US2897555A - Steel ingot making composition, method and apparatus - Google Patents

Description

Aug. 4, 1959 sElJl NlsHlKloRl 2,897,555

STEEL IMGOT MAKING COMPOSITION, METHOD AND APPARATUS Filed Oct. 22, 1957 United States Patent O "ce STEEL INGOT MAKING COMPOSITION, METHOD AND APPARATUS Seiji Nishikiori, Hinaga, Chita-machi, Chita-gun, Aichi-ken, Japan Application October 22, 11957, Serial No. 691,750 Claims priority, application Japan December 22, 1956 6 Claims. (Cl. 22-64) This invention relates to a method and apparatus for making steelingots as well Ias to a metal oxide coating composition for use in casting. vMore particularly, it relates to a method of casting moltensteel `into ingots free from the contamination of foreign matter and gases with the aid of a mold coating composition.

In conventional practices a flow of the molten steel of a certain thickness is poured into Vthe mold from a ladle held immediately thereabove. Under these conditions, the molten steel falling from'a height upon the bottom of the mold envelopsv gases from the turbulent current of gases produced as the ow of liquid steel violently hits the surface of the pool of liquid metal in the mold. As a result, aws and blowholes inevitably occur inside the ingot due to inclusion of foreign matter and gases.

The principal object of the present invention is to pro vide a method and apparatus for producing uniform steel ingots with minimum possible aws and blowholes, the surfaces of which are so clean that no conditioning is required. It is also an object of the invention to insure above average yields. Further objects and advantages will be apparent from the following description.

According to the general methodof the Apresent in- Vention, steel together with a lighter metal oxide coating composition, both inliquid state, are introduced to a ladle, which is then rotated slowly together with an in- Y verted mold which is mounted thereon so as to permit mold and coats the same. The surplusfcoating cmposition in themold still in liquid state is replaced-bythe heavier liquid steel which follows the same into the mold fas the mold is rotated to an upright position. 'The'steel is then allowed to solidify into an in'go'thavin'gY clean surfaces and free from iiaws and blowholes.

2,897,555,y Patented Aug. 4, 1959 In the drawings:

Fig. l is a front view partly in section of the casting apparatus of the present invention;

Fig. 2 is the side view of the apparatus of Fig. 1;

Fig. 3 is a vertical section of the apparatus of Fig. l taken on the line 3-3 thereof;

Fig. 4 isa view similar to Fig. 3 but with the assembly rotated in the direction of the arrow;

Fig. 5 is a view similar to Fig. 4 with the assembly still further rotated; and n Fig. 6 is a view similar to Figs. 4 and 5 with the assembly fully rotated as at the end of casting.

As illustrated in the drawings in Figs. l, 2 and 3 inverted molds 10 are detachably mounted as at 9 ona ladle 11, the interior 12 of which is lined with tire and insulation brick, with the exterior being covered with steel plate 13. For pouring liquid steel and coating composition, ladle 11 is provided with an upwardly extending inlet or spout 14 servicing the upper portion 15 of the ladle. This latter portion is'provided with openings as at 16 (Fig. 3) Vfor burners 17 and 17 which maintain the said metal and coating substances in a molten condition when necessary. The assembled body including ladle, molds, inlet and burners is supported above a 'pit 18, adapted to accommodate the assembly when 'inverted, by trunnions y19 and 19 residing in rigidly mounted holders 20 and 20. The assembled body is krotated about 180 by means comprising motor 21, speedlimiting device 22, and reduction gears 23 and 24.

`The following constitutes a representative description of the present method andthe operation of the abovedescribed apparatus. After completion of the refining operation in the open hearth, converter, or'electric furnace, the molten'steel is poured into the ladlell through the inlet 14 either alone or together with vthe molten coating composition, described indetail hereinafter, which has been liquefied independently ofthe steel. It'is to be understood that the molten coating composition is present with the steel in the ladle prior t`o casting and may also be added to the ladle prior to the steel. The coating composition comprises between about l5 and 25%,

Afew minutes so that the latter .composition mayseparate from" the molten steel, owingto'its lowerspecic gravity, and rise to the' surface. The assembled body heterogeneity in vthe ingot products. l

methods on the contrary where teemingof the steel 4' including the ladle 11,molds 10 and supporting trunnions is rotated slowly in the direction indicated by the arrows in Figs. 3-5 by means of motor 21. During this slow rotation, the lighter molten coating composition 25 (Figs. 4 and 5) enters the mold and contacts the bottom and side walls thereof. Upon Contact with the cool mold it begins to solidify thus coating the interior surfaces thereof to a thickness of approximately 5 mm. As the assembly is rotated further, the molten steel 26 then moves into the ingot mold, replacing unsolidified liquid coating composition and forcing the same toward the upper open end of the mold. Since the open end of the mold adjoining the ladle is covered with the coating composition, the steel does not come in contact with the mold walls. As revolution proceeds, the molds are brought to the vertical position (Fig. 6) and are completely filled with molten steel. The liquid coating composition is displaced to zone 1S of the ladle, covering the upper part of the molds. Any excess liquid coating composition is discharged by gravity ow through inlet spout 14 and collected in pit 18. It is kept at a high temperature by radiant heat from the ladle v11 or by firing the burners 17, 17 when necessary. Meanwhile the heat of the molten steel is conveyed toward the exterior of the molds 10 very slowly by virtue ofthe inferior heat conductivity of the solid coating on the inside walls ofthe mold.

With ythe molds in upright position in 'pit'18, 'following solidiiication ofthe steel the molds lmay be detached from the 4ladle and conveyed from the scene land Vthe ingots removed therefrom in a conventional manner.

Conventional vingo/t casting methods usually give rise during solidilication of the molten steel to growth of columnar crystals approximately 40 -to 80 mm. in thickness adjacent the walls of 'the'mo'lds These crystals frow at right angles to the interior surface of the mold in the outer `part of the ingot which is subject to 'rapid cooling through contact with the mold. In accordance with the method of Vthe present invention, crystals of free orientation are formed in the ingothy lreason of slower cooling caused by 'the lcoating oflow heat conductivity which lines the interior of the-mold. Accordingly, steel ingots produced by'the present method are of uniform lstructure with theleast 'possible segregation. Furthermore, since the moltenv steel when poured into the mold only veryslowly replaces the liquid coating composition Valready in the mold, Mneither Igases nor the molten coating substance are enveloped by the steel. Thus, and through slow cooling, the present method permits the steel ingot to free itself of vblowholes and flaws prior to solidication. In addition, `the liquid coating composition displaced from the`mold by the -steel serves to keep the upper-part of the ingot at athigh temperature for a considerable time, which prevents piping in 'the ingot at this point,'since.solidication ofthe molten steel proceeds gently upward from the bottomfof the mold.

Only the upper 5% vof-ingots castinlaccordance with the present invention need 'be-discarded prior to rolling as compared with about %*lost as the result of conventional casting methods. The "surfaces of vthe ingots produced by the present method 'are so clean that no conditioning is required .prior to/rolling. YFrom these standpoints the invention provides 'an ingot Ycasting method which is more e'fhcient `from a yield standpoint. Y

In accordance with this invention,` one or a plurality of molds may 'be employed and severaljingots cast simultaneously from the same 'heat' `which eliminates In conventional ismadeinto individual molds in succe's'siom even though the same heat Aof steel be used, dissimilarity/inV the qualities of the individual ing'ots canntbe favoidedbecause Vof ditferencesrin the teeming velocities and'temperatures.

Vto

Further in accordance with the present apparatus and method, losses are reduced since all ingots cast simultaneously are of substantially uniform size and weight. In the conventional method the last mold is usually not filled either to the Ifull scale or to the same height to which the other molds were filled with the same heat of molten metal.

Thus, the present invention constitutes an improvement in almost every phase of conventional ingot casting methods. A substantially flawless ingot is produced which has no vblowholes or non-metallic inclusions and the yield is at least 10% better than that possible heretofore.

Referring now to the coating composition in detail, this material must have a specihc gravity sufficiently low that it will not be rolled into the molten steel. It must consist of substances that do not affect the composition of the steel, that is, it must be chemically inert at the temperatures of molten steel. It must have a low melting point and a high fluidity. It must neither crystallize during solidication in contact with molten steel nor gasify at these temperatures. The composition must also be capable of absorbing oxygen and other gases contained in the molten steel as well as non-metallic inclusions.

In accordance with the present invention, the coating composition comprises a mixture of metal oxides, with the principal components being silica, alumina and calcium oxide. The remainder of the composition includes small amounts of other metal oxides, while the aforementioned principal ingredients account for about -85% and preferably about 80% by weight of the mixture. The principal components comprise:

Percent Siog l 5 0-8 0 A1203 10-30 CaO 15-35 A typical coating composition having a melting point of about 11,00% =C..analys`es in percentages by weight:

SiO; FeO A lgviO GaO Mg() MDO T102 F6303 Nag() B10 45,0 3.5 ra 20.7 0.20- 10.-0 las Tracel 2. 1 .4.18

hve heats of KKZ-and live heats of XEIM in the production of 200 kg. steel ingots -by the method of the present invention.

Table I Teemlng Temperature v Kind of in C. Heat Number Steel Coating Steel KTH 1, 400 1, 660 KK2 1, 510 1, 600 A Km ,58o 1, 580 am 1,580 p i; 610 xm 1, 540 1,620 XEL 1,450 1, 600 Km0/r 1, 520 V 1, 600 XEIM-- 1, 450 1, 670 xFrM 1, 550 1, 690 XEIM l, 560 l, 600

' Table 11 j Y N on-Metallic Inclusions 3-Stage Flaw Macro-Corrosion 5 Y Detection2 l Heat Diameter e A A-Type BType Grain Numof Roll Tested Size ber mmm. Placel i Y Aver- Maxi- -Aver- Maxi- Nblielil. lst 2nd 3rd T L S Sc Se D B Bs E Cleanage mum Cleanago mum ness Thick- Thickness Thick- Thickness ness Y ness ness 1 70 {T (Lg) {1)}0 1 1 1 l1 1 2 1Y 1 .1 0.18 .3.1 g 55} 2.09 f3.2 6 G46 B {9g} 0 0 1 1 1 1 1 2 1 1 1 0.27 4.1 8g 2.56 3.7 5 G4.8 T 0 o 0 1 2 1 1 1 2 1 1 1 I0.53 4.2 5g 2.97 4.0 6 G50 2 95 M 0 0 0 1 1 1 2 1 2 1V 1 1 0.46 4.6 8g 2 92 45 7 G5.2 B 0 0 0 1 1 1 2 v1 2 1 1 1 0.31 4.5 5g 3.34 4.4 0 3G53 T 0 0 0 1 1 1 2 1 2 1 1 1 0.94 5.6 9g 2.93 4.5 7 G5.0. 3---..-.- 95 M 0 0 0 1 1 1 2 1 2 1 1 1 0.32 4.3 i 5g i 2.89 4.7 6 G46 B 0 0 0 1 1 1 1 2 1 1 1 0.26 3.4 4(4) 2.97 44 6 G4.5 T 0 0 0 1 2 1 2 1 2 1 1 1 1.02 4.6{ 10(7) 2.54 3.6 6 G5.5 4 95 M 0 0 0 1 2 1 2 1 2 1 1 1 0.93 5.1 15g} 2.38 4.1 6 G55 B 0 0 0 1 1 1 2 1 2 1 1 1 0.97 4.6 72 2.31 4.4 6 G5.3 T 0 0 0 l1 3 1 2 1 1 1 1 1 0.76 4.6 m7 2.89 4.2 6 G59 6 95 M 0 0 0 1 3 1 2 1 1 1 1 1 0.86 5.0 8g 2.54 4.4 7 G6.4 B 0 0 0 1 2 1 2 1 2 1 1 1 0.56 4.7 8g 2.73 4.7 7 G55 T 0 0 1 3 2 1 1 1 1 1 1 0.93 3.5 7g 2.73 4.5 6 G46 6 55 M 0 0 0 1 2 2 1 1 1 1 1 1 0.70 4.1 82 2.16 3.6 6 G47 B 0 0 0 1 1 1 1 1 1 1 1 .1 0.87 3.2 62 1.94 3.1 6 G46 T 0 0 0 1 2 2 1 1 1 1 1 1 0.72 3.7 8g 2.76 3.6 4 G54 7 55 M 0 0 0 1 3 2 1 1 1 1 1 1 0.54 3.4 6g 2.14 3.0 5 G64 B 0 0 0 1 2 1 1 1 1 1 1 1 0.77 3.1 52 2.31 3.2 5 G48 T 0 0 0 1 2 2 1 1 1 1 1 1 1.00 4.2 10g 2.73 3.8 6 G43 8 60 M 0 0 0 1 3 1 1 1 1 1 1 1 0.92 4.6 2.92 3.9 6 G3.9 B 0 0 0 1 1 1 1 1 1 1 1 1 0.54 3.4 5g 3.13 4.3 6 G41 T 0 0 0 1 2 1 1 1 1 1 1 1 0.63 4.5 72 3.00 4.7 7 G54 9 60 M 0 0 0 1 3' 1 1 1 1 V1 1 1 0.63 4.6{ 5(7) 2.81 4.6 6 G56 B 0 0 0 1 2 1 1 1 1 1 1 1 0.70 3.5 6g 3.09 4.2 6 G50 T 0 0 0 1 2 1 1 1 1 1 1 1 1.11 3.3 52 1.86 l 3.2 5 G43 10 60 M 0 0 0 1 2 1 1 1 1 1 1 1 1.12 3.1 82 1.99 3.0 4 G3.7 B 0 0 0 1 1 1 1 1 1 1 1 1 0.94 3.2 52 2.02 3.3 5 G36 Notes to table z 1 T=upper part of ingot; M=n1iddle part of ingot; B=lower part of ingot.

2 1st, 2nd and 3rd signify cylindrical surfaces located 5, 10 and 15 mm. respectively, inside the exterior surface and parallel to the axis. The figures in the columns mean the length of flaws in mm., zero indicating non-existence of aws. I

3 Symbols: T=overall pit; Tc= central pit; L= porous; S=overall segregation; Sc=central segregation; Se=Eyeball segregation; D=dendrlte; B=b1owhole; Bs=skin blowhole; H=hair crack.

The figures 1, 2, and 3 denote best, good and fair results respectively.

The results of the 3-stage flow detection, macro-etching, thereof coated `with solid composition and still further and non-metallic inclusion tests and the grain size of the decreasing the angle of inclination until the open end of crystals in the ingots produced clearly show that the said mold is beneath the pouring opening in said ladle, present method of casting steel ingots is highly satisfacand permitting the coating composition remaining molten tory. to rise to the surface of the steel whereby a solid metal What is claimed and desired to be secured by Letters Oxide barrier is provided between the Steel and the IlgOt Patent is: mold.

1, A method 0f casting Steel ingots which comprises 2. A method aS Set forth in Claim 1 wherein Said metal providing a ladle containing molten steel and a molten oxide composition is one which Will absorb gases and metal oxide composition substantially inert with respect DOD-metalliC material ll thi@ Steel, and Will 110i CI'YSauiZe to the steel and having a substantially lower specic during SOldCatiOIlgravity such that the same rises t0 the surface of the 3. A method aS Set forth in Claim l wherein Said steel, pouring said composition from the surface of the molten metal oxide composition comprises about 60-80% steel into an inclined mold while decreasing the angle of 0f the Volume of Said molten steel.

inclination thereof to bring said composition initially into 4. A method as set forth in claim 1 wherein said Contact with the interior walls of the mold, allowing the molten metal oxide composition comprises about 1525% portion of the composition adjacent the mold walls to by Weight of said molten steel.

solidify, and while further decreasing the angle of inclina- 5. A method as set forth in claim 1 wherein said metal tion poun'ng said steel into said mold over the surfaces 75 oxide composition comprises about 75-85% by weight of a mixture of SiOg, A1203 and CaO in the following prog CaO'.

6. A method of-casting steelingots which comprise metal oxide composition substantiallyinert with respect totfs'aid 'steel and'of substantially lower melting point and' specic Agrau/ity than said steel, pouring said metal oxideY composition into, an inclined ingot mold, while changing the angle of inclination of the mold, to-bring said composition into contact with the Vinterior wall's'of the mold, allowing the portion ofsaid composition contacting said walls to solidify, and pouring said molten steel into said mold in contact with said solidiecl composition, and

further changing said angle of inclination until said ingot an upstanding position at the termination of steel pouring, thereby avoiding direct contact between the ingot walls and the steel, and permitting the portion of said composition remaining molten to rise to the surface of the ingot, thereby providing a solid metal oxide barrier between the steel and the walls of the mold` providing in a ladle quantities of molten steel and molten 5' References Cited in the tile of this patent UNITED'STATES PATENTS 1,734,313 Von Malmbory Nov. 5, 1929 1,834,049 Cooper Dec. 1, 1931 2,278,321 Keir Mar. 31, 1942 2,288,836k Perrin July 7, 1942 2,362,825 Y Hutchins Nov. 14, 1944 2,408,241 Sturbelle Sept. 24, 1946 2,493,394 Dunn Ian. 3, 1950 2,500,556 Mallach Mar. 14, 1950 2,631,344 Vennedy Mar. 17, 1953 McMullen Nov. 30, 1954

Images