| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a cracking connecting rod containing a ferrite pearlite type non-heat treated steel and having high fatigue limit, and to provide its manufacturing method.SOLUTION: A cracking connecting rod is composed of a ferrite pearlite type non-heat treated steel containing 0.20 to 0.60% of C by mass% of additional elements of essential additional elements and optional additional elements, and has a big end part and a small end part engaging with a crankshaft and a piston respectively and a coining treatment handle part connecting these. C, N, Ti, Mn and Cr as essential additional elements and Si, P, S, V, Pb, Te, Ca and Bi as optional additional elements are added. For these additional elements, by mass%, Mn in a range of 0.30 to 1.50% and Cr in the range of 0.05 to 1.00% are added. Further N of 0.005 to 0.030% and Ti in the range of 0.20% or less with satisfying Ti≥3.4N+0.02 are contained. The cracking connecting rod contains Si of 2.0% or less, P of 0.2% or less, S of 0.02% or less, V of 0.50% or less, Pb of 0.30% or less, Te of 0.3% or less, Ca of 0.01% or less and Bi of 0.30% or less, and has 0.2% bearing force at the handle part of more than 700 MPa and 0.2% bearing force at the big end part of less than 650 MPa. The cracking connecting rod is manufactured through a coining step which is conducted by a coining treatment in temperature range of 250 to 600°C and with processing rate of 7% or more.</p> |
