US3662814A - Mold for continuous casting of metal - Google Patents

Abstract

A mold for continuous casting is disclosed having plates joint at corner pieces, whereby a corner piece is bolted to a plate and tensioned against the other plate at that corner.

Description

Unite States Patent Kipp et al.

[151 3,662,814 1 May 16, 1972 [54] MOLD FOR CONTINUOUS CASTING OF METAL [72] Inventors: Adolf Kipp, Osnerbruck, Germany; Walter Stockinger, Torshalla, Sweden; Peter J. Konig, Zumikon, Switzerland [73] Assignee: Concast AG, Zurich, Switzerlanda part interest [22] Filed: Aug. 28, 1969 [21 Appl. No.: 853,698

[30] Foreign Application Priority Data Aug. 24, 1968 Germany ..P 17 58 867.9

US. Cl

....l64/283, 164/273 ..B22d 11/02 [58] Field of Search 164/273, 82, 280, 283; 249/135, 158, 163, 165

[56] References Cited UNITED STATES PATENTS 2,767,448 10/1956 l-larter et al 164/283 3,082,496 3/1963 Bungeroth et al. 1 64/280 3,292,216 12/1966 Colombo ....164/273 UX 3,295,172 1/1967 Dain... ..l64/283 3,528,485 9/ 1 970 Vogel 164/273 FOREIGN PATENTS OR APPLICATIONS 681,844 3/1964 Canada 164/283 Primary Examiner-Robert D. Baldwin Attorney-Smyth, Roston & Pavitt ABS I'RACT A mold for continuous casting is disclosed having plates joint at comer pieces, whereby a corner piece is bolted to a plate and tensioned against the other plate at that comer.

15 Claims, 6 Drawing Figures PATENTEIJMAY 15 ran SHEET 1 [IF 2 iz a x ATTORAAEX/ MOLD FOR CONTINUOUS CASTING F METAL The present invention relates to a mold for continuously casting an ingot, particularly a metal ingot, preferably a steel ingot, whereby the mold cavity is defined by plates held in a frame and tensioned thereto and to each other. The plates are cooled and corner pieces are provided in the regions where plates are joined to establish the mold cavity. This type of molds is known, particularly it is known to establish a mold cavity by means of assembled plates. After a certain period of time the plates have to be reworked because they wear due to mechanical as well as thermal attrition. Reworking the mold walls, however, usually causes a change of the dimensions of the mold cavity, particularly in cross section. In other words, the cross section of the cast ingot will be different after reworking of the walls defining the cavity.

In order to produce a cast ingot of satisfactory quality and particularly in order to avoid rupture of the ingot during cooling as leaving the mold, it is absolutely essential that the ingot leaving the mold be guided in exact conformity to the cross section of the mold cavity. In order to avoid fracture of the edges it is furthermore necessary to round edges of the mold cavity. In particular, mold cavities when assembled from plates for casting ingots of rather large cross sections, particularly for casting slab ingots, usually employs plates having worked in rounded portions. It follows, therefore, that after such plates have been in use for some time reworking of the plates requires also reworking of the rounded portions. Reworking of the rounded corner causes also enlargement of the cross section of the reworked mold, so that the cast ingot is also in this case larger in cross section. Subsequent adjusting of the dimensions of a reworked mold cavity of known construction requires a considerable expenditure of time and this in turn requires a large mold inventory in order to prevent interruption of production.

Molds for continuously casting are known in which plates are joined through transition pieces whereby lateral plates as well as transition pieces are secured to an external frame. In order to obtain a particular tapered construction, it is also known to provide a mold with exchangeable corner pieces of different angles.

The last two types of molds in accordance with known construction, however, have the disadvantages mentioned above, i.e., they change dimensions during reworking. In addition, not only the plates have to be reworked after some time, but subsequently the reworked corner pieces have to be matched to the reworked plates. This, however, has posed considerable difficulties for maintaining a correct rounding and curvature of the corners in the mold and for maintaining also a smooth transition to the adjoining plates. Additional disadvantages result from the fact that there are more elements involved to be reworked. Therefore, there are more gaps and joint areas due to separation of comer pieces and plates defining the mold cavity proper.

Thermal expansion particularly during operation and possible nonuniform thermal expansion in different parts of the mold may cause deformation of those parts of the mold which are placed in abutment but which are not uniform and integral in structure. After cooling and reuse, gaps appear particularly in the region of the level of the molten material in the mold. Metal enters these gaps, solidifies and possibly, increases the existing gaps. Penetration, rupture and other faults in the resulting cast become unavoidable in that case.

A modern steel mill with a wide range for their product line requires differently dimensioned ingots as raw material, particularly for charging rolling equipment. Accordingly, the inventory includes a considerable number of molds to be prepared, maintained and kept ready for operation.

It is an object of the present invention to avoid the several disadvantages outlined above and particularly to provide construction so that the desired relationship between the dimensions of the mold and the ingot guiding system is maintained, even after the mold had to be worked, so that the formation of gaps which may cause rupture of the solidifying ingot can be avoided. It is furthermore an object of the invention to provide particular construction for a mold for continuous casting so that the number of molds to be maintained as inventory can be kept rather small.

In accordance with the preferred embodiment of the present invention it is suggested to employ corner or transition pieces in a mold for continuous casting, there being a corner piece for each pair of angular positioned mold plates. The corner piece is releasably secured to one of the plates of the pair. The adjoining plate, which is the other one of the pair, is positioned for pressure reaction between the plate and the corner piece particularly directly adjacent the mold cavity so that maximum interacting pressure occurs where gap formation is to be prevented the most. The corner piece is secured to one plate of the pair, for example, by means of bolts and/or guiding pins so that the corner piece becomes part of one plate and expands therewith. Gapless abutment of the corner piece and plates therefore remains, even during change in temperature conditions and variable thermal expansion. Therefore there is no deformation between comer piece and plate, and gaps do not form.

Means are provided for edgewise compressing the plates into engagement for establishing the mold, but the compression force is transmitted only through the corner pieces. In case the cross section of the mold is rectangular, for example, for casting slab ingots, there are two long plates and two short cross plates. The two long plates are interconnected outside of the mold through a tensioning device, edgewise compressing the short plates with comer pieces interposed. The transition and comer pieces are preferably provided as part of the plate defining the longitudinal or long dimension of the rectangle. This is particularly advantageous because in case of reworking, matching of the cross plate to the reworked long plate is simpler than matching the long plate to the corner piece.

If the plates have to be reworked, the exchangeable corner pieces connected to them are removed and new ones are substituted. A plate will have its two corner pieces exchanged in that manner. Now the plate, together with newly added corner pieces are reworked so that the reworking inherently includes contour matching between plate and new comer pieces, to maintain a smooth surface for the mold. There remains then only matching of the adjoining plate for pressure interaction with the comer piece as mentioned above. Thus, maintaining the original dimensions of the mold is greatly facilitated. In addition, exchangeability of corner pieces has the following advantage. Comer elements generally are highly amenable to wear and need to be exchanged more frequently. For this reason, and in case there is little or infrequent change of the mold dimensions, the transition and comer pieces should have larger mechanical strength than the plates. This in turn extends the time between reworking.

This is another considerable advantage of exchangeability or corner pieces. Often it is required to cast slab ingots of different cross section. Accordingly, different molds are required and the inventory for molds increases accordingly.'l-lowever, different dimensions for different corner pieces permit establishing different size mold with the same plates. Thus, the plates can be regarded as a basic set for a family of molds and by choosing differently dimensioned corner pieces, ingots of difierent size can be cast.

For example, the distance between two plates facing each other can be made to differ by using comer and transition pieces of different height and/or different length, depending in which direction the dimensions of the ingot are to be changed. In this way, for example, slab ingots of different width and/or different thicknesses can be cast using the same mold plates. More particularly, the corner and transition pieces can be regarded as a continuation of the respective long plate to which they are affixed. The several corner pieces forming an extension of a long plate can be made differently long so that a suitable choice of the length of the corner and transition pieces attached to the same plate permits selection of the long dimension of the slab ingots cross section.

A different height of the corner and transition pieces changes the dimension of the mold in the direction of extension of the cross plates. This in turn is instrumental to change the distance between a pair of facing long plates and to select a particular thickness for the ingot to be cast.

Adjustable molds have been suggested for casting ingots of different width. These molds have cross plates disposed for having an adjustable distance in relation to each other. However, such adjustment and particularly because of tensioning these cross plates between the long plates it was found that the long sides of the long plates can easily be damaged.

Frequent adjusting of the plates defining the smaller dimension of the rectangular cross section of the mold and compression of the plates as provided by tensioning the long plates and additional tensioning as resulting from the thermal expansion can result in damage, for example, in form of indentation in the long plates unless additional measures are taken.

Damage to the long plates can be avoided when comer and transition pieces are used, particularly when the pressure exerted by a pair of long plates upon the cross plates is transmitted only through inserted comer pieces. This is particularly so if the transition and comer pieces are made of a material having a mechanical strength which is lower than the mechanical strength of the plates. For example, the plates defining the mold cavity proper can be made of more or less pure copper and then the transition and comer pieces can be phosphoric-deoxidized copper or electrolyte copper free from oxygen and having been thermally treated. This results also in the advantage that in case of reworking of the cross plates the original distance between the long plates can easily be restored after correspondingly strong inserts have been reinserted.

Pressure interaction between transition and corner piece and plate should occur only in an area directly adjoining the mold cavity. This, in turn, is instrumental in obtaining a lasting joint and it is also instrumental in avoiding formation of gaps between corner piece and adjoining plate. As a consequence the force per unit area of engaging surfaces is rather high. Bevelling is an additional modality for reducing the total surface area of contact so that the pressure, i.e., the force per unit area is correspondingly high, particularly again in the region next to the mold cavity. This is, of course, instrumental in maintaining the cavity closed and for preventing the molten metal from penetrating into any gap.

In order to avoid any deformation of the plate toward which the corner pieces are urged preferably a special spacer bar is interposed between plate and transition and comer piece. For reasons above, corner piece and spacer bar will have a higher mechanical strength than the plates. Bevelling of the spacer bar and/or the transition piece to form a wedge shaped gap reduces the surface area through which pressure is transmitted as between spacer bar and comer piece. The engaging surfaces are in between the wedge-shaped gap and the mold cavity so that the high pressure interaction between spacer bar and corner piece is instrumental in avoiding formation of a gap in the joint.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a horizontal cross sectional view into a portion of a mold for continuous casting and constructed in accordance with the preferred embodiment of the invention;

FIG. 2 is an enlarged portion of FIG. 1 showing particularly a corner ofthe mold; and

FIGS. 3, 4, 5 and 6 illustrate cross sections through different corner pieces in accordance with the preferred embodiment of the invention.

FIG. 1 illustrates a portion of a mold for continuous casting, for example, a slab ingot. The mold is comprised of first plates 1 defining the long dimensions or sides of the rectangle that defines the cross section of mold and slab ingot. There are second plates 2 defining the short sides of that rectangle. Plates 1 and 2 are made of copper and have cooling slots 5. A coolant, for example, water circulates in these slots. Frame or support plates 3 are resiliently forced towards each other by means of tensioning devices such as 6 to force plates 1 and 2 into edgewise engagement. In each comer where a cross plate 2 meets a long plate 1 there is interposed a corner and transition piece 8. The corner pieces are exchangeably secured to plates 1 and provide pressure towards and against the adjoining cross plate 2. The plates 1 and 2 together with corner pieces 8 establish the mold cavity 9.

The corner construction is illustrated in greater detail in FIG. 2 showing in particular and on an enlarged scale further details of a comer piece 8 of the mold shown in FIG. 1. Corner and transition piece 8 is placed in an insert of plate 1 and bolted thereto by means of a pin bolt 10. Therefore, corner piece 8 constitutes in effect a portion of plate 1 serving as a fillet to continue plate 1 as a wall defining portion of the mold cavity. However, releasing of bolt 10 makes comer piece 8 removable. The smooth curved surface contour of the corner piece continues the mold cavity surface to the line or edge where comer piece 8 meets cross plate 2. A joint region 11 is thus established between plate 2 and corner piece 8 adjacent to and extending transverse from mold cavity 9. Pressure is transmitted upon plate 2 across the surface area of contact between corner piece 8 and a recessed edge of plate 2, there being a gap 12 between plates 1 and 2 outside of corner piece 8.

FIG. 3 illustrates a corner of a mold with inserted corner pieces 8' whereby in particular corner piece 8 bears against plate 2 only in a narrow surface region 7 of mutual engagement and which covers approximately one third of the thickness of plate 2. The surface portion of corner piece 8 facing the edge of plate 2 has a bevelled portion to define a wedge shaped gap. The small area of engagement between corner piece 8 and plate 2 for pressure transmission thus extends between mold cavity 9 and gap 14.

A different embodiment is illustrated in FIG. 4, differing from the one in FIG. 3 in that a bar 13 is interposed between plate 2 and corner piece 8". This bar has a bevelled portion where facing and engaging corner piece 8" to establish wedge-shaped gap 14 facing away from the mold cavity 9. Pressure is, therefore, exerted by corner piece 8" upon the bar 13 in a very narrow portion where engaging the bar while a broad surface contact exists between plate 2 and bar 13. Therefore it is advisable to use a harder material for bar 13 and comer piece 8 than for plates 1 and 2, i.e., mechanical strength of elements 13 and 8 is to be higher. In particular a hard copper alloy is suggested here such as an age-hardened copper alloy.

FIG. 5 illustrates another embodiment whereby in particular a corner piece 8" is provided for a mold with rectangular cross section. An adjustable position for the cross plates 2 (or at least one thereof) is contemplated here. Piece 8 in this case is inserted in plate 2 and secured thereto to constitute a unit. In other words, for this embodiment corner piece 8 is secured to cross plate 2 to form a continuation thereof. The comer piece is forced against the long plate 1. The double arrow 16 illustrates adjustability of the position of plate 2 with attached comer piece 8" relative to the surface of plate I particularly as facing the mold cavity 9. Therefore, there is a particular basic mold established with variable cross sections for casting and as resulting from displacement of adjustable plate 2. This is of particular advantage as the advantages of separate comer pieces such as 8" are still maintained.

In either embodiment the height of a corner piece measured relative to plate 1, i.e., the height of at least two corner pieces as attached to or cooperating with the same long plate can be selected differently for establishing differently wide molds. This may be provided in addition to adjustability of plate 2 so that another variant of this embodiment is adjustability of thickness of the cast ingot. The material for the corner piece 8" can in this case be provided at a lower mechanical strength than the plates defining the mold.

Turning now to FIG. 6, there is illustrated another embodiment of the present invention illustrating that the comer piece such as 8" may have particularly selected length to form an extension of longitudinal plate 1. Differently long comer pieces thus permit selection of difierent long dimensions for a slab ingot. Corner piece 8' is secured to plate 1, still maintaining rectangular shape of the mold cavity but being exchangeable. In this case the connecting area has inclined faces 17; particularly there is an inclination relative to the inner surface plate 1 as defining mold cavity 9.

By selecting different width andother different dimensions for the corner pieces, one can control, within limits, the cross section of the ingot to be cast. All these variations for such corner pieces in effect make it possible that with basic plate elements and differently dimensioned corner pieces a large variety of molds can in effect be established without requiring different complete molds for each differently sized slab ingot.

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included.

We claim:

1. Mold for continuous casting of metal, comprising:

a plurality of plates positioned to define the mold cavity and having surfaces for direct exposure to the mold cavity, there being means for cooling the plates;

means for retaining the plates in a particular, mold defining position relation in mutual disengagement, so that a gap exists between respective adjoining two of said plates;

a plurality of corner elements one each per respective two adjoining plates and separable from both said plates, a corner element of the plurality provided for cooperation with a first and a second plate of the plurality in the respective gap between them, the first and second plates arranged transverse to each other, the corner element being releasably secured to the first plate to form a mold cavity defining surface continuation thereof and extending into said gap; and

means including the retaining means acting on the first plate and in the back of the corner element for urging the corner element against the second plate at a first joint therewith, independently from the securing of the corner element to the first plate, and normal to the first joint so that position retaining pressure force as between the first and second plate is transmitted, for sealing the first joint between the second plate and the corner piece, at least essentially exclusively through the corner element, there being at least a surface portion of mutual engagement and providing a second joint between the corner element and the first plate on which the clamping force acts also normal to the second joint for sealing the second joint.

2. Mold as set forth in claim 1, there being four plates arranged to define a mold of quadrangular cross section, there being four corner elements accordingly, the corner elements being releasably secured to two oppositely positioned ones of the four plates, the dimensions of the corner elements respectively perpendicularly to the plates of the two plates determining the dimension of the cavity in the direction of extension of the other two plates.

3. Mold as set forth in claim 1, the corner element having mechanical strength difierent from the mechanical strength of the plates.

4. Mold as set forth in claim 3, the comer element being made of an age-hardened copper alloy, the plates being made of copper.

5. Mold as set forth in claim 3, the corner element being made of heat treated copper, having lower mechanical strength than the plates, the plates being made of copper.

6. Mold as set forth in claim 3, the corner element being made of a heat treated copper alloy, having lower mechanical strengtlh than the plates, the lates being made of copper.

7. old as set forth in c aim l, the second plate bearing against the comer element at a surface area of mutual engagement directly adjacent the mold cavity.

8. Mold as set forth in claim 7, the surface area of contact as extending in the direction of plate thickness of the second plate having dimension of about one third of the plates thickness.

9. Mold as set forth in claim 8, at least one of the remaining, nonengaging surface areas of second plate and of the corner element being bevelled.

l0. Mold as in claim 1, there being a bar interposed between the second plate and the corner element and compression forces between the first and second plate having transmitted through the bar as interposed between second plate and corner element.

11. Mold as set forth in claim 10, the bar and corner element having higher mechanical strength than the first and second plates.

12. Mold as set forth in claim 10, at least one of the bar and of the comer element having a bevelled surface to form a gap, the bearing area of engagement between corner element and bar being between the gap and the mold cavity.

13. Mold as set forth in claim 1, the corner element releasably bolted to the first plate.

14. Mold as set forth in claim 1, wherein at least parts of the joints are aligned and normal to the clamping force provided by the last means and acting edgewise into the second plate.

15. Mold as set forth in claim 14, the first plate having a recess, receiving the corner element, the second joint established in the bottom of the recess on which the corner element sits.

being

Claims (15)

1. Mold for continuous casting of metal, comprising: a plurality of plates positioned to define the mold cavity and having surfaces for direct exposure to the mold cavity, there being means for cooling the plates; means for retaining the plates in a particular, mold defining position relation in mutual disengagement, so that a gap exists between respective adjoining two of said plates; a plurality of corner elements one each per respective two adJoining plates and separable from both said plates, a corner element of the plurality provided for cooperation with a first and a second plate of the plurality in the respective gap between them, the first and second plates arranged transverse to each other, the corner element being releasably secured to the first plate to form a mold cavity defining surface continuation thereof and extending into said gap; and means including the retaining means acting on the first plate and in the back of the corner element for urging the corner element against the second plate at a first joint therewith, independently from the securing of the corner element to the first plate, and normal to the first joint so that position retaining pressure force as between the first and second plate is transmitted, for sealing the first joint between the second plate and the corner piece, at least essentially exclusively through the corner element, there being at least a surface portion of mutual engagement and providing a second joint between the corner element and the first plate on which the clamping force acts also normal to the second joint for sealing the second joint.

2. Mold as set forth in claim 1, there being four plates arranged to define a mold of quadrangular cross section, there being four corner elements accordingly, the corner elements being releasably secured to two oppositely positioned ones of the four plates, the dimensions of the corner elements respectively perpendicularly to the plates of the two plates determining the dimension of the cavity in the direction of extension of the other two plates.

3. Mold as set forth in claim 1, the corner element having mechanical strength different from the mechanical strength of the plates.

4. Mold as set forth in claim 3, the corner element being made of an age-hardened copper alloy, the plates being made of copper.

5. Mold as set forth in claim 3, the corner element being made of heat treated copper, having lower mechanical strength than the plates, the plates being made of copper.

6. Mold as set forth in claim 3, the corner element being made of a heat treated copper alloy, having lower mechanical strength than the plates, the plates being made of copper.

7. Mold as set forth in claim 1, the second plate bearing against the corner element at a surface area of mutual engagement directly adjacent the mold cavity.

8. Mold as set forth in claim 7, the surface area of contact as extending in the direction of plate thickness of the second plate having dimension of about one third of the plate''s thickness.

9. Mold as set forth in claim 8, at least one of the remaining, nonengaging surface areas of second plate and of the corner element being bevelled.

10. Mold as in claim 1, there being a bar interposed between the second plate and the corner element and compression forces between the first and second plate having transmitted through the bar as interposed between second plate and corner element.

11. Mold as set forth in claim 10, the bar and corner element having higher mechanical strength than the first and second plates.

12. Mold as set forth in claim 10, at least one of the bar and of the corner element having a bevelled surface to form a gap, the bearing area of engagement between corner element and bar being between the gap and the mold cavity.

13. Mold as set forth in claim 1, the corner element being releasably bolted to the first plate.

14. Mold as set forth in claim 1, wherein at least parts of the joints are aligned and normal to the clamping force provided by the last means and acting edgewise into the second plate.

15. Mold as set forth in claim 14, the first plate having a recess, receiving the corner element, the second joint established in the bottom of the recess on which the corner element sits.

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