US3076239A

US3076239A - Ingot mold hot top structure

Info

Publication number: US3076239A
Application number: US862407A
Authority: US
Inventors: Davidson Per
Original assignee: Sandvik AB
Current assignee: Sandvik AB
Priority date: 1958-12-30
Filing date: 1959-12-28
Publication date: 1963-02-05
Anticipated expiration: 1980-02-05

Description

Feb. 5, 1963 P. DAVIDSON meow MOLD HOT TOP STRUCTURE Filed Dec. 28, 1959 INVEN TO R- BY i .WWIWM rm ATTORNEYS.

United States Patent PersDavidson,Saudvikcn, Sweden, assignonto Sandvikeus Jernverks; Aktiebolag sandviken, Sweden; a corpora.

tion of Sweden Filed Dec. 28, 1959, Ser. No. 862,407 Claimspriority, application-Sweden Dec. 30, 1958 1 Claim. (Cl. 22-147).

This t inventionrelates to hot tops for ingot. casting molds, andv more particularly to. an ingot casting mold structure having at least one mold cavity section the di-,

mensions of which progressively increase upwardly.

In ingot casting molds it istdesirable that good tight-..

ting against the walls of the mold, low manufacturing.

cost, and simplified construction. A. tight fitting of the hot top within the mold Walls is necessary to prevent the metal which is to be cast from being, forced out the joint and to prevent transverse hot cracks from arising during stiflening, andalso to prevent said falls from appearing along the ingot side. In view of the difiiculties in obtaining a smooth junction between the hot top and the mold,-major-flaws are ordinarily introduced which are impossible to eliminate without causing a large amountof the ingot top portion to be returned as scrap.

Another drawback has been the difficulty in obtaining uniform ingots due to the lack of exactness in the diameter ofthe inner walls of the mold, resulting in variations in ingot weights upon inconsistency in volume measures. Another factor causing the ingot variation could also be a burn-outin the bottom of the mold cavity.

Thepresent invention was developed to avoid the disadvantages presentedby the ingot casting molds of the'prior taken through the longitudinal axis of the ingot mold is smaller than the largest and larger than the smallest widths of the inner wall of the above-mentioned ingot mold section. By'so arranging the hot top casing it is possible to eliminate hot cracks which form during hardening of the ingot. Another advantage of sucha hot top structure is that for a certain variation in volume of the ingot mold-due, for example, to. diameter variations from nominal measure-the hot top will sink to another level than ifithe diameter of the upper portion of the ingot mold should have been normal; In this manner the ingot weight will also be kept substantially constant for certain volume variations in the ingot mold, for example, through a greater sinking of the hot top at increased diameter. By a suitable choice in material the manufacture of the hot top casing becomes relatively inexpensive, good heat insulation of the sinkhead will be obtained, and very close measure tolerances will be provided. By a proper choice of inclination angle a good regulation of substantially constant ingot weight maybe obtained by means of the variable height of the hot top casing along the inclined ingot mold walls. By a proper ice selection of diameter for the lowermost portion of the hot-top there is obtainedthe correct position for accomplishing the above-mentioned regulation without any risk ofloose'nessbetween the casing and the ingot mold or the formation of-projections, pads or the like in the ingot between the mold and the hot top, and thus by the use of thehot' top structure according to the present invention, only negligible surface errors appear upon the topbloomor. slab during rolling. Consequently a great part offthelmaterial in the sinkhead of the ingot is utilized.

One of the primarypurposes of hot tops in the manufacture of highiquality steel is to orient the pipes and liquationsin the upper portion of the sinkhead; Suitable angular limitsfor the inclined mold surfaces are between 2-15., and preferably between 4-8= to achieve uniform ingots within'the limits of the volume variations 7 which usually occur.

gent'wall section and also a second wall section adjacent to and above the first divergent wallv section, the secend wall section having a greater angle of divergency' relative to the longitudinal axis of the mold. In this case the hot top casing is formed with such a diameter at its lower extremitythat this diameter will be between the greatestand the smallest diameters for the abovementioned second section in the same plane through the longitudinal axis of the hot top. Thus the sinking of the hottop casing may be regulated in an accurate mantier, and reduction of the mold volume will not occur asa result of the need of greater inclination for the inner walls; of the ingot mold along a greater portion of. the. mold length. The material in the hot top casing may be chosen in such a manner that the lower extremity of the casing will form a contiguous engagement with the inner wall. of the casing to achieve a effect.

In another embodiment of the invention, a filler is introduced inside the casing at the point of contact with the moldwalls, said filler consisting of asbestos, straw,

FIG. 1 is avertical section of the hot top casing taken along line 1 1 of FIG; 2;

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

FIG. 3 is a vertical sectional view taken through the mold with the hot top casing mounted therein;

FIG. 4 is a detailed section of the joint between the casing and the mold wall of FIG. 6;

FIG. 5 is a detailed sectional view of the lower extremity of another casing embodiment; and

FIG. 6 is a detailed sectional view of another embodimentof hot top casing mounted on an ingot mold.

Referring first more particularly to FIG. 3, the hot top 12 is positionedin the upwardly divergent upper portion ofthe ingot mold 11, which upper portion has in transverse cross section having the configuration of a square with roundedcorners, although other forms and configurations are equally applicable. In the illustrated example a greater part of the inner walls 13 are divergently inclined, and at a certain height above the bottom 14 of the ingot mold there is formed a circumferential shoulder or second divergent portion 15 having a greater angle amazes good sealing volume variations of the ingot mold and the varying sinkage of the hot top as a result of the diameter variations of the ingot mold (i.e., the variation in the diameter). It is possible to form a greater part or all of the inner wall of the mold at a certain inclination angle a, but this is suitable only for certain specific cases, as for example, for small inclination angles (slightly more than 2), and when this inclination angle for the Wall surface 13 corresponds with the correct angle or. Above the shoulder portion 15 there may be provided a mold section with a smaller or zero angle of divergency so that a space will surround the hot top which may contain an enclosed volume of air or a desired insulating filler material as will be described below. In certain cases it may be desirable to terminate the ingot mold at the upper extremity of the shoulder portion 15 and to place a separate outer casing arourd the hot top, as will be described below with reference to FIG. 6. The angle of inclination of the surface 15 should be between 2 and 15, and preferably be between 4S.

The hot top casing 17 comprises a fibrous material and may have various forms. The casing 17 may either be upwardly convergent or of uniform cross section along its length as shown in FIG. 5. At its lower extremity the casing 17 has an outer surface 13 converging to its inner surface; this surface 18 may extend over a part or all of the length of the casing 17. As shown in FIG. 4, a possible variation in height 12 along the wall 15 for the lowermost extremity of the casing lies between the elevation levels 22. and L3, and in the illustrated example this lowermost extremity is positioned adjacent half the variation scope (ll/2). The surface 18 is so formed that it fits against the surface 15 of the ingot mold both with regard to surface form and diameter. As mentioned above, the diameter may be so determined that the casing surface 13 will be positioned for engagement with the shoulder surface 15. Either before or after the insertion of the casing the sealing materialsuch as asbestos, straw, putty, wood wool, glass wool or the like-may be inserted around the outer surface of the casing. This, however, is an alternative which may be excluded or varied. If desired, one or more thickened portions may be formed in the outer wall of the casing 17 above the lower terminal portion 18 or the casing may be formed with a substantially constant wall thickness along the entire length of the casing above the terminal portion i8. This casing 17 may also contact the sinkhead of the ingot and as a result of the terminal surface 18, the casing will merge with the mold wall to achieve a smooth junction between ingot body and sinkhead. An appropriate casing thickness above the portion "it? might be -15 mm. for usual ingot sizes, and a suitable thickness for a 1.7 ton ingot has been established to be 12 The ingot mold may have configurations in transverse cross section which are round, square with rounded upper and lower corners, or polygonal with plane or rounded sides, the inner section of the ingot mold serving as a contact part. The divergent portion against which the terminal surface 18 of the casing rests is positioned below the upper end limiting surface 24 of the mold. By end limiting surface of the mold is meant a surface at the upper portion of the mold which forms an angle of at least 45 to the longitudinal axis of the mold.

, The casing 17 may be formed from suitable fireproof materials such as quartz, sand or other silicates, dolomite, cinders, fibrous materials such as paper pulp, waste paper, mechanical paper pulp possibly with an addition of chemical paper pulp, and a binder such as synthetic glues or resins, or glues of cellulose, animal or vegetable materials. Alternatively, the glue may consist of an inorganic composition such as fireproof cement or silicate of potassium. The percentage composition of the materials by weight may be selected as follows:

Paper pulp 2-20% (preferably 245%), binder (for example glue) 440%, and the remainder quartzite powder; also up to 10% fireproof fibrous material (such as asbestos) may be included.

The wall thickness of the casing and the height of the surface of the shoulder portion 15 is such that the terminal surface 18 of the casing 17 preferably extends over less than 60% of the height of said shoulder portion in order to obtain enough variation in scope in the sinking possibilities of the hot top. However, in some cases the terminal surface 18 may cover more than 60% of the surface 15.

in the embodiment of FIG. 3 the space 20 between the casing 17 and the upper portion 19 of the mold 11 may be filled with said, insulation bricks or any other heat insulating material in order to obtain good heat insulation at the hot top. Should air be used as a heat insulating medium the top of the space 2% will be enclosed.

If the mold terminates at its upper end in the shoulder portion 15 as shown in FIG. 6, an outer casing 21 may be placed concentrically about the mold opening and the hot top casing, said outer casing being formed of fireproof brick or the like. A suitable heat insulation filling may be placed between the outer casing 21 and the hot top casing 17. As possible alternatives, the outer casing 21 may extend along the upper portion of the casing 17 with the lower portion of the hot top casing extending into the upper portion of the ingot mold 11; also an outer casing for the hot top may be arranged outside the casing 17 but inside the upper portion of the ingot mold.

The selection of the angle of inclination a of the surface 18 and the mold shoulder surface 15 is of substantial importance. As an example, for a commonly used type of ingot mold a variation in volume of 4 liters and a variation in diameter of :2 mm. have been found to result in an angle (1 of 7.5.

The shoulder portion 15 may be so formed that it is possible to adjust a given ingot mold to produce an ingot of lighter weight. The shoulder part 15 in this case should have a sufficient length and downward extension to receive a casing with less diameter. The regulation to constant ingot weight for this smaller ingot may take place in the manner described above.

While in accordance with the provisions of 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 and modifications may be made in the apparatus described without deviating from my invention as set forth in the accompanying claim.

I claim:

An ingot casting mold comprising a mold body having a vertical cavity therein, the inner surfaces of the walls of the lower first portion of said cavity diverging progressively outwardly in the vertical direction at a constant first angle, the inner surfaces of the walls of a second portion of said cavity contiguous with and above the walls of said lower first portion of said cavity divergi progressively outwardly in the vertical direction at a constant second angle which is substantially greater than said first angle and is within the range from 4 to 15, a non-metallic hot top casing consisting essentially of a major amount of refractory material and a minor amount of an organic fibrous material and binder positioned in said mold cavity, said hot top casing being of the same cross sectional shape as the cross sectional shape of said mold cavity in a plane perpendicular to the longitudinal axis of the mold at the juncture of the mold and the casing, the walls of said casing terminating at their lower edge portions in downwardly convergent outer surfaces which are at substantially the same angle to the vertical as said constant second angle and are wholly in contact with said surfaces of the walls of said second portion of said mold cavity, the dimension in the vertical direction of said downwardly convergent surfaces of said casing being not more than about 60% of the dimension in the vertical direction of said surfaces of the Walls of said References Cited in the file of this patent UNITED STATES PATENTS Howard Jan. 13, 1925 Firth Aug. 18, 1931 Udy Sept. 2, 1947 Marburg Mar. 27, 1951 Farnsworth Nov. 24, 1959 FOREIGN PATENTS Great Britain July 10, 1924 Great Britain Jan. 26, 1933 Great Britain Nov. 5, 1952