Thermoforming steel with tensile strength of 1,700MPa level and production method thereof

Abstract

The invention discloses thermoforming steel with tensile strength of 1,700MPa level, which consists of the following components in percentage by weight: 0.27-0.50% of C, 0.28-0.50% of Si, 1.20-1.60% of Mn, 0.32-0.60% of Cr, 0.025-0.055% of Ti, 0.002-0.005% of B, 0.010-0.06% of Als, less than or equal to 0.012% of P, 0.010-0.035% of Nb or 0.30-0.45% of Mo or less than or equal to 0.50% of the mixture of Nb and Mo, less than or equal to 0.008% of S, less than or equal to 0.005% of N and less than or equal to 0.005% of O. A production method comprises the following steps of: molten iron desulphurization, converter smelting and blank casting; heating of the cast blank; rough rolling; finish rolling; laminar cooling; reeling; acid pickling and cold rolling; annealing; flattening; finishing and shearing; heating in protective atmosphere; moulding; quenching; and low-temperature tempering for later use. According to the thermoforming steel disclosed by the invention, the tensile strength is greater than 1,700MPa, and the yield ratio is not over 0.70; when used for manufacturing structural parts and safety parts of an automobile, the thermoforming steel not only can reduce the body weight of the automobile, but also can realize yield deformation in the case of automobile accidents to absorb energy and impact force; and therefore, the thermoforming steel is not broken immediately, and the safety of a driver and passengers is effectively protected.

Description

technical field [0001] The invention relates to a steel for automobiles and a production method thereof, in particular to hot-formed steel with a tensile strength of 1700MPa and a production method thereof. Background technique [0002] In order to cope with global warming and energy crisis, energy conservation and emission reduction, low-carbon era, has become a common topic of the global automobile industry. Research figures show that every 10% reduction in vehicle weight can increase fuel efficiency by 6% to 8%. The use of high-strength and ultra-high-strength steels has an effective effect on vehicle weight reduction and has long been a high consensus among automotive engineers all over the world. . [0003] However, with the continuous improvement of the strength of the steel used for the car body, its plasticity and formability are greatly reduced, and cracking and springback are prone to occur during the forming process, which seriously affects the shape and dimensio...

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Problems solved by technology

[0006] [Document 5] The Chinese patent with the application number CN201110269388 "A Heat Treatment Method for High-Strength and Toughness Thermoformed Steel Sheets for Automobiles" discloses a heat treatment method for high-strength and toughness thermoformed steel sheets for automobiles, which belongs to the technical field of high-strength steels for automobiles. To solve the problems of high strength but poor plasticity of the steel plate for hot forming at present, the technical measures to solve the problem: the mass percentage of the components is: C: 0.2-0.4%, Si: 0.1-0.5%, Mn: 1.0- 2.0%, Cr: 0.1~0.5%, B: 0.001~0.005%, Ti: 0.01~0.05%, Al: 0.01~0.1%, P: <0.02%, S: <0.01%, N: <0.01%, remainder The hot-forming steel plate containing iron and unavoidable impurities is tempered in the range of 100-500°C for 1-5 minutes after stamping, which can significantly improve the plasticity of the hot-forming steel and improve the toughness of the steel plate after hot stamping

This patent introduces a heat treatment method for steel plates, which takes a long time for tempering and has low production efficiency

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