HOT-PRESS FORMED MEMBER HAVING EXCELLENT RESISTANCE TO HYDROGEN BRITTLEMENT AND METHOD FOR MANUFACTURING THE SAME

Abstract

The present invention relates to a hot-formed member having excellent resistance to hydrogen embrittlement, and to a method for manufacturing the same. One aspect of the present invention provides a hot-formed member having excellent resistance to hydrogen embrittlement, the hot-formed 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 the pores having a size of 5 µm or less constitute 3-30% of the surface area of ​​the alloy-plated layer as visualized in a cross-section taken in the thickness direction of the member.

Claims

1. A hot-pressed member having excellent resistance to hydrogen embrittlement, the hot-pressed member characterized in that it comprises: 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 the pores having a size of 5 pm or less account 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-pressed member.

2. A hot-pressed member having excellent resistance to hydrogen embrittlement, the hot-pressed member characterized in that it comprises: 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 the number density, obtained by dividing an area of ​​the alloy-plated layer by the number of pores having a size of 5 pm or less, is from 5 x 10³ to 2 x 10⁶ number / mm², when viewed in a cross-section taken in a thickness direction of the hot-pressed member. znaecn / Lznz / q / YiAi 3. The hot-pressed member according to claim 1, characterized in that the pores, taking into account 70% or more of the total pores having a size of 5 pm or less on an area basis, are present in a surface layer portion of the alloy-plated layer.

4. The hot-pressed member according to claim 2, characterized in that the pores, taking into account 70% or more of the total pores having a size of 5 pm or less on an area basis, are present in a surface layer portion of the alloy-plated layer.

5. The hot-pressed member according to claim 2, characterized in that the alloy-plated layer contains pores such that the ratio of an area occupied by pores having a size of 5 pm 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-pressed member.

6. The hot-pressed member according to any one of claims 1 to 5, characterized in that the base steel sheet comprises, by weight, 0.04 to 0.5% carbon (C), 0.01 to 2% silicon (Si), 0.1 to 5% manganese (Mn), 0.001 to 0.05% phosphorus (P), 0.0001 to 0.02% sulfur (S), 0.001 to 1% aluminum (Al), 0.001 to 0.02% nitrogen (N), and a remainder of iron (Fe) and other impurities.

7. The hot-pressed member according to claim 6, characterized in that the base steel sheet further comprises, by weight, at least 0.0001 to 0.01% boron (B), 0.01 to 1% chromium (Cr), and 0.001 to 0.2% titanium (Ti).

8. A method for manufacturing a hot-press formed member having excellent resistance to hydrogen embrittlement, the method characterized in that it comprises: performing aluminum plating on a surface of a base steel sheet and rolling 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 the amount of aluminum plating is 30 to 200 g / m2 on one side, and the cooling rate at 250°C after aluminum plating is 20°C / sec or less.The winding tension during winding is 0.5 to 5 kg / mm2, annealing is carried out in a batch annealing furnace, which contains hydrogen in a volume fraction of 50% or more, in 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 ambient temperature, and an average temperature increase rate in a section of 400 to 500°C is 1 to 15°C / h, during 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.

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

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