DE10342582A1 - Production of a gradient workpiece by layer casting - Google Patents

Abstract

In a method for producing a cast piece, in particular a machine element, such as a cylinder block, from cast iron containing graphite, according to the invention, cast iron batches and / or alloys containing different graphite structures are cast in succession into a mold (2) for different stress zones (4, 3) of the cast piece, as a result of which there is the possibility of better adapting the local material properties to the stress situation than when producing from a single homogeneous melt. A device which is particularly suitable for carrying out the method is also described.

Description

The Invention relates to a method of manufacturing a casting graphite cast iron with the characteristics of the generic term of Claim 1. It also relates to a particular Carry out of the method suitable device and on the castings produced therewith and their uses.

Known is from DE-A1-36 22 511 a method for pouring on a (precious) metal body another (precious) metal body, a second metal melt on the first cast body is infused. This creates a gap-free intermediate area between the two workpieces. According to the above However, the document is printed before the infusion second body a release agent layer made of graphite applied, which is a fusion of the two cast bodies should prevent.

As a general rule it is known that spatially complicated castings, z. B. gear or motor housing, cylinder blocks and heads etc., locally in the company very different loads depending on the functional area get abandoned. Using the example of cylinder blocks for highly stressed diesel engines and / or weight-optimized diesel or gasoline engines this in advance discussed.

• – 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

• - In the walls of the cylinder bores favorable tribological properties in interaction with the piston rings are expected. 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).

To the to water of engine parts such as cylinder blocks are various iron-carbon casting alloys to the expert with different graphite shapes and alloy compositions known: lamellar graphite (GJL), vermicular graphite (GJV), spheroidal graphite (GJS) and their possible transitional forms (see e.g. DE-A1-199 42 780). So far, GJL has mostly been in the Classes GJL-250 to GJL-350 are used. This material, in particular in alloy design, is particularly suitable for the cylinder bores or walls because Lamellar graphite is a good tribological partner for the pistons is and the castings they are technically easy to manufacture and machinable. However, because the lamellar graphite is in a mostly pearlitic matrix affects the fatigue strength of the casting due to internal notch effects, is he for highly charged diesel engines cannot be used without restrictions.

For such maximum stress is therefore common GJV - cast iron with compact graphite inclusions - used. With the realization of ever higher ones Ignition pressures there there are already requirements, GJS, i.e. spheroidal graphite cast iron, to use. However, the latter two materials have also manufacturing disadvantages, because they tend z. B. to higher porosity. In particular are they for the high-speed machining less useful, e.g. B. if Cylinder bores and oil passages PCBN cutting should be introduced.

It is fundamental known (DE-A1-25 18 637), the graphite structures in the manufacture of cast iron pieces in the melt by an "inmould" treatment immediately before pouring in modify the shape as needed.

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

A device is also to be created which is particularly suitable for carrying out the method according to the invention. This object is achieved according to the invention with the features of patent claim 1. The features of claim 11 indicate a corresponding device, while corresponding castings are claimed in claim 20. The characteristics of the independent claims Chen subordinate claims indicate advantageous developments of the invention.

By Application of the method according to the invention becomes a casting in a uniform form from different cast iron batches manufactured, the properties of which better reflect the different areas Operating stresses can be switched off or adapted to them as with a homogeneous cast iron batch or alloy for the whole Casting is possible. Such a casting can also be used as a gradient casting can be referred to, since in any case its internal graphite structure is not the same everywhere.

It is not necessary as a particular advantage of the method according to the invention, in the sequence of casting waiting for the solidification of a melt that was filled in first, but you can immediately after reaching the one you want layer height or the degree of filling the mold with pouring the next Start batch. This does not make a really selective transition reached between batches or layers, but form it transitional forms, z. B. coral graphite, in the interfaces. This will, however on the one hand an intimate, quasi-autogenous connection between the two casting phases and there are no noticeable delays before switching to the second or subsequent casting phase.

you will be the ones discussed above Problems better than with conventional castings, because high strength and tribological properties are achieved there and vibration damping, where desired become. Received at the same time one the option for areas with little stress are not the most highly qualified Material or the most valuable To use alloy and therefore its disadvantages and consumption on the indispensable to restrict.

• 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 crank area from GJV and the cylinder area with water jacket / cooling channels from 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

From this analytically distinguishable layers result within of the outside homogeneous casting.

in the Case a) above is z. B. a cylinder block with more conventional Field of application while the cases b) and c) increased stiffness in the area of the cylinder walls and the water cooling jacket cause. The latter is included in highly charged diesel engines favors extreme combustion pressures and largely prevents them blow-by losses.

at the same execution case one becomes the cylinder axes during of casting or preferably orient vertically in shape, the cylinder area can be positioned above or below. One is preferred to climb to water, but also falling pouring possible is.

Around a separation height the different, the casting Defining forming layers in a reproducible manner is preferred each in height the intended (upper) end of the one to be filled with an alloy Provide one or more overflows. This is unnecessary about that also an exact quantity measurement of the respective batch be replenished Mold cavity.

A another advantageous embodiment provides that the running and gating system of a component or Alloy during of casting a second component or alloy is sealed so the two alloys cannot accidentally mix.

In yet another advantageous embodiment of the method according to the invention a common base melt is poured into the sprue. This is used to manufacture each of the different areas of the finished casting desired Graphite structures in a manner known per se by adding Modifiers, alloying elements, vaccines and other suitable Average in the pouring funnel, in the pouring stream or in the individual Running and gating system treated.

Next pouring of the different cast batches in succession in a barrel and gate system In a further advantageous variant, a running and gate system - for one or several cast batches (materials) used.

A device which is particularly suitable for carrying out the method discussed above will include different run and gate channels for feeding the individual melt batches to the areas of the mold which are to be filled with the differently alloyed and modified cast iron batches. When using a form to be filled in a vertical sequence, these different filling levels are staggered vertically. It is not necessary to separate the different layers, because the process according to the invention transitions or a quasi-autogenous course of the alloys in the transition areas is desired.

In another preferred embodiment the device is operated in increasing casting, whereby, as described above, falling pouring also conceivable is. It also includes at least one overflow from which the just cast batch can emerge from the mold as soon as the assigned batch Level reached is. As a result, in addition to an overfill protection, optical control of the melt level possible. It goes without saying that while of filling preceded by further layers of overflows encapsulated batches are sealed, in particular by solidification. The device can also contain closure devices with which inlets of batches cast first, while a Follow-up batch filled in the mold becomes. This will return the still fluid Precharge prevented on the principle of communicating 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 afterwards detailed description.

Further Advantages, characteristics and features are the following detailed description of exemplary embodiments clearly, the purely schematic drawings show in

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;

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

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

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

In one device 1 for making the cylinder block by casting is a mold 2 aligned so that the axes of the cylinders 3 stand vertically - parallel to the direction of gravity. In the area of the crankcase 4 you can see a power flow area 5 who later has to absorb the gas forces. You can also see the crankcase outer wall 6 , The inside of the form 2 crankcase arranged below the cylinder bank with its cooling water jacket 4 is a first run and gate system 7 cast. The melt flows into the mold 2 is on the bottom of the latter, so it is poured upwards. An overflow 8th 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 can be filled with a first batch of cast iron, preferably vermicular or spheroidal graphite. Of course, more than one overflow can be provided at the same level; the arrangement is shown here only schematically simplified.

The melt emerges from this overflow 8th out, that's the shape 2 filled with the casting material with the properties desired for the area of the crankcase. This has the advantage that you don't necessarily have to work with a precisely defined amount of melt, but can work with a tolerable tolerance.

One then closes with the aid of a closure device 9 the first running and gating system 7 , The overflow 8th is closed by rapid solidification. A second barrel and gate system is now used on the still liquid first cast batch 10 cast a second cast batch from a material (also in increasing cast) that has the properties desired for the cylinder walls, preferably with lamellar graphite or vernicular graphite. The preferred combinations with the material of the first cast batch have already been discussed above.

With this procedure, no sharp boundary area is formed between the two materials, rather, mixing occurs in the border area, that is, approximately at the level of the overflow 8th or the transition from the crankcase to the cylinder bank, both cast batches in a limited area. The filling speed of the second batch is to be determined according to professional judgment, because this may influence the degree of mixing in the limit area.

The locking device 9 prevents that after the material has been introduced via the first barrel and gate system 7 this is pushed back again (communicating tubes) when the material passes through the second barrel and gate system 10 is filled. You could use the shape 2 deviating from the illustration, basically also arrange with the cylinders facing downwards and the casting material intended to form their walls first via the first barrel and gate system 7 - Pour in until it overflows 8th exit. After that, the crankcase would 4 about the second barrel and gate arrangement 10 cast from the designated material. This does not change the result / product achieved.

In the version described here are the two barrel and gate systems 7 and 10 shown completely separate from each other. As already explained above, they can nevertheless in principle be fed from the same base melt if the means for providing the respective different graphite structures are provided in the systems mentioned (not shown). For large series production, however, it is also conceivable to keep different base melts available, from which the respective barrel and gate systems can then be filled individually.

The 2 shows in a representation similar to that 1 a variation 1' the device 1 out 1 , In the 2 shown device 1' also has two barrel and gate systems 7 and 10 on, now with the barrel and gate system 7 the cylinder area and with the barrel and gate system 10 the crankcase area is cast, first the crankcase area with the barrel and gate system 10 and then the cylinder area with the barrel and gate system 7 is poured.

For this are in the running and gating system 10 two distribution strips 11 and 12 provided that extends along the crankcase outer walls 6 extend and directly fill the mold over the entire length of the cylinder crankcase to be cast 2 in the area of the crankcase outer walls 6 enable. This results in a particularly favorable filling of the crankcase outer walls 6 without turbulence, so that a uniform microstructure is created.

The cylinder area 3 is distributed over several central inlets, also distributed over the length of the cylinder crankcase 13 of the running and gating system 7 filled with a second casting batch, different from the first casting batch, which results in a different structure with a different graphite formation compared to the crankcase. By providing multiple central inlets 13 below the respective lower edge of the cylinder area 3 Even material distribution over the cylinder tube bank is also achieved here.

Another modification of the device 1' out 2 is with the device 1'' in 3 shown. Here is the running and gating system 7 modified in that the central inlets 13 when filling the cylinder area through the inlets 14 and 15 have been replaced directly in the shape of the cylinder wall 2 lead. In addition to providing multiple enemas 14 and 15 that are about the circumference of the cylinder 3 are distributed, an annular inlet can also be provided, so that direct and immediate filling of the cylinder wall is possible. This allows a more defined setting of the microstructure in the cylinder area 3 be made.

The 4 shows a device 1''' , in which the crankcase to be cast or the corresponding shape 2 by 90 ° compared to the embodiments of 1 to 3 is rotated so that the cylinder axis is arranged horizontally, that is perpendicular to the direction of gravity. In addition to the first barrel and gate system 7 and the second running and gating system 10 is with this device 1''' a third running and gating system 17 intended. With the different barrel and gate systems, which are staggered vertically, and the appropriately arranged overflows 8th 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 can be laterally cooled at the appropriate point in order to influence the solidification and consequently the microstructure.

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 Running and gating 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 ), made of graphite-containing cast iron, characterized in that for different stress zones of the casting, different cast iron batches and / or alloys containing or forming graphite structures are formed into a mold ( 2 ) pours. A method according to claim 1, characterized in that successive cast iron batches in succession before the solidification of each cast iron batch previously cast into the Filled in form. A method according to claim 1 or 2, characterized in that that the graphite structures of different cast iron batches made of lamellar graphite (GJL), vermicular graphite (GJV) and / or spheroidal graphite (GJS) and their transitional forms selected are. Method according to one of the preceding claims, characterized in that the shape ( 2 ) is filled in an increasing and / or falling manner. Method according to one of the preceding claims, characterized in that for individual areas of a graphite structure or cast alloy, a separate running and gating system ( 7 . 10 ) is used and / or that in a barrel and gate system 2 up to n cast iron batches (layers) are introduced in a chronological order. Method according to one of the preceding claims, characterized in that by at least one in the mold cavity ( 2 ) introduced overflow ( 8th ) the fill level of a batch in the form ( 2 ) is limited. Method according to one of the preceding claims, characterized in that after pouring in a first batch, its running and gating system ( 7 ) is sealed 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 chamber area ( 4 ) from GJV and the cylinder area ( 3 ) from GJL or - the crank area ( 4 ) from GJS and the cylinder area ( 3 ) from GJV or - the crank area ( 4 ) from GJS and the cylinder area ( 3 ) is made from GJL. Method according to one of the preceding claims, characterized characterized that spatially and / or time-dependent influences the temperature of the melt, in particular chilled is used in order to influence the microstructure of the casting in a targeted manner. Device for carrying out a method according to one of the preceding method claims, characterized in that a casting mold ( 2 ) to produce a casting from several batches of cast iron differentiated by their graphite structures and / or alloy contents different barrel and gate systems ( 7 . 10 ) are assigned, each of which is intended for filling one or more specific cast iron batches. Apparatus according to claim 11, characterized in that the running and gating system ( 7 ) for the cast iron batch to be filled first into the bottom of the mold cavity ( 2 ) flows out. Apparatus according to claim 11 or 12, characterized in that the mold cavity ( 2 ) with at least one overflow that limits the fill level of a cast batch ( 8th ) is connected, which is especially designed so 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 ) in the mold cavity ( 2 ) are staggered vertically and / or horizontally. Device according to one of the preceding device claims, characterized in that in at least one running and gating system ( 7 ) a locking device ( 9 ) is provided. Device according to one of the preceding device claims, characterized characterized that means in at least one running and gating system to modify the graphite structure of the continuous cast batch are provided. Device according to one of the preceding device claims, characterized characterized in that one or more means for regulating the temperature, especially coolant are provided, which are particularly spatially and / or temporally variable affect the temperature of the melt. Device according to one of the preceding device claims, characterized characterized in that one or more barrel or gate systems are provided are that have manifolds that are at least along one Extension direction of the to be filled Cast range are arranged around the casting at least over the entire length of this Direction of extension uniform and / or to fill with little turbulence. Device according to one of the preceding device claims, characterized characterized that the running and gating system directly in the to be filled Casting area flows into or about one or more central inlets is evenly distributed. Cast part, especially engine or cylinder block or cylinder crankcase made of graphite-containing cast iron, which in particular according to the process according to one of the claims 1 to 10 is made, characterized in that the casting in Areas with different requirement profiles from layers or areas with different graphite structures and / or Alloys is formed. casting according to claim 20, characterized in that the areas with different graphite structures and / or alloys through training merge into mixed areas, in particular in the mixed areas mixed forms of the graphite structures available.