Bi-metal screw, materials are SS304+SS410, SS316+SS410, SS304+SCM435, SS316+SCM435, anti-corrosion performance can reach 1000 hours, self-tapping composite nails are mainly used for the installation of photovoltaic support, can punch 0.4-1.00mm iron plate, self-drilling composite nails, Can be penetrated 1-6mm iron plate.