US3911996A

US3911996A - Apparatus for continuous casting of metals

Info

Publication number: US3911996A
Application number: US465554A
Authority: US
Inventors: Renald Veillette
Original assignee: Alcan Research and Development Ltd
Current assignee: Alcan Research and Development Ltd
Priority date: 1973-04-30
Filing date: 1974-04-30
Publication date: 1975-10-14
Anticipated expiration: 1992-10-14
Also published as: AU6836674A; IN141381B; ES425764A1; JPS5250011B2; ZA742543B; BR7403486D0; CA1023129A; FR2227071A1; CH584076A5; DK137786B; US3933192A; GB1473095A; JPS5026724A; CA1023130A; NL7405753A; FR2227071B1; DK137786C; DE2420997A1

Abstract

A method of continuously casting a substantially rectangular section metal ingot includes the steps of progressively increasing the gap between at least the mid-points of the two longer side walls of the mould, without substantially altering the gap between the side walls at their ends, as the speed of advance of the ingot through the mould increases from an initial slow speed; maintaining a water-filled zone in contact with the outer surfaces of the mould side walls, and, at least along said longer side walls, directing jets of water into the water-filled zone at closely spaced intervals towards said longer side walls; and emitting a substantially continuous curtain of water on to the surface of the ingot emerging from said mould. The waterfilled zone is defined by an envelope which, at least along said longer side walls, is flexible so as not to interfere with the flexing movement of said side walls.

Description

United States Patent [191 Veillette [21] Appl. No.1 465,554

[30] Foreign Application Priority Data Apr. 30, 1973 United Kingdom 20553/73 [52] US. Cl 164/82; 164/89; 164/273 R; 164/280; 164/283 M [51] Int. Cl. B22d 11/02 [58] Field of Search 164/82, 89, 273 R, 280, 164/283 R, 283 M [56] References Cited UNITED STATES PATENTS 3,741,280 6/1973 Kozheurov et al 164/250 FOREIGN PATENTS OR APPLICATIONS 1.191070 5/1970 United Kingdom 164/82 l-IZZ 1 Oct. 14, 1975 1,125,594 3/1962 Germany 164/283 M Primary ExaminerR. Spencer Annear Attorney, Agent, or Firm-Cooper, Dunham, Clark, Griffin & Moran ABSTRACT A method of continuously casting a substantially rectangular section metal ingot includes the steps of progressively increasing the gap between at least the midpoints of the two longer side walls of the mould, without substantially altering the gap between the side walls at their ends, as the speed of advance of the ingot through the mould increases from an initial slow speed; maintaining a water-filled zone in contact with the outer surfaces of the mould side walls, and, at least along said longer side walls, directing jets of water into the water-filled zone at closely spaced intervals towards said longer side walls; and emitting a substantially continuous curtain of water on to the surface of the ingot emerging from said mould. The water-filled zone is defined by an envelope which, at least along said longer side walls, is flexible so as not to interfere with the flexing movement of said side walls.

10 Claims, 6 Drawing Figures Sheet 1 of 2 3,911,996

US. Patent Oct. 14, 1975 US Patent Oct. 14, 1975 Sheet20f2 3,911,996

56.3 mqi I23 I14 I24 H7 APPARATUS FOR CONTINUOUS CASTING OF METALS The present invention relates to apparatus for the production of metal ingots, particularly aluminium and aluminium alloy ingots, by the direct chill semicontinuous casting process, that is to say, to process in which ingots are produced by pouring metal into an open-ended mould and applying coolant, usually water, directly to the solidified surface of the metal as it emerges from the mould.

In the production of large rectangular-section ingots for the production of rolled product, it is customary to impart a small amount of convex curvature to the long side walls of the mould to counteract the greater metal shrinkage which takes place near the middle of the wide faces of the ingot during solidification as compared with locations near the narrow faces of the ingot. By the use of these conventional moulds in which the distance between the wide faces is greatest at their midpoints, the upper parts of the wide faces of the ingot are controlled to an acceptable condition of flatness. However, the butt end of the ingot is formed when the rate of pouring molten metal is relatively low and, as a consequence, in the butt portion of the ingot the wide faces exhibit an undesirable amount of convexity when the above-mentioned conventional moulds are employed. Before an ingot is rolled it is customary to scalp the surface to remove surface defects and thus form a relatively smooth rolling face. The presence of a thick convex butt end frequently makes it necessary to scalp the wide faces of the ingot at the butt end to remove this convexity before a rolling face scalp cut can be made. The presence of the convexity near the butt end also leads to a safety hazard when the unscalped ingots are stacked.

In order to overcome this difficulty in an unpublished prior proposal it has already been proposed that each wide side wall of a mould for casting a rectangularsection ingot by the DC. (direct chill) semi-continuous casting process be made flexible and is provided with means for controlling the curvature of the side wall. Such means most conveniently takes the form of a screw jack acting on the side wall at one or more positions symmetrically disposed in relation to the midpoint of the wall by the operation of which bowing may be progressively applied to the side wall to flex it from an initial flat or slightly bowed condition at the beginning of the casting operation to an appropriately more pronounced bowed contour by the time the maximum dropping rate of the casting table has been reached.

In the prior proposal each flexible mould wall member is associated with a means for applying sub-mould cooling, i.e. the application of coolant directly to the solidified surface of an ingot emerging from the mould and means are also provided for cooling the mould wall itself. For this purpose the flexible mould wall member is associated with, but relatively movable in relation to a water supply conduit, formed with a row of orifices for directing jets of water onto the reverse face of the flexible wall member and with a separate conduit similarly formed with a row of orifices for directing jets of water onto the surface of an ingot emerging from the mould.

The flexible side wall members of the mould of the prior proposal preferably take the form of thick strips of a metal having heat-conductivity, such as copper or aluminium. Although the side wall member is free to flex or bow under the load applied by the jack or other means, the associated coolant supply system is substantially rigid and thus the position of the coolant supply system in relation to the mould wall and to the surface of the ingot emerging from the mould is variable, this variation increasing towards the centre of the mould wall where the extent of movement is greatest.

In an improvement of the prior proposal provided by the present invention the side wall member is provided with an associated flexible water jacket, which is arranged to flex with the side wall member and to provide a water outlet slit at the ingot outlet edge of the flexible mould wall member. Such slit may be arranged to be of substantially constant characteristics both in water emission characteristics and in positional relation to the adjacent ingot surface and this is a definite and substantial advance as compared to the supply of coolant from a relatively rigid water supply conduit. The flexible water jacket must be formed of material of high flexibility and extensibility, since it definesa substantially enclosed space at the reverse face of the mould wall member. In operation this space is maintained full of water. If the water jacket were made of metal of appropriate gauge for the service to be performed, it would have an excessive rigidifying effect on the adjacent mould wall. The flexible water jacket is therefore necessarily formed of a flexible synthetic material, chosen for its thermal-resistance characteristics, since it will be appreciated that first of all the flexible water jacekt must be in sealed relation with the metallic mould wall.

In order to achieve a high rate of heat transfer at the reverse face of the side wall member with the object of maintaining the temperature of the metal of the mould wall at as low a value as possible at its contact with the synthetic material of the water jacket, the water jacekt is preferably provided with means for directing jets of water somewhat obliquely onto the reverse surface of the mould side wall at closely spaced intervals. The flexible water jacket is therefore preferably provided with a longitudinally extending water conduit lying within the envelope and formed with spaced apertures for directing jets of water onto the mould wall. It is preferably made in the form of a flexible envelope which is secured in sealing relation to the side wall member at or near its upper edge, i.e. the edge adjacent the entry to the mould and is secured in spaced relation to the side wall member at or near its lower edge, i.e. the edge adjacent the exit of the mould, so as to define a slit between the envelope and the lower edge of the mould wall for the delivery of coolant for sub-mould cooling, the water supply conduit supplying water via the nozzles into the enclosed space thus defined. This slit permits the emission of a substantially continuous curtain of water from the water-filled space, i.e. a curtain of water extending substantially along the full length of the long side of the mould. The water supply conduit may take the form of a pipe, connected at intervals to the side wall member by support brackets, the pipe serving in turn as a support to hold the envelope in position in relation to the mould side wall member. However in a more preferred arrangement the en velope and water conduit are in the form of an integral plastics extrusion, so that the conduit forms part of the wall of the envelope. Whichever arrangement is adopted a means must be provided for supporting the lower edge of the envelope in parallel relation with the mould wall so as to maintain a slit of substantially constant width. This is preferably achieved by providing the envelope with a relatively stiff, but flexible, lower lip and connecting the envelope at or near the lip to the side wall member at a series of closely adjacent points.

Since the flexing of the side wall members is necessarily accompanied by a small amount of longitudinal movement in the region of their ends, it is necessary either to provide a rubbing seal between the side wall members and independently mounted stationary end wall members or arrange for the end wall members to move towards and away from each other in step with the flexing of the side wall members.

In a mould constructed in accordance with the present invention it is preferred to arrange that the end wall member and side wall members are formed into a unitary structure, so that the end wall members move towards and away from each other in accordance with the amount of bowing applied to the side members. Although this entails some reduction in the width of a flat ingot as the sides of the mould are bowed during the casting operation, this is of no concern, since the consequence is only that for the first few inches the width of the butt is less oversize. In this construction the end wall members are provided with associated water boxes of conventional design, the water boxes providing both cooling for the mould end walls and sub-mould cooling of the narrow faces of the ingot. The flexible water conduit is preferably carried around the ends of the mould so that there is interconnection between the water conduits along the two side walls of the mould.

Whilst it is usually preferred that the faces of the opposed side wall members of the mould should be truly parallel to the axis of ingot movement, it may in some instances be desirable to incline them slightly so that the gap between the outlet edges of the side wall members is slightly less than the gap at the inlet edges.

The provision of a mould with flexible side walls has various advantages in the direct chill continuous casting process. In addition to the primary object of substantially eliminating butt-convexity, it enables ingots of different composition to be cast without change of mould. In conventional practice it is frequently necesary, when casting a different alloy, to change the mould for a mould of different side wall convexity, because of the different shrinkage characteristics of various alloys and different casting speeds employed.

Ingots as large as 18 inches X 56 inches for the production of aluminium sheet have been produced by the use of moulds made in accordance with the invention. Various casting speeds and appropriate mould bows produced ingots with flat rolling faces.

Casting started with each of the mould side walls bowed out by 3/32 inch, and the bowing was progressively increased until a bow of 1 H16 inches per wall or 2% inches total bow was obtained for a casting speed of inches per minute.

An ingot of these dimensions, cast in a conventional mould at 5% inches per minute, would have a buttconvexity of approximately 1 inch per face.

Referring now to the accompanying drawings:

FIG. 1 is a part plan view of one form of mould constructed in accordance with the present invention;

FIG. 2 is a side view of the mould of FIG. 1;

FIG. 3 is a section on line D-D of FIG. 1;

FIG. 4 is a section on line EE of FIG. 1;

FIG. 5 is a section line on line FF of FIG. 1; and

FIG. 6 is a section of the side wall of a modified mould.

The mould of FIG. 1 comprises side wall members 101 and end wall members 102, formed of aluminium extruded sections welded together to form a rectangular structure. Each end wall member 102 is welded to a top support plate 103, which carries a water box 104 for the supply of coolant to the reverse face of the end wall member 102. A hose junction member 105 is secured on the underside of the support plate 103. The junction member has a downwardly extending inlet branch for connection by means of a flexible hose to a water supply system and three horizontally extending outlet branches.

Each side wall member 101 is provided with two clevises, consisting of upper and

lower plates

106 and 107. The clevises are arranged symmetrically on opposite sides of the mid-point of the side wall member 101 and are provided for connection by links to any appropriate form of screw jack or the like, through which the force for flexing the side walls of the mould is applied. Alternatively the bowing function may be performed by hydraulic means. Indeed many other mechanical, electro-mechanical and pneumatic devices suggest themselves for this purpose. Whatever expedient is adopted, it is preferred that the device for flexing the mould wall is automatically controlled so that the amount of bowing is kept in step with the rate at which the casting table is lowered.

As will be seen from FIGS. 2 and 5, the water box 104 receives water via a flexible hose from one branch of the junction member 105 and applies water to the rear surface of the mould wall member 102 via jets 108, which direct jets of water obliquely onto the mould wall through the water-filled space 109. A plate 110 is secured by bolts to the bottom of the water box to define a water emission slit 111 through which water is directed from the space onto the end surface of an ingot emerging downwardly from the mould:

As will be seen from FIGS. 3 and 5, the side wall members 101 and end wall members 102 are both formed from an extruded aluminium section. However it will be understood that the end members 102 could be formed from flat aluminium strip with almost equal convenience.

As will be seen from FIG. 3, the flexible side wall assembly of the mould is comprised of an extruded aluminium section to form the mould wall and extruded envelope and water conduit section 112, formed in a rather stiff grade of p.v.c.

The wall member 101 is shaped so that it may be flexed without substantial distortion, being of substantially equal stiffness at top and bottom edges. The extruded section is provided with an undercut nutreceiving groove 114 and a longitudinal aperture 115 which forms part of a continuous lubrication system. The surface of the extrusion is chamfered at 117.

The section 112 provides a tubular water conduit 118. A series of closely spaced apertures 119 are drilled in that part of the conduit 118 which faces the reverse face of the side wall member 101, but between its connection to the junction member 105 and the end of the side wall member 101 these apertures are omitted.

An angle-section upper envelope wall portion 120 of the p.v.c. extruded section 112 rests upon the abutment 116 and is secured by rivets 121 to the side wall member 101. The rivets 121 also serve to support a thin splash guard 122.

The section 112 has a lower envelope wall and lip portion 123, which co-operates with the surface 117 to provide a water emission slit 124, directed to the provision of sub-mould cooling in the conventional manner. The portion 123 is connected to the wall member 101 by a series of closely spaced studs 125, which screw into tubular nuts 126 trapped in groove 114.

The section 112 thus co-operates with the side wall member 101 to define a water jacket space 127, to which water is supplied from the water conduit 118 through jet apertures 119 and from which water is emitted for sub-mould cooling through the slit 124. The section 112 provides little interference with the flexing of the aluminium side wall of the mould and, with the mould wall, provides a water emission slit through which a substantially uniform sheet or curtain of water may be emitted for sub-mould cooling.

It will be seen from FIG. 4 that at the locality of the clevis the lip portion 123 is cut back to fit with the clevis plate 107, which is welded to the chamfered surface 117 on member 101. To compensate for this the clevis plate 107 is formed with a series of closely spaced apertures 130 for emission of sub-mould cooling water. An adjustable baffle 131 preferably is provided to co-operate with apertures 130.

In the modified mould illustrated in FIG. 6 the general construction of the mould end walls and associated water box is the same as in FIGS. 1 to 5. In this construction, however, the water supply conduit and the envelope for cooling the side wall and applying submould coolant are separate from one another.

The mould side wall member 201 is a simple aluminium strip having a chamfered edge 202. Support brackets 203 are secured at intervals to the rear face of the side wall member 201 and are provided to maintain a water conduit 204 spaced away from the mould side wall. The conduit 204 is a neoprene or like flexible material and is provided with nozzles 205 for directing water onto the side wall member 201. A flexible neoprene gasket 206 is wrapped around the conduit tube 204 to define a water space 207. At the top the envelope gasket 206 is clamped behind an aluminium strip 208, whilst the other edge of the gasket 206 is clamped between a pair of thin aluminium strips 209 and 210, which are secured to the side wall member 201 at widely spaced intervals by attachment members 211 to define a water emission slit 212. It will be apparent that the tube 204 acts as a support for the more flexible gasket 206.

It will be understood that the mould of the present invention may be employed with casting appratus which is otherwise of conventional construction. Thus the lower end of the mould is closed at the beginning of the casting operation by a stool cap, which in this instance is truly rectangular to correspond with the intitial shape of the mould cavity. As will be apparent from the foregoing explanation, the side walls of the mould are set to be substantially rectilinear at the beginning of the casting operation and are progressively bowed in accordance with the shrinkage characteristics of the metal being cast, as the casting speed is increased.

It will be appreciated that the supply of metal to the mould may be effected in any convenient way, i.e. via conventional float-controlled dip tube or other conventional metal feeding devices employed in the art to maintain a substantially constant metal head during the casting operation.

The supply of water to the cooling system is preferably provided with an on-of control mechanism in conjunction with an automatic timer to enable the supply of coolant to be pulsed on a short time cycle, such as 2 seconds, to control the rate of heat extraction from the ingot in the known way.

I claim:

1. Procedure for continuously casting a substantially rectangular-section metal ingot including the steps of a. supplying molten metal to the inlet end of a mould having an open outlet end and a substantially rectangular passage therethrough and maintaining a head of molten metal in said mould during said casting operation,

b. cooling the mould for solidifying the peripheral portion of the metal therein,

c. advancing the ingot through the mould at a relatively low initial speed and then increasing the rate of advance of the ingot through the mould,

d. applying coolant directly to the surface of the ingot emerging from said mould, and

e. increasing the gap at least between the mid-points of the opposed longer sides of the rectangular mould without substantial alteration of the gap between said sides at the ends thereof when the rate of advance of the ingot through the mould is increased above the relatively low initial speed,

wherein the improvement comprises maintaining a water filled zone in contact with the outer surface of the wall of the mould, and, at least along the long sides of said mould, directing jets of water into said water filled zone at closely spaced intervals towards said wall and towards the outlet end of said mould and emitting a substantially continuous curtain of water from the said water filled zone onto the surface of the ingot emerging from said mould.

2. Procedure according to claim 1 further including progressively increasing the curvature of the walls of the longer sides of said mould to increase the gap between the mid-points of said sides.

3. In apparatus for continuously casting a substantially rectangular section ingot in combination a. a rectangular mould adapted to receive and contain a supply of molten metal, said mould having an open outlet end and side walls formed of heat conductive metal,

b. means for initially closing the open outlet end of the mould and for progressively withdrawing an ingot from said mould at a controllably variable rate as the surface portion of said mould solidifies,

c. means for applying coolant liquid to the walls of the mould around its periphery,

d. means for applying coolant liquid direct to the surface of the emerging ingot at a position adjacent the outlet end of said mould, and

e. means for varying the curvature of at least the long side walls of said mould progressively during the performance of the casting operation,

wherein at least along the long sides of the mould a flexible envelope, formed ofa synthetic thermally resistant plastics material, is secured in sealed relation to the mould wall at the inlet end of the mould and is secured in spaced relation to the mould wall at the outlet end of the mouls so as to define a coolant receiving space in contact with the mould wall and having a substantially continuous coolant emission slit extending substantially along the full length of said long side at the outlet end of the mould, said flexible envelope being associated with a flexible tubular supply conduit formed of a synthetic thermally resistant plastics material, arranged to discharge jets of water at closely spaced intervals into said coolant receiving space.

4. Apparatus according to claim 3 in which each of the long side walls of the mould formed of essentially strip form flexible metal, associated with means for applying a flexing force thereto arranged symmetrically with regard to the mid-point of said side wall, the ends of the side walls being restrained from tranverse movement.

5. Apparatus according to claim 3 in which the short end walls are provided with cooling means independent of the means for cooling the long side walls.

6. Apparatus according to claim 3 in which the long side walls and the end walls of said mould are formed into a unitary structure so that flexure of the side walls results in movement of the mould end walls.

7. Apparatus according to claim 3 in which at least the long side walls of the mould are formed of an aluminium extruded section having an undercut groove therein adjacent the outlet end of the mould, said groove serving to receive and retain one part ofa series of spaced fixing means, said fixing means serving to secure the adjacent portion of the flexible envelope in spaced relation to the mould wall adjacent the outlet end of the mould.

8. Apparatus according to claim 3 in which said flexible envelope and said flexible water supply conduit are combined into a unitary extruded section.

9. Apparatus according to claim 8 in which said extruded section comprises a tubular water supply conduit portion, an angle-section upper wall envelope portion for securing in sealed relation with said mould wall and a lower envelope wall portion, terminating in an inclined lip portion for defining one side of said coolant emission slit. t

10. Apparatus according to claim 9 in which the tubular water supply section is formed with series of apertures therein directed towards the mould wall and inclined towards the outlet end thereof.

Claims

1. Procedure for continuously casting a substantially rectangular-section metal ingot including the steps of a. supplying molten metal to the inlet end of a mould having an open outlet end and a substantially rectangular passage therethrough and maintaining a head of molten metal in said mould during said casting operation, b. cooling the mould for solidifying the peripheral portion of the metal therein, c. advancing the ingot through the mould at a relatively low initial speed and then increasing the rate of advance of the ingot through the mould, d. applying coolant directly to the surface of the ingot emerging from said mould, and e. increasing the gap at least between the mid-points of the opposed longer sides of the rectangular mould without substantial alteration of the gap between said sides at the ends thereof when the rate of advance of the ingot through the mould is increased above the relatively low initial speed, wherein the improvement comprises maintaining a water filled zone in contact with the outer surface of the wall of the mould, and, at least along the long sides of said mould, directing jets of water into said water filled zone at closely spaced intervals towards said wall and towards the outlet end of said mould and emitting a substantially continuous curtain of water from the said water filled zone onto the surface of the ingot emerging from said mould.

3. In apparatus for continuously casting a substantially rectangular section ingot in combination a. a rectangular mould adapted to receive and contain a supply of molten metal, said mould having an open outlet end and side walls formed of heat conductive metal, b. means for initially closing the open outlet end of the mould and for progressively withdrawing an ingot from said mould at a controllably variable rate as the surface portion of said mould solidifies, c. means for applying coolant liquid to the walls of the mould around its periphery, d. means for applying coolant liquid direct to the surface of the emerging ingot at a position adjacent the outlet end of said mould, and e. means for varying the curvature of at least the long side walls of said mould progressively during the performance of the casting operation, wherein at least along the long sides of the mould a flexible envelope, formed of a synthetic thermally resistant plastics material, is secured in sealed relation to the mould wall at the inlet end of the mould and is secured in spaced relation to the mould wall at the outlet end of the mouls so as to define a coolant receiving space in contact with the mould wall and having a substantially continuous coolant emission slit extending substantially along the full length of said long side at the outlet end of the mould, said flexible envelope being associated with a flexible tubular supply conduit formed of a synthetic thermally resistant plastics material, arranged to discharge jets of water at closely spaced intervals into said coolant receiving space.

7. Apparatus according to claim 3 in which at least the long side walls of the mould are formed of an aluminium extruded section having an undercut groove therein adjacent the outlet end of the mould, said groove serving to receive and retain one part of a series of spaced fixing means, said fixing means serving to secure the adjacent portion of the flexible envelope in spaced relation to the mould wall adjacent the outlet end of the mould.

9. Apparatus according to claim 8 in which said extruded section comprises a tubular water supply conduit portion, an angle-section upper wall envelope portion for Securing in sealed relation with said mould wall and a lower envelope wall portion, terminating in an inclined lip portion for defining one side of said coolant emission slit.