Double alloy screw (bimetallic) screw base material for the alloy structural steel, gold foreign double-alloy screw is divided into two types: (1) edge spray double-alloy screw refers to the surface of the spirally spray welding wear-resistant corrosion-resistant alloy, (2) all-spray double-alloy screw means that the spiral edge and groove as a whole spray a layer of wear-resistant, corrosion-resistant, high temperature alloy; screw surface alloy hardness is higher than the substrate; Jin Yang's double alloy screw is the main component of the United States (Ni / B / Cr), self-fluxing alloy; the use of ion spray welding double alloy process, the advantage is to improve the hardness of the screw surface and wear, corrosion resistance, high temperature performance. Golden foreign screw - double-alloy screw is mainly applied to add glass fiber plastic, VO fire material and, PA, PC, PBT, PPO, PC + ABS and other fiberglass engineering materials.