US2402833A - Method of casting ingots - Google Patents

Description

ED STATES 2,402,833 I I 'Ms'rnon or CASTING moors Paul F. Mumma, McKeespor-t, ad Arthur W.

Thornton, Pittsburgh, Pa., e

1- ore to National Tube Company, a corporation of New- Jersey Application November 16, 1943, Serial No. 510,582 (cl. 22-216) 7 Claims. 1

' The present invention relates to an improved 1 method of casting ingots, a primary object of the invention being to make possible the production of steel ingots in which the metallurgical pipe cavity is unoxidized and is free from slag or other contaminatmgnon-metallic or metalloid materials.

A further object of the invention is to reduce the depth of the metallurgical pipe cavity insofar as this may be practical without resorting to the use of elaborate and expensive hot topping practices and without incurring the economic losseslncldent to the high ingot top discards required on conventional hot-topped ingots. I I

The above and related objectives of the inven-.

tion will be more fully apparent from consideration of the following specification and claims when read in connection with the accompanying drawing, in which:

Figure 1 is a plan view ofv the apparatus for carrying out one of the essential steps of the improved method.

Figure 2 is a sectional view on line 11-11 of metallurgical pipe is uniformly non-porous. and

thus an important advantage arises by the exclusion from the pipe of oxidized portions and the exclusion from the pipe of slag or oxides such as inherently collect within the pipe according to conventional practice.

It is well known to those skilled making. shaping, and tratins steel products, that the piped ends of ingots are cropped on, thus 'produclng a large amount or heavy scrap. However,

- in the rolling of certain steel products such as Figure 1, illustrating the manner oi gently apply-. I

ing a coolant to the top crust formed on an ingot immediately after-teeming. I

Figure 3 is an elevation of the apparatus shown in Figure 1, viewed in the direction of the arrow 3 thereof. I

Figure 4 is a section similar to Figure 2, illustrating a further essential step 01' app ying an insulating material to the solidified top crust oi the ingot. I

In the conventional practice usually followed for the production oi. steel ingots of ordinary seamless steel tubing produced by the rotary 2s piercing process, it is found that within reasonable limits a clean, unoxidized and slag-free pipe portion 01 an ingot is not detrimental to the quality of the finished product, and hence ii this condition can be maintained, which is made p05 slble under the herein claimed invention, a higher commercial grade (as distinguished from special quality steels receiving expensive and at, times elaborate "hot topping treatment), the ingot molds are filled with liquid steel to the desired height, and this molten metal solidifies into an ingot with no further special treatment, in accordance with the natural laws governing the solidification phenomenon. As is well known to those skilled in the art. when this conventional pouring practice is used on semi killed or killed steels. the resulting ingot contains a deep, roughly cone-shaped cavity, generally referred to as a metallurgical pipe, in its top portion. This pip results from a volumetric contraction obtained in the transition of the metal from the molten to the solid state. The top or the pipe is covered over by a crust of initially solidified metal which, under optimum conditions, should be continuous and tree from openings leading to the metallurgical pipe. In actual practice, however, many 53' ingot-to-flnished product yield is achieved.

Referring to the drawin in carrying out our novel method, molten steel contained in an overhead conventional portable ladle I0 is teemed into a conventional ingot mold I2. Immediately after the teeming, we gently apply a coolant so as to insure that a non-porous top crust i4 is formed on the ingot It. The coolant generally employed is water, and we deem it important to initia y apply the-water so as to gently flow it over the top of the molten metal quickly after teeming. As suggested in- Figures 1 and 2. a coolant such as water may be applied by discharging a plurality of jets 20 from a pipe 22- obliquely downward, so that the Jets first impinge on the inner face 24 o! the mold opposite the pipe 22. This water then gradually and gently floats over the top of the molten steel to th crust it.

The volume oi water'supplied is under control 01' a valve 28 located in pipe to leading to a suita. i I

in the art of metallurgicalpipe it. The quantity of water Y remainder Of rials such as used varies somewhat with the ingot size. For

example, we have found that approximately gallons should be used on a 10,000-pound ingot having a top area of 575 square inches. It is,

rupture the initial, extremely tender solidified film which eventually becomes the thicker crust II. We have found that this gentle initial water application can be effectively made by the relatively'simple and inexpensive apparatus such as shown in Figures 1, 2, and 3 of the drawin which is nothing more than a drilled pipe with a control valve therein, the nozzles or orifices in the pipe being disposed at the proper angle to impinge the water jet first on the side wall of the mold, as indicated in'Figure 2, so that thereafter the water body is slowly and gently flowed over the molten steel. gentle application, for example, after the first 10 per cent of the total water'used is applied, the

the total water may be added in any manner found most convenient.- Other meansj'of spraying could, of course, be used during the initial. application, and if desired the entlre',quantity of water could be placed on the top by discharging the water through a perforated pipe such as shown at 22. The net result, of the gentle application of water or other coolant to the top ofthe molten metal which eventually formsthe ingot. it will be appreciated, is to form an impervious crust i4 spanning the pipe or cavity II so as to prevent or minimize oxidation of the of the pipe and to exclude oxidised slag orother contaminating nonmetallic materials such as normally collect within the-pipe under prior practices where no special provision is made for their exclusion.

After the impervious crust II is formed by the gentle application of the coolant, an insulating such as indicated at it in Figure 4 is applied to the top crust N. This insulating materialis 'eflectlve to restrict heat dissipation from the exposed ingot top surface. and thus assist in- "maintaining a portion of the ingot top volume (beneath the solidified crust l4) in a molten state for 'a-longer-than-normal period of time, so that this molten metal, by gravitating toward thebody oftheingot, will partially compensate for the volumetric shrinkage taking place in the ingot andhence reduce the depth of the metallurgical pipe; -,The insulating material 32 may be one or moiepf a variety of inert or' combustible matesaud, pulverized brick, dehydrated lime. limestone or dolomite dust. coke dust. fine coal, straw, grain hulls, cork, etc., its principal requirement being that either by blanketing effect or by exothermicaction, or both, it acts to restrict heat flow from the top surface of the ingot. No question of ingot metal contamination is involved since the prior water-sealing operation prevents access of the insulating material, or its reaction products, to the molten metal beneath the water-sealed ingot top crust.

Heretoiore, when using conventional hottoppins practices. the cropped-oi! or discarded tops of the ingots are normally of the order of from 12 to 20 per cent of the weight of the ingot.

An important advantage of the herein claimed invention is that amuch smaller portion of the ingot need be discarded, this being due to the fact that there is no mechanical discontinuity Following the initial in the outside ingot surface. such as occurs at the specific steps which a reduction to practice has shown to be highly advantageous, and have illustrated apparatus found to be practical and well suited for carrying out the herein claimed method, it is to be understood that the detailed disclosure and drawing are to be interpreted in an illustrative rather than a limiting sense, since various modifications may be resorted to by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

We claim: f

i. In the casting of ingots, the method which comprises teeming molten metal into an ingot mold, applying a coolant to the top surface of the ingot immediately after said teeming step so as to effectively. seal the initial top crust of the ingot, and covering the solidified top crust with an insulating material to restrict heat dissipation from the exposed ingot top surface and thus assist in maintaining a portion of the ingot top beneath the solidified crust in a molten state for a longer-than-normal period of time, so that this molten metal, by gravitating toward the body of the ingot,v will partially compensate for the volumetric shrinkage taking place there and hence reduce the depth of the metallurgical pipe.

2. Inthe casting of ingots, the method which comprises teeming molten metal into an ingot mold, gently applying a coolant to the top surface of the ingot immediately after said teeming step so as to eflectively seal the initial top crust of the ingot, and covering thesolidifled top crust with an insulating material to restrict heat dissipation from the exposed ingot top surface to thus assist inmaintaining a portion of the ingot top volume in a molten state for a suillcient period of time to allow the molten metal to gravitate toward the body of the ingot so as to partially compensate for volumetric shrinkage taking place there and hence reduce the depth of the metallurthe mold cavity so as to gently apply the water to the top surface of the ingot immediately after said teeming step so as to form an impervious initial top crust on the ingot, and covering the top crust with an insulating material to restrict heat dissipation from the exposed ingot top surface and thus assist in maintaining a portion of the ingot top volume beneath the solidified crust in a molten state for a longer-than-normal period of time, so that this molten metal, by gravitating toward the body of the ingot, will partially compensatefor the volumetric shrinkage t king place there and hence reduce the depth of the metallurgical pipe. I

4. In the casting of ingots, the method which comprises teeming molten metal from an overhead source into an ingot mold, impinging a coolant against an inner wall of the ingot mold so as to gently apply said coolant to the top surface of the teemed metal immediately after said teeming step so as to form an impervious top crust on the ingot, and covering the thus-formed 'top crust with comminuted insulating material I 5 to retard the dissipation of heat from the top surface of the ingot.

5. In the casting of ingots, the method which comprises teeming molten metal from an overhead source into an ingot mold, directing water at a low angle against the inner wall of the ingot mold, so as to gently apply said water to the top surface of the ingot immediately after said teeming step so as to form an initial impervious top crust on the ingot, and covering the said top crust with an insulating material to re- .tard the dissipation of heat from the top surface 1 of the ingot, thereby reducing the depth of the metallurgical pipe.

6. In the casting of ingots, the method which comprises teeming molten metal from an overhead source into an ingot mold, gently applying a coolant through a multiplicity of jets to the top surface of the teemed metal quickly after 6. I said teeming step so as to form an impervious top crust on the ingot, and covering the thus-formed top crust with an insulating material to retard the dissipation of heat from the top surface of the ingot.

7. In the casting of ingots, the method which comprises teeming molten metal from an over-- head source into an ingot mold, gently applying a determined amount of coolant thereto so as to quickly form an impervious top crust'thereon to obtain a pipe free of oxidation and slag and covering the said top-crust with an insulating material to retard the dissipation of heat therefrom, thereby reducing the extent of the pipe so that a large percentage of the ingot can be rolled into seamless tubing and the like.

PAUL F. MUMMA. ARTHUR w. THORNTON.

Images