EP1477661A2 - Producing of a gradient-workpiece by layer-casting - Google Patents

Abstract

Method involves making the workpiece from cast iron containing graphite, using different graphite structures for different zones of the workpiece that are subject to different stresses. Cast iron charges and/or alloys that are cast in a mold contain or form the different graphite structures. An independent claim is also included for: (a) apparatus for implementing the inventive method (b) and a cast item, especially an engine or cylinder block or cylindrical crankcase of cast iron with graphite.

Description

The invention relates to a method for producing a casting from graphite-containing Cast iron with the features of the preamble of claim 1. It relates also on a device which is particularly suitable for carrying out the method, and on the castings manufactured with them and their uses.

DE-A1-36 22 511 discloses a method for pouring on a (noble) metal body on another (precious) metal body, on the body that was cast first a second molten metal is poured on. This creates a gap-free intermediate area between the two workpieces. According to the above However, print will be available a graphite release agent layer is applied to the pouring of the second body, which prevent the two castings from merging.

It is generally known that spatially complex castings, e.g. B. gear or motor housing, Cylinder blocks and heads etc., depending on the functional area, very much in operation exposed to different stresses. Using the example of cylinder blocks for highly stressed diesel engines and / or weight-optimized diesel or petrol engines this will be discussed in advance.

• möglichst geringes Gewicht (kleine Wand- und Stegstärken, gewichtsoptimiertes Design);
• hohe Belastbarkeit gegen hohe Zünddrücke;
• gute Geräuschdämmung;
• gute Bearbeitbarkeit (Bohren, Schleifen, Fräsen, Honen, Innenspindeln, Gewindeschneiden etc.) in Großserienfertigungen;
• hohe Verschleißbeständigkeit.

The following requirements must be met for such components:

• weight as low as possible (small wall and web thicknesses, weight-optimized design);
• high resilience against high ignition pressures;
• good noise insulation;
• good machinability (drilling, grinding, milling, honing, internal spindles, thread cutting etc.) in large series production;
• high wear resistance.

• in den Wänden der Zylinderbohrungen günstige tribologische Eigenschaften im Zusammenspiel mit den Kolbenringen erwartet. Hierdurch sollen der Ölverbrauch verringert und die Inspektionsintervalle (Ölwechsel) ausgedehnt werden. Man wünscht einen geringen Reibungsbeiwert, hohe Verschleißbeständigkeit und hohe mechanische Steifigkeit gegen den Arbeitsdruck.
• im Kraftflussbereich um die Kurbelwellenlager hohe Festigkeit, Dauerfestigkeit und Steifigkeit gefordert.
• von den Außenwänden, insbesondere von der Kurbelraum-Außenwand eine hohe Steifigkeit gefordert, um die Geräuschentwicklung durch hohe Oberflächen-Dämpfung (geringe Oberflächenmobilität) zu verringern.

Be in detail

• Favorable tribological properties in interaction with the piston rings are expected in the walls of the cylinder bores. This is intended to reduce oil consumption and to extend the inspection intervals (oil change). A low coefficient of friction, high wear resistance and high mechanical rigidity against the working pressure are desired.
• high strength, fatigue strength and rigidity are required in the power flow area around the crankshaft bearings.
• a high degree of rigidity is required from the outer walls, in particular from the crank chamber outer wall, in order to reduce the noise development due to high surface damping (low surface mobility).

Various iron-carbon casting alloys are known to the person skilled in the art for casting engine parts such as cylinder blocks with different graphite shapes and alloy compositions known: lamellar graphite (GJL), vermicular graphite (GJV), Spheroidal graphite (GJS) and its possible transition forms (see e.g. DE-A1-199 42 780). So far, mostly GJL in the classes GJL-250 to GJL-350 have been used. This Material, especially in an alloy version, is particularly suitable for cylinder bores or walls because lamellar graphite is a good tribological partner for the pistons and the castings are technically easy to manufacture and machinable are. However, because the lamellar graphite in a mostly pearlitic matrix due to internal Notch effects affect the fatigue strength of the casting, it is for highly charged Diesel engines cannot be used without restrictions.

For such maximum loads, GJV cast iron with compact is often used Graphite inclusions - used. With the realization of ever higher ignition pressures there are also requirements to use GJS, i.e. spheroidal graphite cast iron. The two however, the latter materials also have manufacturing disadvantages because they tend z. B. to higher porosity. In particular, they are for high speed machining less useful, e.g. B. when cylinder bores and oil channels through PCBN cutting should be introduced.

It is fundamentally known (DE-A1-25 18 637), when producing cast iron pieces Graphite structures in the melt by an "inmould" treatment immediately before Pour into the mold to modify as needed.

The invention is based on the object of a method for producing a casting with differently stressed areas or zones, in particular a cylinder crankcase for internal combustion engines, to indicate with which different materials can be arranged in the casting according to the load.

A device is also to be created which is particularly suitable for carrying out the process according to the invention Process is suitable. With regard to the method, this object is achieved according to the invention solved with the features of claim 1. The features of the claim 11 indicate a corresponding device, while in claim 20 corresponding Castings are stressed. The characteristics of the independent claims subordinate claims give advantageous developments of the invention on.

By using the method according to the invention, a casting is made in a uniform Mold made from different batches of cast iron, their properties better geared to the different operational stresses in certain areas or to these can be customized as this with a homogeneous batch of cast iron or - Alloy is possible for the entire casting. Such a casting can also be used as Gradient casting can be called, because in any case its inner graphite structure is not is the same everywhere.

As a particular advantage of the method according to the invention, it is not necessary in which Sequence of casting to wait for the solidification of a melt that was filled in first, but one can immediately after reaching the desired layer height or the degree of filling start pouring the next batch into the mold. With that, though no really sharp transition between the batches or layers achieved, but transitional forms are formed, e.g. B. coral graphite, in the interfaces. hereby on the one hand, an intimate, quasi-autogenous connection between the two casting phases is achieved, and second, there are no noticeable delays before switching to the second or the following casting phase.

The problems discussed above are thus dealt with better than with conventional problems Castings, because you can achieve high strength, tribological properties and vibration damping where desired. At the same time you get the option not for high-stress areas also the most qualified material or to use the highest quality alloy and its disadvantages and To limit consumption to the essential.

a) der Kurbelraumbereich aus GJV und der Zylinderbereich nebst Wassermantel/Kühlkanälen aus GJL;

b) der Kurbelraumbereich aus GJS und der Zylinderbereich aus GJV;

c) der Kurbelraumbereich aus GJS und der Zylinderbereich aus GJL.

The following embodiments are preferably possible for an engine or cylinder block for an internal combustion engine:

a) the crankcase area made of GJV and the cylinder area together with water jacket / cooling channels made of GJL;

b) the crank area made of GJS and the cylinder area made of GJV;

c) the crank area made of GJS and the cylinder area made of GJL.

This results in layers that are analytically distinguishable from each other within the exterior homogeneous casting.

In the above case a) it is e.g. B. a cylinder block with more conventional Field of application, while cases b) and c) increased rigidity in the area of Cylinder walls and the water cooling jacket effect. The latter is used with highly charged ones Diesel engines with extreme combustion pressures preferred and largely prevented blow-by losses.

In the same embodiment, the cylinder axes become during casting or in orient the shape preferably vertically, the cylinder area positioned above or below can be. It is preferred to pour upwards, but also downwards is possible.

Reproducible by a separation height of the different layers forming the casting to define, one is preferred in each case in the amount of the intended (upper) end of the Provide one or more overflows with an alloy to be filled in the mold. This Furthermore, there is no need for an exact quantity measurement of the respective batch mold cavity to be filled.

Another advantageous embodiment provides that the running and gating system one component or alloy during the casting of a second component or alloy is closed, so that the two alloys do not accidentally can mix.

In yet another advantageous embodiment of the method according to the invention poured a common base melt into the sprue. This is used to manufacture the graphite structures required for the different areas of the finished casting in a manner known per se by adding modifiers, alloying elements, Inoculants and other suitable agents in the pouring funnel, in the pouring stream or treated in the individual running and gating system.

In addition to casting the various cast batches one after the other in a barrel and gate system In a further advantageous variant, a running and gating system is used used for one or more cast batches (materials).

A particularly suitable device for carrying out the method discussed above is Different run and gate channels for feeding the individual melt batches to include the areas of the form with the differently alloyed and modified Cast iron batches are to be filled. When using one to be filled in vertical order These different filling levels are staggered vertically. A separation of the different layers is not necessary, because according to the inventive method Transitions or a quasi-autogenous course of the alloys in the transition areas are desired.

In a further preferred embodiment, the device is operated in increasing casting, falling pouring is also conceivable, as described above. It includes the Furthermore at least one overflow from which the batch just cast from the mold can exit as soon as the level assigned to it is reached. This is next to one Overfill protection also allows a visual control of the melt level. It understands by itself that overflows preceded while filling more layers encapsulated batches are sealed, in particular by solidification. It can also Device contain closure devices with which inlets from first cast Batches are sealed while a subsequent batch is filled into the mold. In order to returns of the still liquid pre-batch based on the principle of communicating Prevents tubes. Further details and advantages of the method and the device according to the invention go from the drawing of an embodiment and their themselves here following detailed description.

Fig. 1

eine Schnittansicht einer ersten Vorrichtung zum Gießen eines Gussstücks in Gestalt von Zylinderblöcken für eine Verbrennungskraftmaschine aus Bereichen mit unterschiedlichen Graphitstrukturen;

Fig. 2

einen Schnittansicht einer weiteren erfindungsgemäßen Vorrichtung zum Gießen von Zylinderblöcken bzw. Zylinderkurbelgehäusen;

Fig. 3

eine weitere Schnittansicht einer erfindungsgemäßen Vorrichtung zum Gießen von Zylinderblöcken; und in

Fig. 4

eine Schnittansicht einer vierten Ausführungsform einer erfindungsgemäßen Gussform.

Further advantages, characteristics and features become clear in the following detailed description of exemplary embodiments, the purely schematic drawings in FIG

Fig. 1

a sectional view of a first device for casting a casting in the form of cylinder blocks for an internal combustion engine from areas with different graphite structures;

Fig. 2

a sectional view of a further device according to the invention for casting cylinder blocks or cylinder crankcases;

Fig. 3

a further sectional view of a device according to the invention for casting cylinder blocks; and in

Fig. 4

a sectional view of a fourth embodiment of a mold according to the invention.

In a device 1 for producing the cylinder block by casting, a mold 2 is like this aligned that the axes of the cylinders 3 are perpendicular - parallel to the direction of gravity. In the area of the crankcase 4, a power flow area 5 can be seen, which later has to absorb the gas forces. The crankcase outer wall 6 can also be seen arranged inside the form 2 below the cylinder bank with its cooling water jacket Crankcase 4 is cast over a first running and gating system 7. The inflow the melt in form 2 is at the bottom of the latter, so it is poured upwards. An overflow 8 is at the level of the transition from the crankcase 4 to the cylinders 3 intended. It marks the threshold up to which the Form 2 marks out with a first batch Cast iron can be filled with preferably vermicular or spheroidal graphite. Naturally more than one overflow can be provided at the same level; the arrangement is here shown only schematically simplified.

If the melt emerges from this overflow 8, the mold 2 with the cast material is included the properties desired for the area of the crankcase. This has the The advantage that you don't necessarily work with a precisely defined amount of melt must, but can work with a tolerable tolerance.

The first running and gating system is then closed with the aid of a closing device 9 7. The overflow 8 is closed by rapid solidification. On the still fluid the first casting batch is now a second by a second barrel and gate system 10 Cast batch cast from one material (also in increasing cast), which is suitable for the Has cylinder properties desired properties, preferably with lamellar graphite or Vemiculargraphit. The preferred combinations with the material of the first batch have already been discussed above.

With this approach, there is no sharp boundary between the two materials trained, rather mix in the border area, d. H. approximately at the level of the overflow 8 or the transition from the crankcase to the cylinder bank, both cast batches in a limited area. The filling rate of the second batch is professional Discretion to determine, because this may result in the degree of mixing in the Limit range can be influenced.

The closure device 9 prevents that after introducing the material over the first Running and gating system 7 this is pushed back again (communicating Tubes) when the material is filled in via the second run and gate system 10. Form 2 could also be used with the cylinders arrange downwards and the casting material intended to form their walls First fill in via the first run and gate system 7- until it comes out of the overflow 8 exit. Thereafter, the crankcase 4 would over the second barrel and gate arrangement 10 cast from the designated material. Changes to the result / product achieved nothing.

In the embodiment described here, the two running and gating systems are 7 and 10 shown completely separate from each other. As stated above, you can nevertheless be fundamentally fed from the same base melt if the funds to provide the different graphite structures in the systems mentioned itself (not shown) can be provided. For large series production, however, it is also conceivable to hold different base melts, from which the respective ones Running and gating systems can be filled individually.

FIG. 2 shows a modification 1 'of the device in a representation similar to FIG. 1 1 from Fig. 1. The device 1 'shown in Fig. 2 also has two running and Gate systems 7 and 10, now with the running and gate system 7 of Cylinder area and with the running and gating system 10 the crankcase area is poured, starting with the crankcase area with the barrel and gate system 10 and then the cylinder area with the barrel and gate system 7 cast becomes.

For this purpose, two distributor strips 11 and 12 are provided in the running and gating system 10, which extend along the crankcase outer walls 6 and over the entire Length of the cylinder crankcase to be cast a direct filling of the form 2 in the area allow the crankcase outer walls 6. This results in a special one favorable filling of the crankcase outer walls 6 without turbulence, so that a uniform microstructure is created.

The cylinder area 3 is over several, also over the length of the cylinder crankcase distributed central inlets 13 of the running and gating system 7 with a second, for first casting batch filled different casting batch, one compared to the crankcase different structure with a different graphite formation results. By providing of several central inlets 13 below the respective lower edge of the hole Cylinder region 3 also has a uniform material distribution over the cylinder tube bank reached.

A further modification of the device 1 'from FIG. 2 is with the device 1 "in FIG. 3 shown. Here, the running and gating system 7 is modified such that the Central inlets 13 replaced by inlets 14 and 15 when filling the cylinder area have been, which open into the form 2 directly in the area of the cylinder wall. Next the provision of a plurality of inlets 14 and 15, which extend over the circumference of the cylinders 3 are distributed, an annular inlet can also be provided, so that a direct and immediate filling of the cylinder wall is possible. This can be a more defined one Adjustment of the microstructure in the cylinder area 3 can be made.

Fig. 4 shows a device 1 "', in which the crankcase to be cast or the corresponding Form 2 is rotated by 90 ° with respect to the embodiments of FIGS. 1 to 3, so that the cylinder axis is horizontal, that is, perpendicular to the direction of gravity is arranged. In addition to the first barrel and gate system 7 and the second barrel and In this device 1 '", the gating system 10 is a third running and gating system 17 intended. With the different barrel and gate systems that are staggered vertically are arranged, and the correspondingly arranged overflows 8, it is possible to provide different graphite structures in layers in the cylinder crankcase.

In addition, there is a cooling element in the area of the crankcase on the crankshaft bearing 16 provided, with which the melt is laterally variably cooled at the corresponding point in order to influence the solidification and consequently the microstructure.

LIST OF REFERENCE NUMBERS

1,1 ', 1 ", 1'"

caster

2

shape

3

cylinder

4

crankcase

5

Power flow area

6

Crankcase outer wall

7

First running and gating system

8th

overflow

9

closure device

10

Second barrel and gate system

11.12

manifolds

13

Central enemas

14.15

enemas

16

heatsink

17

Third running and gating system

Claims (21)

Method for producing a casting, in particular a machine element such as a cylinder block (3, 4), from cast iron containing graphite, characterized in that cast iron batches and / or alloys containing or forming different graphite structures are cast in a mold (2) for different stress zones of the casting. A method according to claim 1, characterized in that successive cast iron batches are successively filled into the mold before the respective cast cast iron batch is solidified. Method according to claim 1 or 2, characterized in that the graphite structures of the different cast iron batches are selected from lamellar graphite (GJL), vermicular graphite (GJV) and / or spheroidal graphite (GJS) and their transition forms. Method according to one of the preceding claims, characterized in that the mold (2) is filled in increasing and / or falling casting manner. Method according to one of the preceding claims, characterized in that a separate running and gating system (7, 10) is used for individual areas of a graphite structure or cast alloy and / or in a running and gating system 2 to n batches of cast iron (layers) in in a chronological order. Method according to one of the preceding claims, characterized in that the fill level of a batch in the mold (2) is limited by at least one overflow (8) introduced into the mold cavity (2). Method according to one of the preceding claims, characterized in that after pouring in a first batch, its running and gating system (7) is closed before pouring in the subsequent batch. Method according to one of the preceding claims, characterized in that a base melt for producing the graphite structures desired in each case for the different areas of the finished casting by adding modifiers, alloying elements, inoculants and other suitable agents in the pouring funnel, in the pouring jet or in the individual barrel and Gate system (7, 10) is treated, in particular manganese sulfide and / or molybdenum disulfide is used. Method according to one of the preceding claims for casting an engine or cylinder block for internal combustion engines, characterized in that the crank area (4) made of GJV and the cylinder area (3) made of GJL or the crank area (4) made of GJS and the cylinder area (3) made of GJV or the crank area (4) is made of GJS and the cylinder area (3) is made of GJL. Method according to one of the preceding claims, characterized in that spatially and / or temporally variable influences the temperature of the melt, in particular cooling, in order to specifically influence the microstructure of the casting. Device for carrying out a method according to one of the preceding method claims, characterized in that a casting mold (2) for producing a casting from several batches of cast iron distinguishable by their graphite structures and / or alloy contents is assigned different barrel and gate systems (7, 10), each of which is provided for filling one or more specific cast iron batches. Device according to claim 11, characterized in that the running and gate system (7) for the cast iron batch to be filled in first opens into the bottom of the mold cavity (2). Apparatus according to claim 11 or 12, characterized in that the mold cavity (2) is connected to at least one overflow (8) which limits the fill level of a cast batch and which is in particular designed such that the melt solidifies quickly in the gate. Device according to one of the preceding device claims, characterized in that the inlets from the different running and gating systems (7, 10) into the mold cavity (2) are staggered vertically and / or horizontally. Device according to one of the preceding device claims, characterized in that a closure device (9) is provided in at least one running and gating system (7). Device according to one of the preceding device claims, characterized in that means for modifying the graphite structure of the continuous casting batch are provided in at least one running and gating system. Device according to one of the preceding device claims, characterized in that one or more means for regulating the temperature, in particular coolants, are provided which in particular spatially and / or temporally vary the temperature of the melt. Device according to one of the preceding device claims, characterized in that one or more running or gating systems are provided which have distributor strips which are arranged at least along an extension direction of the casting area to be filled in order to uniformly and / or at least over the entire length of this extension direction the cast part and / or fill with little turbulence. Device according to one of the preceding device claims, characterized in that the running and gating system opens directly into the cast part area to be filled or is evenly distributed over one or more central inlets. Cast part, in particular engine or cylinder block or cylinder crankcase made of graphite-containing cast iron, which is produced in particular by the method according to one of claims 1 to 10, characterized in that the cast part in areas with different requirement profiles from layers or areas with different graphite structures and / or alloys is trained. Casting according to claim 20, characterized in that the areas with different graphite structures and / or alloys merge into one another by forming mixing areas, in particular mixed shapes of the graphite structures being present in the mixing areas.

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