US 12,655,495 B2 · Steel sheet for hot stamping, method for manufacturing the same, hot stamped component, and method for manufacturing the same

Abstract

A steel sheet for hot stamping includes, as a chemical composition, by mass %: C: 0.060% to 0.120%; Si: 0% to 0.70%; Mn: 1.60% to 3.00%; P: 0.100% or less; S: 0.0100% or less; N: 0.0100% or less; Al: 0.001% to 0.100%; Ti: 0.005% to 0.050%; and B: 0.0005% to 0.0100%. If necessary, the chemical composition contains one or two or more selected from the group consisting of Nb, V, W, Ni, Cu, Mo, Sn, Ca, Mg, and REM and a remainder of Fe and impurities, A microstructure includes 70% or more of upper bainite by area ratio, and a number density of iron carbides having a major axis of 0.01 μm or more included in the upper bainite is equal to or greater than 4/μm2.

Claims18

Dependent claims

A steel sheet for hot stamping comprising, as a chemical composition, by mass %:

C:
0.060% to 0.120%;
Si:
0% to 0.70%;
Mn:
1.60% to 3.00%;
P:
0.100% or less;
S:
0.0100% or less;
N:
0.0100% or less;
Al:
0.001% to 0.100%;
Ti:
0.005% to 0.050%;
B:
0.0005% to 0.0100%;
Nb:
0% to 0.100%;
V:
0% to 0.100%;
W:
0% to 0.100%;
Ni:
0% to 2.00%;
Cu:
0% to 2.00%;
Cr:
0% to 2.00%;
Mo:
0% to 2.00%;
Sn:
0% to 0.200%;
Ca:
0% to 0.0500%;
Mg:
0% to 0.0500%;
REM:
0% to 0.0500%;
and
a remainder of Fe and impurities,
wherein a microstructure includes 70% or more of upper bainite by area ratio, and
a number density of iron carbides having a major axis of 0.1 μm or more included in the upper bainite is equal to or greater than 4/μm2, and
wherein a carbide included in the upper bainite has a needle shape, is present between laths of the upper bainite, and has a shape elongated in one direction.

42 more elements

A method for manufacturing a steel sheet for hot stamping according to claim 1, the method comprising:

a heating process of heating a steel ingot or a slab having the chemical composition according to claim 1 to 1,150° C. to 1,300° C. directly or after cooling the steel ingot or the slab;
a hot rolling process of performing hot rolling on the steel ingot or the slab after the heating process such that a finishing temperature is equal to or higher than 850° C. to obtain a hot-rolled steel sheet;
a coiling process of coiling the hot-rolled steel sheet after the hot rolling process at 700° C. to 500° C.;
a cooling process of cooling the hot-rolled steel sheet after the coiling process to room temperature;
a pickling process of pickling the hot-rolled steel sheet after the cooling process;
a cold rolling process of performing cold rolling on the hot-rolled steel sheet after the pickling process at a cumulative rolling reduction of 30% to 70% to obtain a cold-rolled steel sheet;
an annealing process of heating the cold-rolled steel sheet to an annealing temperature range of 850° C. to 900° C. and holding the cold-rolled steel sheet in the annealing temperature range for 10 to 2,000 seconds;
and
a heat treatment process of cooling the cold-rolled steel sheet after the annealing process to a temperature range of 400° C. to 600° C., holding the cold-rolled steel sheet in the temperature range for 100 to 1,000 seconds, and cooling the cold-rolled steel sheet to room temperature.

6 more elements

Dependencies are inferred from the claim text.

Steel sheet for hot stamping, method for manufacturing the same, hot stamped component, and method for manufacturing the same

Life of this patent

Steel sheet for hot stamping, method for manufacturing the same, hot stamped component, and method for manufacturing the same

Life of this patent

Abstract

Claims18