Abstract: A high pressure fuel injection tube includes a connection head with a seat face in a spherical shape. A ring-like flange is spaced from the seat face in an axial direction. A conical portion is formed in the interval between the ring-like flange and the seat face. An undercut bent recess groove with a ring-like shape and a deep depth is formed on the conical portion. Thus, a shallow smooth ring-like recess groove is formed on an inner side of the connection head, and a compressive residual stress is present at an inner peripheral face of the ring-like groove.

Abstract: A high pressure fuel injection tube includes a connection head with a seat face in a spherical shape. A ring-like flange is spaced from the seat face in an axial direction. A conical portion is formed in the interval between the ring-like flange and the seat face. An undercut bent recess groove with a ring-like shape and a deep depth is formed on the conical portion. Thus, a shallow smooth ring-like recess groove is formed on an inner side of the connection head, and a compressive residual stress is present at an inner peripheral face of the ring-like groove.

Abstract: A high-pressure fuel injection pipe has a connecting head with an outer circumference formed for a mating seat portion. A shallow annular groove is formed in the inner side of the connecting head while shaping the head. A connecting washer is fit on the outer circumference of the lower neck of the connecting head. The injection pipe is characterized in that the lower neck of the connecting head is provided with an at least two-stepped portion having no slope, and in that the connecting washer is provided with a stepped portion corresponding at least partially to the stepped portion of the connecting head, so that the stepped portions may abut against each other.

Abstract: A high-pressure fuel injection pipe having connecting head portion is provided which is capable of eliminating a fear of the occurrence of cavitation erosion of the inner surface of the connecting head portion and a fatigue failure of the same head portion by having a contour of a cross section of an annular pocket occurring in an inner part of the connecting head portion during a head portion processing operation extend shallowly and gently. This fuel injection pipe has at a connecting end portion of a thick-walled steel pipe having a relatively small diameter, including a seat surface, an annular flange formed so that the flange is axially spaced from the seat surface, and a conical surface connected to the seat surface, extending therefrom to the annular flange and tapering off to a free end of the connecting head portion, wherein the conical surface is provided at a part thereof with an annular, shallow, cross-sectionally curved recess.

Abstract: A high-pressure fuel injection pipe has a connecting head with an outer circumference formed for a mating seat portion. A shallow annular groove is formed in the inner side of the connecting head while shaping the head. A connecting washer is fit on the outer circumference of the lower neck of the connecting head. The injection pipe is characterized in that the lower neck of the connecting head is provided with an at least two-stepped portion having no slope, and in that the connecting washer is provided with a stepped portion corresponding at least partially to the stepped portion of the connecting head, so that the stepped portions may abut against each other.

Abstract: A high-pressure fuel injection pipe having connecting head portion is provided which is capable of eliminating a fear of the occurrence of cavitation erosion of the inner surface of the connecting head portion and a fatigue failure of the same head portion by having a contour of a cross section of an annular pocket occurring in an inner part of the connecting head portion during a head portion processing operation extend shallowly and gently. This fuel injection pipe has at a connecting end portion of a thick-walled steel pipe having a relatively small diameter, including a seat surface, an annular flange formed so that the flange is axially spaced from the seat surface, and a conical surface connected to the seat surface, extending therefrom to the annular flange and tapering off to a free end of the connecting head portion, wherein the conical surface is provided at a part thereof with an annular, shallow, cross-sectionally curved recess.

Abstract: A stainless steel pipe of the bright annealing finish type, having a highly-soothed inner surface according to the present invention is characterized in that the inner surface roughness of the pipe, expressed in Rmax is 1.0 micrometer or less, and suitable as a clean pipe for use in an apparatus for the production of semiconductors. According to the method of production of the present invention, a stainless steel pipe having a highly-smoothed inner surface can be obtained by cold drawing and bright annealing treatment only. By this method, such a treatment that has been considered to be essential, for example, electrochemical polishing can be omitted, so that the production cost can be greatly reduced. The stainless steel pipe of the invention can thus be widely utilized in the fields of the production of semiconductors and the like.

Abstract: A method of manufacturing hollow steel bars comprising the steps of preparing a hollow billet with the dimensions meeting a condition expressed by the following formula (1) by piercing a steel billet with a piercer after heating, inserting a mandrel as an inner surface sizing tool into a hollow billet, and then rolling the hollow billet on a cross-rolling mill having three rolls arranged around a pass line to provide plastic working for reduction of the outside diameter and adjustment of the wall thickness of the hollow billet so as to meet a condition expressed by the following formula (2), and a manufacturing apparatus comprising an electric resistance heating unit, the piercer, and the cross-rolling mill, whereint.sub.0 /d.sub.0 >0.1 (1)Rt<0.55Rd (2)wheret.sub.0 =wall thickness of hollow billet before cross rollingd.sub.0 =outside diameter of hollow billet before cross rollingRt=wall thickness reduction (%), Rt=(t.sub.0 -t.sub.1)/t0.times.100Rd=outside diameter reduction (%), Rd=(d.sub.0 -d.sub.1)/d.

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 method of manufacturing a long tube having a small diameter, such as a tube for use in a heat exchanger, by cold working. A plug drawing using a pressurized lubricating oil of 500 kgf/cm.sup.2 or more accompanied by the reduction in wall-thickness is adopted as at least the final cold work. In the case where a tube having desired dimensions is not obtained by this plug drawing, subsequent free-loaded drawing can be conducted.

Abstract: A method of manufacturing a long tube having a small diameter, such as a tube for use in a heat exchanger, by cold working. A plug drawing using a pressurized lubricating oil of 500 kgf/cm.sup.2 or more accompanied by the reduction in wall-thickness is adopted as at least the final cold work. In the case where a tube having desired dimensions is not obtained by this plug drawing, subsequent free-loaded drawing can be conducted.

Abstract: An apparatus for continuous production of seam-welded steel tubing is proposed. The apparatus includes a series of shaping rolls for shaping a strip taken out from a strip coil into a tubular intermediate product, the roll series including a finpass roll group. The tubular product is subjected to seam welding under the action of a seam welder. Before arrival at the welder, a substantial main part of the preformed tubing with exception of opposing edge zones thereof is subjected to heating by a heater compensate for excess compressive stresses induced in the edge zones, while these zones are subjected to cooling by a cooler for avoiding otherwise formation of disadvantageous edge wavings which would otherwise occur.

Abstract: A process of continuous production of seam-welded steel tubing is concerned.A steel strip is taken out from a strip coil and conveyed to a tube-preshaping step including a plural of shaping roll stand positions. In the preshaping step, the strip is laterally rounded up gradually from band strip to a rough-shaped tubing until the side edges are brought into a mutually abutting state ready for seam-welding. The preshaping step is divided into a plurality of local regions. In these local regions, substantially body portion with exception of corresponding marginal edge zones of the tubing stock is separately subjected to heating. The heating width and heating intensity at these regions are increased stepwise as the tubular stock advances from upstream to downstream for avoiding conventionally appearing edge wavings and buckling undulations in the material of the steel tubing.