| 摘要 |
<p>PROBLEM TO BE SOLVED: To solve a problem of reduction of hot workability while securing good machinability by adding Bi in place of Pb in a martensitic free cutting stainless steel containing no Pb as a free cutting element and constituted by composite addition of Bi in place of Pb together with S and Te.SOLUTION: A martensitic Bi free cutting stainless steel has a composition containing, by mass%, C:over 0.10 to less than 0.35%, Si:0.10 to 2.0%, Mn:0.80 to 2.0%, P:0.005 to 0.050%, S:0.10 to 0.30%, Cr:10.0 to 18.0%, Bi:0.01 to 0.30%, Te:0.01 to 0.10%, O:0.005 to 0.030%, B:0.0005 to 0.0100%, N:0.04% or less and the balance Fe with inevitable impurities, satisfies the following formula (1), formula (2) and formula (3), 5×[C]+2×[S]+10×[Te]+3×[Bi]≤2.90 formula (1), 3.0≤[Mn]/[S]≤15.0 formula (2), 10≤[S]/[O]≤40 formula (3), and contains sulfide having an equivalent circle diameter of 2.0μm or more and an aspect ratio of 10 or less with an area ratio of 0.50 to 10.0%.</p> |
