Abstract: This invention relates to a welded line pipe structure for transporting corrosive petroleum or natural gas. It is constituted by martensitic stainless steel pipes containing 8–16% Cr and at most 0.05% C. By suitably controlling the welding conditions at the time of girth welding of the steel pipes so as to ensure that the Cr concentration in grain boundary Cr-depleted portions existing immediately beneath a weld oxide scale is at least 5%, the occurrence of SCC in a high temperature CO2 environment can be prevented.

Abstract: Single layer and multilayer polyolefin foam pipes with improved compression resistance have a polyolefin foam layer which consists of mixtures of modified propylene polymers having strain hardening behaviour or propylene homopolymers with a stereospecifity index >98% or propylene copolymers with a stereospecifity index of the homopolymer matrix of >96%. The polyolefin foam pipes are coated steel pipes for transporting crude oil or gas products or district heating applications, single layer pipes for insulation purposes and for non- or low-pressure applications and multilayer plastic pipes for the transportation of hot or cold fluids.

Abstract: The present invention provides a fuel tank or a fuel pipe excellent particularly in the corrosion resistance of the outer surface in a salt damage environment, and is a fuel tank or a fuel pipe excellent in corrosion resistance characterized by: being formed by using a steel sheet or a steel pipe containing Cr of 9.0 to 25.0 mass % as the base material; on the outer surface thereof, having any one or more of welded portions, brazed portions and structurally gapped portions contacting components; and having one or more of metals, whose electrode potential in a 5%-NaCl aqueous solution at 30° C. is ?0.4 V or less relative to a saturated calomel electrode, attached to at least a part or parts of said portion(s) of the outer surface in an electrically conductive manner.

Abstract: An automotive fluid tubing, especially for gasoline, diesel fuel or hydraulic fluid, and composed of metal can be provided with a tube coating of aluminum and then a polyamide 12 layer which is extruded onto the aluminum coating. The polyamide extruded layer greatly improves the wear-resistance and corrosion-resistance of the tubing.

Abstract: A structure and a method for coupling a protective net to a flexible tube, comprising shaping the flexible tube, wrapping the flexible tube with the meshed protective net made of stainless steel, and welding both ends of the flexible tube to both ends of the protective net. A solution heating process for the flexible tube and welding process for the flexible tube and the protective net are simultaneously carried out under the same condition in the same furnace. As a result, the protective net and the flexible tube are uniform in terms of physical properties. Furthermore, intergranular corrosion of stainless steel by inevitable stress generated upon welding a flexible tube and a protective net using any one of conventional methods, and crevice corrosion between a welding ring and a flexible tube, are prevented.

Abstract: A high-strength steel pipe excellent in formability and burst resistance wherein, when a high-strength steel pipe exceeding 850 N/mm2 in tensile strength is produced by a UOE method, a ratio (R/r) of an average radius of curvature in a range of 120 mm in a circumferential direction including a weld of the steel pipe before pipe expansion in a pipe expansion process (R) to the radius of the steel pipe after pipe expansion (r) is 0.65 to 2.0, and preferably the ratio (R/r) is 0.90 to 2.0. Preferably, Vickers hardness of the base metal Hv, the minimum Vickers hardness at the HAZ Hz, pipe wall thickness t, and a peaking amount at the weld of the steel pipe before pipe expansion in a pipe expansion process &dgr; satisfy the following expression, (1+0.005t|&dgr;|)Hz<0.03584Hv2−25.34Hv+4712.

Abstract: A layered article having a curved surface made of a supporting metal metallurgically bonded to a supported metal.

Abstract: An automotive fluid tubing, especially for gasoline, diesel fuel or hydraulic fluid, and composed of metal can be provided with a tube coating of aluminum and then a polyamide 12 layer which is extruded onto the aluminum coating. The polyamide extruded layer greatly improves the wear-resistance and corrosion-resistance of the tubing.

Abstract: A pipe of layers of thermoplastic polyolefins of the same type, however with different properties, which are connected inseparably with one another, an outer first layer and a second layer, adjoining the first layer on the inside, consisting of a material, which has not been cross-linked, the second layer approximately having the FNCT the value or the NPT value of a one-layer standard pressure pipe and the first layer having an FNCT or NPT value, which is higher by a factor of at least 3 than that of the second value. Moreover, a third layer is provided, which adjoins the second layer on the inside, also consists of material that is not cross-linked and has a PNCT, which is higher by a factor of at least 3 than that of the second layer and an NPT layer, which is higher by a factor of at least 2 than that of the second layer.

Abstract: An outer pipe 10 and an inner pipe 12 are formed by drawing. Inner pipe 12 is inserted into outer pipe 10 and a metal core 14 is inserted into inner pipe 12. From this state, drawing is performed so that outer pipe 10 presses tightly against inner pipe 12. Metal core 14 is pulled out, resulting in a two-layer clad pipe 15. Alternatively, a two-layer clad pipe can also be made by drawing outer pipe 10 and inner pipe 12 without inserting metal core 14.

Abstract: The present invention provides a fuel tank or a fuel pipe excellent particularly in the corrosion resistance of the outer surface in a salt damage environment, and is a fuel tank or a fuel pipe excellent in corrosion resistance characterized by: being formed by using a steel sheet or a steel pipe containing Cr of 9.0 to 25.0 mass % as the base material; on the outer surface thereof, having any one or more of welded portions, brazed portions and structurally gapped portions contacting components; and having one or more of metals, whose electrode potential in a 5%-NaCl aqueous solution at 30° C. is −0.4 V or less relative to a saturated calomel electrode, attached to at least a part or parts of said portion(s) of the outer surface in an electrically conductive manner.

Abstract: A hose for containing a vacuum, which hose has an impermeable flexible tube capable of holding a vacuum and a braided or interwoven flexible interior wall, said wall providing support to said interior wall of said impermeable flexible tube. Optionally, an exterior braided or woven wall may be provided to the hose for protection or to allow the hose to be used as a pressure hose. The hose may delimit a vacuum space through which may travel a thermal transfer line containing, for example, cryogenic fluid.

Abstract: The multi-layered heat resistant metal tube is disclosed. This tube has excellent anti-coking characteristics and is suitable for use under the conditions where carbon tends to deposit and accumulate thereon due to contacting with hydrocarbons at a high temperature. The tube is made by forming weld-mounted overlaid layer of Cr—Ni alloy by building-up welding over the inner surface and/or the outer surface of a substrate tube made of a heat resistant metal. The Cr—Ni alloy comprises 35% by weight or more of Cr and satisfies the relationship: Ni(w%)≧0.5Cr(wt %). Building-up welding is preferably carried out by PPW (Plasma Powder Welding) in which the filler metal is supplied in the form of powder.

Abstract: An outer pipe 10 and an inner pipe 12 are formed by drawing. Inner pipe 12 is inserted into outer pipe 10 and a metal core 14 is inserted into inner pipe 12. From this state, drawing is performed so that outer pipe 10 presses tightly against inner pipe 12. Metal core 14 is pulled out, resulting in a two-layer clad pipe 15. Alternatively, a two-layer clad pipe can also be made by drawing outer pipe 10 and inner pipe 12 without inserting metal core 14.

Abstract: A pipe of layers of thermoplastic polyolefins of the same type, however with different properties, which are connected inseparably with one another, an outer first layer and a second layer, adjoining the first layer on the inside, consisting of a material, which has not been cross-linked, the second layer approximately having the FNCT the value or the NPT value of a one-layer standard pressure pipe and the first layer having an FNCT or NPT value, which is higher by a factor of at least 3 than that of the second value. Moreover, a third layer is provided, which adjoins the second layer on the inside, also consists of material that is not cross-linked and has a PNCT, which is higher by a factor of at least 3 than that of the second layer and an NPT layer, which is higher by a factor of at least 2 than that of the second layer.

Abstract: A four layer composite including a first interliner positioned between a 4xxx series braze clad and a core alloy and a second interliner positioned on the opposite side of the core alloy from the first interliner. At least one of the first and second interliners has higher amounts of Si than that of the core alloy adjacent thereto. The higher Si content interliner preferably contains about 0.02-1.1 wt. % Si.

Abstract: To provide a super-high strength line pipe that is excellent in low temperature toughness, can be field welded easily, and has a tensile strength of at least 900 MPa (exceeding ×100 of the API standard), and a production method thereof. The present invention relates to a super-high strength line pipe produced by shaping a steel plate into a pipe shape and arc welding seam portions, the strength of a base steel portion is 900 to 1,100 MPa and the strength of the weld metal is higher than the base steel strength −100 MPa. In the steel pipe, the Ni content of the weld metal is higher by at least 1% than that of the base steel. The combination of the chemical components of the steel plate with those of the weld metal, for accomplishing these steel pipes by a U&O step is shown concretely. A production method of the steel plate and the welding method for achieving the steel pipe are also described.

Abstract: A device for arresting the propagation of a buckle appearing on an outer tube of a double-walled rigid pipe intended to transport hydrocarbons and consisting of two coaxial tubes. The double-walled pipe is of the reelable type and intended for very great depths and consists of a thick and rigid annular transverse partition fastened to the inner tube and to the outer tube. The partition is joined to the outer tube and to the inner tube by means of an outer and inner sleeve having the same diameter as the outer and inner tubes and fastened to the latter.

Abstract: A heating furnace tube, a method of using the same and a method of manufacturing the same which have been developed with a view to eliminating inconveniences occurring when a carbon-containing fluid is made to flow in the heating furnace tube. The heating furnace tube which comprises a rare earth oxide particle distributed iron alloy containing 17-26 wt. % of Cr and 2-6 wt. % of Al. The method of manufacturing this heating furnace tube which comprises the steps of forming or inserting an insert metal on or into at least one of a joint end portion of one heating furnace tube element and that of the other heating furnace tube element, bringing these two joint end portions into pressure contact with each other directly or via an intermediate member, and diffusion welding the two heating furnace tube elements to each other by heating the insert metal.

Abstract: Sheet having a multilayer structure, called a sandwich sheet, composed of two rolled metal skins which are joined together by a core, in which sheet the core contains a stainless steel wool.

Abstract: A coolant line for air-conditioning systems that are operated with carbon dioxide as a coolant, particularly air-conditioning systems of motor vehicles, can be tightly connected at both ends to connecting parts. The line has an inside, metallic, corrugated hose that is coolant-tight, a radially pressure-resistant, flexible, metallic jacket that surrounds the hose with radial spacing and provides axial support, and a compression-proof, temperature-resistant intermediate plastic layer that fills the space between at least the radially-outside corrugation crests of the metal hose and the jacket so as to prevent play.

Abstract: A tube for a cracker unit in which ethylene is produced withstands, without oxidizing or losing its strength, the elevated temperatures required to effect cracking, yet retards coking. The tube has a shell formed from stainless steel or high nickel alloy and a liner formed from an iron-aluminum alloy. The liner retards the deposit of carbon and its build up known as coking. To form the tube, a high alloy ingot is bored to provide a bore that extends through its center. Then a weld overlay is applied to surface of the bore, with the overlay being derived from a weld metal containing at least 16% aluminum and the balance essentially iron. Thereafter, the ingot is heated to its hot working temperature and extruded through sets of opposed rollers, with the direction of advance being in the direction of the bore. The extruding transforms the ingot into a lined tube.

Abstract: A metal pipeline for use in an automobile having a protective coating layer comprising a metal tube, a zinc-nickel alloy plating layer formed on the outer circumferential surface of the metal tube, a chromate layer formed on the zinc-nickel alloy plating layer and an extrusion molded thermoplastic resin coating layer formed on the chromate layer. A nickel plating layer is formed under the zinc-nickel alloy plating layer. The metal pipeline having the protective coating layer has excellent durability under severe corrosive circumstances including external mechanical forces and also has excellent heat resistance, corrosion resistance and impact shock resistance.

Abstract: The invention provides methods of manufacturing hardened stainless steel tubing, pipe, shafts and assemblies. The present inventions also provides stainless steel shafts, tubing, pipe or assemblies reinforced with stainless steel members brazed and hardened within the shafts, tubing, pipe or assemblies.

Abstract: A valve has a contractible valve element formed of an inner laminae of PFA, an outer laminae of PTFE with the outer laminae having a boss to provide positive compression and positive distension of the valve element. The portion that constrict is welded to a PFA tubular end portion thus providing the advantages of a PTFE laminae with a boss and the PFA what it surfaces. The valve utilizes a valve mechanism which has a yoke which moves radially towards and away from the contractible valve element with linkages extending from yoke arms which connect to opposite sides of the contractible valve element. The valve element may thus be positively closed and positively opened. The hermetic seal between the outer PTFE laminae and the inner PFA laminae causes the inner laminae to extend outwardly when the outer laminae is positively distended thereby allowing the valve function where the fluid being controlled is under a negative pressure.

Abstract: An apparatus is provided for manufacturing a high quality multi-wound metal tube having satisfactory adhesion between multi-wound walls and for a seam portion at a reduced cost. Walls of the multi-wound tubular body are pressure welded with each other and then cooled, while at least the outer circumference of a brazing material between the walls of the multi-wound tubular body is kept at a flowable temperature by heating, by using at least one of a step of pressing substantially uniformly the outer circumferential surface of the tubular body in a radial direction from the outside, a step of substantially uniformly pressing the inner circumferential surface of the tubular body in the radial direction from the inside or a step of exerting a tensile force to the tubular body in the direction of the tubular axis.

Abstract: A clad material of a clad steel pipe is disposed on at least one of an internal surface and external surface of a base material, the clad material having two lateral edges which are welded together to form the pipe. A thickness of the clad material at the two ends of the clad material in a lengthwise direction is predetermined at a first value, the first value which enables absorption of a discrepancy in thickness when connecting the clad steel pipe to another clad steel pipe; and wherein a thickness of the clad material at other parts other than the two ends is determined to be at a second value which is smaller than the first value.

Abstract: A valve has a contractible valve element formed of an inner laminae of PFA, an outer laminae of PTFE with the outer laminae having a boss to provide positive compression and positive distension of the valve element. The portion that constrict is welded to a PFA tubular end portion thus providing the advantages of a PTFE laminae with a boss and the PFA what it surfaces. The valve utilizes a valve mechanism which has a yoke which moves radially towards and away from the contractible valve element with linkages extending from yoke arms which connect to opposite sides of the contractible valve element. The valve element may thus be positively closed and positively opened. The hermetic seal between the outer PTFE laminae and the inner PFA laminae causes the inner laminae to extend outwardly when the outer laminae is positively distended thereby allowing the valve function where the fluid being controlled is under a negative pressure.

Abstract: A known method for producing an object having a flanged tubular portion at the outer periphery, comprises supplying a continuously extended, cylindrical body made of the flange material to a welding zone at the tubular portion of the object and welding the flange material to the welding zone by heating and winding the cylindrical body around the object.

Abstract: A multi-wound stainless steel pipe produced by plastic-deforming a hoop material made of a stainless steel sheet applied with a Cu-brazing material on the surface thereof to a multi-wound pipe and after melting the brazing material between the walls of the multi-wound pipe, cooling the molten brazing material, wherein the Cu-brazing material between the walls and the Cu-brazing material at the surfaces of the inside surface and the outside surface of the pipe are diffused into the base material at a depth of from 0.5 .mu.m to 15 .mu.m and bonded thereto. The multi-wound stainless steel pipe is excellent in the pressure resisting strength and working strength and has a high quality.

Abstract: Welded high-strength steel structure with excellent SSC and corrosion resistance in a wet carbon dioxide environment having a low H.sub.2 S concentration. A structure having a Vickers hardness of at most 350 and a joint tensile strength of at least 620 MPa and composed of a base metal comprising a martensitic stainless steel with a martensitic or tempered martensitic structure containing 0.001 to 0.05% C and 9 to 14% Cr and a weld metal comprising an austenitic-ferritic stainless steel having a duplex structure composed of austenite and 35 to 75% by volume of ferrite and containing 22 to 27% Cr,7 to 11% Ni and 1.5 to 5% Mo, and at most 0.03% C as an impurity.

Abstract: A multi-wall tube and a method for making the multi-wall metal tube. In the process, a preformed tube is used as an inner core. A metal strip, coated with binding metal, is longitudinally wrapped around the core tube. The assemblage is then heated to the brazing temperature of the binding metal whereby all layers become integral to form the finished multi-wall tube.

Abstract: A lapped steel tube which is improved in resistances to the repeated high-pressure fatigue and the cavitation erosion, in the vibration resistance and in the fitting properties to eliminate the clearances between its inner, outer and intermediate pipes and to lower the production cost. The lapped steel tube comprises an outer pipe, an intermediate pipe and an inner pipe. The outer pipe is made of an electroseamed pipe, the intermediate pipe is made of a duplex-wound pipe or an electroseamed pipe, and the inner pipe is made of a seamless pipe. The outer, intermediate and inner pipes are lapped by drawing them together and are integrated by soldering the individual lapped faces.

Abstract: A tube element, especially for the exhaust systems and exhaust gas recirculation systems of combustion engines in vehicles. The element has a single- or multi-ply tube element made of metal which is provided with cylindrical end fittings and at least two annularly corrugated bellows and a connecting pipe forming a single element, with the pipe corresponding with the bellows in diameter as well as in wall thickness, and with the inside diameter of the connecting pipe corresponding substantially with the free inside diameter of the adjacent bellows. The element has a concentric reinforcing pipe at an external radial distance to the connecting pipe, with the ends of the reinforcing pipe, whose inside diameter corresponds with the outside diameter of the bellows, being connected with the radial outward crests of the first corrugations of the bellows following the connecting pipe.

Abstract: The invention concerns a process for manufacturing ribbed tubes, wherein a stainless steel tube is provided with ribs by helicoidally winding a copper strip around it, and a ribbed tube thus manufactured. In joining the tube and rib, the unmelted copper strip is set on the tube surface edgewise into a melted area produced by a laser beam exclusively on the tube surface, thereby bonding the strip onto the tube by the solidification of the melted tube material. In this manner ribbed tubes can be provided, featuring an internal tube made of corrosion-resistant stainless steel and a helicoidal rib made of copper for increasing the heat exchange surface of the tube, which is distinguished by high thermal conductivity.

Abstract: There is disclosed an Al alloy composite tube for refrigerant passages, made by extruding, or extruding and drawing a two-layer composite pipe obtained by shrink-fit of a tubular Al alloy inner material to the inside of a tubular Al alloy core, or a three-layer composite pipe obtained by shrink-fit of the two-layer composite pipe to the inside of a tubular Al alloy outer material; and a method for producing the same. This Al alloy composite tube for refrigerant passages causes less blisters at the interface between an inner pipe and an outer pipe, and can prevent debonding of the inner pipe.

Abstract: Heat-exchanging conduit tubes for a laminated heat exchanger made of aluminum material containing aluminum alloy having a brazing material claded and formed by folding one plate or overlaying two plates and brazing to connect edge joints of the folded plate or the overlaid plates, wherein the folded plate or the overlaid plates have projections protruded from one or both faces of the opposed plates toward the other plate, the projections are joined in contact with a flat face of the other plate or the projections of the other plate, and the edge joints of the folded plate or the overlaid plates are joined, and the height of the edge joint of the each plate is smaller than those of the projections. Thus, the heat-exchanging conduit tubes can be securely brazed to provide flat tubes having a satisfactory pressure resistance, and a method for producing them can be attained.

Abstract: A multi-walled steel pipe includes at least two pipe bodies of different diameters. The two pipe bodies are overlapped with one another. Either the inner surface of the outer pipe body or the outer surface of the inner pipe body is a rough surface having a roughness of 10 to 30 .mu.m. The rough surface is made by brasting, etching, or brushing or by the use of rolls. At least one of the overlapping surfaces is plated with copper to provide a brazing layer by which the overlapping surfaces are brazed together. The pipe bodies are double-walled stainless pipes, seamless stainless pipes, or electroseamed pipes.

Abstract: A liquid-impervious tube, includes at least one first band helically wound on itself, characterized in that this first band is porous and pervious to gaseous fluids and in that it includes a second thin band which is pervious to gaseous fluids and impervious to liquids, and which is also helically wound on itself, with partial overlapping of its turns, said turns being secured to one another in a impervious manner so that the second band defines a liquid-impervious continuous covering.

Abstract: The method of forming a seamed metal tube having a metal coating of this invention includes applying a metal coating to the upper face of a metal strip prior to welding. The strip is then formed into an open seam tube and welded, preferably in a non-oxidizing atmosphere with the seam preferably located in the lower portion of the tube. Finally, at least a lower portion of said tube is reheated with the seam located in the lower portion of the tube, thereby causing the metal coating to flow downwardly over the seam, coating the seam. In one embodiment, the strip is preformed into an arcuate shape and coated, wherein the metal coating increases in thickness toward the lateral strip edges, such that the coating will flow over the seam following welding. The inside coated seamed tube may also be immersed in a galvanizing or metal coating bath to coat the outside of the tube.

Abstract: A fuel injection pipe for a diesel engine which can sustain high internal pressure is provided. The inventive fuel injection pipe of a thick doublet pipe structure comprising an inner pipe and an outer pipe and having a thin inner diameter is arranged such that the inner pipe is formed out of a seam welded pipe made of a high tension steel plate and having a thickness of 0.4 to 1.5 mm and the outer pipe is formed out of a thick steel pipe made of the same material with the inner pipe or of carbon steel. Because the fuel injection pipe thus obtained allows inner facial wrinkles of the inner pipe to be suppressed to 25 .mu.m or less in depth, it can fully sustain high internal pressure of 1200 bar or more.

Abstract: A valve, which has heat-sensitive parts, has at least one connecting tube to which a pipe is arranged to be soldered using local heating. The connecting tube consists of a material of such low thermal conductivity that the heat-sensitive parts remain below the limit temperature as the heat required for soldering is applied. No cooling measures are therefore needed while the pipe is being joined by soldering.

Abstract: An externally and internally enhanced welded tube formed from a strip having a thickness b. The tube includes an inner wall enhanced with a first desired pattern having a thickness of a. An outer wail is enhanced with a second desired pattern, the second desired pattern having a thickness c. The weld fusing a portion of adjacent longitudinal edges of the strip wherein a weld bead associated with said weld is recessed within said desired patterns, does not extend beyond said desired patterns, and the length of said portion of said adjacent longitudinal edges that is fused together is from about (b+0.05a+0.05c) to about (b+0.2a+0.2c).

Abstract: The present invention includes a cast in place aluminum tailspout and a stainless steel exhaust pipe. The stainless steel exhaust pipe includes a flared out portion. The cast in place tailspout includes a section that surrounds at least a portion of the flared section of the exhaust pipe and includes a hooked finger for engaging an outwardly extending shoulder of the flared portion.

Abstract: The invention relates to a gas chromatography transfer line, having a glass tube (12), a steel tube (13) enclosing this glass tube and a heating coil (17) enclosing the steel tube, in which a tube (15) made of a material with high thermal conductivity is arranged between the steel tube (13) and the heating coil (17), the tube (15) being provided with a series of bores (16) in the axial and in the circumferential direction and being soldered to the heating coil (17) and to the steel tube (13), the solder (20) filling the bores (16) and intermediate spaces between the steel tube (13) and the tube (15).

Abstract: Clad pipe having an inner pipe and an outer pipe metallurgically bonded to each other is manufactured by a process comprising the steps of: (a) preparing an inner pipe and an outer pipe made of different metallic materials, the outer pipe having an inner diameter larger than the outer diameter of the inner pipe; (b) forming an Ni-B layer by electroplating or electroless plating on the surface of one of the pipes facing the other pipe when the two pipes are assembled, the Ni-B layer having a thickness of 2-100 .mu.m and consisting essentially, on a weight basis, of B: 0.5%-7%, Fe: 0%-30%, P: 0%-7%, and a balance of Ni and inevitable impurities; (c) assembling the two pipes by inserting the inner pipe into the outer pipe; (d) subjecting the assembled pipes to cold working for reduction in diameter to such a degree that the outer diameter of the inner pipe is reduced by from 0.

Abstract: A multi-layer metal tube consists of a flat steel band having a soldering layer connected to at least one side of the steel band. The soldering layer consists of a copper alloy having a melting point below 1020.degree.. The tube is produced by deforming the flat steel band into a tubular shape by winding or cylindrically rolling and by subsequently soldering the steel band to form the multi-layer metal tube. The soldering step prevents leaks as well as corrosion. In the corresponding method for manufacturing the multi-layer tubes the steel band in a first step is electrolytically degreased and activated in a nickel flash bath or in a copper pickling bath. Subsequently, the steel band is coated with the copper alloy which contains tin, zinc, or silver in order to reduce the melting point. After completion of the winding step or rolling step, the multi-layer tube can be coated with an additional corrosion-preventing layer.

Abstract: Disclosed is a welded tube with an excellent corrosion-resistant inner surface, in which the inner surface including the bead part has a first plate layer of one metal material selected from Sn, Sn-Zn, Sn-Ni, Ni-P and Ni-B and the first plate layer is overcoated with a second plate layer of one metal material selected from Ni, Co and alloys based on the metals. The welded tube is free from exposure of the steel base out of the plate layer and is also free from cracks, pin holes, overplated spots and peeling of the plate layer. It has excellent corrosion resistance and good workability for working the terminals. The welded tube is produced by forming a first plate layer of Sn, Sn-Zn, Sn-Ni, Ni-P or Ni-B on at least one surface of a steel strip, then forming a second plate layer of Ni, Co or an alloy based on the metals over the first plate layer, shaping the thus plated steel strip into a tube by welding with the plated surface being inside and then heat-treating the tube.

Abstract: Disclosed are a welded pipe with an excellent corrosion resistance, having two plate layers on the inner surface thereof, and a method of manufacturing it. The inner surface is coated with the plate layers even on the bead part and other steel foundation-exposed parts. A first plate layer of at least one of Ni, Co and Ni- or Co-base alloys is formed on at least one surface of a steel strip, then a second plate layer made of a metal or alloy having a lower melting point than the metal or alloy of forming the first plate layer is formed over the first plate layer. The thus plated steel strip is formed into a pipe and then heat-treated to give a welded pipe having no exposed steel foundation. The welded pipe has excellent corrosion resistance and workability.

Abstract: Line pipe having good corrosion-resistance and weldability, in which at least the inner surface of the pipe that is in direct contact with the fluid moved through the pipe is formed of high chromium steel that contains, by weight percent, 7.5 to 16 percent chromium, a carbon content reduced to no more than 0.03 percent and a nitrogen content reduced to no more than 0.02 percent, and a substrate that is not in direct contact with the fluid and is formed of steel that contains 0.02 to 0.25 percent carbon, 0.1 to 1.0 percent silicon, 0.05 to 2.0 percent manganese and 0.005 to 0.1 percent aluminum, a phosphorus impurity content reduced to no more than 0.015 percent and a sulfur impurity content reduced to no more than 0.005 percent, and in which the thickness of the high chromium steel portion does not exceed 25 percent of the total thickness of the pipe.