EP1689543A2

EP1689543A2 - Method for liberating cast parts from remaining molding sand, and device for carrying out said method

Info

Publication number: EP1689543A2
Application number: EP04802757A
Authority: EP
Inventors: Dieter Johnen
Original assignee: Elino Industrie-Ofenbau Carl Hanf & Co GmbH
Current assignee: Elino Industrie-Ofenbau Carl Hanf & Co GmbH
Priority date: 2003-11-21
Filing date: 2004-11-18
Publication date: 2006-08-16
Anticipated expiration: 2024-11-18
Also published as: WO2005051573A2; EP1689543B1; DE502004009434D1; WO2005051573A3; DE10354493A1; ATE429990T1

Abstract

Disclosed are a method for liberating cast parts from remaining molding sand, especially sand cores, and a device for carrying out said method. The cast parts (6) to which the remaining molding sand sticks are introduced into the heated drum (1) of a furnace system, the bottom area of said drum (1) being filled with a bed of loose pourable material (4). The drum (1) is made to rotate when the cast parts are guided therethrough such that the loose pourable material (4) is conveyed from the bed of pourable material into the top area of the drum and is thrown down onto the cast parts (6) so as to detach and destroy the sticking remaining molding sand. In this manner, the sticking remaining molding sand can be removed while the dwell time of the cast parts (6) in the furnace system is kept particularly short.

Description

Process for removing cast sand residues from castings and device for carrying out the process

The present invention relates to a method for removing cast sand residues from castings, in particular sand cores.

In the case of relatively complicated castings, for example aluminum castings, such as engine blocks, it is relatively difficult to remove the remains of the casting sand adhering to the castings. In particular, it is difficult to remove sand cores that are located within the cavities of the castings. Such sand cores are generally held together using a suitable binder, for example organic substances that can be burned out, and form relatively solid bodies.

Methods for removing cast sand residues from castings, for example for coring aluminum castings, are known. These processes work in a mechanical, pneumatic or thermal manner, for example in stationary fluidized bed furnaces. Continuous thermal processes are known, for example, from EP 0 546 210 B2 and EP 0 612 276 B1, in which the coring, the heat treatment of the castings and the sand regeneration are combined. In particular, in the above mentioned stationary fluidized bed furnaces.

In these known methods, the castings are moved continuously through an oven chamber in which there is a heated gas atmosphere. The hot gas atmosphere, which is under a suitable excess pressure, burns out the binder holding the sand cores together and frees the castings from the sand adhering to them. The loosened sand is collected in the lower area of the furnace chamber, removed from the furnace and regenerated.

The present invention has for its object to provide a method of the type specified, which is particularly quick and easy to carry out.

This object is achieved according to the invention by a method for freeing castings from casting sand residues, in particular sand cores, which comprises the following steps:

a. Introducing the castings with the sand residues into the heated drum of an oven system, which is filled in its lower region with a bed of loose bulk material;

b. Passing the castings through the drum and thereby rotating the drum and thereby conveying the loose bulk material from the bed into the upper drum area and throwing the same onto the castings to detach and destroy the adhering casting sand residues;

c. Removing the amount of sand from the drum that exceeds the amount of bulk material initially present; and

d. Take the cleaned castings out of the drum. The process according to the invention is based on the basic idea of applying heated loose bulk material to the cast parts with the casting sand residues by throwing them down onto the castings from the upper area of the drum interior, thereby breaking up the adhering casting sand residues while burning out the binder and detaching them from the casting. The inside of the drum is therefore not operated with excess pressure, and no fluidized bed or a targeted gas flow is used. Instead, the remains of the pouring sand are removed solely by the force of gravity of the dumped bulk material in connection with the heat transfer contact caused by it, which leads to burning out of the binder. The bulk material used for throwing is preferably at a high temperature and has a temperature of 500 ° C. or more, for example.

The throwing material used in the method according to the invention is preferably the same material as it adheres to the casting, ie the same casting sand. In this way, a separation of the throwing material from the detached pouring sand is not necessary, which would be the case if a different particulate material was used as the throwing material, for example other sand particles and the like. According to the invention, the casting sand used as the throwing material thus mixes with the detached casting sand residues in the lower region of the drum, and the mixed casting sand material is conveyed back into the upper drum region by the drum rotation and is thrown off there again. In this way, the cast parts are permanently subjected to cast sand that is thrown off during their movement through the drum. The amount of sand accumulating in excess of the amount of casting sand initially present is removed from the drum in order to maintain an approximately equal bed of casting sand in the lower area of the drum. Nature- A slightly rising sand bed can also be accepted as long as this does not affect the circulation or continuous conveying of the casting sand in the upper drum area.

In another embodiment of the method according to the invention, a different material, for example metallic or ceramic solids, is used as the bulk material than the casting sand adhering to the castings. The invention also includes embodiments in which mixtures of the same pouring sand and other bulk materials are used. An embodiment is particularly preferred in which a casting sand bed is used, in which ceramic or metallic solids are contained. Glass particles can also be used alone or mixed with pouring sand.

If materials other than the casting sand adhering to the castings are used as the casting material, the casting sand is separated from these other materials, for example sieved, and removed from the drum, while the other casting material remains in the drum. In the case of mixtures of other bulk material and pouring sand, only part of the pouring sand, which accumulates as the castings pass through the drum, is separated and removed from the drum.

In general, any bulk material that has the required hardness and whose abrasion is not too great can be used as a throwing material. As for the shape of the rubble material, any shape can be used (round shapes, angular shapes) as long as the purpose of the present invention is achieved. The most suitable forms are to be determined empirically. After the castings have been subjected almost continuously to the high-temperature cast sand on their way through the drum, at the end of their way through the drum they are almost free of any remaining sand and can be removed from the drum. The remains of pouring sand, which the castings may still carry out, naturally do not play any role for the bed of bulk material used inside the drum, since this is constantly filled up with new pouring sand that comes from the detached remains of pouring sand. Only at the beginning of the process must a bed of loose rubble be set up inside the drum. Later, this bed is continually supplemented with detached remains of pouring sand, with excess pouring sand being removed.

In the method according to the invention, the drum wall is heated in order to keep the bed of bulk material arranged inside the drum at a substantially constant high temperature. The bed of bulk material located in the drum before it is introduced into the drum is preferably heated before the start of the process, so that a correspondingly high-temperature material bed is already present when the first casting is introduced.

The castings themselves can be introduced into the drum in the temperature state in which they leave the casting system.

In a further development of the method according to the invention, the interior atmosphere of the drum is determined in relation to the treatment of the castings. If, for example, the castings leaving the foundry system are to be subjected to an annealing process, the atmosphere in the drum is adjusted with respect to its composition or its temperature so that this annealing process can be carried out. Advantageously, the cleaned castings led out of the drum are subjected to a further cleaning process by blowing in order to also remove the last adhering sand particles.

In a particularly preferred embodiment of the method, the castings are continuously fed through the drum. As a result, the method according to the invention can be carried out particularly quickly and easily. However, this does not exclude that discontinuous conveying of the cast parts (step by step, cycle, etc.) is also possible. In general, it can be said here that an introduction into the drum at one longitudinal end, conveyance by the drum and execution at the opposite longitudinal end are preferred. This should also not rule out that loading and unloading is carried out at the same longitudinal end of the drum (so-called retort furnace). With intermittent funding, there is the possibility of controlling the dwell time.

The castings can be conveyed within the drum horizontally or at an angle. Funding can be centered or eccentric.

In addition, during their movement through the drum, the cast parts can be pivoted or rotated, in the drum rotation direction or in the opposite direction to the drum rotation direction, in order to achieve the most uniform possible application of the cast sand to the cast part. As a result, parts of the cast part are also exposed to the thrown-off bulk material, which would not be hit by the bulk material without rotating or pivoting. A heat treatment of the cast parts which is expediently carried out immediately after the method according to the invention can be carried out using the sensible heat of the cast parts and has a substantially improved uniformity and thus quality with an equally considerably reduced duration.

As studies have shown, the residence times in the process according to the invention are considerably shorter than in the thermal processes known to date. This results in considerable time savings that cannot be overestimated.

The present invention further relates to an apparatus for performing the method described above, which comprises an oven system. The device is characterized in that the furnace system has a rotating heated drum, the inside of which is provided with conveying elementsή which convey the bulk material from the bulk material bed upwards along the drum wall and drop it onto the castings. These conveying elements are preferably designed as blades. The conveying elements are preferably arranged at a distance along the inner circumference of the drum. When the drum rotates, they pass through the bed of rubble arranged in the lower area of the drum and convey a part of the rubble along the wall of the drum to the upper area of the drum, from where the bulk material is thrown onto the castings below. In this way, the preferably high-temperature bulk material gets onto the casting sand residues (sand cores) adhering to the castings, whereby these are broken up by the burning out of the binder and released from the castings. A combination of mechanical and thermal effects is therefore used to remove the remains of the casting sand. The drum preferably forms part of a drum or rotary retort oven. In the drum furnace, the castings are loaded at one end of the furnace and removed at the opposite end of the furnace. A rotary retort oven has a closed end, while loading and unloading take place at the other end.

In the present description, the term "drum" is always used uniformly, although this means both the rotating element of a drum furnace and that of a retort furnace.

As already mentioned, the drum is heated indirectly, i.e. there is no direct heating inside the drum, but the drum wall is heated from the outside. Optionally, an additional heater for direct heating can be provided. Such drum ovens or rotary retort ovens with indirect heating are known and need not be described in detail at this point. Indirect heating can be carried out, for example, by heating with gas, oil, electrically, inductively, by microwaves, etc.

The castings to be freed from the casting sand residues are moved through the drum or in the drum with the aid of a product carrier. Such a product carrier can be designed, for example, as a slideway, vibrating table, walking beam system, chain-like flow system, etc. It is essential that the castings can be largely freely contacted by the dropped bulk material without being hindered by the product carrier. This is achieved in any case in a particularly preferred solution of the invention, in which the device places a rust-like or cage-shaped product carrier inside the drum. has. In general, the product carrier used can be designed to be pivotable or rotatable, so that the cast parts arranged on or in the product carrier can be pivoted or rotated during their movement within the drum in order to achieve a largely uniform loading of the bulk material.

The furnace system is preferably designed as a continuous system, but can also be designed as a rotary retort furnace system. Here, the castings move in the forward and backward directions.

The product carrier can also be designed as a conveyor belt, or the product carrier can be arranged on a conveyor device, for example a conveyor belt.

The furnace system preferably has suitable locks on the inlet and outlet sides in order to enable the castings to be introduced and carried out without the furnace atmosphere escaping to the outside or the ambient atmosphere penetrating into the furnace. Such locks are known and need not be described in detail here.

Baffle plates are preferably used to determine the height of the bed of bulk material within the drum. These can be spiral-shaped and run around the inner circumference of the drum so that they can be used to fill or empty the drum when the direction of rotation is reversed.

The excess amount of pouring sand is also discharged from the drum in a suitable, atmospheric manner. It can then be fed to conventional core sand regeneration in order to enable it to be used again in the casting installation. The invention is explained in detail below using an exemplary embodiment of a drum furnace system in conjunction with the drawing. Show it:

Figure 1 is a schematic cross-sectional view of a drum furnace; and

Figure 2 is a schematic longitudinal sectional view of the drum furnace of Figure 1 on a different scale.

The drum furnace shown schematically in FIG. 1 has a rotating drum 1 which is rotatably mounted within a suitable storage rack, which is indicated schematically at 2. Such drum ovens are known and therefore do not need to be described in detail here.

The rotatably mounted drum 1 is heated indirectly, i.e. from the outside via heating devices not shown in FIG. 1 (for example a suitable gas heater), so that the drum wall is heated. Inside the drum 1 there is a suitable gas atmosphere, which is maintained almost unchanged inside the drum due to the formation of inlet and outlet locks for the cast parts to be treated and the pouring sand to be introduced and removed. The respective locks for the introduction and execution of the castings and the casting sand are not shown in FIG. 1.

Figure 1 also shows a product carrier 5 in the form of a cage, in which a casting 6 to be treated is located. The product carrier 5 rests on a conveyor belt 7 which carries the product carrier into the drum, through the drum in the longitudinal direction thereof and out of the drum moved out again. Such product carriers are also known.

Suitable devices (not shown) are also provided in the interior of the drum, which pivot the product carrier 5 clockwise in FIG. 1 about the central longitudinal axis of the drum. When the product carrier 5 moves through the drum, the cast part 6 arranged in the product carrier 5 is pivoted.

In the lower part of the drum 1 there is a bed of pouring sand (bed of bulk material) 4, which is erected there before the introduction of the first casting 6 with casting sand residues into the drum. While the casting 6 passes through the drum in the longitudinal direction, the drum rotates, with conveying elements 3 in the form of blades arranged on the inside of the drum wall conveying the casting sand from the bed 4 in FIG. 1 counterclockwise into the upper region of the interior of the drum and when this upper area has been reached, cast it onto the casting 6 located underneath, which is fixed in the cage-shaped product carrier 5. Due to the indirect heating of the drum wall, the casting sand bed 4 has been brought to a correspondingly high temperature, for example about 500 ° C., so that the casting part 6, which is covered with casting sand residues, is now subjected to hot loose casting sand from above. Due to the impact of the hot pouring sand on the adhering pouring sand residues (cores) (abrasive effect) and the associated thermal contact, the pouring sand build-up is broken up by burning out the possibly still existing binding agent, detached from the casting and destroyed, so that the formerly solid masses become loose Collect the pouring sand in the lower area of the rotating drum and enlarge the pouring sand bed 4 there. In order to keep the height of the bed 4 approximately constant, excess pouring sand is manent removed from the drum.

Figure 2 shows a schematic longitudinal section through the drum furnace of Figure 1, drum 1 and storage rack 2 are shown purely schematically. Via a schematically indicated inlet lock 9, the castings 6 to be treated, provided with pouring sand buildup, which are arranged within the cage-shaped product carriers 5, reach the inside of the drum 1 via the conveyor belt 7, are continuously moved through the inside of the drum and pass through the schematically indicated outlet lock 10 out of the drum again. Inside the drum they have been pivoted against the direction of rotation while the drum is rotating. At 4 in the lower part of the interior of the drum, the poured sand bed is indicated, from which the pouring sand is drawn off via an outlet 8.

Finally, it should also be mentioned that the invention also includes an embodiment in which the actual drum does not rotate, but rather a frame arranged in the drum, which is arranged adjacent to the drum wall and carries the conveying elements (blades) for the bulk material. A corresponding effect is achieved in this way.

Claims

claims

1. A method for freeing castings from casting sand residues, in particular sand cores, with the following steps:

Introducing the castings with the sand residues into the heated drum of an oven system, which is filled in its lower region with a bed of loose bulk material; b. Passing the castings through the drum and thereby rotating the drum and thereby conveying the loose rubble material from the bed into the upper drum area and throwing it onto the castings to detach and destroy the adhering casting sand residues; c. Removing the amount of sand from the drum that exceeds the amount of bulk material initially present; and d. Take the cleaned castings out of the drum.

2. The method according to claim l, characterized in that the same pouring sand is used as the bulk material, which adheres to the castings.

3. The method according to claim 1, characterized in that metallic or ceramic solids are used as bulk material.

4. The method according to claim 1 or 3, characterized in that the pouring sand is sieved from the original bulk material.

5. The method according to any one of the preceding claims, characterized in that the casting sand detached from the castings is thrown onto the castings together with the original bulk material.

6. The method according to any one of the preceding claims, characterized in that the drum wall is heated.

7. The method according to any one of the preceding claims, characterized in that the bed of bulk material is heated in the drum before the introduction of the castings.

8. The method according to any one of the preceding claims, characterized in that the castings are introduced into the drum in the temperature state in which they leave the casting system.

9. The method according to any one of the preceding claims, characterized in that the bulk material / pouring sand quantity in the drum is kept substantially constant.

10. The method according to any one of the preceding claims, characterized in that the interior atmosphere of the drum is determined with respect to the treatment of the castings.

11. The method according to any one of the preceding claims, characterized in that the cleaned castings led out of the drum are finally cleaned by blowing.

12. The method according to any one of the preceding claims, characterized in that the castings are guided continuously through the drum.

13. The method according to any one of the preceding claims, characterized in that the drum is heated indirectly.

14. The method according to any one of the preceding claims, characterized in that the castings are pivoted or rotated during their movement through the drum.

15. Device for carrying out the method according to one of the preceding claims with a furnace system, characterized in that the furnace system has a rotating heated drum (1), the inside of which is provided with conveyor elements (3) which remove the rubble material from the Promote the bed of bulk material (4) along the drum wall and throw it onto the castings (6).

16. The apparatus according to claim 15, characterized in that the drum (l) is part of a drum or rotary retort oven.

17. Device according to one of claims 15 or 16, characterized in that the drum (1) has a heating device for indirect heating and optionally an additional heater for direct heating.

18. Device according to one of claims 15 to 17, characterized in that the conveying elements (3) are designed as blades.

19. Device according to one of claims 15 to 18, characterized in that it has a rust or cage-shaped product carrier (5) within the drum (l).

20. Device according to one of claims 15 to 19, characterized in that it has a pivotable or rotatable product carrier (5).

21. Device according to one of claims 15 to 20, characterized in that the furnace system is designed as a continuous system.

22. Device according to one of claims 15 to 21, characterized in that the furnace system has suitable locks on the inlet and outlet sides.

23. Device according to one of claims 15 to 22, characterized in that the drum (1) has baffle plates for determining the height of the bed of bulk material (4).

24. The device according to claim 23, characterized in that the baffle plates are spiral and run all around and serve for filling or emptying when the direction of rotation of the drum (ι).