Abstract
In a method and a carrier gas nozzle for allowing at least one fluid to flow over a welding area of a workpiece along a welding path during a welding process, the at least one fluid is flowed onto the welding area via at least one inlet and channels having openings. The openings of the channels are divided into at least two sectors, and at least one flow parameter, if need be also a property of the at least one fluid of each sector, is individually controlled, wherein at least one flow parameter of at least one fluid of at least one sector is controlled depending on the geometry of the welding path and/or depending on the geometry of the workpiece.
Claims
1. A method for allowing at least one fluid to flow over a welding area of a workpiece along a welding path during a welding process, the method comprising: flowing the at least one fluid onto the welding area via at least one inlet and a plurality of channels having openings, wherein the openings of the channels are divided into at least two sectors, and individually controlling at least one flow parameter of the at least one fluid of each sector, wherein at least one flow parameter of at least one fluid of at least one sector is controlled depending on the geometry of the welding path and/or depending on the geometry of the workpiece.
2. The method according to claim 1, wherein at least one property of the at least one fluid is individually controlled.
3. The method according to claim 1, wherein at least one flow parameter and/or at least one property of the at least one fluid of each sector is individually controlled depending on at least one temperature of the welding area of the workpiece.
4. The method according to claim 3, wherein the at least one temperature of the welding area of the workpiece is measured with at least one temperature sensor, is estimated by simulation or parameter calculation, and/or is determined via the energy introduced into the workpiece during the welding process.
5. The method according to claim 3, wherein when the temperature falls below or exceeds a predetermined limit temperature, at least one flow parameter and/or at least one property of the at least one fluid of at least one sector is changed.
6. The method according to claim 3, wherein at least one flow parameter and/or at least one property of the at least one fluid of each sector is individually controlled depending on a predetermined temperature-time cooling profile of the workpiece.
7. The method according to claim 2, wherein at least one property of at least one fluid of at least one sector is controlled depending on the geometry of the welding path and/or depending on the geometry of the workpiece.
8. The method according to claim 1, wherein at least one flow parameter and/or at least one property of at least one fluid of at least one sector is controlled depending on the welding process.
9. A carrier gas nozzle for allowing at least one fluid to flow over a welding area of a workpiece along a welding path during a welding process, the carrier gas nozzle (1) comprising: a housing, at least one inlet for the at least one fluid and a plurality of channels having openings through which the at least one fluid flows onto the welding area, wherein the channels with the openings are divided into at least two sectors, with at least one inlet for at least one fluid, which sectors are designed for the individual control of at least one flow parameter of the at least one fluid of each sector, wherein the at least two sectors are arranged depending on the geometry of the welding path and/or the geometry of the workpiece, wherein in each sector its own valves or its own flow controllers for the at least one fluid are provided, and wherein a control is provided with which the control of the at least one flow parameter of the at least one fluid of each sector can be carried out by the sector-by-sector control by means of the valves or the flow controllers, so that at least one flow parameter of at least one fluid of at least one sector can be controlled depending on the geometry of the welding path and/or depending on the geometry of the workpiece.
10. The carrier gas nozzle according to claim 9, wherein the sectors are constructed in the form of interconnectable modules.
11. The carrier gas nozzle according to claim 9, wherein at least one temperature sensor is provided for measuring at least one temperature of the welding area of the workpiece.
12. The carrier gas nozzle according to claim 9, wherein the housing, the at least one inlet for each fluid, the channels with the openings, and at most the at least one cooling fluid line are produced in one piece and preferably in a 3D printing process.
13. The carrier gas nozzle according to claim 9, wherein the channels have a round or regularly polygonal cross-section.
Description
(1) The present invention is further explained with reference to the appended drawings. In the drawings:
(2) FIG. 1 is a perspective view of an embodiment of a substantially rectangular carrier gas nozzle;
(3) FIG. 2 is a perspective view of the carrier gas nozzle according to FIG. 1 from below;
(4) FIG. 3 is a section through a module of a carrier gas nozzle;
(5) FIG. 4 is a schematic perspective view of a rectangular carrier gas nozzle with three rectangular sectors;
(6) FIG. 5 is a sectional view through the carrier gas nozzle according to FIG. 4 along the sectional plane VI;
(7) FIG. 6 is the flow profile of the fluid of the carrier gas nozzle according to FIG. 5;
(8) FIG. 7 is a top view of a rectangular carrier gas nozzle with six symmetrically arranged rectangular sectors;
(9) FIG. 8 is a top view of a rectangular carrier gas nozzle with three asymmetrically arranged rectangular sectors;
(10) FIG. 9 is a top view of a rectangular carrier gas nozzle with two symmetrically arranged rectangular sectors;
(11) FIG. 10 is a schematic view of a carrier gas nozzle with six sectors according to FIG. 7, wherein the flow parameters of the fluid of each sector are controlled depending on the geometry of the curved welding path;
(12) FIG. 11 is a schematic view of a carrier gas nozzle with six sectors according to FIG. 7, wherein the flow parameters of the fluid of each sector are controlled depending on the geometry of the straight welding path;
(13) FIG. 12 is a schematic view of a carrier gas nozzle with two sectors according to FIG. 9, wherein the flow parameters of the fluid of the sectors are controlled depending on the geometry of the welding path;
(14) FIG. 13 is a top view of a round carrier gas nozzle having a plurality of sectors modularly constructed and interconnected;
(15) FIG. 14 is an illustrative temperature-time cooling curve for a workpiece during a welding process and appropriate control of the fluid parameters or properties of the fluid of the carrier gas nozzle; and
(16) FIGS. 15A to 15C are further illustrative temperature-time cooling curves for a workpiece during a welding process with three different courses of cooling.
(17) FIG. 1 shows a perspective view of a preferred embodiment of a substantially rectangular carrier gas nozzle 1 for flowing at least one fluid F.sub.i, in particular a protective gas or a cooling liquid or mixtures of a gas and a liquid, along a welding path X through a welding area Y of a workpiece W. The carrier gas nozzle 1 comprises a housing 2 and, at most, a device for fastening to a welding torch B. In order to carry out a rapid adjustment of the carrier gas nozzle 1 with respect to the welding torch B, the device can also be designed to be pivotable in order to be able to bring the carrier gas nozzle 1 out of the position of use (not shown). As a result, the process stability can be assessed, for example, in a welding start phase for quality control. During the welding process, the trailing welding area Y is covered by the carrier gas nozzle 1, as a result of which the welding area Y is protected from air ingress and cooled in order to be able to achieve an optimal quality of the weld seam or the welding surface. The length of the carrier gas nozzle 1 is selected in such a way that, at the desired welding speed v, it is ensured that the at least one fluid F.sub.i flows through the welding area Y until the critical temperature T.sub.k of the workpiece W in the welding area Y, at which a reaction with atmospheric oxygen takes place, is undershot. The depicted carrier gas nozzle 1 has a jacket 3 around the gas nozzle 4 of the welding torch B, via which the primary protective gas is supplied to protect the arc during the welding process (see also FIG. 2). Arranged on the jacket 3 is a module M.sub.1 for forming a first sector S.sub.1, which in turn is connected to three further modules M.sub.2, M.sub.3, M.sub.4 for forming sectors S.sub.1, S.sub.3 and S.sub.4. The connection between the modules M.sub.j can be embodied, for example, by a releasable connection, that is, by a screw connection, latching, or also by a non-releasable connection, such as welding, soldering, gluing, or the like. The carrier gas nozzle 1 can be expanded in a modular manner in order to achieve a shape of the carrier gas nozzle 1 calculated, for example, by simulation or parameter calculation (see also FIGS. 10 to 12). Instead of the interconnected modules M.sub.1 to M.sub.4, the housing 2 of the carrier gas nozzle 1 can also be produced in one piece, and sectors S.sub.1 to S.sub.4 can also be integrated in this common housing 2. The carrier gas nozzle 1 has at least one inlet E.sub.i for the at least one fluid F.sub.i, here in each case one inlet E.sub.1 to E.sub.4 in each module M.sub.1 to M.sub.4 for in each case one fluid F.sub.1 to F.sub.4. Via a plurality of preferably parallel channels 6 having openings 7, the at least one fluid F.sub.i with corresponding flow parameters P.sub.i and properties Q.sub.i flows onto the welding area Y (see FIG. 3). Instead of a substantially rectangular shape of the carrier gas nozzle 1 in top view, round or other shapes are also possible. In the modules M.sub.1 to M.sub.4, the carrier gas nozzle 1 can also contain cooling fluid lines 9, via which, in addition to the at least one fluid F.sub.i, a cooling fluid K can also be applied to the welding area Y.
(18) As already mentioned, the carrier gas nozzle 1 can be embodied in one piece and can preferably be produced in a 3D printing process. For example, a laser sintering process is suitable for this, in which the material, in particular an aluminium alloy, is in powder form and is melted by a laser. In this way, the carrier gas nozzle 1 according to the invention can be produced particularly cost-effectively, and the geometry of the individual elements can be easily adapted as a result. All elements of the carrier gas nozzle 1, such as the housing 2, the at least one inlet E.sub.i for the at least one fluid F.sub.i, the channels 6, and possibly a cooling fluid channel 9, are produced in one operation.
(19) FIG. 2 shows a perspective view of the carrier gas nozzle 1 according to FIG. 1 from below. In this case, the channels 6 with the openings 7 in sectors S.sub.1 to S.sub.4 can be seen, which here have a square cross section. The ratio of the height of the channel 6 to the hydraulic diameter is preferably selected so that the flow within the channels 6 is accordingly stilled and a uniform, laminar flow of the fluid F.sub.i results at the openings 7 of the channels 6. The size of the carrier gas nozzle 1 and also the number n.sub.i of channels 6 in each sector S.sub.i are selected according to the respective application.
(20) In the illustrated exemplary embodiment of the carrier gas nozzle 1 according to FIGS. 1 and 2, the openings 7 of all channels 6 are arranged in one plane, which is particularly suitable for use on a substantially planar workpiece W. Alternatively, the openings 7 of the channels 6 may also be arranged on a curved surface. As a result, the shape of the carrier gas nozzle 1 can be adapted to the shape of the workpiece W. For example, when welding a pipe, the carrier gas nozzle 1 may be concavely or convexly curved in order to be able to achieve an adaptation to the outer or inner surface of the pipe (not shown). As a result, the welding area Y is optimally protected by the fluid F.sub.i, and an optimal welding quality is achieved even with oxidation-sensitive materials, such as titanium in particular.
(21) FIG. 3 shows a section through a module M.sub.j of a carrier gas nozzle 1. This shows the connection of the inlet E.sub.i for the fluid F.sub.i into a distribution chamber 15. In order to be able to optimally distribute the fluid F.sub.i flowing in from the inlet E.sub.i in the gas distribution chamber 10, an element 11 for distributing the fluid F.sub.i can additionally be arranged in the gas distribution chamber 10. Holes 12 lead from the distribution chamber 15 into the parallel channels 6. The distribution of the fluid F.sub.i can also take place in several stages, in that the fluid F.sub.i passes via the inlet E.sub.i into a first distribution chamber 10 and is passed via corresponding holes 12 into a second distribution chamber or several second gas distribution chambers, before the fluid F.sub.i is distributed via corresponding holes to all channels 6 (not shown). Such cascading results in an optimal and uniform distribution of the fluid F.sub.i to all channels 6 and thus a uniform flow through the openings 7 to the welding area Y of the workpiece W to be protected and cooled.
(22) FIG. 4 shows a schematic perspective view of a rectangular carrier gas nozzle 1 and the underlying workpiece W, the welding area Y of which is flowed with at least one fluid F.sub.i. In the illustrated carrier gas nozzle 1, the openings 7 of the channels 6 for the fluid F.sub.i are divided into three rectangular sectors S.sub.1, S.sub.2 and S.sub.3. The number n.sub.i of channels 6 per sector S.sub.1 can be the same or different. According to the invention, at least one flow parameter P.sub.i of the at least one fluid F.sub.i of each sector S.sub.1, S.sub.2 and S.sub.3 can be controlled individually. The welding process proceeds in the direction of the longitudinal extension of the workpiece W, which is indicated by the arrow of the welding speed v.
(23) FIG. 5 shows a sectional view through the carrier gas nozzle 1 according to FIG. 4 with the three sectors S.sub.1, S.sub.2 and S.sub.3 along the sectional plane VI-VI, and underneath in FIG. 6 the flow profile of the fluid F.sub.i of the carrier gas nozzle 1 according to FIG. 5. The flow profile shows a flow parameter P.sub.i of the fluid F.sub.i, here the flow rate v.sub.Fi of the fluid F.sub.i in the transverse direction along the y-axis. In accordance with the configuration of the carrier gas nozzle 1 according to the invention, the flow parameter P.sub.i, here the flow rate v.sub.Fi of the fluid F.sub.1, F.sub.2, F.sub.3 used in each sector S.sub.1, S.sub.2 and S.sub.3, is controlled individually. Sectors S.sub.1, S.sub.2, and S.sub.3 can, of course, be individually configured in different ways. For example, sector S.sub.1 may be configured with a diffuser as in FIG. 3, since a particularly laminar flow is desired here in order to prevent oxidation on the workpiece W. Sectors S.sub.2 and S.sub.3, for example, are only used for cooling and therefore do not need a diffuser, since the temperature there is cooled to such an extent that oxidation no longer takes place. Thus, sectors S.sub.2, S.sub.3 can be produced in a geometrically simpler and thus more cost-effective manner. Here, the flow rate v.sub.F1 of the fluid F.sub.1 in first sector S.sub.1 is selected to be higher than the flow rates v.sub.F2, v.sub.F3 of the fluids F.sub.2, F.sub.3 of sectors S.sub.2 and S.sub.3, which are further away from the welding area Y to be protected and cooled along the welding path X than sector S.sub.1. The flow parameters P.sub.i of the fluids F.sub.i can be controlled by separate inlets E.sub.1, E.sub.2, E.sub.3 for the fluids F.sub.i, F.sub.2 and F.sub.3 of each sector S.sub.1, S.sub.2 and S.sub.3. In this case, the type of fluid F.sub.i of each sector S.sub.1 could also be changed individually and, for example, a different fluid F.sub.i could be used for sector S.sub.1 than for sectors S.sub.2 and S.sub.3 or a different composition of the fluids F.sub.2 and F.sub.3. Likewise, the carrier gas nozzle 1 may be designed so that it has only one inlet E for a fluid F and the inlet is divided between sectors S.sub.1, S.sub.2 and S.sub.3. If each sector S.sub.1, S.sub.2 and S.sub.3 now has its own valve or its own flow controller (not shown) for the fluid F, the flow parameter P.sub.i of the fluid F in each sector S.sub.1, S.sub.2 and S.sub.3 can be controlled individually. The method according to the invention for applying a fluid F.sub.i to a welding area Y of a workpiece W and the design of the carrier gas nozzle 1 according to the invention enable individual control of the fluids F.sub.i used, whereby the consumption of the fluids F.sub.i used and thus the costs can be minimised with optimal quality of the resulting welding result.
(24) FIG. 7 shows a top view of a rectangular carrier gas nozzle 1 with six symmetrically arranged rectangular sectors S.sub.1 to S.sub.6. The inlet E for the fluid F or several inlets E for the fluids F.sub.i are not shown. The welding torch B is arranged in the centre of the symmetrically constructed carrier gas nozzle 1. Assuming regularly arranged channels 6 in the carrier gas nozzle 1 shown here, the number n.sub.3 and n.sub.4 of channels 6 of sectors S.sub.3 and S.sub.4 is less than the number n.sub.1, n.sub.2, n.sub.3 and n.sub.2 of channels 6 of sectors S.sub.1, S.sub.2, S.sub.5 and S.sub.6. The respective design of the carrier gas nozzle 1 and division of the sectors S.sub.1 is optimally adapted to the workpiece W to be produced. There are hardly any limits to the design options.
(25) FIG. 8 shows the top view of a rectangular carrier gas nozzle 1 with three asymmetrically arranged rectangular sectors S.sub.1, S.sub.2 and S.sub.3. Such a configuration will be expedient if the carrier gas nozzle 1 or the welding torch B is generally moved over the workpiece W in a preferred welding direction (see arrow of the welding speed v), since the welding area Y covered by the carrier gas nozzle 1 after welding must always be flowed with the fluid F.sub.i and protected and cooled.
(26) FIG. 9 shows a top view of a rectangular carrier gas nozzle 1 with two symmetrically arranged rectangular sectors S.sub.1 and S.sub.2, each with a corresponding number n.sub.1 and n.sub.2 of channels 6. This embodiment variant of the carrier gas nozzle 1 will be expedient in particular for straight welding paths X, which are swept in both directions.
(27) FIG. 10 shows, on the basis of a schematic view of a carrier gas nozzle 1 with six sectors S.sub.1 to S.sub.2 according to FIG. 7, the control of the flow parameters P.sub.i of the fluid F.sub.i of the sectors S.sub.i depending on the geometry of a curved welding path X. When the carrier gas nozzle 1 moves during the welding process along the welding path X in the direction of the arrow of the welding speed v, expediently only sectors S.sub.2 and S.sub.4 are actuated, that is to say only the flow of the fluids F.sub.2 and F.sub.4 in sectors S.sub.2 and S.sub.4 is activated, since the freshly welded area is only covered by these two sectors S.sub.2 and S.sub.4 due to the curved shape of the welding path X. As a result, a large amount of fluid F.sub.i, which would otherwise also flow via the other sectors S.sub.1, S.sub.3, S.sub.5 and S.sub.6 to the welding area Y, can be saved.
(28) FIG. 11 shows a schematic view of a carrier gas nozzle 1 with six sectors S.sub.1 to S.sub.2 according to FIG. 7. When the carrier gas nozzle 1 moves during the welding process along the substantially straight welding path X in the direction of the arrow of the welding speed v, only sector S.sub.4 is expediently actuated, that is to say only the flow of the fluid F.sub.4 in sector S.sub.4 is activated, since the freshly welded area is only covered by this sector S.sub.4 due to the straight welding path X.
(29) FIG. 12 shows a schematic view of a carrier gas nozzle 1 with two sectors S.sub.1, S.sub.2 according to FIG. 9 during welding along a straight welding path X. When the carrier gas nozzle 1 moves during the welding process in the direction of the arrow of the welding speed v, only the sector S.sub.1 is expediently actuated, that is to say only the flow of the fluid F.sub.1 in sector S.sub.1 is activated, since the freshly welded area is only covered by this sector S.sub.1 due to the straight welding path X and the welding direction.
(30) FIG. 13 shows a top view of a round carrier gas nozzle 1 having a plurality of sectors S.sub.1 which are constructed in a modular manner and are connected to one another. The individual modules M.sub.j may have different shapes, such as a substantially triangular outline in this case. This enables an individual composition of the carrier gas nozzle 1 from different modules M.sub.j to form the desired sectors S.sub.i.
(31) FIG. 14 shows an exemplary temperature-time cooling curve in which the temperature T (in C.) at a stationary location on the workpiece W during the welding process during which the welding torch B is moved with the carrier gas nozzle 1 at the welding speed v over the workpiece W is shown depending on the time t (in s). At the beginning of the welding process during phase I, the temperature T is arranged below the critical temperature T.sub.k relevant for an oxidation. In this phase I, the welding area is cooled, for example, only with compressed air. Thus, during phase I, compressed air is used as fluid F.sub.i in the corresponding sector S.sub.i of the carrier gas nozzle 1, which is located just above the point at which the temperature T is measured. During phase II, the temperature T rises above the critical temperature T.sub.k, which is why carbon dioxide CO.sub.2, for example, is used as the fluid for the sector S.sub.i, which is located above the point where the temperature T is measured. If the temperature T rises above the so-called dissociation temperature T.sub.diss, an inert gas, e.g. argon, is added during phase III in order to protect the molten mass from oxidation during the welding process. After the temperature has fallen below the dissociation temperature T.sub.diss during phase IV, the cheaper carbon dioxide CO.sub.2, for example, can be used again instead of argon. If the temperature falls below a certain limit temperature T.sub.G, a liquid, for example water, is additionally used to cool the workpiece more quickly (phase V). If the measured temperature T finally falls below the critical temperature T.sub.k, the workpiece W can again be flowed exclusively with compressed air (phase VI). FIG. 14 shows only the control of the type of fluid F.sub.i of the sectors S.sub.i of the carrier gas nozzle 1 depending on the temperature T measured at one point. When several temperature sensors are arranged, the properties Q.sub.i or flow parameters P.sub.i of the fluids F.sub.i for the sectors S.sub.i, which are located just above the point of the respective temperature sensor, can be adapted to the respective measured temperature T or the temperature profiles can be adjusted and changed by changing the properties Q.sub.i or flow parameters P.sub.i of the fluids F.sub.i for the sectors S.sub.i. Thus, the temperature-time cooling profile can also be adapted to the geometry of the workpiece W. For example, the workpiece W may have less material at the edge, so that the heat input during the welding process is lower and thus the cooling after the welding process must also be lower, while a higher cooling capacity will be required in the centre of the workpiece W.
(32) Finally, FIGS. 15A to 15C show further exemplary temperature-time cooling curves for a workpiece W during a welding process with three different cooling curves from phase IV onwards after falling below the dissociation temperature T.sub.diss.
(33) According to FIG. 15A, after cooling the temperature T below the dissociation temperature T.sub.diss in phase IV, very rapid cooling is achieved, for example, by a maximum volume flow of the fluid F.sub.i, for example carbon dioxide CO.sub.2, used in the respective sector S.sub.1 of the carrier gas nozzle 1. The cooling rate is, for example, between 50 C./s and 1000 C./s, preferably between 100 C./s and 500 C./s, depending on the geometry of the workpiece W and the material accumulation during the production process. During phase V, after falling below a limit temperature T.sub.G, a very rapid cooling takes place at the beginning through the use of an additional, external cooling medium in the relevant sector S.sub.i. Over time t, the cooling capacity of the external cooling medium is reduced, which is why the slope of curve 1 becomes flatter during phase V. In phase VI, after the temperature T drops below the critical temperature T.sub.k, the cooling is influenced, for example, by controlling the volume flow of an additional cooling gas, such as, for example, air.
(34) In FIG. 15B, the cooling in phase IV is lower than the temperature profile according to FIG. 15A due to a lower volume flow of a protective gas in the respective sector S.sub.i. Thus, the duration of phase IV is greater than in FIG. 15A. In phase V, for example, a substantially constant drop in temperature T takes place by the constant addition of an external cooling medium in the respective sector S.sub.i. In phase VI, for example, cooling is again influenced by the control of the volumetric flow of air.
(35) FIG. 15C shows a temperature-time profile in which, in phase IV, the cooling takes place in a slowed manner by reducing the volume flow of the protective gas in the respective sector S.sub.i. As a result, the phase IV is substantially longer than in the courses according to FIGS. 15A and 15B. After falling below the dissociation temperature T.sub.diss in phase V, according to FIG. 15C, cooling takes place with increasing drop by increasing the cooling capacity by an external cooling medium in the respective sector S.sub.i. After falling below the critical temperature T.sub.k in phase VI, the cooling is again influenced by controlling the volume flow of an additional cooling gas, for example air. FIGS. 15A to 15C show various possibilities of influencing the temperature-time cooling profile of the workpiece W by different flow parameters P.sub.i or properties Q.sub.i of the fluids F.sub.i used in the respective sector S.sub.i of the carrier gas nozzle 1.
(36) The present invention allows the amount of fluids F.sub.i used to be minimised and the welding quality to be optimised.
