To improve resistance against corrosion fatigue, delay breakdown, etc., by containing carbide nitride forming elements in a spring steel and finely dispersing carbide nitride of these elements on a spring constituted by covering a spring steel surface with a galvanized layer with Cr, Ni, Cu, Co, etc., as its main components.
A high strength spring improving environmental strength in a corrosive environment is covered with a plated layer with one or more than two kinds of Cr, Ni, Cu, Co as its main component on its steel surface. In this case, a carbide nitride forming element is contained in a spring steel, and carbide and nitride of these elements is finely dispersed in the steel. As this carbide nitride forming element, it is favourable to contain in mass %, one kind or more than two kinds of Ti: 0.001-0.5%, Nb: 0.001-0.5%, Ta: 0.001-0.5% and N: 10-200 ppm. Additionally, as a spring steel, the spring steel containing C: 0.7% or less Si: 0.1-0.4% and Mn: 0.01-2.0% is favourable.
IWATA TAKASHI
SHIMOTSUSA MASAKI
IBARAKI NOBUHIKO
KAKOU HIROSHI
NANBA SHIGENOBU
