CN116685431A

CN116685431A - Friction stir welding tool, welding method, and sheet welding machine

Info

Publication number: CN116685431A
Application number: CN202180087402.8A
Authority: CN
Inventors: 雷纳托·比安奇
Original assignee: Miwenti SRL
Current assignee: Miwenti SRL
Priority date: 2020-12-22
Filing date: 2021-12-22
Publication date: 2023-09-01
Also published as: IT202100005096A1

Abstract

A friction stir welding tool (4) for welding right (DX) and left (SX) tabs of one sheet metal (21) or two or more sheet metal comprises an integrally formed body comprising a base portion (41) which is anchorable to a tool holder head (3) for a welding machine (1) and a shank portion (42) which, when in use, extends from the base portion in a predominantly axial direction (K) between a base end (42 ') and a head end (42') which is parallel or coincident with a rotational axis (400) of the tool. The shank portion (42) has a conical shape towards the head end (42') and comprises a side surface (420) extending around and along an axial direction (K), provided with protrusions (421) and recesses (422) shaped to mix and convey molten metal towards the surface of the metal sheet (21) being welded, i.e. in the axial direction (K) and towards the base portion (41) of the tool (4), during the welding operation.

Description

Friction stir welding tool, welding method, and sheet welding machine

The present invention relates generally to the field of welding large-sized sheets, for example for producing ingot molds made of sheet material and suitable for receiving molten metal in an industrial production process of billets, such as continuous casting.

More particularly, the present invention relates to friction stir welding tools (friction stir welding tool), sheet welding methods, and sheet welders.

It is well known in the art to weld between metal sheets, i.e., between two tabs/flaps (flaps) of one or more metal sheets.

For example, with particular reference to the steel industry, the construction of copper ingot moulds involves rolling a copper sheet (plate) so as to form a cylindrical cavity, followed by welding between two opposite fins of the plate placed next to each other, so as to completely close the only longitudinal slit left during rolling.

This process of welding the two fins is performed by known fusion welding of the two fins after carefully heating the whole copper piece.

Disadvantageously, this known welding process involves a number of problems. First, the entire copper part needs to be heated, which requires high energy consumption and heating time; furthermore, the aforementioned manually performed welds are highly dependent on the skill of the particular operator performing the weld, and thus create non-uniformities within a single weld, as well as between different and subsequent welds. Furthermore, due to its manner of manufacture, the weld often has internal defects that can lead to failure of the welded area over time.

Furthermore, welding performed with known techniques does not always succeed in meeting the tolerance requirements required for producing high quality manufactured articles (e.g. ingot molds).

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art methods. In particular, it is an object of the present invention to provide a friction stir welding tool, a sheet welding method and a sheet welding machine which can reduce the time required for welding, require less resources, and as a result are reliable and uniform.

According to the present invention, these objects are achieved by a friction stir welding tool, a sheet welding method and a sheet welding machine according to the appended independent claims. Preferred embodiments of the invention are defined in the dependent claims.

The features and advantages of the friction stir welding tool, sheet welding method and sheet welder will become apparent from the following description, given by way of non-limiting example in accordance with the accompanying drawings in which:

fig. 1 shows a perspective view of a welding machine according to an embodiment of the invention;

fig. 2 shows a front view of a welding machine in a step of a welding method according to an embodiment of the invention;

fig. 3 shows details of the steps of a method for manufacturing an ingot mould according to an embodiment of the invention;

fig. 4 shows a detail of the steps of the method of manufacturing an ingot mould according to an embodiment of the invention, after the steps in fig. 3;

fig. 5 shows a detail of the steps of the method of manufacturing an ingot mould according to an embodiment of the invention, after the steps in fig. 4;

fig. 6 shows a perspective view of a welding machine according to an embodiment of the invention;

fig. 7 shows a detail of the welder of fig. 6, but wherein the mold has a geometry of different cross-sections;

fig. 8 shows a perspective view of a welding machine according to another embodiment of the invention;

figure 9 shows a support structure for a welding machine according to an embodiment of the invention;

fig. 10 shows a tool holder head for a welding machine according to an embodiment of the invention;

fig. 11 shows a tool for a tool holder head for a welding machine according to an embodiment of the invention.

According to the figures, reference numeral 1 generally indicates a welder 1 for welding one or more sheets 21 by friction stir welding, for example, preferably for manufacturing an ingot mould 2.

In order to perform welding of a sheet (i.e., two tabs of the same sheet) or several sheets together (i.e., two tabs respectively belonging to different sheets), a welding method will be described below.

In particular, for the sake of simplicity and without loss of generality, the method of manufacturing the ingot mould 2, i.e. the method for welding the metal sheet 21 intended to manufacture the ingot mould, will be described. However, it is also clear that friction stir welding tools, sheet welding methods and sheet welders are intended to weld sheet metal, even if the sheet metal is not the sheet metal from which the ingot mold is made, but any sheet metal other than the sheet metal from which the ingot mold is made.

Thus, in the following description, a metal sheet may be understood as any metal sheet, possibly excluding an ingot mould or a metal sheet intended for manufacturing an ingot mould.

A general embodiment of a method of welding sheet 21 (i.e., for welding the right and left flaps DX, SX of the sheet to each other) comprises the following steps (preferably performed in the order indicated):

a) Providing one or more sheets of metal material 21 extending in a main extension direction X and having the left and right fins SX, DX of the one or more sheets of metal material 21 arranged closely one before the other, the one or more sheets of metal material 21 being arranged on a work plane P;

b) Providing a tool holder head 3 translatable at least in a direction parallel to the main extension direction X, the tool holder head supporting a friction stir welding tool 4;

c) The tool 4 is rotated at the right and left fins DX, SX of the metal sheet 21 and the welding is performed between the right and left fins DX, SX by friction stir welding until a complete mutual welding of the fins is achieved.

With particular reference to the welding of sheet metal for mould construction, but obviously generalizable to any welding of sheet 21 for manufacturing any curved product, or in any case cylindrical or semi-cylindrical or partially cylindrical product, the method provides particular considerations for steps a), b) and c) above:

a) Providing a copper sheet 21 wound around the main extension direction to enclose the inner cavity I, and closely arranging left and right fins SX and DX of the sheet 21 to face each other; in this step, the sheet 21 is arranged on a work plane P (e.g., a work plane of a numerical control machine tool);

c) The tool 4 is rotated at the right and left fins DX, SX of the metal sheet 21 and welding is performed between the right and left fins DX, SX by friction stir welding until the ingot mould 2 is obtained.

If the method is not used for manufacturing ingot moulds, it is clear that in step a) it is preferable to avoid arranging the copper sheet 21 to be wound around the main extension direction.

Preferably, before step c), the welding method comprises the step of positioning the support structure 5 within the internal cavity I. The support structure 5 comprises a backing surface 51 which counteracts the mechanical pressure exerted by the tool on the sheet when step c) is performed.

Preferably, the method provides: a step of cooling the tool holder head 3 by a cooling liquid during step c).

According to a particularly advantageous variant, during step c), the method provides: around the rotating tool 4, an inert gas (e.g., argon) is dispensed over the weld joint formed between the right and left fins DX, SX, thereby avoiding inclusion of other components in the weld.

According to a preferred embodiment of the method, step c) comprises the steps of, preferably performed in the indicated order:

c1 Rotating the tool 4 at the right DX and left SX tabs of the sheet metal (step a in fig. 3);

c2 Initially penetrating the tool 4 into the material of the metal sheet 21 until a predetermined depth D (fig. 4) is reached;

c3 Detecting a force value generated between the tool 4 and the metal sheet 21 by a force sensor arranged in the tool holder head 3;

c4 Detecting a temperature value by means of a temperature sensor positioned on the tool holder head 3, possibly simultaneously with step c 3);

c5 If the force value detected by the force sensor exceeds a predetermined force threshold value and if the temperature value measured by the temperature sensor exceeds a predetermined temperature value, the advance of the tool holder head 3 in the main extension direction X is started.

Preferably, the predetermined force threshold is any value at least equal to 9000N, and the predetermined temperature value is at least equal to 600 ℃ and below 700 ℃, and the number of rotations of the tool 4 is at least equal to 300 rotations per minute (rpm).

According to an aspect of the invention, it is evident that the above method is also intended to weld between the right and left flaps DX and SX of two different sheets placed side by side. That is, in step a), the first sheet and the second sheet may also be arranged adjacent to each other such that the right tab DX of the first sheet approaches the left tab SX of the second sheet, instead of providing one rolled sheet such that the two left and right tabs belong to the same sheet.

According to a variant of the method, in which there is provided welding of the right DX and left SX tabs of one or more copper sheets having a plate thickness of at least 15mm, preferably 19mm to 22mm, the method provides for maintaining the average temperature of the sheets in the vicinity of the tool 4 at about 700 ℃, a speed of advance in the main extension direction X of about 28mm per minute and a number of rotations of the tool 4 of about 350 revolutions per minute. This achieves a defect-free weld.

It is evident that the welder 1 is also an object of the invention, which welder is preferably used, for example, for welding between sheets in addition to manufacturing ingot molds.

According to a variant, the welder 1 can also be used to manufacture ingot moulds 2.

The welding machine 1 comprises a tool holder head 3 supporting a friction stir welding tool 4, and a tool holder head moving device 10, for example a numerical control machine having three axes, which supports the tool holder head 3 and comprises at least one translation assembly 11, such as one or more carts (carts), adapted to translate the tool holder head 3 in a controlled manner along a direction parallel to the main extension direction X of the sheet 21 (or ingot mould 2) and a vertical direction Z related to the main extension direction X or perpendicular.

Preferably, the tool 4 is made of a D2M W-Ni-Mo-Fe alloy (i.e., tungsten nickel molybdenum iron alloy) or a tungsten-rhenium 75-25 alloy or a silicon nitride alloy.

Preferably, the welding machine 1 comprises a work plane P adapted to support the sheet metal 21 during welding, preferably in addition to the ingot mould, and a locking frame 6, the locking frame 6 being releasably fixed to the work plane P. The locking frame 6 comprises an upper frame portion 61 spaced apart from the working plane P in the vertical direction Z. The upper frame portion 61 is adapted to exert a pressure on the metal sheet 21 in the vertical direction P in the vicinity of the slit 22 of the metal sheet 21 to be welded.

According to an embodiment, the working plane P may be adapted to support the ingot mould 2, while the upper frame portion 61 is adapted to exert pressure on the ingot mould 2.

According to an embodiment, the locking frame 6 comprises a plurality of plates 62 spaced apart along the main extension direction X and having shaped concave surfaces 621 for receiving and holding the ingot mould 2 in place at least in a direction perpendicular to the main extension direction X.

According to an embodiment variant, the locking frame comprises at least two vertical uprights 64, 65, each fixed to the work plane P on opposite sides with respect to the sheet metal. On each of these vertical uprights 64, 65, a strip 641, 651 is fixed in the upper region 64', 65' of the vertical upright, which strip extends mainly in the main extension direction X and is adapted to exert a pressure in the vertical direction Z.

Preferably, the welding machine 1 comprises lower fixing means 642, 652 fixed in lower regions 64", 65" of the upright closer to the working plane P than the upper regions 64', 65'. The spacer elements 7, 7' (such as screws) are fixed to the lower fixing means 642, 652 and are adapted to laterally constrain the metal sheet 21 against movement in a transversal direction Y perpendicular to both the main extension direction X and the vertical direction Z.

According to an advantageous embodiment, the welding machine 1 comprises a support structure 5 adapted to be positioned inside the cavity I of the ingot mould. The support structure 5 comprises a backing surface 51 which counteracts the mechanical pressure exerted by the tool 4 on the sheet metal when welding is performed.

Preferably, the tool holder head 3 comprises one internal liquid cooling circuit 31 and at least one internal welding gas delivery circuit 32. The internal welding gas delivery circuit 32 includes a gas outlet nozzle positioned around the tool and adapted to dispense a gas, preferably an inert gas, to ensure an inert atmosphere during welding to avoid inclusion of other substances in the weld.

According to one aspect of the invention, the tool 4 is an integrally formed body comprising a base portion 41 which is anchorable to the tool holder head 3, and a shank portion 42 which, when in use, extends from the base portion, mainly in an axial direction K, parallel or coincident with the axis of rotation 400 of the tool, between the base end 42' and the head end 42 ". The shank portion 42 has a tapered shape toward the head end 42 ". Preferably, the shank portion has a substantially frustoconical shape with a smaller base adjacent the head end 42 ".

In addition, the shank portion 42 includes a side surface 420 that extends around and in the axial direction K, provided with a protrusion 421 and a recess 422. Preferably, the protrusions and recesses are crests and roots of threads formed on the side surfaces 420. In particular, the protrusions 421 and recesses 422 are shaped to mix and convey molten metal towards the surface of the metal sheet being welded (i.e., along the axial direction K and towards the base portion 41 of the tool 4) during the welding operation.

Furthermore, according to an advantageous embodiment, the side surface 42 comprises one or more cut-outs or interruptions in the shape of a cone. Preferably, the cut or interruption is a flat side 423, 423' arranged around the axial direction K, each lying in a secant plane with respect to the axial direction K, i.e. inclined to converge towards the head end 42 ".

Preferably, in a variation of the frustoconical shape of the shank portion 42, the sides 423, 423' are flat milling portions of the curvilinear conical side surface 42. Preferably, this variant comprises three sides 423, 423',423″ arranged around the axial direction K and angularly spaced 120 °.

During the welding operation, i.e. during rotation of the tool 4 in the sheet metal, the shank portion 42 is subjected to a torque about the axial direction K, causing a slight torsion of the shank portion 42. This results in the sides 423, 423' deforming into a curved or twisted or serpentine shape during the welding action. This curved, serpentine or twisted shape creates a preferential path for the molten metal circulation of the welded metal sheet, thus facilitating the metal mixing between the right and left fins DX, SX of the sheet to be welded, for example, the transfer of the molten material from the right fin to the left fin, or vice versa. This ensures that the joint is correctly welded.

In addition, the curved or serpentine or twisted shape assists in transporting the molten metal toward the outermost surface of the sheet metal 21.

According to an embodiment of the invention, the base portion 41 comprises a base surface 410 extending around the shank portion 42, preferably completely around the shank portion 42, in a plane perpendicular to the axial direction K. The base surface 410 is adapted to contact the outermost surface of the metal sheet 21 during the welding step. Preferably, one or more grooves 411 or shaped ridges are obtained on the base surface 410 for displacing the fluid metal material towards the rotation axis 400 of the tool.

According to a preferred embodiment, as shown for example in fig. 11, one or more grooves 411 or ridges are shaped like a flat spiral.

According to a preferred embodiment of the invention, the welding step of the above method (i.e. for example during step c) or c 5)) occurs in the event of a tilting of the rotation axis 400 of the tool 4, which is not perpendicular to the tangential plane P' of the left and right fins SX and DX of the metal sheet 21. In other words, for example, the rotation axis 400 of the tool 4 is not perpendicular to the working plane P, but is inclined by at least 1 °, preferably by at least 2 °, with respect to being perpendicular to the working plane P (for example, as shown in fig. 3, 4 and 5). This is the case, for example, because the working plane P of the welder 1 can be tilted as desired, i.e. the welder comprises a device for tilting the working plane P. Alternatively or simultaneously, this occurs because the tool holder head moving means 10 is configured to support the tool holder head 3 such that the tool 4 advances in the main extension direction X, but the rotation axis 400 is inclined with respect to being perpendicular to the tangential plane P'.

Innovatively, the method for manufacturing an ingot mold and the ingot mold welder according to the present invention can well overcome the problems encountered in manufacturing an ingot mold in the prior art.

In particular, the method for manufacturing an ingot mould according to the invention enables to reduce the time required for welding sheet metal, in particular in the case of manufacturing an ingot mould, requires less resources and improves the welding quality compared to welding performed with the prior art.

Advantageously, the manufacturing method according to the invention does not require preheating the metal sheet for welding of the metal sheet, thereby saving considerable time and energy.

Furthermore, advantageously, the presence of the releasable locking frame enables the metal sheets or ingot moulds of different diameters and different lengths to be fixed to the work plane in a stable manner, ensuring flexibility of use of the welder and sufficient locking to prevent possible displacements that could affect the welding quality.

Furthermore, advantageously, there is a support structure adapted to be positioned within the cavity of the sheet/mould, which allows counteracting the mechanical forces exerted by the tool 4 on the metal sheet when performing the welding and ensures an improved welding quality, since the sheet is less subject to local bending during welding.

According to another innovative aspect, the tool 4 is provided with a conical shaped shank portion 42 provided with protrusions 421 and recesses 422 for efficient delivery of the fluid metal during welding, thus allowing to optimize the welding operation both from the point of view of the welding quality and from the point of view of the overall operating efficiency.

It is obvious that a person skilled in the art, in order to satisfy contingent and specific needs, may make modifications to the invention described above, all contained within the protective scope as defined in the accompanying claims.

Claims

1. A friction stir welding tool (4) for welding a right (DX) and left (SX) tabs of one sheet metal (21), or two or more sheet metal, the tool (4) comprising an integrally formed body comprising a base portion (41) which is anchorable to a tool holder head (3) of a welding machine (1) and a shank portion (42) which, when in use, extends from the base portion between a base end (42 ') and a head end (42') predominantly in an axial direction (K) which is parallel or coincident with an axis of rotation (400) of the tool,

wherein the shank portion (42) has a conical shape towards the head end (42 ") and comprises a side surface (420) which surrounds and extends along the axial direction (K), the side surface being provided with protrusions (421) and recesses (422) shaped to mix and convey molten metal towards the surface of the metal sheet (21) being welded, i.e. in the axial direction (K) and towards the base portion (41) of the tool (4), during a welding operation.

2. Tool (4) according to claim 1, made of a tungsten nickel molybdenum iron (D2M W-Ni-Mo-Fe) alloy.

3. Tool (4) according to claim 1 or 2, wherein the shank portion (42) has a substantially frustoconical shape with a smaller base near the head end (42 ").

4. A tool (4) according to claim 1 or 2 or 3, wherein the side surface (42) comprises one or more cut-outs or discontinuities in the shape of a cone.

5. Tool (4) according to claim 4, wherein the cutting or interruption is a flat side (423, 423 ") arranged around the axial direction (K) and each lying on a secant plane with respect to the axial direction (K), i.e. the side being inclined to converge towards the head end (42").

6. A tool (4) according to any one of claims 3 and 5, wherein the side surfaces (423, 423 ') are flat milling of a curved conical side surface (42) such that during rotation of the tool (4) in the sheet metal piece (21), the shank portion (42) is subjected to a torque about the axial direction (K) deforming the side surfaces (423, 423') so as to assume a curved or twisted or serpentine shape suitable for forming a preferential circulation channel of molten metal of the sheet metal piece.

7. Tool (4) according to claim 6, wherein the sides (423, 423 ') comprise three sides (423, 423',423 ") arranged around the axial direction (K) and angularly spaced apart from each other by 120 °.

8. Tool (4) according to any one of the preceding claims, wherein the base portion (41) comprises a base surface (410) extending around the shank portion (42) in a plane perpendicular to the axial direction (K), preferably extending completely around the shank portion (42),

and wherein the base surface (410) is adapted to be in contact with the outermost surface of the metal sheet (21) during the welding step,

and wherein one or more grooves (411) or shaped ridges are obtained on the base surface (410) to displace the fluid metal material towards the rotation axis (400) of the tool.

9. The tool (4) according to claim 8, wherein the one or more grooves (411) or ridges are in the shape of a flat spiral.

10. A method of welding sheet metal (21) for welding between a right (DX) and a left (SX) wing of sheet metal, the method comprising the steps of:

a) Providing one or more sheets of metallic material (21) extending along a main extension direction (X) and having left (SX) and right (DX) tabs of said one or more sheets of metallic material (21) arranged closely one before the other, said one or more sheets of metallic material (21) being arranged on a work plane (P);

b) -providing a tool holder head (3) translatable at least in a direction parallel to the main extension direction (X), the tool holder head (3) supporting a friction stir welding tool (4) according to any of claims 1 to 9;

c) The tool (4) is rotated at the right (DX) and left (SX) tabs of the metal sheet (21) and welding is performed between the right (DX) and left (SX) tabs by friction stir welding until complete mutual welding of the tabs is achieved.

11. Method according to claim 10, wherein prior to step c) the method comprises the step of positioning a support structure (5) under the right wing (DX) and the left wing (SX), the support structure (5) comprising a backing surface (51) counteracting the mechanical pressure exerted by the tool on the metal sheet (21) when step c) is performed.

12. A method according to any one of claims 10 to 11, comprising the step of cooling the tool holder head (3) by means of a cooling liquid during step c).

13. The method according to any one of claims 10 to 12, wherein during step c), the method comprises: around the rotating tool (4), an inert gas, such as argon, is distributed over the weld joint formed between the right and left fins (DX, SX).

14. The method according to any one of claims 10 to 13, wherein said step b) comprises the steps of:

c1 -rotating the tool (4) at the right (DX) and left (SX) fins of the sheet metal;

c2 -initially penetrating the tool (4) into the material of the metal sheet (21) until a predetermined depth (D) is reached;

c3 -detecting a force value generated between the tool (4) and the metal sheet (21) by means of a force sensor arranged in the tool holder head (3);

c4 -detecting a temperature value by means of a temperature sensor positioned on the tool holder head (3);

c5 If the force value detected by the force sensor exceeds a predetermined force threshold value and if the temperature value measured by the temperature sensor exceeds a predetermined temperature value, the advance of the tool holder head in the main extension direction (X) is initiated.

15. The method according to claim 14, wherein the predetermined force threshold is any value at least equal to 9000N, and wherein the predetermined temperature value is at least equal to 600 ℃ and below 700 ℃, and wherein the number of rotations of the tool (4) is at least equal to 300rpm.

16. A welder (1) for welding one or more metal sheets (21) for friction stir welding according to the method of any one of claims 10 to 15, the ingot mould welder (1) comprising:

-a tool holder head (3) supporting a tool (4) for friction stir welding;

-a tool holder head movement device (10), for example a numerical control machine with three axes, which supports the tool holder head (3), and which comprises at least one translation assembly (11), for example one or more trolleys, adapted to translate the tool holder head (3) in a controlled manner in a direction parallel to a main extension direction (X) of the ingot mould (2) and in a vertical direction (Z) related or perpendicular to the main extension direction (X).

17. Welding machine (1) according to claim 16, comprising a work plane (P) adapted to support the metal sheet (21) during welding and a locking frame (6) releasably fixed to the work plane (P) and comprising an upper frame portion (61) spaced from the work plane (P) in the vertical direction (Z) and adapted to exert a pressure on the metal sheet (21) in the vertical direction (Z) close to a slit (22) in the metal sheet (21) to be welded.

18. The welding machine (1) according to claim 17, wherein the locking frame (6) comprises a plurality of plates (62) spaced apart along the main extension direction (X) and having shaped concave surfaces (621) for receiving and holding the metal sheet (21) in place at least in a direction perpendicular to the main extension direction (X).

19. The welding machine (1) according to any one of claims 16 to 18, comprising a support structure (5) adapted to be positioned under the right wing (DX) or the left wing (SX), the support structure (5) comprising a backing surface (51) that counteracts the mechanical pressure exerted by the tool (4) on the sheet metal when welding is performed.

20. The welding machine (1) according to any one of claims 16 to 19, wherein the tool holder head (3) comprises one internal liquid cooling circuit and at least one internal welding gas delivery circuit comprising a gas outlet mouth positioned around the tool and adapted to dispense a gas, preferably an inert gas, ensuring an inert atmosphere during welding to prevent inclusion of other substances in the weld.