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Screw or tapping screw

A self-tapping screw and screw technology, applied in the direction of screws, nuts, bolts, etc., can solve the problems of hardened self-tapping screw body, heavy load, troublesome process, etc.

Inactive Publication Date: 2005-12-07
NAT INST FOR MATERIALS SCI
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Problems solved by technology

[0003] However, in the conventional carburizing treatment, the carburized layer on the surface is thicker than 0.2mm, and there is a problem that the hardening reaches the inside of the self-tapping screw body.
For self-tapping screws, the hardness of the surface part must be greater than the hardness of the body, and the balance of the hardness is important. Since the thickness of the surface part with high hardness is expected to be appropriate, the traditional carburizing treatment is actually unsatisfactory.
In addition, in the carburizing treatment, surface treatment such as plating for maintaining corrosion resistance must also be performed, which makes this process cumbersome, and there is a problem that the load in the production process is large.

Method used

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Embodiment Construction

[0015] The invention of the present application has the above-mentioned features, and embodiments thereof will be described below.

[0016] As disclosed in the above-mentioned prior application, a screw having an ultrafine structure composed of ferrite grains having an average grain size of 3 μm or less, and furthermore, an average grain size of 1 μm or less can be used to have ferrite grains with ultra-fine grain size. A raw wire rod made of fine-structured steel, obtained by screw forming by cold or warm working. The ferritic ultrafine structure steel in this case can be produced by, for example, rolling a thick steel plate in multiple directions and multiple passes in a hot temperature region, and introducing a strain larger than the critical strain.

[0017] Thereby, for example, when the average ferrite grain size is 1.0 μm, a tensile strength of 700 Mpa can be achieved, and when it is 0.7 μm, a high strength of 800 Mpa can be achieved.

[0018] As for the steel having s...

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Abstract

A screw or a tapping screw, comprising a hyperfine structure steel having ferrite grains of 3 mum or smaller in average grain size and a nitrided layer on a surface part, wherein a strength is increased, a surface hardness is increased, and the surface hardness and an inside hardness are kept in balance, whereby a novel tapping screw and novel general screws can be provided.

Description

technical field [0001] The invention of the present application relates to a screw or a self-tapping screw and a manufacturing method thereof, and more specifically relates to a new screw or self-tapping screw with high strength, high surface hardness, and balanced surface hardness and internal hardness, and a manufacturing method thereof. Background technique [0002] Historically, self-tapping screws have been made of SWCH-10-20 or SUS410 as raw materials. After machining, carburizing and quenching treatment can ensure the necessary hardness, impact resistance and tensile strength during tapping. In addition, conventionally, in order to maintain corrosion resistance, surface treatment such as galvanizing has been performed after carburizing. Delayed fracture caused by plating or the like also becomes a problem. [0003] However, in the conventional carburizing treatment, the thickness of the carburized layer on the surface portion is 0.2 mm or more, and there is a problem...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): F16B25/00C21D1/06C21D9/00C22C38/00C22C38/02C22C38/04C22C38/06C22C38/58C23C8/26C23C8/32F16B33/06
CPCF16B33/06C23C8/26C22C38/02C22C38/06C22C38/04F16B25/00C21D9/0093
Inventor 鸟塚史郎长井寿小松隆史宫下直久高木文人松泽正明宫坂义政畑野圭希藤森千明小坂正义植松正明滨一
Owner NAT INST FOR MATERIALS SCI
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