Kabushiki Kaisha Kobe Seiko Sho

Sadayoshi Furusawa

Toyofumi Hasegawa

Jiro Koarai

Heijiro Kawakami

Takehiko Kato

Katsumasa Tanaka

Takeshi Nakahara

Hideo Takeshita

Shuji Iwata

Tsuyoshi Kohoka

Hitoshi Sato

Described herein is high strength steels used for bolts containing as alloy elements:

High strength steel bolts

A material for steel wool is disclosed which essentially consists of 0.05 to 0.20% of C, up to 0.10% of Si, 0.50 to 1.30% of Mn, 0.035 to 0.10% of P, up to 0.04% of S,0.05 to 0.15% of N and the balance Fe. In this material, Al.sub.2 O.sub.3 inclusions with sizes not smaller than 3 microns are suppressed to a level not greater than 20 ppm and when the content of the Al.sub.2 O.sub.3 inclusions (3 microns and over) is in the range of 5 to 20 ppm, Al.sub.2 O.sub.3 inclusions with a size ranging from 3 to 10 microns is contained in an amount not smaller than 30% of the total content of Al.sub.2 O.sub.3 inclusions with sizes not smaller than 3 microns.

Material for steel wool

A steel for machine construction having excellent cold forgeability and machinability, the steel having a composition of below 0.6% C, below 0.35% Si, below 1.65% Mn, below 3.5% Ni, below 3.5% Cr, below 0.35% Mn, 0.010-0.10% Al and below 0.002% B, the rest being Fe and impurities with limited contents of Ca in the range of 0.0005-0.05%, S of below 0.12% and Al.sub.2 O.sub.3 inclusion of below 0.002%.

Steel for machine construction having excellent cold forgeability and

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Kobe, Japan

Sadayoshi Furusawa