Sumitomo Metal Industries, Inc.

Toru Kato

Koji Watari

Takayuki Nishi

Hitoshi Matsumoto

Naoki Matsui

Hiroaki Tahira

Toshihiko Murakami

Masayuki Kawamoto

Yoshihiko Kamada

Masato Kurita

Mitsuo Uno

Harunori Kakimi

Masashi Hara

Norihiro Nishida

Masanori Sakamoto

A steel for machine structural use which comprises, on the percent by mass basis, C: 0.1 to 0.6%, Si: 0.01 to 2.0%, Mn: 0.2 to 2.0%, S: 0.005 to 0.20%, P: not more than 0.1%, Ca: 0.0001 to 0.01%, N: 0.001 to 0.02% and Al: not more than 0.1%, with the balance being Fe and impurities, with a value of [Ca]e defined by [Ca]e=T.[Ca]&#x2212;(T.[O]/(O))&#xd7;(Ca)of not more than 5 ppm or with a proportion of MnO contained in oxide inclusions of not more than 0.05 and a value of Ca/O of not more than 0.8 is excellent in machinability and, therefore, it can be used as a steel stock for various machine structural steel parts, such as in industrial machinery, construction machinery and conveying machinery such as automobiles. It is substantially free of Pb, hence suited for use as a steel friendly to the global environment. [Ca]e is the effective Ca concentration index (ppm by mass), T.[Ca] and T.[O] are the contents of Ca and O, respectively, in ppm by mass, and (O)and (Ca)are the proportions of O and Ca contained in oxide inclusion, respectively.

Steel for machine structural use and method of producing same

Steel for machine structural use

An apparatus for supplying molten steel and a continuous casting method therewith are described. The apparatus is equipped with a tundish having an upper nozzle at the bottom, a flow control mechanism disposed below the upper nozzle an immersion nozzle formed by a refractory material having a good electrical conductivity, one electrode disposed in the inner space of the tundish the other electrode disposed in the immersion nozzle and a power supply connected to the electrodes and In the method, the molten steel is supplied into a mold in the state of supplying an electric current between the inner surface of the immersion nozzle and the molten steel passing through the inside thereof by utilizing the apparatus for supplying molten steel. The deposition of the Al oxide or the like in the molten steel onto the inner surface of the immersion nozzle and others can be prevented, and thereby the generation of the surface defects in the products can also be prevented.

Molten steel supplying apparatus for continuous casting and continuous casting method therewith

The present invention relates to manufacturing methods of nitrided steel parts, having high tensile strength, high fatigue strength, and excellent bending roughness, through nitriding without thermal refining, to thus-manufactured steel parts, and to steel products for nitriding, and steels for nitriding having a specific chemical composition, serving as steel stock for the manufacture of such steel parts. The chemical composition is as follows: C: over 0.20 to 0.60%, Si: 0.05 to 1.0%, Mn: 0.20 to 1.50%, P: 0.08% or less, S: 0.005 to 0.10%, Cu: 0.30% or less, Ni: 0.30% or less, Cr: 0.30% or less, Mo: 0.30% or less, V: 0.20% or less, Nb: 0.05% or less, Ti: 0.003 to 0.03%, Al: 0.08% or less, Ca: 0.005% or less, Pb: 0.30% or less, N: 0.008 to 0.030%, and the balance of Fe and unavoidable impurities. Steel products preferably have the ferrite-pearlite microstructure having a ferrite percentage of not less than 10%. Nitrided steel parts are formed from the steel products serving as steel stock therefor, and have a nitrided case formed in the surface portion thereof.

Steels, steel products for nitriding, nitrided steel parts

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Kashima, Japan

Toru Kato