US2585096A

US2585096A - Method of making an ingot

Info

Publication number: US2585096A
Application number: US729777A
Authority: US
Inventors: Florence L T Dornin
Original assignee: GEORGE A DORNIN JR
Current assignee: GEORGE A DORNIN JR
Priority date: 1947-02-20
Filing date: 1947-02-20
Publication date: 1952-02-12
Anticipated expiration: 1969-02-12

Description

Feb. 12, 1952 G, A, DORNlN 2,585,096

Feb- 12, 1952 G. A. DORNIN .2,585,096

` METHOD QF MAKING AN INGOT Filed Feb. 20, 1947 3 Sheets-Sheet 2 INVENTOR @am @MM MM Feb. 12, i952 G, A, DORN|N 2,585,096

METHOD OF MAKING AN INGOT Filed Feb. 2O, 1947 3 Sheets-Sheet 5 Si m Am aiented Feb. l2, 1952 UNITEDl Is'ra'rlss IPA'rBN'r OFFICE METTIOD FzlsAsglgG AN INGOT l Ohio, by Florence L. T. Dornin, executrix, Warren, Ohio, assignor to George A. Dornin, Jr.,

Warren, Ohio Application February zo, 1941, serial No. 729,777

3 Claims. l

- This invention relates to a method of making sound ingots of killed steel without employing a hotrtop. The elimination of the hot top results in the following advantages.

' (1) All hot top cost is eliminated (including handling cost and cost of breakingoi the hot top from the ingot after the ingot has been cast).

(2) There are fewer shut oils during pouring and consequently a shorter pouring time is required per heat. In casting ingots provided with hot tops it is customary practice to pour up to the bottom of the hot top, then to stop pouring to allow a seal to form betweenthe hot top and ingot mold and thereafter to resume pouring.

The shorter pouring time and fewer shut ois required where hot tops are not employed result in less stopper trouble.

(3) There is much less pouring dimculty when a running stopper does occur.

(4) 'I'he mold life is increased. The erosive action of the pouring stream on the bottom of the mold is less because the head (distance from ladle to bottom of mold) is shorter. Also when canted nozzles occur, there is more room in which to move the ladle around to correct for the canted nozzle, which means that the plug or plate in the bottom of the mold will be hit much oftener and there will be fewer "streamcut molds.

(5') There are fewer "stickers" for the reasons outlined in (4) above, and because due to the shorter pouring time per heat it is practical to slow pour the bottom of each ingot for thirty seconds or so, which cuts down pressure of impingement on the mold bottom, thus forming a cushioning pool to protect the mold from the severe erosive eii'ect of the full stream. Stickers have many disadvantages; they cause stripper delays, stripper breakdowns, poor mold liie, increased cost of heating and increased surface conditioning costs since sticker ingots are charged into the reheating furnaces in a colder condition than the usual ingots. Stickers do not follow their heats through the mill and quite often become mixed with ingots of different analyses.

In the accompanying drawings which illustrate certain embodiments of my invention,

Figure 1 is a vertical section through an ingot showing the pipe cavity and underlying segregate;

Figure 2 is a vertical section through an ingot in which cleavage has been produced articially between the core, which includes the metal to be isolated and the surrounding zone of sound meta Figure 3 is a vertical section through an ingot which has been treated as shown in Figure 2 and then upset to displace the surrounding zone away from the core;

Figure 4 is a view in side elevation of the ingot of Figure 3 after reshaping to prepare the ingot for rolling;

Figures 5 and 6 are vertical sections through ingot molds and ingots in which the ingots have too little taper;

Figures '7, 8 and 9 are vertical sections through ingot molds and an ingot, illustrating various stages of pouring, the taper of the ingot being excessive; and

Figure 10 is a vertical section through an ingot mold and ingot in'which the taper of the ingot is in accordance with my invention.v

The present invention constitutes an improvement over the invention disclosed and claimed in George A. Dornin Patent 2,021,227. Briefly, that patent discloses and claims a method of isolating unsound metal of an ingot in which the unsound metal is included in a. central core adjacent the top of the ingot and the unsound metal is surrounded by a zone of sound metal. The zone of sound metal is isolated from the central core of unsound metal for example, by wedging the surrounding zone of metal away from the central core, and upsetting the surrounding zone of sound metal axially of the ingot. The ingot is then forged or forged and rolled. The core of unsound metal may be severed either before or after the forging or rolling operation.

I have now found that the best results can be obtained in carrying out the process of the patent if the per cent taper in the ingot is within certain critical values, which lie in a relatively narrow range of percentages which are much greater than the taper generally employed. I'he amount of taper of an ingot which is to be used in the process of the Dornin patent is important from the metallurgical standpoint of producing ingots which are free from secondary pipe and segregation, from the standpoint of pouring practice, from the standpoint of isolating the core 'of unsound metal in the top of the ingot from the surrounding zone of. sound metal, from the standpoint of displacing the zone of sound metal axially of the ingot and from the standpoint of forging the ingot. The per cent taper as used herein is defined by the formula the top surface of the ingot, D2 represents the narrowest dimension of the bottom surface of the ingot body and L represents the body length of the ingot. 'Ihus the ingot shown in Figure 10. which has a horizontal width DI at the top of 2li/2", a horizontal width D2 at the bottom of the ingot body of 141/2", and a length L of 60", has a taper of about 11.7%.

Figures 1 through 4 are illustrative of the Dornin patent. An ingot of the type shown in Figure l having a pipe cavity 2, a central core 3 of unsound metal and a surrounding zone l of sound metal adjacent the top of the ingot is placed in a holding die 5 as shown in Figure 2. A wedge B such as a hollow punch is then driven into the top of the ingot to isolate the surrounding zone l of sound metal from the core l of unsound metal. Thereafter as shown in Figure 3, the zone I of sound metal which has been isolated from the unsound core is displaced axially of the ingot by an upsetting die 1, thereby forming an ingot of the shape shown in Figure 3 having the bulge 8. The upsetting operation may be accomplished in one step as shown or in two steps. substantially the shape shown in Figure 4 and thereafter is rolled, or forged to finished size. The central core 3 containing the unsound metal can be severed from the body of the ingot before the forging operation which produces the ingot shown in Figure 4 or it may be severed after the forging operation or after rolling.

'Ihe process of the Dornin patent and the process of the present invention relate only to the treatment of ingots which have been cast without the use of refractory hot tops. If an ingot were cast with a refractory hot top, the shrink head portion of the ingot within the hot top would be contaminated by the refractory The ingot is then forged to material of the hot top. Thus the bulged portion i 8 shown in Figure 3 would be contaminated on the surface with the refractory material and the corresponding part of the forged ingot as shown in Figure 4 would be contaminated. This contaminated portion covers substantially the area above the line 9 as shown in Figure 4, which amounts to approximately the upper fourth of the ingot. With the use of a hot top it would be necessary to crop oiI this contaminated upper portion, which` of course, would be very uneconomical.

Considering the per cent taper of the ingot from the metallurgical standpoint of producing ingots which are free from secondary pipe and segregation, if the taper is too small the metal tends to bridge during solidification after pouring, thereby forming an ingot having secondary pipe. If the taper is too great, the rate of rise of metal in the bottom of the mold is too rapid and the metal forms a thin skin which often tears during forging or rolling operations instead of forming the desired thick, tough skin. If the taper of the ingot is too great, it is sometimes necessary to cut down the pouring rate by means of a smaller nozzle so that the rate of rise at the bottom of the ingot will not be too great and this slows down the rate of rise of the metal at the top of the ingot to such an extent that bridging occurs which results in secondary pipe and segregation.

Ingots having too little taper are shown in Figures 5 and 6. Referring to Figure 5, the dotted lines I0 represent the progressive solidification of this ingot. For any given freezing line, the metal within this line is liquid While the metal outside is solid. Insulating mate,

rial M is applied to the top surface of the ingot immediately after pouring. The last metal to solidify (inside the freezing line la) contains the segregate zone and this zone is very deep as compared to the corresponding zone in the ingot shown in Figure 10. I have found that an ingot such as that of Figure 5, even 'under ideal conditions, produces a pipe cavity Il and a segregate zone I2 which is entirely too deep for reliable isolation under the process of the Dornin patent. Furthermore due to the small taper. the lines of freezing have very little upward and outward slant-i. e., they are very nearly parallel, even under ideal conditions. There is considerable likelihood that under less ideal conditions the progressive solidiflcation will be as shown in Figure 6. The lines of freezing are so nearly parallel that any small deviation from ideal practice (such as a slight delayin applying the top insulation) will distort these lines inwardly enough to cause bridging as shown by reference numeral i3 while the metal within the line Il is still liquid. The subsequent 'solidiflcation and corresponding shrinkage of this metal will resultI ii secondary pipe and segregation designated by reference numeral I5.

Figures 7, 8 and 9 represent the solidiilcation of an ingot such as may occur under certain conditions in which taper is excessive. Because of the excessive taper the cross-sectional area in the lower end of the ingot is very much less than that of the ingot in Figure 10, while the area in the upper part is very much greater. Therefore in order to prevent an excessively rapid rate of metal rise in the lower part of the ingot during pouring it is necessary to use a much smaller nozzle which automatically results in a very slow rate of rise in the upper portion of the ingot. This often results in the formation of a crust which grows inwardly from the sides of the ingot during the latter stages of pouring. The formation of this crust I8 is shown in Figure "I, which represents the condition of the ingot about $6 poured, the metal inside line lia being liquid. In Figure 8, which represents the condition at the instant pouring is finished, the crust is designated by reference numeral Il. Figure 9 shows the completely solidified ingot. The distortion of the freezing lines caused by the crusting results in complete bridging of the ingot as indicated by reference numeral i8. At this time the metal within the freezing line I9 is still molten and its subsequent solidiflcation results in secondary pipe and segregation designated by reference numeral 20.

If the taper of the ingot is within the proper limits, the freezing takes place in a manner similar to that shown in Figure l0. 'I'his figure illustrates an ingot having a taper of approximately 11.7%. In this figure, the solidication as represented by the freezing lines is such that the pipe cavity 2i and segregation zone 22 are relatively shallow and the segregation zone may be therefore readily isolated from the surrounding zone 23 by the method of the Dornin patent. Furthermore, secondary pipe and secondary segregation have been entirely eliminated. It will be seen that the lines of freezing have a very marked upward and outward slant. This insures progressive soiidiilcation of lthe ingot from the bottom upwardly in spite of any reasonable deviation from ideal pouring conditions which may occur in practice.

Considered from the standpoint of pressing the ingot according to the Dornin patent, the vingot must have enough taper to insure a reasonably shallow pipe cavity 2l and segregate zone 22. as shown for example, in Figure 10. For a given weight and height of ingot, the depth of the pipe cavity and the segregate zone under it decrease as the amount of taper lincreases. Too much taper, however, increases the top area of the ingot and the power required to upset it (Figure 3) is proportional to this area. An increase in the top area of the ingot increases both the work of upsetting the zone of sound metal axially of the ingot and of forging the upset metal back to a size suitable for rolling.

There is a fairly narrow range of tapers which gives the best combination of pipe cavity depth,

depth of segregate zone and top area of ingot for minimum pressing cost and this range corresponds very closely to the best range for obtaining interior soundness and exterior surface of the ingot.

For a given top dimension and a given per cent taper, the bottom dimension wil-l decrease :as length of ingot is increased. The difference between the top and bottom areas and the corresponding rates of metal rise will increase with increased lengths. It isadvisable, therefore, to use a lower per cent taper on long ingots than on short ones if the danger of bridging shown in Figure 9 is to be avoided. Per cent taper lis thus related to the slenderness ratio of the ingot which is here defined as the ratio of body length tothe minimum top dimension (L/DI in Figure 10). I have found, for example, that the maximum taper which can safely be used on relatively short ingots (slenderness ratio of 2.5 to 1 orless) may be several per cent greater than that used on relatively long ingots (slenderness ratio 3.0 to 1 or greater).

For a given slenderness ratio the ideal taper will vary somewhat from plant to plant, depending among other factors upon the type of steel, pouring temperature and pouring rate. The total shrinkage volume of an ingot is dependent on the volume remaining fluid when pouring is completed, and on ,the degree of superheat of this liquid steel. The volume of the shrinkage cavity will, therefore, vary considerably under varying conditions. I have found the total shrinkage volume to vary from about "3% to about 4% of the total ingot volume. Since the depth of pipe cavity will vary in about the same proportion, the ideal per cent taper will also vary. For example, high carbon steels generally have larger shrinkage volumes than low carbon steels because they are generally poured faster and with a higher degree of superheat. 'I'he depth of the pipe cavity is therefore greater and it is preferable to use a larger per cent taper when a mold is to be used primarily on high carbon steels. This is practical since they have relatively tough skins and therefore have less tendency to tear on rolling or forging.

Low carbon steels, and particularly low carbon alloy steels, generally have rather tender skins and are therefore poured relatively slowly, resulting in smaller shrinkage volumes and shallower pipe cavities. The ideal taper for such steels is, therefore, somewhat less than for high carbon steels.

While the ideal slenderness ratio and per cent taper will vary somewhat due to the 'above mentioned conditions, the slenderness ratio and the per cent taper as hereinI defined should be within the following limits according to my invention. The slenderness ratio the upper portion of the ingotis being operated on to isolate the unsound metal and to displace the sound metal axially of the ingot. If the slenderness ratio is below 1.75, the ingot is so short that there is not a sufllcient portion extending above the holding die to enable the operations of isolating the segregated zone and displacing the sound metal axially of the ingot to be carried out in an eflicient manner, it being understood that a certain vertical height of the ingot must be supported by the side walls of the holding die to maintain the ingot in vertical equilibrium. Furthermore, when the slenderness ratio is less than 1.75, the ingot is so short that it becomes uneconomical to process it according to the Dornin patent since the amount of work required in displacing the sound metal axially of the ingot as shown in Figure 3 and the forging and rolling of the ingot to suitable size requires excessive power.

For a given top dimension and a 'given per cent taper, the bottom dimension will decrease as the length of the ingot is increased, i. e., as the slenderness ratio is increased. The difference between the top and bottom areas and the corresponding rates of metal rise will increase as the slenderness ratio increases. If the slender- Aness ratio exceeds 3.75 the rate of rise of the metal in the bottom of the mold will be too great unless the rate of pouring is cut down. If the rate of pouring is cut down, the ingot may bridge over at the top as shown in Figure 9. For these and other reasons, the slenderness ratio should be not less than 1.75 and not more than 3.75.

For a slenderness ratio from 1.75 up to less than 2.50, I may use a per cent taper between 7 and 17%, the per cent taper generally being between 8 and 16% and preferably between 9 and 15%. For a slenderness ratio from 2.5 up to less than 3.0%, I may use a per cent taper between 7 and 16%, generally between 8 and 15% and preferably between 9 and 14%. For a slenderness ratio from 3.0 to 3.75, I may use a per cent taper between 7 and 15%, generally between 8 and 14% and preferably between 9 and 13%. It will be seen that in accordance with my invention the slenderness ratio is never less than 1.75 and never exceeds 3.75. The per cent taper never is less than 7% and never exceeds 17%.

If the slenderness ratio is from 1.75 to less than 2.50. the maximum per cent taper is 17%. If the slenderness ratio is from 2.5 to less than 3.0, the maximum per cent taper is 16% and if the slenderness ratio is from 3.0 to 3.75, the maximum per cent taper is 15%.

By employing the slenderness ratio and per cent taper within the critical ranges specied, it may be possible to produce a segregate zone of unsound metal which is sulciently shallow so that it will be unnecessary to employ the wedging step shown in Figure 2. Thus I might proceed directly to the upsetting step shown in Figure 3 without employing the wedging step.

The invention is not limited to the preferred 7 embodiment but may be otherwise embodied or practiced within the scope of the following claims.

What is claimed is:

l. The method of forming an ingot which comprises casting the entire side surface of a big end up ingot of fully deoxidized steeLagainst a chill mold. said ingot having a slenderness ratio from 1.75 to 3.75 and a taper of 7 to 15%, thereby forming an ingot having at its top a central core including unsound metal surrounded by a zone of sound metal and displacing said zone of sound metal axially of the ingot to isolate the core in` cluding the unsound metal.

2. The method of forming an ingot which comprises casting the entire side surface of a big end up ingot of fully deoxidized steel against a chill mold. said ingot having a slenderness ratio from 1.75 to 3.75 and a taper -of 8 to 14%, thereby forming an ingot having at its top a central core including unsound metal surrounded by a zone of sound metal, wedging the surrounding zone of sound metal away from the central core including the unsound metal, and displacing said zone of sound metal axially of the ingot to isolate the core including the unsound metal.

3. The method of forming an ingot which comprises casting the entire side surface of a big end up ingot a fully deoxidized steel against a chill mold. said ingot having a slenderness ratio from 1.75 to 3.75 and a taper of 9 to 15%, thereby forming an ingot having at its top a central core including unsound metal surrounded by a Chicago. Ill.. pP. 650-653.

8 zone of sound metal, wedging the surrounding zone of sound metal away from the central core including the unsound metal and displacing said zone of sound metal axially of the ingot to isolate the core including the unsound metal.

FLORENCE L. T. DORNIN. Ezecutrix of the Estate of George A. Dornin. De-

ceased.

l REFERENCES CITED The following references are of record in the le Ofth1s 'patenti UNITED STATES PATENTS` OTHER REFERENCES The Ingot Phase of Steel Production. 2nd. ed. (Emil Gathmann, pub. 1937 Schneiderith and Sons, Balt., Md., pp. 36-38. (Div. 14.)

(Div. 14.)

Claims

1. THE METHOD OF FORMING AN INGOT WHICH COMPRISES CASTING THE ENTIRE SIDE SURFACE OF A BIG END UP INGOT OF FULLY DEOXIDIZED STEEL AGAINST A CHILL MOLD, SAID INGOT HAVING A SLENDERNESS RATIO FROM 1.75 TO 3.75 AND A TAPER OF 7 TO 15%, THEREBY FORMING AN INGOT HAVING AT ITS TOP A CENTRAL CORE INCLUDING UNSOUND METAL SURROUNDED BY A ZONE OF SOUND METAL AND DISPLACING SAID ZONE OF SOUND METAL AXIALLY OF THE INGOT TO ISOLATE THE CORE INCLUDING THE UNSOUND METAL.