WO2015106967A1

WO2015106967A1 - Nozzle for covering welds with assisting gas

Info

Publication number: WO2015106967A1
Application number: PCT/EP2015/000068
Authority: WO
Inventors: Barbara Previtali; Daniele Colombo; Bruno Valsecchi; Giovanni Riva
Original assignee: Politecnico Di Milano
Priority date: 2014-01-16
Filing date: 2015-01-16
Publication date: 2015-07-23

Abstract

Device (1) for covering welds with assisting gas, with improved efficiency over prior art devices comprising: a coupling portion (2) arranged to associate the device (1) to a welding head; and a delivering portion (3) comprising at least one main nozzle (4), orientated according to a main axis (x), the main nozzle (4) being provided with an orifice (5) for delivering an assisting gas at a welding area and with an inlet aperture (6), the inlet opening (6) and orifice (5) being passed through by a through axis (y) inclined relative to the main axis (x) of the main nozzle (4), such as to allow for the passage of a thermal beam, for example a laser beam, coming from the welding head.

Description

NOZZLE FOR COVERING WELDS WITH ASSISTING GAS

DESCRIPTION

Field of application

The present invention relates to a device provided with an individual nozzle or a train of nozzles for covering welds with assisting gas, which is particularly intended for welding processes using a thermal beam, for example laser, TIG, electronic beam, MIG, MAG, and plasma welding.

This invention also relates to a welding machine which either integrates or mounts a covering device of the above-mentioned type. This invention is thus particularly suitable for application in the field of industrial welding, particularly with reference to welding processes using a thermal beam.

Prior Art

In the above-mentioned industrial field, the permanent joint of two flaps placed side by side, typically of a metallic material, is achieved by means of localised heating thereby causing the melting and subsequent solidification thereof.

Said heating can be obtained by means of a number of techniques known in the art, and in particular can be carried out by means of a thermal beam, such as in the field of laser welding.

The need for laser welding, as well as for welding carried out with other technologies using a thermal beam, to prevent high-temperature metal from coming in contact with the surrounding atmosphere is known, in order to avoid the occurrence of aesthetic and structural defects which may be caused by contaminations (for example oxidation or formation of nitrides) .

In order to achieve this goal, an inert assisting gas (such as argon, although other types of gases or mixtures can be certainly be used) is blown at the welding seam just formed, such as to temporarily replace the atmosphere right where the metal is still at such a temperature that may promote the occurrence of contamination phenomena.

The assisting gas is typically delivered by means of a suitable nozzle, inclined relative to the thermal beam axis, which opens at the just-formed welding seam, i.e. downstream the melted pond. In order to extend the protective atmosphere to the next seam portion as well, during the cooling, the individual nozzle is sometimes replaced with a train of nozzles placed side by side, which follow the course of the welding.

Still in the industrial welding field, it is further known to use optoelectronic control systems intended to monitor the welding, which are also intended to prevent aesthetic and/ or structural defects. These systems provides for the use of a suitable optical collimator mounted at the welding head and orientated in the direction of the melted pond and/ or subsequent seam being cooled.

While the prior art described above substantially meets the needs of the field, it nevertheless has several currently unresolved drawbacks.

First of all, the covering by means of assisting gas carried out by known devices still results imperfect in some cases, as it causes the formation of undesired oxidations of the welding seam. Particularly, this drawback occurs when the welding is carried out on particularly critical materials, such as titanium. On the other hand, welding on titanium is increasingly important mainly in the aerospace sector, where the presence of imperfections in the seam should be avoided by all means.

The need is also felt to provide two separate devices at the weld pond: a nozzle intended for the emission of assisting gas and a collimator for the optoelectronic monitoring of the process. This results in drawbacks related to the overall size and increase in the manufacturing costs and times for preparing the machine. Furthermore, the overall size of the nozzle interferes with visual access to the interaction point between the thermal beam and the surface to be welded, which is necessary for optimum monitoring.

A further drawback results from the poor flexibility of the covering device with a train of nozzles. The extension of the train must, in fact, be designed with particular reference to certain materials and welding 0068

- 3 - parameters, which affect the seam cooling profile. Thus, in order to carry out welding with different parameters, either the train of nozzles needs to be replaced, or a non-optimum covering must be accepted.

Accordingly, the technical problem at the base of the present invention is to conceive a device for covering welds with assisting gas which overcomes the prior art drawbacks and particularly allows a sensible improvement in the covering, thereby enabling to achieve quality welding even on critical materials such as titanium.

Summary of the invention The above-mentioned technical problem is solved by means of a device for covering welds with assisting gas, comprising: a coupling portion arranged to associate the device to a welding head; and a delivering portion comprising at least one main nozzle, orientated according to a main axis, which is provided with an orifice for delivering an assisting gas - for example argon, although other types of gases or mixtures can be certainly used at a welding area, as it is known to those skilled in the art.

The main nozzle further has an inlet opening, the inlet opening and the nozzle orifice being passed through by a through axis inclined relative to the main axis of the main nozzle. The main nozzle thus results to be arranged for enabling a thermal beam from the welding head and orientated according to said through axis to pass through said inlet opening and said orifice.

In a preferred embodiment of the present invention, the welding head to which the device is associated is a welding head laser, and the thermal beam that passes through the inlet opening is the laser beam generated therefrom. Furthermore, those skilled in the art will appreciate that the device described above can be also advantageously applied to other types of industrial welds, as far as they are arranged to generate a thermal beam, by suitably adjusting the size of the inlet opening based on the type of beam. Weld types can be, for example, TIG, electronic beam, MIG, MAG, or plasma. The provision of the inlet opening on the main nozzle substantially allows bringing the assisting gas right in the interaction point between the thermal beam and the material surface. Thereby, since the melted pond is already formed in an inert atmosphere, it prevents the occurrence of contaminating phenomena, such as oxidation, right from the beginning. The test results obtained by the Applicant show that the resulting quality of the welding is considerably improved.

It should be noted that the main nozzle orifice is preferably arranged for opening flush above the material to be welded, and therefore has a non- orthogonal layout relative to said nozzle main axis, which is on the other hand inclined relative to the work surface.

The main nozzle defines an internal channel for the assisting gas to flow therethrough, which preferably extends according to the main axis and opens to the main nozzle orifice. Said internal channel can be integrated to an optoelectronic control system for acquiring optical information relative to the welding area through the internal channel and the nozzle orifice.

Accordingly, the internal channel advantageously performs a double function of delivery channel for the assisting gas and optical collimator for the optoelectronic control system.

A distal end of internal channel, counter-posed to the nozzle orifice, can be opened to allow the introduction of a component of the optoelectronic control system; for example an optical fiber connector.

Therefore, the optoelectronic control system can be quickly interfaced to the nozzle, by means of simply inserting the optical fibre connector at the distal end.

At the distal end, protection or focalization elements can be also provided, such as lenses or screens, as long as these^~elements are transparent to the monitoring radiation, such that they do not block the visual channel passing through the internal channel.

The main nozzle has at least one inlet for the assisting gas, which can advantageously be opened laterally on the internal channel relative . to the main axis. Thereby, the connection of the assisting gas does not interfere with the collimation axis defined by the internal channel.

Said portion can comprise one or more auxiliary nozzles, which are also provided with an orifice for an assisting gas, the main nozzle and the auxiliary nozzles defining a train of nozzles placed side by side to each other, the orifices being aligned to each other and arranged to cover a welding seam.

In this case, said auxiliary nozzles can have the same characteristics as the main nozzle, particularly being arranged for optoelectronic monitoring and lateral connection to the source of assisting gas.

It should be noted that the individual nozzles can, in this case, define optical collimators of the optoelectronic monitoring system which are independent from each other, thereby allowing different types of detections on the various process areas. Furthermore, since each nozzle can be independently supplied with assisting gas, different flow rates and types of gases can be selected for the various nozzles.

The orifices of said principal and auxiliary nozzles can have a section provided with two substantially rectilinear sides, the sections of the adjacent orifices having corresponding rectilinear sides placed side by side to each other.

By placing the rectilinear sides side by side to each other, any discontinuity points present in the train of circular- section nozzles currently used can be eliminated, thereby ensuring a more even distribution of the assisting gas. Particularly, the nozzle orifices can have polygonal - such as triangular, rectangular or hexagonal - sections which are equal and placed side by side to define an overall continuous impression.

Said auxiliary nozzles, such as the main nozzle, if applicable, can be individually and removably mounted to the delivering portion. Thereby, the extension of the train of nozzles can be easily changed by changing the number of said auxiliary nozzles, according to the parameters and materials to be welded. - . To the purpose of making the modular structure discussed above, the delivering portion can, for example, comprise a support arm provided with a plurality of parallel and contiguous transversal seats for one or more of the auxiliary nozzles and main nozzles to be removably mounted therein. The technical problem discussed above is also solved by a welding machine, such as a laser welding machine, comprising a welding head to which a device for covering welds with assisting gas having the characteristics described above is associated, wherein said welding head is oriented according to the through axis. It should be noted that the covering device mentioned above can be either removably mounted to the welding head or integrated in the structure thereof. The device can also not being directly supported by the welding head, as long as it is in some way associated or arranged to move along with the latter while the machine is operating. Further characteristics and advantages will be more apparent from the following detailed description of a preferred, though not exclusive, embodiment, of the present invention, with reference to the annexed figures, which are given as a non-limiting example.

Brief description of the drawings Fig. 1 shows a side view of the device according to the present invention;

Fig. la shows an enlarged detail of the view of Fig. 1, at the nozzle orifices;

Fig. lb shows a bottom view of the detail of Fig. la;

Fig. 2 shows a top view of the device of Fig. 1 ;

Fig. 3 shows a front view of the device of the preceding figures; Fig. 4 shows a side view, sectioned along a. middle axis, of the device of the preceding figures;

Fig. 5 is similar to the view of Fig. 4 with the additional illustration of a thermal beam generated by a welding head, not represented;

Fig. 6 shows a side view of the device of the preceding figures associated to a welding head;

Fig. 7 shows a perspective view of the device associated to the welding head of Fig. 6.

Detailed description With reference to the attached figures, a device for covering welds with assisting gas, which can be removably mounted to a welding head 100, only schematically illustrated in Figs. 6 and 7 is generally designated with 1.

The device 1 and the welding head 100 associated thereto are illustrated in the figures according to a specific operating configuration; herein below, the positions and orientations -both relative and absolute- of the various elements composing the unit, which are defined by words such as upper and lower, above and below, horizontal and vertical, or other equivalent words, should be always intended as referring to this configuration. Accordingly, they should not be intended as limitations in any case.

In the embodiment described with reference to the attached figures, the welding head 100 is intended for laser welding and is part of a welding machine for industrial use of a type known per se. On the other hand, it should be noted that the device 1 according to the present invention can be alternatively applied to a welding head 100 generating a thermal beam by applying another type of technology, such as TIG, electron beam, MIG, MAG, plasma, or others.

The welding head 100 is orientated according to a vertical axis, which herein below will be designated as a through axis y. In operating conditions, the welding head 100 generates a laser beam 101 orientated according to the through axis y, and is arranged to operate above a working surface substantially orthogonal to said through axis y.

The device 1 has a coupling portion 2, which enables the mounting above the welding head 100, to which a delivering portion 3 having a train of nozzles for delivering assisting gas above the work surface is pivotally connected.

The coupling portion 2, schematically illustrated in the figures, in this embodiment consists of two side plates 20 sandwiching the welding head 100 therebetween; a bolt 21 connects these plates 20 and defines the attachment pin of a support arm 10 of the delivering portion 3. By tightening the bolt 21 , the locking of the relative orientation of the two portions 3 and 4 is ensured.

The support arm 10, which results to be inclined of approximately 45° relative to the axis of the welding head 100, supports the plurality of nozzles 4, 4' composing said train of nozzles.

Particularly, said support arm 10 has, equally spaced along the extension thereof, a plurality of cylindrical transversal seats 1 1 for the relative nozzles 4, 4' to be slidingly accommodated therein. Set screws 12 are also provided to lock the nozzles into their seats 1 1.

The above-mentioned system has a modular nature, as the number of nozzles 4, 4' supported by the support arm 10 can be changed according to the particular welding needs. In the case illustrated in the attached figures, for example, five nozzles 4, 4' are inserted in a total number of seven seats 1 1 ; if other nozzles are inserted in the two empty seats, or if several of the five nozzles are removed, the operator can change the extension of the train of nozzles. Given the modular nature of the attachment system, the nozzles 4, 4' are identical to each other, except for an inlet opening 6 of the laser beam which is only required for the head nozzle. In order to highlight this difference, this nozzle will be designated below as the main nozzle 4, in order to be differentiated from the secondary nozzles 4' that are arranged at the rear thereof.

The main nozzle 4, given the above-described geometry of the support structure, is longitudinally extended according to a main axis x inclined relative to the through axis y of approximately 45°.

It comprises a proximal portion 13 intended to directly cover the work surface, which is followed by an intermediate portion 14 and a distal end portion 15. The three sections are tubular such as to define an internal channel 7, aligned with the main axis x, which opens at the proximal end to define a nozzle orifice 5, and at the distal end 8 to allow inserting an instrument for the optoelectronic monitoring of the process.

The proximal portion 13 has a square-section tubular structure. The proximal end is inclined of 45° relative to the element cross section, such that the nozzle orifice 5 which opens thereat has a rectangular section. The proximal end and the nozzle orifice 5 thus result to be parallel to the underlying surface to be welded, and can move flush above the latter, with deviations equal to or lower than a tenth of millimeter.

The upper side wall of the proximal portion 13 further has an aperture or inlet hole 6, particularly a through hole of a size corresponding to the laser beam 101 generated from the welding head 100. This inlet aperture 6 is vertically aligned above the orifice 5, such that the laser beam 101 , aligned according to the vertical through axis y, passes through this inlet opening 6 and achieves the underlying welding surface through the nozzle orifice 5. Due to the above-mentioned configuration, the main nozzle 4 opens at the interaction point between of the laser beam 101 and surface of the material to be welded, i.e. where the melted pond is being created, thereby immediately preventing any phenomena of atmospheric contamination.

The intermediate portion 14 of the main nozzle 4 is structured as a cylindrical- section tube, with an outer diameter corresponding to that of the seat 1 1 for the latter to be accommodated therein.

Near the distal end thereof, the intermediate portion laterally has a coupling 16 arranged to be associated with a distribution system of the assisting gas. At said coupling 16, on the side wall of the internal channel opens an inlet 9 through which the assisting gas is introduced into the internal channel 7 of the main nozzle 4.

Finally, the distal portion 15 of the_ main nozzle 4 consists of a bushing fitted at the free end of the intermediate portion 14. The distal end 9 of the bushing is arranged for inserting a capture component of a process optoelectronic monitoring system, particularly an optical fibre connector. The optical fibre connector allows capturing optical information related to the welding process, through the window formed by the nozzle orifice 5. The internal channel 7 thus performs the double function of an assisting gas distributor and an optical collimator.

As mentioned above, the secondary nozzles 4' completing the train of nozzles are substantially equal to the main nozzle, except that the inlet opening 6 is not provided.

It should be also noted that, in an alternative embodiment of the invention, the secondary nozzles 4' can also be provided with this opening in order to allow for a complete interchangeability of the components.

For a description of the structure of the secondary nozzles 4' reference should be thus made to the above description of the main nozzle 4.

It is desired, however, to briefly look more closely at the relative arrangement of the orifices 5' of the secondary nozzles 4'. As can be seen in the attached figures la, lb, the nozzles 5, 5' are aligned such that the orifices 5' of the secondary nozzles 4' lay on the same plan as and are aligned and contiguous relative to the orifice 5 of the main nozzle 4. In other words, the rectangular sections of the orifices 5, 5' of the nozzles are subsequently placed side by side such that the short side of a section results to be adjacent to the short side of the following section.

It is also noted that that each of the different secondary nozzle 4' provides the opportunity of being independently interfaced to the optoelectronic monitoring system, in order to check the subsequent areas of the seam downstream of the thermal beam.

Each secondary nozzle 4' is then independently coupled to one or more assisting gas distribution systems. A main advantage of the present invention results from the even and complete covering of the welding seam, which also involves the interaction area of the thermal .team and the surface to be welded and does not. provide the discontinuities deriving from placing circular- section nozzles side by side to each other. Another advantage derives from the opportunity of an effective monitoring of the process, due to the fact that the different nozzles can be used as focusers for an optoelectronic monitoring system. Due to their positioning, - l i the nozzles ensure vision both of the welding process and evolutions of the seam after it is being formed. Particularly, the visual access directed to the melted pond provided by the main nozzle paves the way to a much more refined process control than the prior art embodiments. Said monitoring can be both centred on the thermics and identification of specific defects (cracks, porosity); by disposing of more channels, the more suitable type of monitoring for each single area can be selected.

A further advantage of the present finding is the modularity of the device, which uses a plurality of nozzles that are interchangeable and independent from each other. Thereby, the train of nozzle can be either made longer or shorter according to the welding requirements.

Furthermore, due to the separate supply of the several channels, different flow rates or even types of gases can be selected for each different area of the process. The modularity of the device further allows an easy replacement of any damaged nozzles; the monitoring system can be designed with a plug and play logic, such as to be easily disconnected from the damaged nozzles and reconnected to the replacing nozzles.

Finally, a further advantage of the present invention results from the very low manufacturing costs, being the various parts easy and cost-effective to be worked.

Obviously, those skilled in the art, aiming at meeting contingent and specific requirements, can carry out a number of modifications and variations to the above-described invention, which are all included in the scope of protection of the invention such as defined by the following claims.

Claims

1. Device ( 1) for covering welds with an assisting gas, comprising: a coupling portion (2) suitable for connecting the device ( 1) to a welding head ( 100); and a delivering portion (3) comprising at least a main nozzle

5 (4), oriented along a main axis (x), having at least an inlet (9) for an assisting gas and an aperture (5) for blowing the assisting gas at a welding area; said main nozzle (4) defining an internal channel (7) for passage of the assisting gas, extending along the main axis (x) and opening on the aperture (5) of the main nozzle (4); said main nozzle (4) further featuring

10 an inlet opening (6), said inlet opening (6) and said aperture (5) being traversed by a through axis (y) inclined with respect to the main axis (x) of the main nozzle (4), the main nozzle (4) being arranged for allowing passage of a thermal beam, coming from the welding head ( 100) and oriented along said through axis (y), passing through said inlet opening (6)

15 and said aperture (5); characterized in that the at least one inlet (9) for the assisting gas laterally opens on the internal channel (7) with respect to the main axis (x); and in that a distal end (8) of the internal channel (7), opposed to the aperture (5) of the main nozzle (4), is open so as to allow the insertion of a component of an optoelectronic control system, so that

20 said internal channel (7) is integratable in an optoelectronic control system for capturing, through the internal channel (7) and the aperture (5), optical data relating to the welding area.

2. Device ( 1) according to claim 1 , wherein said delivering portion (3) comprises one or more auxiliary nozzles (4 also featuring an aperture (5')

25 for an assisting gas, the main nozzle (4) and the auxiliary nozzles (4^ defining a set of nozzles adjacent to each other, the apertures (5, 5^ of the main nozzle (4) and of the auxiliary nozzles (4^ being aligned and arranged to cover a welding seam.

_ .

3, . Device ( 1) according to claim 2, wherein the apertures (5. 5^ of said.

30 main (4) and auxiliary (4^ nozzles feature a cross-section having at least two substantially straight sides, the cross-sections of the adjacent apertures (5, 5^ featuring the corresponding straight sides next to each other.

4. Device ( 1) according to claim 3, wherein the apertures (5, 5^ of the nozzles (4, 4^ feature identical polygonal cross-sections placed side-by- side so as to define an overall profile without discontinuities.

5. Device (1) according to one of claims 2-4, wherein the auxiliary nozzles (4^*) are singly and releasably mounted on the delivering portion (3), so that the length of the set of nozzles can be modified by varying the number of said auxiliary nozzles (4').

6. Device (1) according to claim 5, wherein said delivering portion (3) comprises a support arm (10) featuring a plurality of parallel transverse seats (1 1) adjacent to each other, into which one or more among the auxiliary nozzles (4^ and the main nozzle (4) can be releasably mounted.

7. Welding machine comprising a welding head (100) to which a device (1) for covering welds with an assisting gas according to one of the preceding claims is connected, wherein said welding head (100) is oriented along the through axis (y).