US3446270A

US3446270A - Apparatus for continuous casting

Info

Publication number: US3446270A
Application number: US548743A
Authority: US
Inventors: Anatol Michelson
Original assignee: EW Bliss Co Inc
Current assignee: EW Bliss Co Inc
Priority date: 1966-05-09
Filing date: 1966-05-09
Publication date: 1969-05-27
Anticipated expiration: 1986-05-27
Also published as: DE1558178A1

Description

y 1969 A. MICHELSON 3,446,270

APPARATUS FOR CONTINUOUS CASTING Filed May 9, 1966 Sheet of 2 Fig. I

IN VE NTOR fiWATOL M/CHELSON ATTORNEYS May 27, 1969 A. MICHELSON APPARATUS FOR CONTINUOUS CASTING Sheet f- Filed May 9, 1966 Fig. 4

F lg. 3

g INVENTOR I ANATOL M/cueLso/v ATTORNEYS United States Patent 3,446,270 APPARATUS FOR CONTINUOUS CASTING Anatol Michelson, Glenolden, Pa., assignor to E. W. Bliss Company, Canton, Ohio, a corporation of Delaware Filed May 9, 1966, Ser. No. 548,743 Int. Cl. B22d 11/12 US. Cl. 164-282 3 Claims ABSTRACT OF THE DISCLOSURE This invention pertains to the metal castings art and more particularly to the casting of continuous rounds, squares, ovals or slabs hereinafter referred to generally as ingots.

Casting is accomplished in a vertical, flow-through mold which may be either stationary or reciprocating and is usually water cooled. Inasmuch as the ingot emerges from the mold only partly solidified, it will normally have a liquid center of substantial depth contained Within a solid outer skin. Therefore it is necessary for the mold to be located at a considerable height to allow for sufficient secondary cooling, usually in the form of a water spray, in order to complete the solidification process. To reduce the height of the casting plant, the ingot is customarily bent from the vertical casting position through an arc and subsequently straightened in a horizontal position before being cut into prescribed billet lengths. Nevertheless the pouring rate, size of the ingot, metallurgical properties of the metal and other factors influence the permissible rate of secondary cooling and to a large extent limit the reduction in height of the casing plant due to the fact that the ingot which has a deep liquid center must be allowed a longer vertical pass before complete solidification is reached and withdrawal and bending can commence.

Heretofore, withdrawal and bending of the ingot has taken place in a series of rolls located at or near the point of complete solidification. Attempts to decrease the casting height by moving the rolls closer to the mold have generally been unsuccessful primarily due to the fact that the huge withdrawal and bending forces then are applied to the still soft and weak skin of the ingot by the cylindrical rolls which have a very high contact pressure on a tiny strip-like area of the ingot skin often causing a rise in internal and surface cracks. This causing of defects in the ingot by a very high specific pressure of cylindrical withdrawal and bending rolls is a major problem arising from the application of such rolls in continuous casting machines.

Another problem arising from the bending and withdrawal rolls being placed at or below the point of complete solidification is that the straightening rolls must then be located at a point where the ingot is essentially below solidification temperature which necessitates increased straightening forces and causes higher stresses in the ingot which also can lead to surface cracks.

Moreover, the distance between the mold and the bending and withdrawal rolls determines the length of start- 3,446,270 Patented May 27, 1969 ing mechanism required. The starting mechanism is usually a long chain-like device with a bar on the end which is fed by the withdrawal rolls up into the mold at the beginning of a casting run and is used initially to provide a bottom in the mold and to withdraw the ingot. As a consequence of a larger starting mechanism, more expensive and heavier handling and storage equipment is required.

In overcoming these and other disadvantages of the prior art the present invention contemplates a method and apparatus employing a continuous application of a distributed withdrawal and bending force to a relatively large surface area of the ingot which permits commencing the withdrawal and bending closer to the mold where the ingot still has essentially a liquid core.

In accordance with the invention, a withdrawal and bending device travels continuously with the ingot and defines a curvilinear path through which the ingot is bent including a contacting member which occupies a relatively large surface area of the ingot relative to its cross sectional area so as to exert a rather low pressure on the partially solidified ingot.

Further in accordance with the invention, the bending and withdrawal device comprises at least two endless conveyors between which the ingot passes, each carrying a contacting member each of which has a common radius point.

In a further development of the invention, a method is provided of continuous casting which involves the steps of cooling the ingot as it emerges from the mold so as to develop a solidified skin of sufiicient thickness to withstand a predetermined unit pressure and Withdrawing the ingot from the mold and simultaneously bending it along a curvilinear path by the continuous application of a withdrawal and bending force moving with the ingot and applied over a relatively large surface area of the skin.

Further in accordance with the inventive method, secondary cooling of the ingot is carried out in two stages, the first stage including spray cooling between the mold and the application of the bending and withdrawal force of sufiicient duration to develop an ingot skin of predetermined thickness and a second stage comprising spray cooling to complete solidification prior to the curved ingot being straightened.

In another aspect of the invention, because the starting mechanism must go through both straight and curved paths, it is made of a number of rolls whose diameter is equal to the minimum thickness of ingot to be cast.

The principal object of the invention is to reduced drastically a high specific pressure exerted on the ingot by prior art withdrawal, as well as bending rolls in order to avoid various defects on and under the ingots surface caused by such pressure.

Another object of the invention is to reduce the overall height of the continuous casting plant and more particularly to permit the installation of continuous casting machines in existing plant facilities as a result of the reduction in casting height.

Another object of the invention is to start the applica tion of ingot withdrawal and bending forces closer to the mold thereby substantially reducing the vertical cooling height.

Another object is to shorten the distance between the mold and the withdrawal and bending device which permits the use of a shorter starting mechanism with the further advantage of decreasing the size of the handling and storage equipment therefor.

Another object is the provision of a new and improved starting mechanism.

Still another object or advantage of the invention arising from the placement of the withdrawal and bending device closer to the mold is that the ingot is bent while its temperature is above or near the complete solidification point permitting the straightening mechanism to be moved closer to the mold at a spot where the ingot, though solidified, has a higher temperature thus decreasing the straightening forces and the consequent stresses developed in the ingot from this operation.

These and other objects will become apparent by referring to the following description and drawings wherein:

FIGURE 1 is .a front elevational view of a casting machine employing a withdrawal and bending device constructed in accordance with the preferred embodiment of the invention;

FIGURE 2 is a partial view of the casting machine in FIGURE 1 showing the withdrawal and bending device in greater detail,

FIGURE 3 is a side elevational view of the withdrawal and bending device taken along line 3-3 of FIGURE 2; and

FIGURE 4 is a horizontal sectional view of the withdrawal and bending device taken along line 4-4 of FIGURE 2.

Referring now to the drawings wherein the figures are for the purpose of illustrating the preferred embodiment of the invention only and not for the purpose of limiting the same, in FIGURE 1 a casting machine is shown generally including a flowthrough, water cooled mold 12 positioned on a pouring floor 14 and elevated above a cooling chamber 16, a withdrawal and bending device 17, a cooling chamber 18 and a roll straightener 20. A starting mechanism 22 is shown, for purpose of illustration, in its two essential positions; firstly, with the bar 23 positioned in the mold 12 atthe start of a run and; secondly, with the bar stored in the handling and storage equipment 24 after the ingot I is withdrawn and the machine 10 is operating on a continuous basis. The starting mechanism 22 comprises a number of rolls R having a diameter equal to the minimum thickness of ingot I to be cast which are connected together by at least two links L, one on each side, the width of which is less than the diameter of the rolls R. Continuous operation involves the shuttling back and forth on rails 25 of bottom pour ladles 26, one of which is shown in pouring position over a tundish 27. The flow of molten metal from the ladle 26 to the mold 12 is regulated in a known manner by the stopper of tundish 27 in accordance with a prescribed casting rate.

In accordance with the invention, the casting machine 10 is characterized by a two-stage secondary cooling arrangement in which the first stage is cooling chamber 16 and the second stage is primarily cooling chamber 18 but also may include spray cooling within the withdrawal and bending device 17. Initial cooling is performed within the mold 12 by water circulation in the mold walls. The cooling arrangement is distinguished in that the chamber 16 is considerably reduced in size from the known prior art since, in the invention, the purpose of chamber 16 is not complete solidification of the ingot I, but only the formation of a crust or skin I (FIGURE 2) of sufficient thickness greater than that developed in the mold 12 to withstand the withdrawal and bending pressures of the device 17 as will be described more fully hereinafter. The first stage cooling chamber 16 is essentially similar to the second stage cooling chamber 18 in that each employs

support rolls

28, 29 for guiding the ingot I. Water spray jets 30, 31 connected to a water circulatory system and heat exchanger (not shown) are interspersed between

rolls

28, 29. The cooling chamber 18 includes a sliding door 33 which seals an opening therein of sufiicient size to accommodate the pivoted arm 35 of the starting chain storage and handling mechanism 24. The length of the starting chain 22 is somewhat greater than the distance between the middle of the mold 12 and the middle of the 'withdrawal and bending device 17 or the distance between the withdrawal and bending device 17 and a drive spider 36. During continuous casting, the arm 35 remains in the position shown in FIGURE 1 outside of the cooling chamber 18. At the beginning of a casting run, however, the door 33 is opened and the arm 35 lowered to the dotted line position by means of an actuating cylinder 38. The starting chain 22 is moved to and from the mold 12 by means of the spider 36 and the withdrawal and bending device 17 along longitudinal guides 39 positioned at each side of the ingot path.

Referring now to FIGURES 24, the withdrawal and bending device 17 is housed in a spray box 40 within whichwater jets (not shown) may be directed for cooling if necessary. In the preferred embodiment of the invention, a frame 41 supports a pair of

endless conveyors

42, 43 on opposite sides of the ingot I, each being driven continuously with the ingot so that there is no relative movement. To the extent the

conveyors

42, 43 contain essentially duplicate parts, those parts .are identified by like numerals where applicable, however, to the

extent conveyors

42, 43 differ but contain similar parts, like numerals will be used in identifying such parts with the addition of a prime mark with respect to conveyor 43. Each

conveyor

42, 43 is made up of a number of links 44 joined together by .a plurality of contact members or

pressure shoes

45, 45 by means of connecting pins 46, each carrying a roller 47 at the center and rollers 49 on the opposite ends. Upper and

lower conveyor drives

50, 52 each have axially spaced sprocket elements which engage the pin roller 49 for driving the

conveyors

42, 43, each of which has a separate, but synchronized drive 53.

Conveyors

42, 43 each include a track section 54, 54' upon which the central rollers 47 of each

pressure shoe

45, 45 ride. Track section 54 has a convex curvature and in cooperation with a concave portion a of track section 54' defines a segment of a circle having a predetermined radius the length of which depends largely on the cross sectional area of the ingot I and the grade of steel being cast. Generally the length of radius R will be about 25 times the thickness of the ingot I. An upper portion b of track section 54' which extends vertically above the top of track section 54 has a flat surface which serves to take the consequential bending forces as the ingot I enters the curved pathway. Therefore, the forces created in bending the ingot I are transmitted directly to the frame 40 so that the mechanism can be of lighter construction.

The track segment 54 and upper and

lower sprockets

50, 52 of conveyor 43 are fixed rigidly to the frame 40 while the track section 54 and

sprockets

50, 52 of conveyor 42 are suspended on a hinge 58 and a bifurcated arm 60 which supports the upper sprocket shaft 62. The upper end of the track section 54 is carried by the shaft 62 as shown in FIGURE 4 while the lower end is carried by the lower drive sprocket shaft 63 in a similar manner. Upper and lower

bifurcated arms

65, 66 are also journaled on the upper and

lower sprocket shafts

62, 63 and rest on restraining

cylinders

68, 69 which establish the spacing between track sect-ions 54, 54' to develop the required withdrawal and bending forces applied by the shoes 45, 45'. Should a change in ingot size be required, nuts 70 on

cylinders

68, 69 may be adjusted so as to change the distance between pressure shoes 45, 45' according to the thickness of the ingot to be cast. The pressure shoes 45, 45' are curved, convexly and concavely respectively to match the curvature being developed in the ingot I as it passes between the track sections 54, 54'. Since the pressure shoes 45, 45 get hot during contact with the ingot, two cooling tanks 73 with flowing water are positioned so that the pressure shoes 45, 45' pass through upon each revolution of the

conveyors

42, 43. Water spray box 40 includes a water seal 75 at the lower end where the ingot I emerges to collect cooling water.

As referred to previously, it occurs in the prior art that because the withdrawal and bending forces are transmitted to the ingot by cylindrical rolls, essentially a line contact is made with the ingot which is occasioned by extremely high pressures. This dictates that the placement of the withdrawal and bending rolls be at or near the point of complete solidification of the ingot with the consequent disadvantages discussed.

In accordance-with the present invention, and particularly where the ingot has a deep liquid center as usually found in casing steel for example, the withdrawal and bending device 17 provides for continuous application of a distributed bending and withdrawal force to a relatively large surface area of the ingot which eliminates distortion and crack formations in the ingot and permits location of the mechanism closer to the mold at a point where the ingot is only partially solidified as shown in FIGURE 2. With the invention, it is necessary only that the ingot have a skin I of sutficient thickness to withstand the distributed forces. The distributed forces are applied to a surface area of the ingot which is essentially a function of its cross sectional area. That is, for ingots of considerably larger cross section, the

conveyors

42, 43 will be considerably longer and the radius of curvature also considerably longer so that the bending forces are less concentrated. As a rule of thumb, the radius should be about 25 times the thickness of the ingot I.

Moreover, with the invention the shoes 45, 45' applying the distributive withdrawal and bending forces move with the ingot while it is being deformed. This is distinguished from the prior art where the ingot is pulled through rolls inducing certain dynamic rolling stresses thereto.

Modifications of the invention may be visualized by persons skilled in the art, however it should be appreciated that such changes are intended to fall within the invention in its broadest aspects as defined in the appended claims except insofar as limited by the prior art.

I claim:

1. A continuous casting installation including a flowthrough mold from which an ingot is cast and guide means for engaging opposed surfaces of the ingot'and continuously moving therewith along a curvilinear path intercepting the initial direction of movement of the ingot from the mold and diverting it along said curvilinear path, said guide means including: a pair of opposed stationary track sections, one concave and the other convex; said track sections positioned directly opposite each other and defining said curvilinear path and between which the ingot passes; and adjustable frame means for restraining said track sections against movement from a predetermined spacing in relation to the" ingot thickness so that the ingot is deflected from its original course while being withdrawn from the mold; endless conveyor means carried by each of said track sections, each conveyor means including a plurality of pivotally interconnected ingot engaging members having contact areas sufficiently large to distribute the ingot bending forces over an area larger than those obtainable with cylindrical roll contact; a pair of vertically spaced .sprockets for each conveyor successively engageable with the ingot engaging members to move the conveyors around their respective track section; and drive means for driving each conveyor in synchronism with respect to the ingot withdrawal rate.

2. The invention as defined in claim 1. wherein the concave track section includes a fiat portion extending upwardly a considerable distance above the top of the convex section for assuming consequential bending forces.

3. The invention as defined -in claim 1 wherein the ingot engaging members have curved contact surfaces corresponding in curvature to the curvature of its respective track section.

References Cited UNITED STATES PATENTS 1,139,884 5/1915 Melleri 164279 3,283,368 11/1966 Homan 164-282 FOREIGN PATENTS 700,450 12/ 1964 Canada. 992,759 7/1951 France. 876,422 8/ 1961 Great Britain. 930,193 7/ 1963 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner. R. SPENCER ANNEAR, Assistant Examiner.

US. 01. X.R. 164-274