Nippon Steel Corporation

Honda Motor Co., Ltd.

Nippon Steel Sumitomo Metal Corporation

Denso Corporation

Motoki Takasuga

Hitoshi Matsumoto

Tomohiro Yamashita

Tatsuya Hasegawa

Daisuke Hirakami

Hideki Matsuda

Taizo Makino

Masato Yuya

Tadashi Nishiwaki

Masashi Higashida

Kouji Morita

Yoshihiro Takitani

Tomomitsu Fukuoka

Yusuke Miyakoshi

Isamu Saito

Toshimasa Ito

Shigefumi Nishitani

Masashi Kawakami

Yoshiro Tanimura

A steel bar for hot forging according to the present disclosure has a chemical composition consisting of, in mass percent, C: 0.05 to 0.40%, Si: 0.05 to 0.50%, Mn: 1.51 to 3.50%, P: 0.010 to 0.100%, S: 0.30% or less, Cr: 0.05 to 2.50%, V: 0.10 to 0.75%, Ti: 0.005% to 0.250%, Al: 0.005 to 0.060%, and N: 0.002 to 0.020%, with the balance being Fe and impurities, and satisfying Formula (1). A number density of TiNs having a circle equivalent diameter of not less than 20 &#x3bc;m in steel is 0.3 to 4.0/mm:0.48&#x2264;C+0.11Mn+0.08Cr+0.75V+0.20Mo&#x2264;1.50&#x2003;&#x2003;(1)where, symbols of elements in Formula are to be substituted by contents of corresponding elements (in mass percent).

Steel bar for hot forging

A non-heat treated steel bar according to the present disclosure has a chemical composition consisting of, in mass percent, C: 0.39 to 0.55%, Si: 0.10 to 1.00%, Mn: 0.50 to 1.50%, P: 0.010 to 0.100%, S: 0.040 to 0.130%, Cr: 0.05 to 0.50%, V: 0.05 to 0.40%, Ti: 0.10% to 0.25%, Al: 0.003 to 0.100%, and N: 0.020% or less, with the balance being Fe and impurities, and satisfying Formula (1). A number density of AlO-based inclusions in each of which AlOis contained at 70.0% or more in mass % and &#x221a;AREA is not less than 3 &#x3bc;m is 0.05 to 1.00/mm.0.60&#x2264;C+0.2Mn+0.25Cr+0.75V+0.81Mo&#x2264;1.00&#x2003;&#x2003;(1)

Non-heat treated steel bar

A rolled steel material for fracture splitting connecting rods consists of, C: 0.30 to 0.40%, Si: 0.60 to 1.00%, Mn: 0.50 to 1.00%, P: 0.04 to 0.07%, S: 0.04 to 0.13%, Cr: 0.10 to 0.30%, V: 0.05 to 0.14%, Ti: more than 0.15% to 0.20% or less, N: 0.002 to 0.020%, and optionally may contain Cu, Ni, Mo, Pb, Te, Ca, and Bi, with the balance being Fe and impurities. fn1, defined by Formula (1), ranges from 0.65 to 0.80. Relative to the V content in the steel material, a V content in coarse precipitates having a particle size of 200 nm or more is 70% or less, and relative to the Ti content in the steel material, a Ti content in the coarse precipitates is 50% or more.1=C+Si/10+Mn/5+5Cr/22+(Cu+Ni)/20+Mo/2+33V/20&#x2212;5S/7&#x2003;&#x2003;(1)

Rolled steel material for fracture splitting connecting rod

Provided is a non-thermal refined soft-nitrided component including chemical composition of a steel material of a base metal containing: in mass %, C: 0.25 to 0.40%; Si: 0.10 to 0.35%; Mn: more than 2.0% to 2.8% or less; N: 0.0030 to 0.0250%; Cu: 0 to 1.0%; Mo: 0 to 0.3%; Ni: 0 to 0.5%; Ti: 0 to 0.020%; and a balance being Fe and impurities, the impurities including P: 0.08% or less; S: 0.10% or less; Al: 0.05% or less; and Cr: less than 0.20%, wherein a Vickers hardness at a position of 0.05 mm from the surface is 400 to 480, a Vickers hardness at a position of 1.0 mm from the surface is 200 or more, and a compound-layer depth at a stress concentrated region is 5 &#x3bc;m or less. This non-thermal refined soft-nitrided component has an excellent bending straightening property and a high fatigue strength.

Non-thermal refined soft-nitrided component

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Tokyo, Japan

Motoki Takasuga