High strength galvanized steel sheet excellent in terms of coating adhesiveness and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-9677163-B2
Application number	US-201214124090-A
Country	US
Kind code	B2
Filing date	Jun 6, 2012
Priority date	Jun 7, 2011
Publication date	Jun 13, 2017
Grant date	Jun 13, 2017

Abstract

A high strength galvanized steel sheet excellent in coating adhesiveness is made from a base material that is a high strength steel sheet containing Si, Mn, and Cr. A method includes performing an oxidation treatment on steel containing Si, Mn, and Cr in an oxidation furnace under the condition that a selected exit temperature T, reduction annealing and a galvanizing treatment, or optionally, further an alloying treatment under conditions that heating is performed at a temperature of 460° C. or higher and 600° C. or lower for an alloying treatment time of 10 seconds or more and 60 seconds or less.

First claim

The invention claimed is:

1. A method of manufacturing a high strength galvanized steel sheet excellent in terms of coating adhesiveness comprising:
performing an oxidation treatment on steel containing Si, Mn, and Cr in an oxidation furnace under a condition that an exit temperature T satisfies expressions below,
performing reduction annealing, and
performing a galvanizing treatment without performing an alloying treatment:
A=0.015T−7.6 (T≧507° C.),

A=0 (T<507° C.),

B=0.0063T−2.8 (T≧445° C.),

B=0 (T<445° C.),

[Si]+A×[Cr]≦B,

where [Si]: Si content of the steel by mass %, and
[Cr]: Cr content of the steel by mass %,

wherein the oxidation furnace includes three or more zones in which atmospheres can be individually controlled and which are called oxidation furnace 1 , oxidation furnace 2 , oxidation furnace 3 and so on in ascending order of distance from the entrance of the furnace, in which atmospheres of the oxidation furnace 1 and the oxidation furnace 3 have an oxygen concentration of less than 1000 vol.ppm and the balance being N 2 , CO, CO 2 , H 2 O and inevitable impurities and the atmosphere of the oxidation furnace 2 has an oxygen concentration of 1000 vol.ppm or more and the balance being N 2 , CO, CO 2 , H 2 O and inevitable impurities.

2. The method according to claim 1 , wherein an exit temperature T 2 of the oxidation furnace 2 is (the exit temperature T−50)° C. or higher.

3. The method according to claim 2 , wherein an exit temperature T 1 of the oxidation furnace 1 is (the exit temperature T−350)° C. or higher and lower than (the exit temperature T−250)° C.

4. The method according to claim 1 , wherein an exit temperature T 1 of the oxidation furnace 1 is (the exit temperature T−350)° C. or higher and lower than (the exit temperature T−250)° C.

5. The method according to claim 1 , wherein the steel has a chemical composition containing C: 0.01 mass % or more and 0.20 mass % or less, Si: 0.5 mass % or more and 2.0 mass % or less, Mn: 1.0 mass % or more and 3.0 mass % or less, Cr: 0.01 mass % or more and 0.4 mass % or less and the balance being Fe and inevitable impurities.

6. A method of manufacturing a high strength galvanized steel sheet excellent in terms of coating adhesiveness comprising:
performing an oxidation treatment on steel containing Si, Mn, and Cr in an oxidation furnace under a condition that an exit temperature T satisfies expressions below,
performing reduction annealing,
performing a galvanizing treatment, and
performing an alloying treatment under conditions that heating is performed at a temperature of 460° C. or higher and 600° C. or lower for an alloying treatment time of 10seconds or more and 60 seconds or less:
A=0.015T−7.6 (T≧507° C.),

A=0 (T<507° C.),

B=0.0063T−2.8 (T≧445° C.),

B=0 (T<445° C.),

[Si]+A×[Cr]≦B,

where [Si]: Si content of the steel by mass %, and
[Cr]: Cr content of the steel by mass %%,

wherein the oxidation furnace includes three or more zones in which atmospheres can be individually controlled and which are called oxidation furnace 1 , oxidation furnace 2 , oxidation furnace 3 and so on in ascending order of distance from the entrance of the furnace, in which atmospheres of the oxidation furnace 1 and the oxidation furnace 3 have an oxygen concentration of less than 1000 vol.ppm and the balance being N 2 , CO, CO 2 , H 2 O and inevitable impurities and the atmosphere of the oxidation furnace 2 has an oxygen concentration of 1000 vol.ppm or more and the balance being N 2 , CO, CO 2 , H 2 O and inevitable impurities.

7. The method according to claim 6 , wherein an exit temperature T further satisfies:
T≦−80[Mn]−75[Si]+1030,

where [Si]: Si content of the steel by mass %, and
[Mn]: Mn content of the steel by mass %.

8. The method for manufacturing a high strength galvanized steel sheet excellent in terms of coating adhesiveness according to claim 6 ,
wherein the steel has a chemical composition containing C: 0.01 mass % or more and 0.20mass % or less, Si: 0.5 mass % or more and 2.0 mass % or less, Mn: 1.0 mass % or more and 3.0mass % or less, Cr: 0.01 mass % or more and 0.4 mass % or less and the balance being Fe and inevitable impurities.

9. The method according to claim 6 , wherein an exit temperature T 2 of the oxidation furnace 2 is (the exit temperature T−50)° C. or higher.

10. The method according to claim 6 , wherein an exit temperature T 2 of the oxidation furnace 1 is (the exit temperature T−350)° C. or higher and lower than (the exit temperature T−250)° C.

Assignees

• Makimizu Yoichi
• Suzuki Yoshitsugu
• Nagano Hideki
• Kaneko Shinjiro
• Jfe Steel Corp

Inventors

• Makimizu Yoichi
• Suzuki Yoshitsugu
• Nagano Hideki
• Kaneko Shinjiro

Classifications

• C23C2/06

  Zinc or cadmium or alloys based thereon · CPC title

• C22C38/38

  with more than 1.5% by weight of manganese · CPC title

• C22C38/34

  with more than 1.5% by weight of silicon · CPC title

• C21D9/48

  deep-drawing sheets · CPC title

• C21D8/0478

  involving a particular surface treatment (C21D8/0494 takes precedence) · CPC title