What are the technological requirements for self-tapping screws?

Since self-tapping screws are required to have the performance of self-tapping low-carbon steel plates, they require high-hardness surfaces to achieve cutting and extrusion capabilities. At the same time, there must be sufficient heart strength and toughness to prevent distortion or twisting during work. The carburizing of this kind of screw belongs to shallow carburizing. Therefore, the continuous production line of mesh belt furnace or vibrating bottom furnace is mostly used at home and abroad.
Self-tapping lock screws, whether low-carbon steel, medium-carbon steel, or medium-carbon alloy steel, must be carburized, quenched and tempered. If the depth of the hardened layer is too shallow, the surface hardness and torsion strength are insufficient. When screwing in, the thread may deform or slip; on the contrary, if the hardened layer is too deep, it is easy to become brittle, either turning around or breaking. The sensitivity to hydrogen embrittlement is also high, and this trend is closely related to the tempering conditions and materials. The self-tapping screw has a wide range of effective hardened layer depth specified in the standard. The purpose, size, material and tempering conditions of the self-tapping screw should be considered, and the target value should be appropriately increased or decreased within the specified range.