... special design for extruder, based on 38CrMoAlA. conical twin screw and barrel for plastic extruder, granulator or pelletizer Ruian ... steelTechnology: nitriding treatment, alloy coating spraying, heating treatment, screw fully hardeningDiameter: Φ45-Φ200(according to the demands ... less than grade 1Surface roughness: Ra 0.4umStreightness of screw: 0.015mmSurface of hardness of nitrated Cr coating layer ...