SU747584A1 - Method of connecting different metal tubes - Google Patents

Description

The invention relates to a method of joining pipes by heating and squeezing in vacuum, in which pipes are assembled into a telescopic connection, and can be used in power and chemical engineering, in particular in heat exchangers in the manufacture of adapters for connecting pipes from dissimilar materials.

The known method of permanent connection of rotation shells by crimping when heated to the temperature of plastic deformation, in which the joint is obtained through an intermediate layer of a more ductile material than the materials j of the connected pipes 1J- The disadvantage of this connection method is that in conditions of high operating temperatures under the action of thermal on. stitching occurs a creep npoueqc 20 soft layer, which can lead to the destruction of the joint.

Known to interconnect the connection of adapters by explosion 2, in which

An intermediate layer is used, which has a lower melting point than the temperature of the adapter. The main disadvantage of this method is that due to the Rebnnder effect (this is the so-called adsorption decrease in strength), the phase of the phase accelerated at the grain boundaries leads to the opening of the adapter.

There is also known a method of connecting the threads of pipes from dissimilar metals with different linear expansion coefficients by heating in vacuum and squeezing, in which the internal is made of metal with a smaller rassenny phenylphenol and pressed into the thread of the pipe by means of a conical mandrel moved along the internal the pipe at the temperature of formation between the parts to be welded by the eutectic gf-layer. The disadvantage of this method is that it does not provide an adequate working capacity of the middle at high temperatures. This happens because, after welding, the fragile eutectic interlayer forms a gesture: 1W skeleton, which during heating and cooling of the adapter due to thermal stresses easily collapses. This leads to a loss of vacuum density adapters. The aim of the invention is ET. increase in reliability and performance under conditions of high temperatures as a result of smoothing (damping) control creep-plastic deformations caused by thermal stresses during the operation of adapters. This goal is achieved by TeivJ that the connection of dissimilar pipes is ejected through an intermediate layer, which is made of damping material and is applied to the surface of one of the pipes to be connected with a layer constituting 30 -10% of the cross-sectional area thread. The use of this method will improve the reliability of the operation of the compound under conditions of high temperatures. FIG. 1 shows a section of the inner tube with an intermediate layer applied; in fig. 2 - thread, cross section; in fig. Figure 3 shows the zone of junction (the arrow indicates the direction of pressing the segments Tj) y6 using a tapered mandrel. The coupling is carried out as follows. Initially, intermediate layer 2 was applied to one of the pipes, having damping properties. In this case, welding, electric contact welding, powder metallurgy methods can be used. Then the thread 3 is cut so that the cross-sectional area of the intermediate layer 2 is 30-60% of the cross-sectional area of the tooth 3 of thread. Next, the similar thread profile 3 is performed on the druths of pipe 4 and screwed them along the thread, and the pipe is made of a material with a lower linear expansion coefficient. The finished billet is heated to a temperature at which an electrical interlayer 5 forms in contact, and the ester is cone-shaped 6 slanted through the inner tube 1. Precoat bore is covered with one of the known protective coatings to prevent the dorn 6 from catching pipes 1. After cooling, the workpiece is machined to the dimensions of the adapter on a lathe and control templates are cut out to estimate the thickness of the eutectic interlayer 5. Example. Adapters are made from an alloy of system Zh -2.5 Nb with steel OH18H1OT with diameters and pipe thicknesses, respectively F 88x4, 0 95xS. As an intermediate layer, pure niobium of electron-beam melting is used, the wire from which with a diameter of 1 mm is directed by electron beam welding to the outer surface of an alloy pipe, 5Nb, into an undercut with a depth of 1.2 mm on an ELU-5 unit. Then, M88x2 threads are cut on this surface of the pipe in such a way that the cross-sectional area of the intermediate layer is -30% of the cross-sectional area of the tooth of the thread. A similar thread is made on the pipe segment g of steel OH18H1OT. The pipe sections are screwed, placed in a welding unit of type A30608, where they are heated to the temperature of formation of the eutectic interlayer (910 C) and pressed in with a tapered mandrel. The quality of the compounds is assessed by heat pumping with heating and cooling in vacuum from 85 ° to ZEP, and the connections are checked for vacuum density by a helium leak detector. It has been experimentally established that the compounds withstand the greatest number of heat pumps when the cross-sectional area of the intermediate layer is 30 -60% of the cross-sectional area of the thread tooth w. If the thickness of the Nb damping layer is less than 3 (V) about the area across the thread's tooth cross-section, then the optics are partially violated: conditions of external damping of the compound under high temperature conditions, if it is greater than 6O%, then the optical conditions of external damping in the low temperature range are violated . The use of this method of manufacturing adapters will increase the heat resistance of compounds compared to those adapters that are made according to method C approximately 2 times. In the manufacture of a pilot batch of adapters, rejects are reduced by Z-35%.

Formulas

the invention

The method of joining pipes from dissimilar metals with different linear expansion coefficients, including the operations of performing screw threading on the joined surfaces of pipes, installing a pipe made of metal with a lower coefficient of linear expansion into a pipe made of metal with a large linear expansion coefficient, heating in vacuum and squeezing by distributing a conical mandrel at the temperature of formation between the connected parts of the eutectic interlayer, characterized in that, in order to increase the reliability of the connection

under high temperature conditions, before making a thread, an intermediate layer of a material with damping properties with respect to the bonded metals is applied to the surface of one of the pipes, the intermediate layer being 30 -60% of the cross-sectional area of the thread,

Information sources,

0 accepted during examination

1, USSR Author's Certificate No. 239194, cl. B 21D 39 / O4, 1959,

2, USSR Copyright Certificate №545434, class, B 23 K 19 / OO, 1975,

3, USSR author's certificate

No. 202404, Cl, B 23 K 31 / O6, 1957. (prototype). / 2

Claims (1)

Claim A method of joining pipes of dissimilar metals with different linear expansion coefficients, including screw cutting on the connected surfaces of the pipes, installing a metal pipe with a lower coefficient of linear expansion in a metal pipe with a high coefficient of linear expansion, heating in vacuum and squeezing by distributing with a conical mandrel at the temperature of formation between the connected parts of the eutectic layer, which is characterized in that, in order to increase the reliability of the connection in Under high temperatures, before threading, an intermediate layer of material with damping properties with respect to the metals being joined is applied to the surface of one of the pipes, while the intermediate layer is 30-60% of the cross-sectional area of the thread.