Electron beam welding method for thick-wall revolving body component made of magnetic material

Abstract

The invention belongs to the field of material processing and manufacturing, and relates to an electron beam welding method for a thick-wall revolving body component made of a magnetic material. Comprising the steps that a butt joint gap is accurately repaired and matched, corner ridges of upper and lower edges of the butt joint surface are kept, and a mark is manufactured on one side of the butt joint gap; the residual magnetism amount of the material after demagnetization before welding is accurately controlled, and the difference of the residual magnetism amount of the two sub-parts is not larger than 1GS; the inner bushing ring of the designed circular seam has an inverted trapezoidal cross section, the wide end of the inner bushing ring is matched with the inner wall of the cylindrical rotary body, and the narrow end of the inner bushing ring is matched with the inner wall of the conical rotary body; the rotary body component is supported through the component clamping tool, pressure is provided for the rotary body component along the two axial ends, and assembling and positioning of the component to be welded are achieved; welding is conducted in the mode that an electron beam gun is fixed and a rotary body component rotates; and an arc suppression path and an arc suppression beam attenuation form are designed, so that the welding defects of a starting point and an ending point are eliminated.

Description

Technical Field

[0001] The present invention belongs to the field of material processing and manufacturing, and relates to a welding method for rotary components. Specifically, it relates to an electron beam welding method for thick-walled rotary components made of magnetic materials. Background Art

[0002] Sleeve parts, as a transmission component for mechanical motion, are widely used in the field of connecting components with relative motion. They can ensure a certain stiffness while having flexible degrees of freedom in the direction where relative motion is required. With the gradual penetration of the design and manufacturing concepts of green manufacturing and energy conservation and consumption reduction, hollow shafts have gradually become the main structural type. The traditional manufacturing method of hollow shafts is to machine a through hole in the center of the shaft from a bar stock to form an axially symmetric shaft component. However, to meet the needs of some special occasions, some hollow shafts have a relatively thick wall thickness, and their outer shape and dimensions are not symmetric in space, with a smaller shaft port diameter and a larger inner cavity diameter, and they basically do not have the conditions for mechanical hole machining. Therefore, the hollow shaft needs to be divided into two sub-components in the middle, and the two sub-components are manufactured separately and then welded together. Due to the low energy density of the heat source in the traditional arc welding method, the welding heat input is large, and the post-weld deformation exceeds the standard seriously, which cannot meet the current high-precision manufacturing requirements. Therefore, it has gradually been replaced by electron beam welding with a higher energy density and suitable for forming medium-thickness materials. To meet the requirements of high strength and high toughness for shaft parts, some trace elements are added during the material manufacturing process to make the material magnetic. The welding of magnetic materials will affect the incident position and thus affect the heating and flow behavior of the molten pool. Therefore, controlling the heating and flow behavior of the molten pool has become one of the key points. When welding circumferential seams, there are no conditions for using starting and ending arc plates, and the quality control of starting and ending arcs involved is related to the quality of the final product. For the circumferential seam welding of a closed cavity, secondary processing cannot be carried out after welding, and removing the bottom weld where electron beam welding is prone to defects is the core point for protecting the weld quality. In addition, the pre-weld assembly accuracy and clamping and fixing mode, as important factors for improving the welding accuracy of components and controlling welding deformation, have also become an aspect that needs to be mainly considered during process design. Summary of the Invention

[0003] In view of the problems occurring in the electron beam welding of the hollow shaft of magnetic materials mentioned above, the present invention proposes an electron beam welding method for thick-walled rotary components of magnetic materials, which completes the welding of the circumferential weld of the rotary body by the method of keeping the electron beam gun stationary and rotating the component to be welded; designs a special clamping and fixing device to support the rotary body during the welding process and apply pressure along the axial direction, improving the consistency of the component state and the stability of the welding molten pool during the welding process, preventing the weld bead from cracking or the size of the butt joint gap that has not been welded exceeding the standard due to welding deformation; designs the circumferential allowance of the component to be welded to provide machining allowance for the secondary machining of the outer surface after welding, improving the tolerance of the component to the undercut on the front side of the welding, controlling the shape of the butting surface, and improving the butt joint accuracy before welding; adds and designs an inverted trapezoidal filling ring at the back of the weld, selects the electron beam penetration welding mode, introduces the bottom of the molten pool into the backing ring, and avoids residual welding defects in the effective weld bead of the component; controls the incident position of the electron beam, optimizes the effective welding parameters to promote the flow of the molten pool and improve the backfill rate of the molten pool to the small hole, suppressing the generation of weld bead lack of fusion defects; increases the scanning path during the welding process, improves the fluidity of the molten pool and the tolerance of the molten pool to the butt joint gap, improves the joint tissue characteristics, and improves the mechanical properties of the joint; designs the starting and ending arc lap size, adjusts the attenuation form of the ending arc beam current, and improves the starting and ending arc quality of the weld bead. The electron beam welding method for thick-walled rotary components of magnetic materials proposed by the present invention can greatly improve the process window for the stable forming of thin plate welding, significantly improve the processing and manufacturing efficiency, and improve the processing and forming accuracy.

[0004] The technical solution adopted by the present invention is as follows:

[0005] An electron beam welding method for thick-walled rotary components of magnetic materials, the steps are as follows:

[0006] Step (1) precisely repair and match the butt joint gap, keep the corner edge lines of the upper and lower edges of the butting surface, and make a mark on one side of the butt joint gap to improve the accuracy of the path teaching before welding; precisely control the residual magnetism of the material after demagnetization before welding, and the difference in residual magnetism between the two rotary body sub-components, namely the cylindrical rotary body and the conical rotary body, is not more than 1 GS;

[0007] Step (2) design the internal backing ring of the circumferential weld to have an inverted trapezoidal cross-section, which can not only support the welding molten pool of the weld bead and guide the elimination of the tip defect, but also reduce the weight of the backing ring. Among them, the wide end of the internal backing ring is matched with the inner wall of the cylindrical rotary body, and the narrow end of the internal backing ring is matched with the inner wall of the conical rotary body to prevent the internal backing ring from moving during the subsequent clamping of the component;

[0008] Step (3) after assembling the internal backing ring, support the rotary body component through the component clamping tooling and provide pressure to the rotary body component at both axial ends, so that the butt joint gap of the rotary body component always remains under pressure during the circumferential weld welding process, suppressing the exceeding of the gap size caused by welding deformation, and realizing the assembly and positioning of the component to be welded;

[0009] Step (4) adopts the form of welding in which the electron beam gun is fixed and the rotating body component rotates. In order to improve the flow capacity of the molten pool and make the backfilling process of the welding hole periodically stable, the incident point of the electron beam is determined to be the highest point of the annular seam of the shaft component to be welded as the reference point, and the welding hole is offset along the rotation forward direction during welding, so that the welding hole is behind the molten pool. The force of the hole on the wall and the molten pool is used to promote the flow of the molten pool, stably fill the hole, and inhibit the formation of unfused defects in the weld. The arc closing path and arc closing beam attenuation form are designed to eliminate welding defects at the starting point and the end point. The details are as follows:

[0010] In step (1), the precise trimming of the joint gap requires that the joint surfaces are fitted and the gap is not greater than 0.1 mm, and the annular edges of the outer and inner surfaces of the joint surfaces are not chamfered to prevent the groove formed by the chamfer from reducing the subsequent welding path teaching accuracy and causing the molten pool to shift and affect the welding quality. In addition, an arrow mark is made with a marker at any point within 10 mm of the outer surface edge (the arrow points to the joint gap) to prevent the joint gap from fitting too tightly, so that the joint gap cannot be found or the joint gap position is found incorrectly during the welding path teaching.

[0011] In step (2), the inverted trapezoidal inner liner ring is required to have a cross-section of an inverted trapezoid with a wider upper surface and a narrower lower surface, which has a weight-reducing effect compared to a rectangular cross-section liner ring. The upper and lower surfaces of the inverted trapezoid are chamfered to facilitate the guiding and installation of the liner ring. The width of the upper and lower surfaces must be greater than the width of the molten pool to avoid burning of the cross-section during welding and causing the molten pool to flow. The height L must satisfy the relationship between the welding molten pool depth L1 and the wall thickness H of the rotating body component, as shown in formula (1), where L1 needs to be tested for non-penetration welding using the proposed welding process parameters before welding, and the actual measured value of L1 is measured by metallographic observation of the weld.

[0012] L1>L+H+5 mm (1)

[0013] Where: L is the height of the inverted trapezoidal section, L1 is the metallographic measured value of the weld penetration depth in the welding test with the proposed welding parameters, and H is the wall thickness of the rotating body component to be welded.

[0014] In step (3), the assembly and positioning of the component to be welded includes the assembly and positioning of the internal liner ring and the assembly and positioning of the component body, wherein the assembly and positioning of the internal liner ring is to first install the wide end of the internal liner ring into the inside of the cylindrical rotating body, the embedding depth of the internal liner ring is 1 / 2 of the width of the upper surface of the liner ring, and the argon arc welding method is used to perform positioning welding of the spot welding points on the outer edges of the upper surface of the internal liner ring and the inner surface of the rotating body, and then the conical rotating body is installed to the outside of the other end of the internal liner ring and the assembly and positioning of the component body with the atomic parts, ensuring that the assembly gap is not greater than 0.1mm, and the spot welding points are positioned on the upper surface of the rotating body butt gap;

[0015] The assembly positioning of the component body is achieved by installing a component clamping tooling on the component to be welded; the component tooling fixture needs to apply inward pressure and clamp on both sides of the rotating body component along the axis of the rotating body. The component clamping tooling ensures that the clamping force always exists constantly during the welding process of the rotating body, inhibits the excessive deviation of the gap size caused by the thermal deformation of the component, prevents the instability of the welding process and the generation of welding defects. At the same time, an axial surface clamp is added to support the rotating body component. The completed clamped rotating body component is placed horizontally, and a servo motor coaxial with the axis of the rotating body component is installed on the large end side of the rotating body component to make the welding speed steplessly adjustable;

[0016] The described component clamping tooling includes a servo motor, a driving shaft, a driven shaft and two clamps; the clamp includes an upper semi-circle of the clamp and a lower semi-circle of the clamp, which form a complete circular ring structure when combined. A runner is provided on the inner side of the clamp, and the surface of the runner fits with the outer surface of the rotating body to fix the height of the clamp. By fixing the two clamps, the two rotating bodies are coaxially arranged; the driving shaft is located on one side of the cylindrical rotating body, and the driven shaft is located on one side of the conical rotating body. The driving shaft and the driven shaft are respectively in contact with the outer end faces of the cylindrical rotating body and the conical rotating body, and at the same time clamp the rotating body parts to be welded inward, and the axes of the driving shaft, the driven shaft and the two rotating bodies are coaxial; the output shaft of the servo motor is connected to the driving shaft. When the servo motor drives the driving shaft to rotate, the rotating body parts to be welded are subjected to the clamping force existing between the follower shaft and the driving shaft, and then will drive the follower shaft and the two rotating bodies to rotate synchronously;

[0017] In step (4), the method for determining the beam current action position of the electron beam gun is as follows: First, determine the highest point A of the weld bead to be welded on the horizontally placed rotating body and the welding rotation forward direction. Then the beam current action position B should be on the forward side of point A, and the deflection dimension is the connection line BO and AO with the axis O of the rotating body as the reference. The included angle α between BO and AO is 10° - 30°, and the beam current is incident vertically to the horizontal plane at the action position B, and is deflected to make the welding molten pool located on the forward side of the keyhole of the electron beam deep penetration welding, making full use of the pressure of the vapor in the keyhole on the keyhole wall to promote the flow of the molten pool, fill the pores of the molten pool, and inhibit the generation of lack of fusion defects;

[0018] The determination of the welding parameters includes the determination of the effective welding parameters and the arc-retracting parameters. Among them, the effective welding parameters are the parameters for the component to form an effective connection. It selects a welding path with circular wave scanning to form the stirring effect of the keyhole on the molten pool, which is beneficial to broadening the molten pool size, improving the tolerance of the molten pool to the gap, preventing the occurrence of lack of fusion defects, homogenizing the heat distribution in the molten pool, reducing the tissue gradient of the welding joint, and improving the dynamic load performance of the weld seam; while the arc-retracting parameters are to determine the arc-retracting beam current attenuation form. With the starting point C of the arc as the reference, the starting point D of the arc-retracting is designed to be located at the rear side of point C to form an overlapping joint form. The arc-retracting beam current attenuation form is linear attenuation, and the attenuation duration T, the overlapping length of the overlapping joint and the welding speed v should satisfy formula (2),

[0019] T > πD / (3v) (2)

[0020] Where: T is the arc-ending beam current attenuation duration, D is the outer surface diameter of the rotating body, and v is the linear velocity of the outer surface rotation of the rotating body.

[0021] After determining the attenuation duration T, multiply it by the welding speed v to obtain the arc length, thereby determining the arc-ending route.

[0022] Advantages of the present invention:

[0023] (1) Improve the stability of the welding process. Axial pressure is applied to the rotating body component to control welding deformation, inhibit the excessive size of the butt gap during the welding process, which may lead to the instability of the welding process, optimize and determine the deflection and incidence of the electron beam current, control the flow of the molten pool, improve the fluidity of the molten pool, and inhibit defects such as bubbles and lack of fusion.

[0024] (2) Improve the quality of the welded joint. By requiring the fitting accuracy, adopting the circumferential seam lap joint form, combined with the regulation of the arc-ending beam current attenuation, improve the welding quality at the electron beam starting point and the arc-ending point, and avoid the lack of fusion defects at the top and bottom of the joint.

[0025] (3) Improve the mechanical properties of the joint. By adding circular wave scanning during the welding process, promote the stirring effect of the keyhole on the molten pool, improve the uniformity of heat distribution in the molten pool, reduce the tissue gradient of the joint, and improve the dynamic load performance of the joint. Description of the Drawings

[0026] Figure 1 is a schematic diagram of the clamping of the rotating body component and the tooling;

[0027] Figure 2 is a schematic diagram of pre-welding fitting;

[0028] Figure 3 is a schematic diagram of the internal lining ring;

[0029] Figure 4 is a schematic diagram of the assembly and positioning of the component to be welded;

[0030] Figure 5 is a schematic diagram for determining the beam current incidence position;

[0031] In the figure: 1 cylindrical rotating body; 2 conical rotating body; 3 driven shaft; 4 driving shaft; 5 clamp; 6 servo motor; 7 butt gap; 8 internal lining ring; 9 chamfer of the lining ring; 10 fitting surface of the lining ring and the rotating body sub-component; 11 upper surface of the fitting gap of the rotating body component; 12 highest point of the weld bead to be welded; 13 rotation direction; 14 position where the electron beam current acts; 15 electron beam current; 16 axis of the rotating body. Detailed Embodiments

[0032] The following further describes the detailed embodiments of the present invention in combination with the drawings and technical solutions.

[0033] I. Fixture Design

[0034] As shown Figure 1 in the figure, taking the axis of the rotary body component as the reference, driven shafts 3 and driving shafts 4 are added at both ends of the rotary body component, and inward pressure is applied at both ends of the driven shaft 3 and the driving shaft 4 to keep the cylindrical rotary body 1 and the conical rotary body 2 in a clamped state. A clamp 5 is installed, and a servo motor 6 is installed on the large end side (cylindrical rotary body 1) of the component to be welded.

[0035] II. Preparation before Welding

[0036] Before welding, the mating surfaces of the welding beads to be welded of the cylindrical rotary body 1 and the conical rotary body 2 are fitted together. The width of the butt joint gap 7 is not greater than 0.1 mm, and no chamfers are made on the upper and lower edges of the butt joint surface, and the original edges are kept, as Figure 2 shown;

[0037] Before welding, demagnetization is carried out on the cylindrical rotary body 1 and the conical rotary body 2. It is required that the magnetic flux after the demagnetization process is not greater than 1 GS;

[0038] As Figure 3 shown, the internal lining ring 8 is designed as an inverted trapezoid, and chamfers 9 are made at both ends of the upper surface of the lining ring to facilitate the guiding function when the lining ring is assembled with the rotary body sub-component. According to formula (1), the height of the inverted trapezoid cross-section of the back lining ring is calculated to be 4 mm, the width of the upper surface is 20 mm, and the width of the lower surface is 10 mm.

[0039] As Figure 4 shown, for positioning and assembly, first, the wide end of the internal lining ring 8 is inserted into the inner cavity of the cylindrical rotary body 1, so that the embedding depth of the lining ring is 1 / 2 of the width of the upper surface of the lining ring. And at the edge where the upper surface of the lining ring fits with the inner cavity surface of the cylindrical rotary body 1, argon arc welding is used for positioning spot welding along the edge of the lining ring to form the assembly NO1. Then, the conical rotary body 2 is combined with the assembly NO1. It is required that the gap between the fitting surfaces of the cylindrical rotary body part 1 and the conical rotary body 2 is uniform and not greater than 0.1 mm, and the outer surface of the butt joint gap 7 of the rotary body component is spot welded for positioning by argon arc welding to form the assembly NO2 to be welded. Finally, the assembly NO2 to be welded is placed on a special clamping fixture, supported by the lower support rod, clamped and positioned at both ends, and an arrow is drawn with a marker pen on any side of the welding gap, with the arrow pointing in the direction of the gap. The component to be welded after positioning is horizontally placed in the welding station.

[0040] As Figure 5As shown, for the welding path calibration, through the observation holes provided in the design, with the arrow drawn for positioning as a reference, the welding gap to be welded is found. Then, the highest point 12 (point A) of the weld bead to be welded and the welding rotation forward direction 13 are determined. On the rotation forward side of point A, the electron beam action position 14 (the starting arc point B) is determined as the action position of the electron beam 15. It is required that the angles α17 between the lines connecting point A and point B respectively with the axis of rotation of the rotating body 16 (point O) are 20°. Then, the tooling rotating shaft is rotated, and the welding torch is fixed while the component to be welded rotates. The welding path calibration is gradually completed along the annular butt gap;

[0041] The effective welding parameters are determined as follows: Based on the determined annular welding path, when selecting the welding parameters, a circular wave scan is added to form the effective welding parameters (acceleration voltage 90 kV, current 80 mA, focusing current 2 A, rotating shaft speed 5 mm / s, scan amplitude 0.8, frequency 100 Hz). The arc extinguishing parameters are: after completing the circumferential welding and when the molten pool exceeds the starting arc point, the welding current starts to decay, and the decay duration is obtained through formula (2) as 30 s;

[0042] Finally, the equipment is started to complete the welding of the rotating body component.

Claims

1. Electron beam welding method for thick-walled rotary body components of magnetic materials, characterized in that, The steps are as follows: Step (1): Precision fit the butt joint gap, maintain the corner edge lines of the upper and lower edges of the butt joint surface, and make a mark on one side of the butt joint gap; control the residual magnetism after demagnetization before welding, and the difference in residual magnetism between the cylindrical rotating body and the conical rotating body is not more than 1 GS; Step (2): Design the internal lining ring of the circumferential weld to have an inverted trapezoidal cross-section. Among them, the wider end of the internal lining ring is fitted with the inner wall of the cylindrical rotating body, and the narrower end of the internal lining ring is fitted with the inner wall of the conical rotating body; Step (3): After assembling the internal lining ring, support the rotating body component through the component clamping tooling and provide pressure to the rotating body component at both axial ends to achieve the assembly positioning of the component to be welded; the assembly positioning of the component to be welded includes the assembly positioning of the internal lining ring and the assembly positioning of the component body; Step (4): Weld in the form of fixing the electron beam gun and rotating the rotating body component. Determine that the incident point of the electron beam current is offset along the rotation and forward direction during welding with the highest point of the circumferential weld of the shaft component as the reference point, so that the welding hole is behind the molten pool; and design the arc extinguishing path and the arc extinguishing beam current attenuation form to eliminate the welding defects at the starting point and the ending point.

2. The electron beam welding method for the thick-walled rotary body member of the magnetic material according to claim 1, characterized in that In step (1), the requirement for precision fitting the butt joint gap is that the butt joint surfaces are in contact and the gap is not more than 0.1 mm. Chamfers are not made on the annular edges of the outer surface and the inner surface of the butt joint surface, and an arrow mark is made with a marker pen at any point within 10 mm of the outer surface edge.

3. The electron beam welding method for a thick-walled rotary body member of a magnetic material according to claim 1, characterized in that, In step (2), the inverted trapezoidal internal lining ring is required to have an inverted trapezoidal cross-section with a wider upper surface and a narrower lower surface. The width dimensions of both the upper and lower surfaces need to be greater than the width of the molten pool, and the height L needs to satisfy the relationship between the welding molten pool depth L1 and the wall thickness H of the rotating body component, as shown in formula (1): L1>L +H+5 mm (1) In the formula: L is the height of the inverted trapezoidal cross-section, L1 is the measured metallographic value of the weld penetration of the welding test with the proposed welding parameters, and H is the wall thickness of the rotating body component to be welded.

4. The electron beam welding method for a thick-walled rotating body member of a magnetic material according to claim 1, characterized in that, In step (3), for the assembly positioning of the internal lining ring, the wider end of the internal lining ring is first installed inside the cylindrical rotating body, and the embedding depth of the internal lining ring is 1 / 2 of the width of the upper surface of the lining ring. The argon arc welding method is used to perform spot welding positioning at the outer edge where the upper surface of the internal lining ring is in contact with the inner surface of the rotating body. Then, the conical rotating body is installed outside the other end of the internal lining ring and the assembly positioning of the component body is carried out with the original component, ensuring that the assembly gap is not more than 0.1 mm, and spot welding positioning is carried out on the upper surface of the butt joint gap of the rotating body.

5. The electron beam welding method for a thick-walled rotating body component of a magnetic material according to claim 1, characterized in that, In step (3), for the assembly positioning of the component body, the component clamping tooling is installed on the component to be welded; the component tooling fixture presses and clamps inward on both sides of the rotating body component along the axis of the rotating body.

6. The electron beam welding method for thick-walled rotating body components of magnetic materials according to claim 4, characterized in that The described component clamping tooling includes a servo motor, a driving shaft, a driven shaft, and two clamps; the clamp includes an upper semi-circle of the clamp and a lower semi-circle of the clamp, and the two are combined to form a complete circular ring structure. A runner is provided on the inner side of the clamp, and the surface of the runner fits with the outer surface of the rotating body to fix the height of the clamp. By fixing the two clamps, the two rotating bodies are coaxially arranged; the driving shaft is located on one side of the cylindrical rotating body, and the driven shaft is located on one side of the conical rotating body. The driving shaft and the driven shaft are respectively in contact with the outer end faces of the cylindrical rotating body and the conical rotating body, and at the same time clamp the rotating body parts to be welded inwardly, and the axes of the driving shaft, the driven shaft, and the two rotating bodies are coaxial; the output shaft of the servo motor is connected to the driving shaft. When the servo motor drives the driving shaft to rotate, the rotating body parts to be welded are subjected to the clamping force existing between the follower shaft and the driving shaft, and then the follower shaft and the two rotating bodies will be driven to rotate synchronously.

7. The electron beam welding method for a thick-walled rotary body member of a magnetic material according to claim 1, characterized in that, In step (4), the method for determining the beam current action position of the electron beam gun is as follows: First, determine the highest point A of the weld bead to be welded on the horizontally placed rotating body and the welding rotation forward direction. Then, the beam current action position B should be on the forward side of point A. The deflection dimension is the line connecting BO and AO with the axis O of the rotating body as the reference. The included angle α between BO and AO is 10° to 30°, and the beam is incident vertically to the horizontal plane at the action position B, and the deflection incidence makes the welding molten pool located on the forward side of the keyhole of the electron beam deep penetration welding.

8. The electron beam welding method for a thick-walled rotary body member of a magnetic material according to claim 1, characterized in that, In step (4), the determination of the welding parameters includes the determination of the effective welding parameters and the arc extinguishing parameters. Among them, the effective welding parameters are the parameters for the components to form an effective connection, and a welding path with circular wave scanning is selected; The arc extinguishing parameters are to determine the arc extinguishing beam current attenuation form. Taking the starting point C of the arc as the reference, the arc extinguishing starting point D is designed to be located behind point C to form a lap joint form. The arc extinguishing beam current attenuation form is linear attenuation. The attenuation duration T, the lap length of the lap joint, and the welding speed v should satisfy formula (2): T>πD / (3v) (2) In the formula: T is the arc extinguishing beam current attenuation duration, D is the outer surface diameter of the rotating body, and v is the outer surface rotational linear velocity of the rotating body; After determining the attenuation duration T, multiply it by the welding speed v to obtain the arc length, thereby determining the arc extinguishing route.

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