Method for friction stir welding and friction stir welded workpiece

Patent metadata

Field	Value
Publication number	US-10835989-B2
Application number	US-201615748560-A
Country	US
Kind code	B2
Filing date	Jul 29, 2016
Priority date	Jul 29, 2015
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

In a method of friction stir welding two pieces of material of greatly differing melting temperatures, provision is made that the first piece of material is overlapped by the second piece of material. The rotating pin of the friction stir welding tool provides for a butt joint welding and an overlap welding at the same time in that the pin is moved along the face side and contacts it either not at all or at most to a minimum extent. The same also applies to the planar side of the first piece of material, which is overlapped by the less stable piece of material.

First claim

The invention claimed is:

1. A method of friction stir welding a first piece of material to at least one second piece of material, wherein
the first piece of material has a face side and an adjacent planar side which forms a top side or a bottom side of the first piece of material, and has a melting temperature that is higher by at least 250° C. than that of the at least one second piece of material, wherein
a single second piece of material is provided having a thickness greater than the thickness of the first piece of material or a plurality of second pieces of material are provided which are stapled onto each other so that the staple has a higher thickness than the first piece of material, characterized by the following steps:
(a) the first and second pieces of material are arranged next to each other so that the face sides of the first piece of material and the side face of the single second piece of material or one of the second pieces of material are arranged next to each other, the first piece of material is overlapped by a sidewardly protruding portion of the single second piece of material or by one of the second pieces of material such that the single second piece of material or the staple of the second pieces of material is adjacent to the planar side and laterally of the face side; and
(b) the first piece of material is butt welded and overlap welded to the second piece of material or one or more of the second pieces of material by a friction stir welding tool having a rotating pin, by the pin being moved along the face side and the tool being moved along the planar side in the adjacent second piece of material, wherein the pin has a step which faces the planar side and provides for the overlap welding simultaneously with the butt joint welding generated by the pin tip projecting from the step.

2. The method according to claim 1 , wherein at least 90% of the pin is moved in the second piece of material.

3. The method according to claim 1 , wherein during the friction stir welding, the different materials of the pieces of material are not blended, or wherein a diffusion layer of a thickness of 0.5 mm maximum is produced upon scratching.

4. The method according to claim 1 , wherein a pin is used which has a pin tip that extends up to the step and a section extending from the step up to a shoulder and having an axial length, the axial length and the thickness of the second piece of material and the thickness of the first piece of material being matched to each other such that the axial length is equal to or greater than the difference of the thickness of the second piece of material minus the thickness of the first piece of material and a protruding weld seam is produced.

5. The method according to claim 1 , wherein the pin has a shoulder and wherein the friction stir welding tool is advanced toward the planar side only so far that softened material of the at least one second piece of material is permanently present between the shoulder and the planar side of the first material during butt welding.

6. The method according to claim 1 , wherein the pin has a pin tip having an axial length as measured from the pin end up to a step of the pin, the axial length substantially corresponding to the thickness of the first piece of material at the face side thereof.

7. The method according to claim 1 , wherein the overlap welding and the butt joint welding are effected in succession by one or more pins, with the pin responsible for the overlap welding being moved on the face side along the planar side.

8. The method according to claim 1 , wherein the first piece of material and the at least one second piece of material are in the form of flat plates at least in the welding area.

9. The method according to claim 1 , wherein a second piece of material is formed so as to be flat at least in the welding area and, in relation to the first piece of material, extends obliquely to the face side along a transition edge between the face side and the planar side and also obliquely to the planar side to project over the latter, and that the friction stir welding tool simultaneously overlap welds and butt welds while applying pressure towards the planar side.

10. The method according to claim 9 , wherein the second piece of material is placed obliquely onto the first piece of material, contacting the transition edge.

11. The method according to claim 1 , wherein the sidewardly extending portion of the second piece of material overlapping the first piece of material along the flat side is overlap welded to the flat side of the first piece of material only in sections and has an edge strip toward its free end edge, the edge strip not being welded to the first piece of material, the edge strip being severed after the welding process.

12. The method according to claim 11 , wherein in the overlap welding process, a wormhole is produced at the transition of the overlap welded section and the edge strip, the edge strip being severed along the wormhole.

13. The method according to claim 1 , wherein the first piece of material is made of steel and the at least one second piece of material is made of aluminum or copper, or the first piece of material is made of copper and the at least one second piece of material is made of aluminum.

14. The method according to claim 1 , wherein the first piece of material is zinc-plated on the planar side in the overlap welded section, wherein the friction stir welding tool is axially advanced during welding such that the zinc layer remains intact in the non-welded area.

15. The method according to claim 1 , wherein an edge, to be welded, of the first piece of material is measured before or after placing the second piece of material and/or before or during moving the pin and, depending on the measurement, the movement of the pin in relation to the direction toward the first piece of material is open- or closed-loop controlled.

16. A method of friction stir welding a first piece of material to second pieces of material, wherein
the first piece of material has a face side and an adjacent planar side which forms a top side or a bottom side of the first piece of material, and has a melting temperature that is higher by at least 250° C. than that of the at least one second piece of material, characterized by the following steps:
(a) providing a plurality of second pieces of material being of the same material,
(b) arranging one of the second pieces of material having a face side with the face side next to the face side of the first piece of material, wherein the first piece of material has a thickness that is smaller than that of the second piece of material which is arranged adjacent to the face side of the first piece of material,
(c) arranging a further second piece of material on the planar side of the first piece of material which compensates for the difference in thickness of the first and second pieces of material arranged adjacent to their side faces, both second pieces of material further are contacting each other with their face sides, and
(d) wherein the first piece of material is butt welded to the adjacent second piece of material at the adjacent face sides by a friction stir welding tool having a rotating pin, by the pin being moved along the face sides, and the friction stir welding tool being moved along the planar side of the first piece of material to overlap weld the further second piece of material and the first piece of material.

Assignees

• Univ Stuttgart

Inventors

• Werz Martin
• Weihe Stefan

Classifications

• B23K20/122

  using a non-consumable tool, e.g. friction stir welding · CPC title

• B23K20/2275

  the other layer being aluminium · CPC title

• B23K20/1265

  Non-butt welded joints, e.g. overlap-joints, T-joints or spot welds · CPC title

• B23K20/1255 Primary

  Tools therefor, e.g. characterised by the shape of the probe · CPC title