Method of production of steel sheet semi-finished products by press hardening with locally-modified structure in spots for welding

a technology of local modification and semi-finished products, which is applied in the direction of heat treatment furnaces, furnace types, furnace types, etc., can solve the problems of spot welding joints, relative poor ability to undergo plastic deformation, and structural failure risk under external loading, so as to improve the process and reduce the risk of structural failur

US20210040574A1Pending Publication Date: 2021-02-11ZAPADOCESKA UNIVERZITA V PLZNI
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
Publication Date
2021-02-11

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Abstract

A method for producing steel sheet semi-finished products (P) by press hardening is provided that utilizes locally-modified structure in spots for welding. During this method, a steel semi-finished product (P) is heated to a temperature at which complete transformation of ferritic-pearlitic structure to austenite occurs. Afterwards, the semi-finished product (P) is cooled locally in spots for welding to a temperature close to the Mf, after which heat conduction from the surroundings causes reheating and consequently annealing of the hardening structure. Subsequently, the semi-finished product (P) is formed into a drawn part which, at the same time, is hardened in the tool, after which the sheet semi-finished product (P) is retrieved from the tool, once the required temperature was reached.
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Description

RELATED APPLICATIONS

[0001] This application claims the priority benefit of Czech Patent Application Serial No. PV 2019-513 entitled “Method of production of steel sheet semi-finished products by press hardening with locally-modified structure in spots for welding,” filed Aug. 7, 2019, the entire disclosure of which is incorporated herein by reference.FIELD OF THE INVENTION

[0002] This invention relates to a method of producing steel sheet semi-finished products by press hardening with locally-modified structure in spots for welding.BACKGROUND ART

[0003] Materials for manufacturing steel sheet semi-finished products may include high-strength MnB steels, which possess a martensitic microstructure after processing. Such materials may be useful in car body construction. These materials may be produced by press hardening, which is a method of hardening in a tool. Therefore, these materials may show good strength, but may also exhibit a relatively poor ability to undergo plastic deformation, w...

Examples

Embodiment Construction

[0024]Steel blank P made of a sheet stock of 22MnB steel of 1.5 mm thickness is placed into a continuous heating furnace. It passes through the furnace for five minutes and heats up to 950° C., at which the initial ferritic-pearlitic structure transforms to austenite. Once this heating austenitizing process ends, the semi-finished product P is pushed out from the furnace and is set, with the aid of guides and stops and after two seconds, in an exactly-defined position in the cavity of a cooling fixture. At the same time, it is approached by a cooling head fitted with cooling nozzles 1. Over 2.5 seconds, the spots to be welded are cooled with water M pressurized at 6 bar. The cooling medium M is screened from the surroundings by a concentric shroud 2 whose diameter is 12 mm. The shroud 2 also guides the cooling medium M away from the spot being cooled. After the cooling ends, the semi-finished product P is transferred to a tool by means of a handling device. 5 to 7 seconds after the ...