RU2277465C1 - Friction welding method and tool for its implementing - Google Patents

Abstract

FIELD: mechanical engineering; welding.

SUBSTANCE: invention can be used for connecting sheets made of different materials, including unweldable or limitedly by fusion welding. Proposed welding tool has mandrel with support surface on end face rotated around axle and provided with projecting working rod arranged coaxially. Said working rod is dipped in butt joint of members to be connected, and tool is moved with tilting of its axis along butt joint. Plasticized zone is acted upon by pressure built by support end face surface of mandrel and pressure periodically changing in value. Mandrel is made with support surface deflecting from plane perpendicular to its of rotation through angle of 0.5-5.0 degrees. In process of welding mandrel is arranged with possibility of dipping its support surface in edges of sheets to be connected. Improved quality of weld seam owing to creation of tight fine grain structure without microdefects is provided by intensification of weld seam forming process using power frequency pulsation.

EFFECT: improved quality of weld seams.

3 cl, 5 dwg

Description

Technical field

The invention relates to the welding of metals, more specifically to friction welding, and can be used in rocket science, aircraft manufacturing, shipbuilding and other engineering and construction industries for joining sheet metal parts and structural units from various materials, including non-welded and limited welded by fusion for the purpose increase the reliability and strength of welds.

State of the art

A known method of welding metals by friction for joining sheet metal parts, according to which a rotating tool made in the form of a rod with a soldered tip, is immersed in the joint of the parts to be joined and move it along the joint line, transferring the material heated by rotational friction to the area released from behind the moving tool. In this case, when reaching the ductility of materials in the joint zone, an axial force is applied to the tool (see AS USSR No. 195846, class IPC V 23 K, 1967).

The patent for a similar solution, Improving Friction Welding, was granted to the English company The Welding Institute (TWI) - international application WO 93/10935 of 06/10/93 (priority of 1991). Known solutions do not allow to obtain a stably reliable and durable weld.

A known method of friction welding with stirring, mainly for structural elements obtained by pressing, including fitting, installing and securing the connected elements, connecting the elements together by introducing a probe (tool) made with a cylindrical mandrel provided with a supporting surface at the end and a coaxially located tip from a material harder than the materials to be joined, rotated around the axis and moved along the connection line to generate friction heat and created I plasticized zone material elements. In addition, the method includes exposing the plasticized zone to a pressure applied perpendicular to the surface of the materials using the supporting surface, and creating an improved flow of plasticized material perpendicularly and vertically to the edges of the elements to be connected by protrusions on the tip (see international application WO 95/26254, IPC B 23 K 20/12, 1995).

This embodiment of the method, according to the authors, allows to improve the homogenization of the seam and thereby improve its quality. However, this method and tool do not provide guaranteed obtaining a high-quality weld and the absence of discontinuities and inhomogeneities in it.

Disclosure of invention

The objective of the invention is to develop such a method of friction welding using a rotating rod and a tool for its implementation, which would improve the quality of the weld due to the creation of a dense, fine-grained structure and the absence of microdefects.

In accordance with the invention, the task is achieved in that in a method of friction welding, mainly for structural sheet elements, including fitting, installing and securing the joined elements, connecting the elements together by introducing a tool made in the form of a mandrel provided with an abutment surface at the end and coaxially located protruding working rod, rotatable around an axis, immersed by the working rod in the joint of the elements to be connected and moved along it, to generate heat To friction and create a plasticized zone of the material of the elements, the pressure on the plasticized zone by the pressure created by the supporting end surface, the impact on the plasticized zone is carried out by periodically varying pressure using a mandrel made with the supporting surface deviated from the plane of rotation by a predetermined angle.

In addition, in the tool for implementing the method, made in the form of a mandrel associated with a rotation drive and provided with an end face and a coaxially located working rod, the plane of the supporting surface is made deviated from the plane of rotation of the mandrel by an angle equal to 0.5-5 °.

Moreover, in the tool for implementing the method, the supporting surface of the mandrel in the region of a small angle with the side generators of the mandrel is chamfered at an angle to the plane of rotation of the mandrel, equal to 1.05-1.15 (β + α), where β is the angle of inclination of the axis of the tool during welding, α is the angle of deviation of the supporting surface from the plane of rotation.

This embodiment of the method and the tool improves the quality of the weld by eliminating microdefects in the form of discontinuities due to the intensification of the processes of formation of the structure of the weld due to the introduction of frequency power pulsations.

List of drawings

The invention is illustrated by drawings, in which:

- Figure 1 shows a diagram of the implementation of the method in a perspective view with a partial cutout of the sheet along the weld;

- Figure 2 shows a tool for implementing the method with a cut along the axis of the mandrel;

- Figure 3 shows the end part of the tool when conducting welding;

- Figure 4 shows the end part of the mandrel of the tool with a remote working rod;

- Figure 5 shows a view along arrow A of Figure 4.

The implementation of the invention

The process of connecting structural elements, for example, two sheets 1 and 1 'of high-strength aluminum alloy (see Figure 1) "in joint" by the proposed method is carried out in the following sequence.

Sheets 1 and 1 'are assembled in a special assembly-welding fixture (not shown in the drawing). The sheets are adjusted and set, while ensuring the closure of the ends of the edges and the tight fit of the edges to a rigid technological lining. After that, the sheets and the joined edges are fixed. During the welding process, any movement of the edges relative to the clamping device is not allowed.

A tool made in the form of a mandrel 2 provided with a rotation drive at one end and a supporting surface 5 made deflected from the plane of rotation by a predetermined angle and coaxially located protruding working rod is lowered onto assembled, fitted, and fixed in such a way joined connecting sheets. 3. The tool is lowered until the contact of the working rod 3 with the surface of the sheets 1 and 1 '.

The rotation drive 4 is turned on (see FIG. 2) of the mandrel 2 and the rotating working rod 3 is slowly immersed in the joint of the connected elements to generate friction heat and create a plasticized zone of the material of the welded units (as they heat up). The immersion of the working rod 3 is carried out to a predetermined depth, for example, to the thickness of the material being welded until the contact of the supporting surface 5 of the mandrel 2 with the surface of the connected elements (Figure 1). During the immersion of the working rod 3 in the joint, the material around it is heated to a temperature at which it becomes plastic. After that, without stopping the rotation of the working rod 3, begin moving the mandrel with a welding speed V _C along the connection line (Figure 1). The working rod presses on the plasticized material of the sheets to be joined and, rotating, moves the plasticized material to the area that is released behind the moving tool, where a welding seam 6 is formed (Figure 1).

In this case, the plasticized zone is affected by the pressure created by the supporting end surface, due to the constant force exerted on the mandrel along its axis from top to bottom.

To increase the pressure force, the axis of the tool during welding is tilted by a small angle - β (2-3 degrees) (see Figure 3) and the process is conducted with the apex of the angle forward. In this case, the pressure force of the supporting end surface of the mandrel is expanded along the X and Z axes, that is, a force vector appears in the directions along the tool axis (Z) and welding (X), which contribute to better dynamics of the plastic flow of the material and more stable formation of the seam.

In addition to constant pressure, the plasticized zone is affected by periodically varying pressure with the help of a mandrel made with a supporting surface 5 deviated from the plane of rotation 7 by a given angle α.

In the process of moving the rotating tool along the connection line, the supporting surface 5 of the mandrel 2 is deviated from the surface of the joined sheets 1 and 1 'by a constant angle β (about 2-3 degrees) due to the inclination of the tool axis to this angle. To the angle β is added a variable angle α, caused by the deviation of the supporting surface 5 from the plane of rotation 7 of the mandrel. Therefore, at each point on the surface of the sheets to be welded under the supporting surface 5 of the mandrel 2 during its rotation, a periodic alternating immersion of the supporting surface 5 of the mandrel 2 into the edges of the joined sheets with the greatest immersion depth at the joint line behind the moving tool, i.e. in the weld formation zone. As a result, an alternating pressure is created on the weld formation zone with a maximum amplitude value of the variable pressure force behind the working rod 3. This force pulsation increases the dynamics of the deformation of the material and other processes and contributes to the formation of a more dense structure of the weld material, the absence of microdefects in it.

The compaction effect appears in the presence of an angle and increases with an increase in the angle to 4-5 degrees. A further increase in the angle α leads to a violation of the formation of the seam. When choosing the angle α, the thickness of the connected elements and the thermophysical properties of the material of the elements are taken into account. The angle increases with increasing thickness and at lower values of the yield strength of the material of the connected elements.

The tool for implementing the method is made in the form of a mandrel 2 (see FIGS. 2, 3), connected with a rotation drive 4 and provided with an abutment surface 5 and a coaxially disposed working rod 3. The plane of the abutment surface 5 is deviated from the plane of rotation 7 (perpendicular to the axis of rotation 8 of the mandrel 2) at an angle equal to 0.5-5 °.

The rotation drive 4 can be, for example, the drive of a vertically milling machine, in which the tool is installed in the spindle, and the clamping assembly and welding fixture with the joining sheets assembled for welding is mounted on the machine carriage, after which welding is performed.

It should be noted that the supporting surface 5 of the mandrel 2 in practice is performed with a diameter exceeding the diameter of the working rod by about 2-2.5 times.

Since the supporting surface 5 is deflected by an angle α, then (see Figs. 4, 5) it forms an oval with a large axis 9 (axis of symmetry) and a small axis 10. In a section passing through the large axis of the supporting surface 9 and the axis of rotation 8, small 11 and large 12 angles are formed between the supporting surface of the mandrel 5 and the side surface forming it. So that the said small angle does not leave deep scratches on the surface of the weld, the supporting surface in the region of the small angle 11 is made with a bevel 13 at an angle of 14 to the plane of rotation 7 of the mandrel, equal to 1.05-1.15 (β + α), where β - the angle of inclination of the axis of the tool during welding, α is the angle of deviation of the supporting surface from the plane of rotation. The chamfer 13 is formed in the form of a conical surface around the axis of the mandrel 5 and can be made with a maximum size of 17 equal to 0.8-1.5 mm on the major axis.

The working rod 3 can be made interchangeable. It is introduced along the landing landing in the channel of the mandrel 2 to the stop 16 (see FIG. 2) and fixed from falling out of it with a screw 15, and a rigid connection with the mandrel can be made structurally different, for example, via a spline connection. The emphasis 16 on the working rod is made with a diameter exceeding the diameter of the mandrel channel by at least 2.0 mm.

The surface of the working rod 3 can be made with a different relief: screw cutting, protrusions and recesses to enhance the impact on the plastic flow of the material during the welding process.

The proposed method was performed experimental welding of samples from aluminum alloy AMg6. Studies have shown that the resulting weld has a particularly fine-grained metal structure, which increases its reliability and strength characteristics.

Compared with known methods using a tool with a supporting surface lying in the plane of rotation of the tool, the proposed method and tool can improve the stability of obtaining a tight weld even with extreme welding parameters, which increases the reliability of the method.

Claims (3)

1. A method of friction welding, mainly for connecting structural sheet elements, including fitting, installing and securing the elements to be connected, welding with a tool containing a mandrel rotating around an axis, having a supporting surface at the end, equipped with a coaxially protruding working rod, by immersing the working rod in the joint of the connected elements and the movement of the tool with the inclination of its axis along the joint to ensure the generation of heat of friction and create a plasticized zone material of the elements to be connected, wherein the plasticized zone is affected by the pressure created by the supporting end surface of the mandrel, characterized in that the plasticized zone is affected by periodically varying pressure by performing the mandrel with the supporting surface deviated from a plane perpendicular to its axis of rotation for a given angle, and placement of the mandrel with the possibility of immersion of its supporting surface in the edges of the connected elements. 2. A tool for friction welding, comprising a mandrel associated with a rotational drive with a supporting surface at the end, provided with a coaxially projecting working rod, characterized in that the supporting surface of the mandrel is deviated from a plane perpendicular to the axis of rotation of the mandrel by an angle α equal to 0.5 -5.0 °. 3. The tool according to claim 2, characterized in that the supporting surface of the mandrel in the region of a smaller angle with the side generators of the mandrel is chamfered at an angle to the plane perpendicular to the axis of rotation of the mandrel, equal to 1.05-1.15 (β + α), where β is the angle of inclination of the axis of the tool during welding, α is the angle of deviation of the supporting surface from a plane perpendicular to the axis of rotation.

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