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
  • B23K9/00—Arc welding or cutting
  • B23K9/02—Seam welding; Backing means; Inserts
  • B23K9/0203—Inserts
• • 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
  • B23K9/00—Arc welding or cutting
  • B23K9/02—Seam welding; Backing means; Inserts
  • B23K9/035—Seam welding; Backing means; Inserts with backing means disposed under the seam

Definitions

• the invention relates to a root insert for welding seams to be formed between constructional parts, especially that made of highly alloyed steels.
• the invention also relates to a method for welding constructional parts to each other, especially that made of highly alloyed steels, wherein a weld root is produced first and than the further layers of the weld seam is built up.
• backing straps or underlays which are placed under the weld seam to be produced on the root side. If the material of the backing straps is the same as that of the base material, they melt more or less together with the weld root but thereafter they can not be removed. This fact decreases the quality and the aesthetics of the seam, and when using this method with tubes, the remainings form stream obstacles for the medium to be forwarded in the tube. Moreover, the strength of the seam is often not sufficient.
• the straps will not melt together with them.
• the role of the straps is only to support the welding melt and to avoid the collapse of the root.
• a sincere difficulty is in that the straps are to be removed after finishing the weld seam. If this is not possible as it is often the case with tubes, the straps form stream obstacles and, thus, vortexes in the forwarded medium. Because of this, deposits will form on both sides of the straps which greatly increases the corrosion effects in this region of the construction parts being already overstrained and deterioritated by the welding. Moreover, the cleaning of the tubes with go-devi!s will be impossible, too.
• An object of the present invention is to obviate such deficiencies and to provide a root insert for welding as weI I as a method for welding with the aid of this root insert, with which the geometrical shape of the seam can be determined in advance, the heat transfer to the constructional parts to be welded can be regulated during the welding operation, the protective atmosphere for highly alloyed steels wil l no more be necessary on the root side of the parts, and with which the welding operation can be simpler, easier and the seam wiII have a better quality.
• the improvement of the root insert according to this invention is in that the insert has a root portion and a melting web connected to the root portion as well as shoul ders on both sides of the web, which, in mounted position of the insert, lie on the root-side surfaces of the constructional parts to be welded together.
• the root portion is provided, on the outer surface of the root portion being opposite to the web, with a slag-forming coating reaching until the plain defined by the shoulders.
• the mass ratio of the root portion to the web is at least 2:8 and in the case of hot coating, the mass ratio of the root portion to the web is not more than 3:7.
• the root insert is made of the same material as the welding electrode used for welding the constructional parts and/or as the constructional parts themselves.
• the Improvement of the method for welding of .constructiona parts according to this invention is in that before producing the weld root, a root insert is placed in between the constructional parts to be welded together, especially root insert according to any one of Claims 1 to 5, and thereafter the weld root is produced by melting the web of the insert.
• one of the shoulders of the root insert is lain on the root sided surface of one of the constructional parts to be welded together and thereafter, the other constructional part is lain on the other shoulder of the insert.
• the first filling layer of the weld seam is simultaneously produced in form of a twin seam.
• Fig. 1 illustrates a preferred realization of the method of this invention with the help of a cross section of a preferred embodiment of the root insert as in the invention
• Fig. 2 shows a root weld produced with the help of this invention.
• a root insert 3 is provided which, in this particular case, is ring shaped. Root insert 3 has a root portion 4 and, connected to this, a web 5. As it will be described later in more detail, shoulders 6 are lying on the surfaces of tubes 1 and 2 in their mounted position before welding. Shoulders 6 are provided on both sides of web 5 at its junction to. root portion A. In this way, root insert 3 has a stubby mushroom-shaped form turned upside down. The vertical leg of the mushroom is web 5 and its pileus formes root portion A. On the brim of the pileus, the ends of tubes 1 and 2 Iie on as shown in Fig. 1.
• the two side surfaces of web 5 are adjusted to the forms of the finished tube ends. Since, in this particular case, root insert 3 is used for welding tubes 1 and 2 made of highly alloyed, austenitic steel, the welding seam to be formed is to be protected against the ambient air. According to the invention, this is solved by providing a slag-producing coating 7 rather than by argon gas scavenge as usual with the previously known solutions.
• This coating 7 covers the outer surface of root portion A being opposite to web 5 until the plain defined by shoulders 6. In this way, the ends of coating 7 form elongations of shoulders 6 lying on the root-sided surface of tubes 1 and2. Followingly, coating 7 also contacts this root-sided surface of tubes 1, 2 and in the mounted position of root insert 3 as shown in Fig. 1, ambient air cannot creep in to the weld seam under production from the root side.
• the material of this slag-producing coating 7 on root insert 3 can be the same as that of the welding electrode with which the welding is carried out.
• Coating 7 is only needed where this is necessitated by the quality of the materials to be welded as wel l as of the welding seam to be made.
• root insert 3 without any coating can be provided and used, too.
• coating 7 serves, at the same time, as a support for the weld seam during the welding operation and, practically, it eliminates the danger of collapse of the melt. Therefore, the use of root insert 3 having coating 7 on it can be reasonable in such cases, too, in which this would not be indispensa ble because of the materials to be welded.
• a root seam 8 produced according to the invention is shown in cross section.
• This root seam 8 is in fact a twin seam, since not only a seam root 9 in strict sense of the word but also a first filling seam layer 10 is formed.
• the ends of tubes 1 and 2 must be shaped for having the proper form for welding as usual. Thereafter, the ring-shaped root insert 3 wiI I be placed on the end of, let's say, tube 1 by lying shoulder 6 of root insert 3 on the root-sided surface of tube 1 and arranging web 5 radially outwards. After this, the other tube 2 will be placed on root insert 3 for lying the root-sided surface of tube 2 on the other shoulder 6 of root insert 3.
• the longitudinal axis of tube 2 should be brought into coaxial position with that of tube 1, and tube 2 should be pushed in this coaxial direction onto shoulder 5. Having carried out this, sharp edges of tubes 1 and 2 lie between shoulders 6 and web 5 along the whole peripheries of the tubes 1, 2. But with this, the centring of tubes 1 and 2 is also carried out. It is guarantied that the distance between the ends of tubes 1, 2 is constant along the whole periphery which has a striking importance with regard to the welding seam to be produced.
• tubes 1 and 2 After arranging tubes 1 and 2 on root insert 3, the welding can be started by melting down web 5. If tubes 1 and 2 can be pressed towards each other and, thus, their secure position on root insert 3 can be maintained constantly, the provisional fixing of tubes 1, 2 to each other by melt ing web 5 in some places around the periphery, the so called stepping will not be necessary. But if against all, this fixing is carried out, conventional tack weld will not come into being.
• Root portion A of root insert 3 formes seam root 9 whilst the additional material for the first filling seam layer 10 is provided by web 5.
• the heat being necessary for melting is transferred through web 5 and the impacting tube edges to the root.
• the heat amount should be sufficient for totally melting to each other the edges of tubes 1 and 2 and root seam 8 as weI I as for producing slag from coating 7 on the root side. Since the heat transfer occurs predominantly through web 5 and the tube edges, the form of web 5 as well as the mass ratio of web 5 to root portion A have eminent importance.
• Dominant factor is the heat dissipation of tubes 1 and 2 which can be different for the two tubes 1, 2.
• the form of web 5 and the mass ratio of web 5 to root portion A must be determined with great care.
• the mass ratio between the mass of web 5 and root portion A is preferably at least 2:8 but the root portion A in case of need can be smaller in relation to web 5.
• this mass ratio should be maximum 3:7, i.e. the difference can be smaller between the masses of web 5 and root portion A.
• web 5 has a heat regulating function by being formed as in this invention: it makes possible the necessary heat transfer but it counteracts to the burning of the materials of tubes 1, 2.
• coating 7 gets melted and forms the slag coating protecting the seam under production from the influences of the ambient air. Therefore, a protec tive atmosphere on the root side is absolutely unnecessary, even with the most sensitive materials.
• the root insert as in this invention can be used not only for tubes. Welding seams with optional form and tracing can be made with the help of the root insert according to this invention but the root insert must have always the same shape as the welding seams.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Mechanical Engineering (AREA)
• Butt Welding And Welding Of Specific Article (AREA)
• Arc Welding In General (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 1986
  • 1986-09-30 JP JP50512586A patent/JPS63501488A/ja active Pending
  • 1986-09-30 WO PCT/HU1986/000052 patent/WO1987001982A1/en not_active Application Discontinuation
  • 1986-09-30 EP EP19860905916 patent/EP0244436A1/de not_active Withdrawn
• 1987
  • 1987-06-03 FI FI872473A patent/FI872473A/fi not_active IP Right Cessation

Non-Patent Citations (1)

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