Abstract: In a processing method for strengthening carbon steel materials, a carbon steel having an average hardness in the range of HRC 50 to 57 and a bainite structure is subjected to a tension working so as to provide a residual strain of at least 0.3% to the carbon steel. The tensile load in the tension working exceeds the yield point, and is 95% or less of the fracture load.

Abstract: A silent chain having multiple links each having a pair of teeth and apertures, which are connected by connecting pins inserted into the apertures. The links have an sheared link bearing surface which further reduces the wear of the sprocket tooth surface and further prevents defective bending of the silent chain. The bearing surface of the link tooth has a shear surface which may be formed by shaving or fine-blanking. The shear surface length may be at least approximately 70% or at least approximately 90% of the link thickness.

Abstract: In producing a rocker arm, following steps are used: fabricating a rocker arm blank which includes: a rocker arm body having an aperture therein adapted to be converted to a hole for the insertion of a shaft, and which blank is made of a nitrided steel comprising specified amounts of C, Mn, Cr, Al, Si, P, S, Cu, Ni, one of Pb and Bi, and optionally Mo, and, as the balance substantially, Fe; and a slipper surface forming piece; subjecting the rocker arm blank to a refining treatment to adjust its hardness; subjecting the apertures to reaming to form the shaft insertion holes; and subjecting the rocker arm blank with the shaft insertion holes formed therein to a nitriding treatment. Thus, it is possible to mass-produce rocker arms for an internal combustion engine, each of which has excellent mechanical properties.