GB2081149A

GB2081149A - Roll Stand for a Continuous Casting Plant

Info

Publication number: GB2081149A
Application number: GB8124215A
Authority: GB
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1980-08-08
Filing date: 1981-08-07
Publication date: 1982-02-17
Also published as: GB2081149B; FR2488166B1; FR2488166A1; DE3029990C2; JPS5765703U; DE3029990A1; BR8105090A

Abstract

A roll stand for a multi-strand continuous casting plant has a water cooled frame supporting pairs of rolls (4a, 4b) arranged on opposite sides of the path followed by a respective one of the strands (7). The roll (4a) of each pair is drivable through a chain drive from a motor (12) and is urged against the strand by a piston and cylinder unit (8), the projected dimensions of which do not significantly exceed the width of the roll. The various mechanisms are shielded from thermal radiation by hollow, water cooled shields (21). This arrangement allows the number of strands cast simultaneously to be increased while maintaining minimal distance between the strands. Individual drive motors for the rolls may be provided. <IMAGE>

Description

SPECIFICATION Roll Stand for a Continuous Casting Plant Multiple strand plants for continuous casting of metal, particularly steel, are known for the production of continuous cast strands in the form of billets having sides with a width of, for example, 80 to 1 50 mm. It is desirable to increase the yield of the cast material as far as possible while keeping production costs to the minimum.

However, although there are advantages in increasing the number of strands cast simultaneously, technical problems impose restrictions in this respect.

In particular, problems arise in connection with interstrand spacing. Although the mechanical construction of the plant does not present any insurmountable problems in this respect, the channel through which the molten metal is distributed to the individual moulds is the subject of substantial thermal expansion resulting in dispiacement of the delivery tubes fixed thereto and through which the metal is discharged.

Depending upon the cross-sectional dimensions of the strand, a tolerance of no more than + 10 mm in the width of each side relative to the centre line is permitted in the case of a strand with a total side width in the range of 80 to 150 mm. An off-centre discharge of the molten metal into an individual mould leads to uneven cooling of the cast strand as it descends from the mould and to dimensional inaccuracies. To minimise deviations of the delivery tube relative to the centre of the mould, the distance between the delivery tubes is desirably reduced to a minimum, resulting in moulds which are very close together. This proximity of the moulds and of the emerging cast strands leads to the space available for equipment between the strands being severely restricted.

A solution to the problem caused by thermal expansion of the distribution channel as well as an increase in the number of strands produced per unit length of such channel can therefore be achieved provided that the equipment arranged downstream of the mould is so designed that it does not obstruct the space between the strands.

According to the present state of the art, a six strand plant with a distance between the axes of the paths followed by the adjacent strands of 900 mm is feasible and in operation. The length of the distribution channel for this arrangement is given by 5x900 mm+2x400 mm=5,300 mm, a length which is manageable. In the case of a twelve strand casting plant having the same inter-path spacing, the length of the distribution channel would need to be 11 x900+2x400=10,700 mm.

The effect produced by thermal expansion of a distribution channel having this length is in excess of that which is acceptable. In other words, the changes in length of the distribution channel are such as to cause inacceptable shifting of the delivery tubes relative to the moulds. In addition, the heat losses along a path of molten metal of this length are inacceptable. In fact, the shifting of the delivery tubes alone prevents the manufacture of a plant having a greater capacity than six strands.

The present proposal is directed at redesigning the roll arrangements downstream of the mould in such a way as to permit the inter-strand spacing to be reduced to a minimum, thereby increasing the number of strands which may be cast per unit length of distribution channel thereby making possible a multi-strand machine producing more than six strands and possibly even as many as twelve strands.

In accordance with the present proposal, a roll stand for a multiple strand continuous casting plant comprises a frame assembled at least in part from cooled frame members, and a plurality of pairs of oppositely disposed rolls, the path of a respective one of a plurality of strands being located between the rolls of each pair, one roll of each pair being supported by a rocker support pivoted in the frame and movable by means of a piston and cylinder unit to cause the roll to bear against the strand, the projected dimensions of the said unit being such that they do not extend beyond the axial width of the respective roll, or at least not to any significant extent therebeyond, the rolls carried by the rockers being drivable by at least one motor mounted on the frame by way of chain drive means.

The axes of the drivable rolls are conveniently substantially aligned when the plant is in operation and extend transversely of the direction of movement of the strands. The axial width of each roll may be less than the dimension of the strand parallel to the axis of the roll so that the rolls themselves and their rocker supports do not intrude upon the space available between the strands. By arranging for the mechanism associated with each movable roll to be accommodated within a space no wider than the axial width of the roll or its rocker support and by the use of a chain as a power transmission element, a very narrow plant is made possible.

The proximity of the hot cast strand to the mechanism does not cause problems because of the use of cooled frame members in the construction of the strand. In practice, it is possible to achieve spacings of 350 mm between the centre lines of strands in the form of billets having sides with a width of between 80 and 1 50 mm. By making use of the present proposal, a distributing channel having a length of about 5,000 mm and a content of from 12 to 1 5 tonnes of molten steel with twelve delivery tubes for strands with cross-sectional dimensions of up to 1 50 mm side width is made possible. The casting of a quantity of molten metal of 300 tonnes may be carried out more economically, while still maintaining the required casting temperature in the molten metal.

Within the scope of the present proposal, each of the drivable rolls may be driven from a respective separate motor. However, such an arrangement is not preferred because of the complications caused by the need to cool the components of the plant, and by the arrangements necessary for controlling the speed of the individual strands. Preferably, therefore use is made of a single motor common to a group of drivable rollers, conveniently two, three or more adjacent rolls. Power is transmitted from the motor by a chain drive to a shaft, from which drive is transmitted by individual chains to the respective drivable rolls. Substantial expense is hereby avoided. The motor, or each of the motors if provided, may be mounted on the top of the frame.The roll stand proposed herein may be designed as a structural unit which forms one segment of the strand support arrangement, or as a driving stand. Alternatively, two or more stands in accordance with the proposal may be arranged one behind the other in the direction of travel of the strands and together may constitute a straightening roll stand.

The chain drive mechanism is desirably shielded from the thermal radiation emanating from the strands. Special measures are necessary because of the narrow construction of the parts and it is therefore further proposed that watercooled hollow or double walls be provided as shields for the bearings of the rollers, and/or the bearings of the rocker supports, the piston and cylinder drive units and the drive motors. These water-cooled double or hollow walls may be arranged to accommodate the bearings of the rocker supports and/or the rollers directly.

In the drawings: Figure 1 is a side view of a first embodiment of a stand in accordance with the present proposal, Figure 2 is a view of the first embodiment of stand looking along the centrelines of the strands, and Figure 3 is a view similar to Figure 2 but of a second embodiment.

Referring first to Figures 1 and 2, a multistrand continuous casting plant includes a set of moulds from which a plurality of strands 7 issue simultaneously and follow paths which pass over a common surface. In particular, although not essentially, twelve strands may be produced simultaneously, conveniently in four groups, each such group of three strands issuing from a respective mould assembly conveniently of the construction described and illustrated in the specification of our co-pending application No.

8124213 (Ref: 20963 JFS/SJI). In the drawings the strand of one such group are shown together with a stand supporting and driving that group of strands at a position along horizontal paths which they follow for part of their travel. This stand includes a frame assembled in part from vertical frame members 1, transverse frame members 2 and upper cross bars 3, all of which members 1,2 and 3 are hollow and through which passes a flow of water or other coolant. Within the frame, each strand is engaged by a respective pair of rolls 4a and 4b, the lower roll 4b in each pair being journalled for free rotation in a bracket fixed to the frame.The upper roll in each pair is drivabie and mounted in a rocker,support 5 comprising a pair of rocker arms 5a, 5b pivotal about a horizontal shaft 6 carried by brackets 3a mounted on the cooled cross bar 3. A cylindrical bearing housing surrounding the shaft extends from the arm 5a for bearings 23. The rocker support is movable to press the roll 4a against the strand by means of a respective piston and cylinder unit, that unit relating to only one roll being shown in the drawing. It will be understood, however, that each of the rolls 4a is associated with identical mechanisms. The cylinder 8 of the unit is articulated to forks 11 on the cross-member 2 by.

pins 1 Oa and lOb. Pins 9 on the piston rod are journalled in forks carried by a bridge piece extending between the two arms of the rocker support. The piston and cylinder unit and associated parts are accommodated within, or substantially within, the projection of the axial width of the associated rolls.

In the embodiment shown in Figure 2, all of the three drivable rolls of the group are driven from a single electric drive motor 12 mounted above the frame on the cross-member 2. The motor 12 incorporates gearing driving an output shaft bearing a set of sprockets 13 for a set of chains 1 7 driving sprockets 14 on the shaft 6 on which all of the support arms are pivoted. As illustrated, the shaft 6 is assembled from three axially aligned segments secured together although a one-piece shaft can be employed instead. Mounted on the shaft 6 between the arms of each rocker support is a chain wheel 1 4a of a chain 18 driving the shaft 1 6 to which the roll 4a is keyed.The chains 17 and 18 and the sprockets 14, and 15 are arranged in a small space between the rolls 4a, 1 9a and 20a and the rocker arm 5b.

Additional shielding for the shaft 6 is provided by a water cooled hollow or double wall 21 carried by the frame members 1. Such watercooled walls may also be provided to provide a shielding effect for the bearings 22 of the rolls, the bearings 23 of the rocker supports and the piston and cylinder units 8 and the motor 12, in addition to the shielding provided by the cooled cross-members 2.

The embodiment shown in Figure 3 is similar to that in Figure 2 except that each rocker support is pivoted on a respective one of three short shafts 24a, 24b and 24c, each driven from a respective one of three motors 12a, 12b and 12cog by an individual chain 1 7 passing over sprockets 13 and 14 on the output shaft and the shaft 6 respectively. The three motors may, of course, have a lower rating than the single motor shown in Figure 2.

In each embodiment the strands are of billetlike square cross-section arranged with two apices of each strand lying in a common plane mid-way between the pairs of rolls when they occupy their operative positions, so that the strands present a lozenge-like cross-section as viewed in Figure 2 or Figure 3. Each roll defines a V-shaped peripheral groove by being assembled from two roll bodies 1 9a with frusto-conical surfaces 20a in order to engage portions of the strand adjacent a respective edge. Modifications to the rolls may be made to permit handling of other cross-sections of strand.

In a six or more multi-strand plant, two or more stands as described may be arranged side by side and two or more stands may be arranged in succession in order to support each group of three strands.

The stands may be angled in order to support strands following vertical, inclined or curved paths.

Claims

1. A roll stand for a group of strands of multiple strand continuous casting plant comprising a frame assembled at least in part from cooled frame members, and a plurality of pairs of oppositely disposed rolls, the path of a respective one of a plurality of strands being located between the rolls of each pair, one roll of each pair being supported by a rocker support pivoted on the frame and movable to cause the roll to bear against the strand under the action of a piston and cylinder unit, the projected dimensions of which do not extend to any significant extent beyond the axial width of the respective roll, the rolls carried by the rockers being drivable by at least one motor mounted on the frame by way of chain drive means.

2. A roll stand according to claim 1, wherein each of the drivable rolls is supported by a respective rocker support, the rocker supports of all of the drivable rolls of a group being arranged adjacent one another, each drivable roll being drivable by a respective chain drive from sprocket means on a shaft common to all of the drivable rolls of the group, said shaft being drivable from a single motor carried by the frame.

3. A roll stand according to claim 1 or claim 2, including means which at least in part shield the chain drive means from heat radiated by the strands.

4. A roll stand according to any preceding claim, wherein bearings for the drivable rolls, for the rocker supports, the piston and cylinder mechanisms, the motors and the like are shielded from thermal radiation from the cast strands by means of cooled double or hollow walls.

5. A roll stand according to any preceding claim, wherein cooled double or hollow walls directly accommodate bearings for the rocker arms and/or the rolls.

6. A straightening roll stand comprising two roll stands as claimed in any preceding claim arranged one behind the other in the direction of travel of the strands.

7. A roll stand for a continuous casting plant substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 or Figure 3 of the drawings.