WO2023245791A1

WO2023245791A1 - β-SIC-BOUND SIC REFRACTORY MATERIAL HAVING LOW BINDING PHASE CONTENT, PREPARATION METHOD THEREFOR AND PRODUCT THEREOF

Info

Publication number: WO2023245791A1
Application number: PCT/CN2022/107064
Authority: WO
Inventors: 吕春江; 黄志刚; 李�杰; 张新华; 吴吉光; 王文武; 常赪; 王建栋
Original assignee: 中钢集团洛阳耐火材料研究院有限公司
Priority date: 2022-06-21
Filing date: 2022-07-21
Publication date: 2023-12-28
Also published as: CN114853489A; CN114853489B

Abstract

Provided are a β-SiC-bound SiC refractory material having low binding phase content, a preparation method therefor and a product thereof, which relate to the technical field of refractory materials. The β-SiC-bound SiC refractory material having low binding phase content comprises a binding phase and a main phase. The binding phase is β-SiC, with mass content being 3% to 7%. The main phase is o-SiC, with mass content being 92% to 95%. The β-SiC binding phase covers the surface of the main phase in a nanowire morphology. The liquid high-viscosity organic matter used is both a carbon source and a binder. The addition amount and the actual carbon ratio of the high-viscosity organic matter can be adjusted to ensure the moldability of mud and the ignition loss in the firing process, thereby guaranteeing the density of a finished product. In the provided β-SiC-bonded SiC refractory material, the binding phase content is low, and the purity of silicon carbide can be as high as 96% or above. The preparation method is simple. The firing process is carried out in a low-temperature, micro-pressure and oxygen-free atmosphere, and has no environmental pollution and low energy consumption.

Description

β-SiC bonded SiC refractory material with low binder phase content and preparation method and product thereof

This application claims priority to the Chinese patent application submitted to the China Patent Office on June 21, 2022, with the application number 2022107089913 and the invention title "β-SiC bonded SiC refractory materials with low binding phase content and preparation methods and products thereof" , the entire contents of which are incorporated herein by reference.

Technical field

The invention belongs to the technical field of refractory materials, and in particular relates to a β-SiC bonded SiC refractory material with low binding phase content and a preparation method and product thereof.

Background technique

There are reports in the international market of self-bonded silicon carbide refractory products of the same material, which are mainly used for high-temperature kiln linings such as ironmaking blast furnaces and waste incineration ash melting furnaces. Among them, self-bonded silicon carbide products for ironmaking blast furnaces have some applications in China. In the preparation process, in order to improve the molding performance of the mud, more micro-powder grade raw materials, shaped aggregate particles, and two molding methods of machine pressing and pouring are usually added. Most of them are reaction sintering in a carbon-buried atmosphere. The volume density of the products for ironmaking blast furnaces is Mostly in the range of 2.55-2.70g·cm ^-3 , the SiC content is greater than 80%; the FC content is not higher than 4%. The SiC content of some typical brand products is more than 90%, and the high temperature performance is good. Most of the existing self-bonded silicon carbide products imported from China on the market are carbon-buried fired products. The firing atmosphere at high temperatures is mainly CO and N ₂ , and a small amount of nitride (usually Si ₂ N ₂ O) is present in the products. Compared with the main binding phase β-SiC, Si ₂ N ₂ O grains are easy to grow to larger sizes, and the generation of Si ₂ N ₂ O consumes a certain amount of metallic silicon, especially for self-bonding silicon carbide materials with low binding phase content. The existence of Si ₂ N ₂ O side reactions may reduce the content and dispersion uniformity of the main binding phase in the material, which is not conducive to the improvement of the basic indicators of the material.

Moreover, the process of loading and unloading kilns for buried carbon production is cumbersome, unfriendly to the ecological environment, and easily generates dust, requiring strict environmental protection measures. In addition, product production or delivery cycles are long, which has restricted the promotion of its products in more industries for many years.

The information disclosed in this Background section is merely intended to enhance an understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art that is already known to a person of ordinary skill in the art.

Contents of the invention

The purpose of the present invention is to solve the technical problems in the existing self-bonded silicon carbide refractory material technology that the preparation process is complicated, unfriendly to the environment, and the prepared silicon carbide refractory material has low purity, and to provide a β-SiC bonded with low binding phase content. SiC refractory materials and preparation methods and products thereof.

Inventive concept of the present invention

Si and C need to be introduced into the green body to form a sintering reaction at high temperature. In the conventional way of introducing solid C, due to the low density of solid C raw materials, the incorporation will cause the overall density of the mud to be significantly reduced, which is not conducive to improving the basic performance indicators of refractory materials; and the full liquid organic carbon source does not need to add other conventional bonding agent to ensure lower loss on ignition without affecting the final refractory performance.

The optimal amount of liquid organic carbon source added is limited by the molding performance of the mud material. The mud material must be dry and wet to meet the molding requirements. As a result, the amount of carbon source introduced into the liquid organic carbon source is not easy to flexibly adjust. In order to provide a certain amount of carbon source to adapt to material preparation The requirements for synthesizing β-SiC binding phase require an adjustment mechanism to increase the amount of carbon source added. In general, adding less carbon source can generate less β-SiC binding phase. The smaller the grains of β-SiC binding phase formed by reaction sintering, which is conducive to the uniform dispersion of the binding phase in the material. In addition, it is necessary to ensure that the bone Keeping the distance between material particles as small as possible will also help reduce the number of β-SiC binding phases, improve the binding effect and ensure product performance.

By effectively reducing the ignition loss of the binder and scientifically cooperating with reasonable particle gradation, an adjustment mechanism for the amount of carbon source added is formed to provide higher density for subsequent refractory materials. The specific method is that the addition amount of (3-5) mm silicon carbide particles and (0-10) μm silicon carbide powder can be used to adjust the optimal addition amount of liquid carbon source binder during molding, so that it can ensure the normal mud material. Molding can also introduce a reasonable amount of carbon sources. For example, under the premise of maintaining close packing, when the addition amount of (3-5) mm silicon carbide particles is increased to 25% and the addition amount of (0-10) μm silicon carbide powder is 0%, the specific surface area of the particle group in the formula is smaller , less binder can cover the surface of all particles. At this time, the optimal amount of binder required for molding is reduced to 3.0% to 3.5%, and at the same time, the amount of effective carbon source added and the amount of binding phase generated are reduced; on the contrary, when When the addition amount of (3-5) mm silicon carbide particles is reduced to 0% and (0-10) μm silicon carbide powder is increased to 30%, the specific surface area of the particles in the formula is greatly increased, and the optimal binder required for molding is Increasing the amount to 5.0% to 5.5% can increase the amount of effective carbon source added and the amount of bonded phase generated; on this basis, organic binders or mixed binders with different carbon residual rates (30%-60%) can be selected. The agent can more flexibly enhance the adjustment of carbon source quantity, reduce product burning loss, and improve product density. Therefore, the β-SiC bonded SiC refractory product with a low binding phase content has a flexible adjustment mechanism for the number of binding phases. It is difficult for large bricks to be fully sintered, so a formula with a relatively low binding phase quantity can be used, and it is easy for small bricks to achieve full sintering. Fully sintering can use a formula with a relatively high binding phase content, and ensure that there is little difference in the performance of the product, and the product is easy to implement industrial production.

The above examples are used to make the solution easier to understand. Similarly, other solutions are also within the protection scope of this application.

In terms of the formation mechanism of β-SiC nanowires, the reaction between Si and C to generate β-SiC nanowires involves the gas phase to ensure the formation of more flocculent nanowires and a lower generation temperature, making it easier to achieve industrial production.

The formation of β-SiC nanowires requires the participation of the gas phase, usually with the participation of oxygen elements. On the one hand, the source of the oxygen element comes from the oxygen provided during high-temperature sintering of oxides such as ball clay, silica powder, and activated alumina powder added during preparation; on the other hand, it comes from the oxygen in the environment. The oxygen-free atmosphere is only ideal. There is still a small amount of oxygen in the actual reaction environment. Although the atmosphere sintering furnace has a certain degree of sealing, a small amount of air still enters. In addition, the high-purity protective gas prepared industrially cannot reach 100% purity. Therefore, the reaction between Si and C to form β-SiC nanowires involves gas phase participation, as follows:

Si(s)+[O]=SiO(g)

C(s)+[O]=CO(g)

Nanowire deposition reaction: SiO(g)+3CO(g)=β-SiC(Nanowire)+2CO ₂ (g)

β-SiC nanowire solid-gas generation mechanism: the growth end of the nanowire is always solid, and the growth is deposited at the solid tip of the nanowire;

The solid-liquid-gas generation mechanism of β-SiC nanowires: liquid droplets are maintained at the growth end of the nanowires, and the growth is deposited on the liquid tip of the nanowires.

The technical solutions disclosed by the present invention are as follows:

The first aspect of the present invention provides a β-SiC bonded SiC refractory material with low binder phase content, which is characterized by:

Including binding phase and main crystal phase;

Wherein, the binding phase is β-SiC, and the mass percentage is 3%-7%;

The main crystal phase is α-SiC, and the mass percentage is 92%-95%;

The binding phase covers the surface of the main crystal phase in the form of nanowires.

β-SiC combined with SiC refractory materials also include 0-2% SiO ₂ or Al ₂ O _3. This is because the raw materials contain a small amount of oxides, such as ball clay, silica powder, activated alumina powder, etc., which are fired at high temperatures. As for the products produced, a small amount of residue in this part will have limited impact on the performance of the product during use.

In some embodiments, the raw materials for preparing the main crystal phase include component A and component B:

The A component includes silicon carbide, silicon source and auxiliary raw materials, and the silicon carbide includes silicon carbide particles, silicon carbide fine powder and silicon carbide micron powder;

The B component includes carbon source and special additives.

In some embodiments, the mass percentages of each raw material in component A are: silicon carbide particles 60%-80%, silicon carbide fine powder and silicon carbide micropowder combined 10%-30%, silicon Source 2%-5%, auxiliary raw materials 0%-2%;

The content of carbon source in component B is 3%-6% of the total amount of raw materials in component A, and the content of special additives in component B is 0% of the total amount of raw materials in component A. -0.2%.

In some embodiments, the silicon carbide is black silicon carbide. Black silicon carbide has good toughness, and other types of α-SiC are also suitable;

And/or, the silicon carbide particles are particle-graded silicon carbide particles, and the particle size of the particles is 0-5 mm;

Preferably, the specifications of the particle-graded silicon carbide particles are: the mass percentage of particles with a particle size of 0-0.5mm is 5%-20%, and the mass percentage of particles with a particle size of 0.5mm-1.5mm is It is 20%-40%, the mass percentage of the particle size is 1.5mm-3mm is 10%-20%, and the mass percentage of the particle size is 3mm-5mm is 0%-25%;

Further preferably, the purity of the silicon carbide particles is above 98%;

And/or, the particle size of silicon carbide fine powder is 180 mesh-320 mesh, and the purity is more than 97%;

And/or, the particle size of the silicon carbide powder is D50 (0-10) μm, and the purity is above 95%.

By adjusting the silicon carbide particle gradation, the content of silicon carbide fine powder, and silicon carbide micro powder, and selecting organic binders with different carbon contents, the prepared β-SiC combined with SiC can not only have a higher density, but also be able to Guarantee a lower content of β-SiC binding phase.

In some embodiments, preferably, the silicon source is metallic silicon powder; further preferably, the purity of the metallic silicon powder is above 98%;

Preferably, the carbon source only includes liquid high-viscosity organic matter and does not include solid carbon sources; further preferably, the residual carbon rate of the liquid high-viscosity organic matter is more than 30%. The solid carbon source will cause the overall molding density of the mud material to be significantly reduced. Using liquid high-viscosity organic matter as the carbon source can, on the one hand, be used as a binder to shape the solid raw material, and on the other hand, it can control the loss on ignition to ensure that β-SiC combines with SiC. The higher the density and carbon residue rate, the higher the viscosity of the liquid high-viscosity organic matter. The mixture should be prepared according to the actual state of the solid raw materials. Adjust the optimal amount of liquid carbon source binder during molding to ensure normal molding of the mud and introduce a reasonable amount of carbon source. In addition, even if liquid high-viscosity organic matter is used in a high-temperature protective atmosphere, there will be residual solid carbon, and the residual solid carbon content is extremely low, generally less than 2%. The minimum viscosity standard of liquid high-viscosity organic matter is that it can be used as a temporary binder, and the strength of the pressed bricks can meet the requirements for transportation, kiln installation, etc. Generally, the higher the residual carbon rate, the greater the viscosity. Generally, an organic binder with a higher residual carbon rate is used as the carbon source.

In some embodiments, the auxiliary raw material is selected from one or more of spherical clay, silica micro powder, and activated alumina micro powder. The particle size range of the auxiliary raw material is D50≤10 μm. The addition of the auxiliary raw material enhances the clay When firing at high temperatures, the auxiliary raw materials can provide a very small amount of oxygen to help generate the binding phase, improve the sintering effect, and enable the reaction sintering to form a uniformly dispersed binding phase;

And/or, the special additive is selected from one or more of MoSi ₂ , ferrosilicon alloy, and silicon-manganese alloy. The particle size range of the special additive is 240 mesh-320 mesh. The special additive is used as a sintering aid to reduce Si and C reaction sintering temperature.

A second aspect of the present invention provides a method for preparing β-SiC combined with SiC refractory materials with low binding phase content, which is characterized in that the steps of the preparation method include:

Drying: dry the formed wet blank in sections;

Firing: The dried bricks are fired in sections under low temperature and micro-pressure in a non-oxygen atmosphere.

In some embodiments, the density of the wet blank is 2.70-2.90 g·cm ^-3 , and the maximum drying temperature is 110°C-130°C. Controlling reasonable drying temperature and drying time not only ensures that the green body is strong enough to meet production needs such as transportation and kiln installation without producing waste products, but also reasonably controls energy consumption to avoid high temperatures, high energy consumption, and prolonged drying cycles. Production cycle and cost.

And/or, the maximum firing temperature does not exceed 1350°C. When the firing temperature exceeds 1350°C, the volume density and strength of the fired material decrease slightly. On the one hand, the size of the refractory material does not change during firing, and higher temperatures cause further loss of refractory material quality; on the other hand, higher burning The final size of β-SiC nanowires increases with the temperature, which is not conducive to the uniform dispersion of the binding phase in the refractory material.

In some embodiments, the specific steps of staged drying include: putting the formed wet blank into a drying kiln, and after insulating it at 60°C, 70°C, 80°C, 90°C, and 100°C for 4-8 hours respectively, The temperature rise rate is 20°C/h to the maximum temperature of 110-130°C, and the temperature is maintained for more than 12 hours to obtain a dry billet; segmented drying reduces the drying speed, prolongs the heat conduction process, reduces the temperature difference in different parts of the dry refractory material, and reduces the temperature difference in different parts of the dried product. The difference in volatilization speed causes asynchronous shrinkage and stress, which avoids the occurrence of drying defects in the product. The benefits of segmented drying are more obvious for large-size refractory materials.

And/or, the specific step of step-by-step sintering includes: heating the dry blank to 1200°C-1250°C at a heating rate of 20°C-40°C/h, and maintaining the temperature for 5-10h; and then heating it at 10°C-30°C /h heating rate to 1300℃-1350℃, continue to keep warm for 10-20h. Through segmented firing, the temperature difference between the inside and outside of the refractory material is reduced, and the combined phase crystal seeds in different parts of the refractory material are promoted to be evenly produced and grow synchronously. In particular, the core of the refractory material can fully undergo the sintering reaction, and the combined phase crystal morphology is generally uniform. Ensure material uniformity.

A third aspect of the present invention provides a refractory product, which is characterized in that it includes the above-mentioned β-SiC combined with SiC refractory material or the β-SiC combined with SiC refractory material produced by the above-mentioned preparation method.

Compared with the existing technology, the technical effects achieved by the present invention are as follows:

(1) The β-SiC bonded SiC refractory material disclosed in the present invention has low binding phase content, high silicon carbide purity, and the silicon carbide purity can reach more than 96%. The preparation method is simple, and the firing process is under low temperature, micro-pressure, and oxygen-free atmosphere. It is carried out without environmental pollution, and the energy consumption for firing is low, which reduces the preparation cost.

(2) Due to the low density of the solid carbon source in the prior art, the incorporation of the solid carbon source will cause the overall molding density of the mud to be significantly reduced, which is not conducive to improving the basic performance indicators of the finished product. The carbon source of the present invention uses liquid high-viscosity organic matter, which is not selected Solid carbon source overcomes the above shortcomings from the source. In addition, liquid high-viscosity organic matter is both a carbon source and a binder. When other raw materials remain unchanged, the formability and firing of the mud can be ensured simply by adjusting the amount of liquid high-viscosity organic matter and the residual carbon rate. Loss on ignition during the process, thereby ensuring the density of the finished product.

(3) The present invention has a multi-level configuration of raw material particle sizes, adjusts the ratio of different particle levels, and flexibly adjusts the amount of binder in combination with the carbon content of the binder, so that it can not only ensure the normal formation of the mud material, but also Introduce a reasonable amount of carbon source to achieve the goals of low loss on ignition, high density and high bonding strength.

(4) The present invention adds a small amount of auxiliary raw materials and special additives, which enhances the molding performance of the mud, increases the gas phase reaction, reduces the solid-solid reaction process, lowers the firing temperature, and helps to form uniformly dispersed β -SiC nanowire binding phase.

(5) The overall amount of carbon source added in the present invention is small, and the amount of β-SiC binding phase that can be generated is limited. The grains of the β-SiC binding phase formed by reaction sintering are small, which is beneficial to the uniform dispersion of the binding phase in the material. Improvement of finished product performance.

Description of the drawings

Figure 1 is the fracture micromorphology of the β-SiC bonded SiC refractory material with low binder phase content prepared in Example 1;

Figure 2 is the microscopic morphology of the β-SiC nanowire binding phase in the β-SiC bonded SiC refractory material with low binding phase content prepared in Example 1; in the figure: 1β-SiC binding phase; 2α-SiC main crystal phase.

Detailed ways

The technical solutions of the present invention will be described below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the mention of one or more steps in the present invention does not exclude the existence of other methods and steps before and after the combination step, or that other methods and steps can be inserted between these explicitly mentioned steps. It should also be understood that these examples are merely illustrative of the invention and are not intended to limit the scope of the invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and does not limit the order of each method or limit the implementation scope of the present invention. Changes or adjustments in their relative relationships will not change the technical content without substantial changes. Under the conditions, it can also be regarded as the implementable scope of the present invention.

There are no specific restrictions on the sources of the raw materials and instruments used in the examples. They can be purchased in the market or prepared according to conventional methods well known to those skilled in the art.

Example 1

Raw materials and formula used: more than 98% silicon carbide particles, 5-3mm accounts for 5%, 3-1.5mm accounts for 20%, 1.5-0.5mm accounts for 35%, 0.5-0mm accounts for 15%; more than 97% carbonization Silicon fine powder - 320 mesh accounts for 12%, more than 95% silicon carbide micro powder D50 = 8.0 μm accounts for 7.5%; 98% metal silicon powder - 320 mesh addition amount is 3.5%, the weight ratio of ball clay and silica micro powder is 1: 2. Add 2.0%; particle size -320 mesh MoSi ₂ plus 0.1%. When preparing the mud, the above raw materials are fully mixed with a phenolic resin with a carbon residue rate of 40%, and an additional 4.0% of the phenolic resin is added. It is molded into a 600×400×100mm blank, with a molding density of 2.84g·cm ^-3 , a drying temperature of 130°C, and a drying time of 12h. The furnace is fired in an electric heating atmosphere, and argon gas is passed through to remove the air in the furnace in advance. During the firing process, a slight positive pressure of 120 mm of water column is maintained in the furnace, and the maximum temperature is 1320°C, and the temperature is maintained for 14 hours. After cooling, a β-SiC combined with SiC shaped refractory material with low binding phase content is produced. The finished product has a volume density of 2.77g·cm ^-3 after burning, a β-SiC binding phase content of 4-5%, a silicon carbide purity of 96.79%, and a resistance to The folding strength is 58.7MPa.

Figure 1 shows the microscopic morphology of the fracture surface of the β-SiC bonded SiC refractory material with low binding phase content. It can be seen that the β-SiC binding phase 1 covers the surface of the aggregate particles of the α-SiC main crystal phase 2.

As can be seen from Figure 2, β-SiC has a nanowire structure with a diameter of only 50-200mm.

A comparison of various performance indicators between the prepared β-SiC bonded SiC refractory materials with low binder content and imported materials is shown in Table 1.

Table 1 Inspection results of typical sample bricks of finished materials obtained in Example 1 and imported materials

As can be seen from the above table, the β-SiC combined with SiC refractory material with low binding phase content prepared in this example has fewer impurities and higher purity, and the excellent performance of the SiC main crystal phase is more clearly reflected. There are differences in properties from imported self-bonding silicon carbide materials: 1) products with higher purity and high volume density can be prepared; 2) products can achieve higher thermal conductivity; 3) low F.C and N content.

Example 2

Raw materials and formula used: more than 98% silicon carbide particles, 5-3mm accounts for 25%, 3-1.5mm accounts for 12%, 1.5-0.5mm accounts for 25%, 0.5-0mm accounts for 8%; more than 97% carbonization Silicon fine powder - 240 mesh accounts for 24%, more than 95% silicon carbide powder D50 = 3.0 μm accounts for 2%; 98% metal silicon powder - 320 mesh adding amount is 2.1%, silica micro powder adding 1.9%; -320 mesh MoSi ₂ and ferrosilicon 1:1 plus 0.2%. When preparing mud, the above raw materials are fully mixed with phenolic resin with a carbon residue rate of 55%, and an additional 3.4% of phenolic resin is added. The blank was molded into a 695×470×165mm blank with a molding density of 2.85g·cm ^-3 , a drying temperature of 120°C, and a drying time of 15h. The furnace is fired in an electric heating atmosphere, and argon gas is passed through to remove the air in the furnace in advance. During the firing process, a slight positive pressure of 100 mm of water column is maintained in the furnace, and the maximum temperature is 1300°C, and the temperature is maintained for 12 hours. The volume density of the product after burning is 2.80g·cm ^-3 , the content of β-SiC binding phase is 2-3%, the purity of silicon carbide is 96.95%, the flexural strength is 60.2MPa, and FC≤1.0%.

Example 3

The raw materials and formula used are more than 98% silicon carbide particles, 5-3mm accounts for 15%, 3-1.5mm accounts for 10%, 1.5-0.5mm accounts for 25%, 0.5-0mm accounts for 15%; more than 97% is carbonized Silica fine powder - 240 mesh accounts for 17%, more than 95% silicon carbide powder D50 = 5.0 μm accounts for 12%; 98% metal silicon powder - 320 mesh addition amount is 4.8%, ball clay and activated alumina powder are added at 2:1 1.2%; -320 mesh silicon manganese and ferrosilicon alloy 2:1 plus 0.15%. When preparing mud, the above raw materials are fully mixed with phenolic resin with a carbon residue rate of 50%, and 4.2% of phenolic resin is added. It is molded into a 400×350×70mm blank, with a molding density of 2.80g·cm ^-3 , a drying temperature of 130°C, and a drying time of 12 hours. The furnace is fired in an electric heating atmosphere, and argon gas is passed through to remove the air in the furnace in advance. During the firing process, a slight positive pressure of 150 mm of water column is maintained in the furnace, and the maximum temperature is 1350°C, and the temperature is maintained for 10 hours. The volume density of the product after burning is 2.72g·cm ^-3 , the content of β-SiC binding phase is 5-7%, the purity of silicon carbide is 97.57%, and the flexural strength is 50.3MPa.

Example 4

The raw materials and formula used are more than 98% silicon carbide particles, 5-3mm accounts for 0%, 3-1.5mm accounts for 25%, 1.5-0.5mm accounts for 40%, 0.5-0mm accounts for 15%; more than 97% is carbonized Silica fine powder - 240 mesh accounts for 2%, more than 95% silicon carbide powder D50 = 1.0 μm accounts for 12%; 98% metal silicon powder - 320 mesh addition amount is 4.2%, ball clay and activated alumina powder are added at 2:1 1.8%; -320 mesh silicon manganese alloy and ferrosilicon alloy 2:1 plus 0.15%. When preparing mud, the above raw materials are fully mixed with phenolic resin with a carbon residue rate of 40%, and an additional 4.6% of phenolic resin is added. It is molded into a 400×350×70mm blank, with a molding density of 2.74g·cm ^-3 , a drying temperature of 130°C, and a drying time of 14h. The furnace is fired in an electric heating atmosphere, and argon gas is passed through to remove the air in the furnace in advance. During the firing process, there is a slight positive pressure in the furnace, with a pressure of 50mm water column, firing at a maximum of 1330°C, and heat preservation for 10 hours. The volume density of the product after burning is 2.66g·cm ^-3 , the content of β-SiC binding phase is 4-6%, the purity of silicon carbide is 96.89%, and the flexural strength is 47.8MPa.

Example 5

Raw materials and formula, more than 98% silicon carbide particles, 5-3mm accounts for 25%, 3-1.5mm accounts for 10%, 1.5-0.5mm accounts for 25%, 0.5-0mm accounts for 10%; more than 97% silicon carbide Fine powder - 240 mesh accounts for 25%; 98% metallic silicon powder - 320 mesh addition amount is 3.5%, ball clay is added 1.5%; - 320 mesh ferrosilicon alloy is added 0.1%. When preparing mud, the above raw materials, phenolic resin with 50% carbon residue and asphalt are preheated and mixed thoroughly at a ratio of 5:1, and 3.6% is added. The blank is molded into a 500×390×80mm blank with a molding density of 2.72g·cm ^-3 , a drying temperature of 130°C, and a drying time of 15h. The furnace is fired in an electric heating atmosphere, and argon gas is passed through to remove the air in the furnace in advance. During the firing process, a slight positive pressure of 50 mm of water column is maintained in the furnace, and the maximum temperature is 1350°C, and the temperature is maintained for 20 hours. The volume density of the product after burning is 2.66g·cm ^-3 , the content of β-SiC binding phase is 4-5%, the purity of silicon carbide is 96.65%, and the flexural strength is 48.1MPa.

Example 6

A refractory product, including the β-SiC combined with SiC refractory material with low binder phase content prepared in Example 1, is used as the lining material of a high-temperature kiln. After the product is prepared according to the designed shape, it is built with matching fire mud at high temperatures. The interior of the kiln is used as a protective lining. During the service process, it is usually subjected to various complex high-temperature working conditions such as high-temperature thermal stress changes, erosion of various slag components, high-temperature gas erosion or oxidation, erosion and wear.

Some working environments not only require the use of high temperature resistance and corrosion resistance of materials, but also the thermal conductivity of materials for heat exchange, such as cooling stave bricks in blast furnaces and tuyere composite bricks with cooling systems.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and illustration. These descriptions are not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical applications, thereby enabling others skilled in the art to make and utilize various exemplary embodiments of the invention and various different applications. Choice and change. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

A β-SiC bonded SiC refractory material with low binder phase content, characterized by:

Including binding phase and main crystal phase;

Wherein, the binding phase is β-SiC, and the mass percentage is 3%-7%;

The main crystal phase is α-SiC, and the mass percentage is 92%-95%;

The binding phase covers the surface of the main crystal phase in the form of nanowires.
The β-SiC bonded SiC refractory material according to claim 1, characterized in that the raw materials for preparing the main crystal phase include component A and component B:

The A component includes silicon carbide, silicon source and auxiliary raw materials, and the silicon carbide includes silicon carbide particles, silicon carbide fine powder and silicon carbide micron powder;

The B component includes carbon source and special additives.
The β-SiC bonded SiC refractory material according to claim 2, characterized in that the mass percentage of each raw material in the A component is: 60%-80% of silicon carbide particles, silicon carbide fine powder and carbonized The combined amount of silicon micropowder is 10%-30%, silicon source is 2%-5%, and auxiliary raw materials are 0%-2%;

The content of carbon source in component B is 3%-6% of the total amount of raw materials in component A, and the content of special additives in component B is 0% of the total amount of raw materials in component A. -0.2%.
The β-SiC combined SiC refractory material according to claim 2, wherein the silicon carbide is black silicon carbide;

And/or, the silicon carbide particles are particle-graded silicon carbide particles, and the particle size of the particles is 0-5 mm;

Preferably, the specifications of the particle-graded silicon carbide particles are: the mass percentage of particles with a particle size of 0-0.5mm is 5%-20%, and the mass percentage of particles with a particle size of 0.5mm-1.5mm is is 20%-40%, the mass percentage of the particle size is 1.5mm-3mm is 10%-20%, and the mass percentage of the particle size is 3mm-5mm is 0%-25%; further preferably, The purity of the silicon carbide particles is more than 98%;

And/or, the particle size of silicon carbide fine powder is 180 mesh-320 mesh, and preferably, the purity is above 97%;

And/or, the particle size of the silicon carbide powder is D50 (0-10) μm, and preferably, the purity is above 95%.
The β-SiC combined SiC refractory material according to claim 2, characterized in that the silicon source is metallic silicon powder; preferably, the purity of the metallic silicon powder is above 98%;

The carbon source only includes liquid high-viscosity organic matter and does not include solid carbon sources; preferably, the residual carbon rate of the liquid high-viscosity organic matter is more than 30%.
The β-SiC bonded SiC refractory material according to claim 2, characterized in that the auxiliary raw material is selected from one or more of spherical clay, silica powder, and activated alumina powder; preferably, the auxiliary material The particle size range of raw materials is D50≤10μm;

And/or, the special additive is selected from one or more of MoSi 2 , ferrosilicon alloy, and silicon-manganese alloy; preferably, the particle size range of the special additive is 240 mesh to 320 mesh.
A method for preparing β-SiC combined with SiC refractory materials with low binding phase content as claimed in claim 1, characterized in that the steps of the preparation method include:

Drying: dry the formed wet blank in sections;

Firing: The dried bricks are fired in sections under low temperature and micro-pressure in a non-oxygen atmosphere.
The preparation method according to claim 7, characterized in that the density of the wet blank is 2.70-2.90g·cm -3 , and the maximum drying temperature is 110°C-130°C;

And/or, the maximum firing temperature does not exceed 1350°C.
The preparation method according to claim 7, characterized in that:

The specific steps of step-by-step drying include: putting the formed wet blank into a drying kiln, and after insulating it at 60°C, 70°C, 80°C, 90°C, and 100°C for 4-8 hours, dry it at a temperature of 10-20°C/h. The heating rate is increased to the maximum temperature of 110-130°C, and the temperature is maintained for more than 12 hours to obtain a dry billet;

And/or, the specific step of step-by-step sintering includes: heating the dry blank to 1200°C-1250°C at a heating rate of 20°C-40°C/h, and maintaining the temperature for 5-10h; and then heating it at 10°C-30°C /h heating rate to 1300℃-1350℃, continue to keep warm for 10-20h.
A refractory product, characterized in that it includes the β-SiC combined SiC refractory material described in any one of claims 1 to 6 or the β-SiC combined SiC refractory material made by the preparation method in any one of claims 7 to 9.