RU2751203C1 - Method for electron ray welding of annular or circular joints from copper alloys - Google Patents

Abstract

FIELD: welding.SUBSTANCE: invention relates to a method of electron ray welding of annular or circular joints of copper alloy parts and can be used in mechanical engineering, aircraft construction, nuclear power, petrochemical, gas and other branches of industry. The parts prior to welding are chemically treated, passivated, the welded edges are mechanically cleaned and dehydrated. The welded parts are installed in the apparatus, tight contact of the welded edges is ensured without displacement in height. The position of the focus of the electron ray above the surface of the welded parts is set forming a focusing point at the junction of the parts. Holders are made. Electron ray welding is performed. The focusing point is moved along a translational-circular path relative to the junction of the parts. The electron ray current is increased to the operating mode at the ray input section. The ray current is maintained at the set level. The welding speed is consequently increased in the defined circular joint sections up to the overlap area and within the weld overlap area. The electron ray current is then reduced to zero at the ray output section. A weld is formed in suspension with a through weld penetration of the parts and with the required reinforcement of the weld on the reverse side.EFFECT: invention provides welds without defects, irregularities and splashes of melt with reduced level of internal welding stresses in the weld and reduced deformation of the welded joint structure.4 cl, 9 dwg, 1 tbl

Description

Technology area

The invention relates to the field of welding, in particular, to a method of electron beam welding of copper alloys with controlled through penetration, formation of a weld by weight and extends to the production of circular or circular welded joints. The invention can be used in nuclear energy, mechanical engineering, aircraft construction, space and other industries.

Prior art

The known method, which received the patent of the Russian Federation No. 2433023 "Method of electron beam welding" IPC (51): B23K 15/00, B23K 28/02 priority from 16.02.2010, published 10.11.2011, authors: Dragunov V.K ., Ovechnikov S.A., Chepurin M.V., Alexandrova O.P., Golubchik PM (RU), patentee: State educational institution of higher professional education "Moscow Power Engineering Institute" (GOUVPO "MPEI (TU)") (RU).

The method includes the formation of an electron beam, its deflection and movement relative to the axis of the gun, the location of the focus of the beam inside the welded part and maintaining the position of the focus of the beam in the thickness of the welded part constant. The deflection and movement of the electron beam from the axis of the gun is carried out by alternating current to the lower part of the workpiece to be welded through current leads, which are located on both sides symmetrically to the joint at a distance between them equal to the width of the weld in the upper part of the workpiece to be welded. In this case, the magnetic field is moved in the direction of welding at a speed equal to the speed of the electron beam, and the value of the variable current supplied through the current leads is selected from the condition of ensuring the width of the weld of the root zone equal to the width of its upper part.

Signs that coincide with the essential features of the claimed invention are the formation of an electron beam and maintaining the position of the focus of the beam in the thickness of the welded part constant.

The disadvantage of this method is the complexity of the technological process associated with the deviation of the electron beam from the axis of the gun due to the supply of alternating electric current to the lower zone of the parts to be welded and the subsequent formation of a magnetic field and its movement during welding. An increase in the width of the root part of the seam leads to an increase in the size of the heating zone, which, in turn, can lead to an increase in the level of internal welding stresses in the seam. In addition, the quality of the formation of the weld root depends on the degree of deflection of the electron beam from the axis of the gun, on the magnitude of the alternating electric current. The presence of deviations from the alignment of the electron beam and the current lead and the inequality of the welding speed and the speed of movement of the current leads can lead to a violation of the stability of the formation of the weld and the appearance of root defects in the welded joint.

The known method, which received RF patent No. 1568376 "Method of electron beam welding with regulation of heat input along the length of the joint" IPC: B23K 15/00, priority 02.10.1987, published 30.11.1994, authors: V.V. Melyukov. (RU), patentee: V.V. Melyukov

The method provides for a smooth increase in the beam current at the initial stage of welding up to the operating value, then a slight decrease in this current during the passage of the beam along the entire joint with the formation of the weld. At this stage, the beam current is reduced either linearly or exponentially. Due to this, a constant temperature in the welding tone is ensured in any part of the girth joint. In the initial period of welding, within the time interval from t ₁ to t ₂ , the electron beam current gradually increases to the operating value, then the beam current is maintained at a given level within the time interval from t ₂ to t ₃ , followed by a decrease in the beam current at the stage of overlapping the weld and withdrawal of the welding crater within the time interval from t ₃ to t ₄ , characterized in that, in order to improve the quality of welding of circular joints by reducing overheating in the welding zone with closed heat fluxes along the axis of the circular seam, the beam current within the time interval from t ₂ to t ₃ smoothly decrease.

Signs that coincide with the essential features of the claimed invention are: in the initial period of welding, the electron beam current is gradually increased to the operating value, then the beam current is maintained at a predetermined level, and the beam current is reduced at the stage of extracting the welding crater.

The disadvantage of this method is the limited number of zones (3 sectors) to control heat input along the axis of the annular seam. To obtain a welded seam with an optimal shape with strictly regulated parameters along the width and convexity of the seam, it is necessary to control heat input throughout the entire joint with an assessment of the effect of autoheating in different sectors of the ring joint. This is necessary, as a rule, when welding parts made of materials with a high coefficient of thermal conductivity and a low melting point. In the method, the heat input is controlled only by reducing the beam current, under the condition of through penetration in the overlap zone, lack of penetration is possible (since the current value decreases from the operating value to 0).

Of the analogs, as a prototype, RF patent No. 2433024 "Method of electron beam welding of non-magnetic metals and alloys" was chosen: priority on June 16, 2010, published on November 10, 2011 IPC: B23K 15/00, B23K 28/02, authors : Khokhlovsky A.S., Martynov V.P .. Golubchik PM. Sayapin A.S. (RU), patentee: State educational institution of higher professional education "Moscow Power Engineering Institute (Technical University)" (GOUVPO "MPEI" (TU) ») (RU).

The method of electron beam welding of non-magnetic metals and alloys, including the penetration of the joint of the parts to be welded with an electron beam, the creation of a magnetic field inside the parts to be welded and the formation of a given geometry of the electron beam and the penetration channel when the electron beam is deflected along the thickness of the parts, characterized in that blind penetration of the joint is carried out, while in the process of welding, the deflection of the beam is carried out across the joint and the shape and dimensions of the weld root are changed at a constant size of the weld apex inside the parts to be welded from the side of the weld root with an alternating magnetic field.

Signs that coincide with the essential features of the claimed invention are: a method of electron-beam welding of non-magnetic metals and alloys, including the penetration of the joint of the parts to be welded with an electron beam, the formation of a given geometry of the electron beam, and the movement of the electron beam.

The disadvantage of this method is the low strength of the weld with blind penetration of the joint of the parts to be welded. Also, the deflection of the electron beam across the weld leads to the expansion of the root of the weld. which can lead to an increase in the level of welding stresses and deformation of the structure.

Disclosure of invention

The problem to be solved by the claimed invention is to increase the strength of welded joints while improving the stability of the formation of a welded seam by weight with a controlled penetration penetration to ensure the required values of the seam convexity on the reverse side.

The technical result achieved by solving this problem consists in obtaining welded seams without defects, irregularities and splashes of molten metal and reducing the level of internal welding stresses in the seam and reducing the level of deformation of the welded joint structure.

The technical result is achieved by the fact that in the method of electron beam welding of copper alloys with through penetration, including the penetration of the force of the welded parts with an electron beam, the formation of a given geometry of the electron beam, the movement of the electron beam, according to the invention, before welding the parts are chemically etched, passivated, the welded edges are mechanically cleaned, dehydrated. The parts to be welded are installed in the device, ensure tight contact of the welded edges without displacement in height. The position of the focus of the electron beam above the surface of the parts to be welded is set to obtain a focusing spot at the junction of the parts. Carry out potholders. Electron beam welding is performed. In this case, the focusing spot is moved along a progressive circular path relative to the joint of the parts. The current of the electron beam is increased to the operating mode at the section of the beam input. Maintain the beam current at a predetermined level. The welding speed is sequentially increased in the given sectors of the circular joint up to the overlap zone and in the seam overlap zone itself. Then, the electron beam current is reduced to zero at the beam output portion.

The combination of the above essential features provides a technical result - obtaining welded seams without defects, irregularities and splashes of molten metal, reducing the level of internal welding stresses in the seam and deformation of the welded joint structure, which makes it possible to solve the problem of increasing the strength of welded joints while improving the stability of weld formation by weight with a controlled penetration to ensure the required values of the seam convexity on the reverse side.

It is possible that a weld bead is formed on the weight with a through penetration of the parts and with the necessary convexity of the seam on the reverse side. It is possible that the tacks are made with short sections of the seam with an electron beam at four diametrically opposite points at the junction with an effective beam power equal to 30% of the effective effective beam power during welding. This ensures the accuracy of the arrangement of parts in the butt zone (without displacement) during the welding process and thereby reduces the level of internal welding stresses and deformation of the structure.

Possibly, to obtain a focusing spot at the junction of parts, the value of the focusing current of the electron beam is set to be 10% higher than the value of the current of sharp focusing of the beam. This contributes to the formation of a high-quality weld without defects and shape distortions in the form of irregularities and splashes of molten metal.

Brief Description of Drawings

FIG. 1 shows the structure of a welded joint without grooving.

FIG. 2 shows an external view of a cross-section of a welded joint with defects.

FIG. 3 shows the connection of parts by electron beam welding.

FIG. 4 shows the weld overlap zone.

FIG. 5 shows a graph of the dependence of the weld bulge on the reverse side of the angle of the girth joint sector with constant welding modes.

FIG. 6 shows a graph of the dependence of the convexity of the seam from the back side depending on the angle of the sector of the girth joint when changing the welding speed in different sectors.

FIG. 7 shows a schematic representation of the process of performing electron-beam welding of a circular joint with a controlled convexity of the seam on the reverse side.

FIG. 8 shows a graph of the back side bead bulge versus the girth sector angle after adjusting the welding speed in different sectors.

FIG. 9 shows an external view of a cross-section of a welded joint without defects.

Embodiments of the invention

The method described in the patent can be used to weld circular and ring joints of parts. Next, one of the embodiments of the invention will be described - electron-beam welding of model samples in the form of ring joints of tubular billets made of high-purity copper (oxygen-free copper). The thickness of the samples under study is 3.0 mm. The main condition for obtaining high-quality seams is welding with a through penetration without defects and ensuring the bulge of the welded seam on the reverse side of no more than 8% of the thickness of the parts to be welded (0.24 mm). To estimate the size of the seam bulge on the back side, the ring joint is divided into sectors with a step of 60 ° for FIG. 5 and with a step of 40 ° for FIG. 6 and 8.

As shown in FIG. 1, parts 1 and 2 of a cylindrical shape are involved in welding without cutting the edges to be welded (butt joint).

Electron beam welding of parts 1 and 2 made of copper is carried out as follows. For stable formation of the weld, the surfaces to be welded are cleaned from contamination. For this, parts 1 and 2 are chemically etched and passivated before welding. The passivation process consists in creating on the surface of the welded parts 1 and 2 thin layers of joints in the form of an oxide film, which provide protection against corrosion. After that, the edges of parts 1, 2 and especially their end surfaces are subjected to mechanical cleaning with a scraper, followed by wiping with a coarse calico napkin moistened with alcohol. This brings the surfaces to be welded to the required cleanliness and. thus, the influence of local contamination on the quality of the welded seam is excluded. Below is a table of the influence of the preparation of the welded edges on the quality characteristics of the weld. The results are obtained from experiments. The weld section with defects, obtained as a result of the preparation of the edges without mechanical stripping, is shown in FIG. 2.

Table 1 shows that the absence of defects is observed with a full cycle of preparation of the welded edges in the form of chemical etching, passivation, mechanical cleaning and wiping with a coarse calico napkin moistened with alcohol. Pores 3 (in Fig. 2), which are formed during the preparation of the welded edges without mechanical cleaning, are stress concentrators in the weld, reduce the working section and strength properties of the seam. They can also lead to structural failure due to the accumulation of internal welding stresses and deformation of the welded joint.

Parts 1 and 2 are installed in the assembly and welding device, provide tight contact of the welded edges without displacement in height, as shown in Fig. 3. Set the position of the focus of the electron beam 4, generated by the electron beam gun 5, over the surface of the parts 1 and 2 to be welded to obtain a focusing spot. The value of the focusing current of the electron beam 4 is set to 10% greater than the value of the current of sharp focusing of the beam 4, without displacement relative to the joint 6 (Fig. 3).

The experimental results showed that at a focusing current of less than 10% of the current of sharp focusing of beam 4, a weld with defects in the form of irregularities and splashes of molten metal is formed. In addition, there is an excess of the required values of 0.24 mm of the weld bulge on the reverse side with the formation of single pores 3 in the weld root.

At a focusing current of more than 10% of the current of sharp focusing of beam 4, the degree of concentration of beam 4 in the joint area 6 decreases and the zone of thermal action of the electron beam 4 and the seam width increases, since the focus of beam 4 is located even higher relative to the surface of parts 1 and 2. This increases the level welding stresses in the seam and deformation of the joint structure. It also leads to a decrease in the depth of penetration or to the appearance of a defect in the form of lack of penetration, which is a concentrator of welding stresses and reduces the strength of the seam.

After establishing the focus, tacking with an electron beam 4 is performed in short sections at four diametrically opposite points at the joint 6 with the effective power of the beam 4 not less than 30% of the main effective power of the beam 4 during welding. Tacking is performed in order to exclude possible warpage and gaps during the welding process.

The results of the experiments showed that when tacking with an effective power of beam 4 less than 30% of the operating effective power of beam 4, partial melting of the welded edges occurs without mutual mixing of the metal or lack of fusion of the edges. This can lead to a decrease in the strength and rupture of the tack welds during exposure to the thermal welding cycle, since during welding during the heating process, the welded edges expand.

When making tacks with an effective power of the beam 4 more than 30% of the operating effective power of the beam 4, excessive heat input from the welding source is realized and the penetration depth increases. After welding, this leads to exceeding the permissible values for the convexity of the seam on the back side in the areas where the tacks are located.

Electron beam welding is performed in the lower position on an automated installation. When welding in the lower position, the parts 1 and 2 to be welded rotate around the axis 7 located in the horizontal plane and perpendicular to the axis 8 of the electron beam 4. In addition, high-frequency rotation of the beam 4 about its axis 8 is provided. Beam 4 moves along a circular path with a small diameter, about 0.5 mm. This provides an improvement in the structure, mechanical properties and continuity of the weld metal, prevents lack of fusion of the edges on the reverse side of the weld and excludes the appearance of defects in the form of pores.

At the stage of preliminary work, experimental studies were carried out on the welding of model samples. On the first sample, in the range of set values of the welding current with the remaining parameters of the mode being constant, the reference value of the through-penetration current was determined. At a given value of the welding current, a constant welding speed and the constancy of the other parameters of the mode, the following model sample was welded. At the same time, a regularity was revealed of the increase in the bulge of the welded seam on the reverse side before the beginning of the overlap zone 9 of the seam and in the overlap zone 9. The overlap zone 9 (Fig. 4) is a section of the weld seam, which is determined by the distance of the "superimposed" layer relative to the point 10 of the beginning of welding to the point 11 of the end of welding.

The increase in the bulge of the welded seam on the reverse side occurs due to the high coefficient of thermal conductivity of copper and the manifestation of the auto-heating effect. The effect of autoheating is accompanied by a change in the conditions for the formation of the weld due to the counter effect of the heat front propagating from the point 10 of the beginning of welding, which contributes to an increase in the geometric dimensions of the weld and its bulge towards the end of welding according to the power law in accordance with the empirical formula y = 4E-08x ³ -2E- 05x ² + 0.0046x + 2.83 as shown in FIG. five.

In the range from 0 ° to 60 °, the value of current and welding speed is smoothly increased from 0 to operating values. In this range, the seam bulge on the reverse side is up to 0.1 mm, the value of which can be neglected.

In the range from 60 ° to 180 °, the seam bulge on the reverse side increases in the allowable range from 0.1 to 0.12 mm, which is 50% of the maximum allowable seam bulge on the reverse side.

In the range from 180 ° to 330 °, there is a further increase in the seam bulge on the reverse side to the maximum allowable value of 0.24 mm. In a sector with an angle of 330 °, the convexity is the maximum permissible value of 0.24 mm.

At the beginning of the overlap zone 9 from point 10, the bulge is 0.32 mm, which exceeds the required value by 1/3 part. To reduce the value of the seam bulge on the reverse side to the required value up to 0.24 mm, it is necessary to reduce the effect of autoheating along the entire length of the joint.

To reduce the effect of auto-heating along the entire length of the circumferential joint, a welding option was used with a sequential increase in the welding speed from 1200 to 1600 mm / min, as shown in Fig. 6. In the range of angles from 0 ° to 280 °, the welding speed is 1200 mm / min, while the maximum value of the seam bulge on the back side is 0.15 mm.

As shown in FIG. 6, in the range of angles from 280 ° to 330 °, the welding speed was increased to 1300 mm / min. In this case, the maximum value of the seam bulge on the reverse side decreased. A further increase in the welding speed in the range from 330 ° to 355 ° leads to a significant decrease in the bulge of the seam on the back side to lack of penetration. To align the weld bulge within the permissible values, the welding speed values were experimentally adjusted throughout the joint, as shown in Fig. eight.

These corrected values of the welding speed in the specified sectors of the weld joint were applied when welding the specimen in accordance with FIG. 7. In this case, the values of the bulge on the reverse side of the seam of the entire joint did not go beyond the permissible limits (0.18-0.24 mm), as shown in FIG. eight.

In the range from 0 ° to 5 °, fig. 7, there is an increase in the current of the electron beam 4 from 0 to the operating value, this interval is the section of the beam input. A smooth increase in the current of the electron beam 4 ensures the stability of the formation of the weld and more uniform heating, eliminates the appearance of defects in the form of splashes of molten metal.

In the range from 5 ° to 280 ° (Fig. 7.8), the welding speed is 1230 mm / min. The maximum value of the back seam bulge for the interval from 5 ° to 280 ° is 0.14 mm, as shown in FIG. eight.

In the range from 280 ° to 330 ° (Fig. 7, 8), the welding speed is 1290 mm / min. The back seam bulge value for this interval is 0.15 mm. as shown in FIG. eight.

Further increase in welding speed to 1340 mm / min in the range from 330 ° to 355 °, increase to 1380 mm / min in the range from 355 ° to 375 °. further up to 1550 mm / min in the range from 375 ° to 395 °, as shown in FIG. 7, ensures the value of the bulge of the seam on the back side within acceptable limits. The maximum seam bulge on the back side is 0.18 mm, as shown in FIG. eight.

In the range from 395 ° to 415 ° (Fig. 7, 8) to the point 11 of the end of welding, the current of the electron beam 4 gradually decreases from the operating value to 0. This interval is the section of the beam output. In this case, the welding speed in the range from 395 ° to 415 ° is 1550 mm / min. A smooth decrease in the current of the electron beam 4 excludes the formation of possible defects in the form of a crater and undercuts, which are stress concentrators in the seam and can lead to a decrease in the strength of the seam and a violation of the required convexity of the seam on the reverse side.

In the process of welding with an increase in the welding speed in the sectors up to the beginning of the overlap zone 9 and in the zone of the overlap 9 itself, the parts 1, 2 are melted and a weld seam 12 is formed, FIG. 9, by weight (with through-penetration of the welded edges without the use of backings).

After weld 12 has crystallized, FIG. 9, a permanent connection of parts 1, 2 is formed. According to the results of metallographic analysis of the seam, no internal defects were found in it. The welded seam 12 is formed with a through penetration without the formation of defects and with a convexity of the seam 12 on the reverse side of not more than 0.24 mm (8% of the joint thickness). Thus, a change in the welding speed in different sectors of the girth joint provides uniform heat input along the entire length of the joint 6, the required configuration of the weld 12 and, thereby, reduces the level of internal welding stresses and deformation of the structure as a whole.

Industrial applicability

The most effective use of the proposed method in extended structures of variable cross-section in the form of closed bodies, containers, pipes, closed vessels operating under conditions of a pulse increase in temperature and pressure of an internal aggressive medium, dynamic loads, etc. Where it is necessary to connect parts with controlled through penetration, and with increased requirements for manufacturing accuracy, and for the quality of welds.

The proposed method provides the technical effect, which consists in obtaining welded seams without defects, irregularities and splashes of molten metal and reducing the level of internal welding stresses in the seam and deformation of the welded joint structure. The considered embodiment of the invention was implemented on existing equipment using existing materials. This confirms its performance and industrial applicability.

Claims (4)

1. The method of electron beam welding of circular or circular joints of parts made of copper alloys, including the formation of a given geometry of the electron beam, the movement of the electron beam and penetration of the joint of the parts to be welded with an electron beam, characterized in that before welding, the parts are prepared by chemical etching, passivation, mechanical cleaning of the welded edges and dehydration, then the parts to be welded are installed in the device ensuring tight contact of the edges to be welded without displacement in height, the position of the focus of the electron beam is set above the surface of the parts to be welded to ensure the location of the focusing spot on the welded joint of parts and tacking is performed, then an electron-beam welding the joint of parts with simultaneous high-frequency rotation of the electron beam relative to its axis and form a welded seam on the weight with through penetration of parts and with a given convexity of the seam on the reverse side, with this ohm in the beam input section smoothly increase the electron beam current to the working value and maintain it during welding to the overlap zone, where the electron beam current is reduced to zero value, and the welding speed is sequentially increased to the maximum welding speed at which the admissible value of the weld bulge is ensured on the back of the joint. 2. The method according to claim 1, characterized in that the parts to be welded are rotated around an axis located in the horizontal plane and perpendicular to the axis of the electron beam. 3. The method according to claim. 1, characterized in that the tacks are made in short sections at four diametrically opposite points at the junction with the power of the electron beam, which is 30% of the working power of the beam during welding. 4. The method according to claim 1, characterized in that the focusing spot is obtained at the junction of the parts when the value of the focusing current of the electron beam is 10% higher than the value of the current of the sharp focusing of the beam.

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