| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide steel for cold forging and nitriding which is excellent in cold forging characteristic and machinability after cold forging, and is capable of imparting a high core-part hardness, a high surface hardness, and a large effective depth of a hardened layer, to a cold-forged and nitrided component. <P>SOLUTION: The steel for cold forging and nitriding, contains 0.01 to 0.15% of C, 0.35% or less of Si, 0.10 to 0.90% of Mn, 0.030% or less of P, 0.030% or less of S, 0.50 to 2.0% of Cr, 0.10 to 0.50% of V, 0.01 to 0.10% of Al, 0.0080% or less of N, and 0.0030% or less of O with the balance being Fe and impurities, and has a chemical composition that satisfies the following formulae; [399×C+26×Si+123×Mn+30×Cr+32×Mo+19×V≤160], [20≤(669.3×log<SB POS="POST">e</SB>C-1959.6×log<SB POS="POST">e</SB>N-6983.3)×(0.067×Mo+0.147×V)≤80], [140×Cr+125×Al+235×V≥160], and [90≤511×C+33×Mn+56×Cu+15×Ni+36×Cr+5×Mo+134×V≤170]. The metal structure of the steel is a mixed structure comprised of ferrite and a carbide, wherein the carbide has a particle diameter of 3.0 μm or less, a mean aspect ratio of not greater than 5.0, and an area ratio of from 0.2 to 8.0% occupying in the matrix structure. <P>COPYRIGHT: (C)2013,JPO&INPIT |
