MXPA06012270A

MXPA06012270A - Furnace brazing process.

Info

Publication number: MXPA06012270A
Application number: MXPA06012270A
Authority: MX
Inventors: Francesco Gropallo
Original assignee: Francesco Gropallo
Priority date: 2004-04-22
Filing date: 2004-04-22
Publication date: 2007-04-30
Also published as: JP2007533466A; AU2004318635A1; CA2564514A1; WO2005102579A1; BRPI0418728A

Abstract

A furnace brazing process for metal parts of which at least one tubular (3), comprising the positioning of the filler metal (5, 6, 18) preferably in pre-formed shape inside said tubular part and successive reheating inside the furnace to induce the melting of the filler metal and the accomplishment of the joint. The process is particularly suited to the construction of towel-rail type radiators.

Description

STRONG SOLDIER PROCESS IN OVEN FIELD OF THE INVENTION The present invention is related to a strong welding process, especially of elements that are difficult to access from the outside, such as tubes, more specifically to join the elements that constitute a "towel rail" type radiator. This process, according to a preferred aspect is a process of strong oven welding.

BACKGROUND OF THE INVENTION The strong soldier is a system that is commonly used to permanently join two metal parts (the metal can be non-ferrous or ferrous, such as steels with various carbon contents). The union takes place thanks to a thin layer of a metal, different from the material that composes the pieces that are going to unite, called deposit or metal of contribution. The filler metal has a lower melting point than that of the material to be joined, and the area to be welded is brought to a temperature at which the filler metal is melted. In general, the molten filler metal penetrates through capillary action the free space between the two pieces that are to be joined, thus forming the layer that, once solidified, forms the joint. There are two main technologies of strong welding, which differ in the method of supplying the heat to cause the fusion of the filler metal: strong welding by flame, by means of which it is heated directly and locally the area of the joint where the filler material has been placed, and strong welding in the furnace in which the pieces that are to be joined are introduced after the filler metal has been placed in the joint area in a way adequate Inside the oven, the pieces are brought to a temperature at which the fusion of the filler metal occurs. The heating can be carried out gradually and affects all the pieces to be joined and not only the area affected by the joint. It is also normally carried out gradually so as not to induce stress or damage to the parts to be treated. The furnace may consist of several chambers through which the parts to be treated are carried on a conveyor belt suitably constructed to withstand heat, or by means of suitable mechanical means of another type. There are several systems to position the filler metal in the appropriate place; for example, metallic wires bent in a suitable manner can be used to adapt to the characteristics of the related site. Or, pastes composed of metal powder combined with a suitable binder are generally used; in many cases, in fact, the structure of the joint does not allow a precise positioning of the filler metal in the wire form. One field for the strong welding application is to join tubular elements to one another, such as occurs for example when joining a tube to another tube, or to an element of another type, such as, for example, end caps at the ends of the tubes. In this case, a tight connection is required. An application of special interest is in the production of towel-type radiators, commonly used for domestic heating. Typically This type of radiator consists of two tubular collectors parallel to each other, connected transversely by means of a series of tubes (they generally form a structure that looks like a staircase); A fluid, usually water, can enter at one end of the manifold and exit at the opposite end of the other manifold after it has been circulated through the transverse tubes.

The points that are fastened to the strong welding, which must also ensure an adequate seal for liquid, are the connections of the pipes to the collectors, and the ends of the collectors that are closed properly with closing caps (metallic pieces of form appropriate). Normally a copper-based paste is used for steel radiators. This applies to joints outside, then the strong welding is carried out in the furnace. This process is deficient for several reasons: the material of contribution must be able to be dispersed throughout the board in order to obtain an even distribution and it is difficult to position it correctly. Normally this operation is carried out manually by an operator and therefore is hardly reproducible, therefore, the metal is dosed with a large excess, with waste of material, the possibility of obtaining irregular surfaces and, in many cases, bad dissemination throughout the board. This results in a high percentage of rejected parts (often due to inadequate liquid seal). The external positioning also involves the possibility of dripping the molten filler material, thus damaging some parts of the furnace, for example the conveyor belt. The use of solder pastes, which is usually preferred due to the positioning difficulties and which is necessary in the cases of the closure caps of the collectors, may involve disadvantages such as the presence of impurities, for example leaving carbonaceous residues, during and after strong welding, which can compromise the quality of the joint. In addition, the metal in a paste is necessarily diluted in a binding agent, which reduces the concentration of metal in the relevant zone near the joint, with greater dispersion of the metal during the step of forming the joint. In addition, solder pastes, and especially all pastes containing different metals, have a production cost that can be considerable, depending on the metal they contain. Because they involve a production process that involves specialized machinery, it is usually necessary to select them from among those available in the market, which limits the choice of the metal contribution to a small group of metals containing compounds, since it is often too expensive producing or producing a non-commercial compound paste, while useful metals (the term means metals or alloys) are generally available with high purity (such as, for example, in the form of metal wires or powders) in a wide range of compounds, with high qualitative standards.

BRIEF DESCRIPTION OF THE INVENTION Now the aforementioned problems have been solved through the process of strong welding to join two metal pieces, which consists of at least one tubular, consisting of: Positioning a filler metal in one of said metal pieces; - Position the metallic pieces that are going to join together; Heating said metal parts to such a temperature that causes the melting of said filler metal; process in which said filler metal is positioned within the tubular metal part before fusion. According to a preferred embodiment of the invention, said heating is carried out in an oven. According to another preferred aspect of the invention, said filler metal has the shape of the preformed object, which may be, for example, a properly bent metal wire or an appropriately molded object, preferably a thin ring. According to a specific aspect of the invention, the pieces to be joined are the metal parts of a towel-type radiator. For example, they can be a tube and a tubular collector and the tube can be welded in a hole in one of the lateral, preferably flat, surfaces of the collector. Or it can be a closing lid that is going to be connected to one end of the collector in order to close it.

In this case, according to a preferred aspect of the invention, the closure cap has an outer perimeter substantially similar in shape and dimensions to the outer perimeter of the collector; according to another preferred aspect, it has, on the internal face (which is intended to face the collector once the connection is made), a step, the outer end of which has the shape and dimensions in such a way that it enters the collector, thus leaving between each other and the internal walls of the collector barely sufficient space to create a strong solder joint. The closure cap has an external face, in correspondence of which is provided with means for retaining the filler metal in a preformed form near the joint to be welded, for example close to said first step if there is, in general, close to the surface that is intended to form, together with the collector, the joint to be welded. Preferably, these means are an opening formed in the internal face, at the edge of the step. The invention is also related to a closure cap as described above.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be illustrated by means of the detailed description of the preferred embodiments, more non-exclusive, which are presented merely as examples, with the help of the attached figures in which: Figure 1 is a detail of a towel-type radiator; Figure 2 represents schematically a detail of the tube of a towel-type radiator inserted in a collector to form a strong welding joint. Figure 3 shows schematically in cross section a detail of a tube of a towel-type radiator prepared for strong welding with the positioning of the filler material. Figure 4 schematically represents in cross section a detail of a tube of a towel-type radiator prepared for strong welding with the positioning of the filler material, inserted inside the collector.

Figures 5 and 6 schematically represent a closure cap for closing the collector of a towel-type radiator viewed from the inner side and in lateral section. Figure 7 shows schematically, in lateral section, a closure cap inserted inside the collector, ready for strong welding.

DETAILED DESCRIPTION OF AN INCORPORATION With reference to Figure 1, a detail of a towel-type radiator can be observed in which a tubular collector 1 can be noticed. Preferably, the collector has a flat surface 2 in which several openings are formed to receive the ends of the collector. the tubes 3, leaving a sufficient space to create a connection through strong welding between the collector and the tubes, so that the piece is created of which a detail is shown. The tubes can be tapered at the ends in order to facilitate insertion at a correct depth. Sometimes the ends can be reformed after they are inserted, by means of an appropriate machine that is inserted into the manifold from one end. According to a first aspect of the invention, the filler metal is positioned on the outer surface at the end of the tubes, which is then inserted into the hole in the appropriate position, so that the filler metal is inside the collector close to the joint to be welded, so that it is able to approach, once fused, through capillary action to the space in said meeting. The pipes and the collectors are inserted inside the oven in order to cause the melting of the filler metal. Generally, a fully assembled radiator is inserted into the furnace, and this comes out as a finished product after cooling and solidification of the filler metal. The filler metal can be positioned in several ways. For example, a layer 5 constituting a thin film of the filler metal (for example a metal laminate) can be applied or deposited around the end 4 of the tube 3, as shown in Figure 2.

According to a preferred aspect of the invention, the preformed shaping feedstock is positioned, for example a metal wire ring that is placed around the end of the tube. Still more preferably, the ring 6 will be placed in a special slot 7 (see Figure 3) which is formed around the end 4 of the tube (for example by engraving on the outer surface 8 of the tube). The ring can be of the open type, in order to facilitate its placement. In Figure 4 is represented the tube 3 inserted into the opening in the surface 2 of the collector 1, before the heating step, the ring must be found near the joint, so that, by means of capillary action, it is taken to the space between the walls 9 of the collector and the tube 3. The end 4 of the tube 3 will be little protruding in the collector, for example by a distance of between 1 and 3 mm, for example 2 mm. It will have to pass the filler metal, if it has been deposited before the insertion of the tube 3 in the collector 1, inside the opening. Advantageously, the groove 7 will be of sufficient depth to accommodate the preformed shape of the metal so that it does not protrude from the surfaces 8. Or, the end of the tube may be tapered, which also facilitates correct insertion, which, of Declining being sufficient renders unnecessary the presence of the groove 7. In such a case, the filler metal must be shaped so as to allow it to remain in position around the tube, for example, it can be a tightening ring around the surfaces of the tube by elasticity, or a layer (or a solder paste) or a spiral ring, which has the advantage of being able to enlarge without leaving part of the perimeter of the tube uncovered. Advantageously, the decrease and the presence of a slot can be combined properly. In order to ensure the correct insertion of the tubeA guide 10 can also be provided on the surface 8 of the tube, for example a ring-shaped protrusion which prevents too much insertion of the tube. It is also possible that the positioning of the filler metal follows the mutual positioning of the metal pieces that are to be joined together. In the case of the tube to be fixed to the collector, for example, a ring can be attached to the end of the tube already inserted, by means of special machinery. Anyway, it is possible to reform the ends of the tubes from the inside, according to known methods, with the filler metal already positioned; this favors the maintenance of the positions of the metal, beyond the correct positioning of the joint. In contrast to the positioning of the filler material, especially if it is in the form of a paste, on the outside of the joint, the positioning of the filler material in the shape of the preformed object is suitable for automatic positioning. Figures 5 and 6 show a closing lid 11, according to a particular aspect of the invention, for closing the end 12 of the collector 2. Advantageously, the outer edge 13 can have the outer profile of the cross section of the collector . Towards the inner face 15 of the cover and on it a rung 14 will be formed, whose external surface 16 can enter inside the manifold; between the internal surface 17 of the collector and said surface 16 is the space where the molten filler material must be entered (see Figure 7). Analogously to the step 14, an opening 19, suitable for the reception of an unstable gas, can still be formed towards the inner side. preformed article 18 of filler material (which can be a metal wire ring appropriately). It can be fixed, in a manner analogous to the rings used for the tube, by means of its own elasticity and / or by special means, such as projections 20, formed for example by punching on the inside face 15 of the closure cap , close to the edge of the opening 19. Such an opening, with or without protrusions in this case represents the means for fixing in its position the filler material. According to a preferred embodiment, the projections which fix in place a preformed object, especially when this is in the form of an open ring, can be continuously extended over a portion of the selvedge 22 of the inner face 15 of the closure cap 11. example, when the closure cap has the shape shown in Figure 5, with the said edge 22 in a semicircular shape or rounded portion 23 facing a linear portion 24 delimited by two (rounded) corners 25, one can extend a continuous projection on the entire portion 23 and on the corners 25 (may or may not extend on the linear portion 24), while the central portions 26 remain without projections. This facilitates the insertion of the preformed object in the form of an open ring, when it is especially advantageous when this operation is carried out with a machine. The person skilled in the art can find, according to the above exemplified, other possible ways to implement the protrusions in closure caps with the shape shown in Figure 5 or other forms, in order to facilitate the insertion of the metal preform. input. The closure cap may have one or more holes 21 or blind, depending on whether the involved end of the manifold is to be connected to a tube or not. As can be seen in Figure 7, the opening 19 is delimited by the interior surface 17 of the collector and there will be little possibility of dispersion of the filler metal once melted, thus increasing the efficiency of the process. In general, copper-based alloys are used to weld steel elements in the construction of radiators. If preformed filler metal configurations are used, as mentioned, then it is possible to have a large variety of compounds available. This allows them to be selected based on the requirements of the product process and quality. For example, lower melting point alloys can be used instead of those of current practice, thus reducing the temperature of the furnace. This could reduce the mechanical stresses in the finished product and eliminate the need to correct deformations due to heating. The surfaces will be of better quality, even with the prospect of more treatments such as chrome plating. Or you can select alloys of colors, suited to the color of the mechanical parts that are to be joined, such as, for example, those based on copper-nickel or copper-silver if the material of the pieces to be joined is, for example, stainless steel example. If aluminum pieces are to be joined, an aluminum-silicone alloy for the filler metal can be selected, which could easily allow the construction of aluminum radiators. It is possible to use preformed objects provided with an antioxidant if the type of filler metal requires it, for example in the case of alloys based on zinc or aluminum, such as aluminum-silicone. For example, preformed metal wire objects with centers can be used antioxidants The metal rings can be obtained by cutting wire from a roll, if necessary it can be properly bent, for example in a mold, in the form of rings for the closure caps of the collector. The metallic wire of appropriate diameter can be selected, for example, from 0.5 to 2 mm, for example 1 mm. This process, as mentioned, is suitable for the construction of towel-type radiators, where the dimensions of the tubular pieces that are going to join the render of difficult access from the inside. For example, the collectors can be 20 to 50 mm wide, the tubes with smaller diameters suitable, for example, between 10 and 30 mm. Frequently the tubes have sections of unrounded forms, for example oval sections: in these cases, the preformed objects should have the appropriate conformations. The thickness of the metals can vary, for example, between 0.5 and 2 mm. However, it is considered that the processes can find other applications than those that are exemplified, without departing from the scope of the protection of the claims. According to a preferred aspect of the invention, the process is, as mentioned, a process for strong welding. However, it is possible that the heat is supplied to the joint through other methods, for example, flames.

Claims

1. A strong welding process for joining two metallic pieces (1, 3, 11) in which at least one (1) is tubular, consisting of: - The placement of a filler metal (5, 6, 18) in at least one of the metal parts; The mutual placement of the metal pieces that are to be joined; The heating of said metal parts at such temperature that causes the melting of said filler metal; process in which said filler metal is placed inside said tubular metal part before melting it.

2. The process according to claim 1 in which said heating is carried out in a homo.

3. The process according to claim 1 or 2 wherein said filler metal takes the form of a preformed metal object.

4. The process according to claim 3 wherein said object is a metal wire bent in an appropriate manner.

5. The process according to any of the preceding claims in which the end (4) of a tube (3) is welded into a hole provided in the side wall (2) of another tubular metal part (1).

6. The process according to claim 5 in which a layer (5) of filler metal is applied or deposited around the end of said tube and then the end of the tube is inserted into said hole.

7. The process according to claim 5 in which a preformed metal object is placed around the end of said tube and then the end of the tube is inserted into said hole.

8. The process according to claim 7 wherein said preformed metal object is a metal wire ring (6).

9. The process according to claim 8 in which said ring is placed in a special slot (7) provided around the end of said tube.

10. The process according to any of claims 5 to 9 in which the end of said tube has a decreasing shape.

11. The process according to any of claims 5 to 10 in which the end of the tube can be reformed after it is inserted into said hole.

12. The process according to any of claims 5 to 11 in which the end of said tube is inserted inside said hole so that it protrudes inside said tubular piece 1 to 3 mm.

13. The process according to any of claims 1 to 4 in which a closure cap (11) is welded in order to close the end (12) of a tubular collector (1).

14. The process according to claim 13, wherein said closure cap has an internal face (15), corresponding to which means (19, 20) are provided to support the filler metal in the form of a preformed object (18). near the joint to be welded.

15. The process according to claim 14 wherein said closure cap has a step (14) suitable for insertion into said tubular manifold, whose side face (16) is such as to create, with the internal surface (17) of the manifold the board to be welded.

16. The process according to claims 14 and 15 wherein said means for holding the filler metal in the form of a preformed object (18) adjacent to the joint to be welded is an opening (19) formed along the outer edge (13) of the closing lid.

17. The process according to claim 16 wherein said means for holding the filler metal in the form of a preformed object comprises a series of projections (20) provided on the inner face 15 of the closure cap.

18. The process according to any of the preceding claims in which the metal pieces to be joined are pieces of a towel-type radiator.

19. A closure cap (11) for closing the end of a tubular collector (1), with an internal face (15), in correspondence with which means (19, 20) are provided for supporting a filler metal in the form of a preformed object next to the surface (16) intended to form, together with said collector, the joint to be welded.