US3092883A

US3092883A - Tightening device for hot tops

Info

Publication number: US3092883A
Application number: US196085A
Authority: US
Inventors: Ednell Daniel Fredrik
Original assignee: Sandvik AB
Current assignee: Sandvik AB
Priority date: 1961-05-25
Filing date: 1962-05-21
Publication date: 1963-06-11
Anticipated expiration: 1980-06-11

Description

June 11, 1963 EDNELL 3,092,883

TIGHTENING DEVICE FOR HOT TOPS Filed May 21, 1962 3 Sheets-Sheet 1 June 11, 1963 D. F. EDNELL 3,

TIGHTENING DEVICE FOR HOT TOPS Filed May 21, 1962 5 Sheets-Sheet 2 June 11, 1963 D. F. EDNELL TIGHTENING DEVICE FOR HOT TOPS 3 Sheets-Sheet 3 Filed May 21, 1962 United States Patent 3,092,883 TIGHTENING DEVICE FOR HOT TGPS Daniel Fredriir Ednell, Ed, Sweden, assignor to Sandvikens Jernvcrks Ahtiebolag, Sandviken, Sweden, a corporation of Sweden Filed May 21, 1962, Ser. No, 196,085 Claims priority, application Sweden May 25, 1961 13 Claims. (Cl. 22-147) The present invention relates to a tightening device for hot tops for ingot molds or similar casting molds, said hot tops consisting of relatively thin heat insulating slabs intended to be placed adjacent to and against the upper part of the inner walls of the mold.

A hot top is used for ingot mold castings in order to delay the stiffening of the top portion of the ingot after the molten metal has been poured into the mold, thus limiting or avoiding segregations and pipes as high up in the ingot as possible. The hot top should be easy to apply and should cause as little influence as possible on the metal from gas formation, intrusion of foreign substances or the like. It should have a good heat insulation and mechanical strength and be positioned in such a way that it is firmly supported during the casting. At the lower edge of the hot top the sealing against the mold must be .good in order to prevent metal from intruding between the hot top and the walls of the mold thus forming fins which are of substantially disadvantage in the rolling of the ingots. It is also desirable that the hot top is durable during storage, requires little storage space and can be used without extra drying.

The present invention aims especially at the achieving of a good tightening of the lower edge of the hot top against the mold wall. It is characterized by the feature that a member in the form of a frame, plate or the like is placed resting at its periphery against inwardly and downwardly inclined portions of the hot top slabs situated near the lower edges of the slabs on the sides of the slabs which face the interior of the mold. The frame or plate, by its weight, urges the said inclined portions together with the lower edges of the slabs outwardly and holds said edges in contact with the walls of the mold and moves upwardly, floating on the rising surface of the molten metal, after the said rising surface has reached the lower edge of the hot top.

The following description explains the invention in connection with a few embodiments thereof illustrated in the accompanying drawings in which FIG. 1 is a vertical sectional view of the upper end of an ingot mold showing a hot top and frame or plate in operative position therein,

FIG. 2 is a top plan view of the assembly shown in FIG. 1,

FIG. 3 is a vertical sectional view similar to FIG. 1 but showing the frame (left half) and plate (right half) in their raised positions,

FIG. 4 is a vertical sectional view similar to FIG. 1 showing in the left and right halves two modifications of the frame and plate,

FIGS. 5, 6 and 7 are a horizontal sectional view, a vertical sectional view and an enlarged fragmentary sectional view of an embodiment of the invention designed for use in ingot molds which are of a relatively long and narrow horizontal cross section, and

FIG. 8 is an enlarged fragmentary sectional view of the embodiment shown in FIG. 1.

In FTGURE 1, 1% is the upper part of an ingot mold. A hot top is situated along the inside walls of the mold. The hot top consists of slabs 1f hanging on the upper surface of the mold it by aid of flanges 12. The slabs are interconnected by wedges 13, which have contact with ice the slabs along contact surfaces 14. The lower edge portions of the slabs are formed with an inward projection 15 having an upper downwardly and inwardly inclined surface 16 and a lower downwardly and outwardly inclined surface 17. The slab terminates at a surface 18 which is in contact with the ingot mold. The inward projection 15 may consist of a continuous ridge along the lower edge portion of each slab, or it may be divided into a number of separate projections, lugs or the like. Inside the projection 15 there is, as more clearly appears from FIG. 8 a space 19 between the slab and the mold. in this way the slab has the same thickness in the projection 15 as the remainder of the slab. it is of course also possible to make the slab straight at the side facing the mold as indicated in FIG. 7, in which case the projection or projections 15 will form portions which are thicker than the rest and the space 19 will be absent.

As shown in FIGURE 1 a frame 2&- is resting with its outer edges against the upper sloping surfaces 16 of the projections 15 of the slabs 11. The frame is of the same shape but slightly smaller than the cross section of the hot top. The outer edge of the frame is situated at the vertical lines 23. When the frame rests on the surfaces 16 it presses by the wedge effect exerted by its own weight the contact edges 18 of the slabs into contact with the mold. As the molten metal rises a pressure is applied against the lower part of the hot top by the metal engaging the surfaces 17 before the metal surface reaches the frame 26. When the metal surface reaches the frame 26} the latter floats on the metal and is lifted by the same along the lines 23 as the casting proceeds. it is to be noticed that the tightening pressure exerted by the frame on the lower edges of the slabs is not released until the metal has reached the said lower edges and has begun to press them outwardly. The frame may be strengthened by a reinforcement as an iron 22 (see FIG. 2). 21 designates the edge of the opening in the frame.

FIGURE 3, left part, shows the same structure as FIG- URE 1 but with the frame 2%) in raised position. The right part of the FIGURE 3 shows a plate 24, which covers the opening of the mold. This plate can be provided with relatively small holes (not shown) in order to let out air or gases trapped by the rising molten metal. Such a plate can be used when the molten metal is brought into the mold at the bottom of the mold. The advantage of it is that it gives a better heat insulation than a frame with a large opening in its centre. If the metal is to be poured into the mold from above the frame shown in FIGURES 1 and 2 must be used.

FIGURE 4 shows another embodiment of the frame and plate with an upstanding flange in order to improve the floating ability of the frame and plate. The left part of the figure shows a frame 25 with inner and outer flanges 26 and *a central opening 27 for pouring the metal from above, while the right hand part of the figure shows a plate 28 without a central opening for casting from below but a flange 29.

In FIGURES 57 is shown a modification of a hot top with a frame intended for ingot molds with a narrow and long horizontal cross section. There are no separate wedges in the corners of the hot top as in the embodiments shown in FIGS. 1-4, but the shont end slabs 50 are formed as wedges, which press the long side slabs 51 outwardly along

contact surfaces

57 and 58. In cross section the contact surfaces may be convergent towards the interior of the mold as shown at 57 or parallel as shown at 58. There are no separate inward projections on the slabs 51 but their whole inside surfaces 53 are inclined. The frame 52 rests against these inclined surfaces. There may be reinforcing parts 56 connecting the opposite long sides of the frame leaving the opening 54,

and the frame may be parted as shown at 55 into two or more sections. The lower edges 60 of the slabs are inclined in order to provide an ingot surface that is more suitable for rolling- On the side situated towards the wall of the mold there may be a special sealing rim 59 as shown in FIG. 7.

if the mold is used for casting from the top the opening in the frame has to be sutficiently large for pouring the molten metal, but if the casting is performed from the bottom the frame can be substituted by a plate like that shown in FIG. 3 which, if necessary, may have a hole only sufiicient to let out the air and gases as the casting proceeds.

FIG. 8 shows in larger scale a detail of the embodiment according to FIGURES 1 and 2. As can be seen in this figure the part 15a of the lower portion of the slab projects beyond the line of the surface of the slab 11 which faces the mold 10. In this way a good sealing is secured at the lower edge of the hot top so that fins at this part of the ingot are avoided.

If the invention is used in connection with hot tops Without a special sealing rim or ridge protruding beyond the remainder of the surface of the slab as shown at 15a and 59, the tolerances of the slabs should be such that the lower edge with cetaint'y has contact with the mold. In order to achieve this it is possible to make the surface of the slabs facing the mold wall slightly concave. The projections 15 may be continuous along the whole slab but may also consist of a number of projections, lugs or the like separated from each other and having inclined surfaces 16 in order to achieve the wedge effect from the frame or plate.

As explained above the invention can be used for casting from below or from above. It is possible to use the invention for ingots which are wider at their upper ends as well as for ingots which are smaller at their upper ends. In the latter case it is of course important that the projections 15 are so large that the frame can be small enough to have free passage upwardly along the lines 23. a

The invention is useful in connection with hot tops of several known materials but has been found especially useful for hot tops which consist of a major amount of finely divided refractory material and a minor amount of finely divided organic material as, e.g., paper pulp and a glue. As a suitable composition may be mentioned 82-94% fine gnained fireproof material as quartz, olivine or the like, 39% cellulose fiber, especially paper pulp or the like and 18% of a synthetic resin glue. It is also suitable to add up to of asbestos, rock wool or some other fibrous fireproof material to this composition. The average grain size of the main part of the fine grained refractory material should be within the range 0.2-0.02 mm. This composition fills the general requirement of a hot top as it has a very good heat insulation and has a good storing permanency and requires comparatively small storage space. It also fills the special requirement of the present invention, as it gives a good sealing at the contact surface between the hot top and the mold. The material in the frame may be the same as in the rest of the hot top, but of course also different materials may be used in the frame and in the hot top. The specific weight of the frame must of course be smaller than that of the metal as the frame otherwise could not fioat on top of the molten metal.

The hot tops according to the invention can be used also for other mold sections than the rectangular or square sections illustrated as for instance circular and corrugated sections. The hot top has only to be given a shape corresponding to the section of the ingot mold.

The thickness of the slabs of the hot top suitably varies with the size of the ingot. For an ingot weight of 1.7 tons and upper dimensions of 50 x 50 cm. a slab thickness of -12 man. has been found to be suitable. For

4 a 7 ton ingot having upper dimensions of 60 x 70 cm. a slab thickness of 20-25 mm. is suitable. In general the thickness should lie within the limits 10-25 mm. The frame or plate can suitably have approximately the same thickness as the sla'bs, at least if it is made from the same material.

In order to further delay the solidification of the ingot the slabs and the frame or plate may be coated with an exothermic material. It is common in casting ingots to pour an exothermic material on top of the cast metal in order to delay the solidification. If a covering plate of the type shown at 24 in FIGURE 3 or at 28 of FIGURE 4 is used it is not possible to pour an exothermic material in the usual way on the surface of the metal but then the exothermic material can be applied to the underside of the plate.

The above description does not define the limits of the invention but gives only examples of the invention within the scope of the following claims. 1

I claim:

1. A hot top for-casting molds comprising heat insulating slabs positioned adjacent to the inner surfaces of the.

wall of the mold adjacent the upper end thereof, said slabs having inwardly and downwardly sloping irmer surfaces at least adjacent to the lower edges thereof, and a tightening member positioned horizontally between said slabs and resting with its edges in contact with said sloping surfaces thereby urging said slabs against the inner surfaces of the mold when the mold is empty, said mem-- her being tloatable upon the molten metal and having smaller dimensions than the inner horizontal dimensions of said hot top at all levels above that at which it engages said sloping inner surfaces.

2. A hot top as defined in claim 1 in which said mema of molten metal into the mold.

6. A hot top as defined in claim 5 in which said flat strip is provided with upwardly extending flanges adjacent to all edges thereof.

7. A hot top 43S defined in claim 1 in which said member is provided on its lower face with a layer of exothermic material.

8. A hot top as defined in claim 1 in which said slabs are provided with flanges extending outwardly from the u upper edges thereof resting upon the upper surface of the mold and to suspend the slabs in the mold.

9. A hot top as defined in claim 1 in which the inner surfaces of the slabs are inclined inwardly and downwardly continuously from the upper to the lower edges thereof.

10. A hot top as defined in claim 1 in which each slab is provided with a projection adjacent to the lower edge '13. A hot top as defined in claim 1 in which \the lower edge surface of each slab slopes outwardly and downwardly.

References Cited in the file of this patent UNITED STATES PATENTS 2,390,373 Jones et a1 i Dec. 4, 1945 2,462,256 Charm-an at al Feb. 22, 1949 2, 77 Marburg many-""5.- Mat. 29, 1949

Claims

1. A HOT TOP FOR CASTING MOLDS COMPRISING HEAT INSULATING SLABS POSITIONED ADJACENT TO THE INNER SURFACES OF THE WALL OF THE MOLD ADJACENT THE UPPER END THEREOF, SAID SLABS HAVING INWARDLY AND DOWNWARDLY SLOPING INNER SURFACES AT LEAST ADJACENT TO THE LOWER EDGES THEREOF, AND A TIGHTENING MEMBER POSITIONED HORIZONTALLY BETWEEN SAID SLABS AND RESTING WITH ITS EDGES CONTACT WITH SAID SLOPING SURFACES THEREBY URGING SAID SLABS AGAINST THE INNER SURFACES OF THE MOLD WHEN THE MOLD IS EMPTY, SAID MEMBER BEING FLOATABLE UPON THE MOLTEN METAL AND HAVING