Abstract: A reactor includes a core and first to fourth coils wound around the core and magnetically coupled to one another. A coupling coefficient K12 between the first and second coils, a coupling coefficient K13 between the first and third coils, and a coupling coefficient K14 between the first and fourth coils satisfy relations K13>K12 and K13>K14; and a coupling coefficient K23 between the second and third coils, a coupling coefficient K24 between the second and fourth coils, and a coupling coefficient K34 between the third and fourth coils satisfy relations K24>K23 and K24>K34.

Abstract: A reactor includes a core and first and second coils wound around the core about first and second center axes extended in a first direction, respectively. The core includes first and second core legs disposed inside the first and second coils, respectively. The first and second coils are arranged in a second direction perpendicular to the first direction. The first coil includes a first wound-wire part wound around the first core leg and two first terminal parts extended from both end portions of the first wound-wire part, respectively. The second coil includes a second wound-wire part wound around the second core leg and two second terminal parts extended from both end portions of the second wiring wire part, respectively. The second coil has the same shape and the same dimension as the first coil.

Abstract: In diffusion bonding a metal pipe 112e and a metal pipe 114e via a bonded interface 116e formed at the end parts, a portion that is inclined with respect to the radial direction of metal pipes 112e and 114e is provided at least at part of bonded interface 116. In this case, the inclination angle &phgr; of bonded interface 116e and the tip angle 2&thgr; of a pipe expansion tool 130 are preferably in the relationship, 0<&phgr;≦&thgr;+60°. In performing pipe expansion of such a metal pipe bonded body 110e, the pipe expansion tool 130 is moved from the metal pipe 112e, at which the inclined portion of junction face 116e is formed to have a protruding shape, towards the metal pipe 114e, at which the inclined portion of junction face 116e is formed to have a recessed shape. Furthermore, the inner diameter at the vicinity of the junction face of the metal pipe junction may be made larger than the inner diameter at positions away from the junction face.

Abstract: The present invention provides a metal pipe bonded body formed from a plurality of metal pipes. Each metal-pipe is formed with an elongated, pre-formed portion at each end, and a central portion, each elongated, preformed portion having a constant inside diameter greater than an inside diameter of the central portion of each metal pipe.

Abstract: Carbon steel pipes are joined to each other in a non-oxidizing atmosphere by using an insert constituted by a Ni-base alloy or a Fe-base alloy having a melting point which is lower than 1200° C. and a thickness of 80 mm or smaller under conditions that the surface roughness Rmax of the joined surfaces of the carbon steel pipes is 20 &mgr;m or smaller, the joining temperature is not lower than 1250° C. nor higher than 1330° C., duration at the joining temperature is 30 seconds or longer and the pressure is not lower than 2 MPa nor higher than 4 MPa. The expanding operation is performed such that the maximum difference in level of the joined portion is not larger than 25% of the carbon steel pipe and the expansion ratio is 25% or lower.

Abstract: In diffusion bonding a metal pipe 112e and a metal pipe 114e via a bonded interface 116e formed at the end parts, a portion that is inclined with respect to the radial direction of metal pipes 112e and 114e is provided at least at part of bonded interface 116. In this case, the inclination angle &phgr; of bonded interface 116e and the tip angle 2&thgr; of a pipe expansion tool 130 are preferably in the relationship, 0<&phgr;≦&thgr;+60°. In performing pipe expansion of such a metal pipe bonded body 110e, the pipe expansion tool 130 is moved from the metal pipe 112e, at which the inclined portion of junction face 116e is formed to have a protruding shape, towards the metal pipe 114e, at which the inclined portion of junction face 116e is formed to have a recessed shape. Furthermore, the inner diameter at the vicinity of the junction face of the metal pipe junction may be made larger than the inner diameter at positions away from the junction face.

Abstract: In a method of bonding ferric and austenitic dual stainless steels, an insert material made of a Ni base alloy having a melting point below 1290.degree. C. is put between the bonding cross section faces of mother material steels comprising a dual phase stainless steel. A pressure force in the range of 3 MPa to 5 MPa is applied to a bonding area. The bonding area is heated at a temperature in the range of 1290.degree. C. to a melting point of the mother material steel. The temperature is kept for in the range of 30 second to 180 second.

Abstract: In a metal material bonding method, an insertion material, which has a lower melting point than that of metal materials to be bonded, is interposed between bonding end surfaces of the metal materials to be bonded. The metal materials to be bonded is heated and held to a temperature not lower than the melting point of the insertion material and not higher than the melting point of the metal materials to be bonded while applying pressure to bonding surfaces of the metal materials to be bonded. The insertion material is formed to have a size which is smaller than each of the bonding surfaces of the metal materials to be bonded.