RU2789951C1 - Method for pulsed arc welding of an aluminium-magnesium alloy with a melting electrode - Google Patents

Abstract

FIELD: welding.

SUBSTANCE: invention can be used for mechanised arc welding of parts made of an aluminium-magnesium alloy with a thickness of more than 100 mm with a melting electrode in an inert gas. The welded edges are formed with an X-shaped profile. Each edge comprises a central linear section connected by arcuate sections with inclined linear sections. Each of the inclined linear sections of the edge profile is made with an additional bevel with an angle of inclination less than the angle of inclination of said linear section, and the central linear section is made with a chamfer. Prior to welding the root run, removable lining is installed on the side of the chamfers of the central linear sections. Multi-pass welding is performed on each side of the groove. The parts being welded are assembled on a positioner providing consecutive reorientation of the parts in the process of welding when performing welding passes. Welding is performed with preheating and simultaneous heating of the welding zone.

EFFECT: creation of a vacuum-tight welded joint of the parts with minimal deformation thereof and maintaining of the exact geometric parameters of the parts after welding.

4 cl, 3 dwg, 2 tbl, 1 ex

Description

This welding technology belongs to the fields of mechanical engineering and electrical engineering, is intended for mechanized arc welding with a consumable electrode (MAMA/GMAW) in an inert gas and can be used for vacuum-tight welding of parts.

A known method of gas-shielded consumable electrode arc welding of butt joints of aluminum alloys of large thickness, in which an X-shaped groove of the edges to be welded with a bilateral symmetrical curvilinear bevel is performed - type C26 (Arc welding of aluminum and aluminum alloys in inert gases. Welded joints. - Main types , Structural Elements and Dimensions, GOST 14806-80, Moscow: Publishing House of Standards, 1980, p. 18). Cutting edges for welding provides for a blunting of at least 8 mm in size and a rounding radius of 10 mm at an edge opening angle of 15 °.

The disadvantage of this method is that when welding large thicknesses, there is no free access of the welding torch to the welded edges, as a result of which the welder cannot fully control the welding process: the electrode wire stickout increases, which leads to the arc wandering along the edges and their incomplete penetration. The subsequent removal of the weld root and filling the groove formed with filler metal does not guarantee the elimination of lack of penetration in the central part of the welded joint, which is unacceptable, as it leads to a decrease in the quality characteristics of the welded joints.

Closest to the claimed solution is a method of pulsed arc welding with a consumable electrode of aluminum alloys (RF patent No. 2553769. IPC B23K 9/09, B23K 33/00. B23K 103/10, published 06/26/2015 Bull. No. 17). An X-shaped profile of the edges to be welded is formed and multi-pass welding with a thickening of the seam is performed. Each of the edges contains a central linear section connected by arcuate sections with inclined linear outer sections. The arcuate section is made with a radius R=(0.30÷0.50)β, the thickness of the central linear section is performed within c=(0.05÷0.10)β, where β is the thickness of the welded edges.

The disadvantage of this solution is that when welding parts of large thickness from an aluminum-magnesium alloy, taking into account the specified parameters for cutting edges, the cross-sectional area of the weld reaches such values at which there is an increase in the consumption of filler metal, an increase in heat input, an increase in the number of weld passes, which contribute to the appearance of residual deformations, non-fusion, lack of penetration, cracks and pores.

The objective of the claimed method is to optimize the geometric parameters of cutting edges when welding large-sized aluminum-magnesium alloy parts in order to obtain a high-quality vacuum-tight welded joint.

When using the invention, the following technical result is achieved:

- obtaining a vacuum-tight welded joint;

- minimization of deformations of welded parts during welding;

- ensuring the exact geometric parameters of the parts to be welded after welding;

- Welding of large parts.

To solve this problem and achieve a technical result, a method is claimed for pulsed arc welding with a consumable electrode of an aluminum-magnesium alloy, including the formation of an X-shaped profile of the welded edges. Each of the edges contains a central linear section connected by arcuate sections with inclined linear sections. The method includes performing multi-pass welding with thickening of the seam. Each of the inclined linear sections is made with additional bevels, while the angles of inclination of these bevels are chosen depending on the thickness of the parts to be welded. A chamfer is performed on the central linear section. The parts to be welded are installed on the positioner, and before welding the root pass, a removable lining is installed from the side of the chamfers of the central linear sections. Welded passes are performed according to a given algorithm with sequential reorientation of the parts to be welded. The removable lining is made of a material with a melting point higher than that of the parts to be welded. Welding is carried out with preliminary and concomitant heating of the welding zone. When welding large parts, the process is carried out at t _air. =20…30°C and relative air humidity 50-65%.

The execution of each of the inclined linear sections with additional bevels and the choice of the angle of inclination of these bevels, depending on the thickness of the parts to be welded, makes it possible to weld large parts made of aluminum-magnesium alloy, while obtaining a vacuum-tight welded joint and ensuring accurate geometric parameters of the parts to be welded after welding. By achieving the optimal cross-sectional area of the weld, a relatively small number of weld passes, the possibility of residual deformations, non-fusion, lack of penetration, cracks and pores is reduced.

The execution of the chamfer in the central linear section allows you to achieve the best formation of the root pass, respectively, and the entire weld. which contributes to obtaining a vacuum-tight welded joint.

Installing the parts to be welded on the positioner makes it possible to achieve (required) accurate geometric parameters after welding, due to the rigid fixation of the parts to be welded and their positioning among themselves with high accuracy under geodetic control, and this positioner also allows welding large-sized parts.

Installing a removable lining on the side of the chamfers of the central linear sections before welding the root pass prevents the molten material from flowing out during the root pass, thereby ensuring its best formation, respectively, of the entire weld, which contributes to obtaining a vacuum-tight welded joint.

The execution of welded passes according to a given algorithm with sequential reorientation of the parts to be welded ensures the achievement of accurate geometric parameters of the parts to be welded after welding due to the smoothest possible penetration of the parts to be welded from both sides, respectively, the deformations in this case are minimal.

The use of a removable lining made of a material with a melting temperature higher than that of the welded parts contributes to its unhindered removal after the root pass is made, as well as ensuring non-fusion with the material of the welded parts, thereby ensuring the best formation of the root pass.

respectively, and the entire weld, which contributes to obtaining a vacuum-tight welded joint.

The implementation of welding with preliminary and concomitant heating of the welding zone makes it possible to thermally treat the edges of welded large-sized parts made of aluminum-magnesium alloy and achieve the required characteristics necessary to ensure optimal welding conditions, due to this, it is possible to exclude the appearance of non-fusion, lack of penetration, cracks and since.

Due to the constancy of the values of t _air. =20…30°C and relative air humidity of 50-65% in the process of welding large-sized parts, it is ensured that a high-quality vacuum-tight weld is obtained, the exact geometric parameters of the welded parts are preserved after welding.

The essence of the invention is illustrated by drawings.

In FIG. 1 shows the geometry of cutting edges, where:

1 - welded part;

2 - edge cutting;

3 - central linear section;

4 - chamfer;

5 - arcuate section;

6 - inclined linear section;

7 - additional bevel.

In FIG. 2 shows the equipment used in welding parts and the equipment placed on them, where:

1 - welded part;

10 - flexible guide;

11 - vacuum suction cup;

12 - self-propelled welding tractor;

13 - welding torch;

14 - four-way holder;

15 heating mat;

16 - thermocouple;

17 - removable lining.

In FIG. 3 shows a positioner with welded parts installed on it, where:

1 - welded part;

8 - positioner;

9 - special jack;

10 - flexible guide;

11 - vacuum suction cup.

The method of pulsed arc welding with a consumable electrode is implemented as follows.

On the parts to be welded 1 made of aluminum-magnesium alloy along the side edges, edge preparation 2 is performed, and each of the edge preparation 2 contains a central linear section 3, with a chamfer 4 made on it, and the central linear section 3 itself is connected by arcuate sections 5, the radius of which is equal to g, with inclined linear sections 6, made at an angle α. which in turn contain additional bevels 7. made at an angle β. After cutting the edges 2 and before installing the parts to be welded 1 on the positioner 8, they are subjected to visual-measuring control.

Next, the welded joint is assembled on the positioner 8 so that when the two parts to be welded 1 are joined, an X-shaped profile is formed and there are no gaps between the ends of the two parts to be welded 1, the differences in the planes of the two parts to be welded 1 comply with the requirements of the working design documentation. The gap between the two parts to be welded 1 is selected by the stroke of special jacks 9 of the positioner 8.

Welding of parts is carried out using a mechanized welding unit, a system of preliminary and concomitant heating, placed on the surfaces of the parts to be welded 1 from sides (A) and (B). In this case, the mechanized welding installation is installed on the parts to be welded 1 from sides (A) and (B) using flexible guides 10 complete with vacuum suction cups 11. Flexible guides 10 are precisely positioned (parallel) with respect to the cutting of edges 2. On flexible guides 10 from the side of the first weld pass, a self-propelled welding tractor 12 and a trolley for the feeder are attached. For reliable and accurate fixation of the welding torch 13 at a given angle, as well as a point in relation to the surface to be welded, a four-way holder 14 of the welding torch 13 is used on the self-propelled welding tractor 12 with the obligatory fixation of all its stoppers. Before the start of welding, fine adjustments during the welding process are adjusted by linear sliders for transverse and vertical movement. The placement of the system of preliminary and concurrent heating on the parts to be welded 1 from sides (A) and (B) is carried out by laying out the heating mats 15 along the groove 2 at a given distance from the end of the parts to be welded 1. The heating mats 15 are fastened with three L-shaped aluminum brackets , the brackets are welded in the immediate vicinity of the heating mat 15, abutting against its insulating plate, the thermocouples 16 are set along the fixed heating mats 15. The fastener-thermocouple 16 is made by an aluminum L-shaped bracket, into the threaded hole of which the fixing bolt is screwed. After that, the process of welding parts is carried out directly, and welding is carried out in constant climatic conditions. Welding of parts, depending on the thickness of the parts to be welded 1, is performed with a certain number of passes, while the passes are performed according to a given algorithm with sequential reorientation of the parts to be welded 1 using positioner 8 from side (A) to side (B). All welded passes are made according to the technological map (TK). in which for each pass its technological parameters of welding are prescribed.

To form the root pass on the side (A), on the side (B), from the side of the chamfer 4, a removable lining 17 is installed. Next, the parts to be welded are preheated 1. which turns into an accompanying one, after which the welding itself is performed according to the algorithm.

Tests of the above method were carried out on parts with a spherical profile with a radius of 5000 mm. 7000 mm long. 2000 mm wide and 100 mm thick made of aluminum-magnesium alloy AMg5.

Edge preparations 2 for a given thickness of welded parts 1 were performed with the following geometric parameters:

- central linear section 3.4 mm;

- chamfer 4.2 mm × 1.82 mm;

- radius of arcuate sections 5, r=6 mm;

- angle of execution of inclined linear sections 6, α=30°;

- angle of execution of additional bevels 7, β=10°.

To confirm compliance with the established design requirements, the geometry of cutting edges 2 was checked using devices and tools:

- measuring magnifier;

- calipers;

- measuring metal rulers;

- goniometers;

- squares;

- probes.

Installation of parts to be welded 1 on positioner 8 was carried out with the provision of:

- no gap between the ends of the two parts;

- the absence of differences in the planes of the two parts;

- sphere radius tolerance ±10 mm.

Further, the installation of the system of preliminary and concomitant heating and installation of mechanized welding was carried out on the parts to be welded. Moreover, the heating mats 15 were laid out along the cutting edges 2 at a distance of 80 mm from the end of the welded parts 1, and the thermocouples 16 were set along the fixed heating mats 15 at a distance of 250 mm.

Welding was carried out under constant climatic conditions at t=23±l°C and relative air humidity of 60%. in 68 passes, with 33 passes on side (A) and 35 passes on side (B). All welded passes were made according to the technological chart (TC), in which for each pass its own technological parameters of welding were prescribed. The diameter and angle of the burner nozzle 13. Welding wire feed speed were selected individually for each pass.

In tables 1 and 2, the technological parameters of welding on pass No. 1 (root pass) and on pass No. 68 (last pass).

To form root pass No. 1 on side (A), on side (B), from the side of chamfer 4, a removable lining 17 ∅22 mm was installed from a material with a melting point higher than that of AMg5. Next, preheating of the parts to be welded 1 to 75°C was carried out, which turned into a concomitant one with a temperature of 50-55°C, after which the root pass was welded according to the TC with the welding torch 13 vertically relative to the transverse plane of the parts 1 to be welded and at an angle of 70° in relation to the weld (angle forward), the distance from the burner nozzle 13 to the surface of the parts to be welded 1 12-15 mm, for welding the root pass, a nozzle with a diameter of 13 mm and a length of 66 mm was used. After welding pass No. 1, the seam was cleaned along the entire length, upon completion of the cleaning, visual and measuring control was carried out, all identified defects were removed using burrs, followed by cleaning along the entire length of the welded joint. Next, welding of passes from No. 2 to No. 6 on side (A) according to the TC was carried out, between the passes cleaning was carried out along the entire length of the welded joint, visual and measuring control in the amount of 100% and removal of defects, upon reaching an angular deformation of 9 mm in the welded structure, The parts to be welded 1 were prepared for turning from side (A) to side (B) using positioner 8. To do this, the system of preliminary and concurrent heating was turned off, the self-propelled welding tractor 12 and the feeder were dismantled, after turning from side (A) to side ( B) for further work, the removable lining 17 was removed and the root weld was removed from the side (B) by 8 mm and it was cleaned along the entire length, then a self-propelled welding tractor 12 was attached to the side (B), the feeder and the system of preliminary and accompanying heating, welding of passage No. 1 on side (B) was carried out in accordance with the TC with an individual approach for choosing the angle of inclination on the welding torch 13. after welding the pass, the seam was cleaned along the entire length, upon completion of the cleaning, visual and measuring control was carried out, all identified defects were removed using burrs, followed by cleaning along the entire length of the welded joint, then the welding of passes from No. 2 to No. 9 according to the TC on the side (B) with an individual approach for choosing the angle of inclination of the welding torch 13. between passes, cleaning was carried out along the entire length of the welded joint, visual and measuring control in the amount of 100% and removal of defects, upon reaching an angular deformation of 5 mm in the welded structures, parts to be welded 1 were prepared for turning from side (B) to side (A) using positioner 8. equipment was switched off, removed and installed in the same order as when turning from side (A) to side (B), after the overturn from side (B) to side (A), passes No. 5 and No. 6 on side (A) were cleaned from oxides, welding of subsequent passes on side (A) was carried out It is carried out according to the table of welding modes, as well as with an individual approach for choosing the angle of inclination of the welding torch 13 before the start of the welding process in accordance with the TC from No. 7 to No. 33, cleaning was carried out between passes along the entire length of the welded joint, visual and measuring control in the amount of 100% and removal of defects, as well as measurements of angular deformations of parts with their recording in the welding log, passes from No. 29 to No. 33 of side (A) were cleaned along the entire length of the welded joint, then visual-measuring and capillary control was carried out for the presence of pores, undercuts , sagging, etc.. when defects were detected, they were sampled with a burr-cutter, followed by cleaning and welding using an argon-arc welding with a non-consumable electrode (TIG), upon completion of work, the parts were turned over from side (A) to side (B), after overturn from side (A) to side (B), passages No. 7, No. 8 and No. 9 on side (B) were cleaned from oxides, welding of subsequent their passes on the side (B) were carried out according to the table of welding modes, as well as with an individual approach to select the angle of inclination of the welding torch 13 before starting the welding process in accordance with TC from No. 10 to No. measurement control in the amount of 100% and removal of defects, as well as measurements of the angular deformations of the parts to be welded 1 with their recording in the welding log, passes from No. 32 to No. 35 of side (B) were cleaned along the entire length of the welded joint, then a visual measuring and capillary control for the presence of pores, undercuts, sagging, etc., as well as control of changes in the geometry and shape of the aluminum structure, if defects were detected, they were sampled with a burr, followed by cleaning and welding using an argon-arc welding unit with a non-consumable electrode ( TIG). After penetration of all 68 passes, X-ray quality control of the welded joint of the aluminum structure was performed and defects were corrected.

Also, the performance of the above method was successfully proven in welding parts with a straight profile 120 and 150 mm thick made of aluminum-magnesium alloy grades other than AMg5. The method for performing edge cutting can also be used for small dimensions of aluminum-magnesium alloy parts with a thickness of 100 mm or more.

Claims (4)

1. A method for pulse-arc welding with a consumable electrode of parts with a thickness of more than 100 mm from an aluminum-magnesium alloy, including the formation of an X-shaped profile of the welded edges, each of the edges containing a central linear section connected by arcuate sections with inclined linear sections of the edge of the welded part, and performing multi-pass welding on each side of the groove to obtain a weld, characterized in that each of the inclined linear sections of the edge profile is made with an additional bevel, the angle of inclination of which is less than the angle of inclination of the said linear section, while the central linear section is made with a chamfer, and before welding the root pass, a removable lining is installed from the side of the chamfers of the central linear sections, and the assembly of the parts to be welded is carried out on a positioner that provides sequential reorientation of the parts during the welding process when performing welded passes. 2. The method according to p. 1, characterized in that the removable lining is made of a material with a melting point higher than that of the parts to be welded. 3. The method according to p. 1, characterized in that welding is carried out with preliminary and concomitant heating of the welding zone. 4. The method according to p. 1, characterized in that welding is carried out at an air temperature of 20 ... 30 ° C and a relative humidity of 50-65%.

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