Hot-stamped steel

Patent metadata

Field	Value
Publication number	US-9976196-B2
Application number	US-201515129775-A
Country	US
Kind code	B2
Filing date	Mar 31, 2015
Priority date	Mar 31, 2014
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

Hot-stamped steel includes: a steel base metal including a tempered portion having hardness corresponding to 85% or less of the highest quenching hardness defined as a Vickers hardness at a depth position spaced away from a surface layer by ¼ times a sheet thickness in a case of performing water quenching after heating at a temperature equal to or higher than an A c3 point and retention for 30 minutes; and a Zn coating layer formed on the tempered portion of the base metal. The Zn coating layer includes a solid-solution layer including a solid-solution phase containing Fe and Zn that is solid-soluted in Fe, and a lamella layer including solid-solution phase and a capital gamma phase. In the Zn coating layer, an area ratio of the lamella layer is 30 to 100% and an area ratio of the solid-solution layer is 0 to 70%.

First claim

What is claimed is:

1. A hot-stamped steel comprising:
a base metal that is a steel sheet where a part of the steel sheet is a tempered portion or an entirely of the steel sheet is a tempered portion, said tempered portion having a hardness corresponding to 85% or less of the highest quenching hardness, the highest quenching hardness being defined as a Vickers hardness at a depth position spaced away from a surface layer by ¼ times a sheet thickness in a case of performing water quenching after heating to a temperature equal to or higher than an A c3 point and retaining for 30 minutes; and
a Zn coating layer that is formed on the tempered portion of the base metal,
wherein the Zn coating layer includes
a solid-solution layer including a solid-solution phase that contains Fe and Zn that is solid-soluted in Fe, and
a lamella layer that includes the solid-solution phase and a capital gamma phase, and

wherein in the Zn coating layer, an area ratio of the lamella layer in a cross-section perpendicular to a rolling direction is 30 to 100% and an area ratio of the solid-solution layer is 0 to 70%.

2. The hot-stamped steel according to claim 1 ,
wherein the area ratio of the lamella layer in the Zn coating layer is 80% or more.

3. The hot-stamped steel according to claim 1 or 2 ,
wherein a Vickers hardness with a load of 10 kgf of the tempered portion is 180 Hv to 450 Hv.

4. The hot-stamped steel according to claim 1 or 2 ,
wherein a hardness of the tempered portion is 65% or less of the highest quenching hardness.

5. The hot-stamped steel according to claim 1 or 2 ,
wherein the hot-stamped steel is produced by heating to the A c3 point or higher, working and quenching simultaneously through pressing by using a die, and then tempering at 500° C. or more and less than 700° C.

6. The hot-stamped steel according to claim 1 or 2 ,
wherein a part of the base metal is the tempered portion.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Sengoku Akihiro
• Takebayashi Hiroshi

Classifications

• Y10T428/12792

  Zn-base component · CPC title

• C21D9/46 Primary

  for sheet metals · CPC title

• B32B15/013

  one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium · CPC title

• C22C38/001

  containing N · CPC title

• C23C2/06

  Zinc or cadmium or alloys based thereon · CPC title