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EP-4741094-A1 - FRICTION STIR WELDING TOOL

EP4741094A1EP 4741094 A1EP4741094 A1EP 4741094A1EP-4741094-A1

Abstract

The present invention relates to the field of friction stir welding technology, in particular monolithic friction stir welding tools for friction stir welding of materials, especially aluminum, steel or copper, with integrated cooling channels. The invention further relates to a friction stir welding tool holder system, a friction stir welding system and a method for manufacturing the tool holders.

Inventors

  • OYANEDEL FUENTES, Javier A.

Assignees

  • Hufschmied Zerspanungssysteme GmbH

Dates

Publication Date
20260513
Application Date
20251104

Claims (15)

  1. A monolithic friction stir welding tool for friction stir welding of materials, consisting of a shaped body (1.0), wherein the shaped body (1.0) comprises: - a rotation axis (2.0), - a shoulder (1.1) that is arranged orthogonally to the axis of rotation (2.0), - a shoulder surface (1.2) which is arranged between the shoulder (1.1) and the tool shank (1.4), - a stirring stick (1.3) which is terminally arranged on the axis of rotation (2.0) at the shoulder (1.1), - a tool shank (1.4) with a centrally located axis of rotation (2.0), characterized by the fact that the shaped body (1.1) is designed as a single piece and consists of a material selected from the list consisting of hard metal, cermet or ceramic, wherein the molded body has an integrated cooling channel (3.0), wherein the cooling channel is connected to an outlet opening (4.0), the outlet opening is located at the periphery of the molded body.
  2. Friction stir welding tool according to claim 1, wherein the integrated cooling channel (3.0) is designed linearly.
  3. Friction stir welding tool according to one of claims 1 or 2, wherein the integrated cooling channel (3.0) is designed in a twisted configuration.
  4. Friction stir welding tool according to one of claims 1 to 3, wherein the outlet opening (4.0) is connected to the integrated cooling channel (3.0) via an outlet channel (5.0).
  5. Friction stir welding tool according to one of claims 1 to 4, wherein the exit channel (5.0) has an angle (7.0) of 10° to 90° relative to the axis of rotation (2.0).
  6. Friction stir welding tool according to one of claims 1 to 5, wherein the integrated cooling channel (3.0) has two to ten different outlet openings (4.0).
  7. Friction stir welding tool according to any one of claims 1 to 6, wherein the cooling channel is configured to transport a coolant, wherein the coolant is selected from the list consisting of water, water-based emulsions, pure oils, air, nitrogen, or argon.
  8. Friction stir welding tool according to one of claims 1 to 7, wherein the material has a hardness of 1000 to 2500 HV.
  9. Friction stir welding tool according to any one of claims 1 to 8, wherein the material is a cemented carbide, the cemented carbide consisting of a composition comprising a mass fraction of 60 to 97% α-phase, preferably tungsten carbide (WC), 3 to 20% β-phase, preferably selected from the list consisting of Co, Ni or a mixture thereof, and 0 to 35% γ-phase, preferably selected from the list consisting of TiC, (Ta,Nb)C, ZrC, VC or a mixture thereof.
  10. Friction stir welding tool according to any one of claims 1 to 9, wherein the ceramic is selected from the list consisting of aluminum oxide (CA), mixed ceramic (CM), whisker-reinforced ceramic (CR), silicon carbide (SC), SiAlON or silicon nitride cutting ceramic (CN).
  11. Friction stir welding tool according to any one of claims 1 to 10, wherein at least the material of the shoulder and/or the stir pin has a coating, wherein the coating is a PVD or CVD coating, wherein the coating preferably consists of a coating material selected from the list consisting of Chemical Vapor Deposition diamond (CVD diamond), titanium aluminum nitride (TiAlN), titanium nitride (TiN), aluminum titanium nitride (AlTiN), titanium carbide nitride (TiCN), zinc nitride (ZnN), zirconium nitride (ZrN), DLC (diamond-like carbon), PCD (polycrystalline diamond), or PCBN (polycrystalline cubic boron nitride).
  12. Friction stir welding tool according to one of claims 1 to 11, wherein the tool shank has a retaining means (1.5) for the tool holder, wherein the retaining means (1.5) is preferably selected from the list consisting of thread, Weldon holder, surface chuck, groove, notch, recess or rail.
  13. Method for manufacturing the friction stir welding tool according to one of claims 1 to 12, comprising the steps a) Provision of the starting materials in powder form with defined properties, in particular particle sizes, b) Homogenization of the starting materials, c) Cold forming of the molded body and subsequent sintering, or d) Additive manufacturing of the molded part, e) Post-processing of the molded body, in particular grinding.
  14. Friction stir welding tool holder system comprising a friction stir welding tool according to claim 12, arranged operatively in a tool holder (6.0) with integrated coolant supply (6.1) by means of the holding means (1.5).
  15. Friction stir welding system comprising a friction stir welding tool according to one of claims 1 to 12 or a friction stir welding tool holder system according to claim 14, operatively arranged on a tool spindle, wherein the tool spindle has a coolant supply.

Description

TECHNICAL AREA The present invention relates to a friction stir welding tool specifically designed for machining high-melting-point metals under high mechanical and thermal stresses. Preferably, the invention relates to a monolithic FSW tool made of carbide, cermet, or ceramic, particularly with integrated coolant supply to optimize welding process efficiency. This disclosure includes an FSW tool with internal cooling channels that serve to dissipate the heat generated during the welding process and significantly increase the tool's service life. Furthermore, the invention includes a specific manufacturing process that encompasses the production of the tool and the cooling channels to precisely control the process heat while simultaneously ensuring the tool's mechanical stability. This tool is therefore central to the efficient, productive, and durable execution of FSW processes in various industries, particularly in the aerospace and automotive sectors. STATE OF THE ART Friction stir welding (FSW) has established itself as an efficient welding method for difficult-to-weld materials, particularly aluminum alloys and refractory metals. Developed in 1991 by the Welding Institute (TWI) in the UK, the process solved numerous problems associated with traditional welding methods, such as weld porosity, cracking, and distortion. While FSW was initially used primarily for aluminum alloys, it is increasingly being applied to more challenging materials like copper alloys and steel. A key problem in flux-free welding (FSW) of refractory metals is the excessive heating and rapid wear of the welding tool, particularly at the tool shoulder. Various patents and research projects have addressed tool cooling during the welding process to extend its service life. Many of these approaches, such as those described in the patent specification, CN105234554A The described methods involve the use of cooling channels within the tool through which coolant circulates. However, these documents do not define specific materials for the tool itself, which limits the applicability of these solutions to demanding welding processes. Most known technical solutions aim at external cooling of the workpieces. The US patent US6516992B1 This patent describes a method for simultaneous cooling during the Friction Stir Welding (FSW) process, in which coolant is passed through the tool to reduce surface roughness and enable higher welding speeds. However, the patent does not define specific materials for the welding tool, which limits its applicability to more demanding welding processes, particularly with refractory metals. Furthermore, the method focuses primarily on cooling by external coolant, without implementing comprehensive internal cooling of the tool. The US patent US7845544B2 This describes a FSW (Fused Welding) process in which coolant is sprayed onto the tool surface from the outside. While this method cools the tool surface, it does not address the internal heat generation of the tool, making cooling inefficient, especially during intensive welding processes. Again, information on specific tool materials is lacking, limiting its application to high-melting-point metals. The US patent US6772935B2 This describes a process in which the weld is cooled behind the welding tool to reduce the temperature of the affected area. This method focuses on the weld itself and not on cooling the tool, meaning the tool remains exposed to thermal stress. Tool materials are not specified, and there is no integrated cooling within the tool, which negatively impacts tool life. The patent application WO2023119329A1 This describes a forced-air welding (FSW) tool with a forced-air cooling method, where either an air blower, a water sprinkler, or a combination of both is used to cool the workpiece. The fan or sprinkler system is attached to the tool shank to regulate the temperature during the welding process, thereby improving the mechanical and metallurgical properties of the weld. This method focuses on targeted cooling of the workpiece, not the tool, and requires external cooling elements. The disadvantages of external cooling in the FSW process are that only the workpiece surface is cooled, leading to undesirable thermal gradients. These gradients can be particularly problematic with materials such as ceramics or hard metals. This can lead to significant overheating in the workpiece core. Uneven cooling impairs process stability, as the inner part of the workpiece is not cooled sufficiently. This can result in distortion, cracking, or reduced weld quality, making the overall process inefficient. Only a few approaches attempting to achieve more direct cooling can be found in the literature. The Chinese patent specification CN105234554A This describes a friction stir welding head structure with integrated internal cooling, in which cooling channels run spirally or in a U-shape inside the tool. The only suggested method is the use of circulating coolant to pr