US3199160A

US3199160A - Continuous casting of metal

Info

Publication number: US3199160A
Application number: US212416A
Authority: US
Inventors: James S Morton
Original assignee: United Engineering and Foundry Co
Current assignee: United Engineering and Foundry Co
Priority date: 1961-07-26
Filing date: 1962-07-25
Publication date: 1965-08-10
Anticipated expiration: 1982-08-10

Description

Aug. 10, 1965 J. 5. MORTON CONTINUOUS CASTING OF METAL 2 Sheets-Sheet 1 Filed July 25, 1962 INVENTOR JAMES SM ORTON N u 0 3 2 9 2 o o l L 2 o2 u O 2 I M 2.30... 030 3033 3333 9 E 3 3n uoeuaua co oa e ecu n n a a a l q M M. an CI I x a 2 2 H M 3 O O 1) FIG.

HlSATTORNEY 1965 J. s. MORTON 3,199,160

CONTINUOUS CASTING 0F METAL Filed July 25, 1952 2 Sheets-Sheet 2 I Is / INVENTOR JAMES S. MORTON Hts ATTORNEY United States Patent 3,19%,165 CIBNTEN'UQUS (IAfi'liNG Q1 METAL .lames S. Morton, Weybridge, England, assignor, by memo assignments, to United Engineering and Foundry Company, Pittsburgh, Pa, a corporation of Pennsylvania Filed .luly 25, 1962., Ser. No. 212,416 (Claims priority, application Great Britain, July 26, 196i, 27,147/61 5 (Ilainis. (6!. 22-572) This invention relates to the continuous casting of metal in a liquid-cooled mould, from the lower end of which a newly-formed ingot is withdrawn progressively in a continuous length by means of power-driven withdrawal rolls.

in the casting of steel and other high-melting-point metals, the newly-formed ingot emerging from the mould is only partially solidified, i.e. it has a solid skin but a molten centre. The ingot should be completely solidified by the time it reaches the withdrawal rolls, solidification taking place progressively during the passage of the ingot from t io mould to the Withdrawal rolls.

In order to accelerate the solidification of the ingot and to enable the vertical space between the withdrawal rolls and the mould, referred to as the secondary cooling zone, to be reduced, it is usual to spray the ingot with water during its passage through this zone. Very considerable amounts of heat are extracted in this way, with the production of large quantities of steam. A great part of this steam is recondensed by contact with the water sprays but it cannot all be eliminated in this way, and in order to-avoid unsatisfactory working conditions on the mould operating platform and poor working visibility around the mould, it has been proposed to enclose the secondary cooling zone as much as possible and to duct away the steam.

According to the present invention, in a process for the continuous casting of metal in an open-ended liquidcooled mould, a length of the newly formed metal ingot extending vertically below the mould is enclosed in a shroud spaced around the ingot, the shroud defining a secondary cooling zone within which the ingot is sprayed with cooling liquid, and a forced current of air is caused to flow continuously in the generally upward direction through the interior of the shroud to one or more exhaust apertures adjacent to the upper end.

Thus the shroud acts as a form of cooling tower, the forced air current which passes upwardly through it serving to remove steam from within the shroud, and to reduce the rise in temperature in the sprayed water due to rccondensation, and also to remove substantial quantities of heat from within the shroud by evaporating part of the spray water in the manner of a conventional cooling tower.

The velocity of flow of the forced air stream through the shroud should preierablc be in the range 200-500 feet per minute.

in one form of the invention the interior of the shroud is maintained at a sub-atmospheric pressure. For example, the forced air currrent may be induced to flow by means of an extraction fan or other suction device connected to the exhaust aperture or apertures of the shroud. The fan must be sufficiently powerful to maintain the required negative pressure within the shroud.

The shroud may be formed with one or more air inlets at its lower end, the air inl t or one of them being afforded by a narrow annular space surrounding the ingot between its surface and the lower edge of the shroud through the ingot extends downwardly. The escape of Water, which would otherwise run down the surface of the protruding ingot, is substantially reduced or prevented by the air stream drawn in or blown in through the annular gap, possibly aided by water shedder plates or by a ring of steam or air jets directed upwardly around the ingot at the point of exit from the shroud.

In one arrangement the shroud is provided with one or more air inlets at its upper end through which air will be drawn into the shroud by the sub-atmospheric pressure therein, so as to ventilate the region around and above the upper end of the shroud.

Alternatively instead of maintaining the interior of the shroud at a sub-atmospheric pressure and inducing the forced air-stream to flow by means of suction means associated with the exhaust aperture, the forced air stream may be produced in the shroud by blowing air into the lower part of the shroud. For this purpose the jets of compressed air referred to above at the lower part of the shroud may in some cases be relied on alone, although it will usually be desirable to provide one or more additional air inlets in the lower part of the shroud and to blow air under low pressure into the shroud through these inlets, for example by means of low-pressure fans.

According to another of its aspects the invention comprises apparatus for the continuous casting of metal which includes an open-ended liquid-cooled mould beneath which is mounted an elongated shroud positioned to surround a length of the newly-formed ingot depending vertically from the mould, the ingot extending out through the bottom of the shroud, and the side walls of the shroud being spaced from the surfaces of the ingot to deline a secondary cooling zone, spray means for spraying the length of ingot in the secondary cooling zone within the shroud with cooling liquid, and means for forcing a continuous current of air to flow in the generally no ward direction through the interior of the shroud to one or more exhaust apertures situated adjacent to the upper end of the shroud.

According to a further feature of the present invention, the sides of the water-cooled mould may be surrounded by a mould chamber whose interior communicates with the interior of the shroud, and means may be provided for maintaining the interior of the mould chamber at an air pressure greater than the pressure in the interior of the shroud. This mould chamber may contain equipment such as mechanism for vertically reciprocating the mould, and since its interior is maintained at a greater pressure than that in the shroud with which it communicates, steam from the interior of the shroud will be prevented from passing into the mould chamber where it might damage the equipment referred to,

Moreover, the interior of the mould chamber will normally be maintained at a super-atmospheric pressure by the continuous supply to it of compressed air, so that smoke and fumes produced above the mould by the casting operation will be prevented from being drawn into the mould chamber through any clearance between it and the reciprocating mould.

In one such arrangement a common supply of compressed air is connected both to the mould chamber and to a gas burner for heating a tundish associated with the mould, and valve means is provided whereby compressed air may be delivered from the supply either simultaneously to the burner as combustion air and to the mould chamber, or solely to the mould chamber when the burner is not required to preheat the tundish.

The invention may be carried into practice in various ways, but two specific embodiments will now be described by way of example only with reference to the accompanying drawings, wherein:

FIGURE 1 is a diagrammatic sectional elevation of a part of a continuous casting plant for steel, and

FIGURE 2 is a similar view of a modified form of plant.

In the embodiment of FIGURE 1, a continuous casting plant for the casting of steel is provided with a verticallyreciprocable open-ended liquid-cooled mould in a surrounding mould chamber 11, liquid metal being poured as required from a tundish into the open upper end 12 of the mould, and the cast metal ingot 13 being with drawn in a continuous length from the open lower end of the mould by means of power-driven withdrawal rolls 14 spaced vertically below the mould. A tubular metal shroud 15 of rectangular cross-section is mounted immediately below the mould 10 and surrounds and encloses a length of the ingot between the lower end of the mould 1i) and the uppermost withdrawal roll 14. The side wallof the shroud 15 is spaced from the surface of the newly formed ingot 13 which is guided as it descends through the shroud by means of trains of guide rolls 16 mounted within the shroud. The shroud thus defines a secondary cooling zone for the ingot, and also mounted within the shroud 15 are spray nozzles (not shown in the drawing) by means of which sprays of cooling water are directed from all sides at the surface of the ingot 13 within the shroud to cool it. I

Near its upper end the shroud 15 is formed with an exhaust aperture 18 connected by an exhaust duct 19 to a powerful extractor fan (not shown). The top of the shroud 15 is afforded by a top wall 20 which closely surrounds the ingot 15 as it emerges from the open lower end of the mould 10, leaving a narrow annular air gap 21 between the inner edge of the top wall 20 of the shroud and the surface of the ingot, through which air a gap air is drawn into the interior of the shroud as indicated by the arrows 22, thereby ventilating the region of the mould 1t) and mould chamber 11 to withdraw smoke and fumes therefrom.

The bottom wall 23 of the shroud 15 extends inwardly towards the ingot 13, and at its inner edge 24 carries an upstanding flange 25 defining a duct whose section is slightly larger than that of the ingot 13, so that an annular gap 26 is formed around the ingot 13 between its surface and the flange 25. At its upper end the flange 25 carries an inturned perforated rim or spider 23 through which the air gap 26 communicates with the interior of the shroud 15. Additional air inlets 29 are formed in the shroud near its lower end, and are preferably of adjustable area.

The extractor fan connected to the exhaust duct 19 is sumciently powerful to maintain the interior of the shroud 15 at an appreciable sub-atmospheric pressure, and the action of the fan induces a forced air stream to flow in the generally upward direction through the interior of the shroud from the

inlets

26 and 29 at its lower end to the exhaust aperture 18. This forced air current not only carries away with it through the exhaust aperture 18 steam produced within the shroud by the impact of the cooling water of the heated ingot, but it also cools the sprays of cooling water and extracts a further substantial quantity of heat by evaporation of the cooling sprays in the manner of a conventional cooling tower, as referred to above. The air stream drawn vertically upwardly through the space 26 between the flange 25 at the bottom of the shroud and the surface of the emerging ingot scours the ingot surface as it leaves the shroud, and thus helps to prevent the escape of water from the shroud through the aperture 26. This effect is aided by the provision of water shedder plates (not shown) and/ or by a ring of compressed air or steam jets (not shown) positioned around the ingot and directed upwardly along its surface to throw water'upwardly ofi its surface. The additional adjustable air gaps 29 near the bottom of the shroud ensure that a suificient volume of air is induced to flow upwardly through the shroud to produce the re quired cooling tower effect. The annular air inlet 21 at the top of the shroud serves to ventilate the region tion of the extractor fan must be sufficient to cause a sufficient velocity of flow of the forced air stream through the shroud, for example a velocity of between 200 and 500 feet per minute. It is desirable however that the velocity of the forced airstream should not greatly exceed the later value or a substantial quantity of water droplets will be entrained in the air stream and removed from the shroud as well as the steam. On the other hand speeds as low as 150 feet per minute may provide a useful cooling tower effect.

It will be appreciated that by virtue of the extraction through the duct 19 of the steam produced in the interior of the shroud 15, and by the act-ion of the auxiliary air inlet 21 at the top of the shroud, steam is prevented from escaping even in relatively small quantities to the region in the vicinity of the mould itself. If the ventilating action of the annular inlet 21 is insuflicient, the

' top wall 29 of the shroud might be formed with one or more additional inlet apertures, preferably of adjustable area;

In the modified embodiment illustrated in FEGURE 2, similar parts are given the same reference numerals. In this case however the interior of the shroud 15 is not maintained at a sub-atmospheric pressure, but the forced upright draught of air through the interior of the shroud is produced by blowing air under pressure into the lower part of the shroud through the inlets 29, and/ or by means of the water-shedding air or steam jets which are indicated at 30. The forced airstream escapes through the exhaustport 18 near the upper end of the shroud 15 and through the exhaust duct 19, which may if desired be connected to a low-powered extractor fan to assist the discharge from the duct 19. Alternatively the duct 19 may discharge straight to atmosphere. As before, the passage of the forced air draught upwardly through the shroud 15 to the exhaust port 18 producesa cooling tower effect and carries off the steam produced by the evaporation of cooling liquid sprayed on to the ingot within the shroud. The flow velocity of the forced draught should be 200-500 ft./min.

The mould chamber 11 which surrounnds the walls of the vertically-reciprocable mould 1t and which houses ancillary apparatu including the equipment for oscillating the mould vertically, is covered by a cover plate 32 which surrounds the open top of the mould and is separated from the rim of the mould by a small annular gap 33. A tundish 3d incorporating a gas or oil burner is mounted above the mould ill in line with its open upper end, and molten steel is poured from a ladle into the tundish 34 for casting in the mould. The bottom of the mould chamber 11 is closed by a partition 35 formed with an aperture whose rim closely surrounds the lower end of the mould 16 leaving a narrow annular gap 36.

Air under pressure is supplied to the mould chamber from a source S through a port 37 in the side of the mould chamber, and the compressed air is driven through over since the pressure within the mould chamber 11 is around and above the mould, acting as a suction nozzle withdrawn.

maintained by the introduction of the compressed air at a greater value than the pressure within the shroud 15, any flow of steam from the shroud into the mould chambet, and any resultant damage thereby to the equipment in the mould chamber, are prevented. Louvres 38 are provided in the side of the mould chamber 11 so that a part of the compressed air may be directed out of the mould chamber for the benefit of the operators. In addition, some air will escape through the small gap 33 between the topof the mould 1t and the cover plate 32, which gap 33-permits the vertical oscillation of the mould.

Thus smoke and fumes produced in the casting operation, which arise almost entirely in the mould or from the stream of metal being poured from the tundish to the mould, are prevented from entering the mould chamber by the pressure differential. Any smoke which might arise inside the mould chamber and might be detrimental to the operation of the equipment in the mould chamber, is carried by the air stream into the interior of the shroud 15 and thence to the exhaust port 18, or is discharged through the upper gap 33 and louvr-es 38.

The air supply from the source S to the mould chamer 11 is passed through a main air pipe 39 and a branch pipe 41} fitted with a stop valve 4-1. A second branch pipe 42 leads off the main pipe 39 and is connected via a second stop valve 43 to the gas burner incorporated in the tundish 34. Thus compressed air from the source S can also be supplied as combustion air to the burner in the tundish, to enable the latter to be preheated by the burner at the same time as the mould chamber is receiving compressed air from the same source. When the tundish is not required to be heated by the burner, the air supply to the burner is shut ofi by means of the stop valve 43 when the total supply of air from the source S will be delivered to the mould chamber 11.

In accordance with the provisions of the patent statutes, I have explained the principle and operation of my invention and have illustrated .and described what I consider to represent the best embodiment thereof. However, I desire to have it understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

What I claim is:

1. In a process for the continuous casting of metal workpieces in an open-ended mould, in which a length of a newly formed casting extending below the mould is enclosed in a shroud spaced around the casting, the steps comprising causing the casting to pass through the shroud and away from the mould, spraying the casting with a coolant during at least a portion of its passage through the shroud, and at the same time causing a forced current of air to flow continuously through the interior of the shroud to remove steam and heat within the shroud and reduce the temperature or" the coolant within the shroud, and causing a stream of air to be directed around the casting at a point substantially where the casting enters the shroud to ventilate the region around and above the upper end of the shroud.

2. In a process according to claim 1 wherein the mould is surrounded by a mould chamber and the interior of the :mould chamber communicates with the interior of the shroud, including the additional step of causing the mould chamber to be maintained at an air pressure greater than the pressure in the interior of the shroud.

3. Apparatus for the continuous casting of metal, which comprises an open-ended mould, an elongated shroud mounted beneath the mould positioned to surround a length of the newly formed casting depending from the mould in which the casting extends out through the bottom of the shroud, said shroud comprising side Walls spaced from the surfaces of the casting to define a secondary cooling zone, spray means for spraying the length of the casting in the secondary cooling zone within the shroud with cooling liquid, means for forcing a continuous current of air to flow through the interior of the shroud, an exhaust aperture situated adjacent to one end of the shroud to receive the air, a mould chamber surrounding the sides of the mould and communicating with the interior of the shroud, and means for maintaining the interior of the mould chamber at an air pressure greater than the pressure in the interior of the shroud.

4. Apparatus as claimed in claim3 in which the said means for maintaining the interior of said mould chamher at the specified pressure comprises means for admitting a continuous flow of compressed air into the interior of the mould chamber.

5. Apparatus as claimed in claim 4 including a common supply of compressed air connected both to the mould chamber and to a heating burner for heating a tundish associated with the mould, and valve means for delivering compressed air from the supply either simultaneously to the burner as combustion air and to the mould chamber, or solely to the mould chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,424,640 7/47 Spooner 2257.2 2,709,284 5/55 Evans 22-2001 2,871,530 2/59 Wie'land 22-57.2 2,907,082 10/59 Pond 22-572 FOREIGN PATENTS 816,290 10/ 5 1 Germany. 8 14,410 6/59 Great Britain.

WILLIAM J. STEPHENSON, Primary Examiner.

WINSTON A. DOUGLAS, MARCUS U. LYONS,

Examiners.

Claims

3. APPARATUS FOR THE CONTINUOUS CASTING OF METAL, WHICH COMPRISES AN OPEN-ENDED MOULD, AN ELONGATED SHROUD MOUNTED BENEATH THE MOULD POSITIONED TO SURROUND A LENGTH OF THE NEWLY FORMED CASTING DEPENDING FROM THE MOULD IN WHICH THE CASTING EXTEND OUT THROUGH THE BOTTOM OF THE SHROUD, SAID SHROUD COMPRISING SIDE WALLS SPACED FROM THE SURFACES OF THE CASTING TO DEFINE A SECONDARY COOLING ZONE, SPRAY MEANS FOR SPRAYING THE LENGTH OF THE CASTING IN THE SECONDARY COOLING ZONE WITHIN THE SHROUD WITH COOLING LIQUID, MEANS FOR FORCING A CONTINUOUS CURRENT OF AIR TO FLOW THROUGH THE INTERIOR OF THE SHROUD, AN EXHAUST APERTURE SITUATED ADJACENT OF THE END OF THE SHROUD TO RECEIVE THE AIR, A MOULD CHAMBER SURROUNDING THE SIDES OF THE MOULD AND COMMUNICATING WITH THE INTERIOR OF THE SHROUD, AND MEANS FOR MAINTAINING THE INTERIOR OF THE MOULD CHAMBER AT AN AIR PRESSURE GREATER THAN THE PRESSURE IN THE INTERIOR OF THE SHROUD.