Multipurpose ceramic bonded carbon-containing refractories

The production process of multi-purpose ceramic-bonded corundum-based carbon-containing refractories was studied and developed under the industrial conditions of Magnesia bricks. Explored the microstructure characteristics of this material, production process and damage mechanism. The physical ceramic properties and high temperature performance of the material are listed and compared with the performance specifications of the optional refractory ceramics. Determined the unique properties of this material, advantages and the possibility of wide application.

How to improve the production potential of the metallurgical kiln and the potential use of its working lining are the world's major problems facing the refractory and metallurgical industries. One of the most promising directions for ferrous metallurgical and non-ferrous metallurgical refractory materials (particularly those for converter furnace lining products, ladle products, sliding nozzle products) is the use of various additives (crystallized laurel, zirconia, etc.) The carbon-containing composite material, which facilitates the formation of ceramic carbide binders and nitride binders, significantly improves the thermo-mechanical properties of the refractory material.

Under the industrial conditions of Magnesium Brick Co., Ltd., the production process of ceramic bonded corundum carbon-containing refractories was studied and formulated. According to the Russian national standard rCT 28874-90, this material is of the carbonaceous material type. According to the classification of the chemical composition of refractory materials, this material belongs to the category of carbonaceous materials and its carbon content is between 4% and 40%. As granular aggregates, fused corundum or sintered corundum is used.

The chemical composition of the product is shown in Table 1. Table 1 Chemical composition of the product before the test/% (mass) Product No. Product name Burning minus Si metal Corundum Carbonaceous product Magnesium Carbonaceous product Magnesium product Cast spinel product Table 2 The traditional production process of various refractory materials before (molecules) and after (denominator) trials is a multi-process process, ie 5 processes.

A common finely pulverized mixture is prepared, which consists of several components with different proportioning schemes. Various additives are added to the finely pulverized components, including surface active materials, to ensure that the refractory material has the best thermal properties and erosion resistance, and its service life is extended.

Prepare raw materials, implement ingredients and make peat.

The physical ceramic performance specifications of the overbaked product blanks are shown in Table 2. The cured products were placed in a tunnel kiln and buried in coke crumb at 152 (RC was sintered.

Physical Ceramics Performance Index for Refractory Products Product Number Open Porosity Volume Density Compressive Strength Recommended for Refractory Materials (Nol) and similar Refractories, ie, Magnesia Carbonaceous Refractories (No 2), Magnesia Refractories ( See Table 2 for comparison of physical ceramic performance indexes between No3) and magnesium spinel refractory (No4). The linear thermal expansion coefficient data are shown in Table 3. Table 3 Linear thermal expansion coefficient and relative elongation of various refractory materials AL /U Temperature range /VNolNo2Nq3Nq4 Use before W Before use + Before use m version before use'/% Linear thermal expansion coefficient/% Linear thermal expansion coefficient/10-61/% Linear thermal expansion coefficient/% Linear thermal expansion coefficient/UK-1 L/I/% Linear Thermal Expansion The microstructure of the Nol product is characterized by the densely packed corundum aggregate particles, which are held together by a matrix of finely divided components. Unlike No2, No3, and No4 products, Nol products have high thermal shock resistance and re-calcination strength due to the successful combination of particle composition of the batch ingredients and their special microstructure (ie, ceramic bonding). The influence of high temperature treatment of a certain process on the refractories will restrict the formation of ceramic bonds. In the heat treatment, the following basic reactions occur during the formation of minerals at high temperature, the formation of which has been found, and the presence of the above-mentioned formations was confirmed by electron probe X-ray microanalysis method: the aluminum oxide composite oxide was observed and Silicon solid solution (see Figure I, 3). The newly formed ceramic binder (predominantly a silicon carbide binder) exists in an amorphous form, which binds the particles of the finely pulverized components together. Due to the low linear expansion, this silicon carbide product has not allowed the free expansion of the corundum particles it surrounds, and thus has a limiting effect on the decrease of the total expansion rate of the entire product.

The compressive strength of the bricks heat-treated at 200 feet is only 8 MPa, and due to the formation of the ceramic binder, the compressive strength of the entire finished product is increased to an average of 144.7 MPa. Nol compounded products, in particular skateboards used as sliding nozzles The steel company carried out tests when pouring molten steel in large tonnage ladle, showing a reliable service life of at least 2 times. Its chemical composition and mineral composition after use are shown in Table 4. Table 4 Chemical composition and mineral composition of corundum-containing carbonaceous products After use, microfabricated layer f layer contact layer cast hole chemical composition/% burning reduction mineral Composition/% (volume) Corundum Silicate Carbonaceous Material Metallic Silicon Carbide and Aluminum Carbide Others The macroscopic study of the slide after use, as well as the results of optical microscopic studies and electronic microscopic analysis, show that no belt is formed in the slide during use. Floor. The skateboard is uniformly dark gray to black, and only near the sliding work surface, intermittent working layers are found at the intersection of the casting hole surface and the plane and the casting hole, and the thickness is 0.5-2.5mm. No metal and slag immersion fireproof have been observed. Within the material, the contact surface is smooth, straight, and straight (see the comparison with the microstructure of the skateboard before use. The microstructure of the cold face of the skateboard after use does not change much, showing a slight increase in the total porosity.

The damage mechanism of slides for sliding gates during casting of molten steel is usually the damage to the refractories at the beginning of use. The reasons are as follows: due to thermal shock, radial cracks are formed around the casting holes; the working surface is peeled off; and the high temperature chemistry of molten steel and slag is received. Erosion; contact surface pressure; and wear in the final stages. Skeleton resistance depends on many factors, but also in several forms: the structural damage resistance, slag layer resistance to damage and thermodynamic damage resistance. According to reports, the damage resistance can be classified as the anti-destructiveness of the organizational structure under the circumstances we studied. Factors that cause damage to the refractories in this case include: slag erosion - chemical attack of molten metal and slag melts; decreased structural strength; cracking due to thermal stress, contact pressure, and bending forces; clamping force and scouring Sexual mechanical damage and so on.

According to the results of microscope studies, the damage mechanism of corundum-containing carbon-based skateboards is slightly different. According to a variety of damage factors can be divided into two damage mechanisms: skateboard sliding surface damage; skateboard cast hole wall damage. In the former case, the erosive damage is mainly at work; in the latter case, the erosive damage at the pressure of the molten metal flow plays a role (see below).

The corundum carbon-containing slide has a higher strength and a lower linear thermal expansion rate, so that it can make the slide effectively resist the effect of heat load and cracking.

Since the slide has a fine pore structure (the pores in the finely pulverized components are mainly discrete discontinuous pores, which are round and have a diameter of 2040 pm), the composition of the ingredients is the best and the ingredients of the ingredients have various higher unique properties, making the skateboard It has the property of being not easily wetted by molten metal, so the molten metal and slag melt have very little effect on its erosion and erosion (see).

The corundum-containing carbon-based refractories (No. 1 product) doped with a human agent are relatively new types of refractory materials that meet the requirements of users and are superior to those of magnesium products (No. 2), magnesium-carbon products (No. 3), and magnesium. Spinel products (No4) have a series of advantages. Such refractories have good physical ceramic performance indicators and good linear thermal expansion before and after use. The linear thermal expansion rate of the NolNo4 refractory product in the temperature range of 20 to 900 indicates that the linear thermal expansion rate of the Nol refractory product is 0.5 times lower than that of the magnesium carbonaceous product, and that the ratio is lower than that of the magnesium product and the magnesium spinel product. 11.5 times lower. This is constrained by several reasons.

First, the linear thermal expansion coefficient of a refractory ceramic depends on the material itself consisting of several materials because the total linear thermal expansion rate is obtained by adding the linear thermal expansion rates of the materials (for example, the linearity of corundum and crystalline silicon. The thermal expansion rate is lower than that of periclase). The use of materials with a low linear thermal expansion rate will also affect the thermal shock resistance and mechanical strength.

Second, the linear thermal expansion coefficient of a refractory ceramic depends on its microstructure. In a carbonaceous material, it depends in many ways on the particle size of the added carbonaceous material. In a magnesium material, the index depends on the particle size. The shape and composition of the particles.

(a) lists the relationship between relative elongation and temperature of various refractory materials. It is well known that the corundum-containing carbonaceous material has the lowest relative elongation, and also has the lowest coefficient of linear thermal expansion at temperatures below 900 T (see, 6). It is the most suitable raw material for the manufacture of multi-purpose products for various metallurgical kilns, and is particularly suitable for the production of sliding plates for ladle slides.

In terms of mechanical compressive strength indicators, the above materials show their own distinct distinctiveness (see Table 2). The strength of the corundum-containing carbonaceous material doped with a human addition agent is higher than that of the magnesium material, the magnesium carbonaceous material, the magnesium spinel material, and the like. 52 times, the average is 144.7 MPa. And after the test (in the case we studied, it refers to slides for sliding nozzles), that is, after casting 2 times of molten steel, its strength is 0.51.0 times higher than that before use. The significant differences in the strengths of the materials we have developed and other materials studied, and the dramatic increase in the compressive strength of CTa after the use of carbon-containing products, and the addition of various additive agents and manufacturing processes to them. Characteristics are closely related. In this case, the increase in mechanical strength is mainly achieved by adding crystals to the crystal. Under certain conditions, the addition of a sufficient amount of crystalline silicon can cause the material to undergo a chemical reaction, resulting in the re-formation of a silicon carbide binder (see, a-B) D. The material is linear after use in the 20 to 200 and 20 to 650 temperature range. The thermal expansion rate is only slightly reduced (see). This shows that the strength of the material has been improved, that is, the formation of a ceramic binder between silicon carbide and corundum, and the formation of aluminum carbide and composite oxide carbide solid solution (see, B), that is, the formation of carbides at high temperatures is Continuously. This was also confirmed by the following observations: Prior to use, the product was observed to have not participated in the reaction after 1520 calcination (see Table 1).

The physical ceramic properties (bulk density, open porosity, etc.) of various refractory materials are shown in Table 2. The density indices of the materials are almost the same, in other words, within a range. Regarding the open porosity, the corundum-containing carbonaceous material and the magnesium-carbonaceous material are superior to the magnesium-based ones. Due to the characteristics of the microstructure, the open porosity of the former is one time lower than that of the latter. That is to say, due to the addition of carbonaceous substances, the fine pore structure is formed in the refractory material, and the size of the pores is concluding. Under the industrial conditions of Magnesium Bricks Corporation, the production of ceramic-bonded corundum-containing carbon-containing refractories was studied and formulated. Process and applied to practice. Point out the possibility of producing such refractories and its development prospects.

Compared with magnesium-free refractories and magnesia-based refractories without additives, the refractories with the addition of human agents can form high-strength ceramic binders again, and thus show their microstructure, thermal properties and physical ceramic properties. A certain degree of superiority.

It was found and confirmed that the mechanical strength of the corundum-containing carbon-containing product after its use was significantly increased by 0.5 to 1 times, and it was also ascertained that the refractory material was in the range of 20 to 20 (n: and ~650: The linear thermal expansion rate decreases.

Ming, corundum carbon-containing skateboards have poor wettability, and are characterized by their microstructure and mineral phase composition.

The preliminary results of the production of ceramic-bonded carbon-containing refractories show that the material has a low linear thermal swell rate and high mechanical strength. It is a unique material with good thermal shock resistance and high damage resistance. Can be widely used in various metallurgical kiln and device.

The manufacturing process of such a refractory material should be improved step by step to explore its damage mechanism and damage characteristics, thereby significantly increasing its service life and extending the life of the metallurgical furnace liner several times.

3236 Li Lianzhou School (September 22) The Latest Development of Cordierite Zircon Composites Using Industrial Cordierite Powder plus 10% Zircon (ZrSiCK) Molded Cordierite-Zircon Ceramic Composites material. The sinterability of cordierite can be improved by adding ZrSi04 to form a glassy phase. When the amount of zircon added exceeds 2.5%, there is no further effect on the mechanical properties of the composite. When the addition amount of zircon is 2.5%, the maximum bending strength is (84±7>MPa, which is 30% higher than that of pure cordierite. The cordierite with ZrSi042.5% increases with the temperature to 1300T. Due to the densification, its strength increases, but when the temperature exceeds 130 (TC, due to the formation of a large number of glass phases, its strength decreases. With the addition of ZrSi04, the average fracture toughness of cordierite increases from 1.0 to 1.5 MPam' / 2. This is due to the difference in thermal expansion between the cordierite and the second phase of ZrSi4, which causes the cracks around the zircon grains to deflect, rather than due to the residual stress on the cordierite grains.

1 Introduction Constants and thermal shock resistant honeycomb structures are widely used in substrates for electronic devices and automatic exhaust contactors. However, due to its poor mechanical properties in the production process, the fracture toughness is reduced, thereby hindering its application.

In the past 20 years, toughened composites have been developed by exploiting the mechanism associated with dispersed particles to study the dispersibility of fracture energy. The particles of the second phase near the tip of the expandable crack interfere with the front and reduce the stress intensity. The dispersion toughness of oxide ceramics produced by adding a second phase of zirconium oxide is a feasible method for improving the mechanical properties of alumina, mullite and cordierite ceramics.

In past studies, it was found that it was added to cordierite

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