RU2699493C1 - Method of aluminum alloy nonconsumable electrode welding - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to a method of nonconsumable electrode welding of parts from aluminum alloys and can be used in machine building, aircraft building, nuclear power engineering, petrochemical, gas and other industries. Parts 1 and 2 are machined with bevelled edges 3 and 4 in interval α=68…72°. On part 1 there performed is technological ledge 5 and groove 6, at which height of one wall 8 is higher than height of other wall 9. Shank 4 is blunted 7 on part 2. Height of blunting 7 shall not exceed difference of height of walls 8 and 9 of groove 6 of part 1. Welded surfaces of parts 1 and 2 are cleaned of contaminants. After finishing of welded surfaces of parts 1 and 2 before welding, time is not more than 8 hours. Part 2 is installed on part 1 until it stops blunting 7 into higher wall 8 of groove 6. Automatic welding by nonconsumable electrode is performed at joint of parts 1 and 2 at alternating current in two passes.EFFECT: higher quality and stability of formation of welded seam with shifted geometry towards groove and with uniform external configuration throughout joint.8 cl, 5 dwg, 1 tbl

Description

Technical field

The invention relates to the field of welding production, in particular, to a method for automatic argon arc welding of non-consumable electrode of longitudinal and circumferential seams of extended structures of variable cross section in the form of bodies and pressure vessels, which require high-quality welded joints without defects. The invention can be used in mechanical engineering, aircraft manufacturing, in nuclear energy, in the petrochemical, gas and other industries.

State of the art

The known method for which the patent of the Russian Federation No. 2561617 "Method for the arc welding of aluminum alloys", IPC: V23K 9/16, V23K 103/10; priority of 11/13/2013, published on 08/27/2015; author Brovko A.V. The method consists in the fact that the welded product is placed in a climatic chamber, in which, before and during the entire welding process, the surface of the product is blown with a stream of heated air at a speed of 0.02 to 0.5 meters per second, regardless of the rate of flow of the protective gas in the process welding. In this case, the supplied air is heated to a temperature exceeding the surface temperature of the welded product by at least 2 ° C.

The disadvantage of this method is the complexity of the process associated with blowing the surfaces of the welded parts with a stream of heated air. The application of such an operation requires the use of additional equipment in the form of a climate chamber, which is caused by additional costs in the manufacture of parts. In addition, the welding of overall parts directly depends on the dimensions of the climate chamber, which in turn limits the application of this welding method. At the same time, in order to obtain a high-quality welded joint (without defects), it is necessary to control the humidity and temperature of the surrounding air, as well as the speed of the air flow, the product temperature and the temperature difference of the air on the film surface and the incoming heated air, which in turn also complicates the welding technology and the presence of additional control operations. In addition, the main condition for the maximum decomposition of hydrides and evaporation of moisture from the surface of the product is the intake of ambient air with a higher temperature than the temperature of the surface of the product itself, otherwise the decomposition of hydrides and evaporation of moisture from the surface are impaired.

From analogues, as a prototype, the patent of the Russian Federation No. 2505385 was selected “Method of argon-arc welding with non-consumable electrode”; IPC: V23K 9/18, V23K 9/167, priority July 11, 2012, published January 27, 2014, authors: M.S. Pisarev, B.S. Belousov, I.S. Gareev. The method is intended for argon-arc welding of non-consumable electrode parts made of aluminum and magnesium alloys, one of which is thin-walled, the other thick-walled. A groove is made on the thick-walled part, one side of which is higher than the other. The width of the groove is from 2.5 to 3, and the depth from 0.25 to 0.45 of the thickness of the thin-walled part. A layer of cleaning flux is applied to the mating surfaces of the parts, which is located on the surfaces of the parts for 1 to 10 minutes. Then the flux is removed from the parts 2/3 of the thickness of the thin-walled part and the thin-walled part is installed all the way to the higher wall of the groove on the thick-walled part. Parts are melted in the area of their junction, freed from flux. When changing the thickness of the cross section of a thick-walled part in the welding process, the welding current is stepwise changed without interrupting the welding process. Details are welded no more than 8 hours after the flux removal.

The disadvantage of this method is the low productivity of welding, which is associated with the use of manual argon arc welding when connecting parts. Also, obtaining a high-quality welded joint (without defects) with uniform penetration in thickness (penetration depth), using manual argon-arc welding, very much depends on the qualifications of the welder. Due to electrode oscillations, changes in the length of the arc gap and values of the welding speed parameter during manual argon-arc welding, uneven heating of the welded edges occurs with a different heat distribution over the weld section, which can lead to an increase in welding stresses and deformations. In addition, when performing welding in one pass, it is possible to form a seam with a variable cross section and the formation of undercuts along the edges of the seam, which are stress concentrators in the seam. This can lead to structural failure due to accumulation of internal welding stresses.

In the prototype, the weld has a symmetrical shape relative to the joint zone of the parts, in which the formation of defects in the form of pores and oxide inclusions in the root of the weld from the side of a thick-walled part is possible.

Disclosure of invention

The task to which the invention is directed is to improve the quality and stability of the formation of a weld with a displaced geometry in the direction of the groove and with a uniform external configuration throughout the joint.

The technical result achieved by solving this problem is to reduce welding stresses and strains while increasing the assembly accuracy, guaranteed exclusion of pores in the root of the seam and the displacement of oxide inclusions in the volume of the groove.

The technical result is achieved in that in a method for automatic argon-arc welding of non-consumable electrode parts made of aluminum alloys, comprising making a second part of a groove whose height of one wall is greater than the height of another wall, installing the first part on the second until it stops in a higher wall of the groove on the second part , melting parts, according to the invention, cut the ends of the parts with a bevel of edges in the range from 68 to 72 degrees and blunt the edge on the second part with a height not exceeding the difference and the heights of the groove walls of the first part. Before installing the first part on the second, the welded edges are chemically etched, mechanically cleaned, degreased, and dehydrated. Set the second part to the first. Ensure tight assembly of welded edges. Protective gas is supplied to the joint zone of the parts, which is heated with the melting and spreading of the metal of the first part in the central part of the joint zone. A weld is formed with an offset towards the grooves of the first part. Perform welding in automatic mode in two passes. After welding, the parts are annealed.

The combination of the essential features listed provides a technical result - a reduction in welding stresses and strains, an increase in assembly accuracy, guaranteed exclusion of pores in the root of the seam and the displacement of oxide inclusions in the groove volume. This entails an increase in the stability of formation and quality of the weld with a displaced geometry towards the groove and with a uniform external configuration along the entire joint.

Performing cutting with bevelled edges in the range from 68 to 72 degrees ensures access of the electrode and the arc to the lower zone of the welded joint for high-quality execution of the root weld with a displaced geometry towards the groove. The execution of the groove, in which the height of one wall is greater than the height of the other wall, the blunting of the edge on the second part, the installation of the first part on the second all the way to the higher wall of the groove eliminates the displacement of the parts relative to each other in height during assembly and ensures the formation of a weld with offset geometry in side of the groove to displace oxide inclusions in the groove volume.

The use of automatic welding ensures stability and reproducibility of technological modes of welding throughout the joint, which contributes to the formation of a high-quality weld without distortion of shape.

Performing heat treatment in the form of annealing helps to reduce the level of internal welding stresses that cause deformation of the structure. This improves manufacturing accuracy and weldment quality.

After mechanical cleaning of the edges, it is allowed to weld the parts no later than 8 hours. This allows you to exclude pores in the root of the seam and reduce the number of oxide inclusions, which increases the quality of the seam and the stability of its formation.

It is possible to perform the first pass without the use of a welding wire to form the root of the seam with an offset geometry in the direction of the groove. This allows maximum displacement of oxide inclusions in the volume of the groove, which increases the quality and stability of the formation of the weld.

It is possible in the process of the second pass to use a welding wire to fill the groove. This solves the problem of improving the quality and stability of the formation of the weld with a uniform external configuration.

Ensuring a tight assembly of the welded edges can be carried out with a gap of the edges in the joint of not more than 0.3 mm This allows you to increase the accuracy of the assembly, reduce welding stress and strain, which increases the quality and stability of the formation of the weld.

Argon shielding gas can be supplied to the burner. This improves the quality of the weld formation.

During the welding process in automatic mode, using the video surveillance system, it is possible to control the movement of the welding torch along the entire length of the seam without offset relative to the joint, to maintain the value of the welding current, arc voltage, welding speed and filler wire feed speed. This increases the stability of the welding process with uniform heat input and the distribution of temperature fields along the entire length of the weld and reduces the level of welding stress and deformation.

Prevention of displacement of the non-consumable electrode relative to the joint towards the welded parts allows the formation of a high-quality welded joint with guaranteed displacement of the seam towards the groove and with no distortion of the shape of the seam.

Brief Description of the Drawings

In FIG. 1 shows the design of the parts to be welded.

In FIG. 2 shows a cross section of a welded joint with defects.

In FIG. 3 shows the connection of parts before welding.

In FIG. 4 shows the connection of parts before welding with a possible gap in the joint. In FIG. 5 shows a cross section of a welded joint without defects.

Embodiments of the invention

In the manner described in the patent, both flat and cylindrical parts can be welded. Next, one embodiment of the invention will be described - automatic argon arc welding of non-consumable electrode of model samples in the form of aluminum alloy plates.

As shown in FIG. 1, part 1 and part 2 participate in welding. On parts 1, 2, they are cut with bevel edges 3 and 4 in the interval α = 68 ... 72 °.

If you select an angle a of the bevel of edges 3 and 4 less than 68 °, then this can lead to lack of penetration along the cross-section of the seam. To eliminate this, it is necessary to increase the effective power of the welding arc, which can lead to overheating of the welded parts and an increase in the level of welding stresses in the weld and deformations in the structure.

If you choose an angle a greater than 72 °, you will need to increase the amount of filler material to completely fill the groove, usually with a longer high-temperature thermal welding cycle (heating), or it will be necessary to perform an additional pass, which also contributes to an increase in the level of welding stresses in the weld and deformations in the structure.

On the part 1, a technological protrusion 5 and a groove 6 are made, in which the height of one wall 8 is greater than the height of the other wall 9. On the part 2, the blunting 7 of the edge 4 is performed. The height of the blunting 7 should not exceed the difference in the heights of the walls 8 and 9 of the groove 6 of the part 1.

For stable formation of the weld, the surfaces of parts 1 and 2, namely edges 3 and 4, blunting 7, wall 8 are cleaned of contaminants. To do this, before welding, parts 1 and 2 are subjected to chemical etching. After that, the surfaces of parts 1 and 2 to be welded are subjected to mechanical cleaning with a scraper, followed by rubbing with a coarse calico cloth moistened with alcohol.

Moreover, the time interval between the end of the machining of the surfaces of parts 1 and 2 to be welded before the start of welding is no more than 8 hours. This preparation cycle is performed to ensure the required cleanliness of the welded surfaces of parts 1 and 2 and to eliminate the effect of contaminants on the quality of the weld.

With an increase in the time interval of more than 8 hours, an increase in the thickness of the oxide film occurs, which requires excessive heat input from the welding source to melt. This can lead to increased stress and strain in the weld. The table below shows the effect of the time interval between the end of mechanical stripping and the start of welding on the quality characteristics of the weld. The results were obtained as a result of experiments. A defective weld joint obtained during a time interval between mechanical stripping and welding of 10 hours is shown in FIG. 2.

From table 1 it can be seen that the absence of defects is observed when the time between the end of the mechanical stripping process and the start of welding is 8 hours. The pores 10 and oxide inclusions 11 (in Fig. 2), which are formed with increasing time between the end of the mechanical stripping process and the start of welding, are stress concentrators in a weld. They can lead to destruction during the accumulation of internal welding stresses and deformation of the welded joint.

After cleaning, install part 2 on part 1 until the blunting 7 stops in the higher wall 8 of groove 6. This eliminates the displacement of parts 1 and 2 relative to each other in height during assembly and ensures the formation of a weld with a displaced geometry in the direction of the groove 6 to displace oxide inclusions into the volume of the groove 6.

Making the design of the welded joint of the castle type simplifies the assembly process, ensures the exact location of the parts relative to each other and ensures uniform formation of the weld.

In FIG. 3 shows the connection of part 2 with part 1 before welding. The gap in the joint between blunting 7 and wall 8 should not exceed 0.3 mm. If you increase the gap of more than 0.3 mm, the accuracy of positioning of parts 1 and 2 relative to each other worsens and the formation of a seam with its introduction into the technological protrusion 5 is possible.

The clearance is reduced to less than 0.3 mm, thereby improving the positioning accuracy of part 1 relative to part 2 and provides a weld with a penetration not exceeding the depth of the groove 6 and the width d of the zone of penetration 14 not exceeding the width D of the groove 6 (in Fig. 4).

This leads to the elimination of defects in the form of pores 10 (Fig. 2), oxide inclusions 11 at the root of the seam 15, burn through and non-fusion of the edges 3 and 4. As a result, the internal welding stresses are reduced, and the level of deformation of parts 1 and 2 is reduced.

The presence of the technological protrusion 5 and the wall 9 simplifies the assembly process, ensures the exact location of parts 1 and 2 relative to each other and eliminates the likelihood of displacement of parts 1 and 2 in height.

Automatic welding non-consumable electrode 12 (Fig. 3) is performed at the junction of parts 1 and 2 on alternating current in two passes. The values of the main welding parameters are supported in automatic mode. An inert argon gas is used as a shielding gas, which is supplied through a torch 13 to the joint zone of parts 1 and 2 to protect the molten metal of the weld pool. The first pass is performed without a welding wire with penetration and formation of the root of the seam with a displaced geometry towards the groove 6. This allows the oxide inclusions 11 to be displaced into the volume of the groove 6, which improves the quality and stability of the formation of the weld 15 with a uniform external configuration.

Structurally, the bevel surface of the edge 3 of the part 1 is located closer to the electrode 12. Therefore, the heating from the burner 13 of this surface is more intense. That is, during the heat exposure of the welding arc, the bevel surface of the edge 3 of part 1 is first heated. The metal of part 1 melts, spreads to the joint zone of parts 1 and 2, and a weld 15 is formed with an offset towards the groove 6 of part 1 relative to the joint.

The wall 8 of the groove 6 on the part 1 provides the formation of a weld seam 15 with a displaced geometry (in Fig. 4) towards the groove 6 to displace the oxide inclusions 11 (Fig. 2) into the cavity of the groove 6.

A second pass is performed to fill the groove using a welding wire. This ensures uniform formation of the seam 15 from the outside.

The presence of a groove 6 on the part 1 ensures the formation of a weld seam 15 (in Fig. 4) without defects in the form of oxide inclusions and pores, in addition, impurities and oxide inclusions are collected in the groove 6 as a result of welding.

The manufacture of parts 1 and 2 with a bevel of the edges 3, 4, blunting 7 and the wall 9 of the groove 6 provides the possibility of welding thick-walled structures.

After welding, annealing of parts 1 and 2 is performed to reduce the level of residual stresses and thereby prevent the formation of post-weld cracks.

Industrial applicability

The most effective way is to use the proposed method in extended structures of variable cross section in the form of bodies, containers and pressure vessels operating under conditions of a pulsed increase in temperature and pressure of an internal aggressive environment, dynamic loads, etc. Where stiffeners are present in the structures, for example, frames and higher demands are placed on the geometry of the product as a whole and on the quality of the welds, in particular.

The proposed method provides a technical effect, which consists in reducing welding stresses and strains while increasing the accuracy of the assembly and in the guaranteed exclusion of pores in the root of the seam and the displacement of oxide inclusions in the volume of the groove.

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

Claims (8)

1. A method of welding a non-consumable electrode of parts made of aluminum alloys, comprising making a groove on the first part whose height of one wall is greater than the height of the other wall, installing the second part on the first until it stops in a higher wall, melting the parts, characterized in that they cut the ends of the parts with a bevel of the edges with an angle between the edges of 68 to 72 degrees, dull the edge on the second part with a height not exceeding the magnitude of the height difference of the groove walls of the first part, before installing the second part on the first the welded edges are chemically etched, mechanically cleaned, degreased, dehydrated, the second part is installed on the first, assembly of the welded edges is ensured, protective gas is supplied to the joint zone of the parts, which is heated with melting and spreading of the metal of the first part in the joint zone, the weld is formed with an offset of side of the groove of the first part, welding is performed automatically in two passes. 2. The welding method according to p. 1, characterized in that after mechanical cleaning of the edges, the parts are welded no later than 8 hours. 3. The welding method according to claim 1, characterized in that during the first pass the welding wire is not used and the penetration and formation of the root of the seam with the necessary zone of penetration are controlled. 4. The welding method according to claim 1, characterized in that during the second pass, a welding wire is used to fill the groove. 5. The welding method according to claim 1, characterized in that the assembly of the edges to be welded is carried out with a gap of edges in the joint of not more than 0.3 mm. 6. The welding method according to claim 1, characterized in that the argon gas is supplied to the burner. 7. The welding method according to p. 1, characterized in that during the welding process, the movement of the welding torch along the entire length of the seam without offset relative to the joint is automatically controlled, the welding current, arc voltage, welding speed and filler wire feed speed are maintained. 8. The welding method according to claim 1, characterized in that after welding the parts are annealed.

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