Japanese Nitto Seiko Introduces the First Domestic Double Heat-treated Self-tapping Screw

When heat treating self-tapping screws used for steel plates, the industry usually uses carburizing, instead of thermal refinement which is commonly used on bolts. The reason is that thermal refinement cannot withhold thread hardness whereas carburizing can improve surface hardness. However, if you were to use carburized self-tapping screws on a steel plate that requires strong axial force, you would find the ductility weaker than thermal refined screws as well as higher risk of metal fatigue. Even now some people still use thermal refined bolts to tap threads.

In light of that, Nitto Seiko rolled out a new self-tapping screw utilizing "CORFLEX®-I" heat treatment technology. This technology not only improves hardness by partially applying to the portion of tapping, but also maintains hardness and tensile strength equivalent to those of a thermal refined bolt. Accordingly the new self-tapping screw can simultaneously have thermal refined hardness (which prevents metal fatigue) and self-tapping function even when applied on steel plates that require strong axial force.

Summing up the new self-tapping screw: (1) Can tap threads on steel plates (2) Have the same fatigue resistance as thermal refined bolts (3) Eliminating the need to tap threads with a bolt and thus saving total cost. The product has started sale in December 2015. Nitto Seiko expects to produce 1 million units monthly and supply them to the automotive, building and agricultural machinery industry.