阅读说明：本技术 用于密封铝热轨道焊接用的铸模的方法 (Method for sealing a mould for welding thermite tracks ) 是由 J·汉图施 W·安格嫩特 S·海尼格 T·雷尼克 D·麦克尔 于 2019-07-31 设计创作，主要内容包括：铸模(6)具有两个半模(4、5),所述两个半模规定用于竖立在在两个有待连接的轨道端部(1、2)之间的焊接坡口(3)的两侧,在此形成了构成轨道横截面轮廓的铸造室(8)。为了在焊接坡口(3)的两侧的轨道本体和铸模(6)的面朝这个轨道本体的壁区段(9、10)之间密封铸造室(8),在槽(11、12)中使用由至少含有膨胀石墨的物质制成的带,所述带通过热量输入在预热期间扩张并且形成了可靠的密封。与使用填充砂相比,在此产生的优点是,在铺设的轨道中作业时必然携带少得多的质量。(The casting mould (6) has two mould halves (4, 5) which are intended to stand on both sides of a welding bevel (3) between the two rail ends (1, 2) to be connected, wherein a casting chamber (8) forming the cross-sectional contour of the rail is formed. In order to seal the casting chamber (8) between the rail body on both sides of the welding groove (3) and the wall sections (9, 10) of the casting mould (6) facing this rail body, a strip made of a substance containing at least expanded graphite is used in the grooves (11, 12), said strip expanding during preheating by heat input and forming a reliable seal. The advantage of this is that, in comparison with the use of packed sand, much less mass must be carried when working in a laid track.)

1. A method for sealing a casting chamber (8, 27) of a casting mould (6, 21) for performing thermite welding at a component, the casting mould has two mould halves (4, 5; 24, 25) which are open at the upper side and imitate the contour of the component in the welding area, wherein a gap existing between the facing surfaces of the component and the wall sections (9, 10) of the casting mould (6, 21) adjacent to the surfaces of the component is closed off by a refractory sealing compound, wherein molten steel is supplied in the reaction vessel and is brought into the casting chamber (6, 21), to perform a weld provided as a rail joint weld or a repair weld, in particular a repair weld to a rail head (22), characterized in that an expandable substance is used as sealing substance, wherein the expansion can be initiated thermally or chemically, and wherein an expandable substance at least partly consisting of an expandable material is used as the expandable substance.

2. A method according to claim 1, wherein the sealing substance is contained in a groove (11, 12; 28, 29) of the mould half (4, 5; 24, 25).

3. A method according to claim 1, characterized in that the sealing substance is brought into the grooves (11, 12; 28, 29) of the mould halves (4, 5; 24, 25) in connection with the assembly of the mould halves at the respective welding points.

4. A method according to any one of claims 1 to 3, characterized in that an expandable sealing substance in the form of a moulded body is used.

5. A method according to any one of claims 1 to 3, characterized in that an expandable sealing substance in the form of a tape is used.

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

7. A method as claimed in claim 5 or 6, characterized in that the strip is fixed in a form-fitting manner in the groove (11, 12; 28, 29) of the mould halves (4, 5; 24, 25) at the location of the welding point.

8. A method according to any one of claims 1 to 4, characterized in that an expandable sealing substance in the form of a paste-like substance is used.

9. Method according to claim 8, characterized in that the pasty mass is applied in caterpillar form at the point of use thereof.

10. Method according to claim 8, characterized in that the paste-like substance is injected into the grooves (11, 12; 28, 29) of the mould halves (4, 5; 24, 25) at the location of the welding site.

11. A method according to any one of claims 1 to 4, characterized in that an expandable sealing substance in the form of loose particles is used.

12. A method according to any one of claims 16 to 11, wherein the expandable sealing substance is formed from a combination of expanded graphite and other mineral refractory materials.

13. Method according to any of claims 1 to 12, characterized in that the expansion of the sealing substance is thermally initiated by means of a pyrotechnical, exothermically reactive substance or similar heat source.

14. Method according to any of claims 1 to 12, characterized in that the expansion of the sealing substance is thermally induced by preheating of the casting mould (6, 21) before pouring the molten steel.

15. Method according to any one of claims 1 to 14, characterized in that an additional condition for providing the trough (11, 12; 28, 29) of the casting mould (6, 21) and the wall section (9, 10) of the casting mould is that the expansion of the sealing substance here takes place fulfilling a sealing function, preferably towards the outside of the casting mould.

16. Method according to any of claims 1, 4 to 6, 8, 9 and 11 to 14, characterized in that an expandable sealing substance is used to imitate the weld geometry.

Technical Field

The invention relates to a method according to the preamble of claim 1.

Background

The thermite welded connection comprises an intermediate cast structure filling the welding groove between the end sides of the rail ends to be connected, which occurs as a reaction product of a thermite fine-particle mixture composed of iron oxide and aluminum, to which specific alloying elements can be added to influence the hardness and further reactants to suppress the reaction.

Welding of the rail ends is carried out periodically with preheating, in order to obtain a uniform surface temperature of the inner wall of the casting chamber and to discharge possible moisture. The surface temperature affects the cooling speed of the molten steel and thus the casting time and the casting speed, but a temperature deviation is inevitably generated according to different thermal conductivities of the inner wall of the mold and the end side of the rail end.

Such a casting mold is known, for example, from EP0925866B1 and has two mold halves which are arranged on both sides of the rail connection to be produced and in this case symmetrically cover the welding groove. The welding bevel and the end face of the rail end to be connected and the inner wall of the mold half form a casting chamber which in its core region imitates the rail contour and into which the reaction product of the thermite reaction, i.e. the molten steel, is poured from above.

The two half moulds form an interface not only in the parting plane of the casting mould, but also on the surface of the rail ends to be thermically welded, there being a gap between the rail ends that needs to be sealed in order to avoid uncontrolled overflow of molten steel. Such seals must withstand the temperature of the molten steel during the casting process.

It is known to seal said gaps with so-called filler sands (absschmiers and filler sand), which must be carried in the form of bags each containing 25kg when working in a laid track. This sand filling must be applied manually at each welding point from the outside of the casting mould and the gap closed there, with a considerable expenditure of time. This type of seal also does not avoid interaction with the molten steel, since welding infiltration of sand may occur at the point where the filler sand comes into contact with the molten steel, which is difficult to remove later by grinding. The packed sand also often contains moisture and thus can form blisters under the influence of heat, which can lead to weld defects such as "wormholes" or cracks.

A method and a device for thermite welding are known from CH658817a5, in which a casting mold has two mold halves which are provided with a sealing compound on their contact surfaces, wherein the mold halves are closed tightly with a pressure device which is firmly tensioned.

In addition to rail joint welding, the problem of sealing the casting chamber also arises in rail head repair or build-up welding and other welding performed aluminothermally.

A method for producing core sand and/or molding sand for foundry purposes is known from WO2014/106646a1, in which a mineral molding base material with a binder consisting of water glass and expanded graphite is used. With such a binder mixture, it should be possible to facilitate the coring and at the same time improve the surface quality of the cast bodies produced.

This known technique of establishing a seal of the casting mould is therefore not technically considered to be optimal, it is time-consuming, labour-intensive and laborious to perform in practice when working in a laid track, since a large number of auxiliary devices must be carried. The achievable work result in this case is furthermore dependent on the experience and the level of detail of the respective welder.

Disclosure of Invention

The object of the invention is to design a casting mold for thermite welding of the type mentioned at the beginning with a view to a simpler construction of the seal of the casting chamber. In such a mold, this object is achieved by the features of the characterizing part of claim 1.

It is therefore important to the invention that mineral or carbon-containing, refractory, thermally or chemically expandable sealing substances be used instead of the filler sand used hitherto. This is based on the idea of positioning the substance in a gap which is bounded on one side by the surfaces of the rail body or generally of two workpieces to be welded and on the other side by the wall sections of the mold halves. The thermal or chemically induced expansion of the sealing compound fills or fills the gap, the sealing compound being under pressure in the gap and in this way forming a closure structure which reliably seals the gap. Under thermally induced expansion, the filled or combined liquid evaporates as a result of the heat input, wherein expansion of the sealing compound occurs on account of the accompanying volume enlargement. In this connection, for example, hydrates, carbonates or nitrates can be used, which release hydrogen, carbon dioxide or nitrogen. Under chemically induced expansion, the chemical reaction results in the release of a gas or vapor that contributes to the expansion of the sealing substance. Since the sealing compound is thus expandable, the advantage results that, during the work in the laid track, a much smaller mass than the filling sand known for this purpose must be carried along. After the sealing substances have developed their own sealing action on account of expansion after the correct application of these sealing substances, the necessary level of care for sealing the casting mold is set and the time and effort associated therewith is likewise reduced. After the process of applying the sealing substance is simplified, the reliance on the sophistication and experience of the welder involved in these operations is reduced. Another advantage is that the risk of moisture that would otherwise not be excluded when using packed sand entering the mould casting chamber is eliminated.

The expandable mass intended for sealing can be used, similarly to the use of the filling sand known hitherto for this purpose, also outside the casting mold, i.e. next to the actual weld bead or weld bead, without contacting this weld bead. In this connection, the gap between the rail body and the face of the casting mold facing this rail body is sealed. Advantages associated with the use of such a substance as a sealing substance are also provided in this connection.

The field of application of the casting mould equipped according to the invention relates to rail joint welding or repair welding. The latter normally involves wear-induced wear of the rail head, in particular rail defects such as collapse, squeal (belgrasspi), dents, fractures and sideslip points. In such repair welding, the damaged portion of the rail head is first removed and the resulting recess is subsequently filled up by build-up welding. In this case, the important properties of the rail body are to be changed stably at the welding point. In addition to rail joint welding, the present invention may also be used in the welding of other workpieces, where thermite welding is often used.

As expandable sealing substance an expandable substance or a substance at least comprising an expandable component is used. Such an expandable substance may for example be expanded graphite. The expansion of expanded graphite, which can be triggered by an increase in temperature, is known but has hitherto only been used as flame protection, i.e. for preventing the spread of combustion, as oxidation protection in metallurgy and in the chemical industry in connection with paints and pigments. The expanded graphite meets all the requirements set forth for sealing substances that must be met in a mould for thermite welding processes. In this connection, vermiculite, mineral materials, in particular siliceous materials, are considered as further mineral substances, from which expanding water vapor is released by heat input.

The expanded graphite can in this connection be used alone or in combination with other mineral materials.

The features of claims 2 and 3 are directed to an alternative way of using an expandable sealing substance. Such a sealing substance can be used directly in the groove of the mold halves and in this state be provided at the welding site. This means that the mould halves and the sealing substance can be brought together at their place of use. The sealing compound can, however, also be initially introduced into the groove of the mold half at the respective point of use. This means that the mold halves and the sealing substance are brought apart from one another to their place of use.

According to the features of claim 4, sealing substances, such as expanded graphite, can be used as molded bodies, wherein the production takes place by means of an extrusion process.

According to the features of claims 5 to 7, sealing substances in the form of tapes, in particular self-adhesive tapes, are used. The advantage that follows is the flexible mounting at the contour of the mold halves or rail bodies. The strip can be fixed in these grooves in a form-fitting manner if corresponding structural precautions are present at the mold halves, for example in the form of grooves.

According to the features of claims 8 to 10, a sealing substance in the form of a paste-like substance is used, which is applied or injected at its point of use in the form of an injection track into the groove of the respective mold half. The sealing substance can in this case be brought to the place of use in the glue cartridge.

The features of claims 11 and 12 are directed to further variants of the use of expanded graphite. The expanded graphite is used in the form of loose particles, which are mixed with other mineral refractory materials in order to modify their properties. The material mixture combined in this way can then be used as an expandable sealing substance.

The features of claims 13 and 14 are directed to different variants for initiating the expansion process of the expandable sealing substance. This process can be initiated using a substance which reacts exothermically and can thus be triggered by means of the ignition rod, so that the expansion process is started. However, the expansion can also be triggered directly by preheating the casting mold. In any case, sufficient heat introduction into the sealing substance is involved here, so that other techniques, which are also familiar to the person skilled in the art, are also suitable.

The features of claim 15 are directed to the shaping of the casting mould adapted to the expansion process of the sealing compound. It is important here to prevent the expansion of this substance contained in the groove in the direction of the casting chamber. At the same time, the expansion process inevitably produces a pressure in the groove formed in the wall section of the casting mold, which is sufficient to produce a reliable sealing effect in the gap between the rail body and the wall section of the casting mold opposite this rail body. This can be achieved, for example, by different inner and outer gap widths, so that correspondingly different outflow resistances are exhibited for the expanding sealing compound and the inward outflow is at least strongly impeded in any case.

The features of claim 16 are directed to a special use of the expandable sealing substance. This sealing compound produces a sealing effect here in the case of direct contact with the weld bead.

It is recognized that the method according to the invention makes it possible to provide a simple and rapid sealing of the casting chamber of the casting mold to be used in the thermite process, to be precise with less work effort than in the methods proposed in the prior art at the outset and in a reproducible manner independent of the experience and the level of detail of the respective welder.

Drawings

The invention is explained in more detail below with reference to the figures. In the figure:

fig. 1 shows a perspective view of a casting mould according to the invention in a partial sectional view;

FIG. 2 is a plan sectional view of the casting mold half according to FIG. 1 in an initial state;

FIG. 3 is a plan sectional view of the casting mold half according to FIG. 2 at the point in time when the expanded graphite begins to expand;

FIG. 4 is a plan sectional view of the casting mold half according to FIG. 2 at the point in time when expansion of the expanded graphite begins during initiation of the expansion process by preheating;

FIG. 5 is a plan sectional view of the casting mold half according to FIG. 2 at the point in time when the expansion of the expanded graphite is completed;

FIG. 6 is a plan cross-sectional view of a mold prepared for repair weld build-up in the rail area;

fig. 7 is a plan partial sectional view of using expanded graphite in a mold in a band shape as a sealing device.

Detailed Description

Fig. 1 shows two rail ends 1, 2 to be welded by a thermite process, with a welding bevel 3 between their facing end sides. Two mutually identical mold halves of the casting mold 6, which are made of a conventional refractory material and which engage at the outer side in a metallic jacket 7, i.e. a retaining plate, are designated by the reference numerals 4, 5.

In the assembled state of the casting mold 6, the mold halves 4, 5, which are only shown in fragmentary form, are juxtaposed to one another in a vertical parting plane and, viewed in the longitudinal direction of the rail ends 1, 2, surround the welding bevel 3 on both sides, forming a casting chamber 8 which is delimited by the end sides of the rail ends 1, 2 and, furthermore, laterally and at the bottom by wall sections of the mold halves 4, 5.

The two mould halves 4, 5 are fastened to each other by means not shown in the figures in order to perform welding. In a crucible, which is also not shown in the drawing and is placed on the casting mold 6, a thermite reaction takes place, and molten steel is finally produced as a reaction product of the thermite reaction and is introduced into the casting mold, which is open at the top.

The two mold halves 4, 5 have grooves 11, 12 in their wall sections 9, 10 which bear against the rail ends 1, 2, in which grooves corresponding bands 13, 14 of a thermally expandable substance, for example expanded graphite, are inserted. Fig. 1 shows the respective belts 13, 14 after expansion, which takes place towards the outside and thus away from the casting chamber 8. In order to ensure this, the gap between the wall sections 9, 10 and the rail ends 1, 2 is designed to be smaller on the inside, i.e. on the side facing the casting chamber 8, than on the outside, so that a much greater flow resistance is generated towards the inside than towards the outside. The expansion of the strips 13, 14 results in the formation of bulges 15, 16 on the outer side of the wall sections 9, 10, wherein in the space between the rail ends 1, 2 and the grooves 11, 12 a seal is produced as a result of the expansion (which is promoted by the throttling effect during the flow of the expandable substance) and a reliable sealing effect is produced by this substance.

Functional elements corresponding to those in fig. 1 are correspondingly labeled in fig. 2 to 5, and thus, a repetitive description thereof may be omitted.

Fig. 2 shows the casting mold 6 in a state shortly before the pouring of the molten steel, wherein the inlet opening of the side riser, which is not shown in the figures, is marked with reference numeral 17. It is recognized that the gap width 18 between the wall sections 9, 10 and the rail ends 1, 2 is significantly smaller towards the inside, i.e. on the side facing the casting chamber 8, than the gap width 19 on the respective outside. In this way, a clearly preferred expansion direction of the bands 13, 14 is predetermined in terms of the structural design. Fig. 2 shows the bands 13, 14 in a not yet expanded state.

Fig. 3 shows the casting mould 6 in the state in which the bands 13, 14 are manually expanded by means of a pyrotechnic substance 32 or an exothermically reactive substance with an ignition rod 20. Ridges 15, 16 are formed and a seal across gap widths 18, 19 is established. After this process is finished, the pouring of the molten steel may be performed.

Fig. 4 shows the casting mould 6 in a state where the strips 13, 14 just start to expand. The expansion is thermally induced by preheating of the casting chamber 8, which is effected in a conventional manner, the heat introduced here acting on the strip from the inside of the casting chamber 8.

Fig. 5 shows the casting mold 6 in the state in which the strips 13, 14 have ended expanding, so that the bulges 15, 16 have been formed on the outer side of the casting mold 6 and a sufficient sealing contour has been produced in the region of the gap widths 18, 19.

Fig. 6 shows a mold 21, which is provided for repair welding on a rail head 22 of a rail profile 23. The casting mold 21 in turn has two mold halves 24, 25 which are fastened on both sides of the rail profile 23, for example by means of holding plates, not shown in the drawing, and are placed together in a sealed manner along a vertical parting plane 26, in this case a casting chamber 27 which is open on the upper side being shown.

The mold parting plane 26 extends in the vertical center plane of the rail contour 23, wherein the two mold halves 24, 25 engage the rail head 22 from below. The grooves in the mold halves are designated by reference numerals 28, 29, which extend longitudinally parallel to the rail below the rail head 22 and accommodate the strips 30, 31, respectively, which are made of the same material as the strips 13, 14.

In preparation for repair welding, the damaged region of the rail head contour is removed by grinding and/or other means, for example by machining by means of torch ablation, and the mold 21 is positioned and fixed around the exposed region of the rail contour 23.

The belts 13, 14 are intended to establish a seal against the underside of the casting chamber 27 and to introduce an expansion of the belts 30, 31 in preparation for the steel pouring, which can be performed in the same way as in the casting mould 6. It is important that the underside of the casting chamber 27 is already sealed after the expansion has ended. A similar sealing system may also be provided in the vertical direction between the wall section of the casting mould 21 and the track profile, if desired.

In a reaction crucible placed on the casting mould 21, molten steel is supplied in a manner known per se by thermite process, which molten steel optionally incorporates alloying elements in accordance with the material of the rail to be treated. The cast steel introduced into the casting chamber fills or fills in particular the recesses of the rail head 22 produced by erosion with the additional condition that metallurgical properties, for example with respect to hardness and strength, which correspond as far as possible to the metallurgical properties of the remaining running surface, are provided in this region treated by the weld deposit, in particular in the running surface, so that no discontinuities are produced in the property changes by the weld deposit.

The use of the method according to the invention is described above with reference to a casting mould 6 which is composed of two parts, i.e. two half-moulds 4, 5. The use of the method is not limited to this type of casting mold and can be used at the same time in a three-part casting mold, for example, assembled from a base plate supporting the rail foot and two lateral molded parts, or also in other multi-part casting molds.

Fig. 7 shows the use of an expandable sealing compound 33, for example expanded graphite or another compound, in the gap 36 to be sealed between the underside of the rail end 1 and the surface section 35 of the casting mold 21 facing this underside.

The sealing compound 33 is integrated into a tubular casing 34, which can be bonded to the surface portion 35 in the initial state or also in the delivery state. The envelope 34 is of a fire-resistant material, for example a fabric which may be elastic or also inelastic.

Fig. 7 shows the sealing compound 33 in the expanded state, in which the envelope 34 rests firmly against the underside of the rail end 1 and against the surface portion 35 under the pressure of the sealing compound 33, thereby sealing off the gap 36. In the initial state, in which the sealing compound has not yet expanded, the encapsulation is accordingly present in a relaxed state.

The foregoing explanation similarly applies with respect to the preheating and initiation of the expansion process of the sealing substance 33.

A large number of variants of the solution according to the application are possible, in particular not all cases requiring a groove for receiving the sealing substance 33.

List of reference numerals:

1 end of rail

2 track end

3 welding groove

4 half mould

5 half mould

6 casting mould

7 protective sleeve

8 casting chamber

9 wall section

10-wall section

11 groove

12 groove

13 strap

14 belt

15 raised part

16 raised part

17 side riser

18 gap width

19 gap width

20 ignition rod

21 mould

22 rail head

23 track profile

24 mould half

25 half mould

26 split plane

27 casting chamber

28 groove

29 groove

30 belt

31 band

32 pyrotechnic substance

33 sealing material

34 envelope body

35 surface section

36 gap