Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
  • B23K20/06—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating by means of high energy impulses, e.g. magnetic energy
  • B23K20/08—Explosive welding
  • B23K20/085—Explosive welding for tubes, e.g. plugging
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/04—Tubular or hollow articles
  • B23K2101/06—Tubes

Definitions

• the present invention relates to a method of carrying out explosive welding, and more particularly to a method of initiating the explosion of an explosive charge in explo- sive welding processes.
• Explosive welding is a known technique for joining to ⁇ gether primarily metallic materials.
• the materials to be welded together are placed at a given distance from one another and a layer of explosive substance is placed on one metal body, namely the cladding material.
• the explosive is detonated, preferably with the aid of a detonator cap and an initiator disc.
• Detonation of the explosive charge causes an impulse to be sent to the cladding material, which is therewith thrown against and collides with the other metal body, i.e. the so-called base material. This collision takes place progressively, as the detonation proceeds in the explosive substance.
• the cladding material will therefore strike the base material at an angle which is determined by the rate of detonation and the magnitude of the impulse.
• the present invention relates to a method of carrying out explosive welding with which the aforesaid starting non- band area is greatly reduced, and in certain embodiments of the invention totally eliminated.
• the present invention relates to a method of explo ⁇ sively welding together planar or curved workpieces, in which method a first workpiece shall be accelerated towards a second workpiece; in which an explosive charge is applied to the surface of the first workpiece remote from the second workpiece; and in which the explosive charge is brought into contact with an indicator disc so as to ini ⁇ tiate explosion of the explosive charge, the method being characterized in that the explosive charge is applied to a free edge of the forst workpiece, which is to be explosive welded to the second workpiece, and is extended inwardly over the workpiece across a region that corresponds to a subsequent joint or weld region; and in that the initiator disc comprises a thin sheet-like explosive charge having a high brisance, said high-brisance charge being applied against and parallel with the side surface of the explosive charge located on said edge of the first workpiece.
• the present invention can be applied to particular advan- tage when the cladding material is comparatively thick in relation to the desired length extension of the weld or joint in the direction of detonation of the explosive substance.
• the starting non-band area to ⁇ gether with other edge effects will be of the same magni- tude as the weld or joint length when the extension of the initiator over the length of the weld is relatively large, for instance an extension equal to twice the thickness of the cladding material.
• the invention affords particular advantages when explosive welding pipes or tubular ducting, where the pipes are jointed one to the other. In cases such as these the aforesaid starting non-band area is preferably only very slight, or non-existant.
• Figures 1 and 2 illustrate by way of example conventional techniques and also show the occurrence of the starting non-band area
• Figure 3 illustrates one embodiment of the present inven ⁇ tion
• Figure 4 illustrates a modified embodiment of the inven ⁇ tion
• Figure 5 illustrates the lower right-hand part of Figure 4 in larger scale
• Figure 6 shows the embodiment of Figure 5 subsequent to the detonation proceeding some distance along the cladding ma ⁇ terial.
• FIG. 7 illustrates another modified embodiment of the invention.
• Figures 1 and 2 illustrate, by way of example, a conven- tional technique of explosively welding a first workpiece 1 to a second workpiece 2.
• An explosive charge 3 is ap- plied to the first workpiece 1.
• An initiator disc 4 which is comparitively wide in relation to the thickness of the first workpiece 1 , is applied to said workpiece at a location thereon adjacent the explosive charge 3.
• the initiator disc 4 is detonated, a relatively large part of the first workpiece is propelled in a direction perpen ⁇ dicular to the upper surface of the second workpiece 2. Consequently, no band is established in this area, the ini ⁇ tiation area, and a so-called starting non-band area ani- fests in the manner illustrated in Figure 2 at 5.
• the first and second workpieces are brought successively into contact with one another, with the surfaces of the workpieces colliding at a certain mutual angle therebetween, as illustrated in Figure 2, such as to establish a good weld or joint 6'.
• Figure 3 illustrates an embodiment of the inventive method in which a first tubular workpiece 7 is to be explosively welded to a second tubular workpiece 8. It will be under- stood, however, that this embodiment of the inventive method can also be applied in conjuction with, for example, planar workpieces.
• the first workpiece 7 has applied thereto an explosive charge and an initiator disc.
• the explosive charge 9 is applied to a free edge 10 of the first workpiece and ex ⁇ tends inwardly over the first workpiece across an area which corresponds to the extent of a subsequent weld or joint.
• the initiator 11 comprises a thin sheet of a high ⁇ ly brisance explosive, which is applied to and parallel with the side surface 12 of the explosive charge located adjacent said edge 10 of the workpiece.
• the initiator may be a so-called explosive paste retailed, among others, by Bofors AB, Sweden, or shaped penta- erythritol tetranitrate (PETN) .
• PETN penta- erythritol tetranitrate
• the explosive charge may consist, for example, of a plastic-bound explosive substance that incorporates PETN.
• the impulse which the initiator exerts on the workpiece will prevail solely at the location of the edge 10 of the workpiece.
• the impulse generated by the explosive charge towards the workpiece upon detonation will be sufficient to establish an explo ⁇ sive weld subsequent to passing only a short distance from said edge in the detonating direction of the explo ⁇ sive charge.
• the first workpiece will be broughtprogressively- sively into welding abutment with the second workpiece after only a very short distance has been passed from said edge, when seen in the direction of detonation from the explosive charge 9.
• the initiator disc is in sheet form.
• the sheet, or disc has a thickness which is less than from one third to one fifth the thickness or height of the explosive charge, i.e. the thickness or vertical extension above the first workpiece.
• the sheet thickness is preferably less than one tenth of this height.
• the initiator 11 projects beyond the explosive charge 9 in a plane that extends at right angles to the direction of detonation 13 of the explosive charge. Detonation of the initiator 11 therewith takes place on the outwardly projecting part 14 of the initiator 11, and is effected, for instance, with the aid of a detonator cap 15. The initiator 11 will thus have a full explosive force before it strikes the explo ⁇ sive charge 9.
• the initiator 11 When the first workpiece has a cylindrical form, such as the illustrated pipe 7, and is to be explosively welded by expansion against an outwardly lying cylindrical work- piece, such as the illustrated outer pipe 8, and the explosive charge 9 is applied circumferentially around the internal surface of the first workpiece, i.e. in the man ⁇ ner illustrated inter alia in Figure 3, the initiator 11 has the form of a sheet of explosive which is initiated or detonated at the centre thereof.
• part 16 of the first workpiece 17 which is to be accelerated towards the second workpiece 18 is bevelled, or likewise tapered, at least in the region thereof where initiation of the explosive charge 19 is to be effected by means of the sheet-like initiator 20, such that the thickness of the workpiece 17 increases from its outer edge 21 in a direction corresponding to the direction of detonation 22 of the explosive charge 19.
• the thickness of the workpiece 17 is caused to increase from said edge 21 in proportion to the impulse which is direc ⁇ ted from the initiation locus 23 of the explosive charge 19 and which increases progressively in the direction of detonation 22 of said charge.
• the explosive charge 19 is shaped to conform to the surface 24 of the first workpiece 17.
• the initiator disc 20 is in the form of a very thin layer and because the bevelled part of the first workpiece located in the proximity of the initiator has a small mass, due to the bevelling of the workpiece, that part of the first workpiece 17 located beneath the initi ⁇ ator disc will be propelled at a very high speed and will collide with the second workpiece 18, at a given angle thereto, within the space of some few microseconds.
• the collision angle required to effect a bond, or weld is achieved immediately. This will also prevent the fumes or smoke generated by the'explosion from penetrating between the weld surfaces.
• the full strength of the explosive charge 19 is reached subsequent to a given extent of propagation after detonation of the initiator 20. This means that the first impulse received by the first workpiece 17 will increase progressively over this part of the propagation path. Since the first work- piece tapers, the mass to be accelerated will also in ⁇ crease progressively.
• One skilled in this art is able to adapt the length of this taper in the direction of detonation 22 to the impulse generated by a given explosive substance, so that the mass and the impulse available will correspond with each other such that a desired collision angle is obtained both in the region of initiation and downstream of said region.
• the aforesaid starting non-band area is fully elimi ⁇ nated when practicing this embodiment of the inventive method.
• This embodiment of the invention may be applied in con- junction with both planar workpieces and tubular work- pieces or similar hollow workpieces.
• the embodiment is particularly beneficial, however, when applied to gas or oil pipes where the mutually facing ends of the pipes shall be joined so as to produce a smooth transition from one internal diameter to another, i.e. without discontinu ⁇ ous changes in the internal diameter.
• this embodiment of the inventive method is particularly beneficial when the thickness of the second workpiece in the region of the weld or joint is comparatively large in relation to the length extension of the weld region in the direction of detonation.
• FIG. 6 illustrates schematically the course taken by the detonation after a short period of time has lapsed. It will be seen that a good weld 25 has been obtained right from the very edge 21 of the first workpiece 17 and that the first workpiece 17 has contacted the second workpiece 18 at a certain collision angle V. This angle is prefer ⁇ ably between 3 and 18 , and particularly between 10 and 15°.
• Figure 7 illustrates a modified form of the inventive method for application both when the first workpiece lacks a bevelled or tapered edge and when said workpiece has a bevelled or tapered edge.
• the explosive charge 26 is caused to project slightly beyond said edge 29 of the first workpiece 28, as illustrated at 27.
• the initiator disc 30 is here located against the outermost edge 31 of the outwardly projecting part 27 of the explo ⁇ sive charge 30. With this embodiment, the full effect of the explosive charge 26 is reached when detonation of the charge has proceeded in over the edge 29.
• a shield 32 in the form of a rubber or plastic cloth, can be arranged on the second workpiece 33 and over the first workpiece 28, although beneath the explosive charge 26, so as to prevent fumes or smoke from the outwardly pro- jecting part 27 entering between the subsequent weld sur ⁇ faces.
• the present invention solves the problem mentioned in the introduction, by greatly reducing the starting non-band area in the case of explosive weldswhere bevelled or tapered workpieces cannot be accepted, and by eliminat ⁇ ing fully such starting non-band areas in those cases where bevelling of the workpieces is acceptable.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Pressure Welding/Diffusion-Bonding (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

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ID=20364175

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Cited By (2)

Citations (3)

• 1986
  • 1986-04-14 SE SE8601680A patent/SE456804B/xx not_active IP Right Cessation
• 1987
  • 1987-04-07 WO PCT/SE1987/000176 patent/WO1987006169A1/en unknown
  • 1987-04-07 AU AU72848/87A patent/AU7284887A/en not_active Abandoned
  • 1987-04-09 IN IN299/DEL/87A patent/IN169543B/en unknown

Patent Citations (3)

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