CA1061079A - Built-up continuous casting mould - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:

Built-up continuous casting mould, comprising four cooled plates each of which has a surface defining a side of a mould cavity of predetermined cross-section, each pair of the plates on respectively opposite sides of the cavity having load-bearing faces which abut co-operating load-bearing faces on the two other plates so that the plates can be held together by clamping devices applying pressure in a direction substantially normal to said load-bearing faces, and further abutting faces on each plate provided between the load-bearing faces and the cavity-defining plate surface which latter abut-ting faces are so arranged that the notional extensions into the mould cavity of the two such faces on each plate intersect.
There results improved cast strand quality and lengthened mould service file. Moreover, after remachining of the faces of the joints, the mould according to the invention can still be reassembled and provided with the same cross-section as before.

Description

~o6~079 Thc invention relates to a built-up mould for the continuous casting of metal, particularly steel.
According to the nature and size of the cross-section which it is desired to cast, a choice is usually made between tube, ingot or built-up moulds. ~he latter are usually com-posed of four plates attached to a supporting frameO Such built-up moulds, which are also known as plate moulds, can be clas-sified as being adjustable or incapable of adjustment. Adjus-table built-up moulds can be adjusted to different casting cross-sections because the ends of the shorter plates are displaceablygripped between the plates which form the longer sides of the mould. In the case of non-adjustable moulds the two facing pairs of plates are fitted together at the mould corners for the production of a specific casting cross-section.
A mould has been proposed which has a non-adjustable cavity ~ormed by four cooled plates. Two facing plates on op-posite sides fit into slots providing load-bearin~ faces on the t~o other plates which face each other and form the two remaining sides. ~he load-bearing faces adjoining the mould cavity form joints of conventional kind. lhis built-up mould can be held together by clamping devices acting substantially in a directional normal to the load-bearing faces. However, in such moulds the joints begin to open after a relatively short period of service because the plates tend to be plastically defGrmed where they are exposed to the heat of the metal being cast. Open joints may cause faults in the cast strand and - they may even lead to metal breakoutO Moulds which are faulty for such a cause must therefore be subjected to re-machining after a specified number of pours. Even if only very ]ittle material is machined away from the surfaces of the mould cavity near the joints, the moulds cease to have the ori~inal cross-sec'ion and after having been -thus remachined they cannot be 106~079 used for casting the original section again.
It is an object of the present invention to provide a built~up non-adjustable mould in which an improved design of the joints contributes towards improving the quality of the cast strand and permits the service life of the mould to be lengthened. Moreover, it is another object of the invention to provide a mould which after re-machining of the faces of the joints can still be re-assembled and provide a cavity o*
the same cross-section as before.
According to the invention we provide a built-up con-tinuous casting mould, comprising four-cooled plates each of which has a surface defining a side of a mould cavity of pre-determined cross-section, each pair of the plates on respec-tively opposite sides of the cavity having load-bearing faces which about co-operating load-bearing faces on the two-other plates so that the plates can be held together by clamping devlces applying pressure in a direction substantially normal to said load-bearing faces~ and further abutting faces on each plate provided between the load-bearing faces and the cavity-defining plate surface which latter abutting faces are so arranged that the notional extensions into the mould ca-vity of the two such faces on each plate intersect.
In a mould according to the invention the forces of expansion which act across the longitudinal axis of the abut-ting faces are taken up in a more desirable way than is the case for instance between faces abutting at right angles. ~ur-thermore, the forces generated by the clamping device are removed from that part of the joint which is exposed to the thermal load and are transferred to the load-bearing faces which are not thermally stressed. The abutting faces adjoining the cavity of the mould are thus relieved of these clampin~
forces. Another major advantage arises with the mould because, ~061079 when wear has occured and machinillg of the mould walis as well as bf the joints is desi~ed, this can be done without the internal cross-section of the mould being thereby affec-ted.
Furthermore, the design of the joint also permits cooling ~ater slots needed for cooling to be more efficiently located.
With advantage such mould may be chromium-plated to prolong their service li~e, or they may be provided with coatings ap-plied by other known coating techniques. All these advantages contribute towards impriving the quality of the casting and prolonging the service life of the mould.
An optimum thic~ness of material vhich is available for removal by subsequent machining will be available, if the notional extensions of the abutting faces of the joint intersect at an angle of between 70 and 110. ~he number of times a set of plates can thus be re-machined is greater when the an-gle is between the specified limitsO
In the case of moulds having an arcuate cavity the faces of the joints may likewise be curvedO However, it is preferred that they should be flat and end in the centre of a flat or radiused fillet provided in the corner of the mould caYityO These features will permit the flat faces of the joint as well as the load-bearing faces to be machined on ordinary machine tools so that only the curved surfaces need be machined on specialised machinesO Moreover, the flat faces in as-sociation with flat fillets or radii at the corners permit any desired degree of taper of the mould cavity to be produced to a high degree of precision with a minimum expenditure of ,,. timeO
In order to provide the outermost layer of the plate, 3 which comes into contact with the liquid metal, with a limited freedom of expansion it is possible to provide a clearance gap between the abutting faces forming the joint at the corner when the mould is coldO Plastic deformation of the edge of the joint can thus be substantially reduced and the useful life of the mould fur-ther improved.
If it is desired that the plates defining the cavity of the mould should be relieved of the forces generated by the clamping device the cooled plates may be mounted on res-pective backing plates and the load-bearing faces may then be provided on the backing plates rather than on the oooled plates directlyO
The above and other features and advantages of the invention will become further apparent as the following des-cription of the pre~erred embodiments shown in the accompanying drawings proceedsO In the drawings :-Pigure 1 is a diagrammatic plan view of a first em-bodiment of a built-up mould;
~ igure 2 is a diagrammatic plan view of another em-bodiment of a mould, &nd ~ igures 3 to 6 are plan views of different examples of corner joints, each figure showing only one of the corners of the mouldO
Referring first to Figure 1 there is shown a straight-sided mould for the continuous casting of steel built up to a required casting cross-section by plates 2 enclosing a square cavity 30 The plates 2, which will usually consist of copper, are cooled and are bolted to backing plates 50 Two plates 2 on opposite sides each bear against co-operating load-bearing abutment faces 6 on the plates forming the t~o other sides.
- Clamping devices 7 indicated by arrows apply pressure subs-tantially in a direction normal to the abutment faces 6 and 3 enable the plates to be held tightly together. The clamping devices 7 may be, for example, hydraulic jacks or tie rods. Bet-~een the plate surfaces 8 forming the sides of the cavity 3 106~79 and the abutment faces 6 this mould differs from a mould accor-ding to the state of the art in being provided with additional abutting faces 9. ~he latter faces 9 are formed on the plates

2 in such a way that notional extensions 11 of the two faces 9 associated with each plate 2 intersect, as shown in the drawing, inside the mould cavity 3, although they might also be arranged to intersect outside the cavity 3O The angle of intersection 13 of the extensions 11 will preferably be between 70 and 110.
~he mould in ~ig. 2 is provided with flat fîllet fa-ces 14. The faces 9 of the joints in this example extend from the corner between the fillets 14 and the plate surfaces 8 which define a mould cavity 3' of rectangular cross-sectionO
~or the sake of simplicity the backing plates 5 shown in ~igo 1 are omitted in this drawingO
The corner of the mould illustrated in ~ig. 3 is part of a curved mouldO Only a portion of a plate 20 forming a straight side and a portion of a plate 21 forming the outer curved side of the mould are shown. Edges 22 indicate the upper end and edges 23 the bottom end of the mould cavity 3.
~he plates 20 and 21 are set so that the mould cavity tapers by an amount indicated at 25. ~roken lines 26 represent the extreme envelopment curve of the con~avity of the outer curved side of the mould cavity 3. m e faces 9 in this curved mould are neYertheless flat, and they end roughly by the middle of the flat fillet faces 14 in the cornerO If the flat fillet faces 14 are replaced for instance by radiused faces, then the faces 9 of the joint may still intersect the radius in the middle~ A clearance gap 27 is allowed to remain bet~een the co-operating faces of each plate when the mould is cold. The width of the gap 27 is so calculated that it is capable of taking up part of the thermal expansion of the plates. Spe-la6l07s cifically the width of the gap depends upon several castingparameters, such as the cross-section of the mould, the ma-terial of the plates 20 and 21, the metal that is to be cast, the casting temperature, the intensity of the cooling effect, and so forth. A correctly dimensioned gap will close during the starting-up phase of a pour as the surface of the pool rises so that the liquid metal will not penetrate.
As a protection from splutter of the liquid metal, particularly at the beginning o~ the pour, such clearance gaps can be protected with adhesive tapeO The clearance is usually chosen to be in the neighbourhood of about 0.3 mmO In this example the faces 9 are at an angle of 45 to the forces of expansion of the two plates 20 and 21 which act in the direc-tion of the arrows 28. The described arrangement results in a reduction in the width of the gap amounting to T when the plates expand by an amount ~ ~ in the direction 28.
In ~igo 4 which shows a corner of a mould with a ra-diusea fillet on an enlarged scale a layer 40 on the surfaces 8, the faces 9 of the joint and on the outer of the two faces 6 is available for subsequent machiningO If this layer 40 is machined off~ then the resultant fresh edge 41 could move in the direction of arrow 42 and edge 43 in the direction of arrow 44 until the re-assembled plates reform the original line 45 of the joint. The predetermined casting cross-section remains exactly the same after machining as it had been prior to ma-chining. 47 are slots for cooling water which can be machined into the plate so that they are closer to the surfaces of the joints than in conventional moulds.
In the corner of another mould illustrated in Figo 5, the load-bearing faces 6 of the corner joint are not provided on the cooled plates 2, but on the backing plates 5O The term plate, as herein used, is therefore understood to comprise the assembly of plate 2 with the associaied backing plate 5. In this form of construction the work invol~ed in re-machining the plates 2 is therefore less. Instead of re-machining the load-bearing surface on one of the backing plates a suitably prepared spacing block 50' can be replaced by a fresh spacing block 50. According to the number of times the layer 40 on plates 2 is designed to be re-machined spacing blocks of ap-propriate thickness 51 to correspond to the material to be removed at each machining will be prepared. It will be readily understood that such backing plates can be re-used to serve several sets of plates 2.
The proposed built-up mould is suitable for casting ; blooms, slabs and intermediate sections.

Claims (5)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A built-up continuous casting mould, comprising four cooled plates each of which has a surface defining a side of a mould cavity of predetermined cross-section, each pair of the plates on respectively opposite sides of the cavity having load-bearing faces which abut co-operating load-bearing faces on the two other plates so that the plates can be held together by clamping devices applying pressure in a direction substantially normal to said load-bearing faces, and further joint surfaces on each plate provided between the load-bearing faces and the cavity defining plate surface which latter abutting faces are so arranged that the notional extensions into the mould cavity of the two such faces on each plate intersect.

2. A built-up mould according to claim 1, wherein the extensions intersect in the mould cavity at an angle of between 70° and 100°.

3. A built-up mould according to claim 1 having an arcuate mould cavity, wherein the joint surfaces are flat surfaces.

4. A built-up mould according to claim 1, 2 or 3, wherein the joint surfaces are substantially roughly centrally disposed in relation to flat or radiused fillets provided in the corners of the mould cavity.

5. A built-up mould according to claim 1, 2 or 3, wherein a clearance gap is present between the two joint surfaces at a corner when the mould is cold.