conical twin screw barrel,conical screw barrel Technical parameter Nitriding depth:0.50-0.80mm Nitriding hardness:900-1000HV Nitriding brittleness:Less tha grade 1 Surface roughness:Ra0.4 Linearity of the screw:0.015mm Special surface treatment like hard nickel or hard chrome plating depending on the material to be processed can be used on most of these Ni-Alloy Materials as per clients requirements.