EP0000456B1 - Mould for the metallothermic welding of metal workpieces - Google Patents

Description

The present invention relates to a mold for metallothermic, in particular aluminothermic, welding of metal parts.

This type of welding consists in assembling two metal parts of identical or relatively similar shapes by pouring a certain quantity of hot welding fluid around the butt ends to be welded. To make such welds, a mold is used, generally in several parts, intended to surround the parts to be welded and provided with a casting cavity allowing the hot welding fluid to come into contact with the ends to be welded.

This type of welding is most often applied to the welding of metal profiles and in particular of railway rails.

In the case of aluminothermic welding, the preparation of the hot welding fluid, which is most often molten steel, is carried out by the reduction of iron oxides by aluminum.

Since the mold cannot be perfectly joined to the surface of the metal parts and to the surface of any other parts of the mold, it is necessary to seal the mold before proceeding with the actual welding operation.

This sealing is conventionally achieved by luting by means of a paste which is sufficiently refractory so as not to be destroyed by contact with the hot welding fluid. This paste, generally formed from silica sand and an agglomerating agent, for example clay and water or other additives, is deposited on the mold before or after its installation on the parts to be welded and before the pouring of hot welding fluid.

This sealing method gives good results, but it has the disadvantage on the one hand of being long to execute and on the other hand of requiring a correct and careful realization which is not always easy to implement on the site.

It has also been proposed to replace conventional luting by a dry joint constituted for example by a cord of asbestos or even by a cord of an organic material. Such seals have the disadvantage of giving off hot steam, in contact with the hot welding fluid, which can cause blowing in the weld and consequently adversely affect the quality of the weld obtained.

• Le brevet DE - C - 572 591 qui décrit un moule dont les bords sont chanfreinés vers l'extérieur et pourvus d'une matière d'étanchéité telle que de l'argile, le brevet US-A-3 113 359 qui décrit un moule comportant une matière d'étanchéité. telle qu'une laine ou un feutre céramique, placée dans des évidements du moule et le brevet FR - A - 1 327 977 qui décrit un moule comportant une matière d'étanchéité constituée par des blocages céramique alumine silice ou des blocages fibreux réfractaires.

To illustrate the prior art relating to multi-part molds for metallothermic welding of metal parts, comprising a sealing material, the following documents may be cited:

• Patent DE - C - 572,591 which describes a mold whose edges are chamfered towards the outside and provided with a sealing material such as clay, US-A-3,113,359 which describes a mold comprising a sealing material. such as a wool or a ceramic felt, placed in recesses of the mold and patent FR - A - 1 327 977 which describes a mold comprising a sealing material constituted by ceramic blockages alumina silica or refractory fibrous blockings.

Mention may also be made of US Pat. No. 3,022,554 which describes a mold in several parts comprising means capable of ensuring the relative positioning of two parts of mold between them by means of lugs of one of the parts of mold suitable for cooperate with corresponding recesses in the other mold part.

The invention aims to avoid the aforementioned drawbacks by providing a ready-to-use mold and automatically ensuring the desired tightness as soon as it is placed on the parts to be welded.

The invention relates more particularly to a multi-part mold intended for the metallothermic welding of two metal parts by providing around the ends of the parts to be welded a casting cavity intended to receive a certain quantity of hot welding fluid, in which one at least surfaces of the mold, intended to come into contact with a part to be welded or possibly with another part of the mold, comprises a projection having a side inclined towards the outside with respect to the casting cavity, said projection being provided with '' a sealing material, the essential characteristic of which resides in the fact that the sealing material is a seal formed by a ribbon of a compressible material with low loss on fire, one of the faces of which is bonded to said projection.

By the expression "with low loss on ignition", it is meant to mean that the compressible material constituting the seal releases little gas by heating or by reaction with the hot welding fluid and that experience has shown that this low clearance does not cause blowing.

A material meeting these characteristics will advantageously be a felt of mineral origin, for example consisting of silicates such as alumina silicates optionally containing chromium oxides, magnesia silicates, double silicates, such as sodium silicates and iron of the chrosidolite type at 3% water of crystallization and silicates of magnesia and iron of the amosite type at 3% water of crystallization, etc. Such mineral felts release at high temperature only about 2 to 5% of their weight, while asbestos of the chrysolite type releases about 10 to 20%.

Felts of this type are commercially available and can be obtained from manufacturers such as Johns Manville, FERLAM, SEPR (European Society of Refractory Products).

To ensure a particularly advantageous seal, the felts used in the molds of the invention must have a density of approximately 50 to 200 kg / m ³ and preferably approximately 100 to 200 kg / m ³ .

The tape is glued to the projection, either using organic glue or using mineral glue. In the case of an organic glue, there is a glue ring on a portion of the projection located clearly outside 1 relative to the mold cavity, so as to prevent the glue from giving off gases in the casting cavity. In the case of a mineral glue, a layer of glue can be deposited over the entire projection.

In a particularly advantageous embodiment of the invention, the face of the strip, which is opposite to the face glued to the projection, is coated with a malleable metal sheet, for example an aluminum sheet. This sheet is preferably bonded to the opposite face of the ribbon, either by means of a layer of organic adhesive placed on a clearly external part of the opposite face with respect to the casting cavity, for the same reasons as above, either by means of a layer of mineral glue placed on the entire face of the ribbon.

As mineral glue, it is possible, for example, to use an adhesive for foundry cores such as the "CORSY 9A" adhesive from the company FOSECO ^* or the "K 3" adhesive from the company Boniface.

This metal sheet offers the triple advantage of ensuring the protection of the felt, of imparting rigidity to the joint and consequently of being able to preform it, and finally to prevent stuffing of the felt during the positioning of the mold, especially in the portions of parts to be welded parallel or slightly inclined with respect to the direction in which the mold is placed on the parts, which is important in the case of rails.

Although the seal between the different parts of the mold and the parts to be welded can be ensured only by bonding seals on projections, the present invention proposes in another embodiment a mold in which the parts of the mold are shaped so sealing between them, in the region above the casting cavity, without requiring the addition of sealing material.

It is thus not necessary to use a sealing material in the region above the casting cavity, that is to say in a region where the sealing is not as critical. than in the region around the casting cavity.

This embodiment also offers the advantage of ensuring at the same time the positioning of the mold parts between them, while creating a vent for the evacuation of air at the time of casting.

To this end, the invention provides that the mold parts comprise, in their portions in contact with each other above the casting cavity, nestable surfaces ensuring the positioning and sealing of these portions therebetween.

According to a feature of the invention. each of the surfaces. nestable comprises a flat contact surface provided with a bead and a groove capable of cooperating respectively with a groove and a bead of the flat contact surface of another mold part.

The bead and the groove of a planar contact surface are preferably arranged symmetrically with respect to a central recess opening into the planar contact surface so that two identical mold parts can be associated by bead cooperation of the one with the groove on the other, and vice versa, the respective recesses together constituting a casting basin capable of directing the hot welding fluid into the casting cavity.

To ensure the tightness of the mold of the invention around the casting cavity, it is possible to combine a sealing mode obtained by bonding seals on projections to a conventional sealing mode obtained by luting refractory paste.

Although the mold of the invention can be used in the welding of any metal parts, it finds a particularly interesting application in the welding of railroad tracks.

• la figure 1 représente une section partielle d'un moule selon l'invention dont une surface de contact présente une saillie revêtue d'un joint d'étanchéité avant compression de ce dernier;
• la figure 2 représente une vue analogue à celle de la figure 1 après compression partielle du joint;
• la figure 3 représente une vue analogue à celle de la figure 2 après compression totale du joint;
• la figure 4 représente une vue en perspective montrant un moule en trois parties dans son application à la soudure de deux rails de chemin de fer;
• la figure 5 représente une vue en coupe d'une partie du moule de la figure 4;
• la figure 6 est une vue de face d'un autre moule en trois parties, destiné à la soudure de rails de chemin de fer, dans lequel l'étanchéité autour de la cavité de coulée est assurée par collage d'un joint et dans lequel l'étanchéité au-dessus de la cavité de coulée est assurée par des surfaces emboîtables;
• la figure 7 est une vue de côté intérieur d'un demi-moule latéral du moule de la figure 6;
• la figure 8 est une vue de dessus du moule de la figure 6; et
• la figure 9 est une vue du côté intérieur d'un demi-moule analogue à celui de la figure 7, dans lequel l'étanchéité autour de la cavité de coulée est assurée par lutage au moyen d'une pâte réfractaire.

Other characteristics and advantages of the invention will be better understood on reading the additional description which follows with regard to three nonlimiting examples of molds according to the invention applied to the welding of railway rails. and with reference to the attached drawings, in which:

• FIG. 1 represents a partial section of a mold according to the invention, a contact surface of which has a projection coated with a seal before compression of the latter;
• 2 shows a view similar to that of Figure 1 after partial compression of the seal;
• Figure 3 shows a view similar to that of Figure 2 after total compression of the joint;
• FIG. 4 represents a perspective view showing a three-part mold in its application to the welding of two railway rails;
• Figure 5 shows a sectional view of part of the mold of Figure 4;
• FIG. 6 is a front view of another three-part mold, intended for the welding of railroad tracks, in which the sealing around the casting cavity is ensured by gluing a joint and in which sealing over the casting cavity is ensured by nestable surfaces;
• Figure 7 is an interior side view of a side mold half of the mold of Figure 6;
• Figure 8 is a top view of the mold of Figure 6; and
• Figure 9 is a view of the inner side of a half-mold similar to that of Figure 7, wherein the seal around the casting cavity is provided by luting by means of a refractory paste.

FIG. 1 shows a mold 10 whose surface 12 intended to come into contact with the surface 14 of a metal piece to be welded (or of another part of the mold) 16 includes a projection 18 forming an integral part of the mold . This projection 18 has a side 20 inclined at an angle a with respect to the surface 12. The side 20 is inclined outwards relative to the casting cavity 22 (located to the right of the projection 18 in FIG. 1 ). The angle a is an acute angle which may for example have a value of 10 °, although this value is not decisive.

A compressible felt tape with low fire loss 24 is glued by its face 26 to the inclined flank 20 of the projection 18 by means of a glue rod 28 disposed on a part of the flank 20 located clearly outside relative to to the cavity 22 of the mold. On the face 30 of the tape opposite to the face 26 is glued an aluminum sheet 32, of the same width as the felt tape, by means of a layer of adhesive 34 deposited clearly on the outside of the face 30 relative to to the casting cavity 22.

Figure 2 shows the partially compressed seal after clamping the mold 10 against the metal part (or the mold part) 16 and Figure 3 shows the same fully compressed seal after fully clamping the mold.

Due to the inclination of the side 20 of the projection 18, the strip 24 is more compressed on the side closest to the casting cavity 22 than on the side furthest from the casting cavity. Under such conditions, the force applied to the clamping acts essentially on a very small surface and therefore has a considerable clamping efficiency. In addition, the inclination of the flank 20 of the projection 18 contributes to preventing any evolution of gas in the casting cavity.

It should be noted that it is not necessary for the felt tape to be compressed as much as possible, as shown in FIG. 3, to ensure sealing when a mold according to the invention is applied to parts whose profile does not have exactly the nominal dimensions for which the mold is intended. Indeed, certain zones of the felt tape will be very compressed and others less compressed, but, unless the profile of the parts to be welded does not largely go beyond the range of commercial tolerance of the type of profiles for which the mold is intended, these less compressed areas will still be compressed enough to ensure the required seal.

By way of example, it will be observed that a 6 mm thick felt having a density of approximately 150 kg / m ³ already provides sealing when it is compressed to a thickness of 2.5 mm.

The mold of the invention finds a particularly advantageous application in the welding of railway rails as shown in FIG. 4.

FIG. 4 shows, in exploded perspective, two railway rails 36 and 38 intended to be welded by their respective ends by means of a casting mold comprising two identical side parts 40 and 42 and a sole 44. The lateral parts 40 and 42 are intended to be applied on either side of the rails 36 and 38 by covering the ends to be welded. The sole 44 is intended to be applied under the rails 36 and 38 and under the lateral parts 40 and 42 of the mold. The mold parts 40 and 42 have a profile corresponding to that of the rails so as to follow its shape. The mold parts 40 and 42 have respective recesses 46 and 48 able to form, once the mold parts 40 and 42 joined, a funnel capable of bringing the hot welding fluid into the intermediate space between the two rails. The recess 46 is extended by a recess 50 facilitating access to the hot welding fluid at the bottom of the mold. The recess 48 of the mold part 42 is extended by a similar recess (not visible in FIG. 4).

The sole 44 has a recess 52 promoting the arrival of the hot welding fluid under the two rails at the junction of their ends. The mold parts 40 and 42 are moreover provided with ascent pipes 54 and 56, respectively, making it possible to expel outward the air which is trapped in the mold as the hot welding fluid is poured.

The aforementioned recesses of the mold parts 40 and 42 and of the sole 44 constitute the casting cavity which has been referred to above.

The seal between the different parts of the mold and the two rails is produced by means of seals such as that described above with reference to FIGS. 1 to 3, that is to say a seal formed from a felt tape. coated with aluminum foil and glued to a projection on the side inclined towards the outside with respect to the casting cavity.

The mold part 40 is provided, on its surface intended to come into contact with the two rails 36 and 38 and with the mold part 42, with a seal 58 and a seal 60 arranged respectively on either side of the casting cavity. The seal 58 is bonded to a projection having a side inclined towards the outside with respect to the recesses 46 and 50, along the entire height of the side of the abovementioned contact surface which appears on the left in FIG. 4. The seal 60 is bonded , on a projection having a side inclined towards the outside with respect to the recess 50, along a height on the side of the aforementioned contact surface, appearing on the right in FIG. 4, which corresponds to the portion of said surface coming to be applied on the rail 38. The upper end of the seal 60 is ends with an extension 62 protruding from the projection on which it is glued and having for example a length of 5 to 10 mm, which is intended to prevent any risk of leakage of the welding fluid at the junction of the two mold parts 40 and 42 above the rail 38. The lower ends of the seals 58 and 60 end in similar extensions (not visible in FIG. 4) intended to prevent any risk of leakage of the welding fluid at the junction of the mold part 40 with sole 44. Referring more particularly to FIG. 5, the seal 60 of the mold part 40 ends at its upper end by the above-mentioned extension 62 and at its lower end by an extension 66. The mold part 42 is equipped with two similar seals of which only the upper end of the seal 64 (which is the counterpart of the seal 58 of the mold part 40) is visible in FIG. 4. The upper ends of the seals 58 and 64 do not have any extensions since sealing at this point in the mold is not essential.

It will be noted that, during the assembly of the two mold parts 40 and 42, the upper part of the seal 64 seals with the upper part of the contact surface of the mold part 40 which is not provided with joint and that it is the same for the upper part of the joint 58 of the mold part 40.

The sole 44 is coated with a seal 66 ′ affecting the shape of a rectangular frame, obtainable for example by die cutting, surrounding the recess 52. The seal 66 ′ is glued to a rectangular perimeter projection which has a side inclined towards the outside with respect to the recess 52.

It will be easily understood from FIG. 4 that when the mold parts 40 and 42 and the sole 44 are pressed and held against each other and against the two rails, the seal of the mold at the level of the casting cavity is perfectly done.

It then suffices to introduce the hot welding fluid by means of a crucible opening into the pouring funnel formed by the recesses 46 and 48.

The seals bonded to the various parts of the molds according to the invention will advantageously be installed in the factory after manufacture of the molds so as to avoid having to glue the seals on the site immediately before the welding operation.

By doing so, we can save a significant amount of time and dispense with the use of skilled labor necessary to carry out conventional wrestling operations.

The mold shown in FIG. 6 consists of two identical side half-molds 110 and 110 ′ and a sole 112 and is intended to be used in the metallothermic welding of two end pieces of railway rails. The half-molds 110 and 110 ′ are intended to be applied on either side of the rails by covering the butt ends to be welded and have an internal profile corresponding to a half rail profile. The sole 112 is intended to be applied under the rails and under the half-molds 110 and 110 '.

The seal around the butt ends to be welded, in the region of the casting cavity, is ensured by bonding a seal formed by a ribbon of a compressible material with low fire loss, as described above.

Thus, the half-mold 110 (see FIG. 7) has on its face intended to come into contact with the half-profiles of the rails to be welded two projections 114 and 116 respectively disposed on either side of a recess 118, intended to constitute the casting cavity with the corresponding recess of the half-mold 110 '. The two projections 114 and 116 each have a side inclined at an angle a towards the outside with respect to the recess 118 and are intended to receive by bonding a seal. A seal is also bonded to the floor 112 around the casting cavity.

Above the casting cavity, that is to say above the rails to be welded, the half-molds 110 and 110 'are in contact with each other by respective planar surfaces 120 and 120' which are provided with reliefs allowing their nesting to ensure both the positioning of the two half-molds 110 and 110 'and their sealing in the region of the contact surfaces 120 and 120'.

The reliefs of the surface 120 include a bead 122 and a groove 124 able to cooperate respectively with the groove 124 'and the bead 122' corresponding to the surface 120 'of the half-mold 110'.

The bead 122 and the groove 124 are arranged symmetrically with respect to a recess 126 so that when the two half-molds are joined, the recess 126 forms with the recess 126 'corresponding a pouring basin communicating with the cavity casting through a chamber formed by two recesses 128 and 128 '.

This pouring basin can be provided with a central orifice provided with a removable pouring plug which can be removed to allow the passage of a torch in the case where a welding is carried out with preheating.

Communication between the recesses 126 and 128 and between the recesses 126 'and 128' is ensured respectively by bores 130 and 130 '.

The bead 122 and the groove 124 have a general shape consisting of two linear segments forming an angle between them. In addition, the groove 124 opens on the one hand into the recess 128 and on the other hand into the upper face 182 of the half-mold 110. The depth of the groove 124 is greater than the height of the bead 122 to allow forming , when the half-molds are combined, a vent 132 and a vent 132 '(see FIG. 8) allowing the evacuation of air at the time of the pouring of the welding fluid.

The half-mold 110 further comprises a riser pipe formed by a cylindrical duct of small diameter 132 opening into a cylindrical duct of larger diameter 136 which serves as a receptacle for the excess of the welding fluid which previously heated the two end of rails.

As can be seen in Figures 7 and 8, the half-molds 110 and 110 'are wider at the contact surfaces 120 and 120' to allow better contact between these two half-molds.

FIG. 9 shows the inner face of a half-mold 138, the upper part of which is similar to that of the half-mold 110 of FIG. 7 and the lower part of which is shaped so as to provide sealing by luting. . Thus, the inner face of the half-mold 138 has a flat surface 140 provided with a bead 142 and a groove 144 produced as indicated above with reference to FIGS. 6 to 8.

Furthermore, this inner face has two protrusions 146 and 148 arranged on either side of a recess 150 intended to constitute the casting cavity with the corresponding recess of an identical half-mold.

These two protrusions 146 and 148 have a contour corresponding to that of a half-profile of the rail and are provided with grooves 152 and 154 respectively intended for the application of lute paste.

In the case of a mold comprising two half-molds of the type shown in FIG. 9, the seal between the lower part of the two half-molds and the sole will be carried out by bonding a refractory joint to the sole.

The various parts of the molds of the invention are produced conventionally from a mixture based on agglomerated and hardened sand.

Claims (5)

1. A mould in several parts for the metallothermic welding of two metal items together by arrangement around butts of the items to be welded to define a pouring cavity adapted to receive a quantity of hot welding-fluid, wherein at least one of the faces of the mould, which will contact either one of the items to be welded or possibly another part of the mould. comprises a projection (18) which presents a sloping side (20) towards the exterior of the pouring cavity (22), said projection (18) being fitted with a sealing material, characterized in that said sealing material is a sealing joint (24) constituted by a strip of a compressible material which is little affected by heat, especially a felt of mineral origin, a face (26) of the strip being stuck onto said projection (18).

2. A mould as claimed in claim 1, characterized in that the face (30) of the strip, opposed to the face (26) stuck onto the projection (18), is coated with a malleable metal foil (32), especially an aluminium foil, which is stuck onto said opposed face (30) of the strip.

3. A mould as claimed in any one of claims 1 and 2, characterized in that the mould parts (110, 110') comprise, in those portions which are in contact with each other, above the pouring cavity, interlocking surfaces which ensure the location and staunchness of that part in respect of each other, each interlocking surface comprising a flat contact-surface (120, 120') provided with a ridge (122, 122') and a groove (124, 124') with which a groove (124', 124) and a ridge (122', 122) respectively on the flat surface (120', 120) of another mould part (110', 110) cooperate.

4. A mould as claimed in claim 3, in which the ridge (122, 122') and the groove (124, 124') of a flat contact-surface are disposed symmetrically in relation to a central slot (126, 126') opening out upon said flat contact-surface whereby two identical mould parts (110, 110') may be associated by cooperation of the ridge (122, 122') of one mould part with the groove (124, 124') of the other mould part, and conversely, the respective central slots (126, 126') forming together a pouring opening for directing hot welding-fluid into the pouring cavity:

5. A mould as claimed in claim 4, in which one of the ends of the groove ( 124; 124') opens out upon the central slot (126, 126') and the other end of the groove (124, 124') opens outside the mould, the depth of the groove (124, 124') being greater than the height of the ridge (122, 122') so as to permit the formation when the groove (124, 124') of a mould part (110, 110') receives the ridge (122', 122) of another mould part (110', 110), of a vent (132, 132') for the evacuation of air when welding-fluid is poured into the pouring cavity.

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