Process for removing inclusions present in a welding seam and device for executing said process

Abstract

A process for removing inclusions (6), in particular silicates, present in the surface region of a welding seam (3), which is manufactured using shielding gas and which joins metallic components (4) to one another is designed in such a manner that the welding seam (3) is impinged by several jets (5) of a fluid medium that is subject to high pressure and by using different angles of incidence.

Description

The present process relates to a process for removing inclusions present in a welding seam in accordance with the preamble of the main claim 1 as well as a device for executing said process.

While welding by means of shielding gas-welding procedures there are precipitations of the components in the metal that are joined to one another by welding and/or the constituents of e.g. silicon, that are present in the welding filler materials that get deposited predominantly as manganese silicate in the surface region of the welding seam.

Gas shielded arc welding can be carried out using various processes. Examples of such processes include metal-inert gas (MIG)-welding or metal-active gas-welding using mixed gas (MAGM). Such deposits that are in a size range of 0.2 to 1 mm and are thus very small are distributed in an irregular pattern over the length and width of the welding seam. The silicates adhere very strongly to the weld metal. The overlapping of the seam material over the inclusion further intensifies this adherence.

Silicate-inclusions in the region of such undercuts cannot be removed using the processes that are known from patent applications such as for instance, JP 103 39 290 A (abstract) and DE 36 26 300 A1.

The latter document proposes the removal of inclusions by means of an abrasive high-pressure water jet using a fine-grained, sandy material as the abrasive material.

However the application of such an abrasive material results in soiling the components that have to be cleaned in a subsequent cleaning process in order to prepare them for further machining. This naturally involves a considerable expenditure of labor and hence does not permit an economically efficient use of the said process. Therefore this process is not suitable for the machining of mass production components.

Even the abrasive effect of the blasting agent on the process devices such as robots etc. whose operability, at least with respect to their durability, can be severely restricted by the penetrating abrasive material proves to be very disadvantageous.

The said inclusions lead to an increased risk of corrosion that adversely affects the strength of the welding seam in the course of time. Most importantly, this factor works against the several efforts made, for instance in the field of automotive engineering, for toward ensuring a longer service life of welded components.

These non-metallic inclusions, in particular the silicates, have lesser adhesive forces than the material the forms the rest of the welding seam. The lacking adhesiveness of the inclusions cause coating defects if the component that is welded together is provided with a coating, for instance, galvanization or a color application.

Such coating defects, besides affecting the visual overall impression of the device, also form potential corrosion spots.

The only option known so far to eliminate inclusions present in the surface region of the welding seam reliably basically comprises of a machining operation, such as grinding etc. that produces metal particles or shavings and in which even the regions that are free of inclusions, are inevitably processed at least in part.

However, a machining operation of such type involves very high expenditure and thus works against the cost-effective manufacturing of components that are used as mass production components, for instance in the field of automotive engineering.

Therefore, the task and objective underlying the present invention is to further develop a process of this kind so as to enable a reliable, economically efficient removal of inclusions in the welding seam.

This objective is achieved by a process having the characteristics specified in the main claim 1, as well as by a device pursuant to claim 12.

As has been seen surprisingly, a thus executed machining operation of the welding seam removes the inclusions, in particular silicates, present in the surface region of the welding seam, where at least one jet of the fluid medium, preferably water, engages at the inclusions in the border region of the adjoining material and detaches the existing joint.

In doing so, the fluid medium is subject to a pressure of 1,500 to 4,000 bar, preferably 2,500 to 3,000 bar.

Since the blasting of the individual inclusions cannot be carried out in a fixed direction or in a targeted manner, the entire surface of the welding seam must be blasted. This can be carried out economically using a rotating nozzle head comprising of several nozzles (n>=2). In accordance with the present invention, the individual jets of fluid medium emerging from the nozzles impinge the welding seam at different angles. This ensures that at least one jet reaches the weakest connection point of the silicate on the metal and thus removes the inclusion.

The nozzles of the nozzle head are preferably adjusted to one another so as to facilitate the focusing by adjusting the gaps between them. This adjustment of the gaps between the nozzles can also be altered during the process pursuant to the present invention.

In a preferred embodiment of the invention, the nozzles are arranged eccentrically in relation to the centerline of the nozzle head and at different distances to the center of the rotation axis. In case of a smaller eccentricity an additional axially arranged nozzle can also be provided.

Contrary to the prior art, the removal of the inclusions using a fluid medium does not involve a machining operation that produces metal particles or shavings if one disregards the detachment of the inclusions and a possible abrasive effect on the welding seam on the whole so that the result is an extraordinarily effective machining process. Furthermore, this machining operation can be automatized completely, thus resulting in considerable cost advantages, while simultaneously optimizing the surface of the welding seam with respect to corrosion resistance and/or coating ability. The latter allows for a completely closed coating that absolutely fulfils the desired purpose of corrosion protection or surface design.

The machining of the welding seam in relation to both the machining result as well as the production-relevant data, for instance consumption of energy or medium and speed of operation can be optimized using a fluid medium, preferably water, that is subject to a pressure of 1,500 to 3,500 bar, several outlet openings of the nozzle, each having a diameter of 0.4 to 0.8 mm, a feed speed of 60 to 90 mm/s, a nozzle speed of 1,000 to 2,000 min⁻¹ where the nozzle is at a distance of approximately 15 to 30 mm from the welding seam.

Additional advantageous embodiments of the present invention have been specified in the characteristics of the dependent claims. Exemplary embodiments of the device in accordance with the present invention are set forth in the following description on the basis of the enclosed drawings of which:

FIG. 1 illustrates the side view of a device in accordance with the present invention in its operating position,

FIG. 2 illustrates an enlarged view of a detail illustrated in FIG. 1,

FIG. 3 illustrates a schematic bottom view of the device.

FIG. 1 illustrates a device for removing inclusions, in particular, silicates present in the surface region of a welding seam 3, which is manufactured using shielding gas and with which two metallic components 4 are joined to one another.

The device has a nozzle head 1 that is connected in a rotating and/or oscillating manner to a rotary drive that is not illustrated here.

In the present embodiment, the nozzle head 1 is provided on its end side with three nozzles 2, from each of which a jet 5 of fluid medium emerges that is subject to high pressure such that the angles of emergence a1 to a3 are adjusted variably inwards, that is to one another and impinge the welding seam 3 at corresponding angles of incidence.

As can be seen clearly especially in FIG. 3, the nozzles 2 are arranged eccentrically to the rotation axis of the nozzle head 1 and at different distances e1 to e3 to one another.

Due to the different angles of incidence, the various eccentricities of the nozzles 2 as well as the rotating and/or oscillating movement of the nozzle head 1, each surface region of the welding seam 3 is impinged by a high pressure jet 5 where the nozzle head can be mounted in such a manner that its progression corresponds to that of the welding seam to be processed, for instance, on a robot etc. when the corresponding workpiece is placed in a stationary position. Alternately the workpiece can be moved in relation to the nozzle head 1, which is then stationary. Either of these cases reliably enables, with the help of any of the jets 5, the detachment of the existing inclusions 6 from their joint with the welding seam.

The complete device can be mounted in such a manner that its progression corresponds to that of the welding seam to be processed, for instance on a robot etc. when the corresponding workpiece is placed in a stationary position.

However, it is also feasible to move the workpiece in relation to the device, which is then stationary.

Claims

1. A process for removing inclusions in particular, silicates, present in the surface region of a welding seam, which is manufactured using shielding gas and which joins metallic components to one another, wherein the welding seam is impinged by several jets of a fluid medium that is subject to high pressure and by using different angles of incidence

2. The process pursuant to claim 1, wherein the jets are applied at the same time.

3. The process pursuant to claim 1, wherein the jets are applied onto the welding seam in a rotating and/or oscillating manner

4. The process pursuant to claim 1, wherein at least a few of the individual jets are adjusted to one another and extend in an inclined manner

5. The process pursuant to claim 1, wherein the jets are guided continuously in the direction of the welding seam

6. The process pursuant to claim 1, wherein the welding seam is moved in relation to the region of incidence of the jets

7. The process pursuant to claim 1, wherein the jets are guided at variable distances (e1 to e3) from a nozzle head

8. The process pursuant to claim 1, wherein at least one jet is guided axially in relation to the centerline of the nozzle head

9. The process pursuant to claim 1, wherein the fluid medium is subject to a pressure of 1,500 to 4,000 bar.

10. A device for executing the process pursuant to claim 1, wherein an arrangement is provided that comprises of several nozzles for a fluid medium that is subject to high pressure and that the nozzles extend at variable angles of inclination (α1-α3).

11. A device pursuant to claim 10, wherein at least a few of the nozzles are adjusted to one another and extend in an inclined manner.

12. A device pursuant to claim 10, wherein the nozzles are arranged in a nozzle head.

13. A device pursuant to claim 10, wherein the nozzle head can be moved in a rotating and/or oscillating manner.

14. A device pursuant to claim 10, wherein said device can be moved in relation to the welding seam to be processed.

15. A device pursuant to claim 10, wherein the relative movement of the device or of the workpiece provided with the welding seam amounts to approximately 60 to 90 mm/s.

16. A device pursuant to claim 10, wherein the speed of the nozzle head during operation is approximately 1,000 to 2,000 min−1.

17. A device pursuant to claim 10, wherein the diameter of the nozzles is approximately 0.4 to 0.8 mm.