| 摘要 |
本发明提供一种高碳热轧钢板，其将添加有B的钢作为原材料，即便于氮气环境中进行退火，亦可稳定地获得优异的淬火性，且于淬火处理前，具有硬度以HRB计为73以下、总伸长率为39%以上等优异的加工性。所述高碳热轧钢板具有如下的组成：以质量%计含有C：0.20%~0.40%、Si：0.10%以下、Mn：0.50%以下、P：0.03%以下、S：0.010%以下、sol.Al：0.10%以下、N：0.0050%以下、B：0.0005%~0.0050%，进而含有合计为0.002%~0.030%的Sb、Sn、Bi、Ge、Te、Se中的1种以上；并且于B含量中所占有的固溶B量的比例为70%以上，并具有包含肥粒铁与雪明碳铁、所述肥粒铁粒内的雪明碳铁密度为0.08个/μm 2 以下的微组织，且硬度以HRB计为73以下，总伸长率为39%以上。; moreover, the high-carbon hot rolled steel sheet has a hardness of 73 HRB or less and excellent workability such as a total elongation of 39% or more before quenching. The high-carbon hot rolled steel sheet contains, in terms of mass %, 0.20 to 0.40% of C, 0.10% or less of Si, 0.50% or less of Mn, 0.03% or less of P, 0.010% or less of S, 0.10% or less of sol.Al, 0.0050% or less of N, and 0.0005 to 0.0050% of B, and further contains a total of 0.002 to 0.030% of one or more of Sb, Sn, Bi, Ge, Te and Se. In the high-carbon hot rolled steel sheet, an amount of solid-solution B in the B content is 70% or more. The high-carbon hot rolled steel sheet has a microstructure including ferrite and cementite, wherein a cementite density in a ferrite grain is 0.08 /μm 2 or less. The high-carbon hot rolled steel sheet has a hardness of 73 HRB or less and a total elongation of 39% or more. |
