Although there are many types of self-tapping screws, they all have the following in common:
(1) It is generally made of carburized steel (99% of total production). It can also be made of stainless steel or non-ferrous metals.
(2) The product must be heat treated. Carbon steel self-tapping screws must be carburized, and stainless steel self-tapping screws must be solid solution hardened. In order to achieve the mechanical properties and performance properties required for the self-tapping screws.
(3) The surface hardness of the product is high and the core toughness is good. That is, "inner soft outside just." This is a major feature of the performance requirements of self-tapping screws. If the surface hardness is low, it will not be screwed into the base; if the core has poor toughness, it will not be used if it is broken. Therefore, "inner soft outer steel" is a very important requirement for self-tapping screws to meet the performance.
(4) The surface of the product needs surface protection treatment, generally electroplating treatment. Some products have to be phosphate treated (phosphorylated), such as wallboard self-tapping screws, which are mostly phosphating.
(5) Production by cold heading process. It is recommended to use a high speed cold heading machine and a high speed thread rolling machine or a high speed planetary thread rolling machine. The emphasis on high speed is to ensure product quality. Only the head of the self-tapping screw produced by the high-speed machine is formed, and the thread quality is high.
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