US-20260124660-A1 - PLATED STEEL SHEET FOR HOT PRESS FORMING, AND METHOD OF MANUFACTURING THE SAME

Abstract

A plated steel sheet for hot press forming with improved hydrogen delayed fracture properties is disclosed. The disclosed plated steel sheet includes a base steel sheet, and a plating layer formed on a surface of the base steel sheet and including, by weight, Si: 5.0 to 15.0%, Zn: 10.0 to 30.0%, Fe: 4.0 to 12.0%, and the remainder including Al and unavoidable impurities.

Inventors

• Hyeon-Seok HWANG
• Kkochnim Oh

Assignees

• POSCO CO., LTD

Dates

Publication Date

20260507

Application Date

20260106

Priority Date

20201218

Claims (4)

1. 1 . A method of manufacturing a hot press formed product, comprising: providing a base steel sheet and preparing a plated steel sheet by immersing the base steel sheet in a plating solution including, by weight, Si: 5.0 to 15.0%, Zn: 10.0 to 30.0%, and the remainder including Al and unavoidable impurities; heating the plated steel sheet to a temperature greater than 800° C. and less than 1,100° C.; hot press forming the plated steel sheet; and cooling the hot press-formed plated steel sheet.
2. 2 . The method of claim 1 , wherein the heating of the plated steel sheet is performed for more than 2 minutes and less than 15 minutes.
3. 3 . The method of claim 1 , wherein the heating of the plated steel sheet is performed at a rate of 2° C./sec to 15° C./sec.
4. 4 . The method of claim 1 , wherein in the cooling of the plated steel sheet formed by the hot pressing, the cooling is performed at a rate of 15° C./sec or more in a temperature range of 700° C. to 350° C.

Description

CROSS-REFERENCE OF RELATED APPLICATIONS This application is a divisional application of U.S. patent application Ser. No. 18/268,138, filed on Jun. 16, 2023, which is the U.S. National Phase under 35 U.S.C. § 371 of International Patent Application No. PCT/KR2021/019275, filed on Dec. 17, 2021 which claims priority to and the benefit of Korean Application No. 10-2020-0178907 filed on Dec. 18, 2020, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a plated steel sheet for hot press forming and a method of manufacturing the same, and more particularly, to a plated steel sheet for hot press forming with improved hydrogen delayed fracture properties by optimizing component conditions and heat treatment conditions, and a method of manufacturing the same. BACKGROUND ART Recently, as the demand for safety and fuel efficiency has increased, the use of high strength steel for weight reduction of automobiles is increasing, but the high strength steel has a problem in that it is difficult to form a product having a complex and precise shape as material fracture occurs during processing or spring back occurs after processing. Hot press forming (HPF) is a method for solving these problems, and its application is recently expanding. A hot pressed steel sheet is easy to form as it is hot-worked in a state where it is usually heated to 800 to 950° C., and has the advantage of increasing the strength of molded articles when quenching through a mold. However, when a steel material is heated to a high temperature, the surface of the steel material is oxidized, so there is a problem in that a process of removing the product on the surface of the steel sheet must be added after press forming. For this purpose, conventionally, a method of introducing an aluminum plating layer or zinc plating on the surface of the steel sheet as a material for hot press forming has been proposed. However, the use of a steel sheet plated with high strength steel is limited due to delayed fracture caused by hydrogen. Specifically, delayed fracture is a phenomenon in which hydrogen diffuses into steel to reduce the ductility and toughness of a steel material after molding of a part, and fracture occurs without plastic deformation. In particular, in an aluminum-plated steel sheet using high strength steel as a base, a hydrogen diffusion coefficient of an Al and Al—Fe-based interface alloy layer is very low, and a problem of delayed fracture is more serious than that of a steel sheet without a metal coating. Therefore, it is required to develop a plated steel sheet for hot press forming that can be applied to automobile parts by securing not only strength but also improved hydrogen delayed fracture properties. DISCLOSURE Technical Problem Embodiments of the present invention are intended to provide a plated steel sheet for hot press forming with improved hydrogen delayed fracture properties and a method of manufacturing the same. Technical Solution A plated steel sheet for hot press forming according to an embodiment of the present invention includes a base steel sheet, and a plating layer formed on a surface of the base steel sheet and including, by weight, Si: 5.0 to 15.0%, Zn: 10.0 to 30.0%, Fe: 4.0 to 12.0%, and the remainder including Al and unavoidable impurities. In addition, according to one embodiment of the present invention, the base steel sheet may contain, by weight, C: 0.1 to 0.4%, Mn: 0.5 to 3.0%, Si: 0.1 to 0.8%, B: 0.01% or less (excluding 0), Ti: 0.1% or less (excluding 0), and the remainder including Fe and other unavoidable impurities. Further, according to one embodiment of the present invention, the plating layer attached to the surface of the base steel sheet may have an attachment amount of 40 to 120 g/m2. In addition, according to one embodiment of the present invention, the thickness of the plating layer may be 5 to 40 μm. In addition, according to one embodiment of the present invention, an Al—Fe-based interface alloy layer formed between the base steel sheet and the plating layer and including, by weight, Al: 30.0 to 60.0% and Si: 5.0 to 20.0%, may be provided. In addition, according to one embodiment of the present invention, the plating layer may contain silicon crystals having a silicon concentration of 60% or more, a zinc concentration of less than 20%, and a long axis length of 1 μm or more. A method of manufacturing a plated steel sheet for hot press forming according to another embodiment of the present invention includes: providing a base steel sheet and preparing a plated steel sheet by immersing the base steel sheet in a plating solution including, by weight, Si: 5.0 to 15.0%, Zn: 10.0 to 30.0%, and the remainder including Al and unavoidable impurities; heating the plated steel sheet to a temperature greater than 800° C. and less than 1,100° C.; hot press forming the plated steel sheet; and cooling the hot press-formed plated steel sheet. In additio