What type extruder cylinder is suitable for injection molding

What type extruder cylinder is suitable for injection molding? There is 45# steel, 40Cr steel, 38CrMoAIA nitriding steel on the market. If your product is fiberglass, chrome plating is about to fade after three months. It is better to choose nitriding stainless steel extruder cylinder for injection molding. In general, you can choose common extruder cylinder for PC, PMMA, PA and other materials. 

Double alloy screw is made from high quality SACM645 steel and the top thread is welded with double metal layer. Bimetallic extruder cylinder is made from high quality 38CrMoALA steel which has good wear-resistance, good corrosion-resistance, high temperature resistance, high pressure resistance. It is suitable for moulding lenses, transparent shell, cosmetic containers, transparent acrylic, nylon, PVC, ABS, products.