US 4,693,298 AGranted

Means and technique for casting metals at a controlled direct cooling rate

AssigneeWagstaff Engineering, Inc.

InventorFrank E. Wagstaff

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Abstract

Close control of the direct cooling rate is achieved by bubbling a substantially insoluble gas into the curtain-forming coolant as it is about to discharge onto the emerging ingot. The resulting bubble-entrained curtain of coolant experiences an increased velocity, and the increase is not accompanied by a reduction in the thermal conductivity of the coolant. Instead, the bubble-entrained coolant appears to have a scrubbing effect on the metal, which breaks up any film and reduces the tendency for film boiling to occur at the surface of the metal, thus allowing the process to operate at the more desirable level of nucleate boiling, if desired. This in turn makes it possible to regulate the cooling rate by selective use of the bubbling effect, including turning the effect on and off to allow film boiling to occur when desired, such as in the butt forming stage of the casting operation. The bubbling effect can also be used to regulate the cooling rate when the coolant is in short supply and/or hotter than desired.

Claims40

Dependent claims

In the process of continuously casting metal as ingot by introducing molten metal to the cavity of an annular mold, through one end opening thereof, and while the metal undergoes partial solidification in the mold to form a body of the same on a support adjacent the other end opening of the cavity, reciprocating the mold and support in relation to one another endwise of the cavity to elongate the body of metal through the latter opening of the cavity, the improvement comprising:

introducing liquid coolant to an annular flow passage which is circumposed about the cavity in the body of the mold and opens into the ambient atmosphere of the mold adjacent the aforesaid opposite end opening thereof to discharge the coolant as a curtain of the same that impinges on the emerging body of metal for direct cooling of the same,
a gas, which is substantially insoluble in the coolant liquid, under pressure into an annular distribution chamber which is disposed about the passage in the body of the mold and opens into the passage through an annular slot disposed upstream from the discharge opening of the passage at the periphery of the coolant flow therein,
releasing the body of gas in the chamber into the passage through the slot,
subdividing the body of gas into a multiplicity of gas jets as the gas discharges through the slot, and
releasing the gas jets into the coolant flow at a temperature and pressure at which the gas is entrained in the flow as a mass of bubbles that tend to remain discrete and undissolved in the coolant as the curtain of the same discharges through the opening of the passage and impinges on the emerging body of metal.

2 more elements

In apparatus for continuously casting metal as ingot by introducing molten metal into the cavity of an open ended mold at one end opening thereof, while continuously withdrawing partially solidified metal as ingot from the opposite end opening of the mold, the improvement comprising:

means defining an annular flow passage which is circumposed about the cavity in the body of the mold to carry liquid coolant, and which opens into the ambient atmosphere of the mold adjacent the aforesaid opposite end opening thereof so as to direct the liquid coolant at the surface of the ingot as it emerges from the mold to extract heat from the same,
means for introducing liquid coolant into the annular flow passage,
means defining an annular gas distribution chamber which is disposed about the flow passage in the body of the mold,
means for opening the chamber to the passage including an annular slot disposed upstream from the discharge opening of the passage at the periphery of the coolant flow therein,
means for charging a body of pressurized gas into the annular distribution chamber,
means for releasing the body of gas into the passage through the slot when the chamber is open to the passage, and
means in the slot for subdividing the body of gas into a multiplicity of gas jets as the gas discharges through the slot, and for entraining the gas in the flow of coolant as a mass of bubbles that tend to remain discrete and undissolved in the flow as it discharges through the opening of the passage and impinges on the emerging body of metal.

4 more elements

Dependencies are inferred from the claim text.