... :L/D=15--55 1,Standards of single screw and cylinder of exturder machine:20mm--300mm,2,Ratio ... Less Than Grade 15,Surface Roughness :Ra 0.46,Screw Straightness :0.015mm7,Surface Chromium-Plating’s Hardness After ... Corrosion & Abrasion Resistance Bimetal Spraying Process8,Horniness screw (HTP1:abrasion HTP2:corrosion resistance,HTP3:abrasion and corrosion resistance) Barrel for plastic extruder machine