... blowing molding machine 1.Hardness of nitration: 950-1020Hv 2.Fragility of nitration: Less than grade 1 screw head for blowing molding ... screw barrel,extruder screw barrel,screw barrel for injection molding machine,twin screw barrel,screw barrel for extruder machinery, ... screw barrel for injection molding machinery. Material:38CrMoAlA,SKD11,SKD61,HPT2B,high quality ...