LU84977A1 - SEALING ARRANGEMENT ON A SLIDING CLOSURE AND USE OF TWO LOCKING BODIES FOR PRODUCING THE SEALING ARRANGEMENT - Google Patents

Description

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Stopinc Aktiengesellschaft, Baar (Switzerland) case 3217

Sealing arrangement on a sliding closure and use of two closure bodies for producing the sealing arrangement

The invention relates to a sealing arrangement on the sliding, preferably plate-shaped closure bodies of a sliding closure for casting metal, in particular light metal melts. In addition, the invention relates to the use of an abrasion-resistant closure body in sliding contact with an abrasion-resistant closure body for the purpose of producing the aforementioned sealing arrangement according to the invention.

With sliding closures, such as those used primarily for casting steel, the tightness is guaranteed by exact surface grinding of both locking bodies (fixed and «movable locking plate). As is known, the flowing steel melt causes intensive wear both on the plate bores (flow openings) and on the sealing surfaces despite the use of particularly high-quality refractory materials, which is why the plates must be replaced after a few castings for safety reasons.

From DE-AS 24 04 881 a sealing arrangement on a rotary slide closure is known, which consists of a ring-shaped

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- 4 - mm, concentric to the axis of rotation sealing ring exists; the latter can be arranged on the circumference of the plates or inserted between the plates in a groove extending from the sealing surfaces. This arrangement is intended to prevent melt from escaping between the plate sealing faces towards the outside thereof, i.e. it is designed to protect against breakthrough in the event of a serious malfunction or damage. However, this arrangement cannot change the abovementioned wear phenomena or the limited period of use of the plates.

In contrast, a proposal according to DE-OS 30 31 377 aims in this direction.

Thereafter, the penetration of melt between the plate sliding surfaces is to be prevented and the solidification of penetrated melt is to be counteracted. According to the proposal there, this is done by combining closure plates made of certain different materials, namely a stationary plate made of soft, lubricating and poorly wettable material with high thermal conductivity and a movable plate made of hard and dense material with low thermal conductivity. In contrast, however, it has been shown that even with low wetting there is always a certain *

Adhesion exists between the plate material and the melt and "pulling" small amounts of melt between the plate sliding surfaces cannot be avoided when the closure is actuated. Furthermore, a high thermal conductivity of the stationary plate is indeed a suitable means (in conjunction with other measures) in order to prevent the melt from "solidifying" in the area of the throughflow opening or to guarantee the spontaneous outflow when the closure is opened Distance from said opening the temperature on the plate sliding surface must necessarily be lower / \

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- 5 - than the solidification temperature of the melt, otherwise the tightness of the closure is questioned.

The object to be achieved with the invention is to use a slide lock during a large number of shooting; Movement to ensure tightness along the sliding surfaces and thereby enable extended periods of operation without changing the closure body. In this context it should be mentioned that under certain operating conditions, especially when casting light metal melts, the wear at the flow openings of the closure plates is low; in such cases, the condition of the sealing surfaces sliding on each other is practically decisive for the service life of the plates.

This object is achieved according to the invention by a sealing arrangement which is produced in a specific way according to claim 1. The use according to the invention of closure bodies in the production of such a sealing arrangement is characterized by the measure according to claim 5.

The fact that the invention ensures a tight closure during several thousand to well over 10,000 slide operations with the same closure bodies opens up new areas of application for the slide closure. For example, continuous operation on melting, holding or pouring furnaces under standing melt is possible or the use for continued

Casting of separate, measured quantities of melt during casting.

In connection with the invention it should be remembered that the seal along the sliding surfaces of the closure body, starting from the fixed flow opening, both on all sides towards the edge of the sliding surface and - in the closed position of the movable closure body - against / - 6 - its Flow opening towards, ie in the direction of movement or in the direction of the "wear grooves" must be guaranteed. In view of the requirement mentioned in second place above, it is certainly surprising if depressions or “grooves” formed by wear according to the invention are included in the sealing arrangement. A targeted use of

Abrasion and wear also completely contradicts the conventional idea of "lubrication", which is aimed precisely at avoiding wear and reducing friction (this of course does not rule out that the abrasion-resistant material can also have favorable sliding properties that can be found throughout Slip surface as low friction).

According to the invention, the occurrence of abrasion in a mixture with metal particles has been recognized as decisive for a permanent tightness with continued actuation of the closure. Although it cannot be stated generally and conclusively which specific material pairings lead to the goal, this can - based on the invention - be determined from case to case with relatively simple experiments.

The mode of operation of the mixture mentioned can essentially be imagined in such a way that the presence of the abrasion particles prevents the build-up of coherent metal bodies between the sliding surfaces, which, if solidified as "metal tongues" or "sheets", would lead to the rapid destruction of the closure bodies. It was found that the batch has a very low strength, but that there is a certain cohesion between the particles, which prevents "washing out" and the groove-shaped depressions remain permanently filled by the batch. Incidentally, the sealing effect obviously does not depend on it, whether the metal particles remain molten in the batch or solidify (temporarily); - 7 - even if after a series of operations e.g. If the melt container is emptied and the temperature on the slide sliding surfaces drops significantly below the solidification temperature of the melt, the seal can be operated again later after the melt has been refilled.

The invention is equally applicable to linear sliding closures such as rotary and pivot closures; the rotary movement can be of a changing direction (analogous to the linear lock) or always in the same sense. The closure can also be attached to the furnace or melting vessel with the sliding surfaces in a horizontal, inclined or vertical position.

The claim 2 relates to a preferred installation of the abradable and the fixed closure body. Claim 3 relates to the specific arrangement in the linear and claim 4 in the rotary slide lock. Claims 6 to 10 finally relate to the use of certain materials for the closure body.

Various exemplary embodiments of the invention are described in more detail below in connection with the drawing. Show it:

1 essential parts of a linear slide closure attached to a melt vessel in longitudinal section,

2 shows the view of the sliding surface of the fixed closure plate (partially broken away) of the closure according to FIG. 1,

3 shows a corresponding view of the fixed closure plate of a rotary slide closure,

4 shows a section along the line IV-IV in FIG. 2 through a lot of the fixed and the movable closure plate in a large magnification, - δ -

Fig. 5 is a microscopic micrograph of the mixture of wear and metal particles in section along the line V-V in Fig. 3, i.e. perpendicular to the direction of movement (magnification approx. 150 times linear), and

Fig. 6 is a similar micrograph in section along the line VI-VI in Fig. 3, i.e. in the direction of movement (magnification approx. 165 times linear).

In the exemplary embodiment according to FIG. 1, only the two closure bodies - here in the form of two flat plates 12 and 14 - are drawn with solid lines, further parts of the sliding closure 10 and parts of the melting vessel to which the closure 10 is attached are only indicated by dash-dotted lines. The melt vessel 1 contains a metal melt 3, for example an aluminum melt, and has a pouring opening 2, which leads to the sliding closure 10. The stationary base plate 12 of the closure is held in a base plate 16 fastened to the melt vessel 1 and has a flow opening 13 which continues the vessel opening 2. With the base plate 12 or with. whose sliding surface 9 is the movable slide plate 14 of the

Closure in sliding contact, i.e. the slide plate can be moved back and forth together with the slide 18 receiving it in the direction of arrow P along the sliding surface 9. The flow opening 15 of the slide plate is either brought to cover in a known manner with the flow opening 13 of the base plate 12 (open position of the closure) or, as shown, offset against it (closed position). A pouring sleeve 17 inserted in the slide 18 can connect to the flow opening 15 in a known manner.

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It is not necessary to describe the further construction of the closure according to FIG. 1 in detail, since this is not necessary to understand the invention. Merely for the sake of completeness, Swiss patent application 3255 / 81-5 and German patent application P 32 08 101.4, the Swiss; Patent specification 523 730 and the German patent specification 19 51 447 as examples of linear sliding closures and on the European * 0 see published patent application 0 040 692 or the German

Laid open publication 30 13 975 as examples of rotary slide closures. However, it should be emphasized that the sealing arrangement according to the invention not only on plate-shaped closure bodies with a flat sliding surface such as e.g. 1 can be realized, but in principle also on closure bodies of a different shape with e.g. cylindrical, conical or T-spherical sealing surface.

The tightness of the closure 10 when it is started up is provided in a known manner in that the sliding surfaces of the plates 12, 14 are exactly flat and the plates are continuously clamped perpendicular to the sliding surfaces. However, in order to ensure the tightness not only for a few operations, but also in the sense of the invention also with continued operation with thousands of operations, the one closure body, in this case the fixed base plate 12, is made of an abrasion-resistant material at least along its sliding surface 9 , while the other closure body, here the displaceable plate 14, consists of abrasion-resistant material.

• t '* The abrasion ability of the material is shown in wear phenomena on the sliding surface 9 of the plate 12, which are shown in more detail in FIGS. 2 and 4 and are explained below:

If the closure continues to operate with new plates 12, 14 and when exposed to melt 3 according to FIG. the slide plate is moved back and forth in the direction of the arrow P in relation to the base plate, will soon appear at / t - 10 -

The sliding surface 9 of the abradable plate 12 forms a “wear pattern”, as can be seen in FIG. 2. It is formed in an area which extends from the flow bore 13 by approximately the stroke length on both sides (the bore 15 in the closed position is indicated in Fig. 2), more or less randomly arranged and shaped groove-shaped depressions 19, which run essentially in the direction of the slide. The width of the surface area mentioned corresponds approximately to the diameter of the bore 13 (even if this is, for example, larger than that of the bore 15 ), it can also go somewhat beyond this diameter according to Fig. 2. Fig. 4 shows this typical wear pattern in cross-section in a large enlargement. As can be seen, however, the depressions or "wear grooves" 19 mentioned are not empty, but from the beginning with filled in a mixture of materials 20 which arises when the closure is actuated between the plates 12 and 14 and s I stored in the recesses 19. It is a mixture of abrasion particles of the abradable plate 12 and small particles or droplets of the melt 3, which are drawn between the plates during the sliding movement. As can be seen from FIG. 4, the sliding surface of the abrasion-resistant plate 14 remains, as expected, practically flat or without wear.

As a result of the phenomena and processes described above, the closure remains operational and reliably tight during a very large number of operations. At the beginning of the operation, a sealing arrangement between the closure bodies 12 and 14 is thus produced by actuating the closure under the action of melt in the manner described. It has been shown that the wear or the depth of the grooves 19 does not increase steadily, but perhaps remains practically stationary after a few hundred operations. The observed groove depth ranges from a few tenths of a millimeter to about one millimeter.

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Even with the reverse arrangement of the closure body - abrasion-resistant body fixed and abrasion-resistant body displaceable - it is basically possible to produce the described sealing arrangement in the same way. However, this can have certain disadvantages in other respects, e.g.

because then the abrasion-resistant sliding surface is constantly in contact with the standing melt 3.

It is striking that the described "wear pattern" with a stored material mixture on the abrasion-resistant sliding surface is only made of pig. 2 visible surface area occurs, but not in the surrounding areas of the sliding surface 9. This means (as the composition of the batch 20 shows) that the process is linked to the presence of melt. It can be assumed that during the relative displacement of the closure body, small amounts of melt are drawn in between the sliding surfaces and then, possibly after their solidification, cause the abrasion; the phenomenon was observed with materials that are only slightly wetted by the melt (e.g. different types of graphite). Although the processes inside the "wear grooves" 19 are not accessible for direct observation, it is assumed that the local composition of the batch 20 changes again and again with continued actuation of the closure. However, the particles of the mixture show a certain cohesion, at least in the cooled state. If the closure is shut down after prolonged operation and the closure plates are then taken apart, the batch preferably remains slightly adhering to the surface of the wear-resistant plate 14.

Of course, it is not necessary that the one closure body consist of abrasion-resistant material, but it is sufficient if this property is at least on its t - 12 -

Sliding surface is given. The relevant closure body or the closure plate 12 can e.g. be composed of two or more layers of different materials in thickness. In this way, closure bodies can be produced which, in addition to the required abrasion ability on the sliding surface, have certain advantageous combinations of material properties, for example with regard to thermal conductivity, flexural strength, hardness, etc.

In contrast to FIG. 2, FIG. 3 shows the view of the wear-resistant sliding surface of the fixed closure plate 22 of a rotary slide closure. The flow opening of which is arranged off-center is designated by 23, and the position of the flow opening of the movable, abrasion-resistant closure plate (not shown) in its closed position is indicated by dash-dotted lines at 25. After continued actuation of this closure by rotating the movable closure plate in the direction of arrow R, the "wear pattern" shown in FIG. 3 is produced, i.e. essentially circular, concentric, groove-shaped depressions 19 'are formed in the abrasion-resistant sliding surface of the closure plate 22. If, on the other hand, the twist lock was opened and closed by partial rotations with alternating directions of rotation, the depressions 19' would only open via a corresponding circular arc extend of limited length. 1, 2 and 4 regarding the manufacture and properties of the sealing arrangement and in particular the batch of material embedded in the wear grooves also apply analogously to the embodiment according to FIG. 3.

5 and 6 give an idea of the structure of the batch 20 forming part of the sealing arrangement (FIG. 4). After the seal arrangement was produced in the manner described on a twist lock according to the example in FIG. 3 and the lock was in operation for a long time, the lock was stopped and dismantled. When separating the rotatable and the fixed closure plate, most of the batch stored in the recesses 19 'remained adhering to the sliding surface of the rotatable plate. This sliding surface of the rotatable plate forms the lower edge in FIGS. 5 and 6 and is designated 14 'there. The area 14 'with the mixture was then poured over with a hardening casting resin (G in FIGS. 5 and 6), and after the hardening thereof, the preparation was on the one hand along a line V - V and on the other hand along a line VI - VI in FIG. 3 cut on, that is to say transversely to the direction of movement and otherwise tangential to a specific wear groove 19 ', ie at the relevant point of contact of the cutting line in the direction of the actuation movement. At the relevant points, the ground pictures Fig. 5 and Fig. 6 were then taken. In both pictures, the embedded metal particles M are recognizable as bright, practically white spots. The abrasion particles A mixed with the metal particles appear gray. The more or less large dark to black spots H, on the other hand, are to be interpreted as cavities in the batch or as unevenness in the ground plane that arose during the preparation of the preparation.

In comparison to FIG. 5, FIG. 6 clearly shows the direction of movement when the lock is actuated. Both

Figures show a fairly irregular mixture, but it is considered essential that no larger "metal lumps" are formed, but that the metal particles are repeatedly interrupted by intermediate wear particles. Some specific materials or material combinations for closure bodies, such as have been used successfully in the manufacture of the described sealing arrangement, are given below as examples. It is understood that this information cannot be complete. The selection must be made on a case-by-case basis among materials that are sufficiently resistant to the respective melt at the given temperature. The decisive aspect for the suitability is then whether the described abrasion phenomena and the amount can be achieved in the case of selection tests in the presence of melt, which then enables the sealing arrangement to be produced and thus the reliable, continuous operation of the closure. Findings and tests to date confirm that graphite or material mixtures with a high graphite content or other materials with a similar, characteristic "platelet structure" are particularly suitable as abrasion-resistant materials.

Example 1: A closure plate made of electrographite (99% graphite content, 18 vol.% Open porosity) was used as an abrasion-resistant, fixed plate in connection with an abrasion-resistant slide plate made of zirconium oxide (95% Zr02) in a linear slide closure attached to a casting trough. By continuing to operate the closure, measured quantities of a cast aluminum alloy (G-AlSi9Mg according to DIN 1725, with 9% Si and 0.3% Mg) were cast at a temperature of approximately 750 ° C. The seal arrangement was produced in the manner described. After approximately 3,000 actuation strokes without malfunction and with the seal tightly sealed, the casting operation was stopped and the closure plates were removed to examine the sealing arrangement. It turned out that the plates could have been used without any risk.

Example 2 *: A rotary slide closure was equipped with an abrasion-resistant, fixed closure plate made of hot-pressed boron nitride BN with a hexagonal lattice structure and a rotatable plate made of ZrC> 2 (same material as example 1). A pure aluminum - 15 -

Cast melt (99.5% Al) at 750 ° C by continuing to open and close the closure. After 965 trouble-free actuations (revolutions) in the course of which the described sealing arrangement had been generated, the experiment was stopped.

Example 3: The same closure as in Example 2 was subjected to an endurance test in the same test facility and with the same melt, but with a different plate assembly. In this case, a fixed plate made of carbon with a high graphite content (over 92% electrographite) was combined with an abrasion-resistant rotating plate made of high-alumina material (90% AI2O3, 8% S1O2). The series of tests included no less than 10550 operations, i.e. Castings with shorter or longer interruptions and the associated cooling of the closing plates. The subsequent investigation showed that the plates or the sealing arrangement would still have been functional.

Example 4: A rotary slide closure was installed as a tapping closure on a melting and holding furnace for pure aluminum (approx. 750 ° C). The closure was equipped with a fixed plate made of electrographite (99% graphite, 14% vol. Open porosity) and a rotating plate made of aluminum titanate - AI2TXO5 and the operation was characterized by frequent tapping of relatively small amounts of melt. In this way, around 800 locking operations with complete tightness were achieved during about three and a half days. The subsequent investigation showed that the plates and their sealing arrangement were still fit for purpose. With locking plates made of the same materials, around 6400 operations were achieved without any problems in a rotary slide lock attached to a test facility.

Claims (8)

1.Sealing arrangement on the sliding, preferably plate-shaped closure bodies of a sliding closure (10) for potting metal, in particular light metal melts, produced by continued relative displacement between a closure body (12, 22) which can be abraded at least on its sliding surface (9) and one with this in Wear-resistant abrasion-resistant closure bodies (14, 14 ') while simultaneously applying melt (3) to the closure bodies, forming a mixture (20) of abrasion (A) and metal particles (M) between the closure bodies, which are essentially groove-shaped and In the direction of displacement (P, R), recesses (19, 19 ') formed by wear are embedded in the sliding surface (9) of the abrasion-resistant closure body (12, 22). 2. Sealing arrangement according to claim 1, wherein the abrasion-resistant closure body (12, 22) is fixed and the abrasion-resistant closure body (14) is displaceable. 3. Sealing arrangement according to claim 1 or 2 on the closure bodies of a linear sliding closure, with substantially rectilinear depressions (19, Fig. 2). / / / s 3217 i w ♦ - 2 - 4. Sealing arrangement according to claim 1 or 2 to the closure-jg || body of a rotary slide closure, with essentially HM * circular or circular arc-shaped recesses (19 ', Fig. 3). 1311 5- Use of an abrasion-resistant closure body (12, 22) at least on its sliding surface in sliding contact with an abrasion-resistant closure body (14, 14 ') for producing a sealing arrangement between the preferably plate-shaped closure bodies of a sliding closure (10) for potting of metal, in particular light metal melts, by continued actuation of the closure acted upon by the melt (3) and formation of a mixture (20) of abrasion (A) and metal particles (M) between the closure bodies, which is essentially groove-shaped and in the direction of actuation (P. , R) extending recesses (19, 19 ') caused by wear in the sliding surface (9) of the abrasion-resistant closure body (12, 22). 16. Use of an abrasion-resistant closure body (12, 22) consisting predominantly of graphite according to claim 5. 7. Use of an abrasion-resistant closure body (12, 22) consisting predominantly of boron nitride with a hexagonal lattice structure according to claim 5. 8. Use of a high-alumina, abrasion-resistant closure body (14, 14 ') according to claim 5. 9 · Use of an abrasion-resistant closure body (14, 14 ') consisting predominantly of zirconium oxide according to claim 5. 10. Use of an abrasion-resistant closure body consisting predominantly of aluminum titanate according to claim 5.