RU2784438C1 - Welding method for aluminum alloy parts - Google Patents

Abstract

FIELD: welding.

SUBSTANCE: invention relates to a method for welding parts made of aluminum alloys and can be used in mechanical engineering, aircraft building, nuclear energy, petrochemical, gas and other industries. The protrusions of the edges of parts with a thickness d from 3.0 to 6.0 mm are performed. The wall thickness of the parts is t≥8.0 mm, d/t≤0.75. The length of the protrusion of the edges L<(3d+Δ), where Δ is the allowance for shrinkage of the butt weld. The edges of the parts are cut with the angle of cutting the edges in the range of 65°<α<75°. One-pass welding of the butt joint in an inert gas environment is performed by automatic arc welding. Form the root of the seam on weight with the width of the seam B<L. The root of the seam is cooled. The space between the bevels of the two edges is filled with beads by multi-pass arc welding in a mixture of shielding gases using a filler wire. In addition, the first bead is centered relative to the joint. Each subsequent roller after the first is shifted relative to the previous one by 40-60% of its width. The first six rolls are made after cooling each previous one to room temperature, and starting from the seventh, the rolls are made without intermediate cooling.

EFFECT: improving the quality of welded joints of parts by reducing the heating zone, eliminating welding defects, temperature-time separation of welds filling the space between the bevel edges of two parts, and eliminating the effect of filler beads on the formation of the root of the weld.

8 cl, 5 dwg

Description

Technical field

The invention relates to the field of welding production, in particular, to a method of arc welding with a non-consumable electrode in an inert gas environment of longitudinal and circumferential welds of extended structures of variable cross section, which require high-quality welded joints with through penetration. The invention can be used in machine building, aircraft building, nuclear energy, petrochemical, gas and other industries.

Prior Art

The known method is described in RF patent No. 2563793 "Method of welding pipelines from high-strength pipes with controlled heat input", IPC: V23K 31/02, V23K 33/00, V23K 9/235, V23K 101/10; application No. 2014110685/02, priority 03/20/2014; published on September 20, 2015, authors: Revel-Muroz P.A. (RU), Chentsov A.N. (RU), Kolesnikov O.I. (RU), Goncharov N.G. (RU), Zotov M.Yu. (RU), Shoter P.I. (RU).

In a method for welding pipelines from high-strength pipes with controlled heat input, including cutting the connecting ends of pipes for welding, assembling welding elements, preparing the edges of welded elements of welded joints, welding elements with an annular butt using arc welding along the entire perimeter of the pipe with control of the parameters of the thermal cycle of welding, when In this case, the control of heat input into the metal is carried out in the range from 0.8 to 1.2 kJ / mm, the preparation of edges for welding is carried out with the ratio of the total width of the grooves to the thickness of the welded elements in the range from 1.3 to 2.0, preheating is carried out at temperature from 170 to 200°C, the imposition of welded beads forming a butt welded joint is implemented with a ratio of the thicknesses of the previous and subsequent bead from 1.0 to 2.0, each pass forming the weld is performed by parallel imposition of two beads, with every second the roller is annealing and completely covers the first roller; the process is carried out with maintaining the interlayer temperature between the superimposed weld beads from 170 to 220°C, and cooling of the welded joint at a rate of 150-200°C per hour is ensured by covering with heat-insulating belts, which are removed after reaching the joint temperature of 50°C.

Essential features that are common with the features of the technical solution: cutting the connecting ends for welding, assembling the welding elements, preparing the edges of the welded elements of welded joints, welding the elements using arc welding.

The disadvantages of this method include the fact that the quality of the formation of the root of the first bead is not ensured, as well as the unacceptability of the technology for applying beads from electrodes for welding steels to welding aluminum alloy. Also, the lowest possible heat input is not ensured due to the use of heating during welding and the parallel imposition of two rollers at once, which excessively increases the reinforcement of the reverse roller.

The known method is described in RF patent No. 2229968 "Method of welding joints in the manufacture of pipelines", IPC: V23K 31/02, V23K 101/06; application No. 2003105518/02, priority 27.02.2003; published on 10.06.2004, authors: Khomenko V.I. (RU), Kuchuk-Yatsenko S.I. (RU), Kazymov B.I. (RU), Zagadarchuk V.F. (RU), Bykovets K.P. (RU).

The method for welding pipe joints in the manufacture of pipelines is carried out as follows: cutting the edges of the ends of the pipes to be welded with blunting, assembling the joint, centering, welding first the root weld and then filling the remaining part of the groove with electric arc welding. In this case, the root weld is performed by electric flash welding without lining and immediately, without cooling, the remaining part of the groove is filled with semi-automatic welding with flux-cored wire or automatic welding in shielding gases. Cutting edges (cutting angle does not exceed 30°) is performed with a blunting thickness d at d/S<0.5, where S is the pipe wall thickness. The inner surface of the pipes is machined to a certain length. Burr from the inner surface after the root weld is removed by mechanical finishing.

Significant features common with the features of the technical solution: cutting edges with blunting, assembling the joint, welding first the root weld and then filling the remaining part of the groove with electric arc welding.

The disadvantage of this method is that the quality of the formation of the root of the first seam is not ensured and access to the inside of the pipe is required for its completion. At the same time, the internal groove made reduces the strength of the welded joint relative to the working wall of the pipeline. For electric flash welding of aluminum alloys, significant upsetting rates (150 mm / s and higher) are required, which are higher than when welding mild steel. The upsetting pressure for aluminum alloys can reach 196.1-215.7 MPa. Therefore, their welding requires machines of relatively higher power with automatic control. In addition, the continuity of welding after the root pass increases the heat input, which also contradicts the minimum heat input requirements and increases the sag of the root weld.

As a prototype, the technical solution described in the patent of the Russian Federation No. 2355540 "Method of welding circular joints of pipes", IPC: V23K 28/02, V23K 33/00, V23K 31/02, V23K 101/06; application: 2006142988/02, priority: 04.12.2006; published on May 20, 2009, authors: Baranov V.N. (RU), Bednyakov V.V. (RU), Grezev A.N. (RU), Kazakevich I.I. (RU), Khomenko V.I. (RU).

In the method of welding circumferential joints of pipes, which includes cutting with blunting the edges of the ends of the welded pipes of a section of constant section, performing cutting with blunting the edges of the ends of the welded pipes of a section of variable section, assembling the joint, centering, welding the root weld by electrocontact flash welding and filling the remaining part of the groove at a temperature welded by electric contact welding of the root weld, according to the invention, the cutting with blunting of the edges of the ends of the pipes to be welded of a section of constant section is performed with a thickness d depending on the material and thickness s of the pipe wall in accordance with the ratio d/s=0.15-0.6 and length L=( t+Δ+l _op /2+l _os /2), where d is the thickness of the groove, s is the wall thickness of the pipes to be welded, t is a value depending on the method of filling the remaining part of the groove, Δ is the maximum standard value of the oblique cut of the ends of the pipes, l _op - the total length of the melted pipe sections in the process of electric contact welding of the root weld, l _os - total d the length of the upset pipe sections in the process of electric contact welding of the root weld, which is equal to the thickness of the molten metal at two ends immediately before upsetting, the cutting of the edges of the section of variable section is carried out with an angle α=0-30°, and the filling of the remaining part of the groove is carried out by laser welding from the temperature of the welded electrocontact root welding.

Significant features common with the features of the technical solution: performing a groove of a constant section, assembling the joint, welding the root weld with electric contact welding, flashing and filling the remaining part of the groove.

The disadvantage of this method in relation to the claimed is that with this method of welding steel pipes, the internal flash is practically absent and no modification is required. However, when welding the root weld of an aluminum alloy, “reinforcement” is required, the formation of a back bead with a smooth transition to the base metal to ensure uniform strength and eliminate the effect of stress concentrators in the form of sharp transitions in the weld root zone. Given the significant shrinkage during solidification of the weld of aluminum alloy parts, as well as the high coefficient of linear expansion, the use of electric flash welding to make the root weld can lead to significant permanent deformations. Another disadvantage is the use of laser welding with remelting of the root weld of electrocontact welding, which is problematic in the formation of the root of the through weld of aluminum alloys, which requires protection from the external gaseous environment and has a tendency to spatter during the formation of the melt pool and tightening of the root part. Also provided by the method, the continuity of welding after the root weld increases the heat input, which contradicts the requirements for the minimum heat input when welding aluminum for high-quality formation of the root weld. In the length formula L, the value of the remaining part of the groove (a section of constant section) should not be less than the outer width of the root weld, which, when welding with a heat-conducting seam, is up to 3 times the thickness of the joint.

Disclosure of invention

The task to be solved by the claimed invention is to ensure the equal strength of the weld and the base metal while eliminating stress concentrators at the root of the weld, and reducing the shrinkage of the welded joint.

The technical result achieved in solving this problem is to reduce the heating zone; in the exclusion of welding defects; in the temperature-time separation of the seams that fill the space between the bevels of the edges of the two parts, and in the exclusion of the influence of the filling beads on the formation of the root of the seam.

The technical result is achieved by the fact that in the method of welding parts made of aluminum alloy, including the implementation of the protrusion of the edges of the parts, cutting the edges of the parts with giving them a bevel, assembling the joint of the protrusions of the edges, welding the joint, filling the space between the bevels of the edges of two parts, according to the invention, the protrusions of the edges of the parts perform with a thickness d from 3.0 to 6.0 mm with a wall thickness of the parts t≥8.0 mm in accordance with the ratio d/t≤0.75. The length of the protrusion of the edges satisfies the condition L<(3d+Δ), where Δ is the allowance for shrinkage of the butt weld. The edges of the parts are cut with the angle of cutting the edges in the range of 65°<α<75° degrees. Perform single-pass welding of the butt joint in an inert gas environment by automatic arc welding with the formation of the weld root on weight with a weld width B<L. After the root of the weld is cooled, the space between the bevels of the two edges is filled with beads by multi-pass arc welding in a mixture of shielding gases using a filler wire.

The combination of the listed essential features provides a technical result - a reduction in the heating zone, the elimination of welding defects, the temperature-time separation of the seams that fill the space between the bevels of the edges of the two parts, and the exclusion of the influence of filling beads on the formation of the root of the seam.

This makes it possible to solve the problem of ensuring equal strength of the weld and the base metal while eliminating stress concentrators in the root of the weld and reducing the shrinkage of the welded joint.

The achieved result is provided not only by the presence of distinctive features, but also depends on their interaction with other essential features of the proposed method. This allows you to expand the functionality of the method, provide a solution to the problem.

An extended function provided by known and distinctive features, and obtaining an unobvious result from the use of these features in the form of the formation of a weld root with a bulge on the reverse side and with a smooth transition to the base metal due to welding in helium indicates the compliance of the proposed technical solution with the criterion of "inventive step" .

Brief description of the drawings

In FIG. 1 shows the connection of parts before welding.

In FIG. 2 shows a schematic representation of the welded joint after the root weld has been made.

In FIG. 3 shows the successive filling of the grooves with multi-pass rollers.

In FIG. Figure 4 shows a snapshot of a section of a welded joint of a specimen made of AMg6 alloy 12 mm thick.

In FIG. Figure 5 shows a snapshot of a section of a welded joint of a sample made of AMg6 alloy 12 mm thick with a defect in the form of a sagging weld root.

Embodiments of the invention

The method described in the patent can weld both flat and cylindrical parts made of aluminum alloys with magnesium. Next, one of the embodiments of the invention will be described - automatic arc welding with a non-consumable electrode in an inert gas environment of model samples in the form of plates with a thickness of 8.0 mm or more from aluminum alloy AMg6, since the technical result for other aluminum-magnesium alloys is similar to that considered here.

The description uses the terms adopted in the national standard of the Russian Federation GOST Ρ 58904-2020/ISO/TR 25901-1:2016 and in GOST Ρ 50.05.08-2018.

Welding edge - part of the melted surface that supports the weld pool.

Cutting edges - giving the edges to be welded the required shape.

Edge preparation angle - angle α between the beveled edges of the parts to be welded.

Edge bevel - straight inclined cut of the edge to be welded.

Butt joint - a type of joint in which the parts lie approximately in the same plane opposite each other at an angle of 135 ° to 180 °.

Passage, roller - metal, remelted or deposited for a single movement of the electrode, welding torch or gas burner.

Single pass welding - welding in which the weld is made in one pass.

The boundary of the outer surface of the passage is the longitudinal boundary between the rollers, or between the roller and the base material.

Root (seam) - a zone on the side opposite to that on which welding was performed.

Weld root convexity - part of a one-sided weld from the side of its root, protruding above the level of the surfaces of the welded parts (estimated by the maximum height of the surface of the weld root above the specified level).

Lack of fusion - a defect in the form of non-fusion in a welded joint due to incomplete melting of the edges of the base metal or surfaces of previously made weld beads.

Weld root concavity - a defect in the form of a depression on the surface of the reverse side of a one-sided weld (estimated by the maximum depth of the weld root surface from the level of the surfaces of the welded parts).

As shown in FIG. 1, part 1 and part 2 are involved in welding. On parts 1 and 2, protrusions 3 of the edges of the parts are made. The protrusions 3 of the edges of parts 1 and 2 are made with a thickness d (mm) from 3.0 to 6.0 mm with a thickness t≥8.0 of the wall of parts 1 and 2 mm in accordance with the ratio d/t≤0.75. It has been experimentally established that:

1. - If 3.0<d<6.0 mm, then at t≥8.0 mm the ratio d/t≤0.75.

2. - If d> 6.0 mm, then high-quality formation of a seam with through penetration is not ensured.

This makes it possible to obtain a technical result in the form of a reduction in the heating zone due to single-pass welding of the butt joint in helium. Increasing the thickness of the protrusions 3 edges of parts 1 and 2, as a rule, leads to an increase in the heating zone. The use of an inert gas in the form of helium does not lead to a significant increase in the heating zone, which does not affect the convexity of the weld root on the reverse side.

The length of the protrusion 3 edges of parts 1 and 2 must satisfy the condition L<(3d+Δ), where Δ is the allowance for shrinkage of the butt weld.

If L>(3d+Δ), then this leads to an increase in the number of filling beads and, accordingly, the degree of heat input into the welded joint, which contributes to an increase in the shrinkage of the joint.

The fulfillment of the condition L<(3d+Δ) allows to obtain a technical result in the form of a reduction in the heating zone and the level of shrinkage of the welded joint.

Further, the edges of parts 1 and 2 are cut with giving them a bevel 4. The edges of parts 1 and 2 are cut with the angle α of cutting the edges in the range from 65 to 75 degrees.

As a result of the experiment, it was found that if you choose the angle of cutting edges α<65°, then when filling rollers 8, 9, 10, 11, 12, 13, 14, 15, defects accumulate on the border of these rollers and bevels 4 of the edges of the parts 1 and 2, which in the future can serve as weld stress concentrators and adversely affect the equal strength of the welded joint.

If you choose the angle α>75°, then this leads to an increase in the width of the space 5 between the bevels 4 of the edges of parts 1 and 2, which in turn leads to an increase in the volume of filler material to completely fill the space 5 between the bevels 4 of the edges of two parts 1 and 2 due to the increase in the number of filling rollers. This leads to a longer high-temperature thermal cycle of welding, which contributes to an increase in the heating zone and shrinkage of the welded joint.

The implementation of the angle of cutting edges 65°<α<75° allows you to get a technical result, which consists in the formation of a joint without non-fusion and without incomplete filling of the space 5 between the rollers and bevels 4 of the edges of parts 1 and 2. This eliminates welding defects.

Parts 1 and 2 are connected in such a way that the protrusions 3 of the edges of parts 1 and 2 are joined to each other and form a butt joint, as shown in Fig. 1 and 2.

As shown in FIG. 1, one-pass welding of the joint 6 of parts 1 and 2 is performed in an inert gas environment by automatic arc welding with the formation of the weld root 7 (Fig. 2) on weight. In this case, the seam of the joint 6 is made with a width B that satisfies the condition B<L, where L is the length of the protrusion 3 of the edges of parts 1 and 2.

If B>L, then there is an increase in the heating zone with possible melting of the bevels 4 of the edges of parts 1 and 2. This can lead to a decrease in the efficiency of penetration and the appearance of a welding defect in the form of lack of penetration. In this case, to form the weld root 7 with a bulge on the reverse side, it is necessary to increase the heat input into the welded joint. This, in turn, can lead to increased shrinkage of the joint.

The fulfillment of the condition B<L provides the technical result in the form of a reduction in the heating zone and the elimination of a welding defect in the form of a lack of fusion of the joint 6 of the welded parts 1 and 2.

In single-pass butt welding of 6 parts 1 and 2, helium is used as an inert gas.

According to the results of the experiments, it was found that when welding without helium (in argon), the root of the weld 7 when connecting the joint 6 is formed with a defect in the form of a concavity on the reverse side of the welded parts 1 and 2.

Due to the higher helium ionization potential, the formation of a highly concentrated arc with increased penetration ability and a relatively narrow weld in single-pass welding with through penetration and the formation of the weld root 7 with a convexity on the reverse side and with a smooth transition to the base metal of parts 1 and 2 is ensured.

This allows to obtain a technical result in the form of a reduction in the heating zone due to single-pass welding of the joint 6 of the joint and in the exclusion of welding defects in the form of a concavity of the root of the weld 7 on the reverse side.

As shown in FIG. 2 and in FIG. 3 after cooling the weld root 7 fill the space 5 between the bevels 4 of the edges of parts 1 and 2 with beads 8, 9, 10, 11, 12, 13, 14, 15 by multi-pass arc welding in a mixture of protective gases (argon + helium in a ratio of 30% Ar and 70% He) using filler wire. For aluminum alloys, the use of a mixture consisting of 70% He and 30% Ar is very effective in terms of productivity. In this case, the thickness of the metal welded in one pass increases significantly, and the formation of the seam improves [Akulov A.I. Technology and equipment for fusion welding / A.I. Akulov, G.A. Belchuk, V.P. Demyantsevich. - M.: Mashinostroenie, 1977].

This makes it possible to obtain a technical result in the form of excluding the influence of filling rollers 8, 9, 10, 11, 12, 13, 14, 15 on the formation of the weld root 7 when the space 5 between the bevels 4 of the edges of parts 1 and 2 is completely filled.

When filling the space 5 between the bevels 4 of the edges of parts 1 and 2, the first roller 8 is performed without displacement relative to the joint 6.

As shown in FIG. 3, after roller 8 has been completed, the next rollers are applied offset. The roller 9 is displaced relative to the roller 8 by 40-60% of its width. In the same way, roller 10 is displaced relative to roller 8, roller 11 is displaced relative to roller 10, roller 12 is displaced relative to roller 11, roller 13 is displaced relative to roller 12, roller 14 is displaced relative to roller 13, roller 15 is displaced relative to roller 14.

The following was established experimentally. If the displacement of rollers 9, 10, 11, 12, 13, 14, 15 relative to the previous ones was less than 40% or more than 60%, then the sequence of filling space 5 with rollers 9, 10, 11, 12, 13, 14, 15 was violated, which required formation of additional rollers. This led to an increase in heat input into the welded joint and, accordingly, to shrinkage of the joint as a whole.

When filling space 5 with rollers 9, 10, 11, 12, 13, 14, 15 with an offset in the range of 40-60% relative to the previous ones, a seam is formed without additional heat input. This makes it possible to obtain a technical result in the form of eliminating welding defects and reducing joint shrinkage.

In addition, in order to reduce the sagging of the root of the seam 7 in the proposed method, the technology of intermittent formation of the seam of the filling rollers 8, 9, 10, 11, 12 and 13 is used. The technology consists in cooling each of the rollers 8, 9, 10, 11, 12 and 13 to room temperature after the initial six passes. In this case, the boundaries between the filling rollers 13, 14 and 15 of the upper layer and the boundaries between the rollers 14 and 15 and bevels 4 are performed above the outer surface of the parts 1 and 2 to be welded.

This makes it possible to obtain a welded joint with reinforcement of the seam from the outside and to ensure equal strength of the seam and the base metal.

This allows to obtain a technical result in the form of a temperature-time separation of the seams filling the space 5 between the bevels 4 of the edges of parts 1 and 2, and eliminating the influence of the filling rollers 8, 9, 10, 11, 12, 13, 14, 15 on the formation of the weld root 7 .

As shown in FIG. 4, welding with the implementation of these solutions made it possible to ensure the high-quality formation of the root 7 of the weld between parts 1 and 2 with a smooth transition to the base metal of parts 1 and 2 without external and internal defects.

As the results of the experiments showed, when filling rollers 8, 9, 10, 11, 12 and 13 are made without cooling the joints to room temperature, a significant sagging of the root of the weld 7 (Fig. 5) is observed due to shrinkage phenomena and its extrusion. With excessive sagging of the root of the weld 7 with an undesirable configuration in the form of sharp transitions (stress concentrators) from the back bead to the base metal, the equal strength of the welded joint decreases. This leads to the fact that the performance of the welded joint deteriorates.

In the proposed technical solution, the welding process of the AMg6 alloy in a helium environment ensures the high-quality formation of the weld root 7 with a bulge on the reverse side and with a smooth transition to the base metal of parts 1 and 2, and filling the space 5 between the bevels 4 of the edges of parts 1 and 2 initially with six temperature and time with rollers 8, 9, 10, 11, 12 and 13 allows, due to their cooling to room temperature, to maintain a smooth transition from the root of the weld 7 to the base metal and, thereby, ensure the absence of undesirable configuration in the form of sharp transitions (stress concentrators) and defects in the form of sagging of the weld root 7. At the same time, due to the equal strength of the welded joint, its performance is ensured. This is an extended function provided by the well-known and distinctive features of non-obviousness of the technical solution.

Industrial Applicability

The most effective way is to use the method of welding parts made of aluminum alloy in extended structures of variable cross section in the form of containers and housings for various industrial purposes, operating under conditions of cyclic loading and pressure of an aggressive environment. Where there are stiffening elements in the structures, for example, frames, and there are increased requirements for the geometry of the product in general and for the quality of welds, in particular.

Implemented in practice, the proposed method of welding aluminum alloy parts, confirmed the technical result, which consists in reducing the heating zone due to single-pass welding of the butt joint; in the exclusion of welding defects; in the temperature-time separation of the seams that fill the space between the bevels of the edges of the parts and in the exclusion of the influence of the filling beads on the formation of the weld root.

In general, the considered embodiment of the invention was implemented on currently existing equipment using available materials. This confirms its performance and industrial applicability.

Claims (8)

1. A method for welding parts made of aluminum alloy, including making the protrusion of the edges of the parts, cutting the edges of the parts with giving them a bevel, assembling the joint of the protrusions of the edges and welding the joint with filling the space between the bevels of the edges of the two parts, characterized in that the protrusions of the edges of the parts are made with a thickness d from 3.0 to 6.0 mm with a wall thickness of parts t≥8.0 mm in accordance with the ratio d/t≤0.75, with the length of the ledge of the edges L<(3d+Δ), where Δ is the allowance for shrinkage of the butt weld , cut the edges of parts with a bevel angle in the range of 65°<α<75°, perform single-pass welding of the butt joint in an inert gas environment by automatic arc welding with the formation of a weld root on weight with a weld width B<L, cool the weld root and fill the space between the bevels of two edges with rollers by multi-pass arc welding in a mixture of shielding gases using a filler wire. 2. Welding method according to claim 1, characterized in that the parts are welded from aluminum alloy AMg6. 3. Welding method according to claim 2, characterized in that single-pass welding of the butt joint is performed in a helium environment. 4. The welding method according to claim 1, characterized in that when filling the space between the bevels of the two edges, the first bead is made in the center relative to the joint. 5. The welding method according to claim 1, characterized in that each subsequent roller after the first one is shifted relative to the previous one by 40-60% of its width. 6. The welding method according to claim 1, characterized in that the first six rollers filling the space between the bevels of the two edges are performed after each previous one has cooled to room temperature, and starting from the seventh, the rollers are performed without intermediate cooling. 7. The welding method according to claim 1, characterized in that the space between the bevels of the two edges is filled in a mixture of protective gases argon + helium in a ratio of 30% Ar and 70% He. 8. The welding method according to claim 1, characterized in that the filling of the space between the bevels of the two edges is completed at the position of the boundaries between the rollers and the position of the boundaries between the rollers and bevels above the outer surface of the parts to be welded.

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