WO1997001406A1

WO1997001406A1 - Feeder for use in casting molten metal

Info

Publication number: WO1997001406A1
Application number: PCT/DE1996/001150
Authority: WO
Inventors: Franz Hampel; Ulrich Lanver; Peter Peters; Detlef Reichelt; Klaus Riemann
Original assignee: Chemex Gmbh
Priority date: 1995-06-28
Filing date: 1996-06-27
Publication date: 1997-01-16
Also published as: ATE182821T1; DE59602611D1; AU6297696A; EP0779844B1; ES2135238T3; EP0779844A1; DE29510068U1

Abstract

Disclosed is a feeder for use in casting molten metal in casting moulds. It comprises a hollow mould body made from an exothermic material and closed off at its top end by a horizontal wall section. The side wall (9) of the feeder is so designed as to be outwardly convex from the top wall section (5), merging at the bottom end into an admission section (7) also referred to as a feed neck, and is provided with several ribs (12) which project into the inner chamber; these ribs merge at their ends with the upper wall or admission section. The feeder is preferably designed in such a way that the outer contour of the side wall (9) from the upper rim of the upper wall (5) as far as the bottom edge of the admission section (7) is essentially tear-shaped in longitudinal section, while the inner contour of the side wall (9) at least in the lower region of the feeder is essentially egg-shaped in longitudinal section between the ribs (12). The feeder is characterised in that it has a small standing surface without requiring undercuts at the lower feeder end, while also having a large volume, good pressure resistance, low weight and excellent exothermic properties.

Description

Feeders for use in casting molten metal

The invention relates to a closed feeder for use in casting molten metal. Such feeders are integrated into this during the production of a casting mold and form a space surrounded by molding material, which has a passage to the mold cavity and, during casting, is filled with liquid metal by the casting flow, which flows back to the casting during the solidification process and the volume deficit to compensate for the solidification of the casting. In this way, the formation of so-called blowholes (that is, shrinkage cavities caused by the metal volume contraction during the solidification process) is prevented.

In order to ensure a proper feeding process, the metal in the feeder must solidify later than the metal of the casting, ie the modulus (ratio of volume to surface) of the feeder must be greater than that of the casting. At the same time, the smallest possible amount of metal should remain in the feeder after solidification for cost reasons, and for this purpose the walls of the feeder are often formed from an exothermic material, for example an aluminothermic mixture. Such a material is ignited by the liquid metal, and therefore an exothermic reaction takes place after the penetration of the pouring flow into such a feeder, by means of which heat is supplied to the metal located in the feeder interior. This remains through the Heat supply is liquid longer than the metal in the mold cavity of the mold and is therefore better usable for feeding.

Many casting molds are produced with the aid of a model plate, which specifies the inner contour of the mold cavity and, in each case at the points where a feeder insert is required, with a holding device, e.g. a mandrel for fixing the position of the feeder insert is provided. After the feeders have been placed on the mandrels, the sand is then applied to the pattern plate and compressed into the casting mold, the term "sand" being understood here as a synonym for all types of granular molding materials and molding material mixtures.

In recent times, for various reasons, feeders are increasingly required which take up as little space as possible on the model plate. This can only be achieved incompletely with conventional feeders. Exothermic feeders of conventional design generally have an essentially cylindrical, slightly frustoconical shape, and their internal geometry is such that the cross section of the passage leading to the casting corresponds to the maximum internal cross section of the feeder, that is to say it means a very large footprint. By arranging a crushing core (in principle this is a plate with a smaller opening compared to the feeder outlet, for example made of croning sand or another suitable material), the cross section of the passage can be significantly reduced at the lower feeder end, and the footprint can also be reduced are reduced with the help of the crushing core in that the side wall of the crushing core is tapered from the lower outer feed end, but this does not yet lead to the desired success. The conical indentation of the crushing core side wall results in an undercut below the feeder, which results in inadequate compaction of the molding sand in this area. Therefore, the cone angle, based on the level of the footprint, must not assume small values, which in turn limits the achievable reduction in the footprint of the feeder. In this context, it is further aggravated that the conventional feeders have a large wall thickness in order to withstand the compression pressure customary in modern high-performance molding plants and to be able to offer enough exothermic energy, so that the lower outer feeder end must have a large distance from the feeder center axis . This is where the invention comes in. Its task is to specify an exothermic feeder which has a very small footprint, a high feeder module, a sufficiently large feeder volume and a very high degree of efficiency for the exothermic reaction. Furthermore, the external shape of the feeder should avoid undercuts so that the sand can be brought into good contact with the outer surface of the feeder and with the adjacent model plate and can be compacted well everywhere in the production of a casting mold in the usual molding plants.

This object is achieved according to the invention in that the side wall of the feeder is convexly curved outwards from an upper, essentially horizontal wall part, merges at the lower end into a passage part, also referred to as a feeder neck, and has a plurality of frames projecting into the interior , which at their ends merge into the upper wall or the passage part. Further features are defined in the subclaims.

Through the interaction of its features, the feeder according to the invention ideally fulfills all requirements. As a result of the convex shape, it not only has an enlarged module, but also an aerodynamically favorable outer contour, preferably in the form of an inverted drop standing on the tip, which allows good covering with sand and good compaction of the sand, and likewise one aerodynamic inner contour, which is preferably egg-shaped at least in the lower region of the feeder and ensures a good outflow of the feed metal through the passage. The inner frames result in an extraordinarily high compressive strength, enable a smaller wall thickness of the outer wall (and thus a weight that is at least 1/3 smaller than that of a conventional feeder of the same volume) and also ensure, since they are also made of exothermic material , for a better introduction of the exothermic heat into the feed metal, thus increasing the exothermic efficiency. Overall, the volume of the feeder need only be slightly larger than the feed requirement of the casting calculated for the application.

The feeder according to the invention is expediently provided with a crushing core, but does not necessarily require such a one (for example if a spring mandrel is used or the passage has a molded-on breaking edge that can be arbitrated if necessary). If a crushing core is used, its side wall is preferably shaped in such a way that it continuously follows the outer contour of the feeder and in this way forms a relatively large angle (for example of approximately 60 °) with the level of the storage surface. The side wall of the crusher core can also be steeper (at an angle of up to 90 °), but then no longer results in the optimally small, but rather a slightly larger footprint, and on the other hand should never be flatter than the side wall of the feeder by one Avoid undercuts at the lower end of the feeder. If the ratio of the feed volume to the size of the footprint is used as a parameter (a large value stands for large volume and small footprint, as desired), in the preferred embodiment of the crusher core with a side wall that continuously continues the outer contour of the feeder, this results in a great deal Favorable value in the range of about 35 - 40 cm, while with conventional feeders of the same volume only values in the order of 10 cm can be achieved. The same also applies to the ratio of the largest feeder diameter to the size of the footprint as a parameter, which in the preferred embodiment assumes a value of about 1.7 cm ^-1 and for the conventional feeders only in the order of about 0.5 cm ^-1 This also impressively confirms the number of success achieved with the invention.

The invention is explained in more detail below in exemplary embodiments with reference to the drawing. Show it:

Fig. 1: The longitudinal sectional view of a feeder according to the invention

(Section plane I-I in Fig. 2), and

2: cross-sectional segments of the feeder according to FIG. 1 (section plane IIA-IIA, IIB-IIB and IIC-IIC in FIG. 1.

3 and 4: sectional views of another embodiment of the invention analogous to the views shown in FIGS. 1 and 2.

The feeder 3 shown in FIGS. 1 and 2 is closed at the top by a flat end wall 5 and has a convexly bulged side wall 9 and a lower feed neck 7, which has a crushing core 1 connected is. The feeder 3 is made of exothermic material and the crusher core 1 can be formed from croning sand, for example. It is provided in the usual way with a breaking edge 2 in order to facilitate the separation of the feeder from the casting after casting.

The feed neck 7 and the adjoining crushing core 1 delimit the passage 4, which creates the connection between the interior 13 of the feeder and the mold cavity to be fed. At the same time, however, the feeder neck is also designed as a guide for a mandrel (not shown further), a so-called short mandrel being assumed in the example of FIGS. 1 and 2, which does not extend substantially beyond the feeder neck 7 into the interior 13 and that in a centering section 6 of the spear neck is accommodated. The wall of the outlet opening 4 expediently has a funnel-like wall section 10, along which the mandrel is guided continuously to the centering section. Alternatively, however, a long mandrel can also be used, which extends through the interior 13 to the end wall 5 and engages with its upper end in a centering recess (see 26 in FIG. 3). In this case, the centering section 6 of the throat is unnecessary.

The annular underside of the crushing core 1 forms the footprint 8 of the feeder, and the outer contour of the lateral, convexly bulged side wall 9 extends from the upper end wall 5 to the footprint 8 in a constant curvature which is at the tip with the curvature of one is comparable to the drop and is therefore referred to as "drop-shaped". It can be seen that the footprint can be kept very small in this way and that the largest diameter of the feeder (at level AA) is at a relatively large distance from the footprint, with the result that despite the very small footprint good compression of the molding sand is also ensured in the critical area of the food neck.

In the interior 13 of the feeder, several, for example three, vertical frames 12, which are directed towards the feeder center axis MM and which consist of the exothermic material, are molded onto the bulged side wall 9. These frames can occupy up to 25% of the interior volume and in this example have vertically extending interior surfaces 14, the distance from which the center axis of the feeder MM is somewhat larger than the radius of the centering section 6. Furthermore, these frames 12 are arranged at the same angular distance from one another with respect to the center axis and each taper in the direction of the same isosceles trapezoid. They go at their ends on the one hand into the upper end wall 5 and on the other hand into the feeder neck 7 and give the feeder a greatly increased compressive strength, so that the side wall 9 can be made correspondingly thinner and the desired weight saving results. At the same time, these frames 12 of the interior of the dining room also prove to be particularly effective heat sources which locally increase the range of exothermic reaction heat. The heat released during the exothermic reaction of the frame material is almost completely released to the liquid metal within the feeder via the flanks and inner surfaces of the frames; Heating losses due to heat dissipation on the outer wall of the feeder 3 and from there to the molding sand which envelops the feeder are minimal.

The inner contour of the side wall 9 can be kept equal to the outer contour in the upper feeder half (constant wall thickness of the side wall) and merges into the passage 4 of the feeder neck with a constant curvature in the lower feeder half, so it is essentially egg-shaped in this area. This supports a uniform metal flow in the course of the feed and also has the advantage that the wall thickness in the lower feeder area increases continuously, as a result of which more exothermic material and thus more exothermic action can be brought into the lower feeder area.

Instead of vertical frames 12, other reinforcing elements can also be connected to the side wall 9 of the feeder, for example honeycomb-like structures. However, these are somewhat problematic in terms of production technology, so that vertical frames are preferred. The dargestell¬ th feeders with circular cross section, the three or a maximum of four frames are functional, while at feeders with different cross-sectional shapes that are referred to further below, a larger number may be seen from frames pre ^¬. When using a short mandrel, the frames 12 do not need to end at a distance from the center axis MM of the feeder, rather it does not bother if (in contrast to that shown in FIGS. 1 and 2) the central area aligned with the centering section 6 of The interior of the feeder is installed. This can even be preferred in individual applications.

3 and 4 show an embodiment of the feeder, which is intended for use with a long mandrel, but does not differ in principle from the embodiment according to FIGS. 1 and 2. For this reason, functionally identical parts are also designated with the same reference numerals but with an index line and are not explained again.

3 and 4, the contour of the feeder interior 13 'is egg-shaped not only in the lower feeder half, but also in the upper feeder half. In addition, the frames 12 'are rounded on their inner surfaces 14' and end flush at the passage 4 ', which in this case has no centering section analogous to section 6. Rather, the inner surfaces 24 of the frames in the upper feeder area assume the function of section 10 in FIG. 1 by reliably guiding the mandrel into the centering recess 26.

The feeder according to the invention can be made in one piece (as shown in the drawing) or in multiple parts (e.g. with a division level at the level of plane A-A of the largest diameter), the individual parts subsequently being combined to form a one-piece feeder, e.g. be glued. In terms of production technology, a two-part design is quite inexpensive, but the one-piece design also offers no problems in terms of production technology by specifying the internal geometry which is important for the desired success by means of removable cores made of a plastic material such as polystyrene or the like. Depending on requirements, these cores can be detached from the inside of the feeder or are pyrolyzed with metal when the feeder is finished or poured off.

The crusher core 1 or 1 'provided in the illustrated exemplary embodiments need not have a side surface 11 or 11' which continues the outer contour of the feeder, although this is the preferred embodiment. If an optimally small footprint is not required, but the advantages of the invention are to be exploited, the crushing core can also be cylindrical or steeply conical (with a cone angle) greater than about 60 °) extending side surface. On the other hand, a crusher core can be dispensed with if - as mentioned at the beginning - a spring mandrel is used, for example, or a crusher edge can be formed directly with the exothermic material of the food neck.

Moreover, the feeder does not have to have the circular cross-section shown in the drawing, but can also take any other cross-sectional shape (with a corresponding shape of the passage and the footprint), as is generally known for feeders. Typical are e.g. oblong-oval cross-sectional shapes. It can also, this is of practical importance especially for the lower portion of the feeder, a circular cross-sectional shape continuously change into an elongated one.

Claims

claims

1.) Feeder for use in casting metals in casting molds, comprising a hollow molded body made of an exothermic material, which is closed at its upper end by a horizontally extending wall part, characterized in that the side wall (9) of the feeder from the upper wall part (5) proceeding convexly curved outwards, merging at the lower end into a passage part (7), also referred to as a feeder neck, and having several frames (12) projecting into the interior, which at their ends merge into the upper wall or the passage part.

2.) Feeder according to claim 1, characterized in that the outer contour of the side wall (9) from the upper edge of the upper wall (5) to the lower edge of the passage part (7) of the feeder in the longitudinal sectional view is substantially teardrop-shaped.

3.) Feeder according to claim 1 or 2, characterized in that the inner contour of the side wall (9) at least in the lower region of the feeder in the longitudinal sectional view between the frames (12) is substantially egg-shaped.

4.) Feeder according to one of claims 1-3, characterized in that a centering recess (26) for receiving a dome is arranged inside the upper wall part, the inner surface (14) of the frames (12) a greater distance from the The center axis of the feeder (MM) corresponds to the radius of the dome, and that the inner surfaces (14) of the frames (12) in the upper feeder area are designed as oblique guide surfaces (24) for introducing the dome into the centering recess .

5.) Feeder according to one of claims 1-4, characterized in that a crushing core (1) is attached to the passage part (7), the lower surface of which forms the footprint (8).

6.) feeder according to claim 5, characterized in that the

Side surface (11) of the crusher core (1) continues the outer contour of the feeder.

7.) feeder according to claim 5, characterized in that the

Side surface (11) of the crushing core (1) forms an angle between 60 ° and 90 ^° with the plane of the footprint (8).

8.) Feeder according to one of claims 1-4, characterized in that the lower surface of the passage part is formed as a footprint and a breaking edge is formed directly with the exothermic material of the passage part.

9.) feeder according to one of the preceding claims, characterized in that the feeder (3) made in one piece using a lost core or is composed of several separately manufactured parts.

10.) Feeder according to one of the preceding claims, characterized ge indicates that the feeder (3) has a circular cross-section or an elongated oval cross-section or a cross-section continuously transitioning from a circular shape into an elongated oval shape.