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Material Grades for Strip Mill Work Rolls
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Other Options
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ROCAST - The Centrifugal Casting System
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The mould for the production of rocast rolls consists of a one piece chill, that contains the entire moulding setup. The chills are over five meters in length, and vary in diameter to suit the specific roll dimensions required.
The mould to produce the top journal is made from self-setting chemically bonded sand, and is moulded directly into the top section of the chill.
The bottom journal is moulded with in-house produced sands, contained in an iron sleeve.
This sleeve, or insert together with a bottom fixing plate, is inserted into the bottom of the chill and held in place with steel pins.
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The assembly is completed by the fixing of the lid, which allows entry of the pouring pipes.
The rocast machine is buried 10 meters below the foundry floor, and is contained under a large steele cover. It consists of a turntable at the bottom, onto which a heavy steel shroud is held, with yolks at the top and bottom, each containing 12 hydraulically operated jacks that run agianst the shroud, keeping it perfectly vertical at all times.
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The assembled mould is lowered into position in the shroud, and then rotated to speeds of up to 800 revs per minute.
Next, pouring pies of adjustable length are inserted through the lid. The pipes terminate in specially designed ceramic nozzles, that direct the metal stream as required.
Once the mould is complete, the metal can be poured. To show to pouring sequence more clearly, the mould is seen below as a cross section diagramme.
The first metal poured, is a highly alloyed, hard-wearing shell material, which can be Alloy Indefinite Chill, High Chromium Iron or sophisticated High Speed Steels.
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The metal stream is directed at a carefully controlled angle, directly onto the mould surface, which rapidly chills the metal to produce a dense, fine-grained material.
Once poured, a thermocouple is inserted into the mould to read the temperature as the shell metal cools and solidifies.
At a specified temperature, the first, or butter layer of tough, high strength core metal is poured against the solidified shell. This can be of either flake or nodular iron.
After a specified time, the casting is filled with the remaining core metal, as simultaniously, the mould is decelerated. This fill follows a tightly computer controlled parabolic rate to ensure accurate pouring, and thus good casting integrity.
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At all stages of the cast, computer control and data logging occures, to allow detailed sybsequent analysis of casting parameters.
The completed casting is then left to cool for a number of days and, when cooled, the lid is removed from the mould and the chill lifted away from the casting and insert.
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The refractory materials are then removed and the cast roll is ready for heat treatment and machining.
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