Hot-rolled galvanized steel sheet having excellent galling resistance, formability and sealer-adhesion property and method for manufacturing same

Patent metadata

Field	Value
Publication number	US-10982309-B2
Application number	US-201716327426-A
Country	US
Kind code	B2
Filing date	Aug 22, 2017
Priority date	Aug 22, 2016
Publication date	Apr 20, 2021
Grant date	Apr 20, 2021

Abstract

Disclosed are a hot-rolled galvanized steel sheet having excellent galling resistance and formability, and a method for manufacturing the same. The hot-rolled galvanized steel sheet, includes: a base steel; and a hot-rolled galvanizing layer formed on the surface of the base steel, wherein the hot-rolled galvanizing layer provides a hot-rolled galvanized steel sheet having a Mn crystallite having a size of 10 μm or less between the resin dendrites of zinc that form sequins.

First claim

The invention claimed is:

1. A method for manufacturing a hot-rolled galvanized steel sheet, the method comprising:
a plating layer forming step of depositing a steel sheet in a hot-rolled galvanizing solution, containing 0.1 to 0.8 weight percentage (wt %) of aluminum (Al), 0.05 to 1 wt % of manganese (Mn), with a remainder of zinc (Zn) and inevitable impurities, and taking out the deposited steel sheet therefrom to form a plating layer that forms a hot-rolled galvanizing layer;
a primary cooling step of cooling the steel sheet, on which the hot-rolled galvanizing layer is formed, at a cooling rate of −10 degrees Celsius per second (° C./s) until a temperature of the steel sheet reaches 420° C.;
a secondary cooling step of cooling the steel sheet at a cooling rate of −8° C./s until the temperature of the steel sheet reaches 418° C. from 420° C.; and
a tertiary cooling step of cooling the steel sheet at a steel sheet temperature of 418° C. or less at a cooling rate of −10° C./s or more to form the hot-rolled galvanizing layer.

2. The method of claim 1 , wherein the hot-rolled galvanizing solution has a temperature of 440 to 470° C.

3. The method of claim 1 , further comprising:
a wiping step of blowing nitrogen or air to the steel sheet, taken out from the hot-rolled galvanizing solution, to remove excessive molten zinc adhered to the steel sheet while cooling the steel sheet.

4. The method of claim 1 , wherein the secondary cooling step is performed by blowing a gas having a temperature ranging from 100° C. to 400° C.

5. The method of claim 4 , wherein the gas is air or a nitrogen gas.

6. The method of claim 1 , further comprising:
cleaning a surface of the steel sheet to remove foreign substances before the plating layer forming step;
annealing the steel sheet in a nitrogen-hydrogen reducing atmosphere at an A3 transformation temperature or higher; and
cooling the annealed steel sheet before being deposited in the hot-rolled galvanizing solution.

7. The method of claim 1 , further comprising:
temper-rolling a surface of a solidified hot-rolled galvanizing layer after the tertiary cooling step.

8. The method of claim 1 , wherein the hot-rolled galvanizing solution contains 0.15 to 0.5 wt % of Al, 0.05 to 0.6 wt % of Mn, and a remainder of Zn, and a total content of elements excluding Zn is 1 wt % or less.

Assignees

• Posco

Inventors

• Kim Sang-Heon
• Hwang Hyeon-Seok
• Lee Suk-Kyu
• Jeon Sun-Ho
• Song Yon-Kyun
• Yoo Bong-Hwan

Classifications

• C23C2/18

  Removing excess of molten coatings from elongated material · CPC title

• C21D9/46 Primary

  for sheet metals · CPC title

• C22C18/04

  with aluminium as the next major constituent · CPC title

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title

• C23C2/20

  Strips; Plates · CPC title