FRICTION STIR WELDING TOOL AND METHOD FOR PRODUCING SAME

Abstract

A friction stir welding tool, which includes a pin and a shoulder rigidly connected to the pin, for welding components composed of a parent material having a melting point of more than 900° C., in particular steel. To achieve a particularly long service life of the tool even with thick-walled components, it is provided that the shoulder is at least partially composed of a first material and the pin is at least partially composed of a second material. Furthermore, the shoulder is at least partially composed of a first: material and the pin is at least partially composed of a second material. In addition, a method for joining components of one or more parent materials having a melting temperature of more than 900° C. is provided.

Claims

1. A friction stir welding tool, which comprises a pin and a shoulder rigidly connected to the pin, for welding components composed of a parent material formed by a steel and having a melting point of over 900° C., wherein the shoulder is at least partially composed of a first material and the pin is at least partially composed of a second material, wherein a material pairing of the first material with the parent material has a first coefficient of kinetic friction and a material pairing of the second material with the parent material has a second coefficient of kinetic friction, wherein 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 first material has a melting temperature of more than 900° C., preferably more than 2000° C.

3. The friction stir welding tool according to claim 1, wherein the second material has a melting temperature of more than 900° C., preferably more than 2000 ° C., in particular more than 3000 ° C.

4. The friction stir welding tool according to claim 1, wherein the first material and the second material have different strengths.

5. (canceled)

6. The friction stir welding tool according to claim 1, wherein the first material has a lower chemical affinity to the parent material than the second material.

7. The friction stir welding tool according to claim 1, wherein the friction stir welding tool has a shaft which comprises a third material, in particular is formed by a third material.

8. The friction stir welding tool according to claim 1. wherein the first material contains molybdenum, in particular is embodied as a molybdenum alloy.

9. The friction stir welding tool according to claim 1, wherein the second material contains tungsten, in particular is formed by tungsten-rhenium.

10. The friction stir welding tool according to claim 1, wherein the first material and/or the second material comprises a ceramic material, in particular an oxide ceramic material, and/or a non-oxide ceramic material such as carbides, nitrides, or silicides, or is formed by a material of this type.

11. The friction stir welding, tool according to claim 1, wherein the first material and/or the second material comprises a refractory metal, a refractory metal alloy, a nickel alloy, a cobalt alloy, and/or an iron alloy, or is formed by a material of this type.

12. A method for producing a friction stir welding tool having a pin and a shoulder, with which method components of a parent material formed by a steel, in particular a structural steel, which parent material has a melting temperature of more than 900° C., can be joined by friction stir welding, in particular for producing a friction stir welding tool according to claim 1, wherein a first component part, which is composed of a first material, is rigidly connected to a second component part, which is composed of a second material, so that at least a partial region of the shoulder is formed by the first material and at least a partial region of the pin is formed by the second material, wherein a material pairing of the first material with the parent material has a first coefficient of kinetic friction and a material pairing of the second material with the parent material has a second coefficient of kinetic friction, wherein the first coefficient of kinetic friction is lower than the second coefficient of kinetic friction.

13. The method according to claim 12, wherein the first component part is connected to the second component part in a materially bonded manner.

14. The method according to claim 12, wherein the first component part is welded to the second component part.

5. The method according to claim 12, wherein the first component part is connected to the second component part using a friction welding method.

16. The method according to claim 12, wherein the first component part is connected to the second component part using a pressure welding method.

17. The method according to claim 12, wherein, depending on a desired mean coefficient of kinetic friction that acts during contact of the shoulder with the parent material and lies between a first coefficient of kinetic friction, which a material pairing of the first material with the parent material has, and a second coefficient of kinetic friction, which a material pairing of the second material with the parent material has, a first partial region of the shoulder is formed by the first material and a second partial region of the shoulder is formed by the second material, in order to achieve the desired mean coefficient of kinetic friction.

18. The method according to claim 12, wherein, before a connection of the first component part to the second component part, the first component part is formed with a contour which corresponds to the partial region of the shoulder that is formed from the first material.

19. The method according to claim 12, wherein the first component part has an essentially rotationally symmetrical outer contour, in particular is embodied to be roughly ring-shaped.

20. A method for joining components of one parent material formed by a steel, in particular a structural steel, or multiple parent materials formed by a steel, in particular a structural steel, and having a melting temperature of more than 900° C. by friction stir welding, wherein a friction stir welding tool according to claim 1 is used.

21. The method according to claim 20, wherein the components are embodied to be tubular.

22. The method according to claim 20, wherein the components have a wall thickness of more than 10 mm.

Description

[0047] Additional features, advantages, and effects of the invention follow from the exemplary embodiments described below. In the drawings which are thereby referenced:

[0048] FIGS. 1 through 3 show different friction stir welding tools embodied according to the invention;

[0049] FIG. 4 shows a friction stir welding tool according to the invention during the welding of two components;

[0050] FIGS. 5 through 7 show further friction stir welding tools;

[0051] FIG. 8 shows a further friction stir welding tool during the joining of two components.

[0052] FIG. 1 shows a section through a friction stir welding tool 1 embodied according to the invention. As can be seen, the friction stir welding tool 1, which is embodied to be essentially rotationally symmetrical to a rotation axis 9, comprises a shaft 4, a pin 2, and a shoulder 3, wherein the shoulder 3 is oriented roughly perpendicularly to the rotation axis 9 and is formed by a first component part 5 of a first material, in this ease a molybdenum alloy, and 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 illustrated, the first component part 5 is embodied to be ring-shaped, wherein an inner diameter 13 of the first component part 5 corresponds to a pin outer diameter 11, which in this case corresponds, in turn, to the shoulder inner diameter 13. An outer diameter of the ring-shaped first component part 5 corresponds to a shoulder outer diameter 12. The shoulder 3 is thus in this case entirely formed by the first component part 5 or the first material.

[0053] Due to the use of tungsten-rhenium in the region of the pin 2, a high temperature resistance is achieved with a tool of this type. Through the use of the molybdenum alloy in the region of the shoulder 3, a lower coefficient of kinetic friction is achieved at the shoulder 3 than in the region of the pin 2 when components 7 of a steel, in particular of structural steel, are being welded, so that a lower heat input via the shoulder 3 is achieved compared to a friction stir welding tool 1 composed solely of tungsten-rhenium, with identical process parameters such as contact pressure in an axial direction, rotational speed of the friction stir welding tool 1 about the rotation axis 9, and forward speed. In the region of the pin 2, a higher coefficient of kinetic friction, which the material pairing of tungsten-rhenium with structural steel exhibits, is beneficial for achieving an intensive stirring in a joining zone. Thus, using friction stir welding, components 7 with a large wall thickness 10 can also be welded together in such a manner that both a long service life of the friction stir welding tool 1 and a high quality of the welded joint are achieved.

[0054] FIG. 2 shows a further friction stir welding tool 1 according to the invention. The shoulder 3 is once again entirely formed by a ring-shaped first component part 5 of a molybdenum alloy, whereas the pin 2 and a partial region of the shaft 4 are formed by a second component part 6 formed from tungsten-rhenium. In contrast to the friction stir welding tool 1 illustrated in FIG. 1, however, the shaft 4 here is formed only partially by the second component part 6 and is partially formed by a third component part 8 of a third material, which third material can be more favorable than tungsten-rhenium in terms of production costs, for example.

[0055] FIG. 3 shows a further exemplary embodiment of a friction stir welding tool 1 according to the invention. In this exemplary embodiment, the first component part 5 does not extend across the entire shoulder 3, but rather only forms a first partial region 14 of the shoulder 3, so that a second partial region 15 of the shoulder 3 is formed by the second component part 6, which the pin 2 is also formed by. Thus, only an outer first partial region 14 of the shoulder 3 is formed by the first component part 5, which in this case is also embodied to be ring-shaped and is composed of a molybdenum alloy. In this case, the ring-shaped first component part 5 therefore extends from the shoulder outer diameter 12 not to the pin 2, or not to the pin outer diameter 11, but rather only to an inner diameter 13 that lies roughly in the middle between a shoulder inner diameter 13 and the shoulder outer diameter 12. Here, the shoulder inner diameter 13 also corresponds to the pin outer diameter 11. By modifying the inner diameter 13 of the first component part 5, or by modifying the first partial region 14 formed by the first material and the second partial region 15 of the shoulder 3 formed by the second material, a desired mean coefficient of kinetic friction of the shoulder 3, which occurs in use on a parent material such as steel, for example, can thus be adjusted at will between a first coefficient of kinetic friction of a material pairing of the first material with the parent material and a second coefficient of kinetic friction of a material pairing of the second material with the parent material. In the exemplary embodiment, the first coefficient of kinetic friction of the material pairing of molybdenum alloy with steel is lower than the second coefficient of kinetic friction of the material pairing of tungsten-rhenium with steel, so that in the exemplary embodiment illustrated in FIG. 3, a mean coefficient of kinetic friction is obtained in th.e region of the shoulder 3 that is higher than the coefficient of kinetic friction of the material pairing of molybdenum alloy with steel and lower than the coefficient of kinetic friction of the material pairing of tungsten-rhenium with steel.

[0056] FIG. 4 shows a friction stir welding tool 1 according to FIG. 1 during the welding of second components 7, once again in a sectional illustration. As can be seen, the pin 2 extends essentially across an entire wall thickness 10 of the components 7, in this case embodied to be plate-shaped for example, which are composed of a steel, preferably a pipeline steel, and have a melting temperature of more than 90° C. Through the use of 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, so that an advantageously intensive stirring of the parent materials of the components 7 is achieved in the region of the pin 2, whereas a comparatively low heat input occurs via the shoulder 3.

[0057] The ring-shaped first component part 5, from which the shoulder 3 in the exemplary embodiments illustrated in FIG. 1 through FIG. 4 is at least partially formed, is connected to the second component part 6 in the exemplary embodiments by means of a friction welding process, which second component part 6 forms the pin 2 and at least a partial region of the shaft 4.

[0058] This results in a rigid, stable connection, whereby it is also ensured that, between the first component part 5 and the second component part 6, there is no gap and therefore no plasticized material from the weld can penetrate into such a gap, as would be the case with a multi-part friction stir welding tool 1 in which, for example, the shoulder 3 rotates at a lower speed than the pin 2.

[0059] FIGS. 5 through 7 show further exemplary embodiments of a friction stir welding tool 1 according to the invention in sectional illustrations. In these exemplary embodiments, the shoulder 3 and the pin 2 of a friction stir welding tool 1 composed essentially of a third material are at least partially coated with different materials in order to obtain different frictional properties in the region of the pin 2 and in the region of the shoulder 3 when a friction stir welding method is carried out. The friction stir welding tool 1 can thereby essentially be composed of a third material and, as illustrated, be coated only in the region. of the shoulder 3 and in the region of the pin 2, in order to obtain the desired properties in these partial regions. In the exemplary embodiment illustrated in FIG. 5, a surface forming the shoulder 3 is thereby entirely coated with a first material and a surface forming the pin 2 entirely coated with a second material. Thus, in the exemplary embodiment illustrated in FIG. 5, the first component part 5 is embodied as a coating in the region of the shoulder 3 and the second component part 6 as a coating in the region of the pin 2, wherein the first component part 5 can, for example, also be composed of a molybdenum alloy and the second component part 6 once again of a tungsten alloy.

[0060] In the exemplary embodiment illustrated in FIG. 6, the first component part 5, which is likewise formed by a coating, only partially covers a surface in the region of the shoulder 3. Here, a coating not composed of the first material, or a partial region of the shoulder 3 not formed by the first component part 5, is formed by a coating formed from the second material, or by a second component part 6, which second component part 6 also forms a surface of the pin 2. In this manner, a coefficient of kinetic friction of the shoulder 3 that lies between the first coefficient of kinetic friction and the second coefficient of kinetic friction can once again be achieved.

[0061] FIG. 7 shows a further embodiment in which a surface in the region of the shoulder 3 is formed by a first component part 5 composed of a first material, which first component part 5 is embodied as a coating. Here, a surface of the pin 2 is partially coated with the first material and partially with the second material, in order to obtain properties in this case which lie between the properties of the first material and the properties of the second material.

[0062] FIG. 8 shows the use of a friction stir welding tool 1 according to FIG. 5 during a method for joining corresponding components 7, once again in a sectional illustration.

[0063] As can be seen in FIGS. 5 through 8, the friction stir welding tool 1 can thus also be formed essentially by a third material or a third component part 8 which at the end side in the region of the shoulder 3 and of the pill 2 is coated with a first material that forms a first component part 5 and a second material that forms a second component part 6, in order to obtain corresponding properties. In contrast to the exemplary embodiments illustrated in Figs. I through 4, in the exemplary embodiments illustrated in FIGS. 5 through 8, the contours of the first component part 5 and of the second component part 6 are thus first formed during the production of the friction stir welding tool 1, namely by coating a surface of the third component part 8.

[0064] A corresponding friction stir welding tool 1 can, in principle, be used for widely different purposes. Preferably, a corresponding tool is used to weld together structural steel, in particular high-strength and super. high-strength steels, as well as thick-walled pipes that, for example, can be composed of a structural steel and have a wall thickness 10 of more than 10 mm, along a weld that runs in a circumferential direction, which pipes can be used for a pipeline at a great depth. for example. Even thick-walled pipes of steel can thus be welded without changing tools using a single friction stir welding tool 1, whereby a corresponding pipeline can be produced in a particularly cost-efficient manner.