(1) is generally made of carburizing steel (total 99%). Can also be made of stainless steel or nonferrous metal manufacturing.
(2) products must undergo heat treatment. Self-drilling screws must be carburized carbon steel, stainless steel tapping screws must pass through the solid solution hardening. To enable the tapping screw mechanical properties and performance meet the requirements of the standard.
(3) products with high surface hardness and core toughness. That is, "neirouwaigang". This is tapping screw and the performance requirements of a feature. Such as low surface hardness, twist in a matrix are not such core toughness, a screw is broken, and you cannot use. So "neirouwaigang" is tapping screws to meet performance requirements.
(4) products which need surface protection treatment of the surface is generally electroplating treatment. Product surface treated with phosphate (phosphate). Such as: wall tapping screws for phosphate.
(5) the use of cold heading production. Recommended for high-speed cold headers and high-speed thread rolling machine or high-speed planetary rolling machine production to ensure product quality. Tapping screw head forming good thread of high quality.