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EP-4106942-B1 - FRICTION STIR WELDING TOOL, METHOD FOR MANUFACTURING THE TOOL, AND METHOD OF ASSEMBLING WORKPIECES WITH SUCH TOOL

EP4106942B1EP 4106942 B1EP4106942 B1EP 4106942B1EP-4106942-B1

Inventors

  • FIGNER, GUNTER
  • CALISKANOGLU, Ozan
  • OPPENEIGER, Lucas
  • PFEIFFER, CHRISTIAN

Dates

Publication Date
20260513
Application Date
20210201

Claims (15)

  1. A friction stir welding tool (1), which has a pin (2) and a shoulder (3) connected rigidly to the pin (2), for welding components (7) consisting of a parent material that is composed of steel and has a melting point of more than 900°C, wherein said friction stir welding tool (1) particularly is produced in a method according to one of claims 6 to 15, and wherein the shoulder (3) consists at least partially of a first material and the pin (2) consists at least partially of a second material, characterized in that a material pairing of the first material with the parent material has a first coefficient of sliding friction and a material pairing of the second material with the parent material has a second coefficient of sliding friction, wherein the first coefficient of sliding friction is lower than the second coefficient of sliding friction.
  2. The friction stir welding tool (1) according to claim 1, characterized in that the friction stir welding tool (1) has a shaft (4) that contains a third material, particularly is composed of a third material.
  3. The friction stir welding tool (1) according to claim 1 or 2, characterized in that the first material contains molybdenum, particularly is realized in the form of a molybdenum alloy, and/or in that the second material contains tungsten, particularly is composed of tungsten-rhenium.
  4. The friction stir welding tool (1) according to one of claims 1 to 3, characterized in that the first material and/or the second material contains a ceramic material, particularly an oxide ceramic material and/or a nonoxide ceramic material such as carbides, nitrides or silicides or is composed of such a material.
  5. The friction stir welding tool (1) according to one of claims 1 to 4, characterized in that the first material and/or the second material contains a refractory metal, a refractory metal alloy, a nickel alloy, a cobalt alloy and/or an iron alloy or is composed of such a material.
  6. A method for producing a friction stir welding tool (1) that has a pin (2) and a shoulder (3), which friction stir welding tool is capable of connecting components (7) consisting of a parent material that is composed of steel, particularly construction steel, and has a melting temperature of more than 900°C by means of friction stir welding, particularly for producing a friction stir welding tool (1) according to one of claims 1 to 5, wherein a first part (5), which consists of a first material, is connected rigidly to a second part (6), which consists of the second material, such that at least a section of the shoulder (3) is composed of the first material and at least a section of the pin (2) is composed of the second material, characterized in that a material pairing of the first material with the parent material has a first coefficient of sliding friction and a material pairing of the second material with the parent material has a second coefficient of sliding friction, wherein the first coefficient of sliding friction is lower than the second coefficient of sliding friction.
  7. The method according to claim 6, characterized in that the first part (5) is connected integrally to the second part (6), wherein the first part (5) preferably is welded to the second part (6).
  8. The method according to claim 6 or 7, characterized in that the first part (5) is connected to the second part (6) by means of a friction welding process.
  9. The method according to one of claims 6 to 8, characterized in that the first part (5) is connected to the second part (6) by means of a pressure welding process.
  10. The method according to one of claims 6 to 9, characterized in that , depending on a desired average coefficient of sliding friction that acts during a contact of the shoulder (3) with the parent material and lies between a first coefficient of sliding friction of a material pairing of the first material with the parent material and a second coefficient of sliding friction of a material pairing of the second material with the parent material, a first section (14) of the shoulder (3) is composed of the first material and a second section (15) of the shoulder (3) is composed of the second material in order to achieve the desired average coefficient of sliding friction.
  11. The method according to one of claims 6 to 10, characterized in that the first part (5) is produced with a contour that corresponds to the section of the shoulder (3) composed of the first material prior to connecting the first part (5) to the second part (6).
  12. The method according to one of claims 6 to 11, characterized in that the first part (5) essentially has a rotationally symmetrical outer contour, particularly an approximately annular design.
  13. A method for connecting components (7) consisting of a parent material or multiple parent materials that is/are composed of steel, particularly construction steel, and has/have a melting temperature of more than 900°C by means of friction stir welding, characterized in that a friction stir welding tool (1) according to one of claims 1 to 5 is used for connecting these components (7).
  14. The method according to claim 13, characterized in that the components (7) have a tubular design.
  15. The method according to claim 13 or 14, characterized in that the components (7) have a wall thickness (10) of more than 10 mm.

Description

The invention relates to a friction stir welding tool comprising a pin and a shoulder rigidly connected to the pin, for welding components made of a base material formed by a steel with a melting point of more than 900 °C according to the preamble of claim 1 (see e.g. WO 2008/102209 A2 ). The invention further relates to a method for manufacturing a friction stir welding tool with a pin and a shoulder, with which components made of a base material formed by steel having a melting point of more than 900 °C can be joined by friction stir welding, see claim 6. Furthermore, the invention relates to a method for joining components made of a base material formed by a steel, in particular a structural steel, or of several base materials formed by a steel, in particular a structural steel, with a melting temperature of more than 900 °C by friction stir welding, see claim 13. Friction stir welding tools for joining components with a melting point above 900 °C, for joining components made of a single steel or several different steel alloys, are known in the art. Such tools have a pin and a shoulder, usually arranged perpendicular to the pin. When joining two adjacent components, a compressive force is applied to the components to be joined via the shoulder. Simultaneously, due to the rotation of the friction stir welding tool relative to the components around an axis of rotation, the components are heated, so that the components are plasticized and mixed in a joining zone within the area of the friction stir welding tool, thus creating the joint. The pin ensures that the plasticized material is stirred in the joining zone and is therefore subjected to high mechanical and thermal stresses during friction stir welding, while the shoulder of the friction stir welding tool is responsible for a large part of the heat generation. The size of the shoulder is generally determined by the maximum surface pressure under the shoulder and the required compressive force in the axial direction on the components to be joined. It has been shown that materials which have favorable properties for use as pin materials, for example a high melting temperature, lead to excessively high or insufficient heat generation when used in a friction stir welding tool at the shoulder due to excessive friction with the base material of the components to be joined, resulting in an unsatisfactory weld seam. To avoid excessively high or low temperatures during the welding process, it is known in the art to make the shoulder correspondingly larger or smaller. However, this leads to suboptimal pressure in the joining zone, which in turn causes problems with the quality of the weld. Furthermore, it is known from the prior art to form the shoulder and the pin from separate components and to drive the shoulder at a different speed than the pin in order to influence the heat input via the shoulder independently of its size by adjusting the rotational speed of the shoulder. However, it has been shown that while this achieves the desired effect when welding aluminum and other materials with low melting points, when welding base materials with a melting point above 900 °C, such as steel, plasticized material from the joining zone penetrates a gap between the pin and the shoulder, leading to damage to the tool and thus a reduced tool life. This is where the invention comes in. The object is to provide a friction stir welding tool of the type mentioned above, with which a particularly high quality of the weld joint can be achieved even with a given geometry of the friction stir welding tool, while simultaneously achieving a very long tool life. Furthermore, a method for manufacturing a friction stir welding tool of the type mentioned above will be specified, with which such a friction stir welding tool can be manufactured. Finally, a method for joining components of the type mentioned above will be specified, with which a particularly high quality of connection can be achieved in an efficient manner. According to a first aspect of the invention, a friction stir welding tool is defined in claim 1. Within the scope of the invention, it was recognized that the disadvantages of prior art friction stir welding tools can be overcome if the friction stir welding tool is made, at least partially, of a different material in the shoulder region than in a region of the pin. The first material differs from the second material, to which the first material is rigidly bonded, typically in terms of its chemical composition, mechanical and/or thermal properties. This allows for the simple creation of an optimized friction stir welding tool, depending on the desired application. It is advantageous if the first material has a melting temperature of more than 900 °C, preferably more than 2000 °C. Preferably, the second material has a melting point of more than 900 °C, preferably more than 2000 °C, and particularly more than 3000 °C. This allows for a particularly long service life of