... of the double alloys:HRC56-656)Fully hard screw(wear-proof, corrosion-proof, heatproof, high-pressure ... double screw extruders, rubber machinery, and petroleum machinery. Technical index: 1)Depth of nitration case:0.4- ... 3)Roughness of the surface:Ra 0.4mm 4)Screw straightness: 0.015mm/m 5)hardness of ... the double alloys:HRC56-65 6)Fully hard screw(wear-proof, corrosion-proof, heatproof, high-pressure ...