DE2058842A1 - Method and device for the production of shell castings - Google Patents

Description

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DIPL.-ING. XL MARCH DIPL.-ING. K. SPARING

TBUTOJT «ΜIU (IUM

1/538

Description of the patent application

of Polygram Casting Co. Limited, Shernfold Park, Frant,

Turnbridge Wells, Kent / England

concerning:
"Process and device for the production of shell castings"

The invention relates to a process for the preparation of a specific and Schalengußteilen for carrying out the method dea device.

In some cases it is necessary to support the shell molds while molding is taking place in order to prevent damage or warping of the thin shells . This need arises all the more, the larger and heavier the cast parts which produce xu.

It is known to effect such a support of the Schalenfonaen that they are inserted into a container and this is then filled with refractory granular material, for example steel shot, gravel, grit, wet sand, which material is optionally compacted so that the forms are supported from will. After the GuA has taken place and the melt has solidified, it can be removed from the container. The AhstUtsgranulatmaterlal must then be removed from the container so that the process can be repeated if the

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next casting takes place. Sometimes the container has an openable bottom to allow the granular material to be discharged to simplify.

This method requires that large amounts of granular material have to be handled, and the time and manpower requirements as well as the need for devices are considerable.

The object of the present invention is to create a method of the type described above in which the need for the exchange of granular material in the container can be dispensed with. This object is achieved according to the invention in that a fluidizing gas is passed through the granular material to form a granular fluid bed, while the permeability of the shell molds is reduced relative to that of the fluid bed for the gas for the purpose of guiding the gas essentially through the granular material that the Shell molds are used in the fluid bed to such a depth that when the fluid bed collapses, the shell molds are supported by the refractory granulate material , but the pouring opening (s) are above the granulate material surface, so that the fluid bed is brought to collapse by switching off the gas supply and that after After the casting, gas is again passed through the granular material to form the fluid bed and the shell molds are removed.

In a preferred embodiment of the invention the permeability of the Schalengußformen is reduced by the fact that the mold is coated with a substance which is impermeable to the fluidic sierende gas, which substance will be at least partially destroyed during the casting, so that a a permissible value the permeability of the mold gives rise to the gases that are evolved during casting.

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The forms can be encased in a sheet of substance or the form can be placed in a sack or container made of this substance. The train, the sack or the container must not be near the. or the pouring openings be in the mold, or, if so, the gate must be opened for casting. Open that can be done in a simple manner in that the melt that is to be poured is poured onto that part of the substance, which covers the pouring sprue ^ uSkT the heat of the melted To use metal to destroy that part of the substance. The material for the envelope can consist of plastic, for example polyethylene;

Alternatively, the shell mold can also be coated, for example by spraying one for it Case of suitable substance which reduces the permeability of the shell molds with respect to the fluidizing gas * and is destroyed while the casting is taking place, or with another substance that admittedly opposes the permeability of the mold fluidizing gas, but not the permeability of the mold to gases evolved during casting reduced an unacceptable value. An example of the first * The substance mentioned is paraffin wax, while bentonite can be used in the second case.

If the molds have a small internal volume, can oppose the required reduction in permeability the fluidizing gas can be achieved in that the sprue or sprues of the molds are closed and only for the casting be opened. A sprue plug can be used for this purpose.

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The required ratio between the permeability the shell molds and that of the fluidizing bed can be achieved in that a granular substance is used as the refractory material, the grain size of which is chosen so that in fluidized state, the permeability of the fluid bed is significantly greater than that of the shell mold, so that the required The degree of fluidization is also maintained in the immediate vicinity of the shell molds after the latter has entered the fluidized bed has been used.

The thermal conductivity of the fluid bed and thus the cooling of the mold during casting can be increased, by using material with a higher thermal conductivity than conventional refractory material. Instead of conventional refractory sand can be zircon sand, chromite or olivine can be used.

The refractory material of which the fluidized bed is made can be dry sand or some other refractory material with a gas permeability for the gases evolving during casting which is well above that of the shell mold at this stage of the process .

Each shell mold can be supported in an open mesh basket during movement into and out of the fluid bed and during casting. Larger shell molds can be customized

Baskets can be assigned, but it is possible to pack several smaller shapes in a common basket.

In a preferred variant of the invention The fluid bed is vibrated before casting

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Compressed container. The container can already be in Vlbration be moved while the fluid bed is still being formed, so that upon completion of the fluidization, the bed is rapidly compacted. The vibration can also be stopped shortly after the end of the fluidization.

The invention will be explained in more detail below with reference to the accompanying drawings.

Fig. 1 shows in side view, partly in section,

a section of a device for performing the method according to the invention.

FIG. 2 is a plan view of the device according to FIG Fig. 1, and

FIG. 3 diagrammatically shows a plan view of a section of another embodiment of FIG Contraption.

Fig. 1 and 2 show a container 1 for granulated refractory material 2, which is supported on a fluidizing floor 3, under which the container is formed so that a Air box 4 arises, which via lines 5 with a flow control valve 6 to a (not shown) fluidizing air source connected. The fluidizing floor 3 acts in a known manner so that a uniform flow of fluidizing air through the material is maintained so that the latter is fluidized. ■

Shell molds made by any known method become an open framework comprehensive holder 7 held. The exact design of the holder 7 depends of course on the shape and size of the shapes, but shows

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the drawing shows a typical embodiment. It has side parts 8, from the lower ends of which cross supports 9 extend, the ends of which are connected by longitudinal cross members 10, from which the forest supports 11 extend. As can be seen from Fig. 2, the form supports are channel sections and in pairs arranged with the open portions of each pair facing each other. The cross supports 9 and the longitudinal beams 10 also support a wire mesh floor 12, the task of which is still to be explained. The shell molds, which normally have a peripheral flange, are located between the mold supports 11, fe wherein the circumferential flanges engage in their channel sections.

Before the shell molds are introduced into the holder 7, they are, as shown diagrammatically in FIGS. 1 and 2, used at 13 in bags 14 made of polyethylene, the openings of which are at the top and remain open, so that the sprues 15 of the Shell shapes remain accessible. As soon as the shell molds in the holder 7 with their flanges engaging in the mold supports 11, as described above, have been inserted, a locking rod 16 is passed through openings in the side parts 8 to to prevent upward movement of the shell shapes, which would otherwise be possible.

w The device is then used as follows

explainedi

The container is filled with a granular material, for example quartz sand, and the lines 5 to a source connected by fluidizing air. The shell molds which fill xu are inserted into the polyethylene bags as described above and then inserted into the holder 7. The fluidizing Air is then allowed to flow into the air box 4 by opening the valve 6 is opened, and when the granulate material 2 is completely

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is fluidized, the holder is immersed in the fluidized material lowered until the angle 17 on the rare parts 8 on the top Sit on the edge of the container.

The depth to which the shell shapes fluidized into the Material to be countersunk is chosen so that the sprue 15 safely above the surface of the material remain free in such a way that that when the valve 6 is closed so that the fluid bed of the material 2 collapses, the shell forms in the material are securely embedded.

After the fluidized bed collapses, the material be compressed by vibration of the container 1. This improves the support for the bowls by the granulate * material. The container 1 can, for example, be attached to an electrically driven »- compression table, which is shown in FIG. is indicated as a dashed rectangle 18. The shell shapes are now prepared for the casting, and this will be more common Way done. Dx ~ * part of the bolted material melts and burns most of the polyethylene bags, so that gases evolving during the Eir jussas flow through the Know walls of the shell shapes escape.

After a short cooling-off period it becomes fluid again! - sizing air is fed into the air box, uei the material 2 to fluidize, after which the Balter 7 approaches the container · «· can be lifted. If during the dialing a signal of the Dishfonaen takes place 1st, the wire mesh base holds 12 dl · parts when lifting the baltter out of the container, so that the material 2 cannot be contaminated. The process can then be repeated with old new shell shapes.

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It can be seen that the shell molds are securely supported during pouring, so that a reduction in the wall thickness of the shell molds is made possible. Such a reduction reduces the filling and solidification time in mold shell production and a smaller amount of shell molding material is required.

Using a fluidized bed as described above to facilitate the filling of a number of molds in succession has been found to increase the temperature of the material of which the fluidized bed is made. Even if the temperature of the material W up to 18O ° C rises, the protection conferred by the plastic sachet during the time in which the molds are lowered into the fluid bed before the sprue, not compromised. Of course there is a higher temperature rise for the granular material as the mold is filled and this destroys the polyethylene bag. However, during the time in which the cast metal solidifies and until the onset of a fresh mold, the temperature of the granulate material has fallen back to the value given above.

The method described above can easily be used in an automated form in a foundry. Corresponding advantages t devices can be developed in verschiedenster Ausführungeform. For example, a number of containers similar to the container 1 described above can be arranged in a row under a lifting mechanism , which is designed for lowering a filled holder into a container and later lifts the holder out of the container again after the GuB. The series of containers will always have one or more waiting to receive holders with empty shell molds, while in one or more others the metal poured into the shell molds is just solidifying and finally from one or more others

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Containers the holder straight to remove bind as the cast metal are sufficiently solidified that the container from the supporting Material bed can be removed.

Alternatively, multiple containers can be arranged on a turntable which is moved through a series of stations. In the first of these stations, a holder with empty shell molds is inserted into a container, its supporting material is fluidized. Fluidization takes place in a second station finished, and the molds are filled, after which the container through a cooling station is led into a discharge station, where the holder is removed and transported to one place, where the finished castings are removed from the molds. A device of the type just described is in detail shown in FIG. 3.

A sequence of containers 20 is on a turntable 19 arranged, each of which is generally similar to that in Figs illustrated container is. The lines 21 of the container 20 are jointly connected to a central plenum chamber 22 which contains a blower with an electric motor drive (not shown) that as a source of fluidizing air with high throughput, however serves relatively low pressure. Automatically actuated flow control valves 23 control the intake of the fluidizing air in the air boxes of the containers. The valves 23 can for example * cam actuated when the turntable «moves around the containers through the sequence of stations.

The shell mold holding device denotes the turntable via a Conveying device supplied, which is indicated diagr — like at 24 is. The container can have a raised guideway uda * s «n, on which the loaded 8chal «nformhalt« r from a (not allowed *, ' installed) transfer station «u a ·» container in the ttelluftg

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-ΙΟ-be brought and then lowered into the container. In the position I, the valve 22 of the container is open and the granulate material is fluidized in it. If the keeper is in the desired position in the container, the turntable is rotated further and conveys the container into position II, in which the valve 22 is closed. There is no fluidization and, if necessary, is the granulate material is compacted by vibration of the container. The following container is now in position I. ^ been brought and the peeling fogger inserted into the container. The turntable then continues to rotate and transports the first-mentioned container to position III. In this position, the container is located near a sprue or sprue for the introduction of molten metal from a crucible (not shown) into the shell molds. The GuB begins in position III and can be continued in position IV or beyond, depending on the size of the shell shapes.

A further rotation of the turntable advances the container in stages up to position V, where valve 22 opens is so that fluidizing air can "enter the air box of the container and thus fluidize the granular material in it," so that the shell holder can be removed with a crane. Dl «removal takes place by means of a diagransuurtlg at 25 shown conveyor device similar to the conveyor device 24 mentioned above Holder is brought to a processing station by means of the conveyor device 25, where the sole foraen are removed, including the To expose cast parts. The container now moves further into position 6, where the valve 22 is closed and the fluidization des Granulataater ^ as in the container is omitted.

The route "between positions IV and V forms" one Kuhlione, in which the Gufinetall solidifies. The Folylthylenslck

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are burned off during the movement of the container along this distance, thus during the cast iron and subsequently developing gases can escape through the shell mold walls.

It is preferred to have the container at station I. Subject to vibration because this promotes uniform fluidization. Also provides after switching off the flooding The sustained vibration of the container ensures that the Fluid bed collapses and compacts quickly. The vibration will stop within a short time, for example 2 to 4 seconds after the end of the fluidization

As explained above, the holder for the shell molds can be designed in the most varied of ways, depending on the shape, size and number of the shell molds to be accommodated. In addition, other possibilities for supporting the holder in the container can also be used. The depth to which the holder is lowered into the container must be chosen so that the granulate material of the bed cannot penetrate into the pouring openings of the shell molds, neither during insertion nor after the fluidization has ended ( before pouring. ♦ . "

A grid or "ine group of crossbars can close" be arranged the container bottom transversely, but it must be ensured that the fluidization of the bed does not adversely _t, is influenced · The tab is than lowered into the tank until it on the grid or rests on the crossbars.

Such a construction is unsuitable for the application in connection with Sobalengußfonen whose pouring openings not all « have the same height above the Hdena de «Belters, on the they sat.

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BATH ORIGINAL

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In this case, a modified design of the holder would have to be selected with hooks or projections for engagement with the top edge of the container »which are adjustable for setting the depth to which the holder is lowered into the container · In another embodiment of the holder, hooks or Projections are provided to keep the molds in such a position to keep that their sprues are all level above the bottom of the holder.

It is understood that it is not essential to the invention that the wire mesh floor, which was mentioned above, one with the Forms holder connected component. The wire mesh floor can be a separate component with handles or other devices for pulling the wire mesh out of the container in certain Intervals to remove debris and other debris, which may have accumulated in the granular material of the container. The wire mesh floor can be superfluous to be withdrawn each time after a group of filled shell molds has been removed from the container.

Claims t

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Claims (1)

- 13 patent claims 1) Process for the production of shell castings, at which the shell molds are supported by refractory granulate material, characterized in that a fluidizing gas is passed through the granulate material for formation a granular fluid bed, while reducing the permeability of the shell molds relative to that of the fluid bed to the gas is for the purpose of guiding the gas essentially through the Granulatmateriäl that the shell molds in the fluid bed up to one be used to such a depth that when the Fluid bed, the shell molds supported by the refractory granulate material, but the pouring opening (s) above the Granular material surface are that the fluid bed is brought to collapse by switching off the gas supply, and that after casting, gas is again passed through the granulate material to form the fluid bed and the shell molds can be removed. 2) Method according to claim 1, characterized in that that the permeability of the shell molds is reduced by treating the same in such a way that the molds with a Substance are enveloped during the casting process gets destroyed. 3) ■ method according to claim 2, characterized in that the forms with a cover, a sack or a container be enveloped from the substance. 4} The method according to claim 2, characterized in that the outer surfaces of the molds are coated with the substance. - 14 - 109824/1231 bad original 5) Method according to claim 3, characterized in that that the substance is a plastic. 6) Method according to claim 5, characterized in that the substance is polyvinyl chloride. 7) Method according to claim 4, characterized in that that the substance is paraffin wax. 8) Method according to claim 1, characterized in that that reducing the permeability by covering ™ the outer surface of the shell mold with a substance which essentially maintains the permeability of the mold for gases evolving during casting 9) Method according to claim 8, characterized in that the substance is bentonite. 10) Method according to claim 1, characterized in that the reduction in permeability by closing the mold pouring funnel takes place before it is inserted into the fluid bed and that the funnel is opened again for the GuB will. 11) The method according to claim 1, characterized in that the dl · reduction dmx peraeability is brought about by using a refractory granulate material as a basket size such that its permeability 1 * fluidised «« state is considerably greater than that of the shell gufifoxnen. 12) Method according to one of the preceding claims, characterized in that the refractory Gratmlataaterlal a thermal conductivity, which is higher than the usual forauiande, as well as a gas permeability far above that of the Sch & lengu & fonten owns & AD ORIGINAL - 15 - 109924/1231 13) Method according to one of the preceding claims, characterized in that the granulate material is compressed after the fluid bed has collapsed before casting. 14) Device for performing the method according to a of claims 1 to 12 with a container for the granular material, characterized in that the container «inen. iluidisiergaspermeablen, but for the granulate material itself has impermeable soil, which is an act of a plenum chamber forms, which is connected to a fluidizing gas source via a line with a control valve, and that a device J for lowering and lifting out the cast shell fora in the or from the granulate material in its fluidized state is provided. , 15) Device according to claim 14, characterized in that that the device has a plurality of containers and a transport device for moving the container along a predetermined As well as a main plenary committee to whom the Plenum channels assigned to individual containers can be connected. 16) Apparatus according to claim 15, characterized in that the control of the valves by moving the container of one to the other station, the distance along triggered UERT such \ · that the valve close upon arrival of the container at a UNLOAD · "and loading station for blow-drying · di opening and at the next station. 17) Device according to claim 16, characterized by Vibration devices for the containers in the loading station and / or the station following this for the compaction of the granulate material BATH 109824/1231