Hot press formed article having excellent delamination resistance and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-10640840-B2
Application number	US-201615250022-A
Country	US
Kind code	B2
Filing date	Aug 29, 2016
Priority date	Dec 24, 2014
Publication date	May 5, 2020
Grant date	May 5, 2020

Abstract

An HPF molding member having a melted aluminum plating layer formed on the surface of a base steel sheet and excellent delamination resistance. The base steel sheet comprises: 0.18-0.25% by weight of C; 0.1-1.0% by weight of Si; 0.9-1.5% by weight of Mn; 0.03% by weight or less of P; 0.01% by weight or less of S; 0.01-0.05% by weight of Al; 0.05-0.5% by weight of Cr; 0.01-0.05% by weight of Ti; 0.001-0.005% by weight of B; 0.009% by weight or less of N; and the balance Fe and other impurities. The plating layer consists of a soft diffusion layer and a hard alloy layer, the hard alloy layer having a tau layer irregularly and non-continuously dispersed and distributed on the inside thereof at 10% or more of the entire area fraction. The difference in hardness between the alloy layer and the diffusion layer is 400 (Hv) or less.

First claim

What is claimed are:

1. A hot press formed (HPF) article having excellent delamination resistance, a hot dip aluminum plating layer being formed on a surface of a substrate steel sheet, wherein the substrate steel sheet includes, in % by weight, C: 0.18% to 0.25%, Si: 0.1% to 1.0%, Mn: 0.9% to 1.5%, P: 0.03% or less, S: 0.01% or less, Al: 0.01% to 0.05%, Cr: 0.05% to 0.5%, Ti: 0.01% to 0.05%, B: 0.001% to 0.005, N: 0.009% or less, and a remainder of Fe and other impurities;
the plating layer is formed to have a soft diffusion layer and a hard alloy layer;
the alloy layer comprises Fe 2 Al 5 matrix phase and a tau phase comprised of Fe—Al—Si based alloy phase;
the tau phase is irregularly and discontinuously dispersed and distributed inside the alloy layer in an amount of 10% or greater based on the total area fraction so that a difference in hardnesses between the alloy layer and the diffusion layer is 400 (Hv) or less.

2. The hot press formed (HPF) article having excellent delamination resistance of claim 1 , wherein the substrate steel sheet is a cold rolled steel sheet or a hot rolled steel sheet.

3. The hot press formed (HPF) article having excellent delamination resistance of claim 1 , wherein the tau phase is present in a range of 10% by weight to 20% by weight inside the alloy layer.

4. The hot press formed (HPF) article having excellent delamination resistance of claim 1 , wherein the tau phase has an aspect ratio in a range of 1 to 4.

5. The hot press formed (HPF) article having excellent delamination resistance of claim 1 , wherein the tau phase having a size of 5 μm or less occupies an area of 50% or greater with respect to the total tau phase fraction.

6. The hot press formed (HPF) article having excellent delamination resistance of claim 1 , wherein the substrate steel sheet further includes Mo+W in an amount of 0.001% to 0.5%.

7. The hot press formed (HPF) article having excellent delamination resistance of claim 1 , wherein the substrate steel sheet further includes a sum of one or more types of Nb, Zr or V in a range of 0.001% to 0.4%.

8. The hot press formed (HPF) article having excellent delamination resistance of claim 1 , wherein the substrate steel sheet further includes Cu+Ni in a range of 0.005% to 2.0%.

9. The hot press formed (HPF) article having excellent delamination resistance of claim 1 , wherein the substrate steel sheet further includes one or more types of Sb, Sn or Bi in an amount of 0.03% or less.

10. A method for manufacturing a hot press formed (HPF) article having excellent delamination resistance, the method comprising:
preparing a steel sheet including, in % by weight, C: 0.18% to 0.25%, Si: 0.1% to 1.0%, Mn: 0.9% to 1.5%, P: 0.03% or less, S: 0.01% or less, Al: 0.01% to 0.05%, Cr: 0.05% to 0.5%, Ti: 0.01% to 0.05%, B: 0.001% to 0.005, N: 0.009% or less, and a remainder of Fe and other impurities;
hot dip aluminum plating the steel sheet by, after heating the steel sheet to a temperature of 550° C. to 850° C., immersing the steel sheet in a hot dip aluminum plating bath maintained at a temperature of 640° C. to 680° C. and composed of, in % by weight, Si: 7% to 13%, Fe: less than 3%, and the remainder of Al and other unavoidable impurities;
skin pass milling (SPM) the hot dip aluminum plating steel sheet with an elongation of 0.5% to 3% after cooling the hot dip galvanized steel sheet;
alloying a hot dip aluminum plating layer on a surface of the hot dip aluminum plated steel sheet by heating the hot dip aluminum plated steel sheet to a temperature of 850° C. to 950° C. and maintaining the temperature for a certain period of time; and
manufacturing a hot press formed (HPF) product by rapidly cooling the alloyed hot dip aluminum plated steel sheet to a temperature of 300° C. or lower while hot press forming the alloyed hot dip aluminum plated steel sheet.

11. The method for manufacturing a hot press formed (HPF) article having excellent delamination resistance of claim 10 , wherein the alloyed hot dip aluminum plating layer is formed to have a soft diffusion layer and a hard alloy layer;
the alloy layer comprises Fe 2 Al 5 matrix phase and a tau phase comprised of Fe—Al—Si based alloy phase;
a tau phases is irregularly and discontinuously dispersed and distributed inside the alloy layer in an amount of 10% or greater based on the total area fraction.

12. The method for manufacturing a hot press formed (HPF) article having excellent delamination resistance of claim 11 , wherein the tau phase is present in a range of 10% by area to 20% by area inside the alloy layer.

13. The method for manufacturing a hot press formed (HPF) article having excellent delamination resistance of claim 11 , wherein the tau phase has an aspect ratio in a range of 1 to 4.

14. The method for manufacturing a hot press formed (HPF) article having excellent delamination resistance of claim 11 , wherein the tau phase having a size of 5 μm or less occupies an area of 50% or greater with respect to the total tau phase fraction.

15. The method for manufacturing a hot press formed (HPF) article having excellent delamination resistance of claim 10 , wherein the steel sheet is a cold rolled steel sheet or a hot rolled steel sheet.

16. The method for manufacturing a hot press formed (HPF) article having excellent delamination resistance of claim 10 , wherein the substrate steel sheet further includes Mo+W in an amount of 0.001% to 0.5%.

17. The method for manufacturing a hot press formed (HPF) article having excellent delamination resistance of claim 10 , wherein the substrate steel sheet further includes a sum of one or more types of Nb, Zr or V in a range of 0.001% to 0.4%.

18. The method for manufacturing a hot press formed (HPF) article having excellent delamination resistance of claim 10 , wherein the substrate steel sheet further includes Cu+Ni in a range of 0.005% to 2.0%.

19. The method for manufacturing a hot press formed (HPF) article having excellent delamination resistance of claim 10 , wherein the substrate steel sheet further includes one or more types of Sb, Sn or Bi in an amount of 0.03% or less.

Assignees

• Posco

Inventors

• Kim Heung-Yun
• Sohn Il-Ryoung
• Bae Dae-Chul

Classifications

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D8/0226

  Hot rolling · CPC title

• C21D9/46 Primary

  for sheet metals · CPC title

• C22C38/001

  containing N · CPC title