US2837800A

US2837800A - Casting of ferrous ingots

Info

Publication number: US2837800A
Application number: US541958A
Authority: US
Inventors: Hachiya Shigeo; Uchiyama Tatsuhei; Aihara Masumi
Original assignee: Yawata Iron and Steel Co Ltd
Current assignee: Yawata Iron and Steel Co Ltd
Priority date: 1954-11-01
Filing date: 1955-10-21
Publication date: 1958-06-10
Anticipated expiration: 1975-06-10

Description

, June 10, 1958 sHIeEo I-IAcI-IIYA ETAL 2,837,800

msmc OF FERROUS INGo'rs 2 sheets shee 1 Filed 001;. 21, 1955 FIG. 4

I FIG. 2}

FIG.

FIG. 5

FIG. 3

1NVENTQR5 SHIGEO HACHIYA TATSUHEI UCHIYAMA MASUMI AIHARA ATTORNEYS June 1953 SHIGEO HACHIYA ETAL 2,837,800

CASTING OF FERROUS INGOTS Filed Oct.- 21, 1955 2 Sheets-Shee 2 INVENTORS SHIGEO' HACHIYA TATSUHEI UCHIYAMA MASUMI AIHARA BYM,WM

ATTORNEYS the subsequent rolling process.

United States arent O 2,837,800 CASTING OF FERROUS INGOT S Shigeo Hachiya, Tokyo-t0, and Tatsuhei Uchiyama and Masumi Aihara, Yawata City, Japan, assignors t Yawata Iron and Steel Co., Ltd., Tokyo, Japan, a Japanese corporation Application October 21, 1955, Serial No. 541,958 Claims priority, application Japan November 1, 1954 12 Claims. (Cl. 22215) The present invention relates to a method of casting ingots intended to be rolled into sheet, plate or structural metal form. More particularly, it has especial relation to such a method wherein occluded gases are eliminated, whereby physically sound ingots, free from skin blow- "holes and inner segregations, are obtained.

molten steel may be melted and refined, deleterious gases and non-metallic inclusions, which bring about ingot defects, can be found in any kind of an ingot. Of the gases, oxygen, nitrogen, and hydrogen, etc., will form detrimental skin blowholes near the entire periphery of '21 killed steel ingot on solidification after being teemed into a mold. The skin blowholes result in stringers and cracks in rolled metal products. The stringers and cracks must be removed by planing or scarfing either the ingot -'or the rolled metal.

With respect to rimmed steel ingot, the occluded gases remain in the ingots themselves, and are subject to Most of the gases result inthe inner gas holes peculiar to rimmed steel in general, a part of them will form undesirable tubular gas pockets in the lower central peripheral portion of the ingot, and some of them will form unfavorable inner segregations together with a gas hole group in the upper central portion of the ingot, which result in the formation of skin laminations in rolled products. In the rimmed steel ingot, the crust thereof consists of physically sound molten steel.

The skin blowholes in killed steel ingots, and the tubular gas pockets as Well as inner segregations together with the gas'hole group in rimmed steel ingots, are peculiar defects usually formed in these ingots, which have been generally believed exceedingly difficult to eliminate.

A great many methods and additives have been proposed and adopted in the past to eliminate such harmful blowholes and gas pockets, but it is believed that no one has ever endeavored to degasify the occluded gases at a desired portion of the molten steel teemed in the mold in such a simple and effective manner as set forth in the present invention. In accordance with this invention, a suitable degasifying agent is filled into the end of a treatingor stirring pipe, and this treating pipe is inserted into the rrnolten metal to be treated by anoperator, thus pushed below the surface thereof at any portion and at any effective treating level while being stirred or agitated by the operator in order to insure an effective reaction between the degasifying agent and the metal to be treated, eliminate the detrimental gases, and produce a sound steel ingot adapted for rolling and substantially free from skin blowholes and inner segregations.

it is the primary object of this invention to provide a method of casting a sound steel ingot substantially free from skin blowholes and inner segregations, heretofore considered impossible.

It is another object to provide a method of casting ingots in which the quantity of blowholes and gas pocket groups is considerably cut down.

It is another object to provide a method of casting killed steel ingots in which peripheral blowholes are eliminated to produce a more perfect killed steel ingot than heretofore possible and particularly intended for rolled products.

It is another object to provide a method of casting rimmed steel ingots in which tubular gas pockets in the periphery of the lower central portion thereof, and inner segregations together with gas hole groups in the upper center thereof, are removed to produce a sounder ingot for use in making rolled products, than has heretofore been possible.

It is still another object to provide an improved degasification treatment by the introduction of a treating or agitator pipe having a suitable degasifying agent filled thereinto into the molten metal, capable of discharging or exposing the degasifying agent at an effective treating level at any desired portion below the surface of the molten metal bath in the mold.

The foregoing and still further objects of the invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, are accomplished by the procedure of which a presently-preferred exemplary embodiment is described in the following.

Referring to the accompanying drawings:

Fig. 1 is a longitudinal section of a treating or stirring plpe.

Fig. 2 is a longitudinal section through a bottom-poured killed steel ingot casting apparatus.

Fig. 3 is a horizontal section taken along line 3-3 of Fig. 2.

Fig. 4 is a longitudinal section through a bottom-poured rimmed steel ingot casting apparatus.

Fig. 5 is a horizontal section taken along line 55 of the apparatus of Fig. 4.

Fig. 6 is a longitudinal section of a killed steel ingot produced by the conventional method.

Fig. 7 is a horizontal section of the ingot of Fig. 6, taken along line 7-7 of the latter.

Fig. 8 is a longitudinal section of a rimmed steel in- .got showing tubular gas pockets together with inner segre be treated. The other end of the agitator is handled by an operator.

Fig. 2 shows a bottom-poured killed steel ingot casting apparatus which comprises a big-end-up ingot mold 1, a shrink head casing 2, a runner 4, and a base-plate 5. 3 is the treating pipe or agitator. The aluminum 6 is dissolved and reacts with occluded gases in the molten metal 11 in the mold 1. h is the height of the teeming metal in the mold.

Fig. 3 shows, by means of arrows, the course along which the agitator 3 is moved; see also arrows in Fig. 2.

Fig. 4 shows a bottom-poured rimmed steel ingot casting apparatus which comprises big-end-down ingot mold 1a, .a runner 4, and a base-plate 5. 3 is the agitator. The aluminum 6 is dissolved and reacts with occluded ,gases in the molten steel 11 in the mold 1.

Fig. 5 shows, by means of arrows, the course along which the agitator is moved in the periphery and the center; see also arrows in Fig. 4.

Fig. 6 shows a diagrammatic longitudinal section illustrating the formation of skin blowholes of a killed steel ingot cast in the bottom-poured mold provided with a shrink head casing, and this steel ingot is obtained by the conventional method in a 60 ton basic open-hearth furnace. The ingot has the following chemical analysis: 0.34% C, 0.116% Si, 0.59% Mn, 0.02% P, 0.015% S, and 0.121% Cu. This ingot consists of semi-hard steel, and weighs 3 tons. Numeral 7 of Figs. 67 designates skin blowholes formed below the surface around the ingot.

Fig. 8 is a longitudinal section showing the formation of tubular gas holes 8 and inner segregations together with a gas hole group of a rimmed steel ingot cast in the bottom-poured mold, this steel being produced by the conventional method in a 6 ton Heroult basic electric furnace, and having the following chemical analysis: 0.08% C, 0.03% Si, 0.30% Mn, 0.006% P, and 0.020% S. This ingot is extra soft steel, and weighs 4.9 tons. Reference numeral 8 (Figs. 8 and 9) shows deleterious tubular gas holes formed around the periphery of the lower central portion of the rimmed ingot and reference numeral 9 shows inner gas holes peculiar to the rimmed steel ingot, while reference numeral 10 shows harmful inner segregations together with a gas hole group aggregated in the upper central portion of the rimmed steel ingot, which result in skin laminations in rolled products.

This invention is characterized by the method of casting ingots under degasification wherein an operator inserts an elongated pipe with a degasifier such as aluminum filled into the end thereof, into molten steel in the mold at its desired portion, ag-itates the molten steel, dissolves aluminum filled into the end of the agitator pipe in the molten metal, whereby the aluminum reacts with any occluded gases in order to remove the latter, regardless of the character thereof.

In the practice of the invention with reference to Fig. 2, when molten steel 11 is teemed into the bottom-poured big-end-up ingot mold 1 through runner 4, and at the beginning or at the latest at the time when the teeming of molten metal reaches one-half of the predetermined amount thereof, an agitator pipe 3 as shown in Fig. l is pushed to a shallow extent into the molten bath level. As illustrated in Figs. 6 and 7, peculiar skin blowholes 7 are formed in the inner periphery of a killed steel ingot, so that various gases contained in this peculiar portion of molten steel 11 can be removed by the effective degasification or deox-idization treatment according to the invention, that is, by the application of a stirring pipe 3 along the inner periphery of molten metal in the mold in such manner that the stirring pipe is moved while agitating along the inner periphery of the molten steel, as shown by the arrow in Fig. 3, coming into close contact with the mold, and then the agitator is lifted upwards as the molten steel rises in the mold while being stirred continuously. In the course of the agitation,

" 3 in the lower central peripheral portion thereof in order aluminum powder at the end of the pipe 3 is continuously dissolved in the molten metal and reacts with the occluded gases, such as oxygen, carbon monoxide, nitrogen, etc. in the metal, whereby the gases are eliminated continuously in the treated local portion of the metal. When almost all the molten steel has been teemed in the mold, agitation is discontinued, and the agitator is lifted above the metal bath level. With the above procedure, the occluded gases which result in skin blowholes can be removed. Furthermore, to give completeness to the process of de asification, agitation by means of this treat ing pipe 3 should be repeated several times in accordance with the steel quality, and necessity.

As for the agitator pipe 3 for this purpose, a carbon steel pipe is used. If it is made of heat resistant steel or of refractory material of the silico-carbide series, it is economical due to its durability. Instead of aluminum filled into the inside of the end of the agitator pipe 3, ferrosilicon, ferrotitanium, calcium silicide, or any other deoxidizer may be used either singly or in combination. The deoxidizers are used to advantage when filled into the end of a pipe, as powder or in finely divided form. Alternatively, a pipe of a low melting point material, or a pipe of thin wall which contains a nonpowdered deoxidizer in the inside of the end thereof can be used effectively, since the pipe is dissolved together with the deoxidizer to insure reaction between deoxidizer and molten metal.

In reference to Fig. 4, the application of this invention to the casting of rimmed steel ingots in the bottompoured ingot mold is as follows: when molten steel 11 has been teemed through runner 4, and filled to the predetermined height in the mold 1, an agitator pipe 3 is introduced immediately into the bottom portion of molten metal; first, molten steel 11 is agitated by the treating pipe to remove unfavorable tubular gas pockets 8 shown in Figs. 8-9; secondly, the treating pipe 3 is immediately moved to the upper central portion of the molten steel wherein inner segregations and gas pocket group 10 are formed, while being agitated. The arrows in Figs. 4 and 5 show how to agitate the molten steel effectively by the treating pipe, that is, the pipe is lifted gradually upwards while the steel is being agitated.

As agitation proceeds, powdered aluminum 6 is continuously dissolved in the molten steel to react with the occluded gases in the molten metal, whereby such gases are continuously removed from the treated portions of the ingot. To give completeness to the object of the invention, agitation by means of the treating pipe 3 can be preferably repeated several times in compliance with the steel quality and necessity.

In the case of a top-poured rimmed steel ingot, agitation is effected by the treating pipe as soon as molten steel has been teemed up in a similar manner as described in the bottom-poured rimmed steel ingot.

Thus, with respect to the rimmed steel ingot, the removal of its peculiar tubular gas holes as well as of its inner segregations together with the gas hole group which are the peculiar defects of the rimmed steel ingot, by means of the present degasifying treatment, results in a superior kind of steel ingot, one of the semikilled steel ingots.

As described in the foregoing, the process of this invention can be classified in regard to the manipulation of the treating pipe as follows:

(1) Killed steel ingot, bottom-poured casting. At the beginning of teeming molten steel, an agitator pipe is dipped to a shallow extent into the molten steel and raised as molten metal rises in the mold, while the molten metal is agitated in the inner peripheral portion thereof in the mold.

(2) Rimmed steel ingot, either bottom-poured or toppoured casting. An agitator pipe is immersed down to the bottom of the mold as soon as the teeming of molten EXAMPLE 1 Killed steel; bottom-poured cast ingot: 28 heats. Unit weight of various steel ingots: 3.3 tons-10.2 tons. Agitator applied: about 200 tons in all. Agitator not applied; about 300 tons in all. The quantity of aluminum filled into the end of an agitator: about 500 grams per ton. 1

The following table shows the comparison of formation of stringers and cracks in the steel products rolled from the above ingots, 200 tons and 300 tons, respectively.

Comparison of defects formation DESCRIPTION OF DEFECTS Treatment Stringer, Percent Crack, Percent Total, Percent kg. Ingot kg. Ingot kg. Ingot Agitator, applied. 216 0.1 860 0. 43 1, 078 0.5 Agitator, not applied 4, 686 1. 56 7, 211 2. 4 11, 897 3. 96

As described above, the process of the present invention is strikingly eiiective for the prevention of defects.

As shown above, with the ingots obtainedrin accordance with the treatment of this invention as astarting material, the quantity of inferior billets with such defects as inner segregations and gas hole groups were 2 of the 37 billets which were rolled into hoops as the final product, while, on the other hand, the quantity of inferior billets with defects were 8 of the 19 billets which were obtained from the ingots which had been produced with- -out the above treatment.

The foregoing indicates the preferred manner in which the invention can be carried out to attain the desired results. It 'is understood that various changes and modifications may be made in the method of the invention without departing from the spirit and scope of the invention or sacrificing its material advantages.

Having thus disclosed the invention what is claimed l. A method of casting iferrous ingots which comprises teeming molten ferrous metal into an ingot mold, introducing a treatingpipe having a degasifying agent filled into the foremost end thereof into the bottom portion of said molten ferrous met-a1 immediately upon completion of the teeming of said molten metal, agitating upwardly along the periphery of the lower central portion of said molten metal with said treating pipe in a circular motion to dissolve said degasifying agent in the molten metal, whereby various occluded gases in said molten metal are eliminated by reacting said gases with said degasifying agent.

2. A method of casting killed steel ingots which comprises teeming a predetermined amount of molten steel The kind of steel for the above test consists principally of free cutting steel. In regard to the type of steel, such as commercial extra mild steel and the like, in which the formation of longitudinal cracks is very frequent in rolled products due to the reduced state of deoxidation, the practice of this invention can be expected to be much more advantageous.

EXAMPLE 2.

Top-poured cast rimmed steel ingots were produced for billet (96 mm. x 96 mm.) for use in hoop, in which molten steel was applied by the agitation treatment of this invention by means of an agitator pipe to prevent formation of tubular gas holes as well as inner segregations together with gas hole group. The resulting steel ingots were rolled into billets, which were then rolled into hoops, the final products. The products were examined in comparison with those produced by the toppoured rimmed ingots of the same steel without the application of an agitator treatment of the invention.

(A) Chemical analysis:

Percent C 0.07 Si 0.01 Mn 0.39 P 0.012 S 0.026

'l'reat- Quantity Hoops Hoops Ingot N0. Aluminum ment of Billet rolled. rolled Consumed Time, produced (good (bad min. billet) billet) 2 kg. ingot-.. 1.5 18 18 1.6 kg. ingot 1. 5 19 17 not consumed. 19 11 into a bottom-poured ingot mold, introducing a treating pipe having a degasifying agent filled into the foremost end thereof into said molten metal at the latest at the time when the teeming of the molten metal reaches onehalf the predetermined amount thereof, agitating upwardly along the periphery of said moltensteel in a circular motion with said treating pipe as said molten steel rises in said mold, and discontinuing agitation and lifting said treating pipe up out of the molten steel upon completion of teeming of said molten steel, whereby various occluded gases in said molten steel are eliminated by reacting said gases with said degasifying agent.

3. A method as claimed in claim 2 in which the degasifying agent'is aluminum in solid form.

4. A method as claimed in claim 2 in which the degasifying agent is aluminum in powdered form.

5. A method as claimed in claim 2 in which the degasifying agent is selected from the group consisting of ferrosilicon, ferrotitanium, calcium-silicide and mixtures thereof.

6. A method as claimed in claim 2 in which the treating pipe is made of refractory material.

7. A method of casting rimmed steel ingots which comprises teeming molten rimmed steel into a bottompoured ingot mold, introducing a treating pipe having a degasifying agent filled into the foremost end thereof into the bottom portion of said molten steel immediately upon completion of the teeming of a predetermined amount of molten metal, agitating upwardly along the periphery of the lower central portion of said molten metal with said treating pipe in a circular motion, then moving said treating pipe to the upper central portion of said molten metal and agitating in said upper central portion of said molten metal, whereby various occluded gases in said molten metal are eliminated by reacting said gases with said degasifying agent.

8. A method as claimed in claim 7 in which the degasifying agent is aluminum in solid form.

9. A method as claimed in claim 7 in which the degasi fying agent is aluminum in powdered form.

10. A method as claimed in claim 7, in which a toppoured ingot mold is used.

11. A method as claimed in claim 10 in which the degasifying agent is aluminum in solid form.

7 r 12. A method as claimed in claim 10 in which the 1,673,873 degasifying agent is aluminum in powdered form. 1,814,584 2,591,517 References Cited 1n the file of this patent UNITED STATES PATENTS 5 1,053,738 McNilT Feb. 18, 1913 502,756 1,184,523 Field May'23, 1916 581,888 1,206,188 York Nov. 28, 1916 22,294 1,596,888 PacZ Aug. 24, 1926 of 1902 1,672,446 Cape June 5, 1928 10 --8 Hulsizer June 19, 1928 Bost July 14, 1931 Daussan Apr. 1, 1952 FOREIGN PATENTS Great Britain Mar. 24, 1939 Great Britain Oct. 29, 1946 Great Britain July 30, 1903