... steelTechnology: nitriding treatment, alloy coating spraying, heating treatment, screw fully hardening,specifications: 30g-25000g screwDepth of nitrition layer: 0.5-0.8mmNitriding ... : Ra 0.4umSurface of hardness of nitrated Cr coating layer: ≥950HVThickness of Cr coationg layer: 0.03-0.08mmUsed for granulation,PP, PE ...