| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a tapping screw made of a high hardness stainless steel, which can be screwed into a workpiece made of a low-carbon steel while forming a female screw. <P>SOLUTION: A screw raw material 1a integrated with a head portion including a drive portion and a leg portion having threads, is formed by heading and rolling. The screw raw material 1a is made of an austenitic, ferritic or martensitic stainless steel. The screw raw material 1a is subjected to electroless nickel plating to form a nickel-phosphorus alloy plating film 22a, and subsequently to zinc plating to form a zinc plating film 23a. After a surface treatment film having a layered structure including the nickel-phosphorus alloy plating film and the zinc plating film is formed, the material is subjected to a low-temperature heat treatment to harden the nickel-phosphorus alloy plating film while emitting occluded hydrogen. <P>COPYRIGHT: (C)2013,JPO&INPIT |
