EP0890400B1 - Casting method for making metallic mouldings - Google Patents

Description

The invention relates to a casting method for manufacturing of metallic castings according to the generic term of independent claim.

In casting processes for the production of metallic Castings become castings, for example cast iron, specifically a gray cast iron alloy, in the liquid state a casting mold, for example one in a mold pit modeled sand mold or a mold, placed where it solidifies by giving off heat to the casting mold. In the Solidification runs complex chemical and physical Operations. In particular the spatial and temporal The course of solidification of the cast material has a decisive one Influence on the developing structure and thus the mechanical properties of the casting.

After solidification, the casting must still be Reaching a so-called unpacking temperature, the z. B. for gray cast iron alloys usually below 300 ° C is chosen to cool in the mold before leaving can be demolded. Also the spatial and temporal The cooling process of the cast material has an essential one Influence on the mechanical properties for example the internal stresses of the castings. Since that The casting material increasingly heats up the casting mold Cooling rate of the cast material with increasing dwell time in the mold and can, for example, before Unpacking temperature reached below 1 ° C decrease per hour. This is the cooling time of the Foundry comparatively compared to the solidification time long. For large-volume castings such as B. Engine housings of large diesel engines often result Cooling down of several weeks. Because in foundries Only a few molded pits are available for reasons of space stand in which such large-volume castings the long cooling times are producible essential limiting factor for the achievable Production capacity and are therefore below disadvantageous economic aspects.

Another disadvantage of known casting processes is in the fact that often larger, especially in Giesslingen Mass, the solidification process in the cast material, in particular the solidification time, not from a metallurgical point of view is optimal so that a structure is formed which does not have the desired properties. Therefore the structure of the casting must be removed after it has been demolded is, through time-consuming and costly thermal Aftertreatment, such as conversion annealing or Normalization annealing, can be changed.

Furthermore, known casting processes have the disadvantage that that the cooling process of the cast material often increases considerable and problematic residual stresses, in particular tensile stresses inside the casting leads. This problem is particularly pronounced in Castings that have a complex structure, such as for example engine housings for large diesel engines. Such motor housings (see e.g. Fig. 1) have numerous recesses, internal cavities different dimensions and partitions with very different wall thicknesses. Especially with such complex castings can withstand internal stresses very easily lead to dimensional changes or cracks, so that a very time and cost intensive thermal aftertreatment, for example, stress relieving is indispensable, to a reasonable quality of the casting guarantee.

EP-A-0 065 208 deals with the manufacture thick-walled, container-like cast iron castings with nodular graphite (spheroidal graphite iron), such as as Transport container used for used fuel assemblies become. To produce a fine-grained, low-segregation and pore-free casting structure is proposed Relentlessly building the mold core and the outer shape entire inner surface with a liquid, in the system evaporating liquid to cool and so pour to dimension that the cast iron solidifies in them before the eutectic solidification of the casting begins. The lost mold core includes an iron sheet jacket with welded-on lid, which covers the inner surface shape the thick-walled container. The sheet metal jacket and the lid are separated after cooling and from removed the casting.

DE-C-855 151 discloses a process for the production of steel blocks with which the solidification of the Foundry goods should be accelerated by less To generate internal defects in the structure. The mold according to DE-C-855 151 is a sand mold with an inner one Sheet metal jacket, which the outer boundary surface of the Steel blocks are formed and welded to the steel block. In the sand mold, several cooling coils are inlaid which water or compressed air is introduced. With these Cooling coils will cover the entire outer surface of the Steel blocks cooled.

Both methods have in common that both only for very simple symmetrical castings can be used. It will a lost sheet metal jacket that needs either the entire inner or the entire outer surface of the Casting forms.

Based on this state of the art, it is therefore one Object of the invention, a casting process for manufacturing metallic castings to provide the front does not have the disadvantages mentioned. The casting process should produce as economically as possible allow metallic castings. In particular, it should enable the process, especially in Giesslingen large mass, to significantly reduce the cooling times. Furthermore, the casting process should make it possible also complex structured castings such as engine housings for large diesel engines, where one elaborate thermal post-processing can be dispensed with can be accepted without sacrificing quality Need to become.

Of these tasks from a procedural point of view Solving object of the invention is by the features of the independent claim. The Casting method according to the invention for producing metallic castings from a cast material, in which the cast material in a liquid state in a mold, in particular a sand mold, is introduced and that The cast material solidifies in the mold and cools, whereby the Cast material in the mold controlled by a cooling system is cooled, is particularly characterized by that depending on the geometry of the casting and the desired metallurgical effects at least local spatial area of the casting is specified in which the cast material is heated in a targeted and controlled manner withdrawn that the cooling system for the controlled Deprivation of heat in terms of its placement and shape is adapted to this local spatial area, and that controlled heat extraction only by means of flowing Air is made from this local area. Through the Controlled cooling can be spatially and temporally Solidification process and / or cooling process in the cast material control actively and specifically. This allows especially the cooling time that the cast material needs, to reach its unpacking temperature, considerably shorten. Thus z. B. the mold pit in which the mold is much faster for new casting processes are available, so that a clear Increase in production capacity with the same Space requirement is made possible.

The cast material is in the mold in at least one Specifiable spatial area targeted and controlled Deprived of heat. Thus, for example, solidification of the cast material controlled by targeted heat extraction become. By this measure it is e.g. B. possible at least a spatial area of the cast material very much to quickly freeze. This has the advantage that the developing structure of the solidifying Foundry can be influenced in some areas. So z. B. in predefinable areas of the casting by targeted controlled and rapid solidification large Hardness values can be achieved without a thermal aftertreatment such as Transformational annealing is necessary.

It is also the casting method according to the invention preferred, the cast material in the mold in several Specifiable and controlled spatial areas To withdraw heat, being the different areas of heat extracted from spatial areas are essentially independently controllable. This has the particular advantage that the spatial course solidification and / or cooling active and can be influenced in a controlled manner. Thus, the mechanical properties of the castings already at the Influencing manufacturing in a controlled manner.

The heat is extracted by means of air, because air enters inexpensive, easy to handle and is safe cooling medium.

In a preferred procedure, means Temperature sensors at different points in the Poured the local temperature continuously recorded and the temperature profile that can be determined from it Control of cooling used. So you can constantly monitor and through spatial temperature profile actively influence the controlled cooling.

It is particularly important when the cast material cools down advantageous if the temperature gradient over the Foundry is minimized. This means that especially with complex structured castings such as Housings of large diesel engines, tensile stresses in the At least drastically reduce Giessling so that on thermal aftertreatment such as stress relieving can be dispensed with without sacrificing quality To have to buy. It is even possible inside of the casting to generate compressive stress.

The cooling system preferably comprises at least one Pipe system for the flowing air, through which the Foundry in at least one predeterminable spatial Targeted and controlled area of heat can be extracted. This constructively simple measure makes it possible spatial and temporal solidification and / or The cooling process in the cast material is controlled too influence.

Preferably there is direct contact between the Foundry and the pipe system avoided to damage to avoid the pipe system. The pipe system can for example in or between the sand cores of the Sand form run. The cooling system includes one preferred variant furthermore a transmission medium, which thermally connects the pipe system with the cast material coupled. This transmission medium can in the simplest execution sand or a sand core. Around to achieve better thermal contact can Transmission medium but also a better heat conductive Material, e.g. B. graphite. For example the pipe system partly on or in graphite plates that are in direct physical contact with the Stand cast material.

The cooling system preferably comprises at least two Pipe systems for air, through which the cast material in targeted and several predeterminable spatial areas controlled heat is withdrawable, the means of amounts of heat extracted from different pipe systems are essentially independently controllable. By this measure is possible, especially the spatial course of solidification and / or cooling to actively influence in the cast material. So you can according to Giessling or according to his desired Properties of each under metallurgical aspects most favorable course of solidification and / or cooling realize.

In particular, it is advantageous to provide a regulation which controls the amount of heat withdrawn so that the Temperature gradient over the cast material is minimal. Thereby tensile stresses in Giessling can be clearly seen reduce or even generate compressive stress without that Necessity of thermal post-treatments such. B. Stress relief.

Because there are no time-consuming and expensive thermal Post-treatments are required, this is the inventive Casting process particularly economical.

Other advantageous measures and preferred Refinements result from the dependent Claims.

Fig. 1

eine Darstellung eines Motorengehäuses in einer Formgrube zur Verdeutlichung eines ersten Ausführungsbeispiels der Erfindung,

Fig. 2

eine Seitenansicht eines Rohrsystems zum Wärmeentzug aus dem Kurbelraum des Motorengehäuses aus Fig. 1,

Fig. 3

eine Aufsicht auf das Rohrsystem aus der Blickrichtung III-III in Fig. 2,

Fig. 4

eine Darsteluung eines Rohrsystems zur Bodenkühlung des Motorengehäuses aus Fig. 1,

Fig. 5-9

schematische Darstellungen verschiedener Varianten für die Wärmeübertragung zwischen Giessgut und Wärmeträger,

Fig. 10

eine Darstellung eines Exzenterrads zur Verdeutlichung eines zweiten Ausführungsbeispiels der Erfindung,

Fig. 11

einen Querschnitt durch das Exzenterrad entlang der Schnittlinie XI-XI in Fig. 10,

Fig. 12

eine Aufsicht auf eine Kühlerplatte, und

Fig. 13

einen massiven Block mit einer dünnen Bohrung zur Verdeutlichung eines dritten Ausführungsbeispiels der Erfindung.

The invention is explained in more detail below with reference to the drawing and with the aid of exemplary embodiments. The schematic drawing, not to scale, shows:

Fig. 1

1 shows a motor housing in a mold pit to illustrate a first exemplary embodiment of the invention,

Fig. 2

2 shows a side view of a pipe system for extracting heat from the crankcase of the engine housing from FIG. 1,

Fig. 3

a view of the pipe system from the viewing direction III-III in Fig. 2,

Fig. 4

1 shows a pipe system for cooling the floor of the motor housing from FIG. 1,

Fig. 5-9

schematic representations of different variants for the heat transfer between the cast material and the heat transfer medium,

Fig. 10

an illustration of an eccentric wheel to illustrate a second embodiment of the invention,

Fig. 11

10 shows a cross section through the eccentric wheel along the section line XI-XI in FIG. 10,

Fig. 12

a top view of a radiator plate, and

Fig. 13

a solid block with a thin bore to illustrate a third embodiment of the invention.

The inventive casting process for the production of metallic castings is particularly characterized by this characterized that the cast material in the mold controlled cooling or that a cooling system for controlled cooling of the cast material is provided. With the The term "controlled cooling" means that - in the Difference to passive solidification or cooling down - heat is actively removed from the casting material or the casting mold and controls the amount of heat extracted can be influenced.

In the exemplary embodiments described below is used as castings, for example, cast iron and special a cast iron alloy is used. A first embodiment of the invention relates on the manufacture of engine housings for Large diesel engines, such as those used in shipbuilding be used. Such engine cases that are typically extremely complex, that means many cavities and recesses as well as a large one Have number of partitions of different thickness, are usually poured into sand molds that according to the desired shape of the one to be manufactured Castings, possibly taking into account one Machining allowance to be modeled.

Fig. 1 shows a partially schematic representation a motor housing 1 in a mold pit 2, which as Permanent form, i.e. designed for multiple use. The engine housing 1 includes a crank chamber 11 and a cylinder space 12 in which two cylinders 122 are recognizable. The motor housing usually comprises 1 several, for example ten or twelve cylinders 122, which are arranged in pairs in a row. On the further details of that shown in Fig. 1 Motor housing 1 is not discussed here because on the one hand, this is not essential for understanding the Invention and the other are well known.

To manufacture the motor housing 1 is first in the shape of the motor housing 1 in a known manner the mold pit 2, for example made of cement sand consists of several sand cores. Such a Sand core is made from a binder Quartz sand or another sand-like mineral z. B. by chemical or thermal curing created. The individual sand cores that normally only are designed for single use, are in the Form pit assembled or combined such that the cavities between them in their entirety essentially the shape of the casting to be made for the motor housing 1 correspond. According to the 1 shows essentially all cavities and recesses in the motor housing 1 to be produced and the space between the motor housing 1 and the Floor 21 or the inner wall 22 of the mold pit 2 through appropriately shaped sand cores. Because of better clarity is in Fig. 1 on a explicit representation of the sand cores waived and therefore the motor housing 1 shown by the The totality of voids between and in the sand cores is formed.

After the sand mold is created this way, it will liquid castings, usually a cast iron alloy, poured into the sand mold and flows into the cavities, where it solidifies and cools, causing the depicted Motor housing 1 is created.

According to the invention, a cooling system is controlled Cooling of the cast material is provided. In the case of FIG. 1 The illustrated embodiment includes the cooling system several pipe systems that include a crankcase cooler 3 (see Fig. 2 and Fig. 3) and a floor cooler 4 (see Fig. 4) form. A pipe becomes fluid through the pipe systems The heat transfer medium moves the casting material or the casting mold Deprives heat. Air is used as the heat transfer medium because this medium is easy to use, harmless, inexpensive and efficient, even with the usual high temperatures of the cast material. The air can for example by means of a fan or Blower can be moved through the pipe systems. The one The amount of heat extracted from the casting material can be Flow rate of air in relation to time in simple Way through valves, throttle valves or other Control dosing devices. For example, by increasing the flow velocity of the air or by increasing the pressure of the air fed in Increase cooling capacity of the cooling system. In practice it has it has proven itself to supply compressed air of up to a few bar Feed pipe systems. The control of the in the individual pipe systems flowing air volumes can both input and output of the pipe systems respectively. The control takes place for practical reasons but preferably on the output side.

In the first embodiment, two are in essential independent pipe systems provided, namely the crankcase cooler 3 and the floor cooler 4. This is it is possible to cast the casting material in different spatial Extract areas in a targeted and controlled manner, whereby the amounts of heat extracted from the various areas in the are essentially independently controllable. By this local heat extraction it is possible that Temperature profile, i.e. the temperature distribution in the Casting, controlled influence. Through the Placement and the shape of the pipe system or the course the pipes of the pipe system in the mold can be the spatial areas in which the casting material is Pipe systems pretend heat is withdrawn. The explicit The design and placement of the pipe systems is based depending on the geometry of the casting and the concrete Application.

In the first embodiment, the Crankcase cooler 3, the cast material in the border area between the crank chamber 11 and the cylinder chamber 12, that is where there is one due to the geometry of the casting Heat build-up can occur, locally extracting heat. The Floor cooler 4 is used to extract heat from the floor area the engine housing 1.

Furthermore, temperature sensors 5a, 5b, 5c, for example thermocouples cast in the cast material, provided with which show the local temperature of the casting different places is continuously recorded. In the first embodiment, there is a first Temperature sensor 5a in the bottom area, a second Temperature sensor 5b in the center of the border area between Cylinder 12 and crank chamber 11 and a third Temperature sensor 5c in the flange area of the motor housing 1 provided. From the measured values of the three The current temperature sensors 5a, 5b, 5c Determine the temperature profile in the cast material. The Temperature sensors 5a, 5b, 5c transmit their measured values for example to a regulation 6, by means of which the Air volumes in the pipe systems can be controlled. By means of the Regulation 6 sets the flow rate of air in the individual pipe systems, for example via a corresponding control of not shown Throttle devices controlled such that, depending on current temperature profile in the Giessling, the one or other spatial area of the casting a larger one or less heat is withdrawn per time. It comes for example in the area of the second temperature sensor 5b to a heat accumulation, recognizable by a large one Difference between that of the second temperature sensor 5b and the third temperature sensor 5c measured Temperatures, so the regulation 6 Cooling capacity of the crankcase cooler 3 by enlarging the flow rate in air increases so that this approach the two temperatures.

The pipe system forming the crankcase cooler 3 is in 2 is shown in a side view and in Fig. 3rd in a view from the direction III-III in Fig. 2. The crankcase cooler is preferably 3rd in one piece from a tube, for example a steel tube manufactured. The crankcase cooler 3 has a supply Leg 31, which is in a curved, the shape of an almost closed S having part 33 passes. The other End of the S-shaped part 33 goes into a laxative Leg 32 over, which is substantially parallel to that feeding leg 31 runs. The S-shaped part 33 of the crankcase cooler is arranged in the mold, that it is provided with the reference number 30 in FIG Area contacted, which is essentially the limit between the crank chamber 11 and the cylinder chamber 12 forms. According to the shape of this surface 30 are two elbows of the S-shaped part 33 relative inclined towards each other so that they are in the side view 2 form a V. The two bow pieces of the Part 33 are curved so that they the wall of the Follow cylinder 122. Are preferably on the S-shaped Part 33 several heat-conducting plates 34, for example made of graphite, with which the Crankcase cooler 3 rests on surface 30. Thereby is a homogeneous and good heat transfer from guaranteed the cast material in the crankcase cooler 3. It it goes without saying that there is one for each pair of cylinders Crankcase cooler 3 is provided. The feeding and laxative legs 31, 32 each run according to the Representation in Fig. 1 of the surface 30 through the Crank chamber 11 upwards. The feeding legs 31 are either individually or through a common central Line into which they flow, with a Air supply means, for example a fan or a blower. The laxative legs 32 are used for better control and monitoring preferably each individually out of the mold.

The pipe system forming the floor cooler 4 is shown in FIG. 4 shown. The floor cooler 4 is in the bottom of the molding pit 2 arranged and comprises a main line 41, which essentially over the entire width of the Motor housing 1 extends. From the main line 41 branches four each essentially U-shaped tubes 42 from each of which only one leg with the Main feed line 41 is connected. Through these legs the air flows, as indicated by the arrows in FIG. 4, into the U-shaped tubes. The other legs of the U-shaped tubes 42 each lead to an outlet 43 for the exhaust air. For better control and monitoring the outputs 43 are individually led out of the mold. Are between the legs of the U-shaped tubes 42 several steel plates 44 arranged, for example welded in to ensure even cooling of the To achieve bottom area of the motor housing 1. to faster heat transfer between the cast material and the floor cooler 4 can be a transmission medium, e.g. B. Graphite plates 45 may be provided. The graphite plates 45 are in between the steel plates 44 and the cast material or between the sand cores of the casting mold closest to the ground arranged. Furthermore, a feed line 7 (Fig. 1) provided by which the cold air to the level of Main line 41 is guided and fed into this becomes. The tubes of the floor cooler 4 can, for example be made of steel.

In the first embodiment of the invention, it is the primary goals, the cooling time of the engine case in the mold 1 and thus the required production time to shorten significantly, and the residual stresses in the Reduce the casting to the extent that subsequent stress relief annealing can be dispensed with can.

The first goal is achieved through active heat extraction from the cast material by means of the pipe systems directed air reached. This is the heat dissipated much faster than, for example, the allow passive cooling. Practice shows that the cooling time by means of the active controlled cooling, So the time that the motor housing 1 in the mold needed to reach its unpacking temperature, in Compared to passive cooling to less than one Can shorten thirds. This means under economic progress.

From an economic point of view, it is also advantageous that the emerging from the pipe systems heated air used to dry other molds can be so that the contained in the heated air Energy doesn't go unused.

The second goal can be achieved by using the Controlled cooling of the Temperature profile in the area of the temperature sensors 5a and 5b to the temperature profile in the area of Temperature sensor 5c is adjusted. This means, that by regulating the flow rates of air in the Crankcase cooler 3 and in the floor cooler 4 Temperature gradient over the cast material is minimized. By controlled and local heat extraction from the different areas of the cast material, it is possible the cast material is very homogeneous, i.e. with very little internal To cool down temperature differences. Where the Heat builds up, for example in the area of Temperature sensor 5b, the cooling capacity of the corresponding pipe system (crankcase cooler 3) increases that the local heat extraction Temperature to that in the area of the temperature sensor 5c aligned. This homogeneous cooling allows drastically reduce the residual stress in the casting. It is also possible in the area of the temperature sensor 5b to cool so much that here a lower one locally Temperature prevails than in the area of the temperature sensor 5c and the temperature sensor 5a. In principle, it is possible in the area of the temperature sensor 5b To generate compressive stresses.

Thus, in the first embodiment, the Invention of both the spatial cooling process (Temperature profile) as well as the temporal cooling process Influence (cooling rate) in a controlled manner. this means a significant expansion of the casting technology Opportunities because of the spatial and temporal Cooling process of the cast material under metallurgical Aspects, depending on the geometry and desired mechanical Properties of the cast part to be produced, can be optimized is.

Various figures are shown schematically in FIGS. 5-9 Variants for heat transfer between the cast material 10 and the heat transfer air, which is in a line 8 one of the pipe systems moved, shown. The Air is symbolized by an arrow shown. In the simplest case (see Fig. 5) runs the line 8 inside a sand core 9, so that the Sand is the transmission medium, which the Pipe system thermally coupled to the cast material. Is too it is possible (see Fig. 6, Fig. 7 and Fig. 9) as Transmission medium a better heat-conducting material, preferably graphite 20 to use. 6 shown variant, the line 8 is completely of the Surrounded by graphite 20. This can be achieved, for example be by the line 8 at least over a part their length is molded into a graphite body. at the variant shown in Fig. 7 is between the line 8 and the casting 10 also graphite 20 as Transmission medium, but the line 8 borders on it the casting 10 side facing away from a sand core 9. For realization this variant, it is also possible, as in Fig. 9 in Cross section shown, the line 8 on the one hand partially embedded in a sand core 9 and on the other hand, in physical contact with the graphite 20, for example, to bring a graphite plate. Preferably, for better heat transfer, as shown in Fig. 9, the space between the Graphite 20, the line 8 and the sand core 9 with one malleable good heat-conducting medium 22 filled. Suitable for this is, for example, graphite powder, Graphite granules, or graphite powder or granules, the with a good heat-conducting resin, e.g. B. furan binders, is mixed. In the variant shown in Fig. 8 the line 8 is surrounded by an iron body 21, poured into the iron body 21, for example. Is between the iron body 21 and the cast material 10 again graphite 20 is provided.

A second embodiment of the invention relates focus on the production of large eccentric wheels that for example in large presses such as automobile presses be used. During the first embodiment primarily demonstrated how by means of the invention the cooling process in the cast material is controllable the second embodiment primarily as the invention advantageous for controlling the solidification process in Cast material can be used.

In Fig. 10, half is a known one Eccentric wheels 50 shown, the outer ring gear 51 has. 11 shows for better understanding a cross section through the eccentric wheel 50 along the Section line XI-XI in Fig. 10. Also such eccentric wheels 50 are usually modeled accordingly Poured sand molds. For the sake of a better overview is in Figures 10 and 11 on the representation of Sand mold has been dispensed with.

Such eccentric wheels 50 usually have to Sprocket 51 very good mechanical properties, in particular have a very high hardness, around which To withstand the requirements in operation in the long term. there the structure in the area of the ring gear 51 should also be free of cementite excretions. These high Structural requirements are familiar with Casting process not feasible, so that the structure of the Castings after removal from the mold using complex thermal aftertreatment (e.g. normalization annealing with cooling in air and then Stress relieving) has to be formed in order to B. the to achieve the desired hardness. A great disadvantage due to the processing costs it is that the Microstructure of the entire eccentric wheel 50 due to the thermal Post-treatment is reshaped and not just the areas which should have the great hardness.

Controlled cooling according to the invention allows now in the area that should be extremely hard, namely in the area of the ring gear 51, the solidification accelerate through targeted heat extraction in such a way that the ring gear 51 has a very fine structure with small has eutectic cells and completely pearlitic is. Due to the controlled cooling, the Desired hardness on the ring gear 51 without thermal Aftertreatment can be realized, with the rest of the Eccentric wheel 50 remains essentially unaffected.

In the second embodiment, this includes Cooling system multiple cooler plates 60 along the The circumference of the eccentric wheel 50 is arranged. To the better heat transfer is between each cooler plate 60 and the eccentric wheel 50 each have a good thermal conductivity Medium, for example a graphite element 70, where a surface of the graphite elements 70 to each Eccentric wheel curvature is adjusted.

Such a cooling plate 60 is in one in FIG Supervision shown. The cooler plate 60 has an in essentially cuboid shape and has Pipe system that in this embodiment as a one-piece pipeline 61 is configured. The Pipeline 61 leads from an inlet 62 for the Cold air through the interior of the cuboid cooler plate 60 to an outlet 63. Inside the radiator plate 60 The pipeline 61 initially runs parallel to the circumference following the radiator plate 60 then curves in the direction the center of the cooler plate 60 and leads in reverse Direction back to outlet 63. Die The direction of air flow is shown in FIGS. 11 and 12 indicated by the arrows. The cooler plate 60 can for example from a solid steel or iron cuboid exist in which the pipe 61 is cast.

The various cooler plates 60 (see FIG. 10) can individually, in groups or together, each by the Inlet 62 are supplied with air. By controlling the Flow rate of air flowing through the air per time Cooler plates 60 flows, which can be the in the cast Area of the ring gear 51 specifically extracted amount of heat Taxes. This allows the solidification of the cast material accelerate locally in a controlled manner. By appropriate placement of the cooler plates 60 or The area of the Giesslings specify in which through targeted and controlled heat extraction accelerates solidification shall be.

The invention thus also enables the spatial and temporal solidification process in the cast material controlled influence. This also results an expansion of the casting possibilities because a targeted, local influencing of the Solidification-forming structure can be realized.

A third embodiment of the invention relates focus on the production of castings, the massive, have thick areas or blocks in which comparatively thin holes are provided. Fig. 13 shows a section of such a casting, the a solid block 80 (shown hatched) in which a comparatively thin bore 81 is provided. Also the one in FIG. 13 in a detail shown casting is not, for example, in one cast sand mold shown. To realize the Thin bore 81, a sand core 90 is provided, which keeps liquid casting material away from the space of the mold where the casting should later have the thin bore 81. It is a known problem with conventional ones Casting process that there is such thin Bores 81 comes to considerable heat build-up. This often cause the sand of the sand core 90 heats up so much that the penetration temperature of the Sands is exceeded and cast material in the sand core 90 penetrates. The resulting sand-cast iron mixture must be laborious after the casting has been removed from the mold be chiseled out, which is a very time consuming and is damaging work for the staff.

The controlled cooling according to the invention allows also solve this problem. To do this, use a Pipe system, which runs inside the sand core 90, and through which air is moved as a heat carrier, targeted to the spatial area of the casting Extracted heat that contains the thin bore 81. Consequently the solidification and / or the Cooling of the cast material in the area of the thin bore 81 accelerate and through a corresponding regulation of Also control the flow rate of air. On the other hand, can heating the sand core 90 over its Penetration temperature can be avoided efficiently.

In the solid block shown in FIG. 13, this is Pipe system for cooling as a double U-shaped pipe 91 designed. The air flowing through the pipe 91 is indicated by the arrows. Such a double U-shaped Tube 91 can be manufactured by a first straight tube is bent into a U and then the round end of the U towards the open end of the U is bent.

Even if the exemplary embodiments described here Sand casting methods refer to, that is the invention of course, not limited to such examples. she is also for mold casting processes or molds (metallic, mostly made of cast iron Casting molds), suitable or for such casting processes, in which a part of the casting through chill molds and a other part is shaped by a sand mold. In the Using molds it is possible, for example, the pipe systems for the heat transfer medium in the wall of the Provide mold. For example, the pipe systems be poured into the mold.

The casting method according to the invention thus allows through the controlled cooling the spatial and temporal solidification and / or cooling process in the To influence the castings in a controlled manner. Let her through yourself Cooling times, especially for large-scale castings reduce significantly. Metallic castings can also be used very good quality without being made for it elaborate thermal post-processing, such as for example stress relief annealing to reduce Internal stresses or normalization annealing Structural transformation is necessary. This means one considerable time and cost savings.

The placement and the spatial course of the cooling system depends on the geometry of the manufactured Giesslings and according to the specific application, the means after the desired metallurgical effects. Based on these criteria, the spatial Specified areas of the cast material to which targeted and controlled heat is to be extracted.

Claims (8)

1. Casting method for the manufacture of metallic cast parts from a casting material in which the casting material is introduced in the liquid state into a mould, in particular into a sand mould, and the casting material solidifies and cools down in the mould, with the casting material being cooled in the mould by a cooling system (3, 4; 60; 91) in a controlled manner, characterised in that at least one local spatial region of the cast part is specified in dependence on the geometry of the cast part and the desired metallurgical effects in which heat is removed intentionally and in a controlled manner from the casting material in the mould, in that the cooling system is matched with respect to its placement and its form for the controlled removal of heat to this local spatial region and in that the controlled removal of heat out of this local spatial region is carried out only by means of flowing air.
2. Casting method in accordance with claim 1, in which heat is removed intentionally and in a controlled manner from the casting material in the mould in a plurality of predeterminable spatial regions, with the amounts of heat removed from the different spatial regions being regulatable substantially independently of one another.
3. Casting method in accordance with one of the preceding claims, with the respective local temperature being continually measured by means of temperature sensors (5a, 5b, 5c) at different points in the casting material and with the temperature profile determinable therefrom being used for the control of the cooling.
4. Casting method in accordance with claim 3, with the temperature gradient across the casting material being minimised.
5. Casting method in accordance with one of the preceding claims, with the solidification of the casting material being controlled by the intentional removal of heat.
6. Casting method in accordance with one of the preceding claims in which the cooling system (3, 4; 60; 91) comprises at least one tube system (3, 4; 61; 91) for the flowing air and in which the tube system (3, 4; 61; 91) is thermally coupled to the casting material (10).
7. Casting method in accordance with claim 6 in which the transfer medium (20; 21; 22) contains graphite.
8. Casting method in accordance with one of the preceding claims in which furthermore a regulating system (5) is provided which controls the amounts of heat removed in such a manner that the temperature gradient across the casting material is minimal.

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