US3920063A

US3920063A - Top pouring ingot making method using cover flux

Info

Publication number: US3920063A
Application number: US413639A
Authority: US
Inventors: Kantaro Sasaki; Mitsuo Oda
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 1973-03-24
Filing date: 1973-11-07
Publication date: 1975-11-18
Anticipated expiration: 1992-11-18
Also published as: AU458990B2; DE2357874B2; GB1451460A; DE2357874C3; DE2357874A1; SE400493B; AU6235273A

Abstract

In top pouring an ingot using cover flux, a cylindrical, i.e. tubular float is placed within the ingot-making mold. Molten steel is poured into the float while, at the same time, cover flux is continuously supplied to the area between the float and the mold walls. With continued pouring of molten steel, the float moves up and the flux covers the surface of the molten steel. After casting, the float is easily broken down when the ingot is stripped of the mold. The float is made of a light material which is resistant to heat and is easily breakable.

Description

United States Patent 1191 Sasaki et a].

[ TOP POURING INGOT MAKING METHOD USING COVER FLUX [75] Inventors: Kantaro Sasaki, Ashiya; Mitsuo Oda, Oyamazaki, both of Japan [73] Assignees: Sumitomo Metal Industries, Ltd.,

Osaka; Aikoh Co., Ltd., Tokyo, both of Japan [22] Filed: Nov. 7, 1973 [21] Appl. No.: 413,639

[30] Foreign Application Priority Data [58] Field of Search 164/55, 56, 133, 136, 362, 164/281, 123; 249/206, 197

[451 Nov. 18, 1975 FOREIGN PATENTS OR APPLICATIONS 887,556 12/1971 Canada 164/281 1,158,403 7/1969 United Kingdom 164/281 1,141,752 12/1962 Germany 164/56 234,929 7/1964 Austria 249/206 795,978 6/1958 United Kingdom 249/206 993.207 5/1965 United Kingdom 249/206 Primary ExaminerFrancis S. Husar Assistant Examiner-Carl Rowold Attorney, Agent, or Firm-Kurt Kelman [57] ABSTRACT In top pouring an ingot using cover flux, a cylindrical, i.e. tubular float is placed within the ingot-making mold. Molten steel is poured into the float while, at the same time, cover flux is continuously supplied to the area between the float and the mold walls. With continued pouring of molten steel, the float moves up and the flux covers the surface of the molten steel. After casting, the float is easily broken down when the ingot is stripped of the mold. The float is made of a [56] References Cited light material which is resistant to heat and is easily UNlTED STATES PATENTS breakabla 1,073.735 9/1913 c t 1. 164/123 3.262.669 7/1966 249/197 15 Claims, 7 Drawing Flgul'es z u .d 1 11 11 1 mfg U.S. Patent Nov. 18, 1975 Sheet 2 on 3,920,063

US. Patent Nov. 18, 1975 Sheet 3 of3 3,920,063

TOP POURING INGOT MAKING METHOD USING COVER FLUX BACKGROUND OF THE INVENTION The present invention relates to a method for top pouring a steel ingot having good surface and excellent internal cleanliness with very low nonmetallic inclusions.

In bottom pouring of ingots, it is well known to cover the surface of molten steel within the mold with flux such as fly ash, carbon powder, lime, silicon oxide, and aluminum oxide to thereby improve the surface and internal cleanliness of ingot. In the top pouring ingots, however, the use of cover flux was not practical since such flux was carried along by molten steel stream falling from the ladle and could not provide a covering for the molten steel in the mold.

Heretofore, in the top pouring ingot making method, accordingly, it has long been a common practice to use a floatable sprue having a plurality of holes in the walls and bottom which is made to float on the surface of the molten steel, to pour molten steel into said floatable sprue while continuously supplying deoxidizing and cleansing fluxes into the sprue so that the poured mol ten steel will rise quietly within the mold without making any splash and will be solidified. This method, however, has failed to completely obviate the disadvantages of hitherto existing techniques since the additives within the floatable sprue are easily involved into the turbulent stream of the molten steel to contaminate it. On the other hand, since the top pouring ingot making method has a number of advantages in, for example, productivity, inventions which make more effective use of the cover flux in the top pouring method have long been sought.

SUMMARY OF THE INVENTION The present invention provides a method for top pouring an ingot using cover flux by combining the cylindrical float and the cover flux. The first feature of the present invention is to dispose an easily floatable cylindrical i.e. tubular float within an ingot making mold, to continuously supply cover flux to the area between said float and the mold walls, as the float rises on the molten steel. The second feature of the present in vention is to form the float using special materials. Further, the third feature of the present invention is to develop applications of the float.

The first feature of the present invention will be described hereunder in more detail. In the top pouring ingot making method, the cylindrical float is disposed within the ingot making mold prior to the introduction of the molten steel into the mold, then the molten steel is poured into the float to allow it to float on the surface of the molten steel with the rise of the molten steel, the cover flux is supplied to the area between the float and the mold walls to cover the entire surface therebetween to thereby produce steel ingot having excellent surface and internal qualities.

The second feature of the present invention will now be described in more detail. The float used in the method according to the present invention preferably has the properties such that it floats above the surface of the molten steel during the top pouring of the ingot, it is not melted by the molten steel, and that it is easily broken by weak shocks after the ingot has been made.

2 Accordingly, the float is made of light, heat-resistant, and easily broken materials.

The float used in the method according to the present invention is made, as described above with the light, heat-resistant, and easily broken materials, mixing a binder in the materials to give viscosity. The mixture may be shaped into a hollow cylindrical shape, after which the shaped cylinder is dipped into an impregnant to ensure the hardness of the float surfaces and to give it a resistance to fire, and then drying it.

Materials used in the float according to the present invention are as follows:

A. Material to give resistance to fire (hereinafter to be referred to as the refractory inorganic powder material) such as powder material of mixture or compound of inorganic oxides such as SiO M 0 Fe O ZrO Cr O MgO, and C210.

B. Material to give lightness and heat insulation (hereinafter to be referred to as the heat insulating inorganic fiber material) such as one or more than one of natural or artificial inorganic fiber materials such as asbestos, rock wool, slag wool, and kaolin.

C. Material to give porosity and breakability (hereinafter to be referred to as the breakable organic fiber material) such as organic fiber material such as paper, pulp, or

wood fiber.

D. Material to give bindability and improve formability (hereinafter to be referred to as the organic binding material) such as organic binding material such as resins or starches (dextrin and gum arabic).

E. Material to impregnate the surface of the float to secure the surface hardness and to give fire resistance (hereinafter to be referrred to as the hardening and refractory impregnant material) such as aqueous solution of colloidal silica, sodium silicate, or aluminum phosphate;

and/or a suspension of one or more than one of the powders finer than 270 mesh of zirconia, aluminum oxide, and silica;

The float according to the present invention is made of the above described materials in any of the combinations tabulated in Table I.

Note: 0 used X not used The third feature of the present invention is to develop the applications of the float. As an application, the float made of the special materials as described above and having a cover flux integrally plastered or laid on the outer surface thereof is disposed within the ingot mold so that the cover flux plastered or laid on the outer surface of the float may gradually fall off the float surface as the float rises with the pouring-in of the molten steel and continuously supplied onto the surface of the molten steel within the mold.

As another application, the float made of the special materials as described above is disposed at the bottom of the ingot mold, a plurality of rods for guiding the upmovement of the float within the mold are disposed vertically and in parallel to each other around the float, and the cover flux is contained within said guide rods so that, as the float moves up being guided by the rods with the in-pouring of the molten steel, the guide rods may be melted to supply the cover flux from therewithin continuously onto the surface of the molten steel within the mold.

These and other features of the invention will become more apparent upon consideration of the following description taken in connection with the accompanying drawings wherein:

FIG. I is a schematic vertical sectional view illustrative of an embodiment of the top pouring ingot making method using cover flux showing the state at the moment when the pouring of molten steel is just started;

FIG. 2 is a view similar to FIG. 1 showing the state when the molten steel is being poured in;

FIG. 3 is a vertical sectional view of a float used in the method according to the invention;

FIG. 4 is a view similar to FIG. 2 showing another application of the float;

FIG. 5 is a view similar to FIG. 2 showing still another application of the float;

FIG. 6 is a schematic perspective view of the float to be used in the embodiment shown in FIG. 5; and,

FIG. 7 is a longitudinal sectional view of a guide rod to be used in the embodiment shown in FIG. 5.

Embodiments of the present invention will now be described with reference to the drawings. In FIG. I, an ingot mold I, mold plate 2, and feeder head frame 3 are constructed conventionally. Numeral 4 denotes a float, one of the features of the present invention, for preventing splash and turbulent stream of the molten steel. This float 4 is, as illustrated, of a cylindrical or tubular form and is designed to prevent splashing and turbulence of the molten steel while providing the entire surface of the molten steel in the mold with cover flux. The float 4 is preferably formed of light materials that are absolutely or substantially not melted with the molten steel such, for example, as a light refractory material that has a specific gravity smaller than that of the molten steel and, accordingly, floats on the surface of the molten steel. Materials and method for forming the float 4 will be described hereinafter in more detail.

Prior to pouring of molten steel, as shown in FIG. 1, the float 4 is placed on the mold plate 2 in the ingot mold l, and in the space 12 between said float 4 and the inner wall 11 of the mold I there are placed on the mold plate 2 cover flux 7 contained in containers 6 such as boxes or bags of materials highly inflammable by the heat of the molten steel such, for example, as paper, resin, or the like. Altemately, as circumstances may require, the containers 6 containing the cover flux 7 may be suspended from the feeder head frame 3 by means of, for example, wires (not shown).

With such arrangement, when the molten steel 20 within a ladle 8 is poured through a long nozzle attached to a pouring gate 9 of the ladle 8 into the float 4, splashes 21 of the molten steel do not reach inner walls ll of the mold but reach only inner walls 41 of the float 4 as shown in FIG. 1. The containers 6 of the cover flux 6 placed beforehand in the space between the float-4 and the inner'wall 11 of the mold are broken or burned when brought in contact with the poured molten steel to thereby allow the cover flux 7 to cover the entire surface of the molten steel in the mold from the beginning of the pouring of molten steel as shown in FIG. 2.

As the top surface of the molten steel within the mold rises, the float moves up at the center on the surface of the molten steel. This upward movement of the float at the center of the mold is caused naturally by the uprising of the level of the molten steel surface within the mold. To ensure this upward movement of the float it is preferable to provide centripetal guide means 42 such as copper rods of about 5 mmo. If the covering of the flux on the surface of the molten steel within the mold should break during up-rising, it will be necessary to supply the flux additionally into the mold.

As described hereinbefore, one of the features of the present invention is to broaden the application of the float. The first example of the float applications is to plaster or lay a layer of the flux on the outer annular surface of the float so that the flux may be gradually melted by the heat of the molten steel as the level of the molten steel rises within the mold and may be continuously supplied onto the surface of the molten steel within the mold. FIG. 4 shows an example of the application of such float in the top pouring ingot making op- 1 l eration.

In FIG. 4, inner layer 43 of a float 4a is formed of the materials not easily melted by the molten steel, having a density smaller than that of the molten steel, and easily breakable, such, for example, as ordinary refractory materials that are normally in indeterminate form. The inner layer 43 of the float 4a is for efiectively preventing splash and turbulent stream of the molten steel during the pouring of molten steel. Outer layer 44 of the float 4a. is formed of the cover flux containing, for example, C 3%, SiO, 46%, AI,O, 24%, CaO 3.8%, Fe,O, 5%, Na,0 9%, water 0.1%, and ignition loss 9.1% with the aid of a bonding agent. It is preferable that the bonding agent has high room temperature strength and is easily decomposed or melted when brought in contact with the molten steel. While there are several inorganic and organic materials satisfying such conditions among which gum arabic, for example, is most satisfactory.

While the float 4a has been described as an annularly laminated cylindrical or tubular body comprising the inner layer 43 of refractory materials and the outer layer 44 of cover flux, it may be a tubular body having an elliptic or polygonal section. The float 40 may be provided in the bottom with a plurality of cut-outs or other suitable means (not shown) to facilitate the uprising of the molten steel poured into the float. Reference numeral 7a denotes a layer of mixture of the cover flux powder and the fluid cover flux melted from the up-movin g float upon the contact thereof with the molten steel during the pouring operation and covering the surface of the molten steel.

In the pouring operation of molten steel, the float 4a is firstly placed on the bottom of the mold 2 as shown by dotted lines in FIG. 4 and molten steel is poured from a ladle (not shown) into the float 4a, which then moves up with the rising of the surface of the molten steel by the continued pouring as shown by the solid lines in FIG. 4. Splashes 21 and turbulent streams of the molten steel are confined within the float 4a. The outer layer 44 of the cover containing the flux formed on the outer surface of the float 4a is readily released when brought in contact with the up-rising surface of the molten steel and is continuously consumed while releasing flux to cover the surface of the molten steel outside of the float 4a. Accordingly, the cover flux is prevented from flowing into the float or involving in the interior of the steel ingot. Furthermore, since the splashes 21 and turbulent stream of the molten steel are confined within the float 40 as described above, the rising of the molten steel in the neighborhood of the interface between the ingot mold and the molten steel is as smooth as in the bottom pouring method and the resultant ingot has excellent surface and interior properties.

Another example of application of the float according to the present invention will now be described with reference to H6. 5, which is similar to the example shown in FIG. 1 except having a float 4b and guide rods 71. The float 4b, one of the characteristic features of the present invention, comprises, for example as shown in FIG. 6, a cylindrical body 47 including a flange 46 having a plurality of guide holes 45. The float 4b is formed of a light and easily broken down refractory material having the specific gravity smaller than that of the molten steel so as to be floatable on the surface of the molten steel. Into the guide holes 45 of the float 4b are inserted the guide rods 71 each of which is fixed to the upper edge of the feeder head frame 3 by suitable means such, for example, as holder 72 as shown in FIG. 5. The guide rods 71 may be formed of suitable metal but not limited thereto. It is advantageous to form the guide rods 71 in pipes of any material that will be readily melted or broken at the temperature of the molten steel so as to serve both as a guide for the float and supplier means of the cover flux.

As shown in H6. 7, the cover flux 7 is contained within the guide rods 71 comprising tubes formed of a metal or other suitable material that is melted or broken at the temperature of the molten steel. The guide rods 71 may be provided with suitable separators 73 therewithin for dividing the cover flux into a suitable number of portions so that the cover flux may be intermittently supplied with the rising of the level of the molten steel surface within the mold.

ln practicing the method according to the present invention, the float 4b as shown in H0. 6 is placed on the bottom of the mold 1 with the flange 46 up. lnto each of the guide holes 45 provided in the flange 46 is inserted a guide rod 71 containing cover flux 7 therewithin. The guide rods 71 are supported at their upper ends by holders 72 resting on the upper edge of the feeder head frame 3. When the molten steel 20 is poured down through the long nozzle 10 from the pouring gate 9 of the ladle 8, the float 4b rises up to the surface as the surface level of the molten steel rises within the mold 1. At the same time the tip ends of the guide rods 71 in contact with the molten steel are melted and the cover flux 7 contained within the rods 71 is scattered on the surface of the molten steel and forms a cover flux layer 7b thereon. Accordingly, the molten steel is poured into the mold with its surroundings always covered with the cover flux. When the surface of the molten steel reaches the upper surface of the feeder head frame 3 the float 4b solidifies with the feeder head. However, as will be described hereinbelow in detail, the float 4b is broken down by the mechanical shocks caused when the ingot is stripped from the mold. Accordingly, in the method according to the present invention, there is no need to remove the float 6 at the end of each ingot making operation and the working efficiency is considerably increased.

A still further characteristic feature of the present invention is to produce a float that is easily broken down by the mechanical shocks caused upon the stripping of the ingot from the mold. In the top pouring ingot making method using cover flux according to the present invention, the float is left at the top of the ingot after the pouring is finished. Removal of each float by workers is inefficient and sometimes very difficult depending on the conditions of the installations of the ingot making works. In the present invention, accordingly, the float is formed of special material so that the float will be easily broken by the mechanical shocks caused by the stripping of the ingot from the mold. Such float eliminates the necessity to remove the float after the pouring of molten steel is finished, increases the working efficiency of the top pouring ingot making operation, and improves the surface of ingot obtained by the top pouring method.

The basic making method and essential materials of such float have thus been described. Now the typical examples of the float will be described hereinunder.

EX AMPLE l The first example was made on the basis of the Type of Combination No. l in Table l. The essential material of this example was an inorganic refractory powder material (A) consisting of quartz sands and chamottes.

To the inorganic refractory powder material (A) consisting of SiO 82.2% by weight, AI O 6.4% by weight, mo, 5.1% by weight, MgO 2.5% by weight, and CaO 3.8% by weight, was added a breakable organic fiber material (C) consisting of paper and pulp in the proportion by weight A C 22, to the resultant mixture was added an organic binding material (D) consisting of phenol resin in the proportion by weight A C D 100 2.7, to the resultant mixture was added water to make a slurry having a concentration of 20% by weight. This slurry was poured into a metal frame having the dimension, diameter 250 mm, thickness 50 mm, and height 200 mm, and filtered under reduced pressure to form a float. The float thus dried was then placed in an airtight vessel in which the float was dipped in a hardening and refractory impregnant material consisting of a colloidal silica aqueous solution of 30% by weight and allowed to be impregnated for three minutes under the reduced pressure of the vessel of 300 mmHg. The float taken out of the vessel was dried at the room temperature for 24 hours and then at l50C for 3 hours.

The composition (percentage by weight) of the materials forming the float described above it shown in Table 2.

Table 2-continued water 70% by weight EXAMPLE ll This example was made according to the Type of Combination No. of Table l. The fundamental material of this example was a heat insulating inorganic fiber material (B) consisting by mixture of rock wool or slag wool 80% by weight and ammosite asbestos 20% by weight. Chemical analysis of the material (B) was: SiO 53.4% by weight, A1 0 9.3% by weight, Fe O 9.3% by weight, MgO 24% by weight and CaO 4% by weight.

To this heat insulating inorganic fiber material (B) was added the breakable organic fiber material (C) consisting of wood chips in the proportion B C 100 27 by weight. To this mixture was added the organic binding material (D) consisting of phenol resin 4% by weight and starch 1% by weight with said mixture 100% by weight. To the resultant mixture was added water to make a slurry having a concentration of 20% by weight. Thereafter, the float was formed, impregnated, and dried in the same manner as in the Example 1 except that suspension (e of zirconia powder of the fineness lower than 270 mesh was used as the hardening and refractory impregnant material (E). [n this suspension, the proportion of the solid content to water was 80 20.

The composition (percentage by weight) of the materials forming the float described above is shown in Table 3.

Table 3 B. Heat insulating inorganic fiber by weight material (Chemical Composition) SiO, 53.4% by weight rat-,0, 9.3% by weight Fe,O, 9.3% by weight MgO 24% by weight C110 4% by weight Breakable organic fiber 4% by weight material wood Organic binding material 1% by weight phenol resin 4% by weight starch l% by weight Balance water 80% by weight Hardening and refractory impregnant material e, Suspension of zirconia powder zirconia powder 80% by weight water by weight (Note) In the suspension of aluminum oxide,

aluminum oxide 40% by weight water 60% by weight In the suspension of silica powder silica powder 40% by weight water 60% by weight EXAMPLE 1]] This example was made according to the Type of Combination No. 9 of Table l. The fundamental material of the float of this example was a refractory and heat insulating material consisting in mixture of the fundamental material used in Example 1 (the refractory inorganic powder material consisting of quartz sands and charmottes) 85% by weight and the fundamental material used in Example [I (the heat insulating inorganic fiber material consisting of rock wool or slag wool 80% by weight and ammosite asbestos 20% by 8 weight) 15% by weight. Chemical composition of the refractory and heat insulating material (A B) shows the composition of SiO; 66% by weight, A1 0 5.2% by weight, Fe O 6.6% by weight, MgO 5.2% by weight, and CaO 17% by weight.

To this refractory and heat insulating material (A B) was added the breakable organic fiber material (C) consisting of wood in the proportion A B C 100 28 by weight. To this mixture was added the organic binding material (D) consisting of phenol resin and starch in the proportion A B C phenol resin starch 100 3 1 by weight. To the resultant mixture was added water to make it a slurry having a concentration of 20% by weight. Thereafter, the float was formed, impregnated, and dried in the same manner as in the Example 1 except that the suspension (e of sodium silicate aqueous solution 70% by weight and silica powder 30% by weight was used as the hardening and refractory impregnant material (E).

The composition (percentage by weight) of the materials fonning the float described above is shown in Table 4.

(Note) To the aqueous solution of 40 weight concentration, it is advisable to add silica powder in the proportion aqueous solution silica powder 60 40 20 by weight. Further to said aqueous solution may be added zirconia powder and silica powder in the proportion aqueous solution zirconia silica 70 20 10 by weight.

FIG. 3 shows a vertical sectional view of another example of the present invention, namely a float formed in a short tube. In this float, the impregnated layer 48 in a shell-like, i.e. annular form encloses said inner construction material portion 49. During the pouring using this float, the binding agent in the inner construction material portion 49 is gasified and a portion of the gas is burnt whereby the binding agent loses its binding capacity. On the other hand, the shell-like outer layer 49 impregnated with the aqueous solution for giving resistance to fire still keeps its original form atter the completion of pouring. However, this float is easily broken down by the mechanical shocks upon the stripping of the ingot from the mold and, accordingly, has an excellent advantage that it eliminates the operation specifically for removing the float at the end of each pouring operation. The shape and size of the float are, of course, to be understood not to be limited to what are shown in the Figure but to be determined depending on the shape and size of the mold. The depth of the required impregnated layer also should be determined 9 depending on the size of the ingot to be made and for the steel ingot of 3 tons, for example, the depth of 3 mm will be sufficient.

The float thus produced had the properties of: porosity 75%, specific gravity 0.6, bending strength 16 kg/cm, water content 0.5% or less, and the depth of the impregnated layer 3 mm. The float dipped within the molten steel at 1600C for l minutes was found to have kept its original form. In the experiment making eight pieces of three-ton steel ingot in each of the conventional top pouring method and the method according to the present invention, the interior cleanliness of the ingots according to each method was as shown in Table 5.

In Table 5, the classes of interior cleanliness, A, B and C are the results determined according to Japanese Industrial Standards JlS-G-OSSS Microscopic test method of non-metallic inclusions in steel representing, respectively, estimation of Class A inclusion (sulfides, silicates), Class B inclusion (alumina) and Class C inclusion (granular oxides) in billets of 150 mmo produced by rolling the three-ton steel ingots.

According to the method of the present invention, as is clear from the foregoing descriptions, since the molten steel is poured within the float, turbulent stream of the molten steel is prevented, and since the flux covering the surface of the molten steel between the float and the mold wall rises quietly and is supplied to the surface of the molten steel, the entire surface of the steel ingot is covered uniformly by the flux, thereby enabling to produce very easily steel ingot having excellent surface and interior properties. Further, when the float with the structure described above is used in top pouring ingot making, it perfectly performs its function as the float without being broken down during the pouring of molten steel. While it keeps its original form after the pouring is finished, since it is easily broken down by mechanical shocks caused when the ingot is stripped from the mold, the float according to the present invention eliminates the necessity to remove it upon completion of each pouring operation, thereby considerably increasing the efficiency in ingot making operation and improving the surface of the steel ingot thus produced.

We claim:

1. A method of pouring a metal ingot in a mold having an upright wall and a bottom wall, which method comprises:

A. placing a tubular float within an ingot on the bottom wall prior to initiation of pouring of molten metal in said mold, said tubular float having annularly disposed thereabout a contained flux supply, said flux being released upon contact with molten metal for passage to the surface of the molten metal between outer surfaces of the tubular float and said upright wall, said float consisting of a material lighter than said molten metal and solid at the temperature of said molten metal, said float being buoyantly supported by said body of molten metal 10 and rising in said mold as the surface of said body rises during said continuous pouring; and B. pouring continuously molten metal into the tubular float.

2. The method of claim 1 wherein the molten metal is steel.

3. The method of claim 1 wherein said float is formed of(A) breakable organic fiber material and (B) a material selected from the group consisting of refractory inorganic powder material, and heat insulating inorganic fiber material, both (A) and (B) bound by organic binding material, the outer surface of the float being impregnated with hardening and refractory impregnant material.

4. The method of claim 3 wherein the hardening and refractory impregnant material consists of an aqueous solution of a member of the group consisting of colloidal silica, sodium silicate and aluminum phosphate.

5. The method of claim 3 wherein the hardening and refractory impregnant material consists of a suspension of a member of the group consisting of zirconia powder, alumina powder, and silica powder.

6. The method of claim 3 wherein the hardening and refractory impregnant material consists of a suspension of an aqueous solution of a member of the group consisting of colloidal silica, sodium silicate, and aluminum phosphate added with a member of the group consisting of zirconia powder, alumina powder, and silica powder.

7. The method of claim 3 wherein the flux is a member of the group consisting of fly ash, carbon powder, lime, silicon oxide and aluminum oxide.

8. The method of pouring a metal ingot in a mold having an upright wall and a bottom wall, which method comprises:

A. placing a tubular float within an ingot on the bottom wall prior to initiation of pouring of molten metal in said mold, said tubular float having a flange thereabout, said flange having a plurality of guide holes therein, guide rods disposed within said guide holes, the guide rods being vertically disposed and containing flux, said flux being released upon contact with molten metal for passage to the surface of the molten metal between outer surfaces of the tubular float and said upright wall, said float consisting of a material lighter than said molten metal and solid at the temperature of said molten metal, said float being buoyantly supported by said body of molten metal and rising in said mold as the surface of said body rises during said continuous pouring; and

B. pouring continuously molten metal into the tubular float.

9. The method of claim 8 wherein the molten metal is steel.

10. The method of claim 8 wherein said float is formed of (A) breakable organic fiber material and (B) a material selected from the group consisting of refractory inorganic powder material, and heat insulating inorganic fiber material, both (A) and (B) bound by organic binding material, the outer surface of the float being impregnated with hardening and refractory impregnant material.

ll. The method of claim 10 wherein the hardening and refractory impregnant material consists of an aqueous solution of a member of the group consisting of colloidal silica, sodium silicate and aluminum phosphate.

1 1 12. The method of claim wherein the hardening and refractory impregnant material consists of a suspension of a member of the group consisting of zirconia powder, alumina powder. and silica powder.

13. The method of claim 10 wherein the hardening and refractory impregnant material consists of a suspension of an aqueous solution of a member of the group consisting of colloidal silica, sodium silicate, and aluminum phosphate added with a member of the for release with rising level of molten metal.

* k i III

Claims

1. A method of pouring a metal ingot in a mold having an upright wall and a bottom wall, which method comprises: A. placing a tubular float within an ingot on the bottom wall prior to initiation of pouring of molten metal in said mold, said tubular float having annularly Disposed thereabout a contained flux supply, said flux being released upon contact with molten metal for passage to the surface of the molten metal between outer surfaces of the tubular float and said upright wall, said float consisting of a material lighter than said molten metal and solid at the temperature of said molten metal, said float being buoyantly supported by said body of molten metal and rising in said mold as the surface of said body rises during said continuous pouring; and B. pouring continuously molten metal into the tubular float.

2. The method of claim 1 wherein the molten metal is steel.

3. The method of claim 1 wherein said float is formed of (A) breakable organic fiber material and (B) a material selected from the group consisting of refractory inorganic powder material, and heat insulating inorganic fiber material, both (A) and (B) bound by organic binding material, the outer surface of the float being impregnated with hardening and refractory impregnant material.

8. The method of pouring a metal ingot in a mold having an upright wall and a bottom wall, which method comprises: A. placing a tubular float within an ingot on the bottom wall prior to initiation of pouring of molten metal in said mold, said tubular float having a flange thereabout, said flange having a plurality of guide holes therein, guide rods disposed within said guide holes, the guide rods being vertically disposed and containing flux, said flux being released upon contact with molten metal for passage to the surface of the molten metal between outer surfaces of the tubular float and said upright wall, said float consisting of a material lighter than said molten metal and solid at the temperature of said molten metal, said float being buoyantly supported by said body of molten metal and rising in said mold as the surface of said body rises during said continuous pouring; and B. pouring continuously molten metal into the tubular float.

9. The method of claim 8 wherein the molten metal is steel.

11. The method of claim 10 wherein the hardening and refractory impregnant material consists of an aqueous solution of a member of the group consisting of colloidal silica, sodium silicate and aluminum phosphate.

12. The method of claim 10 wherein the hardening and refractory impregnant material consists of a suspension of a member of the group consisting of zirconia powder, alumina powder, and silica powder.

13. The method of claim 10 wherein the hardening and refractory impregnant material consists of a suspension of an aqueous solution of a member of the group consisting of colloidal silica, sodium silicate, and aluminum phosphate added with a member of the group consisting of ziRconia powder, alumina powder, and silica powder.

14. The method of claim 10 wherein the flux is a member of the group consisting of fly ash, carbon powder, lime, silicon oxide and aluminum oxide.

15. The method of claim 8 wherein the guide rods have separators therein for dividing flux into portions for release with rising level of molten metal.