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Title:
INDUCTION-HARDENED TAPPING SCREW
Document Type and Number:
WIPO Patent Application WO/2015/029266
Kind Code:
A1
Abstract:
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.

Inventors:
otuski yukito (LTD. 20 Umegahata Inokura-cho, Ayabe-sh, Kyoto 54, 〒6230054, JP)
kakuma yasunobu (LTD. 20 Umegahata Inokura-cho, Ayabe-sh, Kyoto 54, 〒6230054, JP)
Application Number:
JP2013/077847
Publication Date:
March 05, 2015
Filing Date:
October 11, 2013
Export Citation:
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Assignee:
NITTO SEIKO CO., LTD. (20 Umegahata, Inokura-cho Ayabe-sh, Kyoto 54, 〒6230054, JP)
International Classes:
F16B25/00; C21D1/06; C21D1/10; C21D9/00; C22C38/00; F16B35/00; C23C8/22
Foreign References:
JP2001247937A2001-09-14
JP2008144266A2008-06-26
JP2009533635A2009-09-17
JPS6436779A1989-02-07
JP2009035171A2009-02-19
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