What is the difference between a Bimetallic Screw and another screw?

Update:16-11-2018
Summary:

The double alloy screw is made of 88wc/12c0.Crc/25Nicr. […]

The double alloy screw is made of 88wc/12c0.Crc/25Nicr.XaloY108 material and is subjected to integral quenching treatment. It is suitable for all kinds of added glass fiber, plastic and PPA, PO, PPS, LCP, ABS, fireproof, bakelite, magnetic powder, PC. Special engineering plastics. It solves the troubles of chrome-plated screws often falling off the chrome-plated layer for the end users, and completely guarantees the environmental protection requirements of products. It is your ideal helper.
Production use: injection molding machine / extrusion machinery / bakelite machinery
Processing range: inner diameter ф20mm-ф250mm
Effective length: 8000mm
Alloy composition: 88wc/12c0.Crc/25Nicr.XaloY108
Nitriding hardness: HRC59°-65°

The role of other nitriding material injection molding machine screw barrels is:
1. Nitriding can make the surface of the screw barrel have higher hardness and wear resistance. For example, the hardness of the surface of the screw barrel made of 38CrMoAlA high-quality alloy steel after nitriding can reach HV950 or above, equivalent to HRC=55°. -58°, and the high strength and high wear resistance after nitriding are maintained at 350-450 ° C without significant changes
2, can improve the fatigue resistance. Due to the formation of greater compressive stress in the nitride layer, the screw barrel exhibits higher fatigue limit and lower notch sensitivity under the alternating load, nitriding The fatigue limit of the rear screw barrel can be increased by 30%.
3, improve the corrosion resistance of the workpiece, due to nitriding to form a layer of dense, chemically stable phase layer on the surface of the screw, high corrosion resistance in water vapor and alkaline solution, such nitriding method Simple and economical, it can replace galvanizing, bluing, and other chemical coatings. In addition, some screw barrels are nitrided, which not only improves wear resistance and corrosion resistance, but also reduces the stickiness of mechanical and screw barrels. The phenomenon of mixing, extending the working life of the machine.