# US 2022/0033929 A1 · Hot press forming member having excellent resistance to hydrogen embrittlement, and method for manufacturing same

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- Number: US 2022/0033929 A1
- Document ID: US20220033929A1
- Status: Published application
- Kind: A1
- Application number: 17/298,782
- Filed: 2019-12-02
- Published: 2022-02-03
- Earliest claimed: 2018-12-03
- Assignees: Posco
- Applicants: Posco
- Inventors: Seong-Woo Kim; Jin-Keun Oh; Sang-Heon Kim; Sang-Bin Han
- Web page: https://patentgrep.com/patent/US20220033929A1

## CPC

- C21D 9/48: deep-drawing sheets
- B32B 15/012: {one layer being formed of an iron alloy or steel, another layer being formed of aluminium or an aluminium alloy}
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 1/26: Methods of annealing
- C21D 1/76: Adjusting the composition of the atmosphere
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/04: to produce plates or strips for drawing, e.g. for deep-drawing
- C21D 8/0421: {characterised by the working steps}
- C21D 8/0447: {characterised by the heat treatment}
- C21D 8/0452: {with application of tension}
- C21D 8/0478: {involving a particular surface treatment (C21D8/0494 takes precedence)}
- C21D 9/0043: {Muffle furnaces; Retort furnaces}
- C22C 38/001: {containing N}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/14: containing titanium or zirconium
- C22C 38/18: containing chromium
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- C22C 38/38: with more than 1.5% by weight of manganese
- C23C 2/02: Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence)
- C23C 2/12: Aluminium or alloys based thereon
- C23C 2/28: Thermal after-treatment, e.g. treatment in oil bath
- C23C 2/29: {Cooling or quenching}
- C23C 2/40: Plates; Strips
- C23C 28/02: only coatings {only including layers} of metallic material
- C23C 28/021: {including at least one metal alloy layer}
- C23C 28/023: {only coatings of metal elements only}
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)

## Abstract

The present invention pertains to a hot press forming member having excellent resistance to hydrogen embrittlement, and a method for manufacturing same. An aspect of the present invention provides a hot press forming member having excellent resistance to hydrogen embrittlement, the hot press forming member comprising a base steel plate and an alloy-plated layer formed on the surface of the base steel plate, wherein the alloy-plated layer contains pores such that pores having a size of 5 μm or less constitute 3-30% of the surface area of the alloy-plated layer as viewed in a cross-section taken in the thickness direction of the member.

## Claims

### Claim 1

A hot press formed member having excellent resistance to hydrogen embrittlement, the hot press formed member comprising:
a base steel sheet and an alloy-plated layer formed on a surface of the base steel sheet,
wherein the alloy-plated layer contains pores such that pores having a size of 5 μm or less accounts for 3 to 30% of a surface area of the alloy-plated layer, when viewed in a cross-section taken in a thickness direction of the hot press formed member.

### Claim 2

A hot press formed member having excellent resistance to hydrogen embrittlement, the hot press formed member comprising:
a base steel sheet and an alloy-plated layer formed on a surface of the base steel sheet,
wherein the alloy-plated layer contains pores such that number density, obtained by dividing an area of the alloy-plated layer by the number of pores having a size of 5 μm or less, is 5×103 to 2×106 number/mm2, when viewed in a cross-section taken in a thickness direction of the hot press formed member.

### Claim 3

The hot press formed member of 1, wherein pores, accounting for 70% or more of total pores having a size of 5 μm or less based on an area, are present in a surface layer portion of the alloy-plated layer.

### Claim 4 (depends on 2)

The hot press formed member of claim 2, wherein pores, accounting for 70% or more of total pores having a size of 5 μm or less based on an area, are present in a surface layer portion of the alloy-plated layer.

### Claim 5 (depends on 2)

The hot press formed member of claim 2, wherein the alloy-plated layer contains pores such that a ratio of an area occupied by pores having a size of 5 μm or less to an area of the alloy-plated layer is 3 to 30%, when viewed in a cross-section taken in a thickness direction of the hot press formed member.

### Claim 6 (depends on 1)

The hot press formed member of claim 1, wherein the base steel sheet comprises, by weight, 0.04 to 0.5% of carbon (C), 0.01 to 2% of silicon (Si), 0.1 to 5% of manganese (Mn), 0.001 to 0.05% of phosphorus (P), 0.0001 to 0.02% of sulfur (S), 0.001 to 1% of aluminum (Al), 0.001 to 0.02% of nitrogen (N), and a balance of iron (Fe) and other impurities.

### Claim 7 (depends on 6)

The hot press formed member of claim 6, wherein the base steel sheet further comprises, by weight, at least one of 0.0001 to 0.01% of boron (B), 0.01 to 1% of chromium (Cr), and 0.001 to 0.2% of titanium (Ti).

### Claim 8

A method of manufacturing a hot press formed member having excellent resistance to hydrogen embrittlement, the method comprising:
performing aluminum plating on a surface of a base steel sheet and coiling the base steel sheet to obtain an aluminum-plated steel sheet;
annealing the aluminum-plated steel sheet to obtain an aluminum-iron alloy-plated steel sheet; and
heat treating the aluminum-iron alloy-plated steel sheet for hot press forming in a temperature range of Ac3 to 950° C. for 1 to 15 minutes and then hot-press forming the heat treated aluminum-iron alloy-plated steel sheet for hot press forming,
wherein an amount of the aluminum plating is 30 to 200 g/m2 per one side,
a cooling rate to 250° C. after the aluminum plating is 20° C./sec or less,
coiling tension during the coiling is 0.5 to 5 kg/mm2,
the annealing is performed in a batch annealing furnace, containing hydrogen in a volume fraction of 50% or more, at a temperature range of 550 to 750° C. for 30 minutes to 50 hours,
an average temperature increase rate is 10 to 100° C./h when the steel sheet is heated to the heating temperature from room temperature, and an average temperature increase rate in a section of 400 to 500° C. is 1 to 15° C./h, during the annealing, and
a difference between an atmospheric temperature in the batch annealing furnace and a temperature of the steel sheet is 5 to 80° C.

### Claim 9 (depends on 8)

The method of claim 8, wherein the base steel sheet comprises, by weight, 0.04 to 0.5% of carbon (C), 0.01 to 2% of silicon (Si), 0.1 to 5% of manganese (Mn), 0.001 to 0.05% of phosphorus (P), 0.0001 to 0.02% of sulfur (S), 0.001 to 1% of aluminum (Al), 0.001 to 0.02% of nitrogen (N), and a balance of iron (Fe) and other impurities.

### Claim 10 (depends on 9)

The method of claim 9, wherein the base steel sheet further comprises, by weight, at least one of 0.0001 to 0.01% of boron (B), 0.01 to 1% of chromium (Cr), and 0.001 to 0.2% of titanium (Ti).

### Claim 11 (depends on 2)

The hot press formed member of claim 2, wherein the base steel sheet comprises, by weight, 0.04 to 0.5% of carbon (C), 0.01 to 2% of silicon (Si), 0.1 to 5% of manganese (Mn), 0.001 to 0.05% of phosphorus (P), 0.0001 to 0.02% of sulfur (S), 0.001 to 1% of aluminum (Al), 0.001 to 0.02% of nitrogen (N), and a balance of iron (Fe) and other impurities.

### Claim 12 (depends on 11)

The hot press formed member of claim 11, wherein the base steel sheet further comprises, by weight, at least one of 0.0001 to 0.01% of boron (B), 0.01 to 1% of chromium (Cr), and 0.001 to 0.2% of titanium (Ti).