Method of making coated stamped parts and parts made therefrom

Abstract

The present invention relates to a method for manufacturing hot stamped coated parts, which method includes the following consecutive steps, in order: providing a hot-rolled or cold-rolled steel plate including a steel substrate and an aluminum-silicon alloy precoat, the precoat containing Greater than 50% free aluminum and with a thickness of 15 to 50 microns; the steel plate is then cut to obtain a pre-coated steel blank; the blank is then heated in a non-protective atmosphere to a temperature Ti of Te-10°C to Te, Te is the eutectic or solidus temperature of the precoat; the billet at temperature Ti is then heated to 840 to 950°C in a non-protective atmosphere at a heating rate V of 30°C / s to 90°C / s The temperature Tm of the coated heated blank is obtained, and V is the heating rate from the temperature Ti to the temperature Tm; then the coated heated blank is soaked at the temperature Tm for a time tm of 20s to 90s; and then hot stamped. The blank is obtained to obtain a hot stamped coated part; the stamped part is then cooled at a cooling rate to form a microstructure including at least one component selected from martensite or bainite in the steel substrate.

Description

technical field [0001] The invention relates to a method of manufacturing hot stamped parts prepared from steel sheets precoated with an aluminum-silicon alloy, and to hot stamped coated articles obtained by the method. Background technique [0002] Especially in the automotive industry the hot stamping method of pre-painted sheets has been widely used for the manufacture of components, since it allows the production of components with high mechanical resistance and good shock resistance. Metallic pre-coating avoids oxidation and decarburization of the steel substrate during furnace heating prior to hot stamping. An intermetallic alloy with a high melting temperature is formed in the coating by interdiffusion between the precoat and the steel substrate. The heating temperature is chosen to austenitize the steel so that further hardening of the steel substrate is also achieved by quenching in the forming tool. [0003] European patent specification EP0971044 discloses a met...

AI Technical Summary

Problems solved by technology

[0007] Attempts have been made to increase the productivity of the process by shortening the duration of soaking at the austenitizing temperature, however, limitations of the process have been found because for steel substrate elements, especially iron, with aluminum-based coatings The interdiffusion of

Furthermore, reducing the heating time is also a problem, since for very fast heating rates, melting of the coating is encountered, thus resulting in a smooth coating surface and weak adhesion of the paint to the stamped part

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