Hitachi, Ltd.

Jiro Kuniya

Takahiko Kato

Yoshihisa Kiyotoki

Mitsuo Chigasaki

Masayoshi Kanno

Yoshiteru Chiba

Shizuo Matsushita

Isao Masaoka

Masahisa Inagaki

Hideo Maki

Iwao Takase

Katsuzo Aihara

Katsuyuki Imai

Ushio Kawabe

Kazumasa Takagi

Toshikazu Nishino

Takao Imagawa

Yutaka Misawa

Tokuumi Fukazawa

Kunio Miyazaki

Akira Sakamoto

Junjiro Nakajima

Yoshihide Wadayama

Haruhiro Hasegawa

Katsuki Miyauchi

Shigeo Hattori

Hajime Umehara

Kimihiko Akahori

Kiyotomo Nakata

Hisao Itow

Tetsuo Yasuda

Masato Koshiishi

Toshimi Yoshida

Masahiro Ogihara

Akira Maru

Shigeki Kasahara

Shinzoo Ikeda

Heishichiro Takahashi

Yositeru Chiba

Kikuo Takeshima

Tetsuro Yasuda

Tomomi Shiraki

Yochiteru Chiba

A valve which is cobalt-free excellent in wear resistance and seizure resistance manufactured by forming valve seats for a valve disc and a valve body with a nickel base alloy in which silicide particles or boride particles of small particle size are finely dispersed, and the valve seat is bonded to the valve disc or the valve body by way of an insert material comprising a nickel base alloy of a lower melting point by transient liquid phase diffusion bonding.

Valve and manufacturing method thereof

In the joint construction of cobalt-based alloy, a cobalt-based alloy layer, in which granular or massive eutectic carbidedisperses, is joined to a metal of a base metalvia an insert metal layer. For the joint construction of cobalt-based alloy, liquid phase diffusion bonding is performed at a temperature of 1100&#xb0; C. for a retention time of 1 hour with an insert metal with a thickness of about 40 &#x3bc;m being interposed between the base metal, which is S45C carbon steel, and a cobalt-based alloy material which has granular or massive eutectic carbide with a grain size not larger than 30 &#x3bc;m in a matrix of cast structure and contains 1.03 wt % C, 29.73 wt % Cr, 3.86 wt % W, 2.59 wt % Ni, 2.67 wt % Fe, 0.59 wt % Si, and 0.07 wt % Mo, the balance substantially being Co. The cobalt-based alloy layerafter bonding contains granular or massive eutectic carbide.

Joint construction of cobalt-based alloy

In the joint construction of cobalt-based alloy, a cobalt-based alloy layerin which granular or massive eutectic carbidedisperses, is joined to a metal of a base metalvia an insert metal layerFor the joint construction of cobalt-based alloy, liquid phase diffusion bonding is performed at a temperature of 1100&#xb0; C. for a retention time of 1 hour with an insert metal with a thickness of about 40 &#x3bc;m being interposed between the base metal, which is S45C carbon steel, and a cobalt-based alloy material which has granular or massive eutectic carbide with a grain size not larger than 30 &#x3bc;m in a matrix of cast structure and contains 1.03 wt % C, 29.73 wt % Cr, 3.86 wt % W, 2.59 wt % Ni, 2.67 wt % Fe, 0.59 wt % Si, and 0.07 wt % Mo, the balance substantially being Co. The cobalt-based alloy layerafter bonding contains granular or massive eutectic carbide.

A valve is characterized by excellent corrosion and wear resistance and maintainability due to use of a bonding corrosion and wear proof alloy containing non-continuously distributed eutectic carbide on the sliding portions of various types of apparatuses and valves by diffusion bonding. This serves to improve the maintainability of a thermal and nuclear power plant and to provide a nuclear power plant using recirculating water, which ensures excellent working safety, in particular. The corrosion and wear proof alloy is characterized in that network-formed eutectic carbide in the alloy containing the cast structure base metal and eutectic carbide is formed into(multiple) granules or lumps having a particle size of 30 microns or less so that said eutectic carbide is non-continuously distributed.

Valve bonded with corrosion and wear proof alloy and apparatuses using said valve

A wear resistant material containing no cobalt is used for a sliding portion of a control rod driving mechanism of a nuclear plant for reducing the exposure dose due to elution of cobalt and ensuring smooth driving of a control rod under a high load for a long time. A control rod driving mechanism employs a roller and a pin, each of which is made of a wear resisting alloy comprising coarse particles of a hard phase, having a particle size of from 20 to 100 .mu.m, and dispersed in a soft matrix made of an iron-based or nickel-based alloy containing chromium and having a hardness of 300 Hv or less. A nuclear reactor employs this control rod driving mechanism.

Wear resisting sintered alloy and its production, and control rod

An Fe-Cr-Mn alloy is disclosed which has the following composition by wt% and corrosion resistance of which is improved and deterioration in its strength is prevented at grain boundaries due to irradiation of high-energy particles such as neutrons: 5 to 40% of Mn, 5 to 18% of Cr, 2.0 to 12% of Al and the balance of Fe except for unavoidable impurities. In the alloy according to the present invention, Al is added to an Fe-Cr-Mn alloy by a restricted quantity as a main component element. As a result of the addition of Al, an alloy can be obtained in which lowering of concentration of Cr at grain boundaries due to irradiation of high-energy particles such as neutrons can be prevented or concentration of the solutes can be raised.

Fe-Cr-Mn Alloy

A fuel assembly for a nuclear reactor comprising a fuel cladding tube of three-layer structure having an outer surface in contact with reactor water of the nuclear reactor, an inner surface layer in contact with the nuclear fuel, and an intermediate layer interposed between the outer surface layer and the inner surface layer. the outer surface layer is made of a Zr-based alloy containing Nb, Sn and Mo. The inner surface layer is made of pure zirconium. The intermediate layer is made of a high ductility alloy which is higher in ductility than the outer surface layer and is higher in strength than the inner surface layer.

Fuel assembly for nuclear reactor, method for producing the same and

An austenitic steel excellent in resistance to neutron irradiation embrittlement which contains, by weight, not more than 0.03% carbon, not more than 1% silicon, 5 to 25% manganese, 15 to 26% chromium, and 10 to 20% nickel, the ratio of atomic volume of chromium to the average atomic volume of matrix of the steel being from 0.900 to 1.030. It is possible to add to the austenitic steel, besides the above-mentioned alloying elements, at least one element selected from the group consisting of niobium, titanium, zirconium, tantalum and vanadium which are effective in corrosion resistance and irradiation embrittlement under neutron irradiation in total amounts of not more than 1.0%. At least one of components composing the inside of a nuclear reactor or nuclear fusion reactor is made of the austenitic steel.

Austenitic steel excellent in resistance to neutron irradiation

A magnetic recording apparatus with a magnetic head, superconductive layers formed over at least flux generating surfaces of the magnetic head and normal conductive regions of small size for passing the flux provided in the superconductive layers, over the flux generating surfaces, so as not to form a closed magnetic circuit so as to enable reversible spontaneous magnetization in a magnetic recording medium proximate thereto. The minimum unit size (recording wavelength) of the reversible spontaneous magnetization in magnetic recording of the magnetic recording medium can be reduced from the order of 1 .mu.m to that of 0.1 .mu.m. Thus it is possible to increase the surface recording density of the magnetic recording medium utilizing more than 100 Mb/in.sup.2, comparable to the density achieved by the opto-magnetic recording. This in turn makes it possible to provide a large disc apparatus having a capacity of 60 MB or more.

Magnetic recording apparatus and magnetic head with superconducting

A process for controlling an oxygen content of a non-superconductive or superconductive oxide is provided, in which a beam of particles such as ions, electrons or neutrons or an electromagnetic radiation is applied to the non-superconductive or superconductive oxide of a perovskite type such as YBa.sub.2 Cu.sub.3 O.sub.7-x, thereby increasing or reducing the oxygen content of the oxide at the sites of oxygen in the crystal lattice of the oxide. Furthermore, a superconductive device such as a superconductive magnet, superconductive power transmission wire, superconductive transformer, superconductive shield, permanent current switch and electronic element is made by utilizing the process for controlling the oxygen concentration of the superconductive oxide.

Process for controlling oxygen content of superconductive oxide,

A channel box and/or a spacer of a fuel assembly is a welded construction and made of a Zr-Nb-Sn alloy comprising 0.5-2.2 wt % Nb, 0.5-1.5 wt % Sn contained so as to satisfy the relation of Sn(wt %) 22.times.Nb(wt %)--3.0, and balance Zr or a Zr-Nb-Sn-Mo alloy comprising 0.5-2.2 wt % Nb, 0.5-1.5 wt % Sn contained so as to satisfy the relation of Sn(wt %).gtoreq.2.times.Nb(wt %)--0.3, 0.1-0.8 wt % Mo, and balance Zr. The welded portion, its heat affected zone and the unwelded portion of the channel box and/or the spacer have substantially the whole equilibrium phase structure.

Nuclear reactor fuel assembly

A zirconium-based alloy with a high corrosion resistance, consisting essentially of 1 to 2 wt % Sn, 0.20 to 0.35 wt % Fe, 0.03 to 0.16 wt % Ni and the balance substantially Zr. The Fe/Ni content ratio of the alloy ranges between 1.4 and 8. The structure of the alloy has fine intermetallic compound of Sn and Ni is precipitated within the zirconium crystal grain of .alpha.-phase. The alloy may further contain 0.05 to 0.15 wt % Cr. This alloy exhibits reduced hydrogen absorption rate and suffers from no nodular corrosion, so that it can suitably be used as a material of nuclear fuel cladding tubes. The nuclear fuel cladding tube made of this alloys exhibits extended service life when used in a nuclear reactor of high degree of burn-up.

Zirconium-based alloy with high corrosion resistance

A butt welded tubular structure composed of tubular members of austenite stainless steel including a restraining member providing a cover to the entire outer circumferential surfaces of a welded joint and heat affected zones of the tubular members, the restraining member being formed of a metal or alloy of lower stress corrosion cracking sensitivity than the material of the tubular members and joined at the entire surfaces of opposite end portions thereof to the tubular members by welding, although the restraining member is not joined to the tubular members at portions of the restraining member corresponding to the welded joint and heat affected zones of the tubular members. The butt welded tubular structure is produced by joining tubular members of austenite stainless steel by butt welding, covering the entire outer circumferential surfaces of the welded joint and heat affected zones of the tubular members with a restraining member formed of a metal or alloy of lower stress corrosion cracking sensitivity than the material of the tubular members, and joining by welding the entire surfaces of opposite end portions of the restraining member to the tubular members while avoiding the joining of the restraining member to the welded joint and heat affected zones of the tubular members at portions of the restraining member corresponding to the welded joint and heat affected zones.

Butt welded tubular structure of austenite stainless steel

A method for cooling a weld in steel piping during butt welding with cooling of the inside comprises, after joining of pipe ends by a root pass on the inside, cooling the junction being welded by subsequent passes with injection of a liquid medium at room temperature from the center of the pipe against the surrounding wall, in a direction between radial and tangential directions relative to the inner pipe surface. An apparatus for practicing the cooling method comprises a rotatable multi-nozzle assembly having a radius of rotation corresponding to the inside diameter of the pipe and is capable of injecting the cooling medium against the inner surface of the pipe, a duct for conducting the cooling medium to the nozzles, and a pumping device for forcing the cooling medium under pressure into the nozzles.

Method of cooling weld in steel piping and apparatus therefor

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Hitachi, Japan

Jiro Kuniya