HOT-PRESSED STEEL SHEET MEMBER, METHOD OF MANUFACTURING THE SAME, AND STEEL SHEET FOR HOT PRESSING

摘要

A hot-pressed steel sheet member includes a specific chemical composition and further includes a steel structure in which an area ratio of ferrite in a surface layer portion ranging from a surface to 15 μm in depth is greater than 1.20 times an area ratio of ferrite in an inner layer portion being a portion excluding the surface layer portion, and the inner layer portion contains a steel structure represented, in area %, ferrite: 10% to 70%, martensite: 30% to 90%, and a total area ratio of ferrite and martensite: 90% to 100%. A tensile strength of the hot-pressed steel sheet member is 980 MPa or more.

主权项

1. A hot-pressed steel sheet member, comprising:
a chemical composition represented by, in mass %:
C: 0.10% to 0.34%;Si: 0.5% to 2.0%;Mn: 1.0% to 3.0%;sol. Al: 0.001% to 1.0%;P: 0.05% or less;S: 0.01% or less;N: 0.01% or less;Ti: 0% to 0.20%;Nb: 0% to 0.20%;V: 0% to 0.20%;Cr: 0% to 1.0%;Mo: 0% to 1.0%;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 0.01%;Bi: 0% to 0.01%; andbalance: Fe and impurities; and a steel structure in which:
an area ratio of ferrite in a surface layer portion ranging from a surface to 15 μm in depth is greater than 1.20 times an area ratio of ferrite in an inner layer portion being a portion excluding the surface layer portion; andthe inner layer portion comprises a steel structure represented, in area %:
ferrite: 10% to 70%;martensite: 30% to 90%; anda total area ratio of ferrite and martensite: 90% to 100%, wherein a tensile strength of the hot-pressed steel sheet member is 980 MPa or more.