Hot-stamped part and method of manufacturing the same

Patent metadata

Field	Value
Publication number	US-2016145704-A1
Application number	US-201414899267-A
Country	US
Kind code	A1
Filing date	Sep 12, 2014
Priority date	Sep 18, 2013
Publication date	May 26, 2016
Grant date	—

Abstract

A hot-stamped part includes a chemical composition represented by, in mass %: C: 0.120% to 0.400%; Si: 0.005% to 2.000%; Mn or Cr, or both thereof: 1.00% to 3.00% in total; Al: 0.005% to 0.100%; B: 0.0003% to 0.0020%; P: not more than 0.030%; S: not more than 0.0100%; O: not more than 0.0070%; N: not more than 0.0070%; Ti: 0% to 0.100%; Nb: 0% to 0.100%; V: 0% to 0.100%; Ni: 0% to 2.00%; Cu: 0% to 2.00%; Mo: 0% to 0.50%; Ca or REM, or both thereof: 0% to 0.0300% in total; and the balance: Fe and impurities, and a structure represented by: an area fraction of martensite or bainite, or both thereof: not less than 95% in total; a coverage factor of prior austenite grain boundary by iron-based carbides: not more than 80%; and a number density of iron-based carbides in prior austenite grains: not less than 45/μm 2 .

First claim

1 . A hot-stamped part comprising:
a chemical composition represented by, in mass %:
C: 0.120% to 0.400%;
Si: 0.005% to 2.000%;
Mn or Cr, or both thereof: 1.00% to 3.00% in total;
Al: 0.005% to 0.100%;
B: 0.0003% to 0.0020%;
P: not more than 0.030%;
S: not more than 0.0100%;
O: not more than 0.0070%;
N: not more than 0.0070%;
Ti: 0% to 0.100%;
Nb: 0% to 0.100%;
V: 0% to 0.100%;
Ni: 0% to 2.00%;
Cu: 0% to 2.00%;
Mo: 0% to 0.50%;
Ca or REM, or both thereof: 0% to 0.0300% in total; and
the balance: Fe and impurities; and
a structure represented by:
an area fraction of martensite or bainite, or both thereof: not less than 95% in total;
a coverage factor of prior austenite grain boundary by iron-based carbides: not more than 80%; and
a number density of iron-based carbides in prior austenite grains: not less than 45/μm 2 .

2 . The hot-stamped part according to claim 1 , wherein the chemical composition satisfies:
Ti: 0.005% to 0.100%; Nb: 0.005% to 0.100%; or V: 0.005% to 0.100%; or any combination thereof.

3 . The hot-stamped part according to claim 1 , wherein the chemical composition satisfies:
Ni: 0.05% to 2.00%; Cu: 0.05% to 2.00%; or Mo: 0.05% to 0.50%; or any combination thereof.

4 . The hot-stamped part according to claim 1 , wherein the chemical composition satisfies
Ca or REM, or both thereof: 0.0005% to 0.0300% in total.

5 . A method of manufacturing a hot-stamped part, comprising the steps of:
heating a steel sheet to a temperature of not less than Ac3 point and not more than 950° C. at an average heating rate of not less than 2° C./sec; then, cooling the steel sheet through a temperature range from a Ar3 point to (Ms point−50°) C. at an average cooling rate of not less than 100° C./sec while performing hot pressing; and then, cooling the steel sheet through a temperature range from (Ms point−50°) C. to 100° C. at an average cooling rate of not more than 50° C./sec, wherein the steel sheet comprises a chemical composition represented by, in mass %:
C: 0.120% to 0.400%;
Si: 0.005% to 2.000%;
Mn or Cr, or both thereof: 1.00% to 3.00% in total;
Al: 0.005% to 0.100%;
B: 0.0003% to 0.0020%;
P: not more than 0.030%;
S: not more than 0.0100%;
O: not more than 0.0070%;
N: not more than 0.0070%;
Ti: 0% to 0.100%;
Nb: 0% to 0.100%;
V: 0% to 0.100%;
Ni: 0% to 2.00%;
Cu: 0% to 2.00%;
Mo: 0% to 0.50%;
Ca or REM, or both thereof: 0%-0.0300% in total; and
the balance: Fe and impurities, and
a maximum cooling rate is not more than 70° C./sec and a minimum cooling rate is not less than 5° C./sec in a temperature range from (Ms point−120°) C. to 100° C.

6 . The method of manufacturing the hot-stamped part according to claim 5 , wherein the chemical composition satisfies:
Ti: 0.005%-0.100%; Nb: 0.005%-0.100%; or V: 0.005%-0.100%; or any combination thereof.

7 . The method of manufacturing the hot-stamped part according to claim 5 , wherein the chemical composition satisfies:
Ni: 0.05%-2.00%; Cu: 0.05%-2.00%; or Mo: 0.05%-0.50%; or any combination thereof.

8 . The method of manufacturing the hot-stamped part according to claim 5 , wherein the chemical composition satisfies
Ca or REM or both thereof: 0.0005%-0.0300% in total.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Kawasaki Kaoru
• Azuma Masafumi
• Abukawa Genki

Classifications

• C21D1/673

  for die quenching · CPC title

• C21D9/0068 Primary

  for particular articles not mentioned below · CPC title

• C21D7/13

  by hot working · CPC title

• C21D2211/002

  Bainite · CPC title

• C22C38/02

  containing silicon · CPC title