Daido Tokushuko Kabushiki Kaisha

Daido Steel Co., Ltd.

Koyo Seiko Company, Ltd.

Diado Steel Co., Ltd.

Yutaka Kurebayashi

Sadayuki Nakamura

Masakazu Hayaishi

Takashi Kano

Masao Goto

Katsuhiko Kizawa

Tomohito Iikubo

Kazuhisa Ishida

Atsuhiko Ohta

Makoto Hobo

Kiyoyuki Hattori

Yasushi Matsumura

Disclosed is a free-cutting steel for machine structural use which always exhibits desired machinability, particularly, machinability by cutting with cemented carbide tools. This free-cutting steel is produced by preparing a molten alloy of the composition consisting essentially of, by weight %, C: 0.05-0.8%, Si: 0.01-2.5%, Mn: 0.1-3.5% and O: 0.0005-0.01%, the balance being Fe and inevitable, and adjusting the addition amounts of Al and Ca in such a manner as to satisfy the above ranges, S: 0.01-0.2%, Al: 0.001-0.020% and Ca: 0.0005-0.02%, and the conditions of &lsqb;S&rsqb;/&lsqb;O&rsqb;: 8-40 &lsqb;Ca&rsqb;&times;&lsqb;S&rsqb;: 1&times;10 &minus;1&times;10 &lsqb;Ca&rsqb;/&lsqb;S&rsqb;: 0.01-20 and &lsqb;Al&rsqb;: 0.001-0.020% to obtain a steel characterized in that the area in microscopic field occupied by the sulfide inclusions containing Ca of 1.0% or more neighboring to oxide inclusions containing CaO of 8-62% is 2.0&times;10 mm or more per 3.5 mm .

Free-cutting steel for machine structural use having good machinability in cutting by cemented carbide tool

Disclosed is a free-cutting steel containing Ti- and/or Zr-carbosulfide as inclusion and having good machinability both in turning and drilling. The free-cutting steel consists essentially of, in mass %, C: 0.05-0.80%, Si: 0.01-2.5%, Mn: 0.1-3.5%, Ti&plus;0.52Zr: 0.03-1.2%, S:0.015-0.6% and the balance of Fe and inevitable impurities, and is characterized in that the contents of Ti, Zr and S meet the condition of (Ti&plus;0.52Zr)/S<2. The free-cutting steel may contain, in addition to the above basic alloy composition, Ca: 0.0005-0.02% and/or Mg: 0.0003-0.02%. The latter steel exhibits much more improved machinability.

Free-cutting steel

Disclosed is a steel for machine structural use having good machinability and chip-breakability as well as a method of producing the steel. The steel consists essentially of, by wt. %, C: 0.05-0.8%, Si: 0.01-2.0%, Mn: 0.1-3.5%, S: 0.01-0.2%, Al: 0.001-0.020%, Ca: 0.0005-0.02%, O: 0.0005-0.01% and N: 0.001-0.04%, and further, one or both of Ti: 0.002-0.010% and Zr: 0.002-0.025%, the balance being Fe and inevitable impurities. At production of the steel controlled deoxidization is conducted by operation meeting certain conditions so that at least a certain amount of &ldquo;duplex inclusion&rdquo; having a specific chemical composition may be formed, and Ti and/or Zr is added to precipitate finely dispersed MnS inclusion particles with nuclei of Ti-oxide and/or Zr-oxide. The finely dispersed MnS inclusions must share a determined part of the total sulfide inclusions.

Steel for machine structural use having good machinability and chip-breakability

Disclosed is a free-cutting steel which exhibits good machinability in turning and small roughness of the turned surfaces, and in which substantially no macro-streak-flaw occurs. The free-cutting steel contains, by weight %, C: 0.03-0.20%, Mn: 0.5-3.0%, P: 0.02-0.40%, S: more than 0.2% up to 1.0%, one or both of Ti and Zr (in case of both, the total amount): 0.01-3.0%, O: 0.0005-0.0050% and Pb: less than 0.01%, the balance being Fe and inevitable impurities. The steel is characterized in that it contains, as the inclusion therein, Ti-based and/or Zr-based carbosulfide compound or compounds. The steel may further contain at least one from the group of Bi: up to 0.4%, Se: up to 0.5% and Te: up to 0.1%.

A steel for a large bearing suitable for parts of a large-sized bearing which are excellent in resistance to breakage and rolling fatigue life characteristics, and having a chemical composition by mass percentage of 0.80 to 1.30% of C, more than 0.35% and not more than 0.80% of Si, 0.30 to 0.90% of Mn, 0.90 to 1.50% of Cr, one or both of not more than 0.25% of Mo and 0.20 to 1.50% of Ni, the remainder being Fe and inevitable impurities, and exhibiting the following quench-hardenability measured according to a method specified in JIS G 0561: a HRC of 64 or more at J 1.5 mm, a HRC of 63 to 66 at J 7 mm, a HRC of 37 to 50 at J 15 mm, a HRC of 30 to 45 at J 20 mm, a HRC of 28 to 38 at J 45 mm.

Steel for large bearing and parts for large bearing

A steel product contains, by mass %, C: 0.45 to 0.60%, Si: 0.01 to 0.15%, Mn: 0.20 to 0.60%, S: 0.012% or lower, Al: 0.015 to 0.040%, Ti: 0.005 to 0.050%, B: 0.0005 to 0.0050%, N: 0.010% or lower, O: 0.0010% or lower, and balance being Fe and unavoidable impurities. Limitations are provided to allowable maximum sizes per each sort of contained non-metallic inclusions and the number per unit area thereof. This steel may contains one kind or two kinds or more of Cr: 1.00% or lower, Mo: 0.50% or lower and Ni: 1.50 or lower.

Steel for induction quenching and machinery structural parts using the same

Bearing steel materials that are superior in cold workability, machinability, hardenability and rolling contact fatigue life are provided. During the processing of steel materials, the generation of large carbides, that detrimentally affect the rolling contact fatigue life of the steel, is inhibited, thereby obviating the necessity of a heat treatment for dissolving the carbides. The present steel material contains the following alloy elements in percentage by mass: 0.55% to 0.82% of carbon; 0.05% to 0.20% of silicon; 0.50% or less of manganese; 0.90% to 1.30% of chromium; 0.05% to 0.30% of molybdenum; and the remaining percentage substantially of iron. After the spheroidizing annealing of the steel material, the total cross-sectional area rate of carbide is 25% or less.

Steel composition for bearings and method of producing the same

A heat resisting bearing steel having improved rolling fatigue life is disclosed. This steel consists essentially of 0.6-0.9% C, up to 0.5% Si, up to 0.5% Mn, 3.0-5.5% Cr, 3.0-5.0% Mo and 0.5-1.5% V, and the balance being Fe and inevitable impurities, and is characterized in that the content of large Al.sub.2 O.sub.3 inclusions with 10 micron or larger length is restricted to 1.5 ppm or less. The rolling fatigue life of this steel is long and fluctuation of the life is small, and therefore, the steel is highly reliable. It is suitable for the material of bearing to be used at a high peripheral speed and a high temperature such as the main rotational bearings of a heat engine such as a gas turbine.

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Nagoya, Japan

Yutaka Kurebayashi