AU9707298A

AU9707298A - Mould for the welding of two rail ends

Info

Publication number: AU9707298A
Application number: AU97072/98A
Authority: AU
Inventors: Michael Steinhorst
Original assignee: Elektro Thermit GmbH
Current assignee: Elektro Thermit GmbH and Co KG
Priority date: 1997-12-13
Filing date: 1998-12-11
Publication date: 1999-07-01
Anticipated expiration: 2018-12-11
Also published as: NO984976L; EP0925866A2; ATE224255T1; NO984976D0; JPH11245056A; AU748348B2; DE59805600D1; EP0925866A3; EP0925866B1

Abstract

The mold, for casting an intermediate rail section, has risers (25) for the head sides with the under side cross section surfaces at the lower edges of the head flanks of the rail head (8). The risers extend upwards from the edges to give an entry cross section at the risers into the molding zone, according to the thickness of the rail web (7), to meet the expression 0.6 hL ≤ A ≤ 3.75 hL, where h is the height of the rail head, L the width of the welded joint and A the surface of the entry opening cross section.

Description

S F Ref: 441417

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Elektro-Thermit GmbH Gerlingstrasse D-45139 Essen

GERMANY

Michael Steinhorst Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Mould for the Welding of Two Rail Ends The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845 Mould for the Welding of Two Rail Ends The invention relates to a mould for the welding of two rail ends, consisting of mould walls matched to the rail profile, covering the welding groove present between the rail ends and made of a refractory material, the casting space to be filled by the weld being delimited otherwise by the end faces of the rail ends, and at least one system of foot risers and/or head risers and head side risers being moulded into the mould walls, wherein the area of the opening cross section of a head side riser on the casting space side adjoins the lower edge of the head flank of the rail head and extends upward starting from there, the area is dimensioned in accordance with the thickness of the rail web and also as a function of the height of the rail head and the width of the welding groove, with 0.6 hL<A-3.75 hL, and the head riser has a shape tapering in the direction of the rail head.

The joining of two rail ends by welding is known, for example in the form of aluminothermic welding. It is based on the highly exothermic reaction of iron oxides with aluminium, in the course of which the iron oxides are reduced, the iron is produced in molten superheated form and a slag essentially consisting of alumina floats on the melt, the molten iron subsequently being introduced into the welding groove between the rail ends. The starting materials of this reaction are in the form of a fine-grained mixture which essentially consists of iron oxide and aluminium and to which certain alloy elements, such as, for example, C, Mn etc., which determine, inter alia, the hardness of the intercast microstructure, and scrap iron are added in order to dampen the reaction.

Aluminothermic welding is carried out using a mould which regularly consists of two mould halves which are placed to the side of the rail ends around the welding groove at the mutual distance of the end faces and are held together by mould-holding plates. Onto the top of this mould, a reaction crucible is placed into which the aluminothermic mixture is introduced, whereupon the reduction process is initiated in a suitable manner, for example by means of a small pilot rod. After the conclusion of the reaction generally under time control via an automatic crucible plug the molten steel is introduced into the mould for the purpose of carrying out the welding.

Usually, welding is carried out with preheating of the rail ends to be joined. This measure serves, on the one hand, to expel any moisture which may be present in the casting space. On the other hand, it serves to establish extremely homogeneous surface temperatures of the walls of the casting space, in particular of the end faces of the rail ends to be welded, which are superficially fused during the welding, this heat having to be supplied essentially by the molten steel, that is to say via the aluminothermic reaction.

The molten steel introduced into the casting space is intended to fill the latter in accordance with a defined casting rate or casting time, which is determined, inter alia, by the heat outflow conditions, in particular the cooling rates in the region of the walls of the mould. In accordance with the differing thermal conductivities of the mould walls on the one hand and the rail body on the other hand, influenced to a lesser extent also by weather conditions, a corresponding temperature field forms in the edge regions of the melt, corresponding to these locally differing heat removal rates and associated cooling rates. This temperature field in turn determines the crystallisation process.

CO4265 The solidification of molten metals usually goes hand in hand with a volume contraction, so that, as a function of the local progress of the crystallisation process, in particular the local solidification, a formation of sink holes can occur. Sink holes always appear when molten areas of the steel are surrounded by already solidified areas, so that the internal molten areas are still subject to a volume contraction which has already been concluded in the outer areas. Sink hole formation thus follows a temperature field which is characterised in edge regions by temperatures lower than those in core regions.

To avoid the formation of sink holes, the mould is provided with a system of risers and/or feeders which communicate, for example, with the region of the rail foot and of the rail head. These risers form a reservoir for molten metal on the one hand and heat on the other hand. The influence of the risers on the crystallisation process comprises the introduction of molten steel into critical zones of the weld microstructure for the purpose of compensating for volume contraction and at the same time the supply of further heat by this introduction of molten steel. This requires the establishment of a temperature field aimed at avoiding the inclusion of molten areas.

DE-C-196 20 374 discloses a generic mould for the welding of two rail ends. This is provided in the region of the rail foot with a system of foot risers and air channels which communicate on both sides of the rail ends with the rail foot, namely in an area distribution which is symmetrical relative to a central transverse plane. By means of such a riser system, associated with the rail foot, the formation of shrinkage holes in the transition region from the rail foot to the web of the rail can be effectively avoided.

It is also known to associate the rail head with a head riser which communicates directly with at least the upper region of the rail head. It is also known to fit an overflow, also called head side riser, above the rail head in the mould wall. The purpose of this head riser system is to supply more molten metal and heat into the relatively massive rail head during the solidification process in order to achieve a preferably upward-directed solidification which avoids inclusion of liquid areas.

It has been found, however, that even this does not always prevent the formation of shrinkage holes, especially in the extremely critical transition region between the relatively low-mass web of the rail and the rail head.

The object of the invention is accordingly to design a mould of the type described at the outset in such a way that formation of shrinkage holes, especially in the transition region between the web of the rail and the rail head, is suppressed in a simple but effective manner and a smooth reaction is made possible. In such a mould, this object is achieved by a mould for the welding of two rail ends, consisting of mould walls matched to the rail profile, covering the welding groove present between the rail ends and made of a refractory material, the casting space to be filled by the weld being delimited otherwise by the end faces of the rail ends, and at least one system of foot risers and/or head risers and head side risers being moulded into the mould walls, wherein the area of the opening cross section of a head side riser on the casting space side adjoins the lower edge of the head flank of the rail head and extends upward starting from there, CO4265 the area is dimensioned in accordance with the thickness of the rail web and also as a function of the height of the rail head and the width of the welding groove, with 0.6 hL<A-3.75 hL, and the head riser has a shape tapering in the direction of the rail head.

This object is also achieved by a mould for the welding of two rail ends, consisting of mould walls matched to the rail profile, covering the welding groove present between the rail ends and made of a refractory material, the casting space to be filled by the weld being delimited otherwise by the end faces of the rail ends, and at least one system of foot risers and/or head risers and/or head side risers being moulded into the mould walls, wherein the width of the head riser is dimensioned in accordance with the width of the rail head, the height of the head riser is dimensioned in accordance with the height of the rail head, the inner walls of the head riser as viewed in the projection of a cross sectional plane of the rail ends form, with the head flanks of the rail head, cross sections which each taper in the direction of the rail foot between an upper side width and an underside width the dimension being within the range from 0.001 b to 0.1 b and the dimension being within the range from 1.01 x to 5 x.

A first measure, essential to the invention, comprises arranging the head side riser in such a way that the cross section thereof as it opens into the casting space directly adjoins the lower edge of the head flank of the rail head and extends upward starting from this edge. The cross section of the head side riser can in principle have any desired form it is placed, moreover, preferably symmetrically with respect to a central transverse plane of the welding groove. The head side riser freely communicates with the foot risers, so that, in the immediate vicinity of the lower edge of the head flank, there is large-area contact with the rail head, in accordance with the absolute magnitude of the cross section of the head side riser. This means that premature solidification of edge zones of the rail head, especially in the lower critical transition region, is effectively suppressed, since more molten steel and heat are supplied at this point. The rail head is thus subjected at the top and in the region of the head flanks to intensive influence by riser systems, so that the result is directed solidification occurring from the bottom upward within the rail head volume. A further measure according to the invention concerns the dimensioning of the area of the opening cross section of a head side riser. The effect exerted by the head side riser depends quantitatively, inter alia, on the mass of the molten steel solidifying in the casting space and thus on the width of the welding groove and on the height of the rail head. These two influencing parameters, namely the height of the rail head and the width of the welding groove, determine the influence of the volume of the rail head and the heat retention capacity, which can be at least qualitatively represented thereby and which determines the spread of temperature fields and crystallisation fronts with time. A further parameter which influences the cited effect is the thickness of the rail web. A further measure according to the invention comprises the design of the head riser, which, overall, has a shape which tapers conically in the direction of the rail head. This measure leads globally to a transfer of material and heat, concentrated toward the rail head. If the head riser is used for the introduction of the molten steel into the mould, it is also possible, by appropriate dimensioning of the conicity, to ensure that the distance CO4265 within which the melt falls freely is relatively short, so that a contribution to orderly flow control can be made in this way. By dimensioning the area of the opening cross section of the head side riser in accordance with the thickness of the rail web within the range indicated, the formation of shrinkage holes in the transition region between the web of the rail and the rail head can be effectively suppressed by the totality of these measures.

The cited area of the opening cross section has a rectangular or square shape and is characterised by sides a and b wherein one side of the area extends parallel to the bottom side of the rail foot and the other side extends perpendicular to the side and the sides are dimensioned in accordance with the thickness of the rail web, with 0.6 hasl1.5 h and/or with L5b<2.5 L. This is a particularly advantageous design of the cross section.

In the case of thicknesses of the rail web with ss13mm, the area is preferably dimensioned according to 0.75 hL<A<3.75 hL; the sides are preferably dimensioned according to 0.75 h5as1.5 h and/or according to Lb:s2.5 L.

In the case of thicknesses of the rail web with s 13mm, the area is preferably S1 dimensioned according to 0.6 hL-A<3.75 hL; the sides are dimensioned according to 0.6 h5a-1.5 h and/or according to L5b<2.5 L.

In the case of thicknesses of the rail web with s<l3mm, the area is preferably dimensioned according to 1.125 hL<A3.0375 hL; the sides are preferably dimensioned with 0.9 h5a<1.35 h and/or according to 1.25 L5b<2.25 L.

In the case of thicknesses of the rail web with s 13mm, the area is preferably dimensioned according to 0.875 hL<A<2.8125 hL; the sides are preferably dimensioned with 0.7 hsa<1.25 h and/or according to 1.25 L5b<2.25

L.

In the case of thicknesses of the rail web with s<13mm, the area is preferably dimensioned according to 1.575 hL<A<2.4 hL; the sides are preferably dimensioned with 1.05 hal51.2 h and/or 1.5 L5b<2.0 L.

In the case of thicknesses of the rail web with s 13mm, the area is preferably dimensioned according to 1.2 hL<A<2.0 hL; the sides are preferably dimensioned with 0.8 h-a51.0 h and/or according to 1.5 L5b<2.0 L.

The features of above are as a function of the absolute thickness of the web of the rail directed to the more precise definition of the area A of the opening cross section and/or the lengths of the sides a and b. If the area A and/or the sides a, b are dimensioned within the indicated ranges according to the invention, the result is the abovementioned effect that the formation of shrinkage holes in the transition region between the web of the rail and the rail head is effectively countered.

In the case of thicknesses of the rail web with 9mmsl13mm, the width of the head riser (24) is preferably dimensioned in accordance with the width of the rail head with 1.2 bB<8 b, b, or 1.8 b-B<3.5 b.

It is preferred that the height of the head riser is dimensioned in accordance with the height of the rail head with 2 h-Hs20 h, 2.5 h<H<10 h, or 3 h<H<8 h.

C04265 In the case of thicknesses of the rail web with s 13mm, the width of the head riser is dimensioned in accordance with the width of the rail head with 1.2 b<B<8 b, 1.5 b<B<5 b, or 1.8 b5B<4 b.

It is preferred that the height of the head riser is dimensioned in accordance with of the height of the rail head with 3 h<H<25 h, 3 h<H<15 h, or 3 h<H<10 h.

The features of above are directed to the further refinement of the head riser. The geometry of the head riser is defined by a plurality of parameters, which in turn are functionally dependent on the geometrical sizes of the rail profile. In detail, these are the parameter H, namely the height of the head riser, B, namely the width of the head riser, and the measurements x and y which define the width and the geometry of the gaps existing on both sides of the head flanks and determined by the facing walls of the mould, which gaps form parts of the head riser laterally surrounding the rail head. The selection of this parameter constellation in accordance with the above ranges also contributes, within the intention of the stated object, to the achievement of an upwardly-directed progressive solidification of the melt while avoiding shrinkage holes, in particular in the transition region between the web of the rail and the rail head.

A mould which comprises a mould attachment which is destined to receive, inter alia, a reaction crucible and consists of a refractory material, preferably having a higher heat-insulation capacity than that of the other mould walls has the aim of achieving a smooth reaction after the ignition of the aluminothermic mixture. For this purpose, a mould attachment is provided which prevents a premature heat loss, so that overall a lowering of the casting temperature is made possible, without resulting in disadvantageous consequences for the quality of the weld. As is known, the exothermic reaction after the ignition of the aluminothermic mixture results in the formation of a superheated steel at temperatures of above 2000 0 C, with vigorous evolution of gas and/or smoke beginning, inter alia, due to burning carbon, and this is connected with an emergence of flames from the reaction crucible and also an ejection of steel. This reaction profile is felt to be undesirable in the light of an enhanced awareness of the environment and leads to the demand for measures to slow down the reaction.

Although it is known to slow down the reaction by the addition of heat-absorbing elements, for example scrap iron, this is in general questionable because of the resulting lowering of the temperature of the molten steel, with regard to the total heat losses to be expected and an unacceptable lowering of the casting temperature. However, by limiting the heat losses during the aluminothermic reaction according to the invention, namely by using said mould attachment, which can either be an integral constituent of the mould or a component separate from the latter, it is possible to work at a lower casting temperature, so that the interests of environmental protection also taken into account by the mould according to the invention. The mould attachment can consist of a refractory material based on zirconium dioxide but in view of the costs to be expected, it is preferably formed from a material based on quartz sand.

In a preferred mould according to the invention, the angle of inclination has a value at the upper end and a value at the lower end, in particular at the upper end and a value (13) at the point of the head side riser, and CO4265 the angle of inclination (13) and the angle of inclination are dimensioned in accordance with the relationship 13 z a, the sum of the angles of inclination (a 13) being in accordance with the relationship 150_(a 13)<89-, the sum of the angles of inclination (a 13) being, furthermore, (a 13) a and the parameter corresponding to a value of between 0.01 and 4.93 in accordance with the angle of inclination For an angle of inclination with a<60 0 the parameter is preferably selected to be within the range 0.01<z<0.48.

For an angle of inclination with a<45 0 the parameter is preferably selected to be within the range 0.02<z<0.98.

For an angle of inclination with a<30 0 the parameter is preferably selected to be within the range 0.03<z51.96.

For an angle of inclination with a520 0 the parameter is preferably selected to be within the range 0.05<z<3.45.

For an angle of inclination with a<150, the parameter is preferably selected to be within the range 0.06<z<4.93.

It is preferred that the inner walls of the head riser, starting with the upper end are composed of at least two successive sections of planar shape, the angle of inclination corresponding to the angle of inclination of the upper section starting at the end, and the angle of inclination (13) corresponding to the angle of inclination of the lower section ending in the region of the head side riser.

It is further preferred that the inner walls of the head riser have, between the upper end thereof characterised by the angle of inclination and the lower end, in the region of the head side riser, in particular the point thereof, characterised by the angle of inclination a steadily curved shape of the area, which, in particular, is concave toward the inside of the head riser.

The features above are directed to the further refinement of the inner walls of the head riser, namely between the upper open end and the region of the head side risers. The aim is globally inward-directed flow control of the molten steel, ie. in the direction of a central plane of the rail ends to be joined, in particular with the object of supplying both more steel and more heat to the critical transition region between the -rail head and web of the rail, in order to avoid an occurrence of shrinkage holes here. The inner walls can be continuously curved between said upper and lower ends this shape can, however, also be approximated by at least two flat sections. The indicated ranges of the angles of inclination a and 13 in accordance with the designated parameter z have proven to be particularly advantageous in this connection.

While adhering to the intended purpose of the inner walls, numerous modifications are possible.

Thus, this especially includes continuous transitions of inclination relative to the wall sections adjoining said sections. The aim in every case is a smoothed flow of the steel.

The invention will be explained in more detail below with reference to the illustrative embodiment diagrammatically reproduced in the drawings, in which: C04265 Fig. 1 shows a cross section of a rail joint produced by welding, corresponding to section plane I-I in Fig. 2; Fig. 2 shows a partial horizontal section of a rail joint corresponding to section plane I1-11 in Fig.

1; Fig. 3 shows a cross section of a mould according to the invention surrounding the rail ends to be joined in the weld region; Fig. 4 shows a side view of the weld region of two rail ends welded to one another, with an additional representation of the projection area of the cross section of the head side riser; Fig. 5 shows a cross section of another mould according to the invention surrounding the rail ends to be joined in the weld region; Fig. 6 shows an enlarged partial representation of a mould according to the invention in the region of the walls of the head riser.

1, 2 in Figures 1 and 2 of the drawing mark two rail ends which have been welded to one another and whose joint region is characterised by a weld reinforcement 3 of width W. The weld 'is reinforcement 3 covers, symmetrically relative to a transverse central plane 5, the welding groove 4 of width L, existing between the rail ends 1, 2, and otherwise has a shape which bulges out of the surfaces of the mutually aligned rail ends 1, 2 and essentially completely surrounds the welding groove 4.

The rail body in each case consists of a rail foot 6 destined for placement, for example, on sleepers, which are not reproduced in the drawing, a rail web 7 extending perpendicular thereto and S merging into a rail head 8. The rail profile consisting of these three sections has a structure which is symmetrical ab6ut a central vertical plane 9.

Between the rail foot 6 and the web 7 of the rail on the one hand and the web 7 of the rail and the rail head 8 on the other hand, there are in each case rounded transition sections, so that the distance between the vertex 10 of the rail head 8 and the point of intersection 11 of two tangents laid against the undersides of the rail head profile corresponds to the vertex height hk of the rail head 8 as viewed in the plane of the drawing in Figure 1 the points 10 and 11 being located on the track of the central plane 9 because of the symmetry properties of the rail profile. The web height hs is defined by the distance between said point of intersection 11 and a point of intersection 12 of two tangents laid against the upper sides of the profile of the rail foot 6, which point of intersection again is located on said track of the central plane 9. Finally, the foot height hf results as the distance between the point of intersection 12 and the flat underside 13 of the rail foot.

The rail head height h again as viewed in the plane of the drawing in Figure 1 is defined as the vertical distance between the vertex 10 and that point of the head flanks 14 from which the contour per se of the head flank extends inward, that is to say in the direction of the central plane 9.

The web width s is defined as the value of the web. thickness at the narrowest point of the web, that is to say approximately in a central region of the web height hs.

Finally, the width b of the rail head is defined as the horizontal width of the rail head 8 at its widest point.

C04265 Below, reference is made to Figures 3 and 4 in the drawing, wherein elements identical with those of Figures 1 and 2 are numbered correspondingly.

Figure 3 shows a cross sectional representation of the mould 15 according to the invention, which has a symmetrical structure relative to the central vertical plane 9 and globally consists of two mould halves 15', 15", which laterally, symmetrically covering the welding groove, surround the rail ends 1, 2 which are to be joined. The mould halves consist of refractory material, for example water glass-bound quartz sand, and the casting space delimited by the end faces of the rail ends 1, 2, at a distance given by the welding groove, and otherwise by the walls of the mould, is sealed off from the rail profile by refractory sand.

The mould halves 15', 15" are held together by mould-holding plates which are not reproduced in the drawing.

Likewise not illustrated in the drawing is the reaction crucible, which initially is closed at the underside by a plug and into which the aluminothermic mixture is introduced and in which the reaction required for providing molten steel takes place. Molten steel enters the mould at the point 16 from this 1is reaction crucible, which is placed on top of the mould.

17 denotes foot risers, which, at their lower end, open into the casting space in the region of the rail foot 6. The foot risers 17 extend at an angle and symmetrically to the track of the central plane 9.

18 denotes air channels, whose lower ends likewise open into the casting space in the region of the rail foot. The air channels 18 extend substantially parallel to the foot risers 17, namely at the outermost edge regions of the rail foot 6.

The distribution, relative to the surface of the rail foot 6, of the foot risers 17 and air channels 18 is accomplished preferably in such a way that the cardinal point of the area of the cross section of each foot riser 17 is located in the central transverse plane 5 of the welding groove and that, for example, two air channels are provided on one side of the rail profile, in particular with the proviso that the cardinal points of the area of these two air channels are located on both sides of the central transverse plane 5 and that a symmetrical area distribution of these air channels relative to this central transverse plane applies.

19 denotes a diverting plug, which is inserted into the mould from the top and which is formed from a refractory material corresponding to the mould and whose purpose is to distribute the molten steel introduced into the mould from the top in the direction of the arrow 20, uniformly in the direction of the arrows 21 and to introduce it into the casting space delimited by the end faces of the rail ends 1,2, the inner walls 22 and the mould walls 28. The head riser 24 extends between the inner walls 22 of the mould, oriented conically inward in the direction of the welding groove and thus toward the underside. The side walls 23 of the diverting plug 19 extend approximately parallel to the inner walls 22.

denotes head side risers which extend substantially horizontally, starting from the casting space, and freely communicate with the already mentioned foot risers 17. The profile of the welding reinforcement 3 is moulded into the underside of the cross section of the head side risers 25. The axes of the two head side risers 25 can have a slight inclination toward the inside of the welding groove. Otherwise, the head side risers 25 are disregarding the profile part of the welding C04265 reinforcement at the underside placed in such a way that as viewed in the plane of the drawing in Figure 3 the extension of the lower edges 26 meets the head flank 14 of the rail head 8 at the lower edge thereof, which is adjoined by the flank sections thereof, oriented inward toward the central plane 9.

The conicity of the inner walls 22 is, relative to the lateral delimitation of the diverting plug 19, dimensioned in such a way that molten steel, flowing in the direction of the arrows 21, thus flows inward along the inner walls 22 and in this way is guided past the opening cross sections 27 of the head side risers 25 in the direction of the mould walls 28 of the mould 15. Free fall of the molten steel, starting from the outer edges 29 of the diverting plugs 19 up to the mould walls 28, is thus precluded for geometrical reasons, so that there is unambiguous flow control.

As shown especially by Figure 4, the head side riser 25 has, in the preferred embodiment shown in this figure in the drawing, a rectangular cross sectional shape, namely with a height a perpendicular to the plane of the underside 13 of the rail ends and with a width b in the horizontal direction, and thus parallel to said underside 13. The cross sectional area A characterised by the is height a and the width b is the cross sectional area of the head side riser 25 in the vertical plane shown in Figure 3, whose spatial orientation corresponds to an inside vertical plane which extends parallel to the central plane 9 and is tangent upon the mould wall 28' in the region of the upper circumferential edge 28" of the head side riser In the illustrative embodiment shown, the width measurement b corresponds to the width W of the welding reinforcement 3, and the head riser 24 is in other respects arranged in such a way that the width L of the welding groove 4 is covered symmetrically relative to the central transverse plane Another characteristic is that the height dimension a corresponds merely to a part of the height dimension h of the head height. Finally, it is essential that the lower edge 26 of the cross sectional area of the head side riser 25 coincides with the lower edge of the rail head 8 as viewed in the projection of the plane of the drawing in Figure 4. Since the profile of the welding reinforcement 3 continues in the cross section of the head side riser 25, flow underneath the lower edge of the rail head 8 occurs only in the central regions in accordance with the absolute thickness of the welding reinforcement 3 as viewed perpendicular to the rail surface.

According to the invention, the absolute measurements a and b of the cross sectional area of the head side riser 25 in said plane 30 are then selected as a function of the web width s and of the width L of the welding groove 4. In view of the object of the present invention, namely to suppress theformation of sink holes, especially in the transition region of the rail web and the rail head, both the cross sectional dimensioning of the head side risers 25 and their arrangement relative to the structure of the rail profile have the result that premature cooling of the transition region between the web of the rail and the rail head is prevented, since more molten steel and heat are supplied via the head side risers 25 into these critical regions during the solidification process. Since an improved further flow capacity of residual melt and/or a further heat supply capacity is ensured, especially in the region of the lower head flanks of the rail head, zonal surrounding of molten steel by already solidified steel is prevented. This is partly due to the effect of the head risers 24, through which residual melt and heat are fed quasi on all sides into the relatively voluminous rail head region, so that, with this design of the CO4265 mould, especially of the riser systems associated with the rail head region, directional solidification of the rail head part, progressing from the bottom upward, takes place.

Corresponding to the temperature fields dependent on the thickness of the rail web and in connection therewith to the progress in time of the crystallisation of the melt, determined thereby, throughout the casting space, conditions result which deviate quantitatively but not qualitatively and account of which is taken by the ranges according to the invention for the dimensioning of the cross sections of the head side risers Figure 5 shows, similarly to the manner of representation according to Figure 3, a further embodiment of a mould 31 according to the invention, in which, however, functional elements corresponding to those of Figures 1 to 4 are numbered in the same way, so that a repeated description in this respect is unnecessary.

The mould 31 is equipped only with foot risers 17 and not additionally with air channels 18 but it can additionally also be provided with air channels in the same way. On top of the mould 31, there is a mould attachment 32, which can in principle consist of a material corresponding to the material of the mould 31. However, it preferably consists of a material and/or is dimensioned in such a way that its walls have a higher heat insulation capacity than the walls of the mould. For example, it can consist of a refractory material based on zirconium dioxide.

The mould attachment 32 encloses a reception space 33, which is open at the top and bottom and which serves as an insert for the reaction crucible, not illustrated in the drawing, and as a reception space for the slag evolved during the course of the reaction. This will, however, not be discussed in more detail below.

The reception space 33 has, up to a point 34, a shape which conically tapers, starting from its upper end 35 in the direction of the mould 31. The width of the reception space at this point 34 corresponds to the width B of the head riser 24 at the upper end 36 of the mould 31.

The mould attachment 32 and the mould 31 can be fabricated separately from one another and assembled only for carrying out the welding. However, they can in principle also be fabricated integrally.

The upper open end 36 of the mould 31 forms the inlet of the head riser 24, which further tapers conically in the direction of the rail head 8 and globally has a height H. The height H as viewed in the plane of the drawing in Figure 5 is to be understood as the distance between the top end 36 of the mould 31 and the lowest point 37 of the underside of the head side riser 25. The lastmentioned underside has, starting from its one end facing the foot riser 17, a slight downward gradient in the direction of the central plane 9.

Between the head flanks 14 of the rail head 8 on the one hand and the opposite inner walls 22 of the mould walls 28' the sections 38 of the head riser 24 form a cross section which is characterised by the parameters x and y and conically tapers in the direction of the underside. x here marks the horizontal width of this section between the point 37 and the opposite edge of the rail head 8. The dimension y marks the horizontal distance between a straight line laid against the topmost point of the rail head profile and extending parallel to the track of the central plane 9, and that point on the inner wall 22 which is horizontally opposite the vertex 10 of the rail head 8. The point 37 corresponds to that C04265 point on the inner wall 22 which is horizontally opposite the lowermost edge of the head side flank 14 of the rail head 8. Starting from the inlet cross section 39, located at the upper end 36 of the mould, of the head riser 24, this gives a continuous narrowing of the cross section toward the two sections 38 adjacent to the lowermost edges of the head side flanks 14 and characterised by the measurements

X.

The head side risers 25, which, starting from their inlet cross sections facing the foot risers 17, have a slight cross sectional widening in the direction of the rail head, are in other respects, both with regard to the dimensioning and to the arrangement of the opening cross section on the casting space side, designed in the same way as the illustrative embodiment corresponding to Figure 3.

According to the invention, the parameters x, y, H and B are in mutual functional dependence, a corresponding dimensioning of these parameters making, in the same way as the placement and dimensioning of the opening cross sections of the head side risers on the casting space side, a contribution to the prevention of the formation of shrinkage holes in the transition region between the rail web and the rail head and to affecting the crystallisation process in such a way that directional, upwardly progressing solidification results.

Owing to the improved heat insulation of the aluminothermic mixture provided by the mould attachment 32, premature heat loss after the initiation of the reaction is prevented, allowing a lowering of the casting temperatures for the purpose of carrying out a smooth reaction, without a deterioration in the quality of the welded joint, for example due to inadequate superficial fusion of the rail steel.

As Figure 6 shows, the inner walls 22 of the mould have an orientation which is inwardly directed toward the central plane 9 and also the underside 40, and they consist globally of two sections 22', 22". The first-mentioned section 22' starts at the upper end 36 of the mould, and the lastmentioned section 22" ends at the point 37 (Figure 5) where the mould wall 28 (Figure 5) starts. The sections 22', 22" are essentially formed as flat surfaces which have differing angles of inclination relative to a vertical plane. Thus, the angle of inclination of the section 22' relative to the vertical plane is designated a and the angle of inclination of the section 22" relative to the section 22' is designated 3, so that the angle of inclination of the section 22" relative to a vertical plane corresponds to the sum of the angles a and 13. The two angles a and 13 are, in the drawn illustration according to Figure 6, calculated as positive values counterclockwise, so that the sum of the two angles corresponds at least to the value of the angle a. The sections 22', 22" intersect one another because of their generally differing angles of inclination in the region of a horizontally extending edge 41. The inner wall 22 undergoes, in the illustrative embodiment shown in Figure 5, at said upper end 36, a transition to a wall, extending parallel to the central plane 9, of the mould attachment 32. The angle of inclination of the inner wall 22, starting from the section beyond said point 37, is determined by the shape of the mould wall 28 in that region.

According to the invention, the angles a,3 are dimensioned in accordance with the ranges set out above, the object being to obtain in this way an ordered flow of the molten steel in the direction of the web region of the rail profile, in particular a flow free of splash phenomena. Another essential point is here, inter alia, that the sum of the two angles is within the range from 150 to 890.

CO4265 The composite design of the inner wall 22 by two flat sections 22', 22", as shown, between the upper end 36 and the point 37 is to be understood to be merely illustrative. Thus, this region can equally be defined by a continuous curve of the area in particular by a concave curve of the area toward the inside of the head riser 24 between said end 36 and the point 37. In this case, the angles of inclination a, 13 mentioned above correspond to the local angles of inclination at the end 36 on the one hand and the point 37 on the other hand, a continuous transition applying between these discrete individual values of the angles of inclination.

In a limiting case, the angle 3 can also assume the value O, so that, starting from the upper end 36 down to the point 37, a straight-line flat shape of the area of the inner wall 22 results.

C04265

Claims

1. A mould for the welding of two rail ends, consisting of mould walls matched to the rail profile, covering the welding groove present between the rail ends and made of a refractory material, the casting space to be filled by the weld being delimited otherwise by the end faces of the rail ends, and at least one system of foot risers and/or head risers and head side risers being moulded into the mould walls, wherein the area of the opening cross section of a head side riser on the casting space side adjoins the lower edge of the head flank of the rail head and extends upward starting from there, the area is dimensioned in accordance with the thickness of the rail web and also as a function of the height of the rail head and the width of the welding groove, with 0.6 hL<A_3.75 hL, and the head riser has a shape tapering in the direction of the rail head.

2. A mould for the welding of two rail ends, consisting of mould walls matched to the rail profile, covering the welding groove present between the rail ends and made of a refractory material, the casting space to be filled by the weld being delimited otherwise by the end faces of the rail ends, and at least one system of foot risers and/or head risers and/or head side risers being moulded into the mould walls, wherein the width of the head riser is dimensioned in accordance with the width of the rail head, the height of the head riser is dimensioned in accordance with the height of the rail head, the inner walls of the head riser as viewed in the projection of a cross sectional plane of the rail ends form, with the head flanks of the rail head, cross sections which each taper in the direction of the rail foot between an upper side width and an underside width the dimension being within the range from 0.001 b to 0.1 b and the dimension being within the range from 1.01 x to 5 x.

3. A mould as claimed in claim 1, wherein the area has a rectangular and/or square shape, one side of the area extends parallel to the bottom side of the rail foot and the other side (a) extends perpendicular to the side and the sides are dimensioned in accordance with the thickness of the rail web, with 0.6 h5a<1.5 h and/or with Lsb<2.5 L.

4. A mould as claimed in claim 2 or 3, wherein, in the case of thicknesses of the rail web with s_13mm, the area is dimensioned according to 0.75 hL<A<3.75 hL. A mould as claimed in claim 3, wherein, in the case of thicknesses of the rail web with s-13mm, the sides are dimensioned according to 0.75 h-a1.5 h and/or according to L.

6. A mould as claimed in claim 1 or 3, wherein, in the case of thicknesses of the rail web with s 13mm, the area is dimensioned according to 0.6 hL<A<3.75 hL.

7. A mould as claimed in claim 3 or 6, wherein, in the case of thicknesses of the rail web with s 13mm, the sides are dimensioned according to 0.6 h~a1.5 h and/or according to L-b_2.5 L. C04265

8. A mould as claimed in any one of claims 1 or 3 to 5, wherein, in the case of thicknesses of the rail web with s513mm, the area is dimensioned according to 1.125 hL<A<3.0375 hL.

9. A mould as claimed in any one of claims 1, 3 to 5 or 8, wherein, in the case of thicknesses of the rail web with s<13mm, the sides are dimensioned with 0.9 h<a<1.35 h and/or according to 1.25 L5b<2.25 L. A mould as claimed in any one of claims 1, 3, 6 or 7, wherein, in the case of thicknesses of the rail web with s 13mm, the area is dimensioned according to 0.875 hL<A-2.8125 hL.

11. A mould as claimed in any one of claims 1, 3, 6, 7 or 10, wherein, in the case of thicknesses of the rail web with s 13mm, the sides are dimensioned with 0.7 h-a<1.25 h and/or according to 1.25 Lsb:2.25 L.

12. A mould as claimed in any one of claims 1, 3 to 5, 8 or 9, wherein, in the case of thicknesses of the rail web with s<13mm, the area is dimensioned according to 1.575 hL<A<2.4 hL.

13. A mould as claimed in any one of claims 1, 3 to 5, 8, 9 or 12, wherein, in the case of thicknesses of the rail web with s<13mm, the sides are dimensioned with 1.05 h5a:1.2 h and/or 1.5 L5b<2.0 L.

14. A mould as claimed in any one of claims 1, 3, 6, 7, 10 or 11, wherein, in the case of thicknesses of the rail web with s 13mm, the area is dimensioned according to 1.2 hL.

15. A mould as claimed in any one of claims 1, 3, 6, 7, 10, 11 or 14, wherein, in the case of thicknesses of the rail web with s 13mm, the sides are dimensioned with 0.8 hal51.0 h and/or according to 1.5 L5b<2.0 L.

16. A mould as claimed in any one of the preceding claims 1 to 15, wherein, in the case of thicknesses of the rail web with 9mm5s13mm, the width of the head riser (24) is dimensioned in accordance with the width of the rail head with 1.2 bB58 b.

17. A mould as claimed in claim 16, wherein, the width of the head riser is dimensioned with 1.5 b<B55 b.

18. A mould as claimed in any one of claims 16 to 17, wherein the width of the head riser is dimensioned with 1.8 b<B<3.5 b.

19. A mould as claimed in any one of claims 16 to 18, wherein the height of the head riser is dimensioned in accordance with the height of the rail head with 2 h-H520 h. A mould as claimed in any one of claims 16 to 19, wherein the height of the head riser is dimensioned in accordance with the height of the rail head with 2.5 h<H10 h.

21. A mould as claimed in any one of claims 16 to 20, wherein the height of the head riser is dimensioned in accordance with the height of the rail head with 3 hH_8 h.

22. A mould as claimed in any one of claims 1 to 15, wherein, in the case of thicknesses (s) of the rail web with s 13mm, the width of the head riser is dimensioned in accordance with the width of the rail head with 1.2 b<B<8 b.

23. A mould as claimed in claim 22, wherein the width of the head riser is dimensioned with 1.5 bB55 b. C04265

24. A mould as claimed in claim 22 or 23, wherein the width of the head riser is dimensioned with 1.8 b<B<4 b. A mould as claimed in any one of claims 22 to 24, wherein the height of the head riser is dimensioned in accordance with of the height of the rail head with 3 h-H<25 h.

26. A mould as claimed in any one of claims 22 to 25, wherein the height of the head riser is dimensioned in accordance with the height of the rail head with 3 h<H_15 h.

27. A mould as claimed in any one of claims 22 to 26, wherein the height of the head riser is dimensioned in accordance with the height of the rail head with 3 h<H<10 h.

28. A mould as claimed in any one of claims 2 or 16 to 27, wherein the dimension is lo within the range from 0.0025 b to 0.075 b and the dimension is within the range from 1.025 x to X.

29. A mould as claimed in claim 28, wherein the dimension is within the range from 0.01 b to 0.1 b and the dimension is within the range from 1.075 x to 1.5 x. A mould as claimed in any one of claims 1 to 29, comprising a mould attachment which is destined to receive, inter alia, a reaction crucible and consists of a refractory material.

31. A mould as claimed in claim 30 wherein the mould attachment consists of a refractory material having a higher heat-insulation capacity than that of the other mould walls.

32. A mould as claimed in any one of claims 1 to 31, wherein the inner wall of the head riser has, starting with the upper open end down to the region of the head side risers, a varying angle of inclination, as viewed in a cross sectional plane extending perpendicular to the longitudinal axis of the rail ends.

33. A mould as claimed in claim 32, wherein the angle of inclination has a value at the upper end and a value at the lower end, and the angle of inclination (13) and the angle of inclination are dimensioned in accordance with the relationship 13 z a, the sum of the angles of inclination (a 13) being in accordance with the relationship 15'_(a 03)<890, the sum of the angles of inclination (a 13) being, furthermore, (a 13) a and the parameter corresponding to a value of between 0.01 and 4.93 in accordance with the angle of inclination -34. A mould as claimed in claim 33, wherein the angle of inclination has a value at the upper end and a value (13) at the point of the head side riser. A mould as claimed in claim 33 or 34, wherein, for an angle of inclination with a<60 the parameter is selected to be within the range 0.01<z<0.48.

36. A mould as claimed in claim 33 or 34, wherein, for an angle of inclination with a545', the parameter is selected to be within the range 0.02<z<0.98.

37. A mould as claimed in claim 33 or 34, wherein, for an angle of inclination with a-30 the parameter is selected to be within the range 0.03<z<1.96.

38. A mould as claimed in claim 33 or 34, wherein, for an angle of inclination with the parameter is selected to be within the range 0.05<z<3.45. C04265

39. A mould as claimed in any one of claims 33 to 38, wherein, for an angle of inclination (a) with a<15, the parameter is selected to be within the range 0.06<z<4.93 A mould as claimed in any one of claims 33 to 39, wherein the inner walls of the head riser, starting with the upper end are composed of at least two successive sections of planar shape, the angle of inclination corresponding to the angle of inclination of the upper section starting at the end, and the angle of inclination (13) corresponding to the angle of inclination of the lower section ending in the region of the head side riser.

41. A mould as claimed in any one of claims 33 to 40, wherein the inner walls of the head riser have, between the upper end thereof characterised by the angle of inclination and the lower end, in the region of the head side riser, in particular the point thereof, characterised by the angle of inclination a steadily curved shape of the area, which, in particular, is concave toward the inside of the head riser.

42. A mould for the welding of two rail ends, consisting of mould walls matched to the rail profile, covering the welding groove present between the rail ends and made of a refractory material, the casting space to be filled by the weld being delimited otherwise by the end faces of the rail ends, and at least one system of foot risers and/or head risers and head side risers being moulded into the mould walls, substantially as hereinbefore described with reference to the accompanying drawings. Dated 10 December 1998 ELEKTRO-THERMIT GMBH Patent Attorneys for the Applicant/Nominated Person SPRUSON&FERGUSON C04265