3. The role of carbon The agent can not only 3. The role of carbon
Since dolomite clinker is pulverized when exposed to water, anhydrous binder is required for brick making. Generally, they are tar, asphalt, anthracene oil, etc. The organic
bonding prevents hydration, and when it is thermally cracked in the brick, the remaining carbon will greatly improve the performance of the brick. Various attempts have been made to apply asphalt-free bricks in oxygen alkaline converters, and the results have been disappointing. It can be said that residual carbon, like
, is also an important component in dolomite bricks.
When making bricks, the asphalt (or impregnated asphalt) is heated, cracked and separated in an alkaline oxygen converter, so that a small amount of carbon is deposited in the pores of the bricks
to form "Residual carbon" exists in many forms, but in most cases it is compacted at one end of the pore. From
currently known situations show that carbon does not exist in any form. The bonding effect between refractory particles is simply a filler in the pores in the brick. The size, shape and continuity of the residual carbon particles are mainly related to the form of pore closure.
It is related to the size and has little to do with the properties of asphalt.
However, the good effect of a small amount of carbon is undoubtedly the difference between the carbon-containing and non-carbon-containing alkaline oxygen top-blown converters. /p>
Compared with carbon bricks (Figure 9, it can be clearly seen that a small amount of carbon reduces the penetration and transfer of iron oxide into the bricks
.
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Chapter 2 Optimization Design of Dolomite Refractory Production Formula
The obvious difference in the permeability of carbon-containing bricks and carbon-free bricks is also reflected in their use. The erosion rate is uniform and slow, and has a tendency to increase in the later stage. The carbon-free bricks form a metamorphic layer near the working surface, and exhibit considerable structural spalling with variable thickness. . Due to the absorption of iron oxide and silica, the composition of the original brick is changed, so that the composition, high temperature strength, thermal expansion and density of the carbon-free brick change with depth. Compared with this, the composition of the original brick is changed. The properties of carbon bricks do not change much along the depth, showing strong resistance to tissue spalling.
The ability of carbon to inhibit the penetration of slag into depth is a combination of several factors. Generally speaking, this is related to the fact that the residual carbon in the pores can reduce the wettability of the slag. If there are no substances with poor wettability such as carbon in the pores, the slag will go straight. Intrusion
deep into the pores until it solidifies. If messy graphite particles exist in the pores, the slag invasion is limited to the vicinity of the hot surface
In addition, carbon. The pressure generated by oxidation is also a factor in preventing slag penetration.
The important role of carbon can also be explained from the melting relationship, the phase diagram is shown in the figure. /p>
In the following, the reducing atmosphere caused by carbon can make dolomite bricks (such as containing absorbed iron oxide) without liquid
phase. When there is no carbon in the brick, that is, in the air atmosphere , the iron oxide absorbed by the brick begins to melt.
Many studies have been conducted on the carbon content. Therefore, the slag penetration increases rapidly. >To reduce the penetration of slag, the residual carbon content should not be less than
Picture of comparison of the chemical composition of asphalt-containing and asphalt-free magnesia
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Part 4 Optimization Design of Production Formulas for Alkaline and Spinel Refractory Materials
Figure - Isothermal Section of Iron Oxide System
.—Reducing atmosphere (01; 2—in air; 3—magnesium fultenite; 4—magnesium ferrite; 5—liquid phase
The carbon in the brick mainly comes from the organic binder or impregnated material in the brick ( Tar or bitumen. Its carbon content is related to the softening point of the asphalt
and the carbonization temperature (Figure 6. It is better to use high softening point asphalt, and attention should be paid to the appropriate carbonization temperature. In addition
Increase the carbon content The content can be increased by increasing the amount of asphalt and adding an appropriate amount of carbon, such as carbon black.
Simply increasing the carbon content is not enough, because the structure of the carbon has a great impact on the corrosion resistance of the lining bricks. For impregnated bricks, the pore structure and porosity of the bricks should be mainly considered. Of course, bricks with fine pore structure and uniform carbon distribution have better resistance to slag penetration. It is more advantageous than large pore structure and coarse carbon.
Figure 6 The influence of asphalt softening point and carbonization temperature on carbon content
4. Production process of tar dolomite bricks
p>
Tar dolomite bricks are made from sintered dolomite as the main raw material or by adding an appropriate amount of magnesia and using tar asphalt or wax and other organic matter
as a binder. As shown in the figure.
7 The quality of raw materials, the chemical composition and sintering degree of Baiyunyou are related to the properties and use of the product
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Chapter 2 Optimization design of production formula of dolomite refractory materials 79
Service life.
In order to meet the requirements of the oxygen top-blown converter lining, dolomite clinker should be a selected material with high purity and good sintering.
The content,,., and the total amount of impurities should not be greater than, and the volume density should be greater than. 01.0234
56, preferably greater than 03456.
The ingredients of tar dolomite products composed of .0 particles are relatively simple, and a single ingredient is generally used. Sometimes in order to improve its anti-
hydration performance, fine powder can be partially or completely replaced Use magnesia fine powder.
The density and hydration resistance of the product must be considered when mixing the particles, and they also vary depending on the molding method. Coarse-grained dolomite clinker
The specific surface area of ??the material is small, the contact area with air is small, and the hydration resistance is relatively strong. Experimental research and production practice have proven that coarse-grained ingredients are beneficial to improving the density, hydration resistance and erosion resistance of tar dolomite bricks. Currently, the most commonly used critical granularity is 7.366 or 27366.
Although fine powder has the disadvantage of being easily hydrated, it can fill the gaps between large and medium particles, which is beneficial to increase the volume density and sintering of bricks during use
and ensure that the bricks are The boundaries of the shaped surface are neat. At the same time, fine powder can thin the bonding film around large particles, so that the tar will be burned off during use and will not leave excessive pores in the future.
Figure 8.873 Process flow chart of machine-made tar dolomite bricks
During machine pressing, the particles are subject to strong external pressure. If the size of the particles is very different, the stress on the large particles cannot be rapid
p>
And passing it out evenly will cause large particles to be broken.
In order to prevent the particles from breaking, reduce the stress on the particles and quickly and evenly transfer the pressure on the particles to the machine base, the machine press
The molding material should contain appropriate and sufficient amounts of Small and medium particles.
During vibration molding, the particles are not subject to pressure in one direction, but are affected by forces in different directions between the particles. The resulting effect
is not extrusion between particles, but Loose, so there are not many restrictions on the composition of the granules during the process of arranging and fixing the granules
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Part 4 Production Formula of Alkaline and Spinel Refractory Materials Optimized design
Customization. It is not necessary to follow the structure of machine-pressed bricks, but should be similar to the structure of concrete materials in buildings. According to the characteristics of brick particle structure
it can be seen that the use of much larger particles than machine-pressed bricks and the elimination of intermediate particles form a brick with high dispersion and uniformity
The particle structure is reasonable and feasible.
Blank preparation
Sand baking. In order to avoid the reduced fluidity of the binder caused by the cold dolomite clinker absorbing heat during the mixing process of the heated tar asphalt and dolomite clinker, the dolomite sand should also be heated to a sufficiently high temperature. . Baking sand is heating dolomite sand.
If the sand baking temperature is too low, the viscosity of the tar will be increased during the mixing process, resulting in uneven mixing; if the temperature is too high, some of the binder substances will volatilize and change the composition, and Contaminate the operating environment. Generally, the temperature of clinker sand should be controlled at , and only large and medium particles should be baked, and fine powder can be baked or not. The sand baking temperature of Shougang is (machine-made brick material, (vibration forming brick material); Tangshan Iron and Steel Co., Ltd. is; the coarse particles of Shanghai Steel No. 1 Factory are, and the fine powder is.
Sand baking equipment Reverberatory furnaces and vertical heating furnaces are mainly used.
Binder and its preparation. Dolomite sand is a barren material, and appropriate binder must be added during molding.
Tar asphalt, petroleum asphalt, coal tar, anthracene oil, etc. The properties of various binders are shown in the table. The role of magnesia carbon bricks Magnesium carbon bricks
Magnesia carbon refractory materials were developed by the United States in the mid-1960s. After successful development, in the 1970s, the Japanese steelmaking industry began to use magnesia carbon bricks in water-cooled electric arc furnace steelmaking. Currently, magnesia carbon bricks have been widely used in steelmaking around the world and have become a traditional use of graphite. In the early 1980s, magnesia carbon bricks began to be used for the lining of oxygen top blowing converters. Currently, most of the materials used for oxygen top blowing steelmaking furnace linings in the UK are magnesia carbon bricks. The lining life is 1000 to 1500 times, while in Japan, the furnace lining is 1000 times to 1500 times. The service life is 2000 to 2500 times. Aluminum carbon bricks
Aluminum carbon refractory materials are mainly used in continuous casting, protective covers of flat steel billet self-positioning pipelines, underwater nozzles and oil well blasting barrels. The steel produced by continuous casting accounts for more than 90% of the total production, and the UK accounts for 60%. It is made of standard high-strength steel and uses advanced carbon dioxide gas shielded welding to ensure that the machine body is strong and durable. 2. It is made with precision by senior technicians to ensure the accuracy of raw material cutting, parts processing accuracy, and assembly accuracy of the entire machine to ensure fast operation of the entire machine. , stable and reliable. 3. Guide column: using multiple processes such as rough machining, finishing, normalizing and tempering, cylindrical grinding, and chrome plating to ensure high strength, high resistance to distortion, and high wear resistance. 4. Mold: Made of precision-cast manganese steel and surface carburized to ensure a long service life. One-time molding and single-piece assembly greatly reduce the chance of damage and replacement costs.
5. Hydraulic and control systems: The main components are all from well-known brands to prevent pressure relief and leakage. Ensure the long-term and stable operation of the whole machine. 6. Forming system: Using the world's leading high-frequency directional vibration technology, concrete products of various materials and specifications can achieve the best vibration effect and ensure the density of the products. 7. Distribution system: The unique fork-type 360-degree forced distribution system enables fast and even discharging of materials, effectively shortening the distribution time and improving production efficiency.