TAPPING SCREW PREPARED HOLE

摘要

PROBLEM TO BE SOLVED: To surely join a tapping screw prepared hole formed in a steel material by laser fusion and a tapping screw joined to this prepared hole. SOLUTION: This tapping screw prepared hole has a tapping screw prepared hole 3 formed of a through hole formed by fusing a steel plate 2a when moving a steel plate irradiating position of a steel plate fusing laser beam along a cross-sectional shape of the tapping screw prepared hole 3, a quenched hardening film 3f quenched by heating of the laser beam at steel plate fusing time and cooling after finishing the fusion and thinly formed on a surface of the steel plate 2a of an inner peripheral surface of the through hole and a hardening film separation starting part 3d having a shape starting to easily separate the quenched hardening film 3f when contacting with the tapping screw screwed in the tapping screw prepared hole 3 and formed on the inner peripheral surface of the through hole.