Patent ID: 6022427
Filing Date: 2000-02-08
Classification: C21D,Y10S

Abstract:
A method of producing helical springs from steel wire comprising the steps of: hardening a spring's surface thermomechanically by a first shot peening of the surface of the spring when spring is unstressed; destressing said spring thermally after said first shot peening; applying a second shot peening to said spring, said second shot peening being carried out in at least two steps; said first shot peening hardening the spring's skin and deforming plasticly the spring's surface material to a specific depth, said step of destressing the spring thermally producing precipitation, aging, polygonization of crystalline structure in the deformed material of the spring; said second shot peening producing a substantial compression in the spring, said two steps of said second shot peening comprising a first step of rough peening with high-energy bombardment of shot penetrating substantially deeply the spring's skin a second one of said two steps comprising a fine peening at a lower speed than in said first step for increasing compression of the spring's surface and polishing the surface to prevent premature cracking of the spring's surface from substantial loads on the spring, said polishing decreasing notching of the spring and priming the spring for enameling; said first and second shot peening gerating substantially directionally oriented compression in said spring's surface, substantial compression occurring at a specific distance below said spring's surface in a direction along which an operating load will produce maximum tension when said spring is subjected to a load parallel to a load to be applied in a subsequent operation, said compressions counteracting any tension induced by a load during operation; whereby said spring is subjected to three shot peenings.