CA1046249A - Method for constructing a runner for metal melting furnace - Google Patents
Method for constructing a runner for metal melting furnaceInfo
- Publication number
- CA1046249A CA1046249A CA175,722A CA175722A CA1046249A CA 1046249 A CA1046249 A CA 1046249A CA 175722 A CA175722 A CA 175722A CA 1046249 A CA1046249 A CA 1046249A
- Authority
- CA
- Canada
- Prior art keywords
- refractory material
- runner
- binder
- temperature
- constructing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B7/00—Blast furnaces
- C21B7/14—Discharging devices, e.g. for slag
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Ceramic Products (AREA)
- Treatment Of Steel In Its Molten State (AREA)
- Blast Furnaces (AREA)
- Furnace Housings, Linings, Walls, And Ceilings (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to a method of constructing a runner for transferring molten metal and molten slag from a metal melting furnace. The method comprises constructing the runner by stamping or ramming with a first refractory material having a thermal conductivity of 4 K cal/m.h. °C and comprising as a binder, a carbonaceous volatile-matter containing substance, and applying a second refractory material having a thermal conductivity of 2 K cal/m.h. °C, to the surface of the runner which will be in contact with the molten metal and molten slag. The second re-fractory material comprises clay as a binder and is applied in a thickness smaller than the first refractory material, namely, from 30mm to 150mm in thickness. Heat is then applied to the surface to coke and solidify the first refractory material. The construc-tion time of the furnace has been remarkedly reduced producing a much more efficient overall operation with the formation of pollutants.
This invention relates to a method of constructing a runner for transferring molten metal and molten slag from a metal melting furnace. The method comprises constructing the runner by stamping or ramming with a first refractory material having a thermal conductivity of 4 K cal/m.h. °C and comprising as a binder, a carbonaceous volatile-matter containing substance, and applying a second refractory material having a thermal conductivity of 2 K cal/m.h. °C, to the surface of the runner which will be in contact with the molten metal and molten slag. The second re-fractory material comprises clay as a binder and is applied in a thickness smaller than the first refractory material, namely, from 30mm to 150mm in thickness. Heat is then applied to the surface to coke and solidify the first refractory material. The construc-tion time of the furnace has been remarkedly reduced producing a much more efficient overall operation with the formation of pollutants.
Description
1046Z~9 1 This invention relates to a method for constructing a runner for transferring molten metal or molten slag which is attached to a metal melting furnace such as a blast furnace.
Runners of blast furnaces have previously been constructed by stamping a mixture of the fine part~cles of chamotte or silica sand, fire clay particles (as a binder), and water. In recent years, the pressure of the furnace at its top has become higher with an increase in the size of blast furnaces and the advance of the furnace operating techniques. Thus, the amount of pig iron produced in one furnace cycle and the number of pig iron tapping operations per day have increased, and also the temperature of molten iron or molten slag has become high~r. In addition, because there has been employed a method wherein molten iron and molten slag are transferred simultaneously through the same runner, refractory materials used as linings of the runners are drastically attacked by the molten pig iron and molten slag both chemically and mechanically. Carbon bond refractories using as a binder a carbonaceous material containing volatile matters such as pitch, tar or resin have higher softening temperature under load, higher modulus or rupture at high temperature, and higher abrasion re-sistance at high temperature than the above~mentioned ceramic bond refractories using the fire clay particles as a binder. Since the binder material is carbonaceous and neutral and has a high resistance to chemical attack by molten slag, a method has also been utilized in which a runner is constructed by stamping a re-fractory material comprising as a binder a carbonaceous substance containing volatile matters.
When the runner is made by stamping a mixture consisting of chamotte or silica sand particles, fire clay as a binder, and water, the runner can be used by drying it until the water added -1- ~ ' 10~ 49 1 is removed. However, when it is made by stamping a mixture of chamotte particles and as a binder, a carbonaceous substance con-taining volatile matters such as pitch or tar or resin, the product must be heated for longer period of time by gradually elevating the temperature in order to remove the volatile matters, and there-by to coke and solidify the product. However, the time allowed for the construction of the runner and its drying or heat solidification in front of the biast furnace is determined by the operation of the blast furnace. Of late, with an increase in the number of molten metal tapping operations per day as a result of the increasing size of the blast furnace and the advance of the furnace operating techniques, this construction time is greatly shortened, and especially it is not possible to permit long pexiods of time for the drying of the runner or heat solidifying it after construction.
Furthermore, it is difficult to micro-adjust the heating burner in an operation in front of the furnace. Accordingly, since the runner is heated abruptly at high temperatures after construction, heavy smokes and bad smell are generated from the pitch or tar to pollute the working environment in front of the blast furnace.
Further, since large quantities of the volatile matters are dis-sipated at a time, the runner becomes porous, and since it is heated in air, the surface of the runner is oxidized and burnt to reduce its strength.
An attempt has also been made to avoid its contact with air during heating by coating the surface of the constructed runner with a paste comprising coke powder t chamotte powder, and clay, etc. But since the control of temperature rise cannot be performed in view of the situation mentioned above, satisfactory results cannot be obtained. There is also a method in which blocks of a runner are formed in advance, and gradually heated to remove 10'~249 1 the volatile matter and solidify them, and the blocks are then connected to make a runner. However, it is difficult to choose a joint material for the connecting parts of the blocks, the corrosion of the joint parts is remarkable, and much labor is required for assembling the blocks. ;
The present invention provides a method for constructing a runner for a metal melting furnace such as a blast furnace by using a refractory material comprising as a binder a carbonaceous substance containing volatile substances.
As previously stated, when the runner is constructed with a ceramic bond refractory material comprising a mixture of powdery refractory material such as chamotte particles, fire clay powder as a binder, and water, it is necessary to dry the product before use in order to remove the water. On the other hand, when the runner is constructed with a carbon bond refractory material com-prising refractory powder such as fire clay powder, and a carbo-naceous substance containing volatile matters such as pitch, tar or resin as a binder, the product must be coked and solidified by gradually heating it before use to remove the volatile matters.
When the drying procedure is compared with the solidification by coking, the following can be said.
At the drying the ceramic bond refractory material, the drying of the inside of the materials should be least different from that of the surface since the difference in the extent of drying between the inside and the surface of the refractory material will result in cracks. The rate of evaporation of water from the surface of the refractory material is dependent upon the temperature of the outer atmosphere (heating temperature), humidity and the rate of air flow, and the rate of diffusion of moisture within the refractory material differs according to such factors 104~;;249 1 as the temperature of the refractory material, the amount, shape and size of pores, the temperature difference of the refractory material between the inside and the surface, or the moisture con-tent. Accordingly, the drying conditions such as heating should be determined in the light of these factors. However, since the material to be removed is water, the drying can be considered to have been completed if the temperature of the entire refractory material has reached at least 100C to diffuse moisture on the surface, and the time required for evaporation has elapsed.
The solidification of the carbon bond refractory material by coking is performed by heating the refractory material thereby to remove the volatile matters such as pitch, or tar added as a binder. The volatile matters contained in pitch or tar dirfer from each other in volatilization temperature as, for example, cresol has a boiling point of 200C, naphthalene 218C, light oil 250C, phenanthrene 340Cr and anthracene 342C. Accordingly, for coking and solidifying the carbon bond refractory material, the material may be maintained at temperatures at which the individual substances are volatilized until these substances are volatilized completely. The time required for the completion of the volatile matters contained in a carbonaceous substance such as pitch or tar used as a binder for the refractory material is dependent upon the amounts of the volatile substances, and the amount, shape or size of the pores of the refractory material Therefore, the rate of heating the carbon bond refractory material is determined in the light of these factors. However, generally, up to at least about 600C, the temperature must be raised undex a thoroughly controlled condition. The firing of a carbon product of the carbon bond type such as electrodes is performed after filling coke breeze around the product in order to prevent its - 104f~249 1 deformation during heating and also its oxidation during firing.
When a refractory material comprising as a binder a car-bonaceous substance, such as pitch or tar, which contains volatile matters was formed by the stamping method and solidified by coking, there was a large weight loss if it was heated in air to a tempera-ture of at least 300C, and the strength of the material is drastically reduced. Specifically, a mixture of 10% of natural graphite, 48% of silicon carbide, 30~ of chamotte, and as a binder 12% of pitch and tar combined is heated to a temperature of not more than 200C, kneaded, placed in a mold and formed into an article having a diameter of 50 mm and a height of 50 mm by the stamping method. The article formed was heated in air at a temperature between 100C and 1000C indicated in Table 1. Se-parately, a similar test piece was placed in a vessel made of a refractory material, and coke breeze was filled between the vessel and the test piece to shut off air. Then, the test piece was gradually elevated up to 1000C in the course of 40 hours.
The heated products obtained are tested as to their physical properties. The results are shown in Table 1.
_ _ _ _ _ . , .
Heating Temper- Retain- Weight Amount Compres- Porosity temper- ature ing time loss of sive (%) ature rise (hours) (%) wear strength (C) (hours) (ml) (Kg/cm2) 100 1 3 1.1 0.6 14 11.2 200 1 3 2.9 1.1 87 15.1 300 1 3 6.2 2.2 45 19.8 500 1 3 7.8 4.5 13 32.5 800 2 3 14.5 Meas~ rement im~ ~ossible 1000 2.5 3 16.0 Measurement impossible _ _ _ Comparison Example in which coke breeze was filled 1000 14.0 I ~ 1 6.0 1 0.8 1 135 1 21.7 1 The temperature raising time of 1 to 2.5 hours and the retaining time Gf 3 hours were prescribed on the basis of the conjecture of the situation in which the runner is constructed in front of the blast furnace and heated by gas or heavy oil burners.
The amount of wear is measured as follows: A steel ball having a diameter of 2.3 mm and weighing 8.4 Xg is passed through a ver-tically erected tube having an inside diameter of 24 mm, and let fall onto the surface of a test piece from the height of 4 m.
Then, the amount of wear of the surface of the test piece is measured and expressed by volume (milliliters). Larger values of the amount of wear show greater mechanical wear. T~e compression strength and the porosity are measured by conventional methods used for fire brick.
When the carbon bond refractory material comprising pitch or tar as a binder is heated in air, the weight loss becomes greater at a temperature higher than 300C and the amount of wear becomes greater at a temperature of 200C or above, as compared with the case of heating it in the absence of air. The compression strength is at a maximum when the temperature is 200C, and decreases when the temperature is lower than it. The porosity increases with increasing temperature. Especially at a temperature of 800C or above, the test piece becomes crumb-like, and the amount of wear, compression strength and porosity can not be measured. This is because the rapid heating causes abrupt vola-tilization of the volatile matters in the binder, and the coked carbon and the added graphite also burn.
The present invention was accomplished on the basis of the results of this experiment. Thus, the invention provides a method for constructing a runner for a blast furnace, for example, 3 by using a refractory material comprising as a binder carbonaceous - .
: ~ ~ . ....
`` lO~Z~9 1 substances containing volatile matters such as pitch or tar, and heating the resulting trough to solidify it sufficiently as a result of coking.
The invention will be described further by reference to the accompanying drawings in which:
Figure 1 is a schematic sectional view of a runner in accordance with the method of this invention;
Figure 2 is a schematic sectional view of a runner in accordance with a conventional method;
Figure 3 is a curve diagram showing the temperature rise at the time of heating the runner in accordance with the method of this invention; and Figure 4 is a curve diagram showing the temperature rise - at the time of heating the runner by the conventional method.
Referring to Figure 1, the reference numeral 1 represents an ordinary fire brick, 2, a carbon bond refractory material con-taining as a binder carbonaceous substances containing volatile matters, and 3, a ceramic bond containing clay as a binder. A
gas burner for heating is shown at 4. The reference numeral 5 designates an iron covering which can be omitted by increasing the thickness of fire brick when the runner is of the fixed type.
The characterstic feature of this invention is that a refractory material of the carbon bonded type is formed by stamping or ramming to produce a runner, and the surface of the runner which comes in contact with molten pig iron and molten slag is coated with a ceramic bond refractory material containing clay as a binder in a smaller thickness than in the case of the first-mentioned refractory material. The carbon-bond refractory material used is a mixture of, by weight, 10% of natural graphite, 48% of silicon carbide, 30~ of chamotte, and 12% of pitch and tar combined, which is then 1046~i~49 1 kneaded at a temperature of not higher than 200C. The ceramic bond refractory material is a kneaded mixture of, by weight, 7%
of natural graphite, 40~ of chamotte, 20% of siliceous sand, 15%
of silicon carbide, 18% of clay, and water. In this case, the thickness of the ceramic bond refractory material is 50 mm. The ceramic bond refractory material must cover the entire surface so that the carbon bond refractory material may not be exposed. How-ever, in order to release the volatile matters in the carbon bond refractory material, gas extracting pores or spaces may be provided at places which do not come into contact with molten pig iron and slag. Points A to D show the positions of a thermocouple inserted for temperature measurement. The distances from these points to the surface to which the carbon bond refractory material has been applied are 70 mm for point A, 150 mm for point B, 200 mm for point C, and 250 mm for point D. Point E designates a thermocouple inserted in contact with the surface of the refractory material in order to measure the heating temperature.
Referring to Figure 2, the reference numeral 1 shows an ordinary fire brick, 2, a carbon bond refractory material, 4, a gas burner for heating, and S, an iron covering. Points A' to D' show the positions of a thermocouple inserted for temperature measurement. The distances from the surface to which the refractory material has been applied are 70 mm for point A', 150 mm for point B', 200 mm for point C', and 250 mm for point D'. Point E' de-signates a thermocouple inserted in contact with the surface of the refractory material in order to measure the heating temperature.
The points A to E and points Al to E' are arranged on the line crossing the refractory material applied surface at right angles.
Although not shown in the drawings, a space above the gas burner is covered with an iron plate, and the gas burner is ~O~Z49 1 ignited. The gas is burned while controlling the burner so that the temperatures at the points E and E' are 800C, and then the temperatures at the points A to D and A' to D' are measured~ The results of temperature measurement are shown in Figure 3 (present invention), and Figure 4 (the conventional method). In Figures 3 and 4, the temperature at the starting point is about 80C. This is because the carbon bond refractory material is kneaded at elevated temperatures and stamped while being hot. When the con-ventional method is used, the temperatures of the points A' and B' abruptly rise after igniting the burner, as shown in Figure 4.
It is deemed that a part nearer the refractory applied surface than point A' rapidly attains a temperature near 800C. On the other hand, according to the method of this invention as shown in Figure 3, the temperature rise of point A is very linear, and the average rate of temperature rise up to 600C is about 29 & /hr., which is only slightly higher than the average temperature rising rate (25C/hr.) in the case of heating after coke breeze is filled up. For some time after ignition, no rise in temperature is seen because moisture contained in the ceramic bond refractory material evaporates during this time. The difference in temperature rise between the conventional method and the method of the present invention is that in the method of this invention, heat is gradually transferred to the carbon bond refractory material by the heat transfer resistance of the ceramic bond refractory material since the thermal conductivity of the ceramic bond refractory material stamped on the carbon bond refractory material is 2 K cal/m.h. C, while the thermal conductivity of the carbon bond refractory material is 4 K cal/m.h. G. After heating, test samples are collected from points A, B, A' and B', and the physical properties of these samples are measured. The results are shown in Table 2 below.
" 104~i249 Total car- Amount Compressive Porosity bon content of wear strength (~) (%) (ml) (Kg/cm2) . __ _ . .
Method of present ln-vention Point A 17.5 1.0 122 19.2 Point B 18.1 1.5 103 17.4 . .. . ........ _ Conventional method Point A' 15.4 8.7 32 24.5 Point B' 17.3 5.5 61 22.0 Since the total carbon content calculated of the carbon bond refractory material (the sum of the amounts of graphite and coked pitch and tar) is 17%, it is believed that point A in accord-ance with the method of this invention has been substantially completely coked, and at point B, some amount of the volatile matters is still present. At point A' in accordance with the conventional method, the total carbon content decreases, and this is believed to be due to a partial oxidation and combustion of the binder material. In accordance with the method of this in-vention; the amount of wear and the compressive strength are similar to the case of heating the refractory material after filling coke breeze. Furthermore, according to the method of this invention, no smoking and offensive smell occur during heating, and the situation is quite the same as in the case of drying only a ceramic bond refractory. However, in the conventional method, a large amount of gas is evolved from the refractory applied ~urface, and the combustion of the gas near the surface is observed to cause heavy black smokes and bad smell. The absence of smokes and ~046Z49 1 offensive smell in the method of this invention is considered due to the fact that the volatile matters which are gradually evolved - from the carbon bond refractory material come into contact with the heated ceramic bond refractory material to burn or decompose and be converted to a harmless gas consisting mainly of C02. In other words, the method of this invention is very effective for heating carbon bond refractory materials. It is possible to begin to tap molten pig iron after the drying of the ceramic bond re-fractory material, and to coke and solidify the carbon bond re-fractory material gradually by the heat of the molten pig iron.
Experiments show that if the thickness of the ceramic bond refractory material is less than 30 mm, the rate of temperature rise of the carbon bond refractory material is high and the shut-off of air cannot be effected completely. If the thickness of the ceramic bond refractory material applied exceeds 150 mm, the trans-fer of heat to the carbon bond refractory material is poor, and considerable time is needed to solidify the carbon bond refractory material by coking. Furthermore, if the thickness of the ceramic bond refractory material is less than 150 mm, moisture easily evaporates, and therefore, there is no special necessity to control the burner during heating.
- The carbon bond refractory material that can be used in the present invention may be any refractory material comprising a powdery raw material and as a binder carbonaceous materials con-taining volatile matters. The powdery raw material may be those having fire resistance, but in view of the corrosion resistance to molten pig iron and molten slag, it is prefer~ed to use at least one member of each of the following three groups. The first group comprises chamotte, mullite, a-alumina, siliceous sand and zircon sand. The second group includes silicon carbide, ferro-silicon .
~04~2~9 1 nitride, and silicon nitride. The third group includes natural graphite, artificial graphite, and amorphous carbon.
The ceramic bond refractory material is produced by mixing a powdery raw material, a clay substance as a binder such as fire clay or bentonite, and water. The powdery raw material may be those having fire resistance. However, it should not be corroded so much by molten pig iron and molten slag, because the ceramic bond refractory material needs to cover the carbon bond refractory material until the solidification of the carbon bond refractory material by coking is completed. In order to increase its corrosion resistance, it is effective to add graphite and silicon carbide. However, if the amount of graphite exceeds 20%
by weight or the amount of silicon carbide exceeds 50% by weight, the thermal conductivity becomes excessively high.
The method of this invention can be used not only for constructing runners of blast furnaces but also for the construction of runner of metal melting furnaces.
., A runner was constructed by stamping a carbon bond re-fractory material consisting of, by weight, 10% of natural graphite, 48% of silicon carbide, 30% of chamotte, and 12% of pitch and tar combined as a binder. On top of it, a ceramic bond refractory material consisting of, by ~eight, 7% of natural graphite, 40%
of chamotte, 20% of siliceous sand, 15% of silicon carbide, 18%
of clay, and water was stamped in a th~ckness of 70 mm to form a runner in accordance with this invention. The runner was heated for 4 hours by a gas burner, and then molten pig iron was trans-ferred through it. Without repair, 80,000 tons of molten pig iron could be transferred.
When the runner was built only by using the carbon bond " 104~;~49 1 refractory material, the amount of pig iron tapped was at most 40,000 tons. Accordingly, the runner in accordance with this invention was about two times as durable as that in accordance with the conventional method.
i No smokes and offensive smell occurred during heating by the gas burner and after the beginning of transferring molten pig iron. Same as in the case of constructing the runner only with the ceramic bond refractory material, very good working environment could be maintained.
EX~MPLE 2 A runner was constructed by stamping a carbon bond re-fractory material consisting of, by weight, 8% of natural graphite, 4~ of anthracite as amorphous carbon, 35% of silicon carbide, 15%
of ferro-silicon nitride, 21% of mullite, 6~ of zircon sand, and 11% of pitch and tar combined. On top of it, a ceramic bond re-fractory material consisting of, by weight, 10% of natural graphite, 45% of chamotte, 5% of siliceous sand, 20% of silicon carbide, 20%
of fire clay, and water was stamped in a thickness of 100 mm to form a runner in accordance with this invention. After heating for 4 hours by a gas burner, the trough permitted the transferring of 98,000 tons of pig iron without repair. The durability of this runner was more than two times as high as that constructed only with the carbon bond refractory material in which the amount of molten pig iron transferred was at most 45,000 tons.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
Runners of blast furnaces have previously been constructed by stamping a mixture of the fine part~cles of chamotte or silica sand, fire clay particles (as a binder), and water. In recent years, the pressure of the furnace at its top has become higher with an increase in the size of blast furnaces and the advance of the furnace operating techniques. Thus, the amount of pig iron produced in one furnace cycle and the number of pig iron tapping operations per day have increased, and also the temperature of molten iron or molten slag has become high~r. In addition, because there has been employed a method wherein molten iron and molten slag are transferred simultaneously through the same runner, refractory materials used as linings of the runners are drastically attacked by the molten pig iron and molten slag both chemically and mechanically. Carbon bond refractories using as a binder a carbonaceous material containing volatile matters such as pitch, tar or resin have higher softening temperature under load, higher modulus or rupture at high temperature, and higher abrasion re-sistance at high temperature than the above~mentioned ceramic bond refractories using the fire clay particles as a binder. Since the binder material is carbonaceous and neutral and has a high resistance to chemical attack by molten slag, a method has also been utilized in which a runner is constructed by stamping a re-fractory material comprising as a binder a carbonaceous substance containing volatile matters.
When the runner is made by stamping a mixture consisting of chamotte or silica sand particles, fire clay as a binder, and water, the runner can be used by drying it until the water added -1- ~ ' 10~ 49 1 is removed. However, when it is made by stamping a mixture of chamotte particles and as a binder, a carbonaceous substance con-taining volatile matters such as pitch or tar or resin, the product must be heated for longer period of time by gradually elevating the temperature in order to remove the volatile matters, and there-by to coke and solidify the product. However, the time allowed for the construction of the runner and its drying or heat solidification in front of the biast furnace is determined by the operation of the blast furnace. Of late, with an increase in the number of molten metal tapping operations per day as a result of the increasing size of the blast furnace and the advance of the furnace operating techniques, this construction time is greatly shortened, and especially it is not possible to permit long pexiods of time for the drying of the runner or heat solidifying it after construction.
Furthermore, it is difficult to micro-adjust the heating burner in an operation in front of the furnace. Accordingly, since the runner is heated abruptly at high temperatures after construction, heavy smokes and bad smell are generated from the pitch or tar to pollute the working environment in front of the blast furnace.
Further, since large quantities of the volatile matters are dis-sipated at a time, the runner becomes porous, and since it is heated in air, the surface of the runner is oxidized and burnt to reduce its strength.
An attempt has also been made to avoid its contact with air during heating by coating the surface of the constructed runner with a paste comprising coke powder t chamotte powder, and clay, etc. But since the control of temperature rise cannot be performed in view of the situation mentioned above, satisfactory results cannot be obtained. There is also a method in which blocks of a runner are formed in advance, and gradually heated to remove 10'~249 1 the volatile matter and solidify them, and the blocks are then connected to make a runner. However, it is difficult to choose a joint material for the connecting parts of the blocks, the corrosion of the joint parts is remarkable, and much labor is required for assembling the blocks. ;
The present invention provides a method for constructing a runner for a metal melting furnace such as a blast furnace by using a refractory material comprising as a binder a carbonaceous substance containing volatile substances.
As previously stated, when the runner is constructed with a ceramic bond refractory material comprising a mixture of powdery refractory material such as chamotte particles, fire clay powder as a binder, and water, it is necessary to dry the product before use in order to remove the water. On the other hand, when the runner is constructed with a carbon bond refractory material com-prising refractory powder such as fire clay powder, and a carbo-naceous substance containing volatile matters such as pitch, tar or resin as a binder, the product must be coked and solidified by gradually heating it before use to remove the volatile matters.
When the drying procedure is compared with the solidification by coking, the following can be said.
At the drying the ceramic bond refractory material, the drying of the inside of the materials should be least different from that of the surface since the difference in the extent of drying between the inside and the surface of the refractory material will result in cracks. The rate of evaporation of water from the surface of the refractory material is dependent upon the temperature of the outer atmosphere (heating temperature), humidity and the rate of air flow, and the rate of diffusion of moisture within the refractory material differs according to such factors 104~;;249 1 as the temperature of the refractory material, the amount, shape and size of pores, the temperature difference of the refractory material between the inside and the surface, or the moisture con-tent. Accordingly, the drying conditions such as heating should be determined in the light of these factors. However, since the material to be removed is water, the drying can be considered to have been completed if the temperature of the entire refractory material has reached at least 100C to diffuse moisture on the surface, and the time required for evaporation has elapsed.
The solidification of the carbon bond refractory material by coking is performed by heating the refractory material thereby to remove the volatile matters such as pitch, or tar added as a binder. The volatile matters contained in pitch or tar dirfer from each other in volatilization temperature as, for example, cresol has a boiling point of 200C, naphthalene 218C, light oil 250C, phenanthrene 340Cr and anthracene 342C. Accordingly, for coking and solidifying the carbon bond refractory material, the material may be maintained at temperatures at which the individual substances are volatilized until these substances are volatilized completely. The time required for the completion of the volatile matters contained in a carbonaceous substance such as pitch or tar used as a binder for the refractory material is dependent upon the amounts of the volatile substances, and the amount, shape or size of the pores of the refractory material Therefore, the rate of heating the carbon bond refractory material is determined in the light of these factors. However, generally, up to at least about 600C, the temperature must be raised undex a thoroughly controlled condition. The firing of a carbon product of the carbon bond type such as electrodes is performed after filling coke breeze around the product in order to prevent its - 104f~249 1 deformation during heating and also its oxidation during firing.
When a refractory material comprising as a binder a car-bonaceous substance, such as pitch or tar, which contains volatile matters was formed by the stamping method and solidified by coking, there was a large weight loss if it was heated in air to a tempera-ture of at least 300C, and the strength of the material is drastically reduced. Specifically, a mixture of 10% of natural graphite, 48% of silicon carbide, 30~ of chamotte, and as a binder 12% of pitch and tar combined is heated to a temperature of not more than 200C, kneaded, placed in a mold and formed into an article having a diameter of 50 mm and a height of 50 mm by the stamping method. The article formed was heated in air at a temperature between 100C and 1000C indicated in Table 1. Se-parately, a similar test piece was placed in a vessel made of a refractory material, and coke breeze was filled between the vessel and the test piece to shut off air. Then, the test piece was gradually elevated up to 1000C in the course of 40 hours.
The heated products obtained are tested as to their physical properties. The results are shown in Table 1.
_ _ _ _ _ . , .
Heating Temper- Retain- Weight Amount Compres- Porosity temper- ature ing time loss of sive (%) ature rise (hours) (%) wear strength (C) (hours) (ml) (Kg/cm2) 100 1 3 1.1 0.6 14 11.2 200 1 3 2.9 1.1 87 15.1 300 1 3 6.2 2.2 45 19.8 500 1 3 7.8 4.5 13 32.5 800 2 3 14.5 Meas~ rement im~ ~ossible 1000 2.5 3 16.0 Measurement impossible _ _ _ Comparison Example in which coke breeze was filled 1000 14.0 I ~ 1 6.0 1 0.8 1 135 1 21.7 1 The temperature raising time of 1 to 2.5 hours and the retaining time Gf 3 hours were prescribed on the basis of the conjecture of the situation in which the runner is constructed in front of the blast furnace and heated by gas or heavy oil burners.
The amount of wear is measured as follows: A steel ball having a diameter of 2.3 mm and weighing 8.4 Xg is passed through a ver-tically erected tube having an inside diameter of 24 mm, and let fall onto the surface of a test piece from the height of 4 m.
Then, the amount of wear of the surface of the test piece is measured and expressed by volume (milliliters). Larger values of the amount of wear show greater mechanical wear. T~e compression strength and the porosity are measured by conventional methods used for fire brick.
When the carbon bond refractory material comprising pitch or tar as a binder is heated in air, the weight loss becomes greater at a temperature higher than 300C and the amount of wear becomes greater at a temperature of 200C or above, as compared with the case of heating it in the absence of air. The compression strength is at a maximum when the temperature is 200C, and decreases when the temperature is lower than it. The porosity increases with increasing temperature. Especially at a temperature of 800C or above, the test piece becomes crumb-like, and the amount of wear, compression strength and porosity can not be measured. This is because the rapid heating causes abrupt vola-tilization of the volatile matters in the binder, and the coked carbon and the added graphite also burn.
The present invention was accomplished on the basis of the results of this experiment. Thus, the invention provides a method for constructing a runner for a blast furnace, for example, 3 by using a refractory material comprising as a binder carbonaceous - .
: ~ ~ . ....
`` lO~Z~9 1 substances containing volatile matters such as pitch or tar, and heating the resulting trough to solidify it sufficiently as a result of coking.
The invention will be described further by reference to the accompanying drawings in which:
Figure 1 is a schematic sectional view of a runner in accordance with the method of this invention;
Figure 2 is a schematic sectional view of a runner in accordance with a conventional method;
Figure 3 is a curve diagram showing the temperature rise at the time of heating the runner in accordance with the method of this invention; and Figure 4 is a curve diagram showing the temperature rise - at the time of heating the runner by the conventional method.
Referring to Figure 1, the reference numeral 1 represents an ordinary fire brick, 2, a carbon bond refractory material con-taining as a binder carbonaceous substances containing volatile matters, and 3, a ceramic bond containing clay as a binder. A
gas burner for heating is shown at 4. The reference numeral 5 designates an iron covering which can be omitted by increasing the thickness of fire brick when the runner is of the fixed type.
The characterstic feature of this invention is that a refractory material of the carbon bonded type is formed by stamping or ramming to produce a runner, and the surface of the runner which comes in contact with molten pig iron and molten slag is coated with a ceramic bond refractory material containing clay as a binder in a smaller thickness than in the case of the first-mentioned refractory material. The carbon-bond refractory material used is a mixture of, by weight, 10% of natural graphite, 48% of silicon carbide, 30~ of chamotte, and 12% of pitch and tar combined, which is then 1046~i~49 1 kneaded at a temperature of not higher than 200C. The ceramic bond refractory material is a kneaded mixture of, by weight, 7%
of natural graphite, 40~ of chamotte, 20% of siliceous sand, 15%
of silicon carbide, 18% of clay, and water. In this case, the thickness of the ceramic bond refractory material is 50 mm. The ceramic bond refractory material must cover the entire surface so that the carbon bond refractory material may not be exposed. How-ever, in order to release the volatile matters in the carbon bond refractory material, gas extracting pores or spaces may be provided at places which do not come into contact with molten pig iron and slag. Points A to D show the positions of a thermocouple inserted for temperature measurement. The distances from these points to the surface to which the carbon bond refractory material has been applied are 70 mm for point A, 150 mm for point B, 200 mm for point C, and 250 mm for point D. Point E designates a thermocouple inserted in contact with the surface of the refractory material in order to measure the heating temperature.
Referring to Figure 2, the reference numeral 1 shows an ordinary fire brick, 2, a carbon bond refractory material, 4, a gas burner for heating, and S, an iron covering. Points A' to D' show the positions of a thermocouple inserted for temperature measurement. The distances from the surface to which the refractory material has been applied are 70 mm for point A', 150 mm for point B', 200 mm for point C', and 250 mm for point D'. Point E' de-signates a thermocouple inserted in contact with the surface of the refractory material in order to measure the heating temperature.
The points A to E and points Al to E' are arranged on the line crossing the refractory material applied surface at right angles.
Although not shown in the drawings, a space above the gas burner is covered with an iron plate, and the gas burner is ~O~Z49 1 ignited. The gas is burned while controlling the burner so that the temperatures at the points E and E' are 800C, and then the temperatures at the points A to D and A' to D' are measured~ The results of temperature measurement are shown in Figure 3 (present invention), and Figure 4 (the conventional method). In Figures 3 and 4, the temperature at the starting point is about 80C. This is because the carbon bond refractory material is kneaded at elevated temperatures and stamped while being hot. When the con-ventional method is used, the temperatures of the points A' and B' abruptly rise after igniting the burner, as shown in Figure 4.
It is deemed that a part nearer the refractory applied surface than point A' rapidly attains a temperature near 800C. On the other hand, according to the method of this invention as shown in Figure 3, the temperature rise of point A is very linear, and the average rate of temperature rise up to 600C is about 29 & /hr., which is only slightly higher than the average temperature rising rate (25C/hr.) in the case of heating after coke breeze is filled up. For some time after ignition, no rise in temperature is seen because moisture contained in the ceramic bond refractory material evaporates during this time. The difference in temperature rise between the conventional method and the method of the present invention is that in the method of this invention, heat is gradually transferred to the carbon bond refractory material by the heat transfer resistance of the ceramic bond refractory material since the thermal conductivity of the ceramic bond refractory material stamped on the carbon bond refractory material is 2 K cal/m.h. C, while the thermal conductivity of the carbon bond refractory material is 4 K cal/m.h. G. After heating, test samples are collected from points A, B, A' and B', and the physical properties of these samples are measured. The results are shown in Table 2 below.
" 104~i249 Total car- Amount Compressive Porosity bon content of wear strength (~) (%) (ml) (Kg/cm2) . __ _ . .
Method of present ln-vention Point A 17.5 1.0 122 19.2 Point B 18.1 1.5 103 17.4 . .. . ........ _ Conventional method Point A' 15.4 8.7 32 24.5 Point B' 17.3 5.5 61 22.0 Since the total carbon content calculated of the carbon bond refractory material (the sum of the amounts of graphite and coked pitch and tar) is 17%, it is believed that point A in accord-ance with the method of this invention has been substantially completely coked, and at point B, some amount of the volatile matters is still present. At point A' in accordance with the conventional method, the total carbon content decreases, and this is believed to be due to a partial oxidation and combustion of the binder material. In accordance with the method of this in-vention; the amount of wear and the compressive strength are similar to the case of heating the refractory material after filling coke breeze. Furthermore, according to the method of this invention, no smoking and offensive smell occur during heating, and the situation is quite the same as in the case of drying only a ceramic bond refractory. However, in the conventional method, a large amount of gas is evolved from the refractory applied ~urface, and the combustion of the gas near the surface is observed to cause heavy black smokes and bad smell. The absence of smokes and ~046Z49 1 offensive smell in the method of this invention is considered due to the fact that the volatile matters which are gradually evolved - from the carbon bond refractory material come into contact with the heated ceramic bond refractory material to burn or decompose and be converted to a harmless gas consisting mainly of C02. In other words, the method of this invention is very effective for heating carbon bond refractory materials. It is possible to begin to tap molten pig iron after the drying of the ceramic bond re-fractory material, and to coke and solidify the carbon bond re-fractory material gradually by the heat of the molten pig iron.
Experiments show that if the thickness of the ceramic bond refractory material is less than 30 mm, the rate of temperature rise of the carbon bond refractory material is high and the shut-off of air cannot be effected completely. If the thickness of the ceramic bond refractory material applied exceeds 150 mm, the trans-fer of heat to the carbon bond refractory material is poor, and considerable time is needed to solidify the carbon bond refractory material by coking. Furthermore, if the thickness of the ceramic bond refractory material is less than 150 mm, moisture easily evaporates, and therefore, there is no special necessity to control the burner during heating.
- The carbon bond refractory material that can be used in the present invention may be any refractory material comprising a powdery raw material and as a binder carbonaceous materials con-taining volatile matters. The powdery raw material may be those having fire resistance, but in view of the corrosion resistance to molten pig iron and molten slag, it is prefer~ed to use at least one member of each of the following three groups. The first group comprises chamotte, mullite, a-alumina, siliceous sand and zircon sand. The second group includes silicon carbide, ferro-silicon .
~04~2~9 1 nitride, and silicon nitride. The third group includes natural graphite, artificial graphite, and amorphous carbon.
The ceramic bond refractory material is produced by mixing a powdery raw material, a clay substance as a binder such as fire clay or bentonite, and water. The powdery raw material may be those having fire resistance. However, it should not be corroded so much by molten pig iron and molten slag, because the ceramic bond refractory material needs to cover the carbon bond refractory material until the solidification of the carbon bond refractory material by coking is completed. In order to increase its corrosion resistance, it is effective to add graphite and silicon carbide. However, if the amount of graphite exceeds 20%
by weight or the amount of silicon carbide exceeds 50% by weight, the thermal conductivity becomes excessively high.
The method of this invention can be used not only for constructing runners of blast furnaces but also for the construction of runner of metal melting furnaces.
., A runner was constructed by stamping a carbon bond re-fractory material consisting of, by weight, 10% of natural graphite, 48% of silicon carbide, 30% of chamotte, and 12% of pitch and tar combined as a binder. On top of it, a ceramic bond refractory material consisting of, by ~eight, 7% of natural graphite, 40%
of chamotte, 20% of siliceous sand, 15% of silicon carbide, 18%
of clay, and water was stamped in a th~ckness of 70 mm to form a runner in accordance with this invention. The runner was heated for 4 hours by a gas burner, and then molten pig iron was trans-ferred through it. Without repair, 80,000 tons of molten pig iron could be transferred.
When the runner was built only by using the carbon bond " 104~;~49 1 refractory material, the amount of pig iron tapped was at most 40,000 tons. Accordingly, the runner in accordance with this invention was about two times as durable as that in accordance with the conventional method.
i No smokes and offensive smell occurred during heating by the gas burner and after the beginning of transferring molten pig iron. Same as in the case of constructing the runner only with the ceramic bond refractory material, very good working environment could be maintained.
EX~MPLE 2 A runner was constructed by stamping a carbon bond re-fractory material consisting of, by weight, 8% of natural graphite, 4~ of anthracite as amorphous carbon, 35% of silicon carbide, 15%
of ferro-silicon nitride, 21% of mullite, 6~ of zircon sand, and 11% of pitch and tar combined. On top of it, a ceramic bond re-fractory material consisting of, by weight, 10% of natural graphite, 45% of chamotte, 5% of siliceous sand, 20% of silicon carbide, 20%
of fire clay, and water was stamped in a thickness of 100 mm to form a runner in accordance with this invention. After heating for 4 hours by a gas burner, the trough permitted the transferring of 98,000 tons of pig iron without repair. The durability of this runner was more than two times as high as that constructed only with the carbon bond refractory material in which the amount of molten pig iron transferred was at most 45,000 tons.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
Claims
1. A method of constructing a runner for transferring molten metal and molten slag from a metal melting furnace, which comprises constructing the runner by stamping or ramming with a first refractory material having a thermal conductivity of 4 K
cal/m.h. °C and comprising as a binder, a carbonaceous substance containing volatile matter, applying to the surface of said runner which will be in contact with said molten metal and molten slag, a second refractory material having a thermal conductivity of 2 K
cal/m.h. °C and comprising clay as a binder in a thickness smaller than that of first refractory material applied, the thickness of said second refractory material being from 30 mm to 150 mm, and said clay containing refractory material having a lower thermal conductivity than said first refractory material, and applying heat to said surface to coke and solidify the refractory material containing the carbonaceous substance by the gradual transfer of heat to the carbon bond refractory material due to the lower thermal conductivity of the clay-containing refractory material.
cal/m.h. °C and comprising as a binder, a carbonaceous substance containing volatile matter, applying to the surface of said runner which will be in contact with said molten metal and molten slag, a second refractory material having a thermal conductivity of 2 K
cal/m.h. °C and comprising clay as a binder in a thickness smaller than that of first refractory material applied, the thickness of said second refractory material being from 30 mm to 150 mm, and said clay containing refractory material having a lower thermal conductivity than said first refractory material, and applying heat to said surface to coke and solidify the refractory material containing the carbonaceous substance by the gradual transfer of heat to the carbon bond refractory material due to the lower thermal conductivity of the clay-containing refractory material.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6791872A JPS533321B2 (en) | 1972-07-08 | 1972-07-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1046249A true CA1046249A (en) | 1979-01-16 |
Family
ID=13358754
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA175,722A Expired CA1046249A (en) | 1972-07-08 | 1973-07-05 | Method for constructing a runner for metal melting furnace |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS533321B2 (en) |
| BE (1) | BE802047A (en) |
| CA (1) | CA1046249A (en) |
| DE (1) | DE2334529A1 (en) |
| ES (1) | ES416701A1 (en) |
| FR (1) | FR2192175B1 (en) |
| GB (1) | GB1415748A (en) |
| IT (1) | IT989778B (en) |
| NL (1) | NL7309406A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CS171033B1 (en) * | 1974-09-30 | 1976-09-15 | ||
| JPS5366078A (en) * | 1976-11-24 | 1978-06-13 | Matsushita Electric Ind Co Ltd | Method for working synthetic resin plates |
| JPS55144138A (en) * | 1979-04-30 | 1980-11-10 | Toyoda Gosei Co Ltd | Compressing valcanizer |
-
1972
- 1972-07-08 JP JP6791872A patent/JPS533321B2/ja not_active Expired
-
1973
- 1973-07-05 CA CA175,722A patent/CA1046249A/en not_active Expired
- 1973-07-05 NL NL7309406A patent/NL7309406A/xx not_active Application Discontinuation
- 1973-07-06 IT IT5129373A patent/IT989778B/en active
- 1973-07-06 DE DE19732334529 patent/DE2334529A1/en not_active Withdrawn
- 1973-07-06 BE BE133236A patent/BE802047A/en unknown
- 1973-07-07 ES ES416701A patent/ES416701A1/en not_active Expired
- 1973-07-09 GB GB3264773A patent/GB1415748A/en not_active Expired
- 1973-07-09 FR FR7325104A patent/FR2192175B1/fr not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BE802047A (en) | 1973-11-05 |
| AU5784573A (en) | 1975-01-09 |
| IT989778B (en) | 1975-06-10 |
| JPS4927437A (en) | 1974-03-11 |
| DE2334529A1 (en) | 1974-01-24 |
| NL7309406A (en) | 1974-01-10 |
| JPS533321B2 (en) | 1978-02-06 |
| ES416701A1 (en) | 1976-06-01 |
| GB1415748A (en) | 1975-11-26 |
| FR2192175A1 (en) | 1974-02-08 |
| FR2192175B1 (en) | 1983-08-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3212600B2 (en) | Refractory material bound by sialon substrate and method of preparation | |
| US3030228A (en) | Refractory furnace linings and process for producing same | |
| US4605635A (en) | Carbon-containing refractory | |
| CN1050591C (en) | Fired microporous carbon-aluminium brick | |
| CN101798232A (en) | Preparation method of Sialon-carbofrax-corundum composite refractory material | |
| CN107140950A (en) | A kind of preparation method of sucrose combination MgO C fire resistant materials | |
| CA1046249A (en) | Method for constructing a runner for metal melting furnace | |
| NO149692B (en) | HEAT STORAGE, CERAMIC, IRON-OXYENTIC STONE BASED ON OLIVINE AND PROCEDURES IN PRODUCING THEREOF | |
| KR0126863B1 (en) | Refractory ceramic mass | |
| US2567088A (en) | Refractory material and method of making | |
| JPS5917072B2 (en) | Massive refractories for hot-insertion repair | |
| JPH0146473B2 (en) | ||
| JPS629553B2 (en) | ||
| JPS6243948B2 (en) | ||
| Barrett et al. | Fused Magnesia Crucibles | |
| GB1593161A (en) | Refractory materials | |
| JPH0421625B2 (en) | ||
| JPS6374973A (en) | Kiln repairing material | |
| JPS6041016B2 (en) | refractory | |
| SU857685A1 (en) | Ore smelting furnace lining | |
| JPS59131563A (en) | Carbon containing refractories | |
| JPH0354155A (en) | Production of graphite-containing brick for lining of melted metallic vessel | |
| US271437A (en) | Geoege uueyee | |
| SU851794A1 (en) | Composition for self-sintering electrode mass | |
| US3410930A (en) | Method of improving the operation of a cupola |