US3347308A

US3347308A - Machines for continuously casting metal

Info

Publication number: US3347308A
Application number: US486294A
Authority: US
Inventors: Saunders Charles Wilfrid
Original assignee: United Steel Companies Ltd
Current assignee: United Steel Companies Ltd
Priority date: 1965-09-10
Filing date: 1965-09-10
Publication date: 1967-10-17
Anticipated expiration: 1984-10-17

Description

Get. 17, 1967 c, w, SAUNbERS 3,347,308-

MACHINES FOR CONTINUOUSLY CASTING METAL Filed Sept. 10, 1965 e Sheets-$heet 1 Oct. 17, 1967 c. w. SAUNDERS 3,347,308

MACHINES FOR CONTINUOUSLY CASTING METAL 6 Sheets-Sheet 2 Filed Sept. 10, 1965 Oct. 17, 1967 I c, SAUNDERS 3,347,308 7 MACHINES FOR QONTINUOUSLY CASTING METAL Filed Sept. 10, 1965 i 6 Sheets-Sheet 5 Oct. 17, 1967 c. w. SAUNDERS MACHINES FOR CONTINUOUSLY CASTING METAL 6 Sheets-Sheet 4 Filed Sept. 10, 1965 Oct. 17, 1967 c, w. SAUNDERS 3,347,308

MACHINES FOR CONTINUOUSLY CASTING METAL Filed Sept. 10, 1965 Sheets-Sheet 5 MACHINES FOR CONTINUOUSLY CASTING METAL Filed Sept. 10, 1965 6 Sheets-Sheet 6 United States Patent 3,347,308 MACHINES FOR CONTINUOUSLY CASTING METAL Charles Wilfrid Saunders, Aspatria, Cumberland, England,

assignor to The United Steel Companies Limited, Broomhill, Sheffield, England, a British company Filed Sept. 10, 1965, Ser. No. 486,294 7 Claims. (Cl. 164-282) ABSTRACT OF THE DISCLOSURE 'are mounted coaxially and driven from the same side of the machine. To insure firm gripping of the strands despite possible variations in the thickness and to allow the drive to be transmitted to both pairs from the same side, each movable roll or its shaft of the pair furthest from the driving side is connected to the corresponding movable roll or its shaft by an Oldham coupling.

In machines for the continuous casting of metals such as steel the liquid metal is poured into an open-ended mould in which primary cooling takes place. The metal emerges as a strand with a solid skin. Secondary cooling is necessary below the mould, and normally is effected by a large number of water sprays directed onto the strand within a chamber through which the strand passes downwards. This secondary cooling causes the metal to solidify completely or at least to an adequate extent to be engaged by withdrawal rolls which grip the strand frictionally. The movement of the strand is in effect controlled by the withdrawal rolls, of which there may be one or more pairs. Continuous casting machines are of various kinds. In one kind, the mould is vertical and the strand moves vertically downwards from it, being cut into lengths while still travelling vertically.

In another kind of machine the strand, on emerging from a vertical mould, is bent to reach a straightening apparatus horizontally. Withdrawal rolls in such a machine engage the strand before it is bent.

In another kind of machine the mould is curved so that the strand is curved, and again it arrives at a straightening apparatus substantially horizontally. In such a machine the withdrawal rolls may form part of the straightening apparatus.

At the beginning of each cast it is usual to close the bottom of the mould by the head of a dummy bar, which is drawn downwards to pass through the withdrawal rolls and is separated from the strand after passing through these.

The continuous casting machines first built cast only a single strand. This resulted in the casting process being slow, and in modern machines two or more strands are cast simultaneously through two or more moulds. In most such machines the moulds are mounted independently, and there are separate withdrawal rolls, independently driven, for each strand. The necessity of providing separate driving units for each set of rolls increases the space required and the cost of the plant. A recent development comprises the provision of a single set of withdrawal rolls for two strands, or the mounting of separate rolls for two strands on a single shaft. In either case only a single driving unit is required for rolls engaging more than one strand.

However the abolition of the invidivual pairs of rolls,

each with its own driving unit, brings with it various disadvantages. The rolls necessarily expand while they are engaging the hot strands, and they may subsequently contract unevenly. During service, the sectional dimensions of dummy bars may become slightly changed, and it is not unknown for one of the dummy bars to pass through a single pair of withdrawal rolls without being gripped while the other is firmly held by these rolls. The same disadvantage may arise with the strands themselves, since variations in section may occur as a result of distortion or contraction, and a slight variation may lead to loss of contact between one strand and the withdrawal rolls.

In a machine according to this invention for casting two metal strands each engaged by a pair of withdrawal rolls, the corresponding rolls of the two pairs are mounted coaxially and driven from the same side of the machine. One roll in each pair is mounted to move towards or away from the other. Each roll so mounted of the pair further from the driving side is connected to the corresponding nearer roll to a shaft thereof by an Oldham coupling. As is well known, an Oldham coupling comprises two discs, one on each of the shafts or other members to be coupled and a third disc between them, this third or central disc making tongue-and-slot engagement with each of the two outer discs, and the tongue (or slot) on one face being at right angles to the tongue (or slot) onthe other face. If the driving and driven shafts or other members cease to be in axial alignment, relative movement between either tongue and its slot or between each tongue and slot allows power still to be transmitted through the coupling. In other words, because an Oldham coupling allows variation in shaft centres, provided that the shafts remain parallel, its use between the withdrawal rolls of a multi-strand continuous casting machine allows just that amount of variation required to maintain constant tractive effort on all the strands. Thus it becomes possible to drive all four rolls from one side of the machine, and yet allow the individual rolls, while remaining parallel to one another, to deviate from precise coaxiality.

In each pair of withdrawal rolls, only one roll is normally made movable towards and away from the other and therefore yieldable under variations in strand section. The other roll in each pair is normally mounted in fixed bearings. Oldham couplings are preferably provided between these latter rolls also, that is to say the whole assembly is symmetrical on the two sides of the strand, but this is not essential.

In a machine according to the invention each strand may be engaged by a single pair of rolls or by more than one such pair, that is to say there may be one set of withdrawal rolls or more than one set. When there is more than one set, the sets are preferably but not necessarily identical in construction.

The movable roll in each pair may be subjected to hydraulic or spring pressure or both.

Preferably each movable roll is carried by a housing that includes bearings for the roll and that can move in a cross-beam in which all the housings are mounted.

Some constructions according to the invention will now be described in detail with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 is a front elevation of one construction;

FIGURE 2 is ,a side elevation of the same construction, looking in the direction of the arrow II in FIG- URE 1;

FIGURE 3 is a section on the line III-III in FIG- URE 1 and is on a larger scale;

FIGURE 4 is a section on the line IV-IV in FIG- URE 3;

FIGURE 5 is an elevation similar to FIGURE 1 of a construction suitablefor a three-strand machine;

a 3 FIGURE 6 is a similar elevation of a construction for a four-strand machine;

FIGURE 7 is a plan of'part of a modified construction;

FIGURE 8 is a section on the line VIIIVIII in FIGURE 7; and,

FIGURE 9 is a plan of the arrangement of the withdrawal rolls in a four-strand machine.

FIGURES l and 2 show the withdrawal rolls for a machine for continuously casting two curved steel strands. The apparatus shown is intended to engage the strands at points where they are moving substantially horizontally, and comprises a frame 1 which supports four pairs of rollers, two for each strand. One strand is engaged successively by a pair of

rolls

2 and 2 and a

second pair

3 and 3, and the other strand is engaged successively by a pair of

rolls

4 and 4 and a further pair not visible in FIGURES 1 and 2.. The construction and arrangement of the rolls 3 and 3' and the invisible pair are exactly the same as that of the

rolls

2, 2 and 4, 4'. The

rolls

2 and 4 are coaxial, and so are the rolls 2' and 4. FIGURES 3 and 4 show the roll 4 and its mounting. The roll is made in one piece with stubshafts 5 and 5' and an end disc 6. The

stubshafts

5 and 5 are carried in split bearings 12 and 12' in a housing 7. This housing 7 in turn is mounted within a beam 8 in such a manner that it can slide only in a vertical direction. The beam 8 is mounted on the main frame 1. The housing 7 is constructed as a closed cylinder, through the top of which passes a piston rod 10 which is fixed to the beam 8 and to which a piston 9 is fixed. This piston 9 divides a cylindrical part 11 of the housing into two, and hydraulic connections (not shown) are provided for admitting fluid to or discharging it from the spaces above and below the fixed piston 9. If pressure is applied below the piston while the back pressure above the piston is relieved, the housing 7 is forced downwards, carrying the roll with it. By regulating this back pressure the speed of descent of the roll on to the strand can be controlled. If pressure is applied above the piston 9 and the pressure below the piston is relieved, the roll will be lifted clear of the strand, shown at A.

Limitation on the vertical movement of the housing 7 is imposed by a stop 13 which is fixed in the wall of the beam 8 and enters a slot in the housing 7. This stop 13 also prevents rotation of the housing and roller within the beam.

The beam 8 in which the housing 7, and also the similar housing 7 for the roll 2, are mounted, is vertically movable in the main frame 1, in order to adjust the rolls for different section sizes. It can be so moved by

hydraulic rams

14 and 14, and of course when it has been set for any given section size it is firmly fixed in position.

At the beginning of a cast a dummy bar is always threaded through the withdrawal rolls and passed upwards along the usual roller track into the mould. It is important to avoid damage to the head of the dummy bar which might prevent it from closing the bottom of the mould satisfactorily. It is also easier, and more convenient to locate the dummy bar if the rolls have been lifted clear. By moving the beam 8 upwards adequate space for the threading of the dummy bar through the withdrawal rolls is provided. When the head of the bar is passed through, and the bar has been correctly located, the beam is lowered again.

The roll 2 is identical with the roll 4 and is made in one piece with a disc 15. The

discs

6 and 15 together with a third or central disc 16 form an Oldham coupling 17. The drive is transmitted from a motor through a shaft 18 and coupling 1 to the stub shaft 5 of the roll 4, and through the Oldham coupling 17 to the roll 2. It will be seen that the drive is thus transmitted directly to the roll nearer the driving side and indirectly through the Oldham coupling to the roll further from the driving side. Moreover, as all the rolls are driven from one side of the machine, there is considerable simplification of layout and maintenance.

The lower rolls 4' and 2' are mounted in

bearings

20 and 20 and 21 and 21' respectively, these hearings being carried by the main frame 1. The rolls 2' and 4 are identical in construction with the corresponding

rolls

2 and 4 and are interconnected by an Oldham coupling 17'. Since the lower rolls 2' and '4' are not mounted to move towards and away from the

roll

2 and 4, the risk that they may come out of alignment is small. Accordingly the provision of an Oldham coupling between the two lower rolls is not essential, but is highly desirable for another reason. This is that by making each roll and the disc on it that forms part of the Oldham coupling in one piece, the axial length of the assembly of rolls and Oldham coupling is reduced to a minimum. It follows that the distance between the centre lines of the parallel strands is small, and indeed is much smaller than in the common practice hitherto. Naturally the lower rolls must be in the same relative position as the upper rolls, and the provision of the Oldham coupling between them allows exact symmetry.

If for any reason the cast in one strand is to be stopped, the upper roll engaging it can immediately be lifted by upward movement of the roll housing within the beam 8.

FIGURE 5 shows withdrawal rolls in a machine for casting three strands simultaneously. The construction is essentially the same as that in FIGURES 1 and 2, except that a third pair of

rolls

22 and 22 is provided, the roll 22 being connected to the roll 2 by an Oldham coupling 23, and the roll 22' being connected to the roll 2' by an Oldham coupling 23'.

Of course, if desired, in a three-strand machine the withdrawal rolls may be arranged as two pairs driven from one side of the machine and a single pair driver from the other side.

FIGURE 6 shows a withdrawal apparatus for a fourstrand machine. In effect the rolls shown in FIGURES 1 to 4 are duplicated, two of the strands being engaged by

rolls

2 and 2 'and 4 and 4' identical with those shown in FIGURE 1, and the other two strands by rolls 2A and 2A and 4A and 4A. These latter rolls are driven from the other side of the machine. The housing for all the upper rolls are carried in a single beam 8.

In the constructions so far described, the pairs of rolls driven from one side of the machine must always be rotated together, and at the same speed. This is not always desirable, and indeed in some machines it is essential to be able to stop one strand and hold it by withdrawal rolls while allowing the casting of another strand to continue. For example, in a machine in which the strands are vertical, the casting of one strand may have to be interrupted, and then this strand must be gripped firmly by stationary withdrawal rolls.

Independent operation of adjacent pairs of rolls is possible when the roll nearer the driving side is carried by and free to turn on a shaft connected by an Oldham coupling to the corresponding roll further from the driving side or to a shaft thereof. The nearer roll can then be driven around the shaft through one drive, and the further roll can be driven through the shaft by another drive. Thus one roll can be completely stopped while the other turns, or while both rolls turn they can be driven at independent speeds.

Such a construction in which the two rolls are independently driven is shown in FIGURES 7 and 8. These figures simply show the upper roll of the pair nearer the driving side. The roll is shown at 24 and it is made integral with a sleeve 25 and a stub shaft 26, a bore being made through it. This roll is carried by a shaft 27 through end bearings 28 and 28', and a disc 29 of an Oldham coupling 30 is formed on the end of the shaft 27. A gear wheel 31 is keyed to the sleeve 25 and meshes with another gear wheel 32 fixed to a shaft 33. The

gear wheels

31 and 32 are housed in a gear box 34 that forms part of the roller housing, the remainder of which is the same as the housing 7 shown in FIGURES 3 and 4.

The roller 24 is driven through a coupling 35 and the

gear wheels

32 and 31. The roll (not shown) that engages the next strand is driven independently through the shaft 27 and the Oldham coupling 30. The advantage is still obtained that both rolls are driven from one side of the machine, and that any lack of alignment of the two rolls is taken up by the Oldham coupling, together with the considerable additional advantage that either pair of rolls ran be stopped without the other.

FIGURE 9 shows the general arrangement of the drive of the Withdrawal rolls in a four-strand machine in which each pair of rolls is independently driven. Each strand is successively engaged by two pairs of rolls, the figure showing the upper rolls of the pairs. There are two driving motors on each side of the machine, namely 36 and 37 on the left-hand side and 38 and 39 on the righthand side. The motor 36

drives shafts

41 and 42 through a gear box 40 and thus the upper rolls nearer the left-hand side that engages the nearest strand. The motor 37

drives shafts

43 and 44 through gearing in the same gear box 40 and thus drives the upper rolls that engage the third strand through Oldham couplings. The lower rolls are driven from the same motors or gearbox through shafts concealed in the drawing by the shafts 41 to 44. The arrange ment on the right-hand side of the machine is similar.

I claim:

1. In a machine for continuously casting two metal strands each engaged by a pair of withdrawal rolls in which the corresponding rolls of the two pairs are mounted generally coaxially and driven from the same side of the machine, and means mounting one roll in each pair to move towards or away from the other the improvement comprising, an Oldham coupling operativey and rotatably connecting the coaxially adjacent corresponding rolls so that the corresponding rolls may be driven from the same side of the machine and compensate for variations in the thicknesses of the two metal strands being continuously cast.

2. In a machine according to claim 1 in which the Oldham coupling operatively and rotatably connects all corresponding coaxially adjacent rolls.

3. In a machine according to claim 1 in which each movable roll is directly carried by a housing that includes bearings for the roll and that can move in a crossbeam in which all the housings are mounted.

4. In a machine according to claim 3 in which the housing includes a cylinder mounted to slide under hydraulic action over a piston fixed to the cross-beam.

5. In a machine for continuously casting two metal strands each engaged by a pair of withdrawal rolls and are driven from the same side of the machine the improvement comprising corresponding rolls of the two pairs are mounted coaxially and form the two outer parts of an Oldham coupling, one roll of each pair being mounted to move towards and away from the other roll of the same pa1r.

6. In a machine for continuously casting two metal strands each engaged by a pair of withdrawal rolls in which the corresponding rolls of the two pairs are mounted coaxially and driven from the same side of the machine, means including an Oldham coupling rotatably connecting each roll of the pair furthest from the driving side to a shaft on which the corresponding roll of the other pair is free to turn.

7. A machine according to claim 6 in which each roll of the pair nearest the driving side is driven through gearing and formed in one piece with a sleeve carried by a shaft formed in one piece and with an end disc of the Oldham coupling.

References Cited UNITED STATES PATENTS 2,150,248 3/1939 Rosenbaum 72249 2,297,214 9/ 1942 Gosslan 74665 2,630,022 3/1953 Terdina 74-665 XR 2,814,843 12/1957 Savage et al. 164-82 FOREIGN PATENTS 574,185 12/1945 Great Britain.

817,637 10/ 1951 Germany.

801,819 9/1958 Great Britain.

121,913 1959 Russia.

928,093 6/1961 Great Britain. 1,335,289 7/1963 France.

I. SPENCER OVERHOLSER, Primary Examiner. R. S. ANNEAR, Assistant Examiner.

Claims

1. IN A MACHINE FOR CONTINUOUSLY CASTING TWO METAL STRANDS EACH ENGAGED BY A PAIR OF WITHDRAWAL ROLLS IN WHICH THE CORRESPONDING ROLLS OF THE TWO PAIRS ARE MOUNTED GENERALLY COAXIALLY AND DRIVEN FROM THE SAME SIDE OF THE MACHINE, AND MEANS MOUNTING ONE ROLL IN EACH PAIR TO MOVE TOWARDS OR AWAY FROM THE OTHER THE IMPROVEMENT COMPRISING, AN OLDHAM COUPLING OPERATIVELY AND ROTATABLY CONNECTING THE COAXIALLY ADJACENT CORRESPONDING ROLLS SO THAT THE CORRESPONDING ROLLS MAY BE DRIVEN FROM THE SAME SIDE OF THE MACHINE AND COMPENSATE FOR VARIATIONS IN THE THICKNESS OF THE TWO METAL STRANDS BEING CONTINUOUSLY CAST.