Nippon Steel Corporation

Other

Aisin Aw Co., Ltd.

Aoyama Seisakusho Co., Ltd.

Nippon Steel Corporation Muroran Works

Hideo Kanisawa

Tatsuro Ochi

Manabu Kubota

Koji Tanabe

Kiichiro Tsuchida

Takao Taniguchi

Shuji Kozawa

Ken-ichiro Naito

Kazuaki Okada

Masayoshi Saga

Joji Tamura

Kenichiro Naito

Yutaka Neishi

Naoki Matsui

Masayuki Hashimura

Makoto Okonogi

Hiromasa Takada

Kouji Ohbayashi

Atsushi Murakami

Makoto Kosaka

Masao Ishida

Koji Adachi

Hisao Shirai

Keisuke Chiba

Nobuyoshi Uno

Tetsushi Chida

Ryuichi Seki

Kazuoki Shibuya

Koji Ohbayashi

Ryoko Inagaki

Tetsuro Hashiguchi

Kazutaka Aoyama

A bolt is provided that has high strength and excellent hydrogen embrittlement resistance characteristics. A bolt according to an embodiment of the present invention consists of, in mass %, C: 0.32 to 0.39%, Si: 0.15% or less, Mn: 0.40 to 0.65%, P: 0.020% or less, S: 0.020% or less, Cr: 0.85 to 1.25%, Al: 0.005 to 0.060%, Ti: 0.010 to 0.050%, B: 0.0010 to 0.0030%, N: 0.0015 to 0.0080%, O: 0.0015% or less, Mo: 0 to 0.05%, V: 0 to 0.05%, Cu: 0 to 0.50%, Ni: 0 to 0.30%, and Nb: 0 to 0.05%, with the balance being Fe and impurities. The bolt satisfies Formula (1) and Formula (2), and has a tensile strength of 1000 to 1300 MPa and satisfies Formula (3).4.9&#x2264;10C+Si+2Mn+Cr+4Mo+5V&#x2264;6.1&#x2003;&#x2003;(1)Mn/Cr&#x2264;0.55&#x2003;&#x2003;(2)[dissolved Cr]/Cr&#x2265;0.70&#x2003;&#x2003;(3)

Bolt

A steel component formed by carburizing and then induction-hardening of a steel consisting essentially of, by mass, C: minimum 0.08% and less than 0.3%; Si: maximum 2.0%; Mn: from 0.2% to 3.0%; P: maximum 0.03%; S: from 0.005% to 0.05%; Ni: maximum 1.5%; Cr: maximum 3.0%; Mo: maximum 1.0%; O: maximum 0.0025%; and N: from 0.005% to 0.03%; and further including either or both of, by mass, Al: from 0.005% to 0.05%, and Ti: from 0.005% to 0.05%; and still further including either or both of, by mass, V: maximum 0.3%, and Nb: maximum 0.3%; and a balance including Fe and unavoidable impurities. The hardness of the surface layer is at least 55 HRC and the hardness of the core portion is from 20 to 50 HRC. The core portion does not include a martensite structure.

Carburized and induction-hardened component

A method of heat-treating a steel member including carburizing a steel member in a carburizing gas under a reduced pressure. The steel member is then cooled in a cooling gas having a pressure lower than atmospheric pressure. A desired portion of the cooled steel member is then heated using high-density energy. The steel member is then quenched.

Heat treatment method of steel components, steel components and manufacture method of steel components

A high strength bold superior in delayed fracture resistant property has a bolt tensile strength of 1200 N/mm. A high strength bolt comprised of a head portion and shaft portion formed by a steel material, wherein the relation between a bolt tensile strength TS (N/mm) and tempering temperature T (&#xb0; C.) satisfies the following expression (1), the relation between the bolt tensile strength TS (N/mm) and the carbon equivalent C(%) calculated from the chemical composition of the steel material used for the high strength bolt satisfies the following expression (2), and the tensile strength of the bolt is refined to a range of 1200 N/mmto 1600 N/mmby quenching and tempering:&#x2266;1.1+850&#x2003;&#x2003;(1)&#x2266;550+1000&#x2003;&#x2003;(2) 

High strength bolt superior in delayed fracture resistant property and steel material for the same

A bar or wire product for use in cold forging, characterized in that it comprises a steel having the chemical composition, in mass %: C: 0.1 to 0.6%, Si: 0.01 to 0.5%, Mn: 0.2 to 1.7%, S: 0.001 to 0.15%, Al: 0.015 to 0.05%, N: 0.003 to 0.025%, P: 0.035% or less, O: 0.003% or less and balance: Fe and inevitable impurities, and it has, in the region from the surface thereof to the depth of the radius thereof&#xd7;0.15, a structure wherein ferrite accounts for 10 area % or less and the balance is substantially one or more of martensite, bainite and pearlite, and the average hardness in the region from the depth of the radius thereof&#xd7;0.5 to the center thereof is less than that of the surface layer thereof by 20 or more of HV; and a method for producing the bar or wire product. The bar or wire product is excellent in the ductility after spheroidizing and thus allows the prevention of occurrence of cracks in a steel product during cold forging, which has conventionally been a problem in manufacturing structural parts for a machine by cold forging.

Steel bar or wire rod for cold forging and method of producing the same

The present invention provides a steel bar or wire rod for cold forging excellent in ductility after spheroidizing annealing and capable of preventing the occurrence of cracking in the steel material during cold forging, which cracking has so far been a problem when manufacturing machine structural components by cold forging, and a method to produce the same. Specifically, a steel bar or wire rod for cold forging according to the present invention has a chemical composition comprising, in mass, 0.1 to 0.65% of C, 0.01 to 0.5% of Si, 0.2 to 1.7% of Mn, 0.001 to 0.15% of S, 0.015 to 0.1% of Al, 0.0005 to 0.007% of B, and the restricted elements of 0.035% or less of P, 0.01% or less of N and 0.003% or less of O, with the balance consisting of Fe and unavoidable impurities, and is characterized in that: the area percentage of ferrite structure is 10% or less at the portion from the surface to the depth of 0.15 time the radius of the steel bar or wire rod; the other portion consists substantially of one or more of martensite, bainite and pearlite; and further the average hardness of the portion from the depth of 0.5 time its radius to its center is less than the hardness of its surface layer (the portion from the surface to the depth of 0.15 times the radius) by HV 20 or more.

Bar or wire product for use in cold forging and method for producing the same

Disclosed are an outer race for a constant velocity joint, having improved anti-flaking properties and shaft strength, and a process for producing the same. The outer race for a constant velocity joint includes a cup and a serration and comprises by weight carbon: 0.45 to 0.59%, silicon: 0.15 to 0.4%, manganese: 0.15 to 0.45%, sulfur: 0.005 to 0.15%, molybdenum: 0.1 to 0.35%, boron: 0.0005 to 0.005%, aluminum: 0.015 to 0.05%, and titanium: 0.015 to 0.03%, the proportion of the effective case depth in track grooves of the cup being 0.25 to 0.45 in terms of the ratio of the effective case depth t to the wall thickness of the cup w, t/w, the proportion of the effective case depth of the involute serration in its end being 0.20 to 0.50 in terms of the ratio of the effective case depth t to the radius r, t/r. The involute serration in its end preferably has a former austenite grain size of not less than 8 in terms of the grain size number specified in JIS (Japanese Industrial Standards).

Outer race for constant velocity joint, having improved anti-flaking properties and shaft strength, and process for producing the same

The present invention provides a hot rolled steel wire rod or bar for machine structural use having, in the as-hot-rolled condition, cold workability equal to that of the conventional wire rods or bars softened through annealing after hot rolling, and a method to produce the same: and relates to a hot rolled steel wire rod or bar for machine structural use, characterized in that; the wire rod or bar is made from a steel consisting of, in weight, 0.1 to 0.5% of C, 0.01 to 0.5% of Si, 0.3 to 1.5% of Mn, and the balance comprising Fe and unavoidable impurities and containing strengthening elements as required; its microstructure consists of ferrite and pearlite; its ferrite crystal grain size number defined under Japanese Industrial Standard (JIS) G 0552 is 11 or higher; and a granular carbide 2 &mgr;m or less in circle-equivalent diameter and having an aspect ratio of 3 or less accounts for a percentage area of 3 to 15%.

Hot-rolled steel wire and rod for machine structural use and a method for producing the same

The present invention provides a steel wire rod for cold forging which can be spheroidizing-annealed in an as hot-rolled state without requiring preliminary drawing and can have high ductility after the spheroidizing annealing, and a method to produce the same: and is characterized in that; the steel contains, by weight, 0.1 to 0.5% of C, 0.01 to 0.5% of Si and 0.3 to 1.5% of Mn, with the balance consisting of Fe and unavoidable impurities, and further contains hardening elements as required; and the steel has a prior austenite grain size number, defined under Japanese Industrial Standard (JIS) G 0551, of 11 or higher, the amount of diffusible hydrogen in the steel measured by the programmed temperature gas chromatography being 0.2 ppm or less, and the hardness being Hv 250 to 700. The production method is characterized by: hot rolling the steel at a low temperature; rapidly cooling and tempering the wire rod thus rolled by holding it in a furnace atmosphere controlled in the temperature range of 300 to 600&deg; C. for 15 min. or longer but shorter than 1 h.; and then applying spheroidizing annealing as required.

Steel wire rod for cold forging and method for producing the same

Cold workable steel bar or wire and process

Hot rolled steel wire rod or bar for machine structural use and method for producing the same

This invention provides a steel for cold forging, excellent in surface layer hardness and softening properties by annealing, which contains, in terms of wt %, C: 0.1 to 1.0%, Si: 0.1 to 2.0%, Mn: 0.01 to 1.50%, P: not greater than 0.100%, S: not greater than 0.500%, sol. N: not greater than 0.005% and the balance consisting of Fe and unavoidable impurities, wherein a pearlite ratio in the steel structure is not greater than 120&times;(C %) % and the outermost surface layer hardness is at least 450&times;(C %)&plus;90 in terms of the Vickers hardness HV, and a production method thereof. The invention provides also a steel for cold forging, which has a structure wherein a ratio of graphite amount to the carbon content in the steel exceeds 20%, a mean grain diameter of graphite is not greater than 10&times;(C %) &mgr;m and a maximum grain diameter is not greater than 20 &mgr;m.

Steels for cold forging and process for producing the same

Disclosed are a high strength drive shaft and a process for producing the same. The high strength drive shaft comprises as a steel material, by weight, carbon: 0.48 to 0.58%, silicon: 0.01 to 0.15%, manganese: 0.35 to 0.75%, sulfur: 0.005 to 0.15%, molybdenum: 0.1 to 0.35%, boron 0.0005 to 0.005%, aluminum: 0.015 to 0.05%, and titanium: 0.02 to 0.08%, the proportion of the effective case depth of an involute serration in its end of the drive shaft being 0.3 to 0.7 in terms of the ratio of the effective case depth t to the radius r, t/r. The involute serration in its end preferably has a former austenite grain size of not less than 8 in terms of the grain size number specified in JIS (Japanese Industrial Standards). A steel comprising the above constituents and having a hardness of 85 to 95 HRB is machined and form rolled into a shaft, and the shaft is induction hardened and then tempered at 120 to 200&deg; C. to produce the high strength drive shaft.

High strength drive shaft and process for producing the same

A cold forging steel excellent in grain coarsening prevention and delayed fracture resistance and method of producing the same are provided that enable omission of a step of annealing or spheroidization annealing before cold forging and improvement of delayed fracture resistance of a high-strength component used with a heat-treated surface. The cold forging steel is a steel of a specified composition having dispersed in the matrix thereof particles of not greater than 0.2 &mgr;m diameter of one or more of TiC, Ti(CN), NbC, Nb(CN) and (Nb, Ti)(CN) in a total number of not less than 20/100 &mgr;m,. The method of producing a cold forging steel includes the steps of heating this steel to not lower than 1050&deg; C., hot-rolling the steel into steel wire or steel bar, and slowly cooling the steel at a cooling rate of not greater than 2 C./s during cooling to a temperature not higher than 600&deg; C. to obtain a steel having dispersed in the matrix thereof particles of not greater than 0.2 &mgr;m diameter of one or more of TiC, Ti(CN), NbC, Nb(CN) and (Nb, Ti)(CN) in a total number of not less than 20/100 &mgr;m,.

Cold forging steel having improved resistance to grain coarsening and delayed fracture and process for producing same

Non-tempered steel for mechanical structure

Growing community of inventors

Muroran, Japan

Hideo Kanisawa