US3132955A - Method for the manufacture of unburned refractory body - Google Patents

Description

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y 1964 NAOYUKI NAMEISHI 3,132,955

METHOD FOR THE MANUFACTURE OF UNBURNED REFRACTORY BODY Filed April 20. 1961 Change of Compressive Srrengrh of ChomoheBonding Clay- Sodium Silicare Sysrem Chdmorre O 90 8O 7O 6O 5O 4O 3O 20 IO 0 5 Com ressive Srren rh is shownb lb 2 No.01 Composirion p g Y An INVENTOR. NAOYUKI NAMEISHI United States Patent 3,132,955 METHOD FOR THE MANUFACTURE OF I UNBURNED REFRACTORY BODY Naoyuki Nameishi, Kakogawa, Japan, assignor to Harima Refractories Company, Limited, Takasago, Japan, a corporation of Japan Filed Apr. 20, 1961, Ser. No. 104,375 3 Claims. (Cl. 106-67) The present invention relates to a refractory body, and more particularly, to an unburned refractory body for use in a sleeve which protects the steel rod attached to the stopper provided in the steel ladle.

As is known to the steel industry, the steel ladle is used to receive the molten steel from the open-hearth furnace or the like, and the molten steel is teemed into the ingot mold through a nozzle and stopper in the bottom of the ladle. The steel rod attached to the stopper must pass down through the molten steel in the ladle and therefore must be protected with refractory sleeves. The refractory sleeve must resist cracking under the sudden heat shock, and also the joints between the sleeves must be carefully fitted so that the molten steel cannot force them apart.

Accordingly, when we take the use of a refractory body for the sleeve into consideration from the safety point of view at the time of pouring the molten metal into the mold, it should be highly resistant to erosion and corrosion as well as thermal shock, and at the same time there should be no danger of the molten steel penetrating into the joints of the sleeves Heretofore, the burned refractory brick has lent itself to the above requirements. However, the burned brick 3,132,955 Patented May 12, 1964 percent by weight of each material while the opposite side represents zero percent. The diagram is divided into ten percent increments of respective materials. For example, the No. 8 composition consists of 70% chamotte, 10% bonding clay and 20% sodium silicate.

Briefly stated, the invention is characterized by the manufacture of an unburned refractory sleeve brick which comprises molding the refractory plastic compositjgn consisting of a hih siliceous c amotte rapid] calcined at a tem erature eetween 900 and 0" l. and a suitable amount of sodium silicate and sodium carbonate pressre, sa 7,0 Ill sq n., m o a sire sae, an t en ryin te molde brick by heatirrg.

"TE: cnnygntional burp ed refmgtory sleeve brick of prior art is manu actured by burning the mixture of a chamotte obtained by firing an aluminous-siliceous mineral material heavily and a W clay at an elevated temperature for an extended period of time into a esire orm with a specified strength. However, in reference to the unburned sleeve brick, the addition of bonding clay thereto would result in the undesirable simultaneous reaction between molten steel and slag as well as sintering when abruptly brought into contact with the molten steel. Consequently, an incomplete bonded part of brick resulting from sintering tends to form silicate through the reaction with the slag due to an inherent high activity of the material itself and therefore the liquid phase takes place readily with the result that the resistance to erosion and corrosion is exceedingly deteriorated on account of the physical action of molten steel and slag. Further, have discovered that hen the strength of the brick itself is imWgsmunemr se in of sodium silii must be subjected to a burning process, which results in a higher cost of manufacture and also in the difiiculty of attaining a uniform size and shape. On the contrary,

the manufacture of an unburned refractory brick without kiln burning gives an exact dimension of size and shape due to the elimination of the burning process, the chief cause of irregular and random dimensions. Consequently, the accuracy of nozzleand stopper assembly resulting from the thin as well as uniform joint of the sleeve obtained by the instant invention may be accomplished together with the increase of productivity and the decrease of manufacturing cost of sleeve brick.

The present invention contemplates overcoming the above difiiculties and has for its object the provision of a novel and improved process of producing a refractory brick for use at high temperatures under eroding as well as corroding conditions.

Accordingly, another object is the provision of novel and improved refractory articles for various uses and which will withstand erosion and corrosion at high temperatures.

A further object is the provision of an improved refractory body which can be simply and economically manufactured in quantity.

The invention further provides a refractory body which can be easily manufactured in relatively complex shapes as well as in the form of rods, bars and tubes and which lends itself to a wide variety of uses where oxidation, erosion and corrosion resistances at high temperatures are desired.

Other objects and advantages of the invention will be apparent from the following description which, taken in connection with the accompanying drawing, discloses a sides, because the brick absorbs moisture in the air. Accordingly, addition of the bonding clay to the refractory sleeve of the invention does not improve the volume stability thereof during service at high temperatures.

A feature of the invention is to provide a high siliceous material consisting predominantly of pyrophy lljt Al O .4SiO .H O

which has been previously calcined rapidly at a temperature of 900 to 1000 C. for a short period of time. The reason why I limit the temperature of calcination of the material to the range of 900 to 1000 C. is as follows: when the high siliceous material consisting chiefly of pyrophyllite is subjected to heating, dehydration begins at the temperature of 450 C. and proceeds gradually in the neighborhod of 900 C., and a dilferent condition other than the original takes place up to the temperature of 1100 C., nevertheless the material retains still its crystal structure. Then, the formation of mullite begins when the temperature exceeds 1100 C. By the rapid calcination of the raw material at a temperature of 900 to 1000 C. lower than that of the formation of mullite, a finely divided particle of the thus calcined material becomes irregular and non-spherical compared to the raw one with the result that it is easily molded into a desired shape, the occurrence of lamination can be prevented, the firm bond between material particles is attained, the decrease of strength due to moisture absorption is considerably avoided, and a suitable amount of highly viscous siliceous substance is formed in the hot state so as to enhance its resistance to thermal shock during service. In addition, the formation of this highly viscous substance prevents the slag from penetrating into the l i E brick, thereby its resistance to erosion and corrosion is much improved.

When the burned sleeve brick is in service, it is often observed that the melt penetrates through the joint thereof. However, the highly siliceous material in accordance with the invention contains free silicate which is characterized by expansion at the temperature used. By this characteristic expansion as well as the formation of the above highly viscous substance, the joints of the sleeve are completely closed to obviate the attack of the molten steel.

In reference to the strength of this unburned sleeve brick during storage and transportation, it is by no means inferior to that of the burned refractory product, because gi wndiememna i kigtithshiehngsutance to abrasion are achieved by t e improved method of the mver'iti'on WElCh comwmehighly siliceo chamotte material into coarse grains and very fine ones in order to remove intermediate ones therefrom, forming the densely packed mixture thereof addin -10% by weight of a water glass solution of (containing 1.5% sodium carbonate ereto, and molding the thus r u der the hi h ressure of Miles per square inc into a desired configuration.

rm e, it is expected that the bonding strength of the unburned brick will be descreased in the intermediate temperature range or the temperature range in which no sintering takes place, but the present invention obviates it by the application of the water glass or sodium silicate solution, The addition of water glass to the mix, the viscosity thereof will be enhanced so that the transfer of particles is lessened and the closeness of packing is also lowered. Therefore, by the addition of sodium carbonate to the mix, workability as well as the bonding strength of particle are enhanced.

The invention will be fully described in reference to the following example:

EXAMPLE Proportions of Ingredients Ingredient Particle size Percent by weight '1. Calcined higlhly siliceous (pyro- Pass No. 6 to No. 18 40-60 phyllitc) c motto. of ASTM 1 sieve. 2. Same as 1 Pass No. IOOOIASTM 60-40 S 676. 3. Water glass 40 Be solution (con- 1 5-10 tains 1.5% sodium carbonate).

1 ASTM-American Society for Testing Material.

Chemical Analysis of Ingredient 1. Calcined highly siliceous (pyrophyllite) chamotte: Percent sio, 80.65 "no, 0.60 A1 0 16.71 Fe O CaO 0.38 MgO 4 0.27 Ignition loss 0.30

Total 99.90

2. Water glass: Na O.3SiO -|nH- O. 3. Sodium carbonate: Na CO 99% or more.

The above calcined highly siliceous (pyrophyllite) chamotte is finely divided to the above specified fineness of particle size, then charged into a mixer, and subsequently to thoroughly mixing and kneading with the addition of the above water glass solution for a period of 7 to 10 minutes.

Thereafter, it is molded under the high pressure of 7,000 to 19,000 pounds per square inch by means of a friction press or oil press into a desired shape, then allowed to dry at room temperature for a period of 24 hours, and

4 finally dried by heating it to the temperature of C. for a period of 24 hours.

The chemical analysis and the physical properties of the unburned sleeve brick obtained by the above manufacturing method are described hereinbelow:

CHEMICAL ANALYSIS Softening point under load at high temperatures acording to JIS (Japanese Industrial Standard), R2209:

T 1060. T, 1245. T 1420.

Refractoriness, Seger Cone (SK) 26.6 (P.C.E. 27).

In reference to 11$ R2209, Method of Test for Softening of Refractory Brick Under Load at High Temperatures, it is briefly stated as follows: when the sample, 50 mm. x 50 mm. of refractory brick is subjected to the load, 2 kg./cm. (28 lb./sq. in.) while heating at the rate of 6 C. per minute, the temperature at which it is beginning to soften shall be T the temperature at which the initial height of the sample has been compressed to 2% be T and the temperature at which it has been compressed to 20% be T The results of the actual test in which the unburned sleeve brick produced in accordance with the method of the invention has been applied to the steel ladle of ton capacity show that it is less eroded than the burned brick of prior art, but it is even and uniformly eroded, the appearance is considerably improved, and no crack takes place which will cause the stopper trouble.

COMPARISON OF EROSION Unburned brick of this invention Burned brick of prior art. +5 mm. (expansion) 5 to 10 mm.

The results of another actual test in which the unburned brick of the invention has been applied as the lining of the steel ladle of 100 ton capacity show that its permanent dimension is longer than that of the burned brick of prior art by 10 to 15 mm., and the service life of the ladle will be longer by 5 to 10 times in service.

In contrast with the burned sleeve brick of prior art, the advantages of the unburned sleeve brick of this invention are enumerated hereinbelow:

(1) Owing to the elimination of a burning step, the manufacturing cost is cheap.

(2) The shape and size of an unburned brick become more accurate than those of a burned one, therefore the irregularity of size becomes less so that the uniformity of joints and thus the thin joint will be attained in the construction of ladle or furnace. v

(3) On account of the expansion property and the formation of a highly viscous substance in the service temperature range, the attack and penetration of the molten steel towards the joints of the unburned sleeve brick can be prevented.

The invention is not limited to the specific method described, but departures may be made therefrom within the scope of the acompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

Having thus described my invention, what I claim is:

1. A method for the manufacture of an unburned refractory body which comprises calcining a highly siliceous pyrophyllite mineral material at a temperature in the range of 900 to 1000 C. to produce a highly siliceous pyrophyllite chamotte, pulverizing said highly siliceous pyropyllite chamotte into a mixture consisting essentially of grains which will pass through a No. 6 to No. 18 ASTM sieve and of grains which will pass through at least a N0. 100 sieve, mixing said pulverized highly siliceous pyrophyllite chamotte and a water glass containing sodium carbonate, molding said mixture in the absence of a bonding clay under a high pressure of about 7,000 to 19,000 pounds per square inch into a desired shape, and then drying said molded refractory body.

2. A method for the manufacture of an unburned refractory brick which comprises calcining a highly siliceous pyrophyllite mineral material at a temperature in the range of 900 to 1000 C. to produce a highly siliceous pyrophyllite chamotte, cooling said chamotte to room temperature, then pulverizing said chamotte into two parts of different particle sizes, one part being pulverized to the particle size which will pass No. 6 to No. 18 sieve specified by the ASTM and the other part to the particle size which will pass No. 100 sieve specified by the ASTM, providing the mixture consisting of to by weight of said pulverized chamotte with the particle size of No. 6 to No. 18 of said ASTM sieve, 60 to 40% by weight of said pulverized chamotte with the particle size of No. of said ASTM sieve added with 5 to 10% weight of the water glass 40 B. solution containing 1.5% sodium carbonate, subjecting said mixture to thorough mixing and kneading, then molding said mixture in the absence of a bonding clay under the high pressure of 7,000 to 19,000 pounds per square inch into a desired shape, and then drying said molded refractory body.

3. An article of manufacture, a sleeve brick for use in the protection of the steel rod attached to the stopper of the steel ladle, said brick being manufactured by the method as claimed in claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 2,952,553 Ilenda et al Sept. 13, 1960

Claims (1)

1. A METHOD FOR THE MANUFACTURE OF AN UNBURNED REFRACTORY BODY WHICH COMPRISES CALCINING A HIGHLY SILICEOUS PYROPHYLLITE MINERAL MATERIAL AT A TEMPERATURE IN THE RANGE OF 900* TO 1000*C. TO PRODUCE A HIGHLY SILICEOUS PYROPHYLLITE CHAMOTTE, PULVERIZING SAID HIGHLY SILICEOUS PYROPYLLITE CHAMOTTE INTO A MIXTURE CONSISTING ESSENTIALLY OF GRAINS WHICH WILL PASS THROUGH A NO. 6 TO NO. 18 ASTM SIEVE AND OF GRAINS WHICH WILL PASS THROUGH AT LEAST A NO. 100 SIEVE, MIXING SAID PULVERIZED HIGHLY SILICEOUS PYROPYHYLITE CHAMOTTE AND A WATER GLASS CONTAINING SODIUM CARBONATE, MOLDING SAID MIXTURE IN THE ABSENCE OF A BONDING CLAY UNDER A HIGH PRESSURE OF ABOUT 7,000 TO 19,000 POUNDS PER SQUARE INCH INTO A DESIRED SHAPE, AND THEN DRYING SAID MOLDED REFRACTORY BODY.

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