RU2714008C1 - Method of friction welding with mixing of aluminum structures and tool for its implementation - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method relates to friction welding with mixing of aluminum structures. Tool with pin, length 4.5–4.9 mm is used, made in the form of cylindrical surface and spherical surface on pin end, radius of which corresponds to 0.7–0.8 of cylindrical surface diameter. Before insertion of the pin into the joint of the parts, sheet parts are fixed on the substrate from the plate with a lower heat conductivity coefficient than that of the material of the parts being welded, which provides heat concentration in the connection zone. Tool is immersed into the joint of the connected parts to the required depth and welding is performed with the tool lengthwise feed of 40–60 mm/min and rotation speed of 560–710 rpm. Tool inclination angle makes 1–3° in the welding direction. Depth of insertion of support tool shoulder is adjusted from 0.1 to 0.2 mm.

EFFECT: invention ensures absence of defects of welded joints and obtaining strength close to that of base metal.

2 cl, 3 dwg

Description

Technical field

The present invention relates to the field of friction stir welding (STF) of aluminum structures and can be used in aviation and space technology, in shipbuilding and other engineering fields.

State of the art

In FIG. 1 shows the STP method. In friction stir welding, the parts to be welded 1 are placed on the substrate 2 and brought into contact with each other, a tool 3 rotating at a high speed is introduced into the contact zone. After this, the tool 3 moves along the connection line 4 with the welding speed. As a result of friction, the metal is heated up to a plastic state, it is mixed with a rotating tool 3 and forced into the free space behind the tool 3 moving along the joint line 4. After welding, the rotating tool 3 is removed from the joint outside the parts 1. Friction with the material being welded causes heat generation due to which the softening of the material occurs. The friction process during STF is accompanied by plastic deformation of thin contact layers in which internal friction is realized. The main functions of the tool 3 are mixing and transferring the material by extrusion between the surface of the tool 3 and the non-softened material of the parts 1, and the shoulder 5 is the creation of excess pressure in the welding zone. The pressure of the shoulder 5 of the tool 3 in the joint zone causes plastic deformation and the flow of plasticized metal, stirred by the tip - pin 6. Thus, the connection is carried out under extrusion conditions with forging of the material at high rates of relative deformation. Weld core 7.

There is a 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 joined parts and moving 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 (AS USSR No. 195846, MPK V23K, 1967).

The well-known "Method of friction welding and a tool for its implementation" (patent RU No. 2277465, IPC V23K 20/12, 2006), in which the welding tool contains a mandrel rotating around its axis with a supporting surface at the end, equipped with a coaxially protruding working one the core. The working rod is immersed in the joint of the elements to be joined and the tool is moved with its axis inclined along the joint. The plasticized zone is affected by the pressure created by the supporting end surface of the mandrel and the pressure periodically changing in magnitude. In this case, the mandrel is made with a supporting surface deviated from the plane perpendicular to its axis of rotation by an angle of 0.5-5.0 degrees. When welding, a mandrel is placed with the possibility of immersing its supporting surface in the edges of the joined sheets. Improving the quality of the seam due to the creation of a dense fine-grained structure and the absence of microdefects is provided by the intensification of the processes of formation of the seam by introducing frequency power pulsations.

Known solutions do not allow to obtain a stably reliable and durable weld.

The closest to the same purpose to the claimed invention in terms of features is a method of friction stir welding, mainly for structural elements, including fitting, installing and securing the connected elements, connecting the elements together by introducing a pin (tool) made with a cylindrical mandrel equipped with at the end of the supporting surface and coaxially located tip of a material harder than the materials to be joined, rotated around an axis and moved in along the joint line to generate heat of friction and create a plasticized zone of the material of the 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 connected elements due to protrusions on the tip (international application WO 95/26254, IPC V23K 20.12. 1995). This method is adopted as a prototype.

Signs of the prototype, which coincides with the essential features of the proposed method, including fitting, installing and securing the connected elements, the connection of the sheet parts with each other by introducing into the joint parts of the tool containing the supporting shoulder and coaxially located pin made of a material harder than the material to be joined parts and rotating around the axis, and moved along the connection line with the impact on the plasticized zone by pressure, apply perpendicular to the surface etaley via the supporting surface of the tool.

This method and tool do not provide guaranteed production of a high-quality weld and the absence of discontinuities, inhomogeneities in it, due to insufficient concentration of heat in the joint zone.

The objective of the invention is the creation of such a welding method and the manufacture of specialized tools for its implementation, which would improve the quality of the weld, due to the selected optimal welding conditions, ensuring the absence of defects and increase the strength of welded joints made by STP, close to the strength of the base metal.

Signs of the proposed technical solution, distinctive from the prototype — before the tool is introduced into the joint of parts, sheet metal parts are fixed with a thickness of 5 mm using technological equipment (drawings are not shown) for further STP execution on a vertically milling machine; as a substrate, a plate made of materials (for example stainless steel) is adopted, with a lower coefficient of thermal conductivity than that of the material of the welded parts, which ensures the concentration of heat in the joint zone. Use a welding tool with a pin made in the length of 4.5 ... 4.9 mm, the design of which is selected as a cylindrical surface and a spherical surface at the end of the pin, based on the ratio that the radius of the spherical end surface corresponds to 0.7-0.8 of the diameter of the cylindrical pin surface and supporting shoulder with a diameter of 17 ... 20 (18 ... 22). The tool is immersed in the joint of the parts to be joined to the required depth and welding is performed with a longitudinal feed of the tool of 40-60 mm / min. and a rotation speed of 560-710 rpm, while the angle of the tool is 1 ° -3 ° in the welding direction.

Distinctive features in conjunction with the known ensure the absence of defects; reduction of thermal energy losses due to the use of a substrate of a material with a lower coefficient of thermal conductivity than that of the material of the welded parts; increasing the strength of the joints. The strength of welded joints under the considered welding conditions is close to the strength of the base metal and is about 95% of the strength of the base metal.

The method is as follows.

Before the STP process, parts (samples), which are aluminum alloy sheets with dimensions of, for example, 1000 × 75 × 5 mm, are placed on a rigid stainless steel substrate. The samples are fastened using the developed technological equipment (drawings are not shown). The distance between the clamps is 95 ... 100 mm, which ensures the rigidity of fixing samples of FIG. 2. In the joint of the parts to be joined, the tool is immersed in the metal to be welded to a depth equal to 0.10 ... 0.2 mm and during welding due to the axial pressing force, it is maintained in this position. During welding, the tool is given a rotation of 560-710 rpm., While the angle of the tool is 1 ° -3 ° in the welding direction.

The essence of the method is as follows: for welding use a welding tool with a pin made in the length of 4.5 ... 4.9 mm, the design of which is selected in the form of a cylindrical surface and a spherical surface at the end of the pin, based on the ratio that the radius of the spherical end surface corresponds to 0 , 7-0.8 from the diameter of the cylindrical surface of the pin and the supporting shoulder with a diameter of 18 ... 22 FIG. 3; before the pin is inserted into the joint of parts, sheet metal parts are fastened with a thickness of 5 mm using technological equipment to perform further STP on a vertically milling machine; as a substrate, a plate made of materials (for example, stainless steel) with a lower coefficient of thermal conductivity than that of the material of the welded parts is adopted, which ensures the concentration of heat in the joint zone and obtaining a softened layer by reducing heat loss. The tool is immersed in the joint of the parts to be joined to the required depth and welding is performed with a longitudinal feed of the tool of 40-60 mm / min. and a rotation speed of 560-710 rpm., while the angle of the tool is 1 ° -3 ° in the direction of welding.

As a result of friction, the metal is heated up to the plastic state, it is mixed with a rotating tool and forced into the vacated space behind the tool moving along the line of junction. The volume in which the seam is formed is limited from above by the supporting shoulder of the tool. At the end of welding, the rotating tool is removed from the joint outside the part. The main function of the supporting shoulder is to create the required heat in the area of the parts connection due to its friction against the surface of the parts when pressure is applied to the tool. The pressure of the supporting shoulder of the tool in the joint zone causes plastic deformation and the flow of plasticized metal, mixed with a profiled pin. Thus, the connection is carried out under extrusion conditions with

forging the material at high relative strain rates. In addition to fixing it on a prepared substrate using technological equipment, the formation of a compound using STP and its quality are influenced by the geometry of the tool and the material for its manufacture. The material should be characterized by high heat resistance and viscosity due to the fact that the tool during welding works in difficult conditions.

For the material selected from tool stamped steel, which has high heat resistance and toughness. The hardness of the tool is in the range 53 ... 60 HRC. The design of the tool pin is selected in the form of a cylindrical surface and a spherical surface at the end of the pin based on the ratio that the radius of the spherical surface corresponds to approximately 0.7-0.8 of the diameter of the cylindrical surface of the pin. This ratio provides good penetration of the joint at the root of the seam. The diameter of the tool pin is selected taking into account the thickness of the material being welded.

Thus, using the new improved design of the tool and method in accordance with the present invention, sufficient heat is generated from friction. This effect is achieved through the use of a rigid substrate with a lower coefficient of thermal conductivity, compared with the coefficient of thermal conductivity of the material of the welded parts, which, combined with the use of an improved tool design, can increase the strength of the welded joint made by STP, close to the strength of the base metal.

Claims (2)

1. A method of friction welding with stirring of aluminum structures from sheet parts, including their installation and fixing, the connection of the sheet parts to each other is carried out by introducing into the joint parts of the tool, made with a supporting shoulder and pin, rotating around an axis, and moving the tool along the line connection with the impact on the plasticized zone by pressure applied perpendicular to the surface of the parts using the supporting surface of the tool, characterized in that the welded sheet your parts are fixed on a rigid substrate made of a plate made of a material with a lower coefficient of thermal conductivity than the parts to be welded, while the tool is immersed in the joint of the parts to be joined at a speed of 560-710 rpm with a longitudinal feed of 40-60 mm / min, the angle of the tool is 1-3 ° to the direction of welding, and the depth of introduction of the supporting shoulder of the tool into the part is regulated from 0.10 to 0.2 mm. 2. A tool for friction welding with stirring of aluminum structures from sheet parts, containing a support shoulder and a coaxially arranged pin made of a material harder than the material of the parts to be joined, characterized in that the diameter of the support shoulder is 17 ... 20 mm and the pin length is 4, 5 ... 4.9 mm, and the pin has a cylindrical surface and a spherical surface at its end, the radius of which is 0.7-0.8 of the diameter of its cylindrical surface.

Images