Bimetallic composite self-drilling screws usually use an external hexagonal flange head, a main body of austenite SUS304/316, and a drill tail made of SCM435 alloy steel, which makes the screws have both excellent corrosion resistance and the strength of self-drilling screws. They are used in electronics, automobiles, steel structures, railways, machinery, aviation, docks, chemical plants, curtain walls, animal husbandry and other fields.