METHOD FOR SEALING A CASTING MOULD FOR ALUMINOTHERMIC RAIL WELDINGS

Abstract

A casting mold (6) consists of two mold halves (4, 5), which are intended for setting up on both sides of the welding groove (3) between two rail ends (1, 2) to be connected, thereby forming a casting space (8) representing a cross-sectional profile of the rails. For sealing the casting space (8) between the rail bodies on both sides of the welding groove (3) and the wall portions (9, 10) of the casting mold (6) that are facing this welding groove, inserted in gaps (11, 12) are strips consisting of a compound at least containing expandable graphite, which as a result of heat being supplied during a preheating process expands and forms a reliable seal. In comparison with using filler sand at this point, there is the advantage that a much smaller quantity of compound has to be carried along when working on the laid track.

Claims

1. A method for sealing a casting space (8, 27) of a casting mold (6, 21) for performing an alum inothermic welding process on components, with two mold halves (4, 5; 24, 25), one upwardly open, which replicate the component profile in the area of the weld, wherein slits present between the facing surfaces of the components and the wall sections (9, 10) of the casting mold (6, 21) neighboring the latter are closed with a fireproof sealing compound, wherein a steel melt is prepared in a reaction crucible, and introduced into the casting space (6, 21) for performing the welding process set up as a rail connection welding or repair welding operation, in particular of the railhead (22), characterized in that an expandable substance is used as the sealing compound, wherein the expansion can be initiated thermally or chemically, and wherein an intumescent substance consisting at least partially of an intumescent material is used as the expandable substance.

2. The method according to claim 1, characterized in that the sealing compound is received in gaps (11, 12; 28, 29) of the mold halves (4, 5; 24, 25).

3. The method according to claim 1, characterized in that the sealing compound is introduced into gaps (11, 12; 28, 29) of the mold halves in conjunction with putting together the mold halves (4, 5; 24, 25) at the respective welding point.

4. The method according to claim 1, characterized in that the expandable sealing compound is used in the form of a molding body.

5. The method according to claim 1, characterized in that the expandable sealing compound is used in the form of a strip.

6. The method according to claim 5, characterized in that the strip is used in the form of an adhesive, in particular a self-adhesive strip.

7. The method according to claim 5 or-6, characterized in that the strip is positively fixed in gaps (11, 12; 28, 29) of the mold halves (4, 5; 24, 25) at the location of the welding point.

8. The method according to claim 1, characterized in that the expandable sealing compound is used in the form of a pasty substance.

9. The method according to claim 8, characterized in that the pasty substance at its job site is applied in the form of a caterpillar.

10. The method according to claim 8, characterized in that the pasty substance is injected into gaps (11, 12; 28, 29) of the mold halves (4, 5; 24, 25) at the location of the welding point.

11. The method according to claim 1, characterized in that the expandable sealing compound is used in the form of a free-flowing granulate.

12. The method according to claim 1, characterized in that the expandable sealing compound consists of a combination of exfoliated graphite and other mineral fireproof materials.

13. The method according to claim 1, characterized in that the expansion of the sealing compound is initiated thermally by a pyrotechnic, an exothermally reactive substance or a similar heat source.

14. The method according to claim 1, characterized in that the expansion of the sealing compound is initiated thermally by preheating the casting mold (6, 21) before pouring the steel melt.

15. The method according to claim 1, characterized in that the gaps (11, 12; 28, 29) as well as the wall sections (9, 10) of the casting mold (6, 21) are set up with the proviso that an expansion of the sealing compound preferably takes place toward the exterior side of the casting mold, in so doing satisfying the sealing function.

16. The method according to claim 1, characterized in that the expandable sealing compound is used so as to replicate a welding bead geometry.

17. The method according to claim 2, wherein the expandable sealing compound is used in the form of a molding body.

18. The method according to claim 2, wherein the expandable sealing compound is used in the form of a strip.

19. The method according to claim 2, wherein the expandable sealing compound is used in the form of a pasty substance.

20. The method according to claim 2, wherein the expandable sealing compound is used in the form of a free-flowing granulate.

Description

[0026] The invention will be described in more detail below with reference to the attached drawings. Shown on:

[0027] FIG. 1 is a perspective view of a casting mold according to the invention in a partial section;

[0028] FIG. 2 is a flat, sectional view of a casting mold half according to FIG. 1 in the initial state;

[0029] FIG. 3 is a flat, sectional view of a casting mold half according to FIG. 2 at the time an exfoliated graphite expansion begins;

[0030] FIG. 4 is a flat, sectional view of a casting mold half according to FIG. 2 at the time an exfoliated graphite expansion begins while initiating the swelling process via preheating;

[0031] FIG. 5 is a flat, sectional view of a casting mold half according to FIG. 2 at the time an exfoliated graphite expansion has concluded;

[0032] FIG. 6 is a flat, sectional view of a casting mold prepared for surface-layer welding in the railhead area;

[0033] FIG. 7 is a flat, partially sectional view of a strip-like insert of exfoliated graphite as the sealant for a casting mold.

[0034] FIG. 1 shows rail ends 1, 2 to be welded by way of an aluminothermic method, with a welding groove 3 present between their facing front sides. Marked 4, 5 are two mutually identical mold halves of a casting mold 6, which consist of the usual fireproof material, and on the outside are partially framed in a metallic sheath 7, a retaining plate.

[0035] In the assembled state of the casting mold 6, the mold halves 4, 5, of which the latter has only been shown incompletely, lie against each other in a vertical dividing plane and surround the welding groove 3 on both sides as viewed in the longitudinal direction of the rail ends 1, 2, thereby forming a casting space 8 that is bordered by the front sides of the rail ends 1, 2, and otherwise from the side and below by wall sections of the mold halves 4, 5.

[0036] The two mold halves 4, 5 are fixed to each other with means not graphically depicted in order to perform a welding operation. The aluminothermic reaction takes place in a crucible placed on the casting mold 6 (likewise not graphically depicted), ultimately yielding molten steel as the reaction product, which is introduced into the upwardly open casting mold.

[0037] The wall sections 9, 10 of both mold halves 4, 5 abutting the rail ends 1, 2 have gaps 11, 12, in which is placed a respective strip 13, 14 consisting of a thermally expandable substance, e.g., exfoliated graphite. FIG. 1 shows the respective strip 13, 14 after a completed expansion, which takes place from the outside, i.e., starting from the casting space 8. In order to reliably ensure these circumstances, gaps between the wall sections 9, 10 and the rail ends 1, 2 are designed smaller on the interior sides, i.e., the sides facing the casting space 8, than those on the exterior sides, thereby resulting in a significantly higher flow resistance toward the interior side by comparison to the exterior side. The expansion of the strips 13, 14 leads to the formation of beads 15, 16 on the exterior sides of the wall sections 9, 10, wherein a compression and a development of a reliable sealing effect by this substance comes about in the space between the rail ends 1, 2 and the gaps 11, 12 owing to the expansion, facilitated by a throttling effect as the expandable substance flows.

[0038] Functional elements on FIGS. 2 to 5 that correspond with those on FIG. 1 are correspondingly numbered, thus eliminating any need for a repeated description in this regard.

[0039] FIG. 2 shows the casting mold 6 in a state shortly before pouring molten steel, wherein 17 denotes the confluence of a side riser (not otherwise graphically depicted). As evident, the slit widths 18 between the wall sections 9, 10 and the rail ends 1, 2 have distinctly smaller dimensions toward the interior side, specifically on the side facing the casting space 8, than the slit widths 19 on the respective exterior side. In this way, a clearly preferred direction of expansion is structurally prescribed for the strips 13, 14. FIG. 2 shows the strips 13, 14 in an as yet unexpanded state.

[0040] FIG. 3 shows the casting mold 6 in a state where the expansion of the strips 13, 14 was manually initiated by means of a pyrotechnic substance 32 or an exothermally reactive substance with an ignition stick 20. The beads 15, 16 are formed and a seal is established above the slit widths 18, 19. Once this process has ended, the steel melt can be poured.

[0041] FIG. 4 shows the casting mold 6 in a state where the expansion of the strips 13, 14 starts out along a straight line. It is thermally initiated by preheating the casting space 8, which is done in a conventional manner, wherein the heat introduced in the process acts on the strips from the interior side of the casting space 8.

[0042] FIG. 5 shows the casting mold in a state where the expansion of the strips 13, 14 has concluded, so that beads 15, 16 have formed on the exterior sides of the casting mold 6, and a sufficient sealing profile has come about in the area of the slit widths 18, 19.

[0043] FIG. 6 shows a casting mold 21 that is set up for repair surface-layer welding on the railhead 22 of a rail profile 23. The casting mold 21 once again consists of two mold halves 24, 25, which are fixed on either side of the rail profile 23 in a manner not graphically depicted, for example by means of a retaining plate, and lie tightly against each other along a vertical dividing plane 26, thereby yielding an upwardly open casting space 27.

[0044] The dividing plane 26 runs in a vertical central plane of the rail profile 23, wherein both mold halves 24, 25 engage underneath the railhead 22. 28, 29 denote gaps in the mold halves, which extend underneath the railhead 22 parallel to a longitudinal rail direction, and each accommodate a strip 30, 31 made out of the same material as strips 13, 14.

[0045] In order to prepare for repair surface-layer welding, the defective area of the railhead profile is removed by grinding and/or in some other way, e.g., through ablative machining with a cutting torch, and the casting mold 21 is positioned and fixed around the exposed location of the rail profile 23.

[0046] Strips 13, 14 are intended to establish a seal on the lower side of the casting space 27, and an expansion of the strips 30, 31 is introduced in preparation for pouring steel, which can be performed in the same way as for the casting mold 6. It is important that the lower side of the casting space 27 have sealed once expansion has concluded. If necessary, a comparable sealing system can also be provided between the wall sections of the casting mold 21 and the rail profile in a vertical direction.

[0047] In a reaction crucible placed on the casting mold 21, a steel melt is produced in a known, aluminothermic manner, to which alloying elements are possibly admixed according to the material of the rails to be treated. In particular, the cast steel filled into the casting space fills out the recess of the railhead 22 produced through ablation, provided that metallurgical properties, for example with respect to hardness and strength, are produced in this region treated via surface-layer welding, in particular in a driving surface, that correspond as closely as possible to those of the remaining driving surface progression, so that no discontinuity arises in the properties owing to the surface-layer welding.

[0048] The application of the method according to the invention was introduced above with reference to a two-part casting mold 6 composed of two mold halves 4, 5. However, an application of the method is not limited to these types of casting molds, and can likewise be used in three-part casting molds, e.g., those composed of a base plate that supports the rail foot and two lateral mold parts, or even in some other multipart casting mold.

[0049] FIG. 7 shows an application for the expandable sealing compound 33, e.g., exfoliated graphite or another substance in a slit 36 to be sealed between a lower side of the rail end 1 and a surface section 35 of the casting mold 21 facing the latter.

[0050] The sealing compound 33 is integrated into a tubular enveloping body 34, which can be adhesively bonded with the surface section 35 in the initial or the delivery state. The enveloping body 34 consists of a fireproof material, e.g., a fabric, which can be elastic or inelastic.

[0051] Drawing FIG. 7 shows the sealing compound 33 in an expanded state, in which the enveloping body 34 exposed to the pressure of the sealing compound 33 firmly abuts against the mentioned lower side of the rail end 1 as well as the surface section 35, in so doing tightly sealing the slit 36. In the initial state where the sealing compound has not yet been expanded, the enveloping body is correspondingly in a relaxed state.

[0052] The above statements apply analogously with respect to a preheating and an initiation of the expansion process of the sealing compound 33.

[0053] Numerous variations of the subject matter of the application are possible; in particular, gaps are not required in all cases for receiving the sealing compound 33.

REFERENCE LIST

[0054] 1. Rail end

[0055] 2 Rail end

[0056] 3 Welding groove

[0057] 4 Welding groove

[0058] 5 Mold half

[0059] 6 Mold half

[0060] 7 Sheath

[0061] 8 Casting space

[0062] 9 Wall section

[0063] 10 Wall section

[0064] 11 Gap

[0065] 12 Gap

[0066] 13 Strip

[0067] 14 Strip

[0068] 15 Bead

[0069] 16 Bead

[0070] 17 Side riser

[0071] 18 Slit width

[0072] 19 Slit width

[0073] 20 Ignition stick

[0074] 21 Casting mold

[0075] 22 Railhead

[0076] 23 Rail profile

[0077] 24 Mold half

[0078] 25 Mold half

[0079] 26 Dividing plane

[0080] 27 Casting space

[0081] 28 Gap

[0082] 29 Gap

[0083] 30 Strip

[0084] 31 Strip

[0085] 32 Pyrotechnic substance

[0086] 33 Sealing compound

[0087] 34 Enveloping body

[0088] 35 Surface section

[0089] 36 Slit