Steel wire for springs

Abstract

A steel wire for springs includes a main steel body and having a line shape, and an oxidized layer covering an outer peripheral surface of the main body. The steel constituting the main body contains between 0.6 and 0.7 mass % C, between 1.7 and 2.5 mass % Si, between 0.2 and 1 mass % Mn, between 0.6 and 2 mass % Cr, and between 0.08 and 0.25 mass % V, with the balance consisting of Fe and unavoidable impurities. The steel constituting the main body has a tempered martensitic structure. The oxidized layer includes a high Si concentration layer having a maximum concentration of Si of not less than 2.5 times and not more than 5.5 times that of the main body. The main body includes an intergranular oxidized layer arranged to constitute the outer peripheral surface and having a thickness of not less than 0.5 μm and not more than 2.5 μm.

1 . A steel wire for springs, comprising:
 a main body made of a steel and having a line shape; and   an oxidized layer covering an outer peripheral surface of the main body;   the steel constituting the main body containing not less than 0.6 mass % and not more than 0.7 mass % carbon, not less than 1.7 mass % and not more than 2.5 mass % silicon, not less than 0.2 mass % and not more than 1 mass % manganese, not less than 0.6 mass % and not more than 2 mass % chromium, and not less than 0.08 mass % and not more than 0.25 mass % vanadium, with the balance consisting of iron and unavoidable impurities,   the steel constituting the main body having a tempered martensitic structure, the oxidized layer including a high silicon concentration layer having a maximum concentration of silicon of not less than 2.5 times and not more than 5.5 times that of the main body,   the main body including an intergranular oxidized layer arranged to constitute the outer peripheral surface and having a thickness of not less than 0.5 μm and not more than 2.5 μm.   
     
     
         2 . The steel wire for springs according to  claim 1 , wherein the oxidized layer has a thickness of not less than 2 μm and not more than 5 μm. 
     
     
         3 . The steel wire for springs according to  claim 1 , wherein the oxidized layer contains not less than 80 mass % triiron tetraoxide.