US3283368A

US3283368A - Roller apron conveyor continuous casting machine

Info

Publication number: US3283368A
Application number: US354965A
Authority: US
Inventors: Paul J Homan
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1964-03-26
Filing date: 1964-03-26
Publication date: 1966-11-08
Anticipated expiration: 1983-11-08
Also published as: GB1058044A

Description

P. J. HOMAN Nov. 8, 1966 ROLLER APRON CONVEYOR CONTINUOUS CASTING MACHINE Filed March 26, 1964 5 Sheets-Sheet l INVENTOR. PAUL .1. HOMAM BY M M O O u Nov. 8, 1966 P. J. HOMAN 3,283,368

ROLLER APRON CONVEYOR CONTINUOUS CASTING MACHINE Filed March 26, 1964 5 Sheets-Sheet 2 FIG. 2

INVENTOR. PAUL J. HOMAN Nov. 8, 1966 P. J. HOMAN 3,283,368

ROLLER APRON CQNVEYQR CONTINUOUS CASTING MACHINE Filed March 26, 1964 5 Sheets-Sheet 3 INVEN TOR. PA UL J, HUM/1N BY bis United States Patent 3,283,368 ROLLER APRON CONVEYOR CONTINUOUS CASTING MACHINE Paul J. Homan, Pittsburgh, Pa., assignor to Koppers Company; Inc., a corporation of Delaware Filed Mar. 26, 1964, Ser. No. 354,965 9 Claims. (Cl. 2257.2)

This invention relates generally to the continuous casting of metal and, more particularly, to a method and apparatus for guiding the metal castings which are produced and for supporting their faces after they leave the mold.

The continuous casting of metal such as ferrous metals and alloys is a well-known process. In this process molten metal is flowed from a suitable refractory lined vessel through a nozzle in the bottom of the vessel to the open upper end of an upright fiowthrough casting mold. The outer skin of the metal solidifies in the mold to form a slab or strand, although the inside or core has not yet solidified. The partially solidified slab is continuously withdrawn from the open lower end of the casting mold by a withdrawal mechanism which guides and supports the slab.

This withdrawal mechanism must support the faces of the slab against the internal metallostatic forces which exist because the core of the slab remains molten for a considerable distance below the mold. The magnitude of these forces is determined by the head of molten metal contained in the slab, so the forces increase with the distance from the bottom of the mold. To support the faces of the slab so that the internal pressure of the molten metal does not rupture its newly solidified skin and cause a breakout of the molten metal, it has been customary to provide a series of large support rolls below the mold. Such rolls have been arranged on opposite sides of the slab so that their innermost portions are in contact with opposite faces of the slab.

The use of these large, heavy rolls has a number of serious disadvantages. The points of support afforded to the faces of the slab of necessity are widely spaced and a number of pairs of rolls are needed. This leads to the necessity of providing a slab support and guide means of such a height that it requires raising the mold and metal supply vessels to a point where the supplying of molten metal to the mold becomes inconvenient and hazardous as well as costly due to the additional construction expense required. Also, the cost of maintenance is high since it is difiicult to adequately cool the surface of the rolls in contact with the extremely hot slab so that the large expensive rolls must be periodically replaced.

The apparatus of the invention overcomes these difficulties as well as providing several additional advantages. It allows reductions in machine height up to 40 percent, as well as reductions in the amount of machinery required, power consumption and maintenance. The friction between the guide members and the slab is reduced which eliminates the disturbance of the newly formed metal skin by the guide members. It is extremely versatile while maintaining simplicity in design and operation.

In accordance with the invention, two roller aprons are provided for guiding and supporting the faces of the metal slab after it has left the mold. The first apron has a relatively short length and is located just below the mold. This first apron comprises a series of water cooled guide rolls spaced apart from each other and arranged in two groups such that the innermost portion of each group is in direct contact with opposite sides of the metal slab. The second roller apron is such longer than the first roller apron and is located below the first apron. This second roller apron comprises a pair of endless traveling chains of water cooled rollers riding on tracks located below the guide rolls of the first apron. The traveling chains are positioned so that they contact opposite faces of the metal slab such that the portion of the chains in contact with the slab travels in the direction of movement of the metal strand.

One group of guide rolls and the endless traveling chain on one side of the slab are fixed. The other endless traveling chain and corresponding guide rolls are movably mounted such that the distance between the innermost portion of the chains and groups of guide rolls can be varied to guide and support metal slabs of different thicknesses. Means for moving the movable section of the roller aprons is provided as well as a series of members linking the movable and fixed sections of the roller aprons such that a constant distance between the two sections is maintained during the casting of a metal slab of a given thickness. The endless traveling chains can be driven in order to control the rate of descent of the slab from the mold or they can be used merely as a guide means in combination with a pair of driven pinch rolls.

The portion of the conveyor apron in contact with the slab can either straight or it can have various curved configurations such as circular, elliptical, parabolic, hyperbolic, etc.

In accordance with this invention there is provided a method of casting an elongated metal strand comprising continuously pouring molten metal into a casting zone so as to form a metal strand, reciprocating the zone to free the strand from the zone, controlling the rate of descent of the strand from the zone, supporting opposite faces of the strand downstream of the zone with a plurality of substantially cylindrical, rotating surfaces which travel with the strand, and cooling the surfaces so as to present a fresh cooled surface to each line of contact with the strand.

The above and further objects and novel features of the invention will appear more fully from the detailed description when the same is read in conjunction with the accompanying drawings. It is to be expressly understood, however, that the drawings are not intended to be a definition of the invention but are for the purpose of illustration only.

FIGURE 1 is a vertical cross section of a side view showing an embodiment of the novel roller apron with parts broken away in combination with a conventional reciprocating flowtbrough casting mold, pinch rolls and bending and straightening rolls,

FIGURE 2 is a cross sectional View of FIGURE 1 taken along lines lIII,

FIGURE 3 is a vertical cross section showing an enlarged view of the roller apron connecting link and FIGURE 4 is a vertical cross section with parts broken away showing another embodiment of invention illustrated in FIGURE 1.

In the continuous casting of metals, such as ferrous metals and alloys, into an elongated metal slab or strand, molten metal continuously flows from a suiltable refractory lined vessel or tundish 11 through a nozzle 13 to the open upper end of an upright flowthrough casting mold 17. The outer portion or skin 18 of the metal solidifies in the mold to form the slab. However, the partially solidified slab retains its core in a molten state for a considerable distance below the open lower end of the casting mold. The slab is continuously withdrawn from the mold by a withdrawal mechanisrn. A suitable apparatus, such as a series of rollers, guides and supports the faces of the slab until the strand is completely solidified. The slab is then conveyed to a location Where it is cut into lengths by a suitable cutting device.

In the embodiment-of the invention as shown in FIG- 1, the molten metal 15 flows by gravity through nozzle 13 to the open upper end of mold -17 which is arranged to oscillate by conventional means (not shown) in a vertical direction. Metal 15 cools in mold :17 to form slab 19 which is freed from the mold by continuously oscillating the mold. A pair of driven pin-ch rolls 21 controls the descent of strand 19 from mold 17 Located directly below mold 17 is a roller apron 23 which is constructed in two

sections

24, 26 which are located on opposite sides of the path of travel of slab 19. Section 24 is rigidly attached to support 25 and section 26 is rigidly attached to support 28. Roller apron 23 con- I sists of a plurality of guide rolls 31 cooled by a water spray (not shown). Rolls 31 are spaced apart from each other and are in turn supported by rolls 20.- The innermost portion of each roll 31 is in direct contact with a face of slab 19 so that the rolls 31 provide support for the faces of slab 19 against the internal pressure exerted by the molten metal 15 to prevent rupture of the newly formed slab 19.

Located directly below roller apron 23 is roller apron 33 which is constructed in two

sections

32 and 34 which are located on opposite sides of the path of travel of slab 19. Here, the faces of slab 19 are contacted by a pair of endless traveling chains 35. The water cooled rollers 37 of each chain are connected by links 38 and ride on a plurality of closed curved tracks 39 and idling sprocket wheels 41. Section 32 is rigidly mounted toframe 29 by supports 43. Section 34 is movably mounted on frame 29 by means of wheels 47 which ride on tracks 49. Wheels 47 are attached to outrigger 50 which is connected to beam 68 of section 34. Section 34, to which section 26 of roller apron 23 is attached, is movably mounted so that the distance between the innermost portion of rolls 31 and rollers 37 can be varied to accommodate slabs of different thicknesses.

To keep

sections

32 and 34 rigidly positioned, adjustable links 51 are rotatably attached to section 34 by fixed pins 55 and to section 32 by removable pins 57. Links 51 contain a series of apertures 52, suitable for receiving removable pins 57, which are located so that the effective length of links 51 can be varied in one inch increments depending upon in which apertures removable pins 57 are placed. The inner link connecting means are provided with conventional take up bushings (not shown) so that minor adjustments which may be necessary due to slight changes in apron dimensions can be made. Hydraulic ram 59, pivotally mounted to support 60 attached to frame 29, operates by conventional means (not shown) through

links

61, 62 and pin 66 to move section 34 of apron 33 in a horizontal direction on tracks 49.

Rollers 37 provide numerous points of support for the faces of slab 19. The requirement for support increases as the distance from the bottom of mold 15 becomes greater despite. the fact that the skin of slab 19 is becoming thicker as the slab solidifies. This is because of the fact that the internal pressure at any point due to the molten metal greatly increases while the core remains liquid since the pressure is a function of the head of molten metal above that point. Once slab 19 has solidified the faces no longer require support and slab 19 can be subjected to external stresses. Pinch rolls 21 are lo-. cated below roller apron 33 and contact the solidified slab 19 and control its descent from the mold. Bending roll 63 located below pinch rolls 21 is arranged to bend slab 19 to a horizontal position where straightening rolls 64 of straightener 65 contact opposite faces of slab 19 and strai hten it in the horizontal position. This charge in the path of travel of the slab from vertical to horizontal reduces the height requirements of the casting apparatus.

Turning now to FIGURE 2, a horizontal cross section of the novel roller apron is illustrated taken through line 11-11 of FIGURE 1. Rollers 37 ride on tracks 39 which are supported by beams 67 and 68. A plurality of water nozzles 69 fed by pipes 71 are attached to beams 67 by supports 73 and positioned so as to direct a stream of water on the outer portion of rollers 37. Section 34 of roller apron 33 is adapted to move within frame 29 by means of wheels 47 riding on tracks 49. Links 51 are pivotably mounted to supports 75 by fixed pins 55 and links 51 are detachably'mounted to supports 77 by removable pins 57.

FIGURE 3 illustrates in detail construction of the means linking the two halves of roller apron 33. Link 51 is pivotably attached to support 75 of section 34 of roller apron 33 by fixed pin 55 secured by lock plate 56 and to support 77 of the section 32 of roller apron 33 by removable pin 57. Hydraulic cylinder 53 is attached to support 75 through support member 81 such that the upper portion of vertically movable rod 83 of cylinder 53 is positioned to contact link 51 at recess 85. provided in link 51.

Link 51 contains a series of apertures 52 adapted to receive movable pin 57. These apertures have their centers at one inch increments in the horizontal direction. When it is desired to vary the distance between the fixed and movable sections of roller apron 33 in order to guide a slab of ad itferent thickness, hydraulic cylinder 53 is actuated by conventional means not shown so that arm 83 contacts link 51 and supports its weight. Pin 57 is then removed from link 51 and support 77 thus disengaging the fixed and movable sections of roller apron 33. Hydraulic cylinder 59 (FIGURE 1) is then actuated by conventional .means not shown to move movable section 34 of roller apron 33 on track 49 until the innermost portions of rollers 37 on the corresponding sections of roller apron 33 are the desired distance apart. Cylinder 53 is again actuated to move link 51 by means of arm 83 either up or down so that the appropriate aperture in link 51 is moved to coincide with aperture 58 in support 77 so that movable pin 57 can be reinserted. 'This linkage device assures correct and rigid spacing between the rollers of the two halves of the roller aprons.

The thickness of the slab to be cast is varied by changing the dimensions of the moldcham ber which is employed. The mold is arranged so that one face of the slab being cast will contact the fixed side of roller, apron 33. The position of the movable portion of roller apron 33 is then changed by the above procedure so that it will contact the other face of the slab. The molten metal supply, pinch rolls, bending roll and straightening rolls are arranged so that they can be adjusted by conventional means not shown according to the size of the slab to be cast.

In operation, pins 57 in links 51 are removed from support 77 and section 34 of roller apron 33 is adjusted using hydraulic ram 59 to move section 34 so that the width between it and the fixed section 32 corresponds to the thickness of slab to be cast. Removable pins 57 are then reinserted in supports 77 to rigidly link the two

sections

32 and 34 of apron 33. This fixes the relative position of

sections

32 and 34 so that forces exerted on the rollers by the faces of. the slab do not spread the sections apart.

5. Molten metal 15 is flowed from tundish 11 through nozzle 13 to mold 17 where metal 15 solidifies to form sla'b 19. Initially the faces of slab 19 are supported by small water cooled guide rolls 31 of apron 23. As the distance from the mold increases and the metallostatic forces within slab 19 correspondingly increase, the faces of slab 19 are supported by roller apron 33 by means of the rollers 37 of endless chains 35 riding on tracks 39. The rate of descent of the slab 19 from the mold is controlled by pinch rolls 21 with endless chains 35 traveling in the direction of movement of the slab due to the frictional engagement of chains 35 between tracks 39 and slab 19, at one half the speed of slab 19. Slab 19, below pinch rolls 21, is bent to a horizontal position by bending roll 63 and straightened in the horizontal position by rolls 64 of straightener 65 after which it is removed to a suitable location and cut into lengths by a conventional cutting mechanism (not shown).

Since the rollers 37 are being continuously cooled by water sprays 69 while they are in rotating contact with slab 19, a fresh cool surface is being continuously presented to the face of slab 19. This results in excellent heat transfer away from the slab 19 to aid in the solidification of the slab. It additionally prevents the rollers from becoming overheated since a freshly cooled line of contact is continually being presented to the slab by each roller. There is no relative motion between the rollers and slab 19 where they are in contact so that forces due to friction are minimized and any significant distortion of the faces of slab 19 is avoided. This is in contrast to a support apron using a plurality of large fixed rolls. These large fixed rolls provide fewer and more widely spaced support points for the surfaces of the slab against the internal met-allostatic forces. The slab therefore has a tendency to bulge at the point above where it passes between each pair of rolls causing a damming effect to occur. This not only creates'additional friction between the rolls and the slab which increases the power requirements to remove the slab from the mold but it causes continuous distortions of the slab face to occur. These distortions produce cracks in the slab and may even cause rupture of the slab and breakout of molten metal. Since rollers 37 of the novel apron travel with slab 19, this damming effect with its resultant difiiculties cannot occur. Therefore, the invention provides a method for supporting the faces of a newly cast slab which results in a slab of better quality.

The foregoing embodiment has shown the novel apparatus used in conjunction with driven pinch r-olls 21 to control the descent of the slab. The descent of the slab can also be controlled by the continuous chains 35 of roller apron 33 if desired.

To this end, as shown in FIGURE 4, the novel apparatus may include driven sprocket wheels 81 at the lower end of roller apron 33 (only one side of which is shown for simplicity) to pull the chains 35 and consequently slab 19 in a downward direction at a controlled rate. The roller apron as thus driven eliminates the need for pinch rolls 21 and so reduces the height and power requirements of the apparatus further.

Apron 33 is illustrated herein as having a straight vertical configuration but can also be constructed in various curved configurations such as circle, parabola, hyperbola, etc. for use in conjunction with curved molds where a slab of metal 19 having the same curvature of the apron is produced or for use where the apron itself is employed as a bending means for slab 19. The use of these embodiments of the device, of course, allows a further reduction in machine height with its attendant economies.

The foregoing has described an apparatus for guiding, supporting and transporting a metal slab which is continuously being cast in a suitable mold. The device allows simplified construction whereby any failure of a 6 part can be quickly and inexpensively remedied by replacement. It also provides an apparatus whereby the faces of the metal slab can be eifectively supported against internal metallostaic forces while applying the minimum amount of stress on the newly formed skin of the slab. Various embodiments of the device allow a reduction in casting machine height up to 40 percent as well as reductions in the amount of machinery required, power consumption and maintenance. It is ver satile in that slabs of different thicknesses can be cast with assurance that the correct distance between the faces of the support members are accurately determined and maintained throughout the casting operations since the support members can be easily adjusted as a unit.

I claim:

1. In an apparatus for casting an elongated metal slab, in combination, a reciprocating mold Whose inner walls form a casting chamber, means for continuously pouring molten metal from a supply into said casting chamber so as to form a metal slab, means for controlling the rate of descent of said metal slab from said mold, means located downstream of said mold for guiding said metal slab said means comprising,

(a) a plurality of guide rolls spaced from each other and arranged in two groups such that the innermost portion of each group is in direct contact with opposite faces of said metal slab,

(1) means for cooling said guide rolls,

(b) a pair of endless traveling chains of rollers riding on a plurality of closed curver tracks located downstream of said guide rolls such that the innermost portions of said chains contact opposite faces of said metal slab such that said portions of said chains are caused to travel in the direction of movement of said metal slab,

(1) means for cooling guide rollers,

(c) one of said chains and one group of guide rolls being mounted on a stationary support and the other chain and group of guide rolls being mounted on a movable support such that said other chain and group of guide rolls can be moved as a unit to vary the distance between the innermost portions of said chains and said groups of guide rolls in order to guide and support the faces of metal slabs of different thicknesses,

(1) means for moving said movable support and (2) adjustable linking means for maintaining a constant distance between said chains and said groups of guide rolls during the casting of a metal slab of a given thickness.

2. The apparatus of claim 1 wherein said means for cooling said guide rolls and said means for cooling said rollers are a plurality of water sprays.

3. The apparatus of claim 1 wherein said means for controlling the rate of descent of said metal slab from said mold-is a pair of driven pinch rolls located below said chains which are adapted to contact opposite sides of said metal slab.

4. In an apparatus for casting an elongated metal slab, in combination, a reciprocating mold whose inner walls form a casting chamber, means for continuously pouring molten metal from a supply into said casting chamber so as to form a metal slab, means located downstream of said mold for guiding said metal slab and controlling the rate of descent of said slab from said mold said means comprising,

(1) means for cooling said guide rolls,

(b) a pair of endless traveling chains of rollers riding on a plurality of closed curved tracks located downstream of said guide rolls such that the innermost 71 portions of said chains contacts opposite faces of said metal slab,

(1) means for cooling said rollers,

(1) means for moving said movable support,

(2) adjustable linking means for maintaining a constant distance between said chains and said groups of guide rolls during the casting of a metal slab of a given thickness and (d) means for driving said chains to control the rate of descent of said slab from said mold.

5. The apparatus of claim 4 wherein said means for cooling said guide rolls and said means for cooling said rollers are a plurality of water sprays.

6. In an apparatus for casting an elongated metal slab, in combination, a reciprocating mold whose inner walls form a casting chamber, means for continuously pouring molten metal from a supply into said casting chamber so as to form a metal slab, a pair of driven pinch rolls for controlling the rate of descent of said metal slab from said mold, means located downstream of said mold for guiding said metal slab said means comprising,

(1) a plurality of water sprays for cooling said guide rolls,

(b) a pair of endless traveling chains of rollers riding on a plurality of closed curved tracks located downstream of said guide rolls such that the innermost portions of said chains contacts opposite faces of said metal slab such that said portions of said chains are caused to travel in the direction of movement of said metal slab,

(1) a plurality of water sprays for cooling said rollers,

(c) one of said chains and one group of guide rolls being mounted on a stationary support and the other chain and group of guide rolls being mounted on a movable support such that said other chain and group of guide rolls can be moved as a unit to vary the distance between the innermost portions of said chains and said groups of guide rolls in order to guide and support the faces of metal slabs ofdilferent thicknesses,

(1) a hydraulic ram adapted to move said movable support and (2) adjustable linking means for maintaining a constant distance between said chains. and said groups of guide rolls during the casting of a metal slab of a given thickness, said adjustable linking means comprising,

(a) a plurality of metal link pivotally attached on each side of the movable portion of said means for guiding said metal slab by fixed pins and detachably connected on each side of the fixed portion of said means for guiding said metal slab by removable p (1) said links each having a plurality of apertures adapted to receive said removable pins such that the effective length of said connecting links can be varied by placing said pins in different apertures,

(b) means to support said links: when said links are detached from said fixed portion and to position said links so that theremovable pins-can be reinserted to connect said links to said fixed portion.

7. In an apparatus for casting an elongated metal slab, in combination, a reciprocating mold whose inner walls form a casting chamber, means for continuously pouring molten metal from a supply into said casting chamber so as to form a metal slab, means for controlling the rate of descent of said metal slab from said mold, means located downstream of said mold for guiding said metal slab said means comprising, v

(a) a pair of endless traveling chains of rollersriding on a plurality of closed curved tracks such that the innermost portions of said chains contact opposite faces of said metal slab and said portions of said chains are caused to travel in the direction of movement of said metal slab,

(1) means for cooling said rollers, Y

(b) one of said chains being mounted on a stationary support and the, other chain being mounted on a movable support such that said other chain can be moved to vary the distancebetween the innermost portions of said chains in order to guide and support the faces of metal slabs of different thicknesses,

(1) means for moving said movable support and (2) adjustable linking means for maintaining a constant distance between said chains during the casting of a metal slab of a given thickness.

8. In an apparatus for casting an elongated, metal slab, in combination, a reciprocating mold whose inner walls form a casting chamber, means for continuously pouring molten ,metal from a supply into said casting chamber so as to form a metal slab, means located downstream of said mold for guiding said metal slab and controlling the rate of descent of said slab from said mold said means comprising,

(a) a pair of endless traveling chains of rollers riding on a plurality of closed curved tracks such that the innermost portions of said chains contacts opposite faces of said metal slab,

(1) a plurality of water sprays for cooling said rollers,

(b) one of said chains being mounted on a stationary support and the other chain being mounted on a movable support such that said other chain can be moved to vary the distance between the innermost portions of said chains in order to guide and support the faces of metal slabs of different thicknesses,

(1) a hydraulic ram adapted to move said movable support,

(2) adjustable linking means for maintaining .a constant distance between said chains during the casting of a metal slab of a given thickness, said adjustable linking means comprising (a) a plurality of metal links pivotally attached on each side of the movable portion of said means for guiding said metal slab by fixed pins and detachably connected on each side of the fixed portion of said means for guiding said metal slab by removable pins,

(1) said links each having a plurality of apertures, adapted to receive said removable pins such that the effective length of said connecting links can be varied by placing said pins'in different apertures,

(b) means to support said links when said links are detached from said fixed portion and to position said links so that the removable pins can be reinserted to connect said links to said fixed portion,

s,2s3,ses 9 10 (6) means for driving said chains to control the rate of References Cited by the Examiner 9 ficentofsiidsflab t d t 1 t d UNITED STATES PATENTS appara us or cas mg an e onga e me a 5 ran 2,284,503 5/1942 W11l1ams 2257.2 compnsmg means for continuously pouring molten metal 2,314,605 3/1943 Arnold 198 162 mto a casting mold so as to form a metal strand, means 5 f M t fr tr d fr 2,546,476 3/1951 Schefe 198162 or reciproca mg sa1 mo 0 ee sai s an om sai 3,199,143 8/1965 Ousley et a1 17 12 mold, means for controlling the rate of descent of said strand from said mold, means for supporting opposite FOREIGN PATENTS faces of said strand downstream of said mold with a plu- 10 732,115 6/1955 Great Britain.

rality of rollers which travel with said strand and means for cooling said rollers so as to present a fresh cooled SPENCER OVERHOLSER Pnmary Examiner surface to each line of contract with said strand. ANNEAR, Assistant Examiner'-

Claims

9. AN APPARATUS FOR CASTING AN ELONGATED METAL STRAND COMPRISING MEANS FOR CONTINUOUSLY POURING MOLTEN METAL INTO A CASTING MOLD SO AS TO FORM A METAL STRAND, MEANS FOR RECIPROCATING SAID MOLD TO FREE SAID STRAND FROM SAID MOLD, MEANS FOR CONTROLLING THE RATE OF DESCENT OF SAID STRAND FROM SAID MOLD, MEANS FOR SUPPORTING OPPOSITE FACES OF SAID STRAND DOWNSTREAM OF SAID MOLD WITH A PLURALITY OF ROLLERS WHICH TRAVEL WITH SAID STRAND AND MEANS FOR COOLING SAID ROLLERS SO AS TO PRESENT A FRESH COOLED SURFACE TO EACH LINE OF CONTRACT WITH SAID STRAND.