Heating treatment process of plated steel sheet for hot stamping

Abstract

The purpose of this invention is to provide a heat treatment method of a plated steel sheet for hot pressing, a method in which a hot-press formed article having sufficient coating adhesion and corrosion resistance can be stably obtained. According to this heat treatment method of a plated steel sheet for hot pressing, the plated steel sheet is heat treated before hot pressing in which rapid cooling for quenching is performed in a press mold. For this purpose, a slab specimen 10 is heated in the atmosphere in which oxygen concentration is >0 volume % or in which oxygen concentration is >=0 volume % with dew point >=0[deg.]C. Accordingly, on the surface of the slab specimen 10, there is formed a metallic oxide layer of the plating material, namely, a barrier layer such as zinc oxide or zinc hydroxide, for example. Thus, rapid oxidation is suitably suppressed when the article is taken out from a heating furnace, enabling the hot-pressed article to be stably obtained that has sufficient coating adhesion and corrosion resistance.

Description

technical field [0001] The present invention relates to a heat treatment method of a plated steel sheet for hot stamping in which the plated steel sheet is preliminarily heated before hot stamping in which the plated steel sheet is rapidly cooled in a stamping die and quenched. Background technique [0002] There is a tendency for both high strength and light weight to be particularly required for the components of the running part of the automobile and various reinforcement components. Generally, when the strength of the steel sheet used is increased, there is a problem that scratches and fractures occur during forming, or the shape of the formed product is unstable due to a large number of springback phenomena of the steel sheet. [0003] To solve this problem, as shown in Patent Documents 1 and 2, there is hot stamping as one of techniques for manufacturing high-strength steel parts. According to this technique, steels to be formed selected from hardenable steel grades, ...

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Problems solved by technology

[0013] In addition, in the case of hot stamping an aluminized steel sheet, an aluminum oxide film is formed on the surface. Even if it is not like the formation of an iron oxide film, there is still a problem of coating adhesion, so it is impossible to obtain an outer panel that meets the requirements of automobiles. Strict coating adhesion required for components such as walking parts, etc.

[0014] In addition, when using a galvanized steel sheet, when the oxygen concentration is 0% by volume in the preheated galvanized steel sheet before hot stamping, the zinc oxide layer is not formed on the uppermost layer, so when it is taken out from the heating furnace into the atmosphere, The problem of rapid oxidation of the steel plate will occur

In addition, depending on the heating conditions, the zinc oxide layer becomes too thick, and there may be a problem with coating adhesion.

[0015] In addition, even under the conditions of the heating atmosphere gas where the zinc oxide layer is formed, due to the method of supporting the steel plate in the furnace, the formation of the two layers of the steel plate in the part of the steel plate that is in contact with the supporting member is not sufficient, and defects in appearance occur. Uniformity, so the coating adhesion and corrosion resistance of this part may decrease, it is necessary to remove the contact part with the support member in advance, and use the remaining part as a plated steel plate after heat treatment

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