Hot-pressed steel sheet member, method of manufacturing the same, and steel sheet for hot pressing

1. A hot-pressed steel sheet member, comprising:

a chemical composition represented by, in mass %:

C: 0.10% to 0.24%;

Si: 0.001% to 2.0%;

Mn: 1.2% to 2.3%;

sol. Al: 0.001% to 1.0%;

Ti: 0.060% to 0.20%;

P: 0.05% or less;

S: 0.01% or less;

N: 0.01% or less;

Nb: 0% to 0.20%;

V: 0% to 0.20%;

Cr: 0% to 1.0%;

Mo: 0% to 0.15%;

Cu: 0% to 1.0%;

Ni: 0% to 1.0%;

Ca: 0% to 0.01%;

Mg: 0% to 0.01%;

REM: 0% to 0.01%;

Zr: 0% to 0.01%;

B: 0% to 0.005%;

Bi: 0% to 0.01%; and

balance: Fe and impurities; and

a steel microstructure represented by, in area %:

ferrite: 10% to 70%;

martensite: 30% to 90%; and

a total area ratio of ferrite and martensite: 90% to 100%,

wherein 90% or more of all Ti in steel precipitates, and

wherein a tensile strength of the hot-pressed steel sheet member is 980 MPa or more.

2. The hot-pressed steel sheet member according to claim 1 , wherein the chemical composition comprises one or more selected from the group consisting of, in mass %:

Nb: 0.003% to 0.20%;

V: 0.003% to 0.20%;

Cr: 0.005% to 1.0%;

Mo: 0.005% to 0.15%;

Cu: 0.005% to 1.0%; and

Ni: 0.005% to 1.0%.

3. The hot-pressed steel sheet member according to claim 1 , wherein the chemical composition comprises one or more selected from the group consisting of, in mass %:

Ca: 0.0003% to 0.01%;

Mg: 0.0003% to 0.01%;

REM: 0.0003% to 0.01%; and

Zr: 0.0003% to 0.01%.

4. The hot-pressed steel sheet member according to claim 1 , wherein the chemical composition comprises, in mass %, B: 0.0003% to 0.005%.

5. The hot-pressed steel sheet member according to claim 1 , wherein the chemical composition comprises, in mass %, Bi: 0.0003% to 0.01%.

6. A method of manufacturing a hot-pressed steel sheet member, comprising:

heating a steel sheet for hot pressing in a temperature zone of an Ac 3 temperature to the Ac 3 temperature+100° C. for 1 minute to 10 minutes; and

hot pressing after the heating,

wherein the steel sheet for hot pressing, comprises:

a chemical composition represented by, in mass %:

C: 0.10% to 0.24%;

Si: 0.001% to 2.0%;

Mn: 1.2% to 2.3%;

sol. Al: 0.001% to 1.0%;

Ti: 0.060% to 0.20%;

P: 0.05% or less;

S: 0.01% or less;

N: 0.01% or less;

Nb: 0% to 0.20%;

V: 0% to 0.20%;

Cr: 0% to 1.0%;

Mo: 0% to 0.15%;

Cu: 0% to 1.0%;

Ni: 0% to 1.0%;

Ca: 0% to 0.01%;

Mg: 0% to 0.01%;

REM: 0% to 0.01%;

Zr: 0% to 0.01%;

B: 0% to 0.005%;

Bi: 0% to 0.01%; and

balance: Fe and impurities,

wherein 70% or more of all Ti in steel precipitates,

wherein the hot pressing comprises:

first cooling in a temperature zone of 600° C. to 750° C.; and

second cooling in a temperature zone of 150° C. to 600° C.,

wherein an average cooling rate in the second cooling is larger than an average cooling rate in the first cooling,

wherein the average cooling rate is 3° C./second to 200° C./second so as to cause ferrite to start to precipitate in the temperature zone of 600° C. to 750° C. in the first cooling, and

wherein the average cooling rate is 10° C./second to 500° C./second in the second cooling.