US3722576A

US3722576A - Method and apparatus for straightening continuous casting

Info

Publication number: US3722576A
Application number: US00171834A
Authority: US
Inventors: F Gallucci
Original assignee: Steel Corp
Current assignee: United States Steel Corp
Priority date: 1971-08-16
Filing date: 1971-08-16
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27
Also published as: FR2149474B1; ES405882A1; AU470229B2; PL84899B1; JPS4829628A; BE787511A; FR2149474A1; AT326850B; ATA706672A; RO59797A; AU4541472A; IT965110B; BR7205540D0; ZA725448B; NL7211201A; CA970521A; GB1407073A; DE2239966A1

Abstract

A method and apparatus for straightening castings formed in a continuous-casting operation. After a partially solidified casting emerges from a continuous-casting mold, it travels through bending rolls and a curved roll rack which change its direction of travel from vertical to horizontal, but the casting acquires a curved set and must thereafter be straightened. The straightening apparatus of the present invention includes lower and upper series of rolls closely confining a casting, yet avoiding excessive forces such as would damage the casting, which may still have a liquid core. The apparatus has a critical combination of driven and idler rolls of varying diameters, which afford the necessary mechanical strength at reaction points, yet maintain minimum spacing between rolls in each series and allow standardization of the drives for the driven rolls.

Description

United States Patent 1 1 Gallucci [54] METHOD AND APPARATUS FOR STRAIGHTENING CONTINUOUS OTHER PUBLICATIONS Journal of Metals, March 1968, TNIJ.S.P16.

1 1 Mar. 27,1973

Primary ExaminerR. Spencer Annear Attorney--Walter P. Wood [57] ABSTRACT A method and apparatus for straightening castings formed in a continuous-casting operation. After a partially solidified casting emerges from a continuouscasting mold, it travels through bending rolls and a curved roll rack which change its direction of travel from vertical to horizontal, but the casting acquires a curved set and must thereafter be straightened. The straightening apparatus of the present invention includes lower and upper series of rolls closely confining a casting, yet avoiding excessive forces such as would damage the casting, which may still have a liquid core. The apparatus has a critical combination of driven and idler rolls of varying diameters, which afford the necessary mechanical strength at reaction points, yet maintain minimum spacing between rolls in each series and allow standardization of the drives for the driven rolls.

8 Claims, 4 Drawing Figures ANGE/VT PATENTEnnARzmzs SHEET 1 BF 3 Pmmmmzmn SHEET 3 OF 3 FIG. 3

METHOD AND APPARATUS FOR STRAIGIITENING CONTINUOUS CASTING This invention relates to an improved method and apparatus for straightening castings formed in a continuous-casting operation.

In a conventional continuous-casting operation, liquid metal is poured through an open-ended watercooled vertically oscillating mold. A casting, which at this stage has only a relatively thin solidified skin and a liquid core, emerges continuously from the lower end of the mold. Immediately beneath the mold the casting travels through a series of guide rolls, usually idlers, where water is sprayed on its surface to effect further solidification. Next the casting passes through power driven pinch and bending rolls, and thence through a curved roll rack which changes its direction of travel from vertical to horizontal. The casting acquires a curved set as it is bent and must be straightened before it is cut to individual lengths.

In modern low-profile casting machines the casting commences to bend after traveling vertically only a very short distance from the mold, and it may still have a liquid core as it leaves the curved roll rack. As long as the core is liquid, the casting must be handled with great care to prevent damaging its skin and producing an unsatisfactory surface or even a break-out of liquid metal. Hence, when a curved casting with a liquid core is straightened, the casting must be closely confined without excessive force applied at any one location. Similar problems of course are encountered in operating curved-mold casting machines which form a casting with an initial curvature.

An object of the present invention is to provide an improved method and apparatus for straightening curved continuously formed castings in which the casting is closely confined both ahead of and beyond the point of tangency dividing its straight portion from its curved portion, and in which forces applied to the casting in a direction normal to its surface are distributed uniformly along the length of the casting.

A further object is to provide an improved straightening method and apparatus in which tensile forces on a continuously formed casting are minimal.

A further object is to provide an improved straightening method and apparatus which can handle continuously formed castings while the core remains liquid without damaging the casting.

A further object is to provide a straightening apparatus which embodies a combination of rolls of varying diameters to afford mechanical strength at reaction points, yet maintain close spacing of the rolls along the casting.

A further object is to provide a straightening apparatus which is readily assembled or dismantled for maintenance.

In the drawings:

FIG. 1 is a partly diagrammatic longitudinal sectional view of a continuous-casting machine equipped with a straightening apparatus constructed in accordance with my invention;

FIG. 2 is an approximately vertical section on line IIII of FIG. 1;

FIG. 3 is a vertical section on line IlIIII of FIG. 1;

and

FIG. 4 is a top plan view of the structure shown in FIG. 3.

FIG. 1 shows diagrammatically a conventional openended water-cooled mold l0 and the last set of rolls 12 of a curved roll rack of a continuous-casting machine. A partially solidified casting C is formed in the mold and emerges continuously from the lower end thereof. Subsequently the casting travels through the curved roll rack, which changes its direction of travel from vertical to horizontal. The casting has a curved set as it leaves the curved roll rack, and next it travels through my straightening apparatus 13. The casting machine of course includes the usual other parts, such as a drive for vertically oscillating the mold, a guide-roll rack and spray chamber beneath the mold, a pinch roll assembly, bending rolls, a starter bar, etc., which I have not shown since they are not involved in the present invention.

My straightening apparatus 13 includes a lower series of closely adjacent work rolls 15, 16, I7, l8, I9, 20, 21, 22, 23 and 24, and a cooperating upper series 150, 160, 17a, I80, 190, 200, 210, 220, 230, and 240. The two series of work rolls are spaced apart vertically and define a pass for confining the casting C. All ten rolls of the lower series are journaled on fixed axes. Some rolls of the upper series are journaled on fixed axes and some on vertically movable axes, as hereinafter explained. Some rolls are idlers and some driven, as also hereinafter explained.

The pairs of rolls 15-150, 16-160, and 17-170 lie ahead of the point of tangency, that is, where the casting C still is curved. The three lower rolls l5, l6 and 17 are idlers. The two upper rolls and 170 are driven and are vertically movable. The upper roll is an idler and is journaled on a fixed axis. The pair of rolls 18-180 define the point of tangency, that is, where the casting C first becomes straight. Roll 18 may be either an idler or driven and has an idler back-up roll 25 therebelow, as hereinafter explained. The pairs of rolls 19-190, 20-200, 21-210, 22-220, 23-230, and 24-240 lie beyond the point of tangency, that is, where the casting C already is straight. The six

lower rolls

19, 20, 21, 22, 23 and 24 are idlers. The three upper rolls 190, 210, and 230 are driven and are vertically movable. The three upper rolls 200, 220, and 240 are idlers and are journaled on fixed axes.

The three reaction points, where the force on the rolls is greatest, occur at rolls 160, 18 and 200. The

reaction roll 18 sustains the full downward thrust of the force required to straighten the casting. While roll 18 may be of relatively small diameter, it has a largediameter back-up roll 25 to afford the necessary mechanical strength. Each of the other two reaction rolls 16a and 200 sustains one-half the upward thrust of the force required to straighten the casting. Lacking back-up rolls, these rolls must be of sufficiently large diameter themselves to afford the necessary mechanical strength to sustain this force. The reaction rolls must of course be journaled on fixed axes. As a safety feature, I prefer that roll 220 be journaled on a fixed axis and of relatively large diameter, the same as the reaction rolls 160 and 200. As an example for straightening a 10-inch thick slab, roll 18 may have a diameter of only 15 inches, but its back-up roll 25 may have a diameter of 24 inches. Rolls 160, 200, and 220 may have diameters of 19 inches.

All the driven rolls a, 17a, 19a, 21a and 23a (and 18 if driven) desirably are of equal diameter, whereby they can have standardized drive means with interchangeable parts, yet rotate at equal peripheral speeds. The various rolls of both the upper and lower series should be as near one another as space permits to confine the casting C effectively and minimize the tendency of the casing to bulge. Each of the upper driven rolls has a large diameter roll 16a, a or 22a next to it on one or both sides, and hence must be of relatively small diameter not to interfere. Each of the

remaining idlers

15, 16, 17, 8a, 19, 20, 21, 22, 23, 24 and 24a may be of equal diameter, a little larger than the driven rolls. In the example, each driven roll may have a diameter of 15 inches, and each of the last-mentioned idlers a diameter of 16 inches. The diameter of the upper driven rolls determines the diameter of the reaction roll 18 if this roll is driven.

FIG. 2 shows my preferred construction of the pair of 20 work rolls 18-18a (lower roll 18 driven, upper roll 18a idler). The lower roll is a reaction roll and has the backup roll 25 therebelow, as already described. Opposite ends of the back-up roll are journaled in free and held bearings housed in chocks 28 and 28a, which rest on load cells 29, supported on base members 30. Transverse angle irons 31 are welded to the chocks 28 and 28a and extend therebetween to brace the structure. Opposite ends of the lower work roll 18 are journaled in free and held bearings housed in

chocks

32 and 32a immediately above chocks 28 and 28a. A drive shaft 33 for roll 18 is shown extending from the left end to a suitable drive means(not shown), although optionally roll 18 may be an idler. Opposed fixed side frames 34 extend upwardly from the base members 30. Opposite ends of the upper work roll 18a are journaled in free and held bearings housed in

chocks

35 and 35a, which are welded to a transverse beam 36 supported at the top of frames 34 and spanning the space therebetween. The end faces of the six chocks have keys 37 which are slidably received in keyways 38 formed in the inside faces of the side frames 34.

Chocks

35 and 35a are held in place with tapered keepers 39 removably received in openings in the side frames 34. Each

chock

35 and 35a rests on a series of shims 40, which I can take out or add to for the purpose of making minor adjustments in the vertical position of roll 18a. Preferably I pivot latch bars 41 to the upper edges of the side frames to hold the shims in place.

FIGS. 3 and 4 show my preferred construction of the pair of rolls 21-21a (lower roll 21 idler, upper roll 21a driven). The pairs of rolls l5-15a, 17-170, 19-19a and 2323a are similar, and I have not repeated the showing. Opposite ends of the lower roll 21 are journaled in free and held bearings housed in chocks 45 and 45a which rest on ledges 46 formed on opposite fixed side frames 47. I weld downwardly depending studs 48 to the undersides of the respective chocks 45 and 45a to attach the chocks to the ledges 46. Frames 47 have hand holes 49 to furnish access to the nuts on studs 48. Transverse angle irons 50 are welded to the chocks 45 and 45a and extend therebetween to brace the structure. Opposite ends of the upper roll 21a are journaled in free and held bearings housed in chocks 52 and 52a which I weld to the underside of a transverse vertically movable yoke 53. The end faces of the four chocks have keys 54 which are slidably received in keyways 55 formed in the inside faces of frames 47. The upper edges of frames 47 have notches 56 which receive the yoke 53 and portions of the chocks 52 and 52a. A drive shaft 57 for rolls 21a also extends through the notch 56 at the left to a suitable drive means (not shown).

Yoke 53 is formed of spaced apart plates 58 of inverted U-shape connected by separators 59 welded thereto (FIG. 4). The yoke spans the space across the top of the two side frames 47, and has depending legs 60 outside the frames. Double-acting fluid pressure cylinders 61 are anchored at their lower ends to the outside of the respective frames 47 and have vertically movable pistons and piston rods 62. I attach the upper ends of the piston rods to the legs 60 of the yoke with removable pins 63. Thus the cylinders and yoke control the positioning of the upper roll 21a, the chocks 52 and 52a of which can move up and down the keyways 55.

In the remaining combination not yet described, both the lower and upper rolls are idlers, as occurs with the pairs 16-16a, 20-2011, and 22-22a. The parts which support the

lower idlers

16, 20 and 22 preferably are of similar construction to the parts which support roll 21 shown in FIG. 3. The parts which support the upper idlers 16a, 20a, and 22a preferably are of similar construction to the parts which support roll 18a shown in FIG. 2. Hence I have not repeated the showing in another cross-section view, but in FIG. I I have designated these parts with the same reference numer'als as for

rolls

21 and 180.

I can readily dismantle the apparatus for maintenance. After removing the tapered keepers 39, I can use a crane to lift out beam 36, chocks 35 and 35a, and roll 18a as a unit. Thereafter I can lift out successively roll 18 and its

chocks

32 and 32a, and roll 25 and its chocks 28 and 28a. After removing the pins 63, I can use the crane to lift out roll 21a and its chocks 52 and 52a as a unit. Thereafter I can remove the nuts on studs 48 and lift out roll 21 and its chocks 45 and 45a. I follow similar procedures to lift out any of the other rolls.

From the foregoing description, it is seen that my invention affords a simple method and apparatus for straightening a continuous casting, which may have a liquid core even after the straightening operation. I select rolls of diameters to furnish the necessary mechanical strength at the points of maximum thrust yet afford standardization of the driven rolls and their drives, as well as close confinement of the casting. The lower and upper idlers define a pass of uniform thickness for the casting, while the upper driven rolls, which propel the casting through the apparatus, can yield in order to avoid damage to the casting and minimize tensile forces thereon. The load cells 29 are connected in a circuit (not shown) which affords a continuous measurement of the force on the reaction roll 18, and thus give an immediate indication whenever this force becomes out of line.

I claim:

1. In a continuous-casting operation in which a partially solidified casting emerges continuously from the lower end of a mold, travels through a curved roll rack which changes its direction of travel from vertical to horizontal, and wherein the casting has a curved set, a method of straightening said casting comprising:

passing said casting between lower and upper series of closely adjacent rolls, said series being spaced apart vertically and defining a pass for confining the casting;

contacting the bottom face of said casting at the point of tangency dividing the straight portion of said casting from its curved portion with one roll of said lower series, which roll sustains the downward thrust of the force required to straighten the casting',

contacting the top face of said casting on opposite sides of said point with two rolls of said upper series, each of which second named rolls is an idler spaced from said point and sustains half the upward thrust of the force required to straighten the casting;

contacting the top face of said casting opposite said first-named roll and the bottom face opposite said second-named rolls with idler rolls which define therewith a fixed pass;

contacting both the bottom and top faces of said casting in the spaces between said second-named rolls and said point with other rolls of said lower and upper series, which last-named upper rolls are driven and which last-named lower rolls are idlers; and

leaving said driven rolls of said upper series free to move vertically.

2. A straightening method as defined in claim 1 in which said casting has a liquid core at the point of tangency.

3. A straightening method as defined in claim 1 in which said first-named roll is driven.

4. A straightening method as defined in claim 1 in which said first-named roll is an idler.

5. In a continuous-casting machine which includes a mold adapted to form a partially solidified casting which emerges continuously from the lower end thereof, and a curved roll rack adapted to change the direction of travel of the casting from vertical to horizontal and wherein the casting has a curved set, the combination therewith of a straightening apparatus comprising:

lower and upper series of closely adjacent rolls, said series being spaced vertically and defining a pass for confining the casting;

one roll of said lower series being adapted to contact the bottom face of the casting at the point of tangency dividing the straight portion of the casting from its curved portion and to sustain the downward thrust of the force required to straighten the casting;

two rolls of said upper series being adapted to contact the top face of the casting on opposite sides of and spaced from said point, each of which secondnamed rolls is an idler and sustains half the upward thrust of the force required to straighten the castother rolls of said upper and lower series being opposite first and second-named rolls and being idlers and defining with said first and secondnamed rolls a fixed pass;

other rolls of both said series being located in the spaces between said first and second-named rolls,

said last-named other rolls includinghdriven upper rolls and idler lower rolls of which e lower rolls are journaled on fixed axes; and

means connected with said driven upper rolls for moving them vertically.

6. A straightening apparatus as defined in claim 5 in which the roll contacts the bottom face of the casting at the point of tangency is of relatively small diameter, said apparatus comprising in addition a relatively large diameter back-up roll for the relatively small diameter roll to enable the latter to sustain the downward thrust.

7. A straightening apparatus as defined in claim 5 in which the two rolls which sustain half the upward thrust are of relatively large diameter, and the rolls next to them are driven and of relatively small diameter.

8. A straightening apparatus as defined in claim 7 in which all said driven rolls are of the same diameter determined by the diameter which can fit next to said rolls of relatively large diameter.

Claims

1. In a continuous-casting operation in which a partially solidified casting emerges continuously from the lower end of a mold, travels through a curved roll rack which changes its direction of travel from vertical to horizontal, and wherein the casting has a curved set, a method of straightening said casting comprising: passing said casting between lower and upper series of closely adjacent rolls, said series being spaced apart vertically and defining a pass for confining the casting; contacting the bottom face of said casting at the point of tangency dividing the straight portion of said casting from its curved portion with one roll of said lower series, which roll sustains the downward thrust of the force required to straighten the casting; contacting the top face of said casting on opposite sides of said point with two rolls of said upper series, each of which second named rolls is an idler spaced from said point and sustains half the upward thrust oF the force required to straighten the casting; contacting the top face of said casting opposite said firstnamed roll and the bottom face opposite said second-named rolls with idler rolls which define therewith a fixed pass; contacting both the bottom and top faces of said casting in the spaces between said second-named rolls and said point with other rolls of said lower and upper series, which last-named upper rolls are driven and which last-named lower rolls are idlers; and leaving said driven rolls of said upper series free to move vertically.

5. In a continuous-casting machine which includes a mold adapted to form a partially solidified casting which emerges continuously from the lower end thereof, and a curved roll rack adapted to change the direction of travel of the casting from vertical to horizontal and wherein the casting has a curved set, the combination therewith of a straightening apparatus comprising: lower and upper series of closely adjacent rolls, said series being spaced vertically and defining a pass for confining the casting; one roll of said lower series being adapted to contact the bottom face of the casting at the point of tangency dividing the straight portion of the casting from its curved portion and to sustain the downward thrust of the force required to straighten the casting; two rolls of said upper series being adapted to contact the top face of the casting on opposite sides of and spaced from said point, each of which second-named rolls is an idler and sustains half the upward thrust of the force required to straighten the casting; other rolls of said upper and lower series being opposite first and second-named rolls and being idlers and defining with said first and second-named rolls a fixed pass; other rolls of both said series being located in the spaces between said first and second-named rolls, said last-named other rolls including driven upper rolls and idler lower rolls of which the lower rolls are journaled on fixed axes; and means connected with said driven upper rolls for moving them vertically.