EP0872295A1 - Casting mould and method for the production of hollow castings and hollow castings - Google Patents

Abstract

A mould for production of hollow metal castings is provided with an inlet (4) for introduction of a casting material (6) into a cavity (5) bounded by forming surfaces (7, 8, 9). The mould (1) comprises a steel mould (3) and a sand mould (2), with the steel mould providing the forming surface (9) and the sand mould providing the rest (7, 8) of the forming surfaces. Also claimed is a hollow casting with two zones with different wall thicknesses.

Description

The invention relates to a casting mold and a method for the manufacture of hollow metal castings according to the preamble of the respective independent claim and one using this mold or this Process produced hollow casting with two areas different wall thickness. In particular, the Invention a mold and a method for manufacturing of cylinder liners for reciprocating internal combustion engines, especially for large diesel engines.

In reciprocating internal combustion engines, especially in Large diesel engines, such as those used in shipbuilding are used, the cylinder liners are subject to Operating condition of an extremely strong mechanical and thermal load. Especially in the explosion area of the Fuel mixture is high in the cylinder liner Pressures and high temperatures. Therefore must the cylinder liner especially in the explosion area have a high strength to withstand the explosion of the fuel mixture to withstand.

To the strength of the cylinder liners in the area to increase, in which the explosion of the Fuel mixture takes place, the Cylinder liners are typically used in these areas thick-walled. That means one The cylinder liner has two main areas with significantly different wall thickness: one first area in which the wall thickness is greater and which according to the usual nomenclature as Collar area is referred to as well as a second Area in which the wall thickness is smaller and which is called the shirt area.

Cylinder liners for internal combustion engines are often used by means of casting processes from cast iron and especially from Made of gray cast iron alloys. In addition to the chemical Composition of the alloy used as casting compound become the physical and metallurgical Properties of the cylinder liner, such as Structure, strength, elongation, tribological Properties, also from the solidification process of the Casting material significantly influenced. That is why used mold or the carried out Casting process of great importance for the Properties of the cylinder liner.

For the manufacture of cylinder liners are from State of the art two different types of Casting process known. In the sand casting process the liquid casting compound is poured into a sand mold, the beforehand according to the desired shape of the castings to be produced, if necessary under Consideration of a machining allowance, modeled has been. Such a sand mold is made with one Binder quartz sand or another, sand-like mineral z. B. by chemical or thermal curing created and is usually only designed for single use. Disadvantageous cylinder liners produced in this way is, however, that, for example, in terms of their structure, their strength and their stretch less and less The requirements are sufficient, as they are in modern Reciprocating internal combustion engines, especially with large ones Performance. This is mainly due to it attributed that the solidification process of the Casting compound, especially the setting time, in the Sand form not optimal under metallurgical aspects is.

In the second type of casting process, the so-called Chill casting process, one is mostly used Cast iron mold (mold) into which the liquid casting compound is filled. The outer shape the castings get here by a metallic Form in which the casting compound solidifies. Such molds can usually be used several times. At Chill casting is subject to the outer shape of the produced castings, however, relatively strong geometrical restrictions because the mold after the Solidify or after the casting has cooled down must be removable. Because of this constraint can geometric details in the outer shape of the Giesslings usually do not with permanent mold casting processes be formed with reasonable effort. So you have to in the manufacture of e.g. B. of cylinder liners Giessling with relatively large processing allowances to create the desired exterior To be able to realize the shape of the cylinder liner, that is called the castling gives way to its outer Usually shape quite strongly from the desired one End product. This is time-consuming and costly Postprocessing in which large amounts of material e.g. B. can be removed by machining processes have to. Such large processing allowances require one significantly increased need for casting compound and are also therefore not in economic terms desirable.

Especially in the production of very large ones Castings such as B. cylinder liners for modern powerful large motors also result from the Weight of the mold problems. One with casting compound filled mold has a weight in the Range of several tens of tons. Many foundries do not have enough strong lifting devices to to move such masses, e.g. B. a filled mold to move to another place to cool down, or to pull the mold off the casting. It would be extensive and very costly Conversion work required to be strong enough Install lifting devices.

Based on this state of the art, it is one Object of the invention, a casting mold and a method for the production of hollow metal castings to provide the most optimal spatial and temporal solidification in the Allow casting compound and at the same time with relative small processing allowances. In particular is it is an object of the invention, a mold and a To provide methods that are relatively low Machining allowances the manufacture of such Cylinder liners for reciprocating piston internal combustion engines, especially for large diesel engines, enable the with regard to their resilience (e.g. strength, Elongation) also meet the requirements in modern powerful machines are sufficient.

These tasks in apparatus and procedurally resolved objects of Invention are characterized by the characteristics of each characterized independent claim. The Casting mold according to the invention for producing metallic hollow castings from a casting compound, especially for the manufacture of cylinder liners for Reciprocating internal combustion engines, especially for Large diesel engines, has an inlet for the introduction of the Pouring compound into a casting room, which through Forming surfaces are limited and the casting compound records. The casting mold according to the invention comprises a Mold and a sand mold, the mold being a first Has shaping surface, and the sand mold the rest decisive shaping surfaces.

Surprisingly, it turns out that the Casting mold according to the invention and the inventive Procedure the respective advantages of both Sand casting process as well as the permanent mold casting process without the disadvantages mentioned above in Purchase must be made. By the inventive Combination of the mold with the sand mold can - how explained in more detail below - the spatial and solidification over time in the casting compound optimize that the mechanical strength of the Hollow castings (e.g. its strength and hardness) is significantly larger than that of Giesslingen, which for example with conventional sand casting processes or sand molds are produced. At the same time enables the sand mold of the casting mold according to the invention, or their use in the inventive Process, high flexibility with regard to the exterior Shape of the area of the shape that it forms Hollow castings, so that only comparatively small Machining allowances are required.

The mold is preferably the one according to the invention Cast mold designed in one piece because of this thermal damage to the hollow casting, such as they at the interface between two butts Mold parts can occur, have them avoided.

The mold preferably has lines for a fluid Medium, especially air, for the removal and / or supply of Heat up. This measure is advantageous because the Mold before introducing the liquid casting compound into simple way, namely z. B. by warm air through the Blown lines can be preheated. In addition, the hot mold can be removed after removing the Hollow castings easily and quickly, e.g. B. using cold air, can be cooled and stands for again after a short time a new casting process is available. It also exists advantageous possibility during and / or after Introduce the casting compound to withdraw heat from the mold.

In a preferred embodiment, the sand mold comprises a sand core and a sand coat, the casting room of the sand core on the one hand and the sand coat and the On the other hand, mold is limited.

The mold is preferably a vessel that is open on one side with an inner wall and a bottom, the inner wall and at least part of the floor form the first shaping surface. Through this measure the largest possible contact area between the Chill mold and the casting compound, whereby the Heat transfer between the casting compound and the mold improved, especially accelerated.

It is also advantageous if the bottom of the Mold element has a recess and the Sand core extends into this recess.

This allows the sand core to be easily removed center with respect to the sand shell and the mold, whereby the radial symmetry of the hollow casting is guaranteed.

Especially for the production of cylinder liners it is advantageous if the mold is designed in this way is that the distance between the sand core and the inner wall of the mold is larger than the distance between the sand core and the sandcoat. This will the thick-walled area of the hollow casting, that is Area corresponding to the collar area of the cylinder liner corresponds, molded in the mold. This is special favorable for the solidification process of the hollow casting because the thick-walled area (collar area) through the Chill mold at least as fast, but also faster, can freeze like the thin-walled Area (shirt area) that is shaped by the sand mold.

• die erste Formgebungsfläche bildet etwa die Hälfte derjenigen Flächen der Giessform, welche den Giessraum in dem Bereich begrenzen, der von der Kokille umgeben ist. Hieraus resultiert eine grosse Kontaktfläche, durch welche die Wärme aus der Giessmasse in die Kokille fliessen kann.
• das für die Kühlung des Hohlgiesslings wesentliche Materialvolumen der Kokille ist mindestens doppelt so gross ist wie das Volumen des von der Kokille umgebenen Bereichs des Giessraums. Somit ist gewährleistet, dass die Wärmekapazität der Kokille ausreichend ist, um eine rasche Erstarrung im Kragenbereich zu ermöglichen.
• die Wanddicke der Kokille beträgt weniger als das 1.5-fache, insbesondere etwa das 0.9-fache, des Abstands zwischen dem Sandkern und der inneren Wandung der Kokille.

Above all with a view to the optimal spatial and temporal solidification course, it is advantageous to adapt the design of the mold to that area of the casting mold which is surrounded by the mold. For the manufacture of cylinder liners in particular, this means that the dimensions of the collar area of the hollow casting are taken into account when designing the mold. The following measures are therefore preferred:

• the first shaping surface forms approximately half of those surfaces of the casting mold which delimit the casting space in the area which is surrounded by the mold. This results in a large contact area through which the heat can flow from the casting compound into the mold.
• the material volume of the mold which is essential for cooling the hollow casting is at least twice as large as the volume of the area of the casting space which is surrounded by the mold. This ensures that the heat capacity of the mold is sufficient to allow rapid solidification in the collar area.
• the wall thickness of the mold is less than 1.5 times, in particular approximately 0.9 times, the distance between the sand core and the inner wall of the mold.

The method according to the invention is used to manufacture metallic hollow castings, in particular Cylinder liners for reciprocating piston internal combustion engines, especially for large diesel engines, whereby the hollow castings have a first and a second region and the The wall thickness of the hollow casting is larger in the first area is as in the second area. In the inventive The process is a casting compound in a mold introduced and solidifies there. According to the invention the outer shape of the hollow casting in the first area by a mold and in the second area by a Shaped sand mold.

• wenn zum Formen der äusseren Gestalt des Hohlgiesslings im ersten Bereich eine einstückige Kokille verwendet wird;
• wenn die Kokille vor dem Einbringen der Giessmasse durch ein fluides Medium, insbesondere Luft, erwärmt wird;
• wenn die Kokille während und/oder nach dem Einbringen der Giessmasse durch einen fluides Medium, insbesondere Luft, gekühlt wird.

For reasons already mentioned above in connection with the casting mold according to the invention, it is also advantageous for the method according to the invention to

• if a one-piece mold is used to form the outer shape of the hollow casting in the first region;
• if the mold is heated by a fluid medium, in particular air, before the casting compound is introduced;
• if the mold is cooled by a fluid medium, in particular air, during and / or after the casting compound has been introduced.

The mold according to the invention or the Methods according to the invention are particularly suitable for the production of cylinder liners for a Reciprocating internal combustion engine, especially for one Large diesel engine, with two areas different Wall thickness.

The mold according to the invention is particularly suitable for Suitable for carrying out the method according to the invention.

Other advantageous measures and preferred Process configurations result from the dependent Claims.

Fig. 1

einen Schnitt durch ein Ausführungsbeispiel der erfindungsgemässen Giessform im gefüllten Zustand,

Fig.2

einen Schnitt durch eine Variante für die Kokille des Ausführungsbeispiels aus Fig. 1, und

Fig. 3

eine schematische Schnittdarstellung eines Teils einer Zylinderlaufbuchse und eines Teils einer Kokille.

In the following, the invention is explained in more detail both with regard to the procedural and also with regard to the apparatus aspects with reference to the drawing. The schematic, not to scale, drawing shows:

Fig. 1

3 shows a section through an exemplary embodiment of the casting mold according to the invention in the filled state,

Fig. 2

a section through a variant for the mold of the embodiment of Fig. 1, and

Fig. 3

is a schematic sectional view of part of a cylinder liner and part of a mold.

In the drawing, the same or in terms of function equivalent parts with the same reference numerals Mistake.

The following explanations of the invention using a Embodiment of the mold according to the invention for Manufacture of metallic hollow castings from one Casting compounds serve in the same way as Description of an embodiment of the inventive method for producing metallic hollow castings, the first and one have second area, the wall thickness of the Hollow castings in the first area is larger than in second area.

The following explanations also apply exemplary character only on the production of Cylinder liners for reciprocating piston internal combustion engines, especially for large diesel engines. However, they apply analogously also for the production of other metallic Hollow castings. With the term "hollow castings" are such casting body meant that next to their outer Boundary surface at least one boundary surface have, which faces the inside of the body, so e.g. B. hollow cylindrical body, bushings in general, or tubular structures.

It is common today, especially for large diesel engines to use such cylinder liners, the first Area, the so-called collar area and a second Have area, the so-called shirt area, where the average wall thickness of the cylinder liner in Collar area is significantly larger than in the shirt area, for example at least twice as large. Of the Collar area is the one in the operating state explosion of the fuel mixture of the engine takes place, which is the highest pressures and Exposed to temperatures and thus the highest stress is. To withstand this burden, is the Collar area usually with a larger one Wall thickness designed.

Fig. 1 shows a preferred in a sectional view Embodiment of the casting mold according to the invention, which is generally provided with the reference number 1. The casting mold 1 has an inlet 4 for introducing one Pouring compound 6 into a casting chamber 5. The casting chamber 5 is limited by shaping surfaces 7, 8, 9. With the The term "shaping surfaces" becomes physical existing areas designated that an essential Influence the shape of the hollow casting, the means the total of the shaping surfaces is 7,8,9 decisive for the shape of the hollow casting, it forms so him. The shaping surfaces are essentially correct 7,8,9 with the contact surfaces between casting compound 6 and Mold 1 match.

Fig. 1 shows the mold 1 in the filled state, i.e. the casting compound 6 is in the casting chamber 5 and fills this one out. 1 for better understanding Casting compound 6 in two parts with different hatching shown. The larger one, with the reference number 6a provided part indicates the finished Cylinder liner, i.e. the shape of the end product. Of the smaller part with the reference number 6b indicates the machining allowance. Of course this is two-part representation of the casting compound 6 symbolically understand.

According to the invention, the casting mold 1 comprises a mold 3 and a sand mold 2, the mold 3 being a first Has shaping surface 9 and the sand mold 2 the other decisive shaping surfaces 7, 8.

In the embodiment shown in Fig. 1 is the Mold 3 is a one-piece, open-sided vessel with an inner wall 31 and a bottom 32 (see also Fig. 2). The inner wall 31 forms together with one Part 32a of the bottom 32, the first shaping surface 9. Im Bottom 32 of the mold 3 is a recess 322 (see Fig. 2) provided, the function of which later is explained. The mold also has 3 lines 33 for a fluid medium, preferably air. This Lines 33 can channels inside the mold wall be or pipelines that run into the interior of the Mold wall are poured. Through these lines 33 air can be blown to heat the mold 3 feed or withdraw. Furthermore, the mold 3 is on provided on its outer wall with carrying devices 34 to which it can be raised. The mold 3 is, for. B. made in a manner known per se from cast iron.

The sand mold 2 of the shown in Fig. 1 Embodiment includes a sand core 21 as well a sand coat 22. The sand core 21 extends to into the recess 322 in the bottom 32 of the mold 3. Seine The outer surface forms the shaping surface 7. The Sand coat 22 is essentially in the form of a Hollow cylinder or a hollow truncated cone on and surrounds the sand core 21 essentially concentrically. The the sand core 21 facing boundary surface of the Sand jacket 22 forms the shaping surface 8. Depending on the outer shape of the hollow casting to be produced can the sand coat 22 be in one piece or - as in Fig. 1 shown - from several molded boxes 22a, 22b, 22c be composed. The manufacture of the 22 sand mold can be done in a manner analogous to that of conventional sand casting process well known is and therefore does not require any further explanation. Of the Sand coat 22 is sealing but detachable with the mold 3 connected. Known sealants can be used Escape of the liquid casting compound 6 between the mold 3 and prevent the sand coat 22.

The casting space 5 is thus on the one hand from the sand core 21 or the shaping surface 7 and on the other hand of the sand coat 22 and the mold 3 and the associated shaping surfaces 8 and 9, that is The outer shape of the hollow casting is essentially through the first shaping surface 9 of the mold 3 and the Forming surface 8 of the sand shell 22 determined.

In the preferred shown in Fig. 1 The exemplary embodiment is in the recess 322 in the base 32 the mold 3 is fitted with a further sand element 10, which receives one end of the sand core 21 flush. Here is the sand element 10, which can be produced in the same way is shaped like conventional sand molds in such a way that it centers the sankers 21 with respect to the mold 3. This measure ensures the radial symmetry of the Hollow castings can be realized.

The outer shape of the hollow casting in the first area, that is, the area with the greater wall thickness has (collar area), the mold 3 shaped. Therefore, the one shown in Fig. 1 Casting mold 1 the distance between the sand core 21 and the inner wall 31 of the mold 3 larger than the distance between the sand core 21 and the sand coat 22. Furthermore is the embodiment of the mold 1 for designing rising cast, that is, the liquid Casting compound 6 is at the bottom of the mold 1 in the Foundry room 5 introduced. For this purpose, inlet 4 comprises an inlet duct 41, which is located approximately in the center of the Sand core 21 through this and along its longitudinal axis extends. The inlet channel 41 opens into a distributor 42, which is located in the sand element 10 in the recess 322 located. The distributor 42 connects the inlet duct 41 with the casting chamber 5, so that the liquid casting compound 6 through the inlet duct 41 and the distributor 42 to the reaches the lower end of the casting chamber 5. At the upper end (as shown in Fig. 1) of the casting room 5 Overflow container 11 is provided, which also with Fill the casting compound 6 when the casting chamber 5 is filled. The overflow container 11 also serve as Expansion tank from which the casting compound 6 in the Casting chamber 5 can flow back when the volume of the Casting compound 6 in the casting chamber 5 decreases during solidification.

It is understood that the mold according to the invention or the method according to the invention also for falling Cast can be designed, d. H. the casting room 5 then from above (as shown in Fig. 1) with the Casting compound 6 filled. This can be done using, for example a ring feeder, which is on the upper end of the Casting mold 1 is placed.

Fig. 2 shows a section through a variant for the Mold 3. Most of the reference numerals in Fig. 2 are already explained earlier. These explanations are to be clarified again by Fig. 2. A Difference in the variant shown in Fig. 2 Mold 3 is that the inner wall 31 is not is smooth-walled, but a paragraph 311 having. This makes it possible to change the shape of the Hollow castings even more the desired shape of the Align end product and thus the necessary To further reduce post-processing. In the variant the mold 3 according to FIG. 2 are in the wall of the mold 3 two separate lines 331 and 332 for the fluid Medium provided for the removal and supply of heat. Each of lines 331 and 332 is as a pipeline designed, which is poured into the wall of the mold 3 and the mold 3 rotates twice in the circumferential direction. Extends from a first opening 331a or 332a the associated pipeline inside the Mold wall parallel to the circumference around the mold 3, then leads up in the wall, revolves around the Mold 3 in the circumferential direction and ends at a second Opening 331b or 332b. Through each of these lines 331 and 332 can move the fluid medium, preferably air in order to supply or to add heat to the mold revoke. So it is, for example, using warm air possible to preheat the mold 3 in a simple manner thermal damage on contact with the to avoid hot casting compound 6. It turned out to be proved favorable, the mold 3 before the introduction of the Casting compound 6 to a temperature of over 100 ° C. preheat. It is also possible through the Lines 331 and 332 blow cold air to z. B. the Chill mold 3 cool down more quickly after the hollow casting is separated from her. This allows the mold 3 provided faster for further casting processes will. It is also possible to the mold 3 during the Solidification or cooling of the casting compound 6 heat withdraw to z. B. the solidification in the first area To accelerate (collar area) of the hollow casting. In addition, the mold, for example after the Applying release agents and protective agents using warm air be heated to remove residual moisture.

In the following, the production of a Cylinder liner for a large diesel engine using the Casting mold 1 described. First of all, in itself known manner, the sand core 21 (Fig. 1), the sand element 10 and the sand coat 22 or the sand coat 22 forming mold boxes 22a, 22b, 22c corresponding to the modeled the desired shape of the hollow casting. Out the individual parts and the mold 3 is then the Casting mold 1 assembled, the sand core 21 adjusted or centered, and the sand coat 22 becomes firm connected to the mold 3, for. B. screwed. Here the connection point between the sand coat 22 and the mold 3 sealed by a sealant.

The mold 3 is z. B. by means of lines 33 blown warm air to over 100 ° C, for example preheated. Of course, preheating can also be done before Assemble the casting mold 1. Now the liquid casting compound 6, usually one Cast iron alloy, through the inlet duct 41 and the Distributor 42 introduced into the casting room 5.

The casting compound 6 solidifies in the casting chamber 5, causing the Hollow casting is created. The outer shape of the Hollow castings will be in the first area (Collar area) through the first shaping surface 9 of the Mold 3 shaped and in the second area (shirt area) through the sand coat 22 of the sand mold 2. After the Casting compound 6 is solidified, the sand mold 2 can together be lifted off the mold 3 with the hollow casting and deposited in another place to cool down. The mold 3 can thus be used again for one another pouring process can be prepared. After the Hollow casting in sand mold 2 has cooled sufficiently, it is removed from the mold and can now be reworked until the cylinder liner has its final shape.

The interaction of the mold 3 and the sand mold 2 is especially for the production of cylinder liners or of hollow castings with two areas clearly different wall thickness advantageous because of itself hereby a particularly favorable time and space Solidification course of the casting compound 6 can be achieved. in the first - thick-walled - area (collar area) the hollow casting due to the 2 much better heat-conducting mold 3 the heat withdrawn, so that here a large heat flow related to the contact area between the casting compound and the mold 3 prevails. As a result, the hollow casting solidifies in the Collar area very quickly. A short solidification time in the Collar area is under metallurgical aspects desirable because this creates a finer structure in the Hollow casting is created, d. H. a structure with small eutectic cells. This results in very good ones mechanical properties, such as high Strength and high elongation, especially in the collar area, where the cylinder liner is in the operating state is subject to the highest loads.

In the shirt area, i.e. where the wall thickness of the Hollow castings is smaller, a small heat flow is sufficient based on the contact area between casting compound 6 and Sand mold 2 out because of the solidification too extracting heat per contact area is smaller. In addition is the mechanical load on the cylinder liner in the Operating condition in the shirt area not as high as in Collar area, so that a short solidification time in the Shirt area is not as essential as in the collar area. Thus, the advantages of the Sand molding, especially the greater flexibility regarding the external shape of the hollow casting, be used. In addition, the weight of the Casting mold compared to a full mold, so that the Handling of the mold is simplified.

By combining the sand mold 2 with the mold 3 it is because of the different Thermal conductivity of the sand mold 2 and the mold 3 in particular also possible, the hollow casting in the first Area (collar area) to solidify faster bring as in the second area (shirt area). This kind spatial solidification is very advantageous because the Pouring compound 6 in the shirt area is still liquid when in the Collar area already solidifies, because thus can still pour liquid 6 from the shirt-in flow around the collar area to here solidification-related volume reductions in the casting compound balance. This will be a disadvantage Void formation in the collar area practically avoided what positive on the mechanical properties of the Cylinder liner in the collar area.

The one-piece design of the mold 3 is particularly preferred because this results in the heat flow the collar area into the mold 3 during solidification spatially very homogeneous, what is the structure of the educational structure positively influenced.

There is also in the described embodiment the possibility of the mold 3 during the solidification of the To withdraw heat in the collar area by e.g. B. Cold air is blown through the lines 33. This allows the temperature gradient to be Affect the mold wall and the solidification of the Accelerate hollow castings in the collar area.

It is also in view of a rapid solidification of the Hollow castings in the collar area advantageous if - how described above - the first shaping surface 9 a Part 32a of the bottom 32 of the mold 3 comprises. Through this Measure is the contact surface through which the heat can flow from the casting compound 6 into the mold 3, as large as possible, which also leads to a quick Solidification of the collar area contributes.

With regard to the best possible spatial and temporal solidification course and especially in With a view to rapid solidification in the collar area it is advantageous if, on the one hand, the first Shaping surface 9 about half of those surfaces the mold 1, which forms the casting chamber 5 in the Limit the area surrounded by the mold 3, the That is, the first shaping surface 9 is approximately half as much as large as the heat emitting surface of the Collar area. On the other hand, it is advantageous if that essential for the cooling of the hollow casting Material volume of the mold 3 at least twice as large is like the volume of that surrounded by the mold 3 Area of the casting room 5, that means for the Heat removal is essential material volume of the mold 3 at least twice the volume of the Collar area. The wall thickness of the mold 3 is preferably less than 1.5 times, in particular approximately 0.9 times the distance between the sand core 21 and the inner wall 31 of the mold 3. This distance is equal to the wall thickness of the hollow casting in Collar area.

These advantageous measures should be based on FIG. 3 be clarified again. Fig. 3 shows in a schematic sectional view of a part of rotationally symmetrical collar area of a Hollow castings (left) and the part of the mold 3, the the outer shape of the collar area shown shaped (right). The representation in FIG. 3 corresponds essentially to a section of the lower right corner of Fig. 1.

In Fig. 3, the wall thickness of the mold 3 with the Reference number DK denotes and that for cooling essential material volume of the mold 3 with the VK. With the term "for cooling essential material volume "are the Volume areas of the mold wall meant that immediately be limited by the shaping surface 9. For example, those shown in FIG. 1 Carrying devices 34 and 21 under the sand core arranged part on which the mold 3 is not to the material volume essential for cooling count.

The collar area shown in the left part of FIG. 3 of the hollow casting has a total volume that with VG is designated, as well as a wall thickness that with DG is designated. During the solidification of the casting compound 6 the heat can be dissipated through the surface OG of the Collar area are given off, the heat both by the left part of the surface OG in FIG the sand core 21 flows as well through the lower and right part of the upper floor into the mold 3. The the surface of the heat-emitting surface is the same as large as those surfaces of the mold 1 that the of limit the area of the casting space 5 surrounding the mold.

• die erste Formgebungsfläche 9, welche von der inneren Wandung 31 der Kokille 3 und dem Teil 32a des Bodens der Kokille 3 gebildet wird, etwa halb so gross ist wie die wärmeabgebende Oberfläche OG des Kragenbereichs. Hieraus resultiert eine möglichst grosse Kontaktfläche zwischen dem Kragenbereich und der gut wärmeleitenden Kokille 3.
• das Materialvolumen VK der Kokille mindestens doppelt so gross ist wie das Volumen VG des Kragenbereichs. Dadurch ist die Wärmekapazität der Kokille 3 ausreichend, um eine rasche Erstarrung des Kragenbereichs zu ermöglichen.
• die Wanddicke DK der Kokille 3 weniger als das 1.5-fache, insbesondere etwa das 0.9-fache, der Wandstärke DG des Kragenbereichs beträgt.

In the concrete example shown in FIG. 3, the aforementioned advantageous measures for optimizing the solidification process mean that

• the first shaping surface 9, which is formed by the inner wall 31 of the mold 3 and the part 32a of the bottom of the mold 3, is approximately half as large as the heat-emitting surface OG of the collar region. This results in the largest possible contact area between the collar area and the good heat-conducting mold 3.
• the material volume VK of the mold is at least twice as large as the volume VG of the collar area. As a result, the heat capacity of the mold 3 is sufficient to allow the collar area to rapidly solidify.
• the wall thickness DK of the mold 3 is less than 1.5 times, in particular approximately 0.9 times, the wall thickness DG of the collar area.

Practice also shows that it is advantageous to Arrange lines 33 in the wall of the mold that their distance DL from the inner wall 31 of the mold 3 is about a third of the wall thickness DK of the mold 3.

It can also be advantageous in the transition area between collar and shirt area cooling element 15 (see Fig. 1), for example metallic cooling plates, in the To provide mold 1 to the rapid solidification of the To promote the collar area.

With the mold according to the invention or the The method according to the invention can be Cylinder liners for reciprocating piston internal combustion engines, especially for large diesel engines, especially due to the optimized time and spatial solidification course of the casting compound 6, very much good mechanical properties, e.g. B. high strength and have high elongation, so that such Cylinder liners also for use in modern, powerful machines are suitable.

Claims (17)

Casting mold for the production of metallic Hollow castings from a casting compound (6), especially for the manufacture of cylinder liners for reciprocating internal combustion engines, especially for Large diesel engines, with an inlet (4) for Introducing the casting compound (6) into a casting chamber (5), which is limited by shaping surfaces (7,8,9) and absorbs the casting compound (6), thereby characterized that the mold (1) is a mold (3) and a sand mold (2), wherein the mold (3) has a first shaping surface (9), and the sand mold (2) the other decisive ones Shaping surfaces (7,8). Casting mold according to claim 1, wherein the mold (3) is designed in one piece. Casting mold according to one of the preceding claims, wherein the mold (3) lines (33; 331,332) for a fluid medium, in particular air, for exhaust and / or Has heat supply. Casting mold according to one of the preceding claims, which the sand mold (2) a sand core (21) and comprises a sand coat (22), the casting space (5) of the sand core (21) on the one hand and the Sand coat (22) and the mold (3) on the other hand is limited. Casting mold according to one of the preceding claims, which the mold (3) is a vessel open on one side with an inner wall (31) and a bottom (32) is, the inner wall (31) and at least one Part (32a) of the bottom (32) the first Form shaping surface (9). Casting mold according to claim 5, wherein the bottom (32) of the Mold (3) has a recess (322) and itself the sand core (21) into this recess (322) extends into it. Casting mold according to one of claims 5 or 6, wherein the distance between the sand core (21) and the inner wall (31) of the mold (3) is larger than the distance between the sand core (21) and the Sand coat (22). Casting mold according to one of claims 5-7, in which the first shaping surface (9) is approximately half of the surfaces of the casting mold (1) which forms limit the casting space (5) in the area from the mold (3) is surrounded. Casting mold according to one of claims 5-8, wherein the for the cooling of the hollow casting is essential Material volume (VK) of the mold (3) at least is twice as large as the volume (VG) of the Mold (3) surrounding area of the casting room (5). Casting mold according to one of claims 5-9, wherein the Wall thickness (DK) of the mold (3) less than 1.5 times, especially about 0.9 times the distance between the sand core (21) and the inner wall (31) the mold (3). Process for the production of metallic Hollow castings, especially cylinder liners for Reciprocating internal combustion engines, especially for Large diesel engines, with the hollow castings one have first and a second region and the Wall thickness of the hollow casting in the first area is larger than in the second area, in which Process a casting compound (6) into a casting mold (1) is introduced and solidifies there, thereby characterized that the outer shape of the Hollow castings in the first area through a mold (3) and in the second area by a sand mold (2) is formed. The method of claim 11, wherein for molding the outer shape of the hollow casting in the first area a one-piece mold (3) is used. The method according to claim 11 or 12, wherein the mold (3) before the pouring of the casting compound (6) heated by a fluid medium, especially air becomes. Method according to one of claims 11-13, wherein the Chill mold (3) during and / or after the introduction of the Casting compound (6) through a fluid medium, especially air, is cooled. Hollow casting, especially cylinder liner for a reciprocating internal combustion engine, especially for one Large diesel engine, with two areas different wall thickness, made with one Casting mold (1) according to one of claims 1-10. Hollow casting, especially cylinder liner for a reciprocating internal combustion engine, especially for one Large diesel engine, with two areas different wall thickness, manufactured according to a Method according to one of claims 11-14. Reciprocating internal combustion engine, in particular Large diesel engine, with at least one Cylinder liner according to one of claims 15 or 16.

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