Conical twin screw &barrel 1,Hardness After Hardending&Tempering : HB240~280 Technical ... :Less Than Grade 15,Surface Roughness :Ra 0.46,Screw Straightness :0.015mm7,Surface Chromium-Plating’s Hardness After ... Process6,Corrosion & Abrasion Resistance Bimetal Spraying Process7,Horniness screw (HTP1:abrasion HTP2:corrosion resistance,HTP3:abrasion and corrosion resistance Conical twin screw &barrel