CH659602A5 - METHOD FOR PRODUCING A SEALING ARRANGEMENT ON A SLIDING LOCK. - Google Patents

Description

The invention relates to a method for producing a sealing arrangement on the sliding, preferably plate-shaped closure bodies of a sliding closure for casting metal, in particular light metal melts.

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 have to be replaced after a few castings for safety reasons.

From DE-AS 2 404 881 a sealing arrangement on a rotary slide closure is known, which consists of an annular sealing ring concentric with the axis of rotation; the latter can be arranged on the circumference of the plates or can be 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 surfaces towards the outside, i.e. it is designed to protect against breakthrough in the event of a serious malfunction or damage. However, this arrangement cannot change the wear phenomena mentioned or the limited period of use of the plates.

In contrast, a proposal according to DE-OS 3,031,377 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, it has been shown, however, that even with low wetting there is always a certain adhesion between the plate material and the melt and when the closure is actuated, a “pulling in” of small amounts of melt between the plate sliding surfaces cannot be avoided. 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 flow opening or to ensure the spontaneous outflow when the closure is opened. However, at some distance from said opening, the temperature on the plate sliding surface must necessarily be lower 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 ensure the tightness along the sliding surfaces on a sliding closure during a large number of sliding movements and thereby to enable extended operating periods without changing the closure bodies. 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 the method for producing a sealing arrangement according to the characterizing part of claim 1.

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. So z. B. continuous operation on melting, holding or casting furnaces with the melt standing still possible or the use for the continuous pouring of separate, measured amounts 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 its flow opening, i.e. in the direction of movement or in the direction of the “wear grooves” must be guaranteed. In view of the requirement mentioned in the second place above, it is certainly surprising if depressions or “grooves” formed by wear according to the invention are included in the sealing arrangement. The 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 also has favorable sliding properties).

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Can have shafts that affect the entire sliding 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 formation 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 whether the metal particles remain molten in the batch or solidify (temporarily); even if after a series of operations e.g. If the melt vessel is emptied and the temperature on the slide sliding surfaces drops considerably below the solidification temperature of the melt, the seal can be operated again later, after refilling the melt.

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.

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 mounted on 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 part of the fixed and the movable closure plate in a large magnification,

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. perpendicular to the direction of movement (magnification approx. 150 times linear), and

Fig. 6 is a similar micrograph taken 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 slide closure 10 and parts of the melt vessel to which the closure 10 is attached are only dash-dotted indicated. 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 bottom plate

12 or with its sliding surface 9, the movable slide plate 14 of the closure is 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 in a known manner either made to coincide 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.

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, reference is made to the Swiss patent specification No. 653 933 or the German patent application P 3 208 101.4, the Swiss patent specification 523 730 and the German patent specification 1 951 447 as examples of linear slide closures and to the European published patent application 0 040 692 or the German Offenlegungsschrift 3,013,975 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, for. B. can be realized according to FIG. 1, but in principle also on closure bodies of a different shape with z. B. cylindrical, conical or 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 both plates 12, 14 are exactly flat and the plates are permanently clamped together 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. The abrasion resistance of the material is shown in the signs of wear 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 with exposure to melt 3 according to Fig. 1, i.e. the slide plate is shifted back and forth in the direction of arrow P with respect to the base plate, a “wear pattern” soon arises on the sliding surface 9 of the abradable plate 12, as can be seen from FIG. 2. In a surface area which extends from the flow-through bore 13 by about the stroke length to 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 sliding direction. 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. 4 shows this typical wear pattern in cross section in a large enlargement. As can be seen, the above-mentioned depressions or “wear grooves” 19 are not empty, but are filled from the beginning with a material mixture 20, which arises between the plates 12 and 14 when the closure is actuated and is embedded in the depressions 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 in between the plates during the sliding movement. As is apparent from Fig. 4.

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As expected, the sliding surface of the abrasion-resistant plate 14 remains 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. So at the beginning of the operation,

a sealing arrangement between the closure bodies 12 and 14 is 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.

Even with the reverse arrangement of the closure body - abrasion-resistant body fixed and abrasion-capable 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 abradable sliding surface is in constant contact with the standing melt 3.

It is noticeable that the described “wear pattern” with embedded material mixture on the abrasion-capable sliding surface only occurs in the mentioned surface area shown in FIG. 2, but not in the surrounding areas of the sliding surface 9. This means (as also the composition of the mixture 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 as the closure continues to be operated. 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 for the one closure body to consist of abrasion-resistant material, but it is sufficient if this property is at least given on its sliding surface. 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 wearable 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 turning the movable closure plate in the direction of arrow R, the “wear pattern” shown in FIG. 3 is produced, i.e. essentially circular, concentric, corrugated

len-shaped recesses 19 'in the abrasion-resistant sliding surface of the closure plate 22. If, on the other hand, the rotary closure, as is also known, were opened and closed by partial rotations with alternating directions of rotation, the recesses 19' would only extend over a corresponding circular arc of limited length. Otherwise, the above statements regarding FIGS. 1, 2 and 4 apply to the manufacture and properties of the sealing arrangement and, in particular, to the material mixture embedded in the wear grooves also apply analogously to the exemplary 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 sealing 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 embedded 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 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 open, that is once transverse to the direction of movement and in the other case tangential to a certain wear groove 19 ', ie at the relevant point of contact of the cutting line in the direction of the actuation movement. The micrographs Fig. 5 and Fig. 6 were then taken at the relevant points. 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 rather irregular mixture, although 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 pairings for closure bodies, as have been used successfully in the manufacture of the sealing arrangement described, 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 mixture can be achieved in selection tests in the presence of melt, which then enables the production of the sealing arrangement and thus the reliable continuous operation of the closure. Findings and tests to date confirm that graphite or mixtures of materials with a high graphite content or other materials with a similar, characteristic “platelet structure” are particularly suitable as wear-resistant materials.

example 1

A cover plate made of electrographite (99% graphite content, 18 vol.% Open porosity) was used as an abrasion-resistant,

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Fixed plate used in conjunction with an abrasion-resistant slide plate made of zirconium oxide (95% Zr02) in a linear slide lock attached to a 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 about 3000 actuation strokes without malfunction and if the closure was properly 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 lock was equipped with an abrasion-capable, fixed locking plate made of hot-pressed boron nitride BN with a hexagonal lattice structure and a rotating plate made of Zr02 (same material as example 1). A pure aluminum melt (99.5% Al) of 750 ° C. was poured off in a test device 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% A1203, 8% Si02). The series of tests included no less than 10 550 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 lock was installed as a tap lock 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% by volume open porosity) and a rotating plate made of aluminum titanate Al2Ti05 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 even achieved without interference in a rotary slide lock attached to a test facility.

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Claims (8)

659 602 PATENT CLAIMS 1. A method for producing a sealing arrangement on the sliding bodies of a sliding closure for casting metal, in particular light metal melts, characterized in that a sealing body (12, 22) which is abradable at least on its sliding surface (9) and an abrasion-resistant sealing body (14, 14 ') is used, and that one continues to move both closure bodies in mutual sliding contact with simultaneous exposure to the melt (3) against each other and thereby produces a mixture (20) of abrasion (A) and metal particles (M), which essentially groove-shaped depressions (19, 19 '), which run in the direction of displacement (P, R) and are formed by wear, are embedded in the sliding surface (9) of the abrasion-capable closure body (12, 22). 2. The method according to claim 1, characterized in that the abrasion-resistant closure body (12, 22) is used as a fixed and the abrasion-resistant (14, 14 ') as a displaceable closure body. 3. The method according to claim 1, characterized in that one uses predominantly graphite as the abrasion-resistant closure body (12, 22). 4. The method according to claim 1, characterized in that one uses predominantly boron nitride with a hexagonal lattice structure as the abrasion-resistant closure body (12, 22). 5. The method according to claim 1, characterized in that the abrasion-resistant closure body (14, 14 ') used is one made of high-alumina material. 6. The method according to claim 1, characterized in that one uses predominantly zirconium oxide as the abrasion-resistant closure body (14, 14 '). 7. The method according to claim 1, characterized in that one uses predominantly aluminum titanate as the abrasion-resistant closure body (14, 14 '). 8. Sealing arrangement, produced by the method according to one of claims 1 to 7.