Friction Stir Welding Tool and Method for Producing the Same

Abstract

The present invention relates to a friction stir welding tool (1) for welding components (7) made of a base material, in particular steel, having a melting point above 900°C, comprising a pin and a shoulder (3) firmly connected to the pin. To achieve a particularly long service life for tools even with thick-walled components (7), the invention provides a shoulder (3) made at least partially of a first material and a pin made at least partially of a second material. Furthermore, the invention relates to a shoulder (3) made at least partially of a first material and a pin made at least partially of a second material. Furthermore, the invention relates to a method for joining components (7) made of one or more base materials having a melting temperature above 900°C.

Description

Technical Field

[0001] The present invention relates to a friction stir welding tool for welding a component made of a base material having a melting point higher than 900°C, in particular a component made of steel, which comprises a pin and a shoulder firmly connected to the pin.

[0002] Furthermore, the present invention relates to a method for producing a friction stir welding tool having a pin and a shoulder, by which components of a base material having a melting temperature higher than 900°C can be joined by friction stir welding.

[0003] Furthermore, the present invention relates to a method for joining components of one or more base materials having a melting temperature higher than 900°C, in particular for joining components of steel, preferably structural steel, by friction stir welding.

[0004] Friction stir welding tools for joining components having a melting temperature higher than 900°C, in particular for joining components of steel or a plurality of different steel alloys, are known from the prior art. This type of tool includes a pin and a shoulder, which is typically arranged perpendicular to the pin. When two components arranged adjacent to each other are joined, a compressive force is applied to the joined components via the shoulder. At the same time, heating of the components is caused by the friction stir welding tool rotating relative to the components about the axis of rotation, whereby the components are plasticized and mixed in the joining zone in the region of the friction stir welding tool, and thus joining occurs. The pin thereby reliably stirs the plasticized material in the joining zone, where it is exposed to high mechanical and thermal loads during friction stir welding, and the shoulder of the friction stir welding tool bears most of the heat generation. The size of the shoulder is thereby typically obtained from the maximum surface pressure under the shoulder and the required compressive force in the axial direction on the joined components.

[0005] When used in a friction stir welding tool, materials having beneficial properties for use as pin materials, such as a high melting temperature, result in excessive or insufficient heat generation at the shoulder due to excessive friction with the base material of the component to be joined, thereby indicating that optimal welding cannot be achieved.

[0006] To prevent excessive or insufficient temperature during the welding process, it is known from the prior art that the shoulder is accordingly embodied larger or smaller. However, since the compression in the joint zone is not optimal, this results in problems regarding the quality of the welded joint.

[0007] Furthermore, it is known from the prior art that the shoulder and the pin are formed from separate component parts and that, independent of the size of the shoulder, the shoulder is driven at a different speed than the pin in order to influence the heat input through the shoulder using the rotational speed of the shoulder. However, while the desired effect can be achieved in this way when welding aluminum and other materials having a low melting temperature, the plasticized material from the joint zone penetrates the gap between the pin and the shoulder, causing damage to the tool, and where a base material having a melting temperature higher than 900°C, such as steel, is welded, its service life has been shown to be shorter.

[0008] This is addressed by the present invention. Its object is to specify a friction stir welding tool of the type first described. With this tool, even with a given geometry of the friction stir welding tool, a particularly high quality of the welded joint can be achieved, along with a very long service life of the tool.

[0009] Furthermore, a method for producing a friction stir welding tool of the type first described is specified. With this method, a friction stir welding tool of this type can be produced.

[0010] Finally, a method for joining components of the first type noted above is identified. With this method, a particularly high quality of connection can be achieved in an efficient manner.

[0011] According to the present invention, the first object is achieved by a friction stir welding tool of the first type noted above. Here, the shoulder is at least partially composed of a first material, and the pin is at least partially composed of a second material.

[0012] In the context of the present invention, it has been found that when the friction stir welding tool is composed of a material that is at least partially different from the material of the pin region in the shoulder region, the drawbacks of friction stir welding tools from the prior art can be overcome. The first material is typically different from the second material to which the first material is firmly connected in terms of chemical composition, mechanical properties, and / or thermal properties. As a result, an optimized friction stir welding tool can be easily formed according to the desired application.

[0013] It is beneficial when the first material has a melting temperature higher than 900°C, preferably higher than 2000°C.

[0014] Preferably, a second material is provided that has a melting temperature higher than 900°C, preferably higher than 2000°C, particularly higher than 3000°C. Thus, a particularly long service life of the friction stir welding tool can be achieved. Typically, the melting temperature of the second material is higher than that of the first material.

[0015] It has been found effective for the first material and the second material to have different strengths. As a result, in particular, in many cases, a lower strength is sufficient in the shoulder region, but a particularly high strength is typically required, especially in the pin region. Therefore, a tool that particularly well adapts to the required conditions can be realized.

[0016] The combination of the first material and the base material has a first coefficient of kinetic friction, the combination of the second material and the base material has a second coefficient of kinetic friction, and the first coefficient of kinetic friction is different from the second coefficient of kinetic friction, and is particularly beneficial when it is lower than the second coefficient of kinetic friction. Thus, the tool may be embodied to have a lower coefficient of kinetic friction in the shoulder region than in the pin region, for example. Thereby, in a simple manner, a sufficiently high compressive force can be introduced through the shoulder, at the same time with a low surface pressure and without generating excessive heat generation, and in the pin region as well, in particular for a good connection, ensuring that sufficient friction occurs to stir the components plasticized in the joining zone.

[0017] Depending on the desired conditions during the welding process or the required compressive force at the shoulder, the materials may of course be selected such that the first coefficient of kinetic friction is greater than the second coefficient of kinetic friction.

[0018] A shoulder formed entirely of the first material and a pin formed entirely of the second material may be provided, but it is also possible to form the shoulder using only the first material partially and the second material and possibly one or more other materials in part. Similarly, the pin may also be formed in part by only the second material, the first material and possibly other materials. Accordingly, by dividing the shoulder and pin regions into sub-regions composed of different materials having different coefficients of kinetic friction with the base material, it becomes easily possible to achieve the desired coefficient of kinetic friction in both the shoulder region and the pin region. The average coefficient of kinetic friction of the shoulder is typically different from the average coefficient of kinetic friction of the pin.

[0019] This is achievable, for example, when the first component part is ring-shaped and the outer diameter of this first component part corresponds to the outer diameter of the shoulder, while the inner diameter of the first component part is larger than the inner diameter of the shoulder, and the inner diameter of the shoulder is embodied as being able to match the outer diameter of the pin. In the shoulder region, the first material extends there from the outer diameter of the shoulder to the inner diameter of the first component part over the first partial region of the shoulder, and the second material extends from the inner diameter of the first component part to the inner diameter of the shoulder or to the pin in the shoulder region. Further, the pin may be formed by the second material, whereby the second component part forms, partially or completely, the second partial region of the shoulder and the pin.

[0020] Standardly, the average coefficient of kinetic friction of the shoulder is lower than that of the pin. The average coefficient of kinetic friction can thereby be achieved via the corresponding area ratio. When the coefficient of kinetic friction also depends on the relative speed of the friction stir welding tool with respect to the base material, the speed of each area portion during the friction stir welding process may also be taken into account in the selection of the partial region of the shoulder composed of the first or second material.

[0021] Even when a mathematical determination of the average coefficient of kinetic friction achievable over the area formed by the individual materials is preferred, the corresponding friction stir welding tool may of course be formed such that the composition necessary for the desired welding quality in the shoulder region, i.e., the size of the partial region of the shoulder composed of the first material and possibly the second and / or third materials in some cases, is determined by testing.

[0022] Preferably, a first material is provided that is different and has, in particular, a lower chemical affinity for the base material than the second material. Here, chemical affinity means the tendency of each material to bond to the base material. Thus, in the region of the pin, a high chemical affinity can be advantageous in order to achieve good stirring and thus a high strength of the welded joint. In the shoulder region, a lower affinity than in the pin region may be advantageous in order to achieve welding to the smooth surface and to prevent excessive heat input and excessive wear of the friction stir welding tool in the shoulder region. Thus, it can be beneficial if the first material has a lower chemical affinity for the base material than the second material.

[0023] To form the friction stir welding tool, the first material may in principle be connected to the second material in any desired manner, for example by press-fitting, shape fitting, and / or a materially bonded connection method. For example, the friction stir welding tool may essentially consist of the second material and may be coated with the first material in the shoulder region, either partially or completely. In the shoulder region, the first material can also be applied by deposition welding to a larger partial region of the friction stir welding tool, which is composed of the second material, relative to the partial region composed of the second material.

[0024] Similarly, of course, a pin composed of the second material or a partial region of the pin composed of the second material can also be connected to a larger first component part of the friction stir welding tool, which is composed of the first material, in particular by press-fitting, shape fitting, and / or a materially bonded manner, for example by welding or screwing.

[0025] Preferably, the friction stir welding tool comprises a ring composed of the first material, the ring being connected to a second component part composed of the second material by a welding method, in particular a friction stir welding method, the component part forming the pin and the partial region of the shoulder not formed by the ring. The ring composed of the first material may form the outer end of the shoulder or may be arranged in a groove, whereby the ring forms the central or inner first partial region of the shoulder.

[0026] Of course, the first component part of the friction stir welding tool formed from the first material or the second component part of the friction stir welding tool formed from the second material may form at least partially or completely the shaft of the friction stir welding tool.

[0027] In particular, for the purpose of cost optimization, a friction stir welding tool may be provided that includes a third material and, in particular, has a shaft formed of the third material. In this way, the use of cost-effective materials for the shoulder and the pin can be minimized, for example, so that the friction stir welding tool can be produced at a particularly low cost. The individual component parts of the friction stir welding tool, in particular the pin region, the shoulder region, and the shaft region, may be connected to each other in any possible form-fitting, press-fitting, and / or materially bonded manner, for example, by friction welding.

[0028] Of course, depending on the one or more different base materials that make up the component parts being welded in the welded area, the friction stir welding tool may include a wide variety of different materials, and the first material may be formed essentially of any desired material. In particular, in order to achieve beneficial frictional properties at the shoulder, it has been found to be effective, in particular, when the first material contains molybdenum and is embodied as a molybdenum alloy.

[0029] The second material may in principle be formed from any desired material suitable for the corresponding application. Even if high temperatures occur in the joining zone, in order to achieve a particularly long service life, preferably, the second material contains tungsten and, in particular, is provided as a second material formed of tungsten-rhenium.

[0030] Accordingly, in order to achieve advantageous properties, the first material and / or the second material may include a ceramic material, in particular an oxide ceramic material, and / or a non-oxide ceramic material such as a carbide, nitride, or silicide, or may be formed of this type of material.

[0031] A particularly long service life can be achieved if the first material and / or the second material comprises or is formed of a refractory metal, a refractory metal alloy, a nickel alloy, a cobalt alloy, and / or an iron alloy. Refractory metals, i.e., the base metals of groups 4, 5, and 6, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten have extremely high melting temperatures and mechanical properties that are beneficial for use as friction stir welding tools. A further object is achieved by a method of the type initially described, where a first component part made of a first material is firmly connected to a second component part made of a second material, such that at least the shoulder partial region is formed by the first material and at least the pin partial region is formed by the second material.

[0032] Thus, the properties of the friction stir welding tool in the shoulder region can be easily achieved independently of the properties in the pin region.

[0033] To form the friction stir welding tool, the first component part may in principle be connected to the second component part in any desired manner, for example, by press fitting and / or form-fitting connection. However, it is particularly preferred that the first component part is connected to the second component part in a manner such that they are materially bonded. Thereby, a particularly strong connection is achieved.

[0034] The first component part may be connected to the second component part in any desired materially bonded manner, for example, by sintering, 3D printing method, etc., or the second component part may be connected to the first component part, but preferably, a first component part welded to the second component part is provided. Thus, in contrast to the sintering method, coating method, or 3D printing method, it is not absolutely necessary for the outer contour of the first component part to be completely changed or the first component part to be completely melted during the method. Thus, during the method for forming the friction stir welding tool, a first component part and a second component part that essentially retain the outer contour may be provided. For example, the first component part may be embodied as a ring there, which is welded onto the second component part, which includes a pin and, in particular, a part of a shoulder having a groove for the first component part. The welding may be performed, as a result, in a wide variety of techniques known from the prior art, for example, by laser welding, diffusion welding, electron beam welding, etc.

[0035] It has been shown that a particularly strong connection between the first component part and the second component part can be achieved when the first component part is connected to the second component part using a friction welding method.

[0036] Preferably, a first component part connected to the second component part using a pressure welding method is provided. Furthermore, a combination of the friction welding method and the pressure welding method is, of course, possible.

[0037] A desired average coefficient of kinetic friction that acts while the shoulder is in contact with the base material, and in order to achieve the desired average coefficient of kinetic friction according to the desired average coefficient of kinetic friction that is between the first coefficient of kinetic friction of the combination of the first material and the base material and the second coefficient of kinetic friction of the combination of the second material and the base material, it has been found effective that the first partial region of the shoulder is formed of the first material and the second partial region of the shoulder is formed of the second material. In other words, if the shoulder is not entirely formed of the first material, then the size of the partial region of the shoulder formed of the first material is selected according to which average coefficient of kinetic friction is desired in the region of the shoulder. For example, in a material combined with a base material, particularly in a material combined with high-strength structural steel such as used for pipes in a pipeline, if the average coefficient of kinetic friction of the first material is 0.1 and the coefficient of kinetic friction of the second material in the material combined with the same base material is 0.3, then an average coefficient of kinetic friction of the shoulder of 0.2 can be achieved, for example, if the area of the shoulder that contacts the component being welded during the welding process is 50% formed of the first material and 50% formed of the second material. The surface of the shoulder is thus composed of the first partial region and the second partial region, although additional partial regions of other materials are of course possible in principle. Since the speed of the shoulder in the region close to the pin or the axis of rotation is lower than that of the outer edge and the coefficient of kinetic friction can also depend on the relative speed, the region of the shoulder formed of the first material and the region of the shoulder formed of the second material may consequently be in different ratios depending on whether the first material is arranged on the inside or the outside of the shoulder.

[0038] When a first material having a coefficient of kinetic friction lower than that of the second material is preferably used, in order to achieve a particularly large effect, the first material is typically arranged at the outer edge of the shoulder, for example, as an outer ring. Therefore, not only the area ratio of the shoulder formed by the first material or the second material, but rather, at least to some extent, the position of the shoulder formed by the first material or the second material, or the distance from the rotation axis of the friction stir welding tool to the corresponding position, is also related to the quality of the heat input to the weld or the component being welded. Preferably, the friction stir welding tool is embodied to be approximately rotationally symmetric.

[0039] In order to achieve particularly simple production, advantageously, before connecting the first component part to the second component part, a first component part is provided which is formed with a contour corresponding to a partial region of the shoulder formed from the first material. Therefore, the first component part may be embodied, for example, as a ring located in a groove of the second component part to form a corresponding part of the shoulder. In principle, the first component part may of course also be embodied as a polygon or the like in order to achieve a form-fitting connection to the second component part. The second component part may form part of the pin, the whole pin, part of the shaft of the tool, or the whole shaft of the tool.

[0040] Preferably, a first component part is provided which has an essentially rotationally symmetric outer contour and is particularly embodied approximately in a ring shape. This enables particularly simple production of the friction stir welding tool.

[0041] Of course, the friction stir welding tool embodied according to the present invention may be formed by the method according to the present invention.

[0042] The third object is achieved according to the present invention by a method of the type initially described in which a friction stir welding tool embodied according to the present invention is used. As a result, welding of particularly high quality is achieved, along with a long service life of the friction stir welding tool.

[0043] In principle, any desired component can be joined using the friction stir welding tool according to the present invention, but the corresponding friction stir welding tool has been shown to be particularly well-suited for use in a corresponding method in which the components being joined are embodied as tubular. For example, pipes for constructing pipelines can be welded without changing the friction stir welding tool while forming a weld extending along the circumferential direction. This is important for achieving the structure of pipelines installed at a depth of 3000 m below the sea surface, for example, in a particularly efficient manner.

[0044] In particular, the method is preferably used when the component has a wall thickness greater than 10 mm, particularly greater than 20 mm, and in particular when the weld extends across the entire wall thickness. Components typically embodied flatly, preferably tubularly, are placed opposite each other there before being welded along the small surfaces of the components, so that when the weld extends from one surface of the component to the opposite surface of the component, it has a height corresponding to the wall thickness or the height of the small surfaces of the components facing each other.

[0045] Even when having a correspondingly large wall thickness, in order to further achieve a stable friction stir weld joint, in particular, excessive or insufficient amounts of heat can result in a suboptimal friction stir weld joint over at least a partial region of the weld thickness, so it is necessary to input a particularly precisely defined amount of heat. Such precisely defined heat input is easily made possible by the friction stir welding tool according to the present invention. This is because, in particular, the kinetic friction coefficient of the shoulder can be achieved independently of the kinetic friction coefficient and material of the pin.

[0046] Additional features, advantages, and effects of the present invention will follow from the exemplary embodiments described below. The drawings referred to thereby are as follows.

Brief Description of the Drawings

[0047]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0048] FIG. 1 shows a cross-section through a friction stir welding tool 1 embodied according to the present invention. As can be seen, the friction stir welding tool 1, which is embodied essentially rotationally symmetric with respect to the rotation axis 9, includes a shaft 4, a pin 2, and a shoulder 3. The shoulder 3 is oriented approximately perpendicular to the rotation axis 9 and is formed by a first component part 5 of a first material, in this case a molybdenum alloy. The pin 2 and the shaft 4 are formed by a second component part 6 of a second material, in this case tungsten-rhenium. As shown, the first component part 5 is embodied in a ring shape, and the inner diameter 13 of the first component part 5 corresponds to the outer diameter 11 of the pin, which in this case consequently corresponds to the inner diameter 13 of the shoulder. The outer diameter of the ring-shaped first component part 5 corresponds to the outer diameter 12 of the shoulder. Thus, the shoulder 3 is in this case completely formed by the first component part 5 or the first material.

[0049] Due to the use of tungsten-rhenium in the region of pin 2, high temperature resistance is achieved by this type of tool. The use of a molybdenum alloy in the region of shoulder 3 results in a lower coefficient of kinetic friction at shoulder 3 when components 7 of steel, especially structural steel, are welded, thereby achieving lower heat input through shoulder 3 with the same process parameters such as the contact pressure in the axial direction, the rotational speed around the rotational axis 9 of friction stir welding tool 1, and the travel speed, compared to a friction stir welding tool 1 composed only of tungsten-rhenium. The higher coefficient of kinetic friction exhibited by the combination of the materials tungsten-rhenium and structural steel in the region of pin 2 is beneficial for achieving intensive stirring in the joint zone. Thus, components 7 having a large wall thickness 10 may be welded together using friction stir welding in such a way that both a long service life of friction stir welding tool 1 and a high quality of the welded joint are achieved.

[0050] Figure 2 shows a further friction stir welding tool 1 according to the present invention. Shoulder 3 is again here completely formed by a ring-shaped first component part 5 of molybdenum alloy, and the partial regions of pin 2 and shaft 4 are formed by a second component part 6 formed from tungsten-rhenium. However, in contrast to the friction stir welding tool 1 shown in FIG. 1, here shaft 4 is only partially formed by the second component part 6 and partially by a third component part 8 of a third material. The third material may be preferable to tungsten-rhenium, for example, from the perspective of production costs.

[0051] Figure 3 shows a further exemplary embodiment of the friction stir welding tool 1 according to the present invention. In this exemplary embodiment, the first component portion 5 does not extend across the entire shoulder 3. Rather, it forms only the first partial region 14 of the shoulder 3, whereby the second partial region 15 of the shoulder 3 is formed by the second component portion 6 and the pin 2 is also thereby formed. Thus, only the first partial region 14 on the outside of the shoulder 3 is formed by the first component portion 5, which is also embodied in a ring shape in this case and is composed of a molybdenum alloy. In this case, the ring-shaped first component portion 5 thus extends only to the inner diameter 13 approximately in the middle between the inner diameter 13 and the outer diameter 12 of the shoulder, rather than from the outer diameter 12 of the shoulder to the pin 2 or not even to the outer diameter 11 of the pin. Here, the inner diameter 13 of the shoulder also corresponds to the outer diameter 11 of the pin. By modifying the inner diameter 13 of the first component portion 5 or by modifying the first partial region 14 formed of the first material and the second partial region 15 of the shoulder 3 formed of the second material, the desired average coefficient of kinetic friction of the shoulder 3 that occurs when used on a base material such as steel, for example, can thus be arbitrarily adjusted between the first coefficient of kinetic friction of the combination of the first material and the base material and the second coefficient of kinetic friction of the combination of the second material and the base material. In the exemplary embodiment, the first coefficient of kinetic friction of the combination of the molybdenum alloy and steel is lower than the second coefficient of kinetic friction of the combination of tungsten-rhenium and steel. Thereby, in the exemplary embodiment shown in Figure 3, in the region of the shoulder 3, an average coefficient of kinetic friction higher than the coefficient of kinetic friction of the combination of the molybdenum alloy and steel and lower than the coefficient of kinetic friction of the combination of tungsten-rhenium and steel is obtained.

[0052] FIG. 4 shows again in cross-section the friction stir welding tool 1 according to FIG. 1 during welding of the second component 7. As can be seen, the pin 2 extends essentially over the entire wall thickness 10 of the component 7, which in this case is embodied in plate form, for example, made of steel, preferably pipeline steel, and has a melting temperature above 900°C. By using the first material in the region of the shoulder 3, a lower coefficient of kinetic friction is achieved in the region of the shoulder 3 than in the region of the pin 2, whereby a relatively low heat input occurs via the shoulder 3 while an advantageously intensive stirring of the base material of the component 7 is achieved in the region of the pin 2.

[0053] The ring-shaped first component part 5 that at least partially forms the shoulder 3 in the exemplary embodiments shown in FIGS. 1 to 4 is connected to the second component part 6 in the exemplary embodiments by a friction welding process in which the second component part 6 forms the pin 2 and at least a partial region of the shaft 4.

[0054] As a result, a strong and stable connection is provided, which ensures that no gap can form between the first component part 5 and the second component part 6, as is the case, for example, with a multi-part friction stir welding tool 1 in which the shoulder 3 rotates at a lower speed than the pin 2, and thus also ensures that the plasticized material from the welding cannot penetrate such a gap.

[0055] Figures 5 to 7 show cross-sectional views of further exemplary embodiments of the friction stir welding tool 1 according to the present invention. In these exemplary embodiments, the shoulder 3 and the pin 2 of the friction stir welding tool 1, which are essentially composed of a third material, are coated with at least partially different materials in order to obtain different frictional characteristics in the region of the pin 2 and the region of the shoulder 3 when the friction stir welding method is performed. The friction stir welding tool 1 may thus be essentially composed of a third material, and as shown, only the region of the shoulder 3 and the region of the pin 2 may be coated in order to obtain the desired characteristics in these partial regions. In the exemplary embodiment shown in Figure 5, the surface forming the shoulder 3 is thus completely coated with a first material, and the surface forming the pin 2 is completely coated with a second material. Thus, in the exemplary embodiment shown in Figure 5, the first component part 5 is embodied as a coating in the region of the shoulder 3, the second component part 6 is embodied as a coating in the region of the pin 2, the first component part 5 may be composed of, for example, a molybdenum alloy, and the second component part 6 may again be composed of a tungsten alloy here.

[0056] In the exemplary embodiment shown in Figure 6, the first component part 5, which is likewise formed by coating, only partially covers the surface in the region of the shoulder 3. Here, the coating not composed of the first material, or the partial region of the shoulder not formed by the first component part 5, is formed by a coating composed of the second material, or by the second component part 6, and the second component part 6 also forms the surface of the pin 2. Thus, the dynamic friction coefficient of the shoulder 3, which lies between the first dynamic friction coefficient and the second dynamic friction coefficient, can again be realized here.

[0057] Figure 7 shows a further embodiment, where the surface in the region of the shoulder 3 is formed by a first component part 5 made of a first material, and the first component part 5 is embodied as a coating. Here, the surface of the pin 2 is, in this case, partially coated with the first material and partially coated with the second material in order to obtain a property that lies between the properties of the first material and the second material.

[0058] Figure 8 again shows, in a cross-sectional view here, the use of the friction stir welding tool 1 according to FIG. 5 during the method for joining the corresponding component 7.

[0059] As can be seen from FIGS. 5 to 8, the friction stir welding tool 1 may be formed by a third component part 8 which, in order to obtain corresponding properties, is coated with a first material forming the first component part 5 and a second material forming the second component part 6 at the end faces in the region of the essentially third material, or the shoulder 3 and the pin 2. In contrast to the exemplary embodiments shown in FIGS. 1 to 4, in the exemplary embodiments shown in FIGS. 5 to 8, the contours of the first component part 5 and the second component part 6 are, there, i.e., by coating the surface of the third component part 8, first formed during the production of the friction stir welding tool 1.

[0060] The corresponding friction stir welding tool 1 may, in principle, be used for a wide variety of purposes. Preferably, the corresponding tool is a structural steel, in particular a high-strength and ultra-high-strength steel, and, for example, a thick-walled pipe made of structural steel that may have a wall thickness 10 greater than 10 mm along a circumferentially extending weld, and is used, for example, to weld together pipes available for pipelines at great depths. Thus, even a thick-walled pipe of steel can be welded using a single friction stir welding tool 1 without changing the tool, whereby the corresponding pipeline can be produced in a particularly cost-effective manner. Other possible items

[0061] 1. A friction stir welding tool (1) for welding a component (7) made of a base material, particularly steel, having a melting point exceeding 900 °C, comprising a pin (2) and a shoulder (3) firmly connected to the pin (2), wherein the friction stir welding tool (1) is formed, in particular, by the method according to one of items 12 to 19, the shoulder (3) is at least partially made of a first material, and the pin (2) is at least partially made of a second material.

[0062] 2. The friction stir welding tool (1) according to item 1, characterized in that the first material has a melting temperature higher than 900 °C, preferably higher than 2000 °C.

[0063] 3. The friction stir welding tool (1) according to item 1 or 2, characterized in that the second material has a melting temperature higher than 900 °C, preferably higher than 2000 °C, particularly higher than 3000 °C.

[0064] 4. The friction stir welding tool (1) according to one of items 1 to 3, characterized in that the first material and the second material have different strengths.

[0065] 5. The combination of the first material and the base material has a first coefficient of kinetic friction, and the combination of the second material and the base material has a second coefficient of kinetic friction, the first coefficient of kinetic friction being different from the second coefficient of kinetic friction, in particular lower than the second coefficient of kinetic friction. The friction stir welding tool (1) according to one of items 1 to 4.

[0066] 6. The friction stir welding tool (1) according to one of items 1 to 5, characterized in that the first material has a lower chemical affinity for the base material than the second material.

[0067] 7. The friction stir welding tool (1) according to one of items 1 to 6, characterized in that the friction stir welding tool (1) includes a third material, in particular having a shaft (4) formed by the third material.

[0068] 8. The friction stir welding tool (1) according to one of items 1 to 7, wherein the first material contains molybdenum and is embodied as a molybdenum alloy in particular.

[0069] 9. The friction stir welding tool (1) according to one of items 1 to 8, wherein the second material contains tungsten and is formed by tungsten-rhenium in particular.

[0070] 10. The friction stir welding tool (1) according to one of items 1 to 9, wherein the first material and / or the second material contains a ceramic material, in particular an oxide ceramic material and / or a non-oxide ceramic material such as a carbide, nitride, or silicide, or is formed by this type of material.

[0071] 11. The friction stir welding tool (1) according to one of items 1 to 10, wherein 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 formed by this type of material.

[0072] 12. A method for producing a friction stir welding tool (1) having a pin (2) and a shoulder (3), by which a component (7) of a base material having a melting temperature higher than 900 °C, in particular formed of steel, preferably structural steel, can be joined by friction stir welding, in particular a method for producing the friction stir welding tool (1) according to one of items 1 to 11, wherein a first component part (5) composed of the first material is firmly connected to a second component part (6) composed of the second material, whereby at least a partial region of the shoulder (3) is formed by the first material and at least a partial region of the pin (2) is formed by the second material.

[0073] 13. The method according to item 12, wherein the first component part (5) is connected to the second component part (6) in a materially bonded manner.

[0074] 14. The method according to item 12 or 13, wherein the first component part (5) is welded to the second component part (6).

[0075] 15. The method according to any one of items 12 to 14, wherein the first component part (5) is connected to the second component part (6) using a friction welding method.

[0076] 16. The method according to any one of items 12 to 15, wherein the first component part (5) is connected to the second component part (6) using a pressure welding method.

[0077] 17. A desired average dynamic friction coefficient acting while the shoulder (3) is in contact with the base material, and in order to achieve the desired average dynamic friction coefficient according to the desired average dynamic friction coefficient which is between the first dynamic friction coefficient of the combination of the first material and the base material and the second dynamic friction coefficient of the combination of the second material and the base material, the first partial region (14) of the shoulder (3) is formed of the first material, and the second partial region (15) of the shoulder (3) is formed of the second material. The method according to any one of items 12 to 16.

[0078] 18. Before connecting the first component part (5) to the second component part (6), the first component part (5) is formed with a contour corresponding to the partial region of the shoulder (3) formed of the first material. The method according to any one of items 12 to 17.

[0079] 19. The method according to any one of items 12 to 18, wherein the first component part (5) has an essentially rotationally symmetric outer contour, and in particular, is embodied approximately in a ring shape.

[0080] A method for joining components (7) of one or more base materials having a melting temperature higher than 20,900 °C, in particular components (7) of steel, preferably structural steel, by friction stir welding, characterized in that the friction stir welding tool (1) according to one of claims 1 to 11 is used.

[0081] 21. The method according to claim 20, characterized in that the component (7) is embodied in tubular form.

[0082] 22. The method according to claim 20 or 21, characterized in that the component (7) has a wall thickness (10) greater than 10 mm.

Claims

1. A friction stir welding tool for welding a component made of a base material, the component comprising a pin and a shoulder firmly connected to the pin, wherein the base material is formed of steel and has a melting point above 900°C, the shoulder is at least partially composed of a first material, the pin is at least partially composed of a second material, the combination of the first material and the base material has a first coefficient of kinetic friction, the combination of the second material and the base material has a second coefficient of kinetic friction, and the first coefficient of kinetic friction is lower than the second coefficient of kinetic friction.

2. The friction stir welding tool according to claim 1, wherein the melting temperature of the second material is higher than the melting temperature of the first material.

3. The shoulder or the pin partially coated by a first component portion or a second component portion has a coefficient of kinetic friction between the first coefficient of kinetic friction and the second coefficient of kinetic friction by providing the first component portion of the first material and the second component portion of the second material connected to the first component portion on the shoulder or the pin. The friction stir welding tool according to claim 1 or 2.

4. The friction stir welding tool according to any one of claims 1 to 3, wherein the first material has a melting temperature higher than 900°C, preferably higher than 2000°C.

5. The friction stir welding tool according to any one of claims 1 to 4, wherein the second material has a melting temperature higher than 900°C, preferably higher than 2000°C, particularly higher than 3000°C.

6. The friction stir welding tool according to any one of claims 1 to 5, wherein the first material and the second material have different strengths.

7. The friction stir welding tool according to any one of claims 1 to 6, wherein the first material has a lower chemical affinity for the base material than the second material.

8. The friction stir welding tool according to any one of claims 1 to 7, wherein the friction stir welding tool includes a third material, and in particular, has a shaft formed of the third material.

9. The friction stir welding tool according to any one of claims 1 to 8, wherein the first material contains molybdenum, and in particular, is embodied as a molybdenum alloy.

10. The friction stir welding tool according to any one of claims 1 to 9, wherein the second material contains tungsten, and in particular, is formed of tungsten-rhenium.

11. The friction stir welding tool according to any one of claims 1 to 10, wherein the first material and / or the second material contains a ceramic material, and in particular, contains an oxide ceramic material and / or a non-oxide ceramic material such as a carbide, nitride, or silicide, or is formed of this type of material.

12. The friction stir welding tool according to any one of claims 1 to 11, wherein 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 formed of this type of material.

13. A method for producing a friction stir welding tool having a pin and a shoulder, by which a component of a base material having a melting temperature higher than 900°C, formed of steel, in particular structural steel, can be joined by friction stir welding. In particular, it is a method for producing a friction stir welding tool according to any one of claims 1 to 12, wherein a first component part made of a first material is firmly connected to a second component part made of a second material, whereby at least a partial region of the shoulder is formed of the first material, at least a partial region of the pin is formed of the second material, the combination of the first material and the base material has a first dynamic friction coefficient, the combination of the second material and the base material has a second dynamic friction coefficient, and the first dynamic friction coefficient is lower than the second dynamic friction coefficient.

14. The method according to claim 13, wherein the first component part is connected to the second component part in a materially bonded manner.

15. The method according to claim 13 or 14, wherein the first component part is welded to the second component part.

16. The method according to any one of claims 13 to 15, wherein the first component part is connected to the second component part using a friction welding method.

17. The method according to any one of claims 13 to 16, wherein the first component part is connected to the second component part using a pressure welding method.

18. A desired average coefficient of kinetic friction that acts while the shoulder is in contact with the base material, and in order to achieve the desired average coefficient of kinetic friction according to the desired average coefficient of kinetic friction that is between a first coefficient of kinetic friction of the combination of the first material and the base material and a second coefficient of kinetic friction of the combination of the second material and the base material, a first partial region of the shoulder is formed of the first material, and a second partial region of the shoulder is formed of the second material. The method according to any one of claims 13 to 17.

19. Before connecting the first component part to the second component part, the first component part is formed with a contour corresponding to the partial region of the shoulder formed from the first material. The method according to any one of claims 13 to 18.

20. The first component part has an essentially rotationally symmetric outer contour, and in particular is embodied approximately in a ring shape. The method according to any one of claims 13 to 19.

21. A method for joining a component having a melting temperature higher than 900 °C of one base material formed of steel, in particular structural steel, or a plurality of base materials formed of steel, in particular structural steel, by friction stir welding, wherein the friction stir welding tool according to any one of claims 1 to 12 is used. Method.

22. The component is embodied in a tubular shape. The method according to claim 21.

23. The component has a wall thickness greater than 10 mm. The method according to claim 21 or 22.

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