High-strength hot-formed steel base plate with tensile strength greater than 2200MPa and preparation method

Abstract

The invention discloses a high-strength hot-formed steel base plate with the tensile strength larger than 2200 MPa and a preparation method, and belongs to the field of metal materials. The high-strength hot-formed steel base plate comprises the following components of, in percentage by mass, 0.40%-0.44% of C, 0.35%-0.44% of Si, 1.4%-1.5% of Mn, 1.9%-2.4% of Cr, P less than or equal to 0.01%, S less than or equal to 0.005%, 0.015%-0.055% of rare earth element Y, 0.045%-0.06% of Nb, 0.15%-0.2% of V and the balance Fe and inevitable impurities, and V / Nb = 2.5-4.5. According to the method, a cold-rolled steel plate is heated to 700-730 DEG C, heat preservation is conducted for 2-4 h, then air cooling is conducted to the room temperature, the microstructure of the obtained hot-formed steel base plate is ferrite, spherical carbide (the average diameter is 0.1-0.4 microns) and a small amount of intergranular blocky martensite (the volume fraction is 4%-10%), and the hot-formed steel base plate is low in yield strength and tensile strength, high in ductility and excellent in comprehensive mechanical property; g a tensile curve shows a continuous yield characteristic, so that the pre-cold stamping forming performance before hot stamping forming is improved. and after the hot-formed base plate (annealed plate) is subjected to hot forming process quenching treatment, the tensile strength is larger than 2200 MPa, the ductility is larger than or equal to 7.5%, and the technical requirement for automobile light weight is met.

Description

technical field [0001] The invention belongs to the field of metal material processing, and in particular relates to a high-strength hot-formed steel substrate with a tensile strength greater than 2200 MPa and a preparation method that is easy to be prepared by cold stamping in advance. Background technique [0002] With the introduction of concepts such as "lightweight" and "carbon neutrality" of automobiles and the increasingly stringent collision regulations, the strength of steel used in automobiles has been greatly improved. There are many deficiencies in the process, so high-strength hot stamping technology emerges in response to the situation. The hot-formed steel parts that have been commercially applied are mainly 1500MPa grade (22MnB5), 1800MPa grade (30MnB5) and 2000MPa grade (35MnB5). to a very important role. [0003] Most of the hot forming substrates provided by steel mills to customers are annealed steel plates, which are characterized by low strength, low ...

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Problems solved by technology

[0004] Chinese invention patent application (application publication number CN 106811689 A, application publication date: 2017-06-09) discloses a method for preparing hot-formed steel with a tensile strength ≥ 2000 MPa, and its chemical composition mass percentage is: C: 0.3% ~0.5%, Si: 1.2%~1.7%, Mn: 1.4%~2.0%, Als: 0.01%~0.07%, Cr≤1.5%, P≤0.008%, S≤0.005%, B: 0.001%~0.01% , Ti: 0.05% to 0.1%, Nb: 0.01% to 0.08%, and the rest are Fe and unavoidable impurity elements. The hot-formed steel substrate is obtained by smelting, hot rolling, cold rolling, and bell annealing. Among them, when bell annealing The temperature is 700 ℃, and this temperature is kept for 8 hours, and the yield strength is 424MPa, the tensile strength is 616MPa, and the elongation is 19.5%. The annealing time is longer, and the chemical The composition is relatively complex, the Si content is high, and the high Si oxide scale that is difficult to remove on the surface affects the surface quality. The addition of B and Ti elements is easy to form inclusions and reduce the elongation and fatigue properties of the steel.

[0005] Chinese invention patent application (application publication number CN 110257702 B, application publication date: 2021-04-27) publicly released a steel for hot stamping forming and its hot forming method. The chemical composition and quality of the hot forming steel are The content is: C: 0.11% ~ 0.30%, Si: 0.19% ~ 0.35%, Mn: 0.8% ~ 1.9%, Als: 0.015% ~ 0.06%, Cr: 0.21% ~ 0.50%, P≤0.010%, S ≤0.010%, Mo: 0.11%~0.25%, Ni≤3.0%, Nb: 0.03%~0.07%, Ca: 0.0004%~0.006%, and contain one or more of the following elements: B: 0.0004%~ 0.005%, Ti: 0.046% ~ 0.06%, the rest is Fe and unavoidable impurity elements, and its production process is: smelting-continuous casting-slab heating-hot continuous rolling-pickling-cold rolling-annealing-blanking- Hot forming, the patent does not give the annealing process and mechanical properties of the substrate before hot forming, adding precious alloy elements such as Mo and Ni, resulting in high production costs, and its tensile strength level is low, only 1500MPa level

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