... of experience in producing springs2>design as customer's requirement3>competitive price good quality and good service4>specialized in ... has 60Si2MNA, 60Si2CRVA, 55CrSiSurface treatment plate gold, silver, white, red yellow, blue, green, purple, black, etc., salt spray ... to spring length, which ensured the spring quality stable and precise. . TOP quality black carbon steel constant force Flat spiral ...