US3072981A

US3072981A - Hot top casing for casting molds

Info

Publication number: US3072981A
Application number: US861098A
Authority: US
Inventors: Davidson Per
Original assignee: Sandvik AB
Current assignee: Sandvik AB
Priority date: 1958-12-23
Filing date: 1959-12-21
Publication date: 1963-01-15
Anticipated expiration: 1980-01-15

Description

Fig. 3

P. DAVIDSON HOT TOP CASING FOR CASTING MOLDS Filed Dec. 21, 1959 Jan. 15, 1963 superior qualities. hot top includes a firm and relatively thin casing consist- United-States Patent Or This invention relates generally to casting molds used in the casting of steel and other metals and more particularly to a hot top casing structure adapted for use with ingot casting molds.

For a long time there has been a need in the casting hot top art for a mold casing material which meets the requirements of good heat insulation, good form resistance and low manufacturing cost. While various types :of hot top casings have been provided in the past, these have been specifically designed to provide roughened sinkhead surfaces on the cast ingot so that the ingot may be suitably gripped by the tongs of lifting cranes.

An object of the present invention is to provide a cast- .ing mold hot 'produces an ingot the sinkhead of which has smooth surfaces so that-the sinkhead part of the ingot may be used during subsequent ingot treatment rather than being wasted as inthe past.

top casing of simple construction which Another object of the invention is to provide a hot top which results in orientation of the arising pipes and liquations extending upwardly in the ingot so that the portion of the ingot being returned as scrap during subsequent ingot treatment is minimized.

According to the present invention it is possible to manufacture, at low cost, casting mold hot tops having In accordance with the invention the ing of an organic fibrous material, a fireproof material, and a binder, which casing is characterized in that it consists by weight of not less than 2% and not more than 20% (preferably not more than 15%) organic fibrous material, 4l0% binder, and the remainder fireproof ma j terial. For the organic fibrous material it has been proven advantageous to use paper pulp, waste paper or the like-'e.g., mechanical pulp or a pulp of waste paper or the like possibly with an addition of chemical pulp. As fireproof material may be used quartz, sand or another silicate; in some cases basic materials as burned dolomite, cinders, or the like may be used. In the fireproof material may also be included upto by weight of a fireproof fibrous vmaterial such as asbestos. The binding medium may beorganic or inorganic. Of the first type there may be .mentioned glue, such as synthetic glue (e.g. syntheticresins or silicone resin), glue manufactured from animalor vegetable raw materials (cellulose glue). Of the latter type may be mentioned fireproof cement or silicate of potassium (water glass). The casing may be completely or partly surrounded by an insulated volume of air or by a heat insulating material such as sand, bricks or the like.

It has been shown that hot top casings in accordance with the invention are relatively inexpensive to manufacture, have good storing and form resistance properties, good insulation qualities, and achieve smooth surfaces of the cast metal. For example, during the manufacture of a steel ingot with the use of hot top casings in accordance with the invention the sinkhead obtains a smooth surface as the pipes or liquations are concentrated in its uppermost part. This is of great economical importance, since only a very small part of the steel in a sinkhead has to be returned as scrap.

Other objects and advantages of my invention will ice become apparent from a study of the following specification when considered in conjunction with the accompanying drawings in which:

FIG. 1 is a vertical section of the hot top casing taken along line 11 of FIG. 2;

FIG. 2 is a plan view of the hot top casing;

FIG. 3 is a sectional view taken through the mold and hot top;

FIG. 4 is a detailed sectional view of another embodiment of the invention; and

FIGS. 5-7 are detailed sectional views of other hot top constructions.

As shown in FIGS. 3-5, the hot top casing 13 tapers upwardly and inwardly and is supported at its lower edge on the shoulder portions 16 of the wall of the ingot mold 12. It is also possible, however, to place the hot top casing upon the upper circumferential surface of the ingot mold opening. As mentioned above the casing consists by weight of 220% (preferably 2-15%) organic fibrous material, 4-l0% binder, and the remainder fireproof material. As especially preferred limits there may be mentioned 25-13% by weight organic fibrous material and 4.5-9% binder. Possibly also smaller quantities of other materials may be included. As examples of organic fibrous materials of suitable consistency may be mentioned paper pulp, waste paper or the like (e.g. mechanical pulp or pulp manufactured from waste paper, possibly having an addition of chemical pulp). The suitability of the mentioned fiber pulp for thispurpose is that the bin-ding of the usually granular and/ or powder-formed fireproof material (e.g. quartz) is facilitated, and also the casing is given a porosity which substantially increases its insulation qualities. It has also been shown that injurious gas formation is avoided by the use of the casing when theabove mentioned contents of the fibrous material are included.

As fireproof material, quartz or quartzite may be suitably used. Also other fireproof materials such as sand, certain other silicates, basic materials as burned dolomite and cinders and the like may be used. If desired one may use up to about 10% (preferably 04%) by weight fireproof fiber material (as for example asbestos) mixed in the usually granular and/or powder-formed fireproof material. The medium grain size for the fireproof material is to be below 1 mm., preferably below 0.3 mm. and often below 0.2 mm. Suitable limits for the medium grain size may be 0.6-0.05 mm. The grain size may be stated as being below mesh, preferably below 45 mesh.

The binder in the casing may be glue, such as synthetic glue, e.g. synthetic resin or silicone resin, or glue manufactured of animal or vegetable raw materials such as cellulose glue. Usually a sufficient quantity of binder is added to achieve satisfactory strength. In certain cases instead of the above mentioned binder an inorganic binder such as fireproof cement or water-glass may be used.

As examples of suitable material compositions for the casing in accordance with the invention may be mentioned the following:

(1) Mass or pulp composed by waste paper and/or other mechanical pulp, possibly mixed with some smaller quantities of chemical pulp, total 242% by weight, synthetic resin, glue or the like, 58% by weight, and the remainder fireproof material, preferably quartzite powder and/ or the like.

(2) Paper pulp and/or waste paper, 2-8% by weight, glue 5'8% and the rest consisting of fireproof material.

(3) Paper pulp -3-12% by weight (preferably about 3%), asbestos 0.4% (preferably above 0%), glue 5-8% and the rest fireproof material.

As shown in FIGS. 1-2, the hot top casing 13 is formed angle of 2-15, .preferably 2-10.

of course. be supportedby an outer casing and its lower edge may during rolling; the ingot is materially. reduced.

12 (FIG. 3

The shoulder surface 16 is inclined to the vertical at an For small diameter variationsbetween the ingot molds of the same type and size the casing will be applied in such a way upon the ingot mold that the total volume included in the casing and ingot mold (and thus the .ingot weight) will be substantially constant.

In the embodiment of FIG. 3, the inner .wall portions of the ingot mold below and above the shoulder portion 16 may be formed with surfaces slightly inclined to the vertical and also to the surface of shoulder portion 16. The space-14 between casing 13 and upper part 17 of the ingot mold is filled with sand, bricks or another. insulating material. It is naturally also possible to effect mold insulation by enclosing air in a suitable manner in the space 14.- Before or after the application of the casing ,it may be desirable to apply a sealing medium, such as asbestos, putty, wood wool, straw, glass wool or the like on or close to the contact surface of the ingot mold and the casing 13 as at 15, 16.

In .FIG. 4 is shown an embodiment in which the ingot mold .12terminates atits upper end adjacent the shoulder portionl. .Above the ingot mold is placed an outer casingt19 of aninsulating material, such as insulating bricks, surrounded by an outershell 20, and this outer casing 19 laterally supports the outer surface of the hot top casing. Betweenthe outer casing 19: andthe hot top casing 13 is arranged a space 14.

Other modifications of the hot top casing are possible, The outer surface of the hot top casing may extend'into the upper portion of the ingotmold. In FIG. is shown a hot.top, corresponding with that of FIG. '3, at the upper portion of which is provided a cover 18 above. the space 14, which space is filled with insulating ,.material, such as bricks.

The hot top casing 13 has been illustrated in FIGS. l,6 as tapering upwardly ,and inwardly toward the center of the ingot mold, but the casing may also have substantially vertical walls as illustrated in FIG. 7.

,A hot top casing formed in accordance with FIGS. 1-5 and' 7 with or Without the last mentioned cover provides the great advantage that steel or the like from the bloom 'does not to any substantial degree penetrate between the casing and the innerwall of the ingot mold, on account of whichthe risk of hot cracks in the outer layer of the ingot in connection with the stilfening of the ingot is avoided. ,Further .there is obtained a smooth travel bef. tween hot top and ingotmold and in the ingot the forma tion of pads or any other protuberances is avoided, which flaws ordinarily would have been impossible to remove consequently, the percentage of scrap in In. the embodiments describedabove with reference to :FIGS. 1-5 and 7, thelower extremity of the casing 13 is tapered and the outer surfaceof the tapered portion inclined surfaces 22 joined by a common edge 23, which surfaces are contiguous with the walls of a corresponding ledge in the inner wall of the mold.

The thickness of the casing (13, 21) above the lower end supporting surface or surfaces (15, 22) is generally constant and preferably between 5 and 15 mm. For a 1.7-ton ingot the casing thickness should be approximately 12 mm. 7

While in accordance with the patent statutes I have illustrated and described the best forms and embodiments of my invention now known to me, it will be apparent to those skilled in the art that other changes may be made in the apparatus described without deviating from the invention as set forth in the following claims.

I claim:

1. A hot top casing for an ingot casting mold consisting of a molded mixture of from 2 to 15% by weight of a fibrous organic material, 4 to 10% by weight of a binder, up to 4% by weight of an inorganic fibrous material and the remainder consisting essentially of a granular fire proof material which is not disintegrated by the heat to which it is subjected in use selected frornthe group consisting of quartz, sand, refractory silicates, burned dolomite and cinders, said granular fireproof material having a medium grain size within the range from 0.6 to 0.05 mm. and said casing beingrelatively thin andhaving asmooth inner surface.

2. A hot top casing as defined in claim 1 wherein said binderis an organic glue.

3. A hot top casing asdefined in claim 1 wherein said fireproof material is quartz.

4. A hot top casing as defined in claim 1 wherein said organic fibrous material includes cellulosic fibers less than 8% by weight, and said binder includes glue in the range of 48%.

5. A hot top casing as defined in claiml in which the percentage of fibrous organic material is within the range from 2.5% to 13%.

6. A hot top casing for an ingot casting mold consist: ing of a molded 'mixture of from 2 to 15% by weight of a cellulose fibrous organic material,.4 to 10% by weight of aresin binder, up to 4% by weight of an inorganic fibrous material and the remainder consisting essentially of a granular fireproof material which is not disintegrated by the heat to which it is subjected in use consisting of refractory silicate containing material, said granular firetively thin and having a smooth inner surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,696,986 Trembour .'Ian. 1, 1929 1,795,011 :Cross .Mar. 3,.1931 1,819,364 Firth et a1. Aug.. 18, 1931 2,148,583 .Rowe Feb. 28,1939 2,231,813 McDonald Feb. 11,1941 2,272,018 Nicholas .'Feb. 3, 1942 2,462,255 Charman et a1 Feb. 22, 1949 2,678,481 Peterson .May 18, 1954 2,952,055 Gottschalk Sept. 13, 1960

Claims

1. A HOT TOP CASING FOR AN INGOT CASTING MODE CONSISTING OF A MOLDED MIXTURE OF FROM 2 TO 15% BY WEIGHT OF A BINDER, A FIBROUS ORGANIC MATERIAL, 4 TO 10% BY WEIGHT OF A BINDER, UP TO 4% BY WEIGHT OF AN INORGANIC FIBROUS MATERIAL AND THE REMINDER CONSISTING ESSENTIALLY OF A GRANULAR FIREPROOF MATERIAL WHICH IS NOT DISINTEGRATED BY THE HEAT TO WHICH IT IS SUBJECTED IN USE SELECTED FROM THE GROUP CON SISTING OF QUARTZ, SAND, REFRACTOR SILICATES, BURNED DOLOMITE AND CINDERS, SAID GRANULAR FIREPROOF MATERIAL HAVING A MEDIUM GRAIN SIZE WITHIN THE RANGE FROM 0.6 TO 0.05 MM. AND SAID CASING BEING RELATIVELY THIN AND HAVING A SMOOTH INNER SURFACE.