Patent ID: 6027577
Filing Date: 2000-02-22
Classification: C21D,C23C,Y10T

Abstract:
A manufacturing method of a valve spring, comprising the steps of:applying nitriding treatment to a coiled valve spring made of an oil-tempered wire;shot-blasting at a first step cut wires of Hv 650 to 850 in hardness and 1.0 to 0.6 mm in diameter to the coiled valve spring for a first period of time while the coiled valve spring is being rotated about its center axis in a roller-type shot machine; andshot-blasting at a second step cut wires of Hv 650 to 850 in hardness and 0.4 to 0.2 mm in diameter to the coiled valve spring for a second period of time in a tumbling shot machine, said second period of time being longer than said first period.