Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Reexamination Certificate
2001-04-27
2002-12-24
Elve, M. Alexandra (Department: 1725)
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
C164S479000, C164S324000, C164S330000
Reexamination Certificate
active
06497271
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pig casting machine comprising an endless conveyor belt, on which pig casting molds are fastened, for transporting the pig casting molds from a casting station to a pig removal station and vice versa, wherein each pig casting mold, with the mold cavity facing upwards, is filled with molten metal as it passes through the casting station, as well as a device for cooling the pig casting molds before, during and/or after casting wherein the pig casting molds are of a thin wall configuration and the rim areas of neighboring pig casting molds overlap.
2. Description of the Related Art
As is known in the art, liquid pig iron is either supplied after tapping in the blast furnace by means of ladles to the steel mill or, if it cannot be processed directly, is cast in the form of ingots, so-called pigs, for storage or for further transport. Pigs of pig iron have different weights depending on the desired application purpose; conventionally, a pig has a weight of 6 kg.
For manufacturing pigs of pig iron, pig casting machines are used. They are conventionally comprised of a casting station, at least one endless conveyor belt as well as a removal station at the first deflection point of the endless belt. Usually, a plurality of thick-walled casting molds are arranged on this endless conveyor belt. The respective casting mold is filled at the casting station with liquid pig iron. The conveying path of the pig casting machine must extend subsequently so far that the liquid iron in the respective pig casting mold is solidified before reaching the first deflection point of the endless conveyor belt and the shrinking enables removal from the casting mold. When passing through the deflection point, the casting molds automatically empty or the pigs are removed by means of a corresponding device from the molds. The pig casting molds or casting molds of known pig casting machines are manufactured of cast iron. In order to accelerate the solidification process of the liquid iron, the casting molds are cooled laterally, and additionally from above, with splashed water.
From German patent document DE 809 948 a pig casting machine for casting light metal and their alloys having correspondingly low melting points is known, wherein the pig casting molds are arranged as an endless belt. It is suggested to form the pig casting molds out of forged metallic material, for example, copper or aluminum or steel, instead of from cast iron. It is described that it is possible in this way to use relatively thin-walled pig casting molds because they can be cooled directly with water before, during, and after casting, for example, by splashing from below.
SUMMARY OF THE INVENTION
Based on this prior art, it is an object of the invention to provide a pig casting machine with increased production output, i.e., an increased quantity of cast molten mass per time interval, and at the same time minimal manufacturing costs for the pig casting molds.
This object is solved by at least one endless conveyor belt, on which pig casting molds are fastened, for transport of the pig casting molds from a casting station to a pig removal station and vice versa, wherein each pig casting molds, with the mold cavities facing upwardly, is filled when passing through the casting station with molten metal, as well as a device for cooling the pig casting molds before, during and/or after casting, wherein the pig casting molds have thin walls, characterized in that the pig casting molds are embodied for receiving molten metal having a melting temperature above 1,000° C.
The invention is based on the recognition, which has been proven by experiments, that the cooling of the pig casting molds makes it possible, quite in contrast to the decade-old unchanged casting exclusively of light metals with a low melting point, to use for casting heavy metals with melting points above 1,000° C. such pig casting molds which are comprised of a heat-resistant material whose melting point is even lower or not significantly higher than the respective melting point of the metal to be cast.
As a result of the minimal wall thickness, the heat conductivity of the pig casting molds is actually no longer of such importance as was the case in the known capacitive cooling. In contrast, the areal cooling across prevents their melting. The molten metal to be cast is, in particular, heavy metal, such as pig iron, which is cast conventionally at temperatures between 1450 and 1520° C. The pig casting molds are comprised preferably of copper whose melting point is approximately 1,083° C. However, materials with significantly reduced heat conductivity are conceivable, for example, heat-resistant steel, whose melting point, depending on its carbon contents, is within a range of 1,520° C.
Accordingly, the criteria for the material of the pig casting mold can be focused on other, essential properties, and, in particular, on the cold or hot forming properties which are decisive for the suitability in a rolling process and a preferred subsequent deep drawing, which allows a cost-efficient manufacture, as well as those mechanical properties at increased temperature which are decisive for the shape stability of the casting mold in use and their insensitivity against cracks. A preferred proposal of the invention suggests thus that the thin-walled precursor material for the pig casting molds is produced by rolling and is subsequently, for example, deep-drawn or die-formed.
According to a first preferred embodiment, it is proposed for achieving an improved cooling situation that carrying baskets on the respective endless conveyor belt are fastened for receiving the individual pig casting molds, wherein the carrying baskets are designed such that they are only partially in supporting contact with the pig casting molds. For this purpose, on the one hand, the inner contour of the carrying baskets is matched approximately to the outer contour of the pig casting molds and, moreover, the inner surface of the carrying baskets is provided with support pins for a point support of the thin-walled pig casting molds, wherein the diameter of the support pins on the carrying basket is not greater than the wall thickness of the pig casting mold. Accordingly, this fulfills the requirements in regard to ensuring a sufficient shape stability of the thin-walled pig casting mold as well as an unimpaired cooling as a result of the point support action.
The carrying basket can also be embodied as a grate basket which supports the respective pig casting mold like a net. In this connection, the configuration and the material for the support medium are to be selected such that they will not counteract a minimal elastic deformation of the pig casting mold as a result of the own weight of the pig. With this elastic deformation and thus minimal widening of the mold, loosening of the pig at the removal station is assisted.
The carrying basket itself can have rolls which run along guide rails. According to another embodiment, the basket is suspended by corresponding securing means in two parallel extending chains.
By means of the carrying basket it is possible to form the walls of the respective pig casting mold so as to be very thin. Casting molds with thin wall thicknesses have the advantage that the risk of fracture formation as a result of thermal stresses is minimized. With reduced wall thickness, however, the shape stability decreases, wherein this disadvantage is compensated by the support action of the carrying basket. As a result of only partial support by means of the support pins or the grate, cooling of the pig casting molds and thus of the cast body by splashing or immersion in a bath is not significantly impaired. In the embodiment of the carrying basket with support pins the diameter of the support pins on the carrying basket should correspond at most to the wall thickness of the pig casting mold so that the cooling at the points of attack of the support pins is not impaired. As a whole, a shape-stable pig casti
Albedyhl Manfred
Heinrich Peter
Hille Hartmut
Hille Volker
Kallenborn-Weber Ursula
Elve M. Alexandra
Kueffner Friedrich
McHenry Kevin
SMS Schloemann--Siemag Aktiengesellschaft
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