Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0637—Accessories therefor
  • B22D11/068—Accessories therefor for cooling the cast product during its passage through the mould surfaces
  • B22D11/0682—Accessories therefor for cooling the cast product during its passage through the mould surfaces by cooling the casting wheel

Definitions

• This invention relates to apparatus for casting of molten materials and especially casting molten metals. It is more particularly concerned with continuous casting machines.
• a desirable property of almost any metal alloys, preferably in its as-cast 'condition, is a uniform distribution within the cast product of the constituents and impurities normally found in the alloy.
• constitutituent means one of the intended ingredients or elements which make up a metallurgical system or a phase or combination of phases which occur in a characteristic configuration in an alloy microstructure.
• impurities means elements or compounds whose presence in any material is unintended and generally undesired.
• Constituents would include the materials combined into a metallurgical system to produce the particular type of alloy being cast but would not include the impurities, or undesired elements or compounds present in the cast metal.
• segregation of the components in the cast alloy makes it less suitable for subsequent processing such as forging or rolling.
• the term "segregation” also has what applicant believes to be its normal meaning in the art. That is, segregation is a term used to describe the non-uniform distribution or concentration of constituents (and/or impurities) which arises during the solidification of a metal.
• a concentration or accumulation of impurities in various positions within a metal is referred to in the art as segregation.
• the segregation that occurs between the arms of dendrites is referred to as minor or microsegregation and thus the composition may vary within a single crystal.
• Macrosegregation occurs around primary or secondary shrinkage cavities, such as pipe and in similar regions, and is often revealed in some castings as marked lines, having a pronounced erect or inverted cone shape, which are made evident when the ingots are sectioned and etched.
• Zones of segregation tend to occur in but are not limited to, the middle regions of the casting and usually within that part mainly occupied by equiaxed crystals.
• Microsegregation may sometimes be overcome by annealing, but macrosegr ⁇ gation often persists through subsequent heating and working operations.
• So-called pipe segregates may occur around the pipe cavity.
• the constituents (solute) in the iron (solvent) rejected from the freezing liquid are known to accumulate at the advancing solid/liquid interface so that the constituents of lowest melting point concentrate in the last portions to solidify.
• inverse segregation for example in aluminum alloys, this is reversed, for the liquid with high solute concentration becomes trapped in between the dendrites, thereby causing a decrease in concentration of solutes from the surface toward the center.
• Inverse segregation is a _ concentration of constituents or impurities to a higher degree near the outer surfaces (as compared to the interior) of an ingot or casting.
• Prior art methods of casting alloys have provided cast products having a relatively high degree of segregation of impurities and alloying materials within the cast bar. Because of the high level of constituents and impurities in many aluminum and steel alloys, inverse segregation frequently occurs. Such uneven distribution of impurities and/or constituents within the cast bar makes it desirable that the total amount of such within the alloy be reduced so that subsequent processing of the cast bar does not result in unacceptable internal and surface characteristics in the product manufactured from the cast bar. A reduction in the total amount of impurities, however, usually requires expensive additional refining of the alloy prior to casting and is sometimes commercially unfeasible or impractical altogether, while on the other hand the addition of particular constituents (including alloying elements) is sometimes desirable or necessary.
• Finished products such as wire and cable produced from aluminum alloy bar cast with prior art non-uniform cooling methods have lower electrical conductivity, strength, and ductibility qualities than those produced by the present invention.
• Some degree of remote adjustment was provided by dividing the sprays into groups and supplying Water to a central, partitioned manifold. Each supply pipe from the manifold to the sprays was controllable, as was the collective supply from a main, remotely controllable source. This technological step enabled continuous casting of copper and its alloys in such a casting machine.
• the '369 patent was an attempt to provide even greater uniformity of casting wheel cooling to the moving casting mold, though it was necessarily more complex, and subject to clogging of the cooling passages when using unsophisticated and unclean water sources for cooling water.
• the improvement of the present invention in cooling uniformity and effectiveness is achieved by incorporating remotely variable individual spray nozzle adjustment and control method and apparatus such that extremely precise cooling control is achievable about and along the casting path, even though various casting conditions may become present during a cast.
• the nozzle changes are shown effected, by way of example but not limitation, by means of pneumatic controls. Changes may similarly be effected by electrically driven valves, which may also be remotely and individually adjusted. Any known pressure means, including hydraulic pressure, may be used. With pneumatic controls, failure of the pneumatic system may cause loss of control over coolant flow from the individual nozzles and collectively, over the entire system. This could be a catastrophic event when casting certain metals which react explosively to contact with water by forming superheated steam extremely rapidly.
• Another object of this invention is to provide means for the remote adjustment of cooling applied to the cast metal along the casting path.
• Yet another object of this invention is to accomodate the need to precisely and accurately vary the application of coolant, by remote means, at a multiplicity of segmented locations along and peripherally about the longitudinal path of travel of the casting.
• Still another important object of this invention is the provision of method and apparatus to smoothly, uniformly, and effectively change the cooling conditions along and about the casting path to accomodate variations in the casting conditions or parameters.
• Yet another important object of this invention is the provision of method and apparatus to vary the cooling conditions transverse to the casting path such that cast strip could be cooled differently across the width of the strip.
• Still another object of " this invention is the provision of method and apparatus for localized detection and remote signaling of cooling conditions along the casting path, so as to enable continuous control of cooling parameters.
• FIG. 1 is a side elevation view of a typical wheel-band continuous casting apparatus incorporating the cooling means of the present invention
• FIG. 2 is a side elevation view of the wheel-band casting machine of FIG. 1
• FIG. 3 is a view of a typical spray manifold
• FIG. 4 is a sectional view of one form of remotely adjustable spray nozzle suitable for incorporation in the present invention.
• Figure 1 illustrates one typical, system for continuously casting and forming a molten metal.
• the molten metal to be cast is supplied by a melting or holding furnace 1 in which the chemical composition and temperature of the metal are adjusted as necessary.
• the molten metal is then introduced in a continuous manner into the moving mold portion of the casting apparatus 20, which mold is formed by a thin metallic band covering a portion of a peripheral groove in a rotatable casting wheel. Coolant is applied to the mold surfaces, to functionally extract the heat from the molten metal at a rapid rate to both " solidify the metal and to prevent the mold surfaces from overheating.
• the cast metal bar is extracted from the casting apparatus 20 and typically guided through a shearing station 30, which may be used to sever sections of the cast bar if required during the initial starting up of the system, and through a bar preparation station 40 which may clean or condition the bar for rolling.
• a rolling mill 50 works the cast metal bar into rod by a plurality of roll stands which each reduce the bar cross section while elongating it into wrought rod.
• the wrought rod is guided through a cleaning and/or cooling section 60 and thence to a coiler, station 70 where the finished rod is collected into coils for convenient handling, storage, or shipment.
• Casting machine 20 includes a rotatable casting wheel 211, an endless flexible metallic band 212, and band positioning rollers 214a, 214b, 214c, 214d which position and guide the band 212 about a portion of the casting wheel 211.
• the casting wheel 211 is removably affixed to rotatable support plate 215 which in turn is adapted to be driven by a variable-speed motor (not shown) -so as to rotate the wheel assembly in a clockwise direction.
• the casting wheel 211 has an outwardly facing annular peripheral groove which is closed by band 212 to form an arcuate mold cavity which extends about the lower portion of casting wheel 211.
• the first band positioning roller 214a r which is hereinafter called the presser wheel, functions to position or press the band 212 against the casting wheel 211 so as to tightly seal this portion of the peripheral groove which is to receive the molten metal.
• the last band positioning roller 214d which is hereinafter called the tension wheel, is usually movable in a vertical direction and functions to tension band 212 against the lower portion of the casting wheel 211.
• band positioning rollers 214b and 214c which are often called idler wheels and which function merely to guide the band 212 along its path from the tension wheel 214d back to the presser wheel 214a.
• the band 212 sealingly engages the casting wheel 211 so that as casting wheel 211 is rotated by support plate 215, the band 212 is urged along its path at the same speed.
• a moving mold cavity is formed within the lower portion of the casting wheel.
• Molten metal is supplied to the moving mold cavity from a furnace through a pouring pot 225 and pouring spout 224.
• the rate of flow of molten metal from the pouring spout 224 is regulated by suitable means so that the level of the molten metal pool within the casting mold remains just below the point at which the presser wheel 214a seals the band 212 against the peripheral groove in the casting wheel 211.
• the molten metal is carried along its arcuate path within the moving mold where it is solidified by the cooling system and subsequently extracted as a cast bar for further processing.
• the cooling system comprises a multitude of liquid spraying nozzles which direct a coolant, such as water, against the surfaces of the casting wheel 211 and the band 212 so as to extract heat therefrom thus also extracting heat from the metal within the moving mold.
• a coolant such as water
• Cooling of the mold is accomplished with a plurality of cooling manifolds disposed along and about the continuous casting path.
• a large inner manifold 249 as configured in FIG. 2 shows a multiplicity of individual spray nozzles 230 for directing coolant (not shown) against the inner periphery of the casting wheel Z'll. Coolant is supplied to manifold 249 via coolant supply pipes 262 and 263.
• a series of external coolant manifolds are normally disposed alongside the casting path outside of the mold.
• Such manifolds may each be of single chamber or multiple chamber design, as desired.
• the band spray apparatus is comprised of multiple manifolds 240, 241, and 242, although a single manifold may also be used. Coolant is supplied to the manifolds through supply pipes 237, 238, and 239. Manifolds are also used to supply coolant to a multiplicity of sprays (not shown) for the sides of the casting mold; FIG. 2 shows two side manifolds 245, 246 on the exposed side; the manifolds on the other side are hidden from view. Again, a single manifold may be used. In this example, coolant from pipe 263 is supplied to the manifolds
• OMPI via pipes 247, 248.
• manifolds are not shown in these drawings. The methods indicated are discussed above ' and may be applied as described above. All of the manifolds may be curved as required.
• FIG. 3 there is shown a portion of an interior wheel spray manifold adapted for use according to the present invention, including manifold coolant supply pipe 100, manifold 101, and a series of individual remotely controllable valve and spray cooling nozzles means 102, 103, 104, 105, and 106.
• One valve and nozzle means 106 is shown in partial cutaway view to enable observation of the general coolant flow path therethrough.
• FIG. 4 shows the coolant flow through the nozzle means more cleary.
• a coolant supply pipe 100 provides coolant under fluid pressure from a remote source means (not shown) to manifold 101, which in turn feeds each nozzle 102, 103, 104, 105, 106 means.
• a series of pneumatic valve control lines 107, 108, 109, 110, and 111 regulate the position of a valve, within the spray nozzle base, which valve is remotely controlled and regulated by controlling the fluid pressure on each valve as is more particularly described in association with FIG. 4.
• the nozzle means (102, 103, 104, 105, and 106) each comprises a valve (not shown) within a valve containing body 112, a control line 109, an internal coolant path 113, a preferably angularly offset nozzle base 114, and the nozzle per se, 115.
• Various spray patterns can be chosen from in selecting nozzles 115 having different spray deflection surfaces, such as are well known in the art.
• the spray valve remote control lines 107, 108, 109, 110 and 111 only generically represent control lines in FIG. 3. That is, the control line may consist of a sealed pneumatic tubing in the case where the spray nozzle control valve is pneumatically controlled, or of one or more electrical conductors where the spray valves are electrically controlled.
• the present disclosure is not intended to be limiting to a particular control method or mechanism, but is rather directed at the more general concept of individual remote control.
• FIG. 4 there is shown a more detailed view of the inner workings of one form of spray nozzle control valve.
• the body of the valve is fixed to the coolant manifold 101 in which coolant 120 is supplied under pressure via pipe 100.
• the valve body 112 includes therewithin a coolant passageway extending along the path from inflow orifice communicating passageway 113a to exit orifice communicating passageway 113b, along the path between which lies a flow control valve means including gate 122 and seat 121.
• Valve stem 123 extends into pneumatic cylinder 127 where a piston 124, sealingly engaged with the cylinder walls, is attached to valve stem 123.
• a stepped peripheral extension from valve stem 123 functions as a stop 125 for a spring 126 positioned between cylinder end cover 129.
• Spring 126 may be either an expansion spring (so as to close off coolant flow) or a retraction spring (so as to increase coolant flow) as desired.
• Pneumatic pressure changes within the cylinder effected by pressure changes applied via pneumatic control orifice 128, cause the pneumatic piston to open or close the valve, controlling coolant flow.
• the pneumatic pressure is communicated via tubing to remote control apparatus, which may be monitored by pressure/vacuum measuring devices to indicate coolant valve settings; the pressure/vacuum measuring devices may be calibrated in relation to coolant flow to remotely indicate coolant flow.
• the coolant flow may be remotely controlled by an electrical current applied to a small, high torque reversible motor connected to an externally threaded valve stem moving within a fixed threaded element, thereby opening or closing the valve or restricting the flow as desired.
• a small, high torque reversible motor connected to an externally threaded valve stem moving within a fixed threaded element, thereby opening or closing the valve or restricting the flow as desired.
• nonuniform character of the cast metal resulting from segregation, inverse segregation, liquation, and center porosity which results from non-uniform cooling (which may be caused by non-uniform casting rate or other casting parameters) can be avoided with the present invention.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)

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• 1983
  • 1983-12-22 WO PCT/US1983/002023 patent/WO1984002669A1/en not_active Application Discontinuation
  • 1983-12-22 EP EP19840900463 patent/EP0131599A4/de not_active Withdrawn
• 1984
  • 1984-01-04 CA CA000444617A patent/CA1216730A/en not_active Expired

Patent Citations (3)

Non-Patent Citations (1)

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