RU2635123C1 - Dissimilar materials bonding with electronic beam technique - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: grooves (3) are made in the detail, which is made of the low-melting material. The protrusion (4) is made in the detail, which is made of the heat-resistant material, to match with the groove. The ruled welding surfaces are obtained in the joint zone. The groove (3) and the protrusion (4) are fused together when assembling the joint zone, providing the hard contact in between. The scarf butt joint with the variable clearance between the ruled welding surfaces in the shape of the toe-in angle is formed. The brazing is carried out with the electronic beam (5). The beam (5) is moved in reference to the edge towards the low-melting detail (1) over a fixed distance. The low-melting detail (1) is melted and the permanent joint is formed after the crystallization. The cylinder details that are made of the dissimilar materials are connected to each other with the ring seam. The plain details that are made of the dissimilar materials are connected to each other with the longitudinal seam.

EFFECT: welding stress and deformations reduction, expulsion from the weld area of the intermetallic phases, which enhances the strength and the tightness of the details permanent joint.

8 cl, 4 dwg, 1 tbl

Description

Technical field

The invention relates to the field of welding production, in particular to a method for joining dissimilar materials with an electron beam. The invention can be used in mechanical engineering, aircraft manufacturing, in nuclear energy and other industries.

State of the art

A known method of laser welding of parts from dissimilar metals, described in the patent of the Russian Federation No. 2415739, priority 16.06.2009; published April 10, 2011; IPC: B23K 26/40, B23K 9/23, B23K 33/00 (2006.01); authors V.V. Zvezdin, I.Kh. Israfilov, D.E. Veliev. The method consists in the fact that the plane of the butt joint of parts of dissimilar metals is made oblique tangentially to the segment of the heat affected zone of the weld. Laser radiation is focused on a more refractory material at a distance from the butt plane. The angle of inclination of the plane of the butt joint and the focusing distance are calculated from the condition of ensuring the absence of evaporation of fusible material.

The disadvantage of this method is the tendency to accumulation of welding stresses and deformations due to uneven heating of parts with different coefficients of thermal expansion. This can lead to a decrease in the strength of welded joints. In addition, when the heat flux of the beam is shifted to a more refractory material, heat input with a higher energy density is required to form the weld.

A known method of welding pipes from dissimilar materials, described in the copyright certificate No. 759272, priority 30.11.1978, published 08.30.1980; IPC: B23K 28/00, B23K 33/00; authors V.Ya. Elizarov, A.V. Sheptukhin. The method consists in the fact that two pipes of fusible and refractory material are welded. At the end of the refractory pipe, annular grooves are made, butt pipes are assembled and welded. In the welding process, the grooves are filled with welding rollers having a chemical composition similar to a low-melting material, and then the pipes are welded. Due to the additional adhesion on the welding surface, a stepwise engagement of the lock type is created as a result of the filler rollers being mated with the grooves.

Multipass pre-surfacing and subsequent welding require thorough cleaning and protection of the previously deposited metal during subsequent passes from oxidation in the atmosphere of atmospheric gases. The disadvantage of this method is the increase in the number of control operations and the complexity of the weld. The implementation of the air cavities in the form of technological grooves also increases the complexity of manufacturing the connection. In addition, the subsequent filling and welding passes cause heating of the fusion boundaries of dissimilar materials with the appearance of significant internal welding stresses, which, with the concomitant formation of brittle intermetallic phases due to phase transitions caused by heating, can lead to the delamination of previously deposited rollers due to the difference in CTE.

As a prototype for the proposed method, the method of welding pipes was described, described in the copyright certificate No. 573298, priority 04.03.1976; published on 09/25/1977 .; IPC B23K 33/00, B23K 31/06; authors L.K. Andreyanov, V.Ya. Elizarov, Yu.N. Kozin, V.V. Krivonogov, M.G. Kurganov-Nosov, N.I. Lomaev, A.V. Sheptukhin. According to the method, weldable parts are assembled, a part of fusible material is placed on the outside, and a part of refractory material is placed on the inside, the external part is heated in the connection zone with a concentrated energy source. The molten, more fusible metal fills all the bumps, and when the seam cools down, it shrinks and undergoes strong compression.

The disadvantage of this method is the prolonged interaction of the molten metal with a more fusible part with the refractory metal of the inner pipe, which can lead to the formation of brittle intermetallic phases. Long interaction is due to the need to completely fill the grooves with filler material on the inner part and the cutting edges of the outer part. In addition, the long-term influence of the high-temperature thermal welding cycle can lead to excessive accumulation of welding stresses and strains. In the process of heating and cooling, parts are deformed (expansion of pipes with subsequent shrinkage), which can lead to a violation of the requirements for ensuring high precision manufacturing of structures and a violation of operational characteristics. Also, in the case of several grooves, shrinkage from each subsequent seam, which is mainly a seam of the upper low-melting part, will act “on the cut” on the previous seams, until they are peeled off from the refractory part. Thus, the strength and tightness as a whole are reduced.

Disclosure of invention

The problem to which the invention is directed, is to increase the strength and tightness of the integral connection of parts from dissimilar materials.

The technical result achieved in solving this problem is to reduce welding stresses and strains, to exclude intermetallic phases from the weld zone, which increase brittleness, hardness and tendency to crack formation in the weld.

The technical result is achieved by the fact that in the method of joining dissimilar materials with an electron beam containing the assembly of parts with the placement of the part from the fusible material from the outside, heating it in the connection zone with a concentrated energy source, according to the invention, a groove is made on the part from the fusible material under which the part made of a refractory material perform a protrusion. Combine a groove and a protrusion, providing tight contact between them. At the same time, the surfaces to be welded are brought together by a skew joint, with a variable gap between them in the form of a convergence angle. Welding is performed by an electron beam, which is displaced relative to the edge towards the low-melting part by a fixed amount. The fusible part is melted and a permanent connection is formed after crystallization.

The combination of essential features provides a technical result - reduction of welding stresses and deformations, exclusion of intermetallic phases from the weld zone, which increase brittleness, hardness and tendency to crack formation, which makes it possible to solve the problem of increasing the strength and tightness of one-piece parts from dissimilar materials.

If the parts to be welded have a cylindrical shape, then a centering groove is made on the parts of fusible material, under which a centering ring protrusion is made on the cylindrical part of refractory material to connect the parts with an annular seam.

If the parts to be welded have a flat shape, then a straight groove is made on a flat part of fusible material, under which a straight projection is made on a flat part of refractory material to connect the parts with a longitudinal seam.

The manufacture of a groove on a low-melting part and a protrusion on a high-melting part simplifies assembly, ensures the exact location of the parts relative to each other.

When assembling parts, they provide tight contact between the groove and the protrusion in the lower zone of further welding. Due to this, during welding, directed heating of the lower part of the refractory part is carried out due to heat transfer during melting of the low-melting part. At the same time, the upper part of the refractory part is heated in the area of the skew joint. The molten metal of the low-melting part is in contact with a sufficiently heated refractory part in the area of the skew joint. This ensures good wetting and interaction of the welded parts without the formation of intermetallic compounds. This allows you to achieve the necessary temperature distribution in the weld zone, which affects the reduction of welding stresses and deformations, the exclusion of intermetallic phases from the weld zone and improves the quality of the formation of the welded-soldered seam.

To increase the area, improve wettability in the area of the skew joint contact and improve the quality of one-piece joints, a gap between the welded surfaces of low-melting and refractory parts is realized in the form of a convergence angle. The convergence angle of the welded surfaces with low-melting and high-melting parts does not exceed 2 °.

At an angle of convergence of more than 2 °, an incomplete filling of the skew joint cutting is possible, the formation of an incomplete seam with the appearance of stress concentrators, which can negatively affect the operability of the structure as a whole.

When the convergence angle is less than 2 °, or the complete absence of a gap, there is an increased heat removal from the low-melting part to the high-melting part along the border of the joint. In this case, excessive heat input from the welding source is realized, which, when combined with low-melting and high-melting parts, can lead to intensive formation of intermetallic compounds and an increase in stresses in the weld.

To reduce linear and angular deformations during welding of dissimilar materials, it is advisable to use such a welding method with a low heat input value as electron beam welding or pulsed laser welding.

The parts are welded with an electron beam in one pass and thereby exclude overheating and warping of the parts to be welded, as well as the accumulation of thermal stresses and the likelihood of the formation of intermetallic compounds. In addition, performing soldering in one pass reduces the complexity and cost of the welded-solder seam.

Before welding, the electron beam is shifted relative to the edge towards the low-melting part by a fixed value of 1.5 ... 2.0 mm. When the electron beam is displaced by a distance of less than 1.5 mm, excessive melting of the refractory part is possible, which can lead to more intense diffusion of elements and the formation of intermetallic phases. When the electron beam is displaced by a distance of more than 2.0 mm, the configuration deteriorates and the tightness of the weld-solder seam is impaired, since the volume of molten metal of a low-melting part may not be enough to wet the surface of the refractory part and form a high-quality welded-solder joint.

Local melting of the fusible part is carried out with its subsequent spreading over the surface of a more refractory material and the formation of the compound during further crystallization. That is, the low-melting part is melted, the lower part of the refractory part is heated to a high temperature and the upper part of the refractory part is warmed up, the surfaces of the joint are wetted by the melt, the melt crystallizes and a welded-solder joint is formed. The resulting connection provides a joint seal and fixation of one part relative to another.

Thus, this method ensures the absence of brittle intermetallic phases in various zones of the joint, which can lead to destruction upon accumulation of internal welding stresses and deformation of the joint. This increases the strength and tightness of one-piece connection of parts from dissimilar materials.

In the above analogues characterizing the prior art, there is no tool that is inherent in all the features of the invention expressed by the proposed formula so that all the features of a previously known tool are contained in one source of information. This confirms the compliance of the claimed invention with the condition of "novelty."

The information contained in the prior art, by combining, modifying or sharing cannot create the proposed invention. From the prior art, no solutions have been identified that have features that match the distinguishing features of the subject invention. It was concluded that the invention does not explicitly follow for a person skilled in the art. This confirms the compliance of the claimed invention with the condition of "inventive step".

Brief Description of the Drawings

In FIG. 1 shows a cross section of the parts to be welded.

In FIG. 2 shows the connection of parts before welding.

In FIG. 3 shows a cross section of a welded-solder joint (Ti-Ta).

In FIG. 4 shows a cross section of a welded-solder joint in reflected electrons (Ti-Ta).

Embodiments of the invention

In the manner described in the patent, both flat and cylindrical parts can be welded. Next will be described one of the embodiments of the invention - welding of parts from dissimilar materials in the form of tube blanks. As the material of the low-melting part, titanium (Ti) with impurities Al, Si, V, Zr, Mo is used. The refractory part is made of tantalum (Ta).

As shown in FIG. 1, a fusible part 1 and a refractory part 2 are involved in the soldering process. A groove is made on part 1. A groove 3 is made on part 2. A protrusion 4 is made under the groove 3 of part 1.

Electron beam welding is as follows. First, assembly of part 1 with part 2 is performed. In FIG. 2 shows the connection of part 1 with part 2 before welding. Before assembly, parts 1 and 2 are sonicated in ethanol. This brings the welded surfaces to the required cleanliness and, thus, eliminates the influence of contaminants on the quality of the weld. Next, parts 1 and 2 are installed in an assembly-welding fixture (not shown in FIG. 2), which ensures tight contact of the groove 3 of part 1 with the protrusion 4 of part 2 in the lower zone. The assembly-welding fixture provides unhindered access of the electron beam 5 to the zone welding soldering. In the upper zone, a gap between the surfaces to be welded is realized in the form of an angle of convergence of parts 1 and 2. The angle of convergence of the surfaces to be welded of part 1 and 2 does not exceed 2 °.

Next, the electron beam 5 is displaced relative to the edge toward the low-melting part by a fixed value of 1.5 ... 2.0 mm.

Welding is performed with the melting of part 1 and directed heating of the protrusion 4 of part 2 in the lower contact zone with the groove 3 of part 1 and the surface of the braid joint in the upper part of part 2. The lower part is heated by refractory part 2 due to heat transfer during melting of low-melting part 1. At the same time provide heating of the upper part of the refractory part 2 in the area of the skew joint connection of parts 1 and 2.

The molten metal of part 1 spreads over the heated surface of part 2 and forms, upon further crystallization, a welded-solder seam 6, as shown in FIG. 3. Weld parts 1 and 2 with an electron beam in one pass, thereby eliminating overheating and warping of the welded parts, as well as the accumulation of thermal stresses and the likelihood of the formation of intermetallic compounds.

After crystallization of the weld 6, an integral connection of parts 1 and 2 is formed. According to the results of a metallographic analysis of the welded-solder weld 6, no internal defects were detected in it. A welded-solder seam 6 is formed without the formation of intermetallic compounds, as shown in FIG. four.

According to the results of x-ray microanalysis, the chemical elemental composition of the welded-soldered seam 6 is determined, shown in table 1.

In the welding process, metals interact during the melting of part 1 and heating of part 2 with mutual diffusion of elements.

In FIG. 4 shows a cross section of a welded-solder joint in reflected electrons (Ti-Ta). The image obtained in reflected electrons along the weld boundary 6 showed no defects, brittle intermetallic compounds are absent.

As a result of the experiments, it was confirmed that during electron-beam welding of parts 1 and 2 from dissimilar materials, the welded-soldered seam 6 has no defects. That is, the minimum heat input during soldering ensures minimal deformation during heating and shrinkage and eliminates the formation of brittle intermetallic phases.

Industrial applicability

The most effective is the use of the proposed method in structures for critical applications, where high demands are made on ensuring the tightness of ring and longitudinal welded joints. And also where there is a need to connect parts of dissimilar metals in the construction, and increased demands are placed on the accuracy of their manufacture, in general, and on the quality of welded-soldered joints, in particular.

The proposed design of the welded-solder joint provides a technical result, which consists in obtaining a welded-solder joint without the formation of stable intermetallic phases and a decrease in welding stress and deformation.

In General, the considered embodiment of the invention can be implemented on existing equipment using existing materials. This shows its performance and confirms industrial applicability.

Claims (8)

1. The method of connecting parts from dissimilar materials, including assembling the junction of parts of fusible material with a part of refractory material and heating the joint with melting the part of fusible material, characterized in that a part is made of fusible material to make a groove under which parts of refractory material perform a protrusion, with obtaining oblique welded surfaces in the joint zone, and when assembling the joint, the welded surfaces of the groove and protrusion are combined with the formation of a braid joint with the gap between the oblique welded surfaces in the form of a convergence angle, then the joint is heated with a concentrated energy source, which is displaced relative to the joint towards the low-melting part by a fixed amount, the low-melting part is melted and an integral welded-soldered joint is formed. 2. The method according to p. 1, characterized in that they connect the cylindrical parts of dissimilar materials with an annular seam. 3. The method according to p. 2, characterized in that an annular centering groove is made on the parts of the fusible material, under which a centering annular protrusion is performed on the parts of the refractory material. 4. The method according to p. 1, characterized in that they connect the flat parts of dissimilar materials with a longitudinal seam. 5. The method according to p. 1, characterized in that the angle of convergence of the surfaces to be welded with low-melting and high-melting parts does not exceed 2 °. 6. The method according to p. 1, characterized in that the parts are welded with an electron beam in one pass. 7. The method according to p. 1, characterized in that the parts are welded with a laser beam in one pass. 8. The method according to p. 1, characterized in that the concentrated energy source is displaced relative to the welded joint to the side of the low-melting part by 1.5-2.0 mm.

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