screw head for blowing molding machine 1.Hardness of nitration: 950-1020Hv 2.Fragility of nitration: Less than grade 1 screw head for blowing ... screw barrel,extruder screw barrel,screw barrel for injection molding machine,twin screw barrel,screw barrel for extruder machinery,screw barrel ... Bimetallic Layer: HRC55-72 Depth of Bimetallic Layer: >2mm screw head for blowing molding machine