high strength steel for ventilfedern, processes for the manufacture of the steel and the resulting ventilfedern.

摘要

A high-strength steel for valve springs, consisting of 0.50-0.70 wt. % of carbon, 1.50-2.50 wt. % of silicon, 0.50-1.20 wt. % of manganese, 1.50-2.50 wt. % of nickel, 0.50-1.00 wt. % of chromium, 0.20-0.50 wt. % of molybdenum, 0.15-0.25 wt. % of vanadium, and the balance being iron and inevitably included inclusions. Also disclosed is a process for producing such a high-strength steel, which includes a step of minimizing oxygen in a melt of the steel, so as to reduce the oxygen content of the steel to 15 ppm or less, and a step of adding calcium to the melt and thereby controlling the form of the inclusions. The process may further include a step of minimizing titanium and nitrogen in the melt, so as to reduce the titanium and nitrogen content of the steel to 50 ppm or less, and 60 ppm or less, respectively.