INDUCTION-HARDENED TAPPING SCREW

WIPO Patent Application WO/2015/029266

A1

Provided is an induction-hardened tapping screw which, despite being formed from a cold-forging low-carbon steel wire material, is provided with high surface hardness and ductility, and is capable of self-tapping into a member to be fastened having a high hardness. Carbon is diffused from a surface of a screw comprising a low-carbon steel wire material having a carbon content of at least 0.06% but not more than 0.22%, to form a carburized layer having a carbon concentration of at least 0.7% but not more than 1.0%, and the carburized layer is quenched and hardened, and a tip part of a shaft part (4) is further subjected to induction hardening to obtain an induction-hardened tapping screw (1) which has been hardened so as to have a surface hardness of at least 650 HV, while having the core hardness thereof maintained in the range of 200-400 HV inclusive. This induction-hardened tapping screw (1) exhibits superior surface hardness with respect to the shaft part (4) thereof, and superior ductility with respect to an underhead fillet part (6) thereof, and thus is capable of self-tapping into a member to be fastened having a high hardness. Moreover, cold-forging low-carbon steel is used as the wire material therefor, and thus excellent workability and low cost are also achieved.

OTUSKI YUKITO (JP)
KAKUMA YASUNOBU (JP)

PCT/JP2013/077847

March 05, 2015

October 11, 2013

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NITTO SEIKO KK (JP)

F16B25/00; C21D1/06; C21D1/10; C21D9/00; C22C38/00; F16B35/00; C23C8/22

JP2001247937A	2001-09-14
JP2008144266A	2008-06-26
JP2009533635A	2009-09-17
JPS6436779A	1989-02-07
JP2009035171A	2009-02-19

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