Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Patent
1998-03-31
2000-05-16
Zimmerman, John J.
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
148512, 148531, 148902, 148903, 29888047, 1231936, B32B 1518, B32B 1520, F02F 310, B22D 1902, B22D 1916
Patent
active
060635096
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a reinforcing component of which the basic material is austenitic cast iron and which is intermetallically bonded with an engine component made from an aluminum-based alloy, in particular a piston. Reinforcing components of this type are especially employed as ring carriers and in a few cases also as trough-edge protection in connection with aluminum pistons for Diesel engines.
The bond of the reinforcing component--which consists of austenitic grey cast iron alloy in most cases--with the material of the piston is produced by the Alfin-process, which is known in the state of the art since about 1950, by immersing the reinforcing component in an AlSi-melt before the piston material is poured around it, whereby an intermetallic layer develops on the surface of the reinforcing component.
2. The Prior Art
The stresses to which pistons are exposed in Diesel engines, which have continually increased in the past, have revealed the strength limits of alfin-bonds produced heretofore, so that a higher bonding strength is required.
Therefore, it was proposed in DE-OS 42 21 448 to employ austenitic cast iron with a globular or vermicular graphite configuration as reinforcing material, which improves the strength of the bond as compared to the usual grey cast iron alloy material with a lamellar graphite configuration.
The drawbacks of this solution include abandonment of a ring carrier material that has been successfully used for a long time, poorer workability, lower thermal conductivity and slightly poorer resistance to wear of the grey cast graphite material as compared to the grey cast iron alloy type. In addition, grey cast iron qraphite material is slightly more expensive than the grey cast iron alloy type.
SUMMARY OF THE INVENTION
The invention, therefore, deals with the problem of increasing the strength of reinforcing materials of the type specified above and also the reproducibility of the intermetallic bond irrespective of whether the basic material has a grey cast graphite or grey cast alloy graphite configuration.
This problem is solved by a reinforcing component of which the basic material is austenitic cast iron, and which is intermetallically bonded with an engine component made of an aluminum-based alloy, in particular a piston in which the structure of the surface of the reinforcing component is austenitic-ledeburitic at least in areas in the vicinity of the intermetallic bond.
Within the context of the present invention an austenitic-ledeburitic structure is understood to be one that is preferably obtained by remelting austenitic cast iron and where austenite and ledeburite are present next to each other.
Owing to the very fine austenitic-ledeburitic structure and the also very fine nonlamellar configuration of the graphite, a flawless intermetallic layer can develop when the reinforcing component is immersed in a melt bath based on Al. First tear-off tests showed that the tensile strength of the layer as defined by the invention can be increased by at least another 30% as compared to the intermetallic layer with a globular graphite configuration as known from DE-OS 42 21 448.
The surface of the reinforcing component in the zone of the intermetallic bond can be formed austenitic-ledeburitically by remelting it either wholly or in part areas, with ring carriers preferably in the vicinity of the back of the ring carrier.
The laser, the induction or the WIG (tungsten-inert-gas) process can be considered as processes for remelting the reinforcing material.
Hard ingot casting offers another possibility for producing reinforcing components from austenitic cast iron with an austenitic-ledeburitic surface. With ring carriers, however, the problem is that such carriers no longer can be manufactured by the centrifugal casting process, and that due to the poor workability of ledeburite such ring carriers cannot be manufactured as usual by cutting them from cast sleeves but have to be additionally treated by separation and precisi
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Hudelmaier Birgit
Mueller-Schwelling Dieter
Schlosser Detlef
Mahle GmbH
Zimmerman John J.
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