Welding machine for longitudinal metal objects, such as billets

Abstract

To provide a welding machine of a flash welding type, intended to weld together a tail of a first longitudinal metal product with a head of a second longitudinal metal product along an advancement direction.SOLUTION: A machine comprises: a carriage adapted to slide along an advancement direction (X); a first structure (20) with first gripping means (21, 22); a second structure (30), which is slidably supported by said carriage with second gripping means (31, 32); and a power group (40) which can be supplied with mains voltage and is provided with conductors (210), connected to the first gripping means (21, 22) and the second gripping means (31, 32), respectively. The power group (40) comprises: at least one inverter; at least one transformer; at least one rectifier; and a control unit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a welding machine for long metal objects.

[0002] The welding machine according to the present invention is of the flash type and is particularly suitable for processing long metal objects such as billets (steel slabs), bars or blooms.

[0003] In operation, the welding machine is usually arranged upstream of the rolling mill and welds the tips and ends of two consecutive long products along a conveying line, particularly a roller line.

Background Art

[0004] Generally, in a rolling mill, individual metal products directly sent from a casting device or a storage warehouse are welded so that they can be continuously rolled.

[0005] Such metal products are typically unfinished iron-based products such as billets, bars, blooms, etc.

[0006] Welding is performed to join the end of a product to the tip of the next product.

[0007] Generally, welding is performed by a technique known as flash welding, i.e., by a discharge generated by a power source connected to the product to be welded.

[0008] More specifically, a controlled current flows through two surfaces of the metal product to be welded. This current generates energy and brings the two surfaces to the melting temperature ("flashing" step). When the two surfaces are completely melted, the current is stopped and they are fused (made into an amalgam) until they are completely joined ("upsetting" step).

[0009] Therefore, during welding, it is necessary to firmly fix the product. For such a purpose, the welding machine is equipped with gripping means for holding the product in a predetermined position during welding. Usually, the gripping means also operates as a conductor of the welding current.

[0010] Generally, such gripping means typically consists of clamps that directly contact the product to be welded. When welding is performed, the clamps that hold the tip and the end of the product to be welded are brought closer to each other by a hydraulic cylinder or an electric cylinder called an upset cylinder. This operation joins the ends to be welded, removes inclusions and air bubbles, compensates for the material loss caused by melting, and enables the actual adhesion between the two parts to be welded.

[0011] A known type of flash welding machine consists of a carriage that is movable along a track arranged on a segment of the conveying line of a long metal object. This machine further consists of two separate structures mounted on the carriage, each having a pair of clamps. Such structures are substantially parallel to each other and are inclined at an angle of approximately 45° with respect to the plane defined by the carriage of the machine.

[0012] A transformer that is connected to the two structures and is provided with conductors for supplying current to the ends and the tips of the two products to be welded by their respective clamps is arranged above the inclined upper surfaces of the two structures. Therefore, it is difficult to access and maintain the inside of the machine, disassemble and remove heavy parts. This is because these operations are carried out by the operator himself getting into the body of the machine.

[0013] The above problems are made more serious by the following facts due to the nature of its operation: the temperature of the billet to be processed is very high and the welding machine is placed in a harsh environment; a large amount of dirt generated by the billet to be processed; the generation of spatter of molten material from the welding process; and the cooling water used to protect the mechanical parts exposed to the structure.

[0014] Furthermore, the space generally provided for the welding machine is very narrow.

[0015] In such a situation, as a possible technical solution, the following requirements cannot be ignored:

[0016] - The most sensitive components must be kept as far as possible from the axis where welding is performed;

[0017] - A more accessible space must be ensured for the conventional lifting devices operating within the machine itself so as to facilitate the maintenance work of normal machines and special machines;

[0018] - The overall size of the welding machine must not be made smaller or at least must not be made larger in order to make its usage space more versatile.

[0019] In this sense, the energy required in the welding process must be considered to be large during the melting step. Therefore, the transformer bank required to supply these energy amounts needs to consider the following characteristics in terms of dimensions and weight:

[0020] - Since it occupies a considerable amount of space, the passage required for the operator to freely access the machine for maintenance work is restricted;

[0021] - A dedicated support structure is required regardless of the location where it is placed;

[0022] - In case of failure, the disassembly and assembly work is assumed to be complicated and time-consuming.

[0023] Furthermore, it should be considered that the transformer bank needs to be placed as close as possible to the welding clamp. The reasons for this are as follows:

[0024] - The welding machine is a movable device and moves several meters in the direction through which the long metal products pass;

[0025] Increasing the distance between the transformer group and the welding clamp will inevitably increase the electrical impedance, which will in turn affect the flow of current required for welding. [Patent Document 1] International Application WO2021 / 156738A1

[0026] The problem of easy access for the operator to the machine is addressed in International Application WO2021 / 156738A1. The proposed solution is to move the transformer from the upper part of the gripping structure to a lateral position, which extends outside the main structure of the carriage itself where the clamp structure is housed and is defined by a cantilevered carriage attachment delimited by two beams parallel to the sliding direction of the long metal product to be welded. Such an arrangement of the transformer allows free access to the upper part of the gripping structure. This facilitates the maintenance of the welding machine (especially the clamp structure) and enables operations using auxiliary devices for moving heavy objects such as a crane or an overhead crane.

[0027] However, the solution described in International Application WO2021 / 156738A1 has the drawback that the planar dimensions of the welding machine increase, resulting in an increase in the overall size.

[0028] Therefore, the problem of the need to improve the accessibility to the welding machine without significantly increasing the size remains unsolved. [Summary of the Invention]

[0029] Therefore, an object of one invention of the present application is to provide a welding machine for long metal objects that exhibits improved accessibility without requiring a significant increase in size, thereby eliminating all or part of the drawbacks of the aforementioned prior art.

[0030] A further object of the present invention is to provide a welding machine for long metal objects that maintains sufficient operating functions.

[0031] A further object of the present invention is to provide a welding apparatus for long metal objects that is easy to manage and inexpensive.

[0032] A further object of the present invention is to provide a welding machine for long metal objects that does not have a significantly higher assembly cost than similar known machines. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The technical features of the present invention according to the foregoing objects can be clearly found in the content of the claims of this application, and the advantages thereof will become more apparent from the following detailed description given with reference to the accompanying drawings showing one or more embodiments given as non-limiting examples.

[0034] FIG. 1 is a perspective view of a welding machine for long metal objects according to a preferred embodiment of the present invention, seen from above.

[0035] FIG. 2 is an orthogonal elevation view of the welding machine seen in the direction of arrow II shown in FIG. 1.

[0036] FIG. 3 is a plan view of the welding machine of FIG. 1 seen from above.

[0037] FIG. 4 is a perspective view of a component of the welding machine for long metal objects of FIG. 1, relating to a carriage for moving the machine.

[0038] FIG. 5 is a perspective view of a component of the welding machine for long metal objects of FIG. 1, relating to the main body of the machine.

[0039] FIG. 6 is a simplified wiring diagram of a power supply group of the welding machine according to a preferred embodiment of the present invention, composed of an inverter mounted on a carriage.

[0040] FIG. 7 is a simplified wiring diagram of a power supply group of the welding machine according to a preferred embodiment of the present invention, composed of an inverter arranged outside the carriage.

[0041] FIG. 8 is a simplified wiring diagram of a power supply group of a welding machine according to a preferred embodiment of the present invention, which is composed of an inverter mounted on a carriage and a rectifier integrated with a transformer.

[0042] FIG. 9 is a simplified wiring diagram of a power supply group of a welding machine according to a preferred embodiment of the present invention, which is composed of two transformers connected in parallel.

[0043] FIG. 10 is a simplified diagram of a transformer.

[0044] FIG. 11 is a perspective view of a modified example of the carriage of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0045] In the accompanying drawings, the welding machine for a long metal object according to the present invention is generally indicated by reference numeral 1.

[0046] According to a general embodiment of the present invention, the welding machine 1 is of the flash welding type and is suitable for processing long metal objects such as billets (steel pieces), bars or blooms.

[0047] The welding machine 1 is installed upstream of a rolling mill on a conveying line (particularly, a roller line) of a long metal product that moves along the traveling direction X.

[0048] In operation, the welding machine 1 welds the end T of a first long metal product M1 and the tip H of a second long metal product M2 that continuously move along the traveling direction X.

[0049] The welding machine 1 includes a carriage 10, which functions as a base that supports and moves the entire welding machine 1 and slides along the traveling direction X so as to follow the movement of the long metal product in the longitudinal direction.

[0050] According to the attached drawings, particularly the preferred embodiment of the present invention shown in FIG. 4, the carriage 10 includes two beams 11, 12, and these beams 11, 12 are provided with wheels 17 for sliding the carriage 10 parallel to the traveling direction X along the tracks B1, B2 (only a part of which is shown in FIG. 4).

[0051] More specifically, the two beams 11, 12 are laterally connected to each other by at least two connecting beams 13, 14, forming a framework for mounting the remaining part of the welding machine 1.

[0052] The carriage 10 is provided with connected motor means 16 for transmitting motion to the wheels 17. In particular, the motor means consists of an electric gear motor having a pinion-rack type coupling on two tracks B1 and B2.

[0053] According to another embodiment shown in FIG. 11, the carriage 10 can be provided with an appendage 15 that extends outward in a cantilever beam shape in the lateral direction with respect to the traveling direction X in order to accommodate one or more components of the welding machine.

[0054] According to the aforementioned general embodiment of the present invention, the welding machine 1 is supported by the carriage 10 and includes a first structure 20 having a first passage sheet 20a for a long metal product traveling along the conveying line as a part thereof.

[0055] The welding machine 1 also includes a second structure 30 that is slidably supported by the carriage 10 so as to slide parallel to the traveling direction X with respect to both the first structure 20 and the carriage 10 itself.

[0056] Such a second structure 30 has, as a part thereof, a second passage sheet 30a for a long metal product traveling along the conveying line. Such a second passage sheet 30a is aligned with the first passage sheet 20a along the traveling direction X.

[0057] More specifically, as shown in FIG. 5, the two structures 20 and 30 are connected to each other by two support beams 110 and 120 parallel to the traveling direction X. The two support beams 110 and 120 are fixedly fixed to the two beams 11 and 12 of the carriage 10. The first structure 20 is fixedly fixed to the two support beams 110 and 120, and the second structure 30 is slidably connected to the two support beams 110 and 120 by linear guides 111 and 121 so as to slide parallel to the traveling direction X with respect to the first structure 20. The two structures 20 and 30 are connected by one or more actuators 131 and 132 (for example, hydraulic cylinders), thereby enabling relative movement between the two structures in a direction parallel to the axis X in the traveling direction.

[0058] Particularly as seen in FIG. 3, the two structures 20 and 30 are arranged such that there is a gap 2 therebetween.

[0059] In the welding machine 1, the inlet E and the outlet U of the long object can be specified. According to the embodiment shown in the attached drawings, the first structure 20 (fixed) is arranged near the outlet U, and the second structure 30 (movable) is arranged near the inlet E.

[0060] The welding machine 1 further comprises:

[0061] - First gripping means 21 and 22 arranged on the first structure 20 in the first passage sheet 20a for gripping the end portion T of the first metal product M1 or the tip portion H of the second metal product M2;

[0062] - Second gripping means 31 and 32 arranged on the second structure 30 in the second passage sheet 30a for gripping the tip portion H of the second metal product M2 or the end portion T of the first metal product M1.

[0063] In particular, the first gripping means consists of two clamps 21, 22, which are opposed to each other with respect to the first passage sheet 20a, and a long metal object slides between them. More specifically, as shown in FIG. 5, the first clamp 21 (lower clamp) is disposed at the lower part of the first passage sheet 20a, and the second clamp 22 (upper clamp) is disposed at the upper part of the first passage sheet 20a. The two clamps 21, 22 are movable relative to each other and approach and separate to apply a gripping action of approaching and separating from the long object. Preferably, the lower clamp 21 is fixed, and the upper clamp 22 is movable along an axis Z1 at an angle incident to the advancing axis X. For this purpose, the machine 1 includes a first linear actuator 26 (for example, a hydraulic, pneumatic or electric cylinder), which is supported by the first structure 20 and moves the upper clamp 22 along the axis Z1.

[0064] Similarly, the second gripping means also consists of two clamps 31, 32, which are opposed to each other with respect to the second passage sheet 30a, and a long metal object slides between them. More specifically, as shown in FIG. 5, the second clamp 31 (lower clamp) is disposed at the lower part of the first passage sheet 30a, and the second clamp 32 (upper clamp) is disposed at the upper part of the second passage sheet 30a. The two clamps 31, 32 are movable relative to each other and approach and separate to apply a gripping action of approaching and separating from the long object. Preferably, the lower clamp 31 is fixed, and the upper clamp 32 is movable along an axis Z2 at an angle incident to the advancing axis X. For this purpose, the machine 1 includes a second linear actuator 36 (for example, a hydraulic, pneumatic or electric cylinder), which is supported by the second structure 30 and moves the upper clamp 32 along the axis Z2.

[0065] In particular, the first structure 20 and the second structure 30 each extend in a lateral direction with respect to the longitudinal direction which is the advancing direction X, and extend between the respective support members 23 and 24 (arranged opposite to each other in the longitudinal direction) and between the support members 33 and 34 (arranged opposite to each other in the longitudinal direction). Each of the structures 20, 30 is connected to the support beams 110, 120 of the carriage 10 via these support portions 23, 24 and support members 33, 34.

[0066] Preferably, each structure also includes frames 25, 35 which are arranged between the respective support portions 23, 24 and 33, 34 and are configured to accommodate the actuators 26, 36 of the respective gripping means 21, 22 and 31, 32.

[0067] Preferably, the welding machine can be provided with a first guide device 27 and a second guide device 37 at the outlet and the inlet of the welding machine respectively, and can support and guide a longitudinal metal object in the vicinity of the first and second passage sheets of the welding machine 1. In particular, the first guide device 27 is supported by the first structure 20, and the second guide device 37 is supported by the second structure 30.

[0068] In particular, the guide devices 27, 37 are each provided with guide channels 28’, 38’ for guiding, and at least one slide roller 28”, 38” is arranged at the bottom of each of them.

[0069] Preferably, each of the guide devices is movable in the height direction in order to adjust the height for supporting a long metal object passing through the welding machine 1. For this purpose, each of the guide devices 27, 37 is provided with moving means 29, 39 which particularly consist of support guides 29’, 39’ and actuators 29”, 39” (for example, pneumatic or hydraulic cylinders).

[0070] According to a general embodiment, the welding machine 1 further includes a power supply group 40 to which a main voltage can be supplied, and conductors 210; 221, 222 connected to the first gripping means 21, 22 and the second gripping means 31, 32 respectively for supplying current to the terminals and the tips of two long objects.

[0071] Depending on the situation, the conductor can be made rigid or flexible according to whether it should ensure a fixed or variable distance electrical connection.

[0072] The power supply group 40 has the following configuration:

[0073] - At least one inverter 41 that can be mounted on the carriage 10 (see FIG. 6) or installed outside the carriage 10 (see FIG. 7);

[0074] - At least one transformer 42 that is powered by the inverter 41 and is mounted on the carriage 10;

[0075] - At least one rectifier 43 mounted on the carriage that electrically connects the transformer 42 to the first gripping means 21, 22 and the second gripping means 31, 32; and

[0076] - Control unit 50.

[0077] Preferably, as shown in FIGS. 8 and 9, the rectifier 43 is built into the transformer 42.

[0078] Hereinafter, the operation of the welding machine 1 according to the present invention will be described.

[0079] Two long metal objects M1 and M2 (particularly, two billets) slide sequentially through the two passage sheets 20a and 30a of the welding machine 1 in the direction of the travel axis X.

[0080] In particular, the two billets M1 and M2 are arranged while being slidably supported by the two guide devices 27 and 37 in the raised position (preferably, one is arranged at the inlet of the machine and the other is arranged at the outlet) in this step of the welding process, avoiding contact between the billets and the lower clamps 21 and 31 of the first and second gripping means.

[0081] The two billets continue to move until the end T of the first billet M1 and the tip H of the second billet M2 approach the center of the gap 2 existing between the two structures 20 and 30. At this time, the tips and ends of the two billets come into contact with each other.

[0082] At this point, the upper clamp 22 of the first gripping means (supported by the first structure 20 (fixed)) and the upper clamp 32 of the second gripping means (supported by the second structure 30 (movable)) are slid downward along the axes Z1 and Z2 respectively by the operation of their respective linear actuators (hydraulic cylinders 26 and 36), pressing and holding the two billets M1 and M2 against their respective two lower clamps 21 and 31.

[0083] Preferably, simultaneously with the movement of the upper clamps, the guide devices 27 and 37 are moved to the lowered position by the operation of their respective actuators 29” and 39” so as not to interfere with the holding of the billets between the upper and lower clamps.

[0084] In this step, the carriage 10 supporting the entire machine is linearly moved parallel to the advancing axis X of the billets.

[0085] Next, the flash step is started.

[0086] During the flash step, current flows between the two faces of the two billets. This is because at least one transformer 42 is physically connected to all of the four clamps 21, 22 and 31, 32 via the secondary circuit conductors 210, 221, 222. The aforementioned secondary conductors are designed to share the positive pole of the electrical circuit at both clamps (upper and lower) of one structure and the negative pole at both clamps of the other structure.

[0087] The upset step then follows.

[0088] When melting reaches the planned level on the two billet surfaces, the current flow is stopped. A movable structure (second structure 30) supported by two linear guides arranged parallel to the axis X is moved by two hydraulic cylinders 131, 132 fixed to a fixed structure (first structure 20).

[0089] Preferably, as shown in FIG. 2, the line connecting the central points of the axes of the two hydraulic cylinders 131 and 132 intersects the axis X and is aligned on an axis Y that is inclined by approximately 65° from the perpendicular to the axis X. The two cylinders are equidistant from the axis X. When the movable structure 30 moves parallel to the axis X in the direction of the fixed structure 20, pressure is generated between the two surfaces of the two billets, ensuring their joining.

[0090] When the upsetting step is completed, the two upper clamps 22 and 32 are returned to their initial positions. At the same time, the two guide devices 27 and 37 rise and lift the billets that were in contact with the two lower clamps 21 and 31. The moving means 16 of the carriage 10 reverses the moving direction, returns the welding machine to a preset starting position, and waits for a new welding cycle. While the carriage is being returned to the starting position, both hydraulic cylinders 131 and 132 simultaneously push the movable structure 30 back to its initial position away from the fixed structure 20.

[0091] According to a first aspect of the present invention, the inverter 41 is a single-phase or poly-phase inverter with a variable frequency, and the control unit 50 is programmed to operate the inverter 41 at a frequency exceeding 700 Hz.

[0092] At least one transformer 42 has a size that supplies a predetermined nominal power Pn at a predetermined nominal supply frequency fn.

[0093] According to a further aspect of the present invention, after determining the operating power Pex to be generated during welding, two options are possible regarding the sizing characteristics of the transformer 42.

[0094] According to the first option, the predetermined nominal power Pn of the transformer 42 is lower than the predetermined operating power Pex, and the nominal supply frequency fn is lower than 700 Hz. At least one transformer 42 is sized to supply an actual power Pe equal to or greater than the predetermined operating power Pex at frequencies above 700 Hz.

[0095] According to the second option, the predetermined nominal power Pn of the transformer 42 is at least equal to the predetermined operating power Pex, and the nominal supply frequency fn is 700 Hz or higher. At least one transformer 42 is sized to supply an actual power Pe greater than the predetermined operating power Pex at frequencies above 700 Hz.

[0096] In either case, by using frequencies above 700 Hz, the energy requirements for performing welding with a transformer 42 of small dimensions and low weight can be met as compared to the systems known to date for flash welding long metallic products, and the operating power Pex supplied for welding is the same.

[0097] According to the present invention, the welding machine 1 that determines the operating power Pex can operate using a small and low-weight transformer. In particular, since the size of the transformer is small, the space occupied by such a transformer is reduced, and as a result, a large free space for ensuring the accessibility of the operator to the welding machine is secured.

[0098] According to the present invention, the welding machine 1 exhibits improved accessibility without requiring a significant increase in size.

[0099] According to the present invention, a welding machine for long metallic objects also does not have a significantly higher construction cost than similar known machines.

[0100] According to the first option described above, the transformer 42 (sized to supply a nominal power Pn smaller than Pex at a nominal frequency fn smaller than 700 Hz) can be made to act so as to supply a power equal to or greater than Pex by operating at a frequency exceeding the nominal frequency fn. Therefore, the power demand for welding is satisfied by using a smaller transformer. However, such a mode has the drawback of increasing the losses of the transformer and being inefficient.

[0101] According to the second option described above, the transformer 42 (sized to supply a nominal power Pn equal to or at least equal to Pex at a nominal frequency fn greater than 700 Hz) can supply the required power by operating at the nominal frequency fn or can be made to act so as to supply a power greater than Pex by operating at a frequency greater than the nominal frequency fn. Therefore, the power demand for welding is satisfied by using a smaller transformer. Such a mode also has the advantage of minimizing the losses of the transformer and being more efficient when the transformer is operated at the nominal frequency.

[0102] More specifically, referring to FIG. 10, the transformer has a ring (core) made of a ferromagnetic material (typically a thin sheet of silicon steel), on which two windings (a "primary side" consisting of n1 turns and a "secondary side" consisting of n2 turns) are wound. Therefore, this is a double dipole. When a voltage generator v1 ("primary voltage") is supplied to the primary side, a current i1 ("primary current") flows through the primary side, and when the secondary side is open, the current i2 ("secondary current") becomes zero. And a magnetic induction magnetic field is formed in the ring (the "main" magnetic flux φ shown in FIG. 10 corresponds to this). Since the induced electric field lines are also connected to the secondary winding, when i1 changes with time, according to Faraday's law (or the law of electromagnetic induction), a voltage v2 ("secondary voltage") is induced at the secondary terminals. When the secondary side is connected to a load (such as a resistor), current circulates there. Therefore, the transformer can transfer power from the primary winding to the secondary winding without electrically connecting the two windings. That is, energy mainly exists in the core of the transformer, power is transferred through the magnetic field, and energy can be exchanged between both circuits.

[0103] When the magnetic flux of the core is a sine wave, for both windings, the relationship between the effective voltage E, the supply frequency f, the number of turns N, the area a of the core cross-section, and the peak magnetic flux density B is given by the following FEM formula:

Equation

[0104] Assuming that the magnetic flux density B is constant, for the same effective voltage E, as the frequency increases, the cross-sectional area of the core and the number of turns of the winding decrease significantly.

[0105] Similarly, assuming that the magnetic flux density B, the cross-sectional area of the core, and the number of turns of the winding are constant, as the frequency increases, the effective voltage E increases significantly.

[0106] Therefore, the f.e.m. of the transformer at a given magnetic flux intensity increases with frequency. When operating at a higher frequency, the used core can transfer more power without reaching saturation, and the number of turns required to obtain the same impedance decreases, so the transformer becomes physically more compact.

[0107] According to the present invention, the problem of ensuring sufficient accessibility to the welding machine is essentially solved by reducing the size and weight of the transformer, but not (or not necessarily) by changing the arrangement of the transformer itself on the welding machine.

[0108] Preferably, the control unit 50 is programmed such that the inverter 41 operates at a frequency of 700 to 2000 Hz.

[0109] More preferably, the control unit 50 is programmed such that the inverter 41 operates at a frequency between 900 and 1100 Hz, and more frequently at a frequency equal to about 1000 Hz.

[0110] As described above, by utilizing the frequency, a significant reduction in the size and weight of the transformer is achieved in the present invention compared to the conventional systems used for billet welding.

[0111] Since the size of the power group (transformer) is very small, the occupied space is not limited even when it is arranged inside the welding machine. This makes the arrangement of the transformer free, improves the accessibility to the machine, and facilitates maintenance.

[0112] Since the size and weight of the transformer are no longer limiting factors, it is possible to select a position of the transformer as far as possible from the axis where welding is performed. Such a selection can create a space in the machine body where the operation of the lifting means is easy, and at the same time, normal machine maintenance work and special machine maintenance work become easy.

[0113] All of this can be achieved without increasing the overall size of the welding machine.

[0114] Advantageously, according to the present invention, the power group (transformer) can be arranged as close as possible to the welding clamp inside the machine, thus minimizing the length of the conductor connecting to the welding clamp and reducing the electrical impedance generated by the conductor.

[0115] Advantageously, the welding machine can be powered by a commercial power source or a rechargeable system.

[0116] The power group 40 can be composed of a single transformer 42 (as shown in FIGS. 6, 7 and 8) or a plurality of transformers (42a,... 42n) connected in parallel (as shown in FIG. 9).

[0117] Each transformer 42a,... 42n is powered by its dedicated variable frequency inverter 41a,... 41n and is preferably electrically connected to the gripping means 21, 22 and 31, 32 by its dedicated rectifier 43a,... 43n.

[0118] Each of the plurality of transformers is sized to supply a predetermined nominal power Pna,... Pnn at a predetermined nominal power frequency fn.

[0119] The plurality of transformers are sized according to two possible options, similar to the case of a single transformer.

[0120] According to the first option, the sum of the nominal powers Pna,... Pnn of the plurality of transformers is less than a predetermined operating power Pex generated during welding. And the predetermined nominal power frequency fn is less than 700 Hz. The size of the plurality of transformers is such that at frequencies above 700 Hz, it supplies an actual power Pe equal to or greater than the predetermined operating power Pex as a whole.

[0121] According to a second option, the sum of the rated powers Pna,...Pnn of the plurality of transformers is at least equal to a predetermined operating power Pex generated during welding, and the predetermined rated supply frequency fn is greater than 700 Hz. The size of the plurality of transformers is sized as a whole to supply an actual power Pe greater than the predetermined operating power Pex at a frequency exceeding the rated supply frequency fn.

[0122] Preferably, the predetermined operating power Pex has a value between 200 and 2000 kVA.

[0123] Preferably, as a function of the rated power, each of the one or more transformers 42, 42a,...42n has a weight of 150 to 700 kg.

[0124] Preferably, as a function of the rated power, each of the one or more transformers 42, 42a,...42n has the following size:

[0125] - a height of 450 mm to 650 mm;

[0126] - a length of 400 mm to 450 mm; and

[0127] - a depth of 300 mm to 350 mm.

[0128] Operationally, during billet welding, it may be necessary to boost the voltage in the first stage of welding to trigger an arc and generate plasma. Once the arc starts, the voltage is lowered to a steady state and maintained in that state until the second stage of welding is completed.

[0129] Preferably, the power group 40 can constitute a system adapted to provide a boosted voltage during welding.

[0130] More specifically, such a system can be obtained by providing a device for selecting a preset number of turns, called active turns, in the primary circuit of the transformer. Specifically, such a device must reduce the active turns (number of active windings) of the primary side circuit compared to the active turns of the secondary side circuit in order to step up the output of the transformer.

[0131] In fact, as is well known, the ratio of the secondary side circuit voltage (Vs) to the primary side circuit voltage (Vp) is given by the ratio of the number of turns of the secondary side winding (Ns) to the number of turns of the primary side winding (Np):

Equation

[0132] Therefore, in order to increase the voltage, a state where Ns > Np must occur, and such a state occurs when the device selects fewer active turns on the primary side.

[0133] Alternatively, by using a circuit that can change the primary circuit voltage of the transformer, a system that can supply a boosted voltage can be realized. In particular, such a circuit (boost converter) can increase the voltage of the inverter upstream of the transformer, and as a result, the primary side voltage Vp increases. By keeping the turns ratio constant, the increase in the primary side voltage leads to an increase in the secondary side voltage.

[0134] The system provides a boosted voltage that is 1 to 1.8 times the nominal welding voltage.

[0135] The system preferably provides a boosted voltage equal to 1.4 times the nominal welding voltage.

[0136] Preferably, during welding, the power factor of the power grid has a value of 0.92 to 1.

[0137] As already described above, according to the present invention, the problem of ensuring sufficient accessibility to the welding machine is substantially solved by reducing the size and weight of the transformer, rather than (or not necessarily) by changing the arrangement of the transformer itself on the welding machine. In other words, if a single transformer or multiple transformers have a significantly small size and low weight, they can be arranged around the welding machine without being restricted.

[0138] According to the preferred embodiment shown in the attached drawings, at least one transformer 42 or multiple transformers 42a,... 42n can be arranged behind the frames 25, 35 of the two structures 20, 30 with respect to the two passage sheets 20a, 30a. Also preferably, at least one transformer 42 or multiple transformers 42a,... 42n can be arranged on the support parts 24, 34 of the structures 20, 30. In particular, at least one transformer 42 or multiple transformers 42a,... 42n can be arranged on the support part 24 of the fixed structure 20.

[0139] Although not shown in the attached drawings, according to an alternative embodiment, at least one transformer 42 or multiple transformers 42a,... 42n can be arranged on the upper part of the frames 25, 35 of the first structure 20 or the second structure 30. Preferably, it is arranged on the upper part of the frame 25 of the fixed structure 20.

[0140] Although not shown in the attached drawings, according to an alternative embodiment, at least one transformer 42 or multiple transformers 42a,... 42n can be arranged in front of the frames 25, 35 of the two structures 20, 30 with respect to the two passage sheets 20a, 30a. Preferably, at least one transformer 42 or multiple transformers 42a,... 42n are arranged on the support parts 23, 33 of the structures 20, 30. In particular, at least one transformer 42 or multiple transformers 42a,... 42n are arranged on the support part 23 of the fixed structure 20.

[0141] Although not shown in the attached drawings, according to a further alternative embodiment, at least one transformer 42 or a plurality of transformers 42a,... 42n can be arranged outside the frame 25, 35 of one of the two structures 20, 30. Here, the outside of the structure means the wall of the frame of the structure on the side opposite to the wall facing the gap 2 between the two structures 20, 30.

[0142] As already described above, in particular, the carriage 10 consists of a framework arranged transversely to the traveling direction X by two beams 11, 12.

[0143] Preferably, the framework is sized to support the two structures 20 and 30 within its planar size range.

[0144] According to an alternative embodiment shown in FIG. 11, the carriage can include an attachment 15 that extends in a cantilever beam manner outside the framework transversely to the traveling direction X, preferably behind the two frames 25, 35. At least one transformer 42 or a plurality of transformers 42a,... 42n can be arranged on the attachment 15.

[0145] Advantageously, due to the small size and weight of the transformer, the size of the attachment 15 can also be minimized.

[0146] The present invention provides several advantages, some of which have already been described as above.

[0147] The welding machine 1 for long metal objects according to the present invention can achieve improved accessibility without the need for a significant increase in size.

[0148] The welding machine 1 for long metal objects according to the present invention maintains sufficient operating functions.

[0149] The welding machine 1 for long metal objects according to the present invention is easy and convenient to manage.

[0150] The welding machine 1 for long metal objects according to the present invention does not have a significantly higher construction cost compared to similar known machines.

[0151] Therefore, the present invention made in this way achieves the initial objective.

[0152] Obviously, in its actual implementation, it is also possible to take shapes and configurations other than those disclosed above without departing from the scope of the claims.

[0153] Furthermore, all details can be replaced by technically equivalent elements, and any size, shape, and material can be used as required.

Claims

1. A flash welding type welding machine (1) is installed on a conveying line of long metal products moving along a traveling direction (X) for welding an end of a first long metal product and a front end of a second long metal product along the traveling direction (X), the machine comprising: A cart (10) that slides along a traveling direction (X); a first structure (20) supported by the carriage (10) and defining, as a portion thereof, a first aisle seat for the elongated metal products advancing along the conveying line; a first gripping means (21, 22) disposed on the first structure (20) at the first passage seat and configured to grip the terminal end of the first elongated metal product or the terminal end of the second elongated metal product; a second structure (30) slidably supported by the carriage (10), sliding together with both the first structure (20) and the carriage (10) itself parallel to the direction of travel (X), and defining as a part thereof a second aisle seat for the elongated metal products traveling along the conveying line, the second aisle seat being aligned with the first aisle seat along the direction of travel (X); a second gripping means (31, 32) disposed on the second structure (30) at the second passage seat and configured to grip a leading end of the second elongated metal product or a trailing end of the first elongated metal product; a power supply group (40) for supplying a mains voltage and comprising conductors (210; 121, 122) connected respectively to the first gripping means (21, 22) and the second gripping means (31, 32) for supplying current to the end and to the tip; Equipped with The power supply group (40) At least one inverter (41) mounted on the carriage or installed outside the carriage; At least one transformer (42) mounted on the carriage and supplied with power from an inverter (41); At least one rectifier (43) mounted on the carriage and electrically connected to the transformer (42) via the first gripping means (21) and the second gripping means (22); A control unit (50); In a welding machine (1) having the inverter (41) being a variable frequency single or multi-phase inverter, the control unit (50) being programmed to operate the inverter (41) at a frequency above 700 Hz; at least one transformer is sized to provide a predefined nominal power Pn at a prespecified nominal power frequency fn; Where: For an operating power Pex generated during welding, if the preset nominal power Pn of the transformer is less than the operating power Pex and the nominal supply frequency fn is less than 700 Hz, is the at least one transformer (42) sized to provide an effective power Pe equal to or greater than the operating power Pex at a frequency above 700 Hz; or For an operating power Pex generated during welding, a predefined nominal power Pn of the transformer is at least equal to the operating power Pex, and if the nominal supply frequency fn is greater than 700 Hz, the at least one transformer (42) is sized to provide an effective power Pe greater than the operating power Pex at a frequency greater than the nominal supply frequency fn. A welding machine (1).

2. The welding machine (1) of claim 1, wherein the control unit (50) is programmed to operate the inverter (41) at a frequency of 700 to 2000 Hz.

3. The welding machine (1) according to claim 1, wherein the control unit (50) is programmed to operate the inverter (41) at a frequency between 900 and 1100 Hz, preferably around 1000 Hz.

4. The power group (40) is comprised of a plurality of transformers (42a, 42b, ... 42n) connected in parallel with one another, each of the plurality of transformers sized to provide a predetermined nominal power Pna, Pnb... at a predetermined nominal power supply frequency fn, such that the sum of the nominal powers Pna, Pnb... Pnn of the plurality of transformers is either: - less than the operating power Pex generated during welding when the predetermined nominal power frequency fn is less than 700 Hz, in which case the multiple transformers are sized collectively to provide an effective power Pe equal to or greater than the operating power Pex at frequencies above 700 Hz; or at least equal to the operating power Pex generated during welding for a given nominal power frequency fn greater than 700 Hz, in which case the transformers are sized collectively to provide an effective power Pe greater than the operating power Pex at a frequency greater than the nominal power frequency fn; A welding machine (1) according to any one of claims 1, 2 and 3.

5. The welding machine (1) according to claim 1, wherein the operating power Pex has a value comprised between 200 and 2000 kVA.

6. The welding machine (1) according to claim 1, wherein each of the one or more transformers (42; 42a, 42b, ... 42n) has a weight between 150 and 700 kg.

7. The size of each of the one or more transformers (42; 42a, 42b, ... 42n) is: a height h between 450 mm and 650 mm; a length L between 400 mm and 450 mm; and - Depth p is between 300 mm and 350 mm 2. The welding machine (1) according to claim 1,

8. The welding machine (1) according to any one of the preceding claims 1 to 7, wherein the power supply group (40) comprises a system for providing a boosted voltage.

9. 2. The welding machine (1) according to claim 1, wherein each of the first structure (20) and the second structure (30) extends in a longitudinal direction transverse to the direction of travel (X) and is connected between support parts (23, 24; 33, 34) provided on the carriage (10) at opposing positions in the longitudinal direction, and between each of the support parts a frame (25, 35) is provided for accommodating actuators of each of the gripping means (21, 22; 31, 32).

10. 2. The welding machine (1) according to claim 1, wherein the at least one transformer (42) or the plurality of transformers (42a, 42b, ... 42n) are arranged on top of a frame (25, 35) of the first structure (20) or the second structure (30).

11. 2. The welding machine (1) according to claim 1, wherein at least one transformer (42) or a plurality of transformers (42a, 42b, ... 42n) are arranged behind the frames (25, 35) of the two structures (20; 30) relative to the two passage seats, preferably in the support part of the structure.

12. 2. The welding machine (1) according to claim 1, wherein at least one transformer (42) or a plurality of transformers (42a, 42b, ... 42n) are arranged in front of the frames (25, 35) of the two structures (20; 30) relative to two passage seats in the support part.

13. 2. The welding machine (1) according to claim 1, wherein the at least one transformer (42) or the plurality of transformers (42a, 42b, ... 42n) are arranged outside the frame (25, 35) of one of the two structures (20; 30).

14. 2. A welding machine (1) according to claim 1, wherein the carriage (10) consists of two beams (11, 12) equipped with wheels (17) for sliding parallel to the direction of travel (X) along a track, the two beams (11, 12) being connected to each other to form a framework for supporting two structures in the plane of the framework, the carriage (10) being provided with a cantilever-like appendage (15) extending outside the framework, transversely to the direction of travel (X), behind the frame (25, 35), and the at least one transformer (42) or several transformers (42a, 42b, ... 42n) are arranged on the appendage (15).

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