield strength of 1100MPa and above are mainly used in key stress-bearing parts of construction machinery such as booms, pull plates, rotating tables, and frames of construction cranes. They have high requirements for steel plate strength, toughness, welding, cutting, etc., and the current consumption is mainly 20mm and below thin gauge steel plate. In recent years, with the increasing number of large-scale and super-large mines, nuclear power, hydropower, wind power and other engineering projects around the world, the further large-scale construction machinery and equipment have gradually developed, and the high-strength steel plates with large thickness (≥40mm) yield strength Demand is also growing. [0003] As the thi...

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Problems solved by technology

[0003] As the thickness increases, the following problems are bound to be brought: (1) Due to the limitation of the quenching capacity of the quenching machine, the mechanical properties of the steel plate surface and the core are quite different; the problem of uneven performance along the thickness direction is difficult to solve; (2) It is difficult to guarantee the low-temperature impact toughness of large-thickness steel plates; especially for engineering applications in extremely cold regions, how to ensure the ultra-low temperature impact toughness of large-thickness steel plates in an environment of -60°C is a difficult problem

[0004] Chinese patent CN106191673B introduces a quenched ultra-high-strength steel plate with a yield strength of 1100MPa. The steel plate C: 0.15-0.20%; Mn: 1.00-1.40%. Performance; the thickness is thinner than 20mm; and there is no research on the impact toughness at -60°C ultra-low temperature;

[0008] To sum up, the current existing technologies involving ultra-high-strength steel plates with a yield strength of 1100MPa mainly solve the manufacturing problems of thin plates with a thickness of ≤40mm; and only study the low-temperature impact toughness in the environment of -40°C; There is no clear method for the core properties of large thickness steel plates and the ultra-low temperature impact toughness in the extremely cold environment of -60 °C

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