News Archives - Global Refractory Brick Supplier & Factory-Rongsheng

Why is it Necessary to Bake the Furnace After the Construction of Refractory Lining Materials?

2025-09-08 by globalrefractory

Furnace lining materials (such as refractory bricks and refractory castables) absorb significant amounts of moisture during construction. If heated directly without drying, this moisture rapidly evaporates, causing cracks, bulging, and even explosions in the lining. Furnace drying gradually evaporates this moisture by slowly heating it, protecting the refractory materials.

How is Water Removed During the Furnace Drying Process?

After refractory construction is completed, three main types of water exist in the system: free water, physically bound water, and chemically bound water.

During furnace drying, a large amount of free and bound water must be removed. This water evaporates significantly between 80°C and 150°C, after which the drainage rate slows. As the temperature continues to rise, around 300°C, the free and bound water are essentially completely removed. At 500°C to 600°C, the refractory material completes its crystal transformation. At around 1100°C, the sintered strength required for design is reached, and stress is completely released. To fully remove deep-seated free and bound water and complete crystal transformation, constant temperatures must be maintained for a period of time at different temperature ranges.

During furnace drying, the 80°C to 300°C stage is a critical phase. This is primarily because water transforms into water vapor at 110°C. During this phase, the amount of water removed is large and the rate of water removal is rapid. The rate of water removal significantly affects the refractory material. If moisture is removed too quickly, the remaining internal moisture will not diffuse as quickly as the surface evaporation rate. The internal moisture will also heat up and convert to vapor, causing expansion. This can cause cracking in the material, reduce bond strength, and weaken the material. Therefore, the insulation period should be appropriately extended. The ideal drying period is a constant drying rate, where the amount of moisture evaporating from the surface matches the amount of moisture removed from the interior.

When heating from 80°C to 600°C, the temperature should be increased slowly. Too rapid a temperature increase will cause the refractory surface to dry quickly, preventing the large amount of vaporized moisture from evaporating. This will generate destructive vapor pressure and cause cracks or fissures in the refractory. At 300°C, bound water and crystallization water convert to gas and are released through pores. Therefore, sufficient drying time is required to completely remove the crystallization water.

Typical Furnace Curve

The above describes the general principles of furnace curing. Because different refractory materials have different compositions and thicknesses, the furnace curing curve must be determined by the design company in conjunction with the refractory manufacturer. The figure below shows a typical furnace curing curve found online.

First, slowly increase the temperature (20-30°C/hour) to 140°C and hold it at this temperature for 20 hours.
Then, slowly increase the temperature (20-30°C/hour) to 350°C and hold it at this temperature for 10 hours.
Then, slowly increase the temperature (20-30°C/hour) to 420°C and hold it at this temperature for 10 hours.
Finally, slowly cool the temperature back to ambient temperature.

Furnace Drying in Waste-to-Energy Plants

Furnace drying is part of the furnace construction process. Generally, furnace construction is divided into three phases: construction and cold-state inspection, low- to medium-temperature drying, and high-temperature drying.

Construction and cold-state inspection, in simple terms, involve the construction of the furnace walls and refractory components. High-temperature drying refers to the drying of the furnace lining, which is performed simultaneously with the corrosion-resistant passivation treatment of the boiler’s steam-water system. This improves efficiency, saves fuel, and enhances economic efficiency.

The purpose of low- to medium-temperature drying is to remove moisture that cannot naturally separate from the castings, allowing them to further solidify and ensure the performance and quality of the furnace lining. This process virtually completely removes free water and most crystallized water, bringing the moisture content to less than 2.5%, a satisfactory standard.

Of course, a more important aspect of furnace drying is the inspection of the furnace walls after the relatively mild fire. Deformation, cracks, and collapse should be avoided to ensure they meet the performance requirements of the furnace under normal operating conditions.

The basic requirements for furnace drying are that the furnace is complete and has been naturally dried for seven days. While the temperature of a medium-low temperature furnace drying is not particularly high, it is still considered the first ignition. As a thermal equipment, the boiler must undergo its initial thermal testing. Therefore, requirements such as boiler insulation, drum water level, exhaust and drain piping, water and steam pipe hangers, sealed flue gas and air duct openings, pressurized water pressure control, lighting, fire protection, and safety precautions must be in place.

Next comes the preparation of furnace drying equipment and materials.

Before the advent of high-temperature flue gas furnace drying, the furnace drying process was typically accomplished using a combination of wood and fuel oil. Firewood was ignited at a defined location, and after the temperature reached a certain level, a starter oil burner was ignited to raise and maintain the required furnace temperature. Limited by the burning point of the firewood, the labor intensity involved, the high flame temperature of the starter oil burner, and the concentrated heat load, a slow and uniform furnace heating process was impossible. Structural constraints inevitably created “dead spots” within the boiler that were not accessible for drying, making furnace drying quality difficult to ensure.

Currently, most furnaces use light diesel fuel and utilize a furnace drying machine to generate hot flue gas outside the furnace. This hot flue gas serves as the heat source, and after entering the furnace, the furnace walls primarily absorb heat through convection. This prevents high-temperature radiation from the flame from damaging the furnace walls, ensuring uniform heat absorption.

This allows for a slow heating process for the lining material, adhering to the principle of slow and uniform moisture release from refractory and wear-resistant lining materials. Controlling the drying temperature and temperature rise rate promotes the smooth release of different forms of moisture. Ensure temperature control, avoid dead spots, and ensure even heating of the furnace walls.

During the furnace drying process, ensure that all furnace temperature monitoring data is recorded and archived. Ensure moisture drain holes are properly opened and sealed after the boiler is started. At all times, ensure that heating surface tubes are protected from overheating and overburning. Always inspect the smoke exhaust.

Raw Material Composition of Refractory Materials

2025-08-24 by globalrefractory

The chemical composition of refractory materials is one of the most basic characteristics of refractory materials. Generally, the chemical composition of refractory materials is divided into two parts according to the content of the components and their functions:

(1) The basic components that account for the absolute majority and play a decisive role in their performance – the main components.
(2) The subordinate components that account for a small amount – the secondary components. The secondary components are impurities accompanying the raw materials or additives (additives) specially added during the production process to achieve a certain purpose.

Main Component

The main component is the component that constitutes the refractory matrix in the refractory material and is the basis of the characteristics of the refractory material. Its nature and quantity play a decisive role in the properties of the material. The main component can be an oxide or a non-oxide. Therefore, the refractory material can be composed of refractory oxides, or a refractory oxide and carbon or other non-oxides, or it can be composed entirely of refractory non-oxides. Oxide refractory materials can be divided into three categories according to the chemical properties of their main component oxides: acidic, neutral and alkaline.

(1) Acidic refractory materials. This type of material contains a considerable amount of free SiO₂. The most acidic refractory material is siliceous refractory material, which is composed of almost 94% to 97% free SiO₂. Clayey refractory materials have a relatively low content of free SiO₂ and are weakly acidic. Semi-siliceous refractory materials are in between.
(2) Neutral refractory materials. High-alumina refractories (with a mass fraction of Al2O3 above 45%) are acidic and tend to be neutral, while chromium refractories are alkaline and tend to be neutral.
(3) Alkaline refractories contain a considerable amount of MgO and CaO. Magnesia and dolomite refractories are strongly alkaline, while chromium-magnesium and forsterite refractories and spinel refractories are weakly alkaline.

This classification is of great significance for understanding the chemical properties of refractories and judging the chemical reactions between refractories and between refractories and contact materials during use.

Impurities

The raw materials for refractory materials are mostly natural minerals, so they often contain a certain amount of impurities. These impurities can reduce certain properties of the refractory. For example, the main component of magnesia refractories is MgO, while other oxides such as silicon oxide and iron oxide are impurities. The higher the impurity content, the greater the amount of liquid phase formed at high temperatures.

Impurities in refractory materials directly affect the material’s high-temperature properties, such as refractoriness, load deflection temperature, corrosion resistance, and high-temperature strength. On the other hand, impurities can lower the firing temperature of the product, promoting sintering.

At high temperatures, andalusite transforms into mullite and a free SiO2 glass phase. In the Al2O3-SiO2 system, mullite is chemically stable, so refractories containing andalusite are also chemically stable.

Additives

In the production or use of refractory materials, especially amorphous refractory materials, a small amount of additives is added to improve the physical properties, molding or construction performance (operation performance) and use performance of refractory materials. The amount of additives added varies with their properties and functions, ranging from a few ten-thousandths to a few percent of the total amount of refractory materials.

Additives are divided into the following categories according to their purpose and function:

(1) Changing rheological properties: including water reducers (dispersants), plasticizers, gelling agents, degumming agents, etc.
(2) Adjusting the setting and hardening speed: including accelerators, retarders, etc.
(3) Adjusting the internal structure: including foaming agents (air entraining agents), defoamers, shrinkage inhibitors, expansion agents, etc.
(4) Maintaining the construction performance of materials: including inhibitors (anti-swelling agents), preservatives, antifreeze agents, etc.
(5) Improving the use performance: including sintering aids, mineralizers, quick-drying agents, stabilizers, etc.

These added components, except those that can be burned off, remain in the material’s chemical composition.

Chemical composition analysis allows the purity and properties of a product or raw material to be determined based on the types and quantities of the components present. Phase diagrams can also be used to roughly estimate the product’s mineralogical composition and other relevant properties.

Application of High-Strength, Pressure and Erosion-Resistant Carbon Bricks in Large-Scale Submerged Arc Furnaces

2025-08-09 by globalrefractory

The lifespan of a submerged arc furnace lining is affected by a variety of factors, including the quality of the refractory materials, the level of masonry, the furnace drying process, and smelting operations. Some linings can last over 10 years, while others can last only a few months. This wide range in lining lifespan is primarily a significant test of the quality of the refractory materials. Carbon materials are the primary lining material for submerged arc furnaces. carbon blocks, carbon bricks uses. Among them, electric furnace carbon bricks, a special refractory material used to build the bottom and hearth of the submerged arc furnace, have a quality that directly determines the lifespan of the submerged arc furnace lining.

Carbon Bricks - Rongsheng Refractory Bricks — Carbon Bricks

Carbon Bricks for Submerged Arc Furnaces

With the rapid development of high-energy-consuming industries, submerged arc furnaces are becoming increasingly larger, placing increasing demands on the lifespan of furnace linings and furnace bottom safety. Simultaneously, incidents of molten iron penetrating the bottom are becoming more and more frequent, placing higher demands on upgrading furnace lining materials and improving their quality. Carbon bricks must operate at temperatures exceeding 2,000°C and are subject to long-term erosion, penetration, and corrosion from molten iron and furnace charge. When carbon bricks are damaged to a certain extent, preventing the furnace from operating normally, the furnace must be shut down and rebuilt. The service life of carbon bricks is the most important factor affecting the lifespan of an electric furnace. Therefore, improving the oxidation resistance, erosion resistance, and penetration resistance of carbon bricks in electric furnaces is particularly important.

Use of the First Generation of Carbon Bricks

In response to the special requirements of submerged arc furnaces for carbon bricks, and drawing on years of practical production experience, we have developed the first generation of carbon bricks – new high-density, low-porosity electric furnace carbon bricks. These high-density, low-porosity carbon bricks are made from raw materials with high thermal conductivity, low porosity, high bulk density, and strong antioxidant properties. The use of ultrafine powder (98% particle size below 0.045 mm) improves paste forming conditions and fills the micropores between large particles. Additives can reduce the micropores in the carbon bricks. By reselecting and adjusting raw materials, particle size, and mix ratios, and optimizing processes and equipment, we have finally produced electric furnace carbon bricks with a porosity of less than 15% and a compressive strength exceeding 40 MPa, meeting the production needs of submerged arc furnaces. These carbon bricks offer low porosity, high density, high compressive strength, and significantly enhanced resistance to oxidation, erosion, and penetration. The safety, reliability and service life of the furnace bottom of the electric arc furnace have been improved, and the average furnace life has been increased from less than 2 years to 4-5 years.

Microporous Carbon Brick from Rongsheng Factory

The Use of Second-Generation Carbon Bricks

As the industry continues to develop, first-generation carbon bricks, while maintaining a certain market share and influence, will face further upgrades to meet evolving market demands. Large-section carbon blocks have long been widely used in developed countries. However, due to limitations in equipment and process technology, most production is limited to small-section carbon bricks (400 mm × 400 mm), which cannot meet the demand for large-section carbon bricks in large-scale submerged arc furnaces. To meet the continuous development of the industry, through repeated exploration and experimentation, accumulated data, and summarized experience, the size of carbon blocks has been gradually increased from 400 mm × 500 mm, 400 mm × 600 mm, 400 mm × 800 mm, 600 mm × 800 mm, and 800 mm × 800 mm, ultimately achieving mass production of large-size carbon blocks of 800 mm × 800 mm × 4000 mm. The development of large-section carbon blocks involves more than simply increasing the size of existing blocks. Instead, it involves a comprehensive transformation and coordination of process technology, raw material preparation, molding equipment, roasting technology, and machining. While increasing the cross-section of the carbon blocks, the original physical and chemical properties are maintained.

The larger cross-section of these carbon blocks reduces gaps in the furnace floor masonry, thereby reducing the risk of molten iron burning through the furnace floor due to gaps. The larger cross-section also increases the weight of the individual carbon blocks, preventing them from drifting. The successful development and widespread use of the 800 mm × 800 mm large-section carbon blocks provide a strong guarantee for extending the life of large-scale submerged arc furnace linings.

Use of Third-Generation Carbon Bricks

Changes in Demand for Carbon Bricks for Submerged Arc Furnaces. Currently, newly built submerged arc furnaces both domestically and internationally are trending toward larger, more enclosed structures, higher power, and greater automation. Large-scale electric furnaces offer high thermal efficiency, high product quality, low unit investment, stable operation, and environmentally friendly performance. As submerged arc furnaces become larger, the corresponding furnace chamber size is also increasing. This places higher demands on the performance of the materials used to build the furnace.

First, the size of the carbon bricks used to build the furnace bottom is increasing, with the largest size reaching 800 mm × 800 mm × 3,700 mm.

As the cross-section and size of the carbon bricks continue to increase, the weight of each brick is also increasing. During the construction of large submerged arc furnaces, gaps can be reduced to prevent brick drift. This improves the utilization rate of fired blanks and reduces waste for manufacturers.

For a furnace with a diameter of 10 m, based on the design drawings for three sizes of carbon bricks: 400 mm × 400 mm × 1200 mm, 400 mm × 820 mm × 1200 mm, and 800 mm × 800 mm × 3700 mm, one layer of 800 mm × 800 mm × 3700 mm bricks is equivalent to two layers of the other two sizes. Based on the total length of gaps between 400 mm × 400 mm × 1200 mm bricks, replacing them with 400 mm × 820 mm × 1200 mm bricks can reduce the gap by 30.8%. Replacing them with 800 mm × 800 mm × 3700 mm bricks can reduce the gap by 72.1%. Taking the total length of gaps in a 400 mm × 820 mm × 1,200 mm carbon brick as a benchmark, replacing it with 800 mm × 800 mm × 3,700 mm carbon bricks can reduce the gap size by 59.7%.

At the same time, with the increasing size of submerged arc furnaces, the diameter and depth of the furnace chamber have increased. As the charge volume increases, the amount of molten iron loaded in the furnace increases, leading to higher production, which in turn increases the pressure on the carbon bricks at the furnace bottom. Due to the increased charge volume, larger electrode size, and higher furnace temperatures in large submerged arc furnaces, the eddy currents of the molten liquid during the smelting process intensify, increasing the impact on the carbon bricks.

As a manufacturer of submerged arc furnace lining materials, we are committed to upgrading our products to better meet customer needs in response to the challenges faced by downstream enterprises in their upgrades and development. For high-quality submerged arc furnace carbon bricks and blocks, please contact Rongsheng. Get free carbon brick pricing!

Application of Silicon Nitride Bonded Silicon Carbide Bricks in the Ceramic Industry

2025-07-25 by globalrefractory

Silicon nitride combined with silicon carbide bricks not only have the characteristics of high density, high strength, good thermal shock stability, high load softening point, good thermal conductivity, high resistance value, etc., but also have excellent resistance to melting erosion and oxidation resistance of cryolite, aluminum fluoride, sodium fluoride and calcium fluoride. It is mainly used in building sanitary ceramics, daily porcelain, electric porcelain, aluminum, copper, zinc smelting, steelmaking and rolling, ironmaking, metal heat treatment, environmental protection, and other fields.

Silicon Nitride Bonded Silicon Carbide Brick

Silicon nitride bonded silicon carbide brick is a kind of advanced refractory material with silicon carbide sand as the main raw material and silicon nitride as the bonding phase. Since SiC and Si3N4 are covalently bonded compounds, sintering is difficult, and reaction sintering is usually used in industrial production. SiC is used as aggregate, metallic silicon powder is added, and a reasonable particle grading, mixing system and forming process are selected. The dried green body is fired in a nitrogen atmosphere in a dedicated firing equipment. During the firing process, the generated Si3N4 (matrix bonding phase) is gray-white crystals. It can effectively combine SiC particles (aggregates) to form a spatial network structure, so that the brick has incomparable characteristics of other refractory materials. Silicon nitride bonded silicon carbide material is a special silicon carbide brick used in grinding wheels, ceramics, electric porcelain and other industries.

Superior Performance of Silicon Nitride Combined with Silicon Carbide Bricks

The high-temperature flexural strength of silicon nitride combined with silicon carbide is 4 to 8 times that of ordinary refractory materials. The thermal expansion coefficient is half of that of high-aluminum refractory materials. The thermal conductivity is 7 to 8 times that of general refractory materials, and the strength increases with the increase of temperature. When the temperature rises to 1400℃, the strength begins to decrease. But when the temperature drops to 1500℃, the room temperature flexural strength index is still maintained. The thermal conductivity of this material gradually decreases with the increase of temperature. It has the characteristics of high density, high strength, good thermal shock stability, high load softening point, good thermal conductivity, and high resistance value. And it has excellent resistance to melting erosion and oxidation resistance such as cryolite, aluminum fluoride, sodium fluoride and calcium fluoride. Its performance is as follows:

1) Silicon nitride combined with silicon carbide bricks are hard, with a Mohs hardness of about 9. It is a high-hardness material among non-metallic materials, and its hardness is second only to diamond.
2) Silicon nitride combined with silicon carbide bricks have high strength at room temperature, and maintain almost the same strength and hardness as at room temperature at high temperatures of 1200-1400℃. Depending on the use atmosphere, the maximum safe use temperature can reach 1650-1750℃.
3) The thermal expansion coefficient is small, and the thermal conductivity is high compared to silicon carbide bricks. It is not easy to produce thermal stress, has good thermal shock stability, and has a long service life. It has strong high-temperature creep resistance, corrosion resistance, extreme cold and heat resistance, oxidation resistance, and is easy to make bricks with high dimensional accuracy that meet the requirements.

Silicon Nitride bonded Silicon Carbide Bricks — Silicon Nitride Bonded Silicon Carbide Bricks

Application of Silicon Nitride Combined with Silicon Carbide Bricks in the Ceramic Industry

Building Sanitary Ceramics Industry

At present, in the firing of ceramic products, roller kilns are mostly used to fire sanitary ceramics and wall and floor tiles, and the rollers of the roller kilns are basically made of silicon nitride combined with silicon carbide. The application of silicon nitride combined with silicon carbide rollers solves the problem of high firing temperature and heavy load, effectively reduces product energy consumption and improves product quality.

Daily Ceramics Industry

There are two ways to fire daily ceramics: one is to use a shuttle kiln with a sagger or similar kiln; the other is to use a roller kiln in the same way as building sanitary ceramics. The use of kiln tools made of silicon nitride combined with silicon carbide can significantly reduce the mass ratio of kiln tools to bricks, save energy and reduce consumption, and at the same time improve the quality and qualified rate of products. Using a roller kiln to fire daily ceramics, the use of silicon nitride combined with silicon carbide rollers increases the service life of the kiln.

Electrical Porcelain and Electronic Ceramics Industry

The electrical porcelain and electronic ceramics industry requires kiln furniture materials with high temperature, high strength, good thermal stability, long service life and reasonable price, which provides a broad market for the application of silicon nitride combined with silicon carbide kiln furniture.

Silicon nitride combined with silicon carbide has high density, high strength, good thermal shock stability, high load softening point, good thermal conductivity and high resistance. It also has excellent resistance to melting erosion and oxidation resistance of cryolite, aluminum fluoride, sodium fluoride, and calcium fluoride. It plays an increasingly irreplaceable role in building sanitary ceramics, daily ceramics, electrical porcelain, non-ferrous smelting, steelmaking and rolling, ironmaking, heat treatment, environmental protection and other industries. To buy high-quality silicon carbide bricks, please choose Rongsheng. Contact Rongsheng for free samples and quotes.

Does the Size of Refractory Particles have an Effect on the Performance of Refractory Ramming Materials?

2025-07-04 by globalrefractory

The size of refractory raw material particles has an impact on the performance of refractory ramming materials, especially the tensile force and impact resistance of the materials.

Granular Materials of Refractory Ramming Materials

The particles of refractory ramming materials are generally of different particle gradations of 0-5mm, and the particles are also 0-7mm, and will not exceed 8mm particles. Because the particles are small, the ramming will be more compact.

However, there are also 0-3 particles of refractory ramming materials. This is because some parts with too small gaps have special particle requirements. Otherwise, the 0-3 particles have low tensile force and insufficient impact resistance. In many cases, the 0-3 particle grading will not be used for process proportioning. For example, the particles of the baking-free ramming material used in the blast furnace slag skimmer will be larger. There are also refractory castable manufacturers that put the particles into 10mm, so that the impact resistance is strong during use, and it is also more wear-resistant.

Ramming Material Used for the Lining of the Furnaces

Reasonable Particle Grading and Reasonable Process

Refractory materials themselves belong to applied disciplines, with applicability as the ultimate goal. If there is no special requirement under special circumstances, the particle grading between 0-8mm should be used as the proportion. Too large ramming is not dense, too small tension is not good and the impact resistance is not enough.

Reasonable particle grading and reasonable process ratio will produce products suitable for use. Therefore, the production of refractory ramming materials should be based on the use of different furnace linings, and reasonable particle grading is the most scientific.

According to the current market usage, 0-7mm particle grading is a more suitable ratio, and it is also a way to use the ratio combined with the particle grading of the ramming material. Although larger particles are OK, it is most suitable not to exceed 10mm, which is easy to construct.

In summary, the size of the particles does affect the performance of refractory ramming materials. Therefore, it is also a matter of attention in production and use. Although indicators are important, only those suitable for use are the best.

Silica Ramming Refractory Material for Intermediate Frequency Furnace

Why is Boric Acid Used in Refractory Ramming Materials?

Different refractory materials are suitable for smelting different metals or alloys. At present, medium frequency induction furnaces are widely used in metallurgy and foundry industries. During the use of induction furnaces, the impact, friction and electromagnetic stirring of the charge will aggravate the erosion of the furnace lining. The factors that cause the reduction of service life are:

(1) Operating conditions.
(2) Furnace building and baking process.
(3) Rationality of refractory raw materials.

Quartz sand refractory ramming material is widely used in the production of molten cast iron and cast iron alloys because of its high cost performance and good thermal shock stability, mechanical strength and resistance to acidic slag corrosion.

However, there are many types of quartz ores, and their important performance indicators such as impurity content and crystallinity are different. As a result, the service life of quartz refractory materials in medium frequency furnaces varies greatly.

Theoretically, quartz with low impurity content and high crystallinity has high mechanical strength and excellent thermal shock stability, and is particularly suitable as a lining material for large-capacity medium-frequency furnaces. However, the sintering performance of this quartz is poor, which will affect the service life of the lining.

Quartz ramming material is made of high-quality large-grained quartz sand as the main raw material, supplemented by a binder and a sintering promoter. During the production process, an important binder needs to be added, and boric acid is used as a sintering binder. During the sintering process of the furnace lining, boric acid is dehydrated and converted into boric oxide. At high temperatures, boric oxide plays the role of a high-temperature binder and promotes the sintering of the workpiece.

In addition, during the high-temperature use of quartz ramming material, quartz will react with boric acid B2O3 to form tridymite and cristobalite. Boric oxide can reduce the synthesis and sintering temperature of quartz without causing obvious harm to the material properties. Therefore, boric acid is an important raw material for quartz ramming material.

We know from a set of experiments that boric acid plays an important role in quartz ramming material. The main raw material is quartz sand, whose critical particle size is 5mm. Different particle gradings are carried out according to the maximum stacking density, and boric acid is added as a sintering agent. Then the test block is made and the total weight loss of quartz is observed to be about 3.0 when the temperature rises from 25℃ to 1500℃ in the furnace. When the temperature rises from 25℃ to 1000℃, the weight loss of quartz is about 2.2, and this part of the loss mainly comes from the evaporation of free water and crystal water. Due to the evaporation of free water, an endothermic peak appears at 80℃. Due to the transformation of β-quartz to α-quartz, there is an endothermic peak at 580℃. Due to the transformation of α-tridymite to α-quartz, a large endothermic peak appears at 1250℃. There are also thermal effects of other crystal transformations, but they are not very obvious, indicating that its phase change is easier to occur.

The linear change rate of the ramming material after sintering increases with the increase of the content of the sintering agent boric acid. The change rate of the ramming material sintered at 1100℃ generally shows an increasing trend, and the linear change of the ramming material sintered at 1600℃ first increases and then decreases. It is worth noting that the linear change rate of the ramming material sintered at 1100℃ is negative. The reason is that the sintering agent boric acid begins to form a liquid phase at this temperature, causing the sample to shrink. The linear change rate of the ramming material sintered at 1600℃ is positive, and the sample expands. The reason is that quartz has a transition from a low-temperature phase to a high-temperature phase at high temperature, accompanied by volume expansion. This phase change is irreversible, and the volume expansion still exists after the temperature is reduced.

Effect of the content of sintering agent boric acid on the compressive strength of the ramming material. With the increase of the boric acid content, the compressive strength of the ramming material shows a significant increasing trend. It can be seen from the B2O3-SiO2 phase diagram that after adding boric acid, a liquid phase appears in the ramming material at about 440℃, thereby promoting sintering and improving the strength of the ramming material. As the temperature rises, the amount of liquid phase increases, and the strength of the ramming material is bound to increase. However, due to the phase change of quartz at high temperature, the volume expansion associated with the phase change will partially offset the sintering effect of boric acid, making the influence of boric acid content on the strength of ramming material sintered at 1600℃ smaller. Boric acid mainly improves the medium-temperature sintering strength of the ramming material, while the role of the sintering promoter during high-temperature sintering is relatively small, and at this time it still mainly depends on quartz.

Forming Process of Refractory Materials

2025-06-202025-06-13 by globalrefractory

Semi-dry pressing

During the semi-dry pressing process, the loose materials do not have enough moisture and must be subjected to greater pressure. With the help of pressure, the blank particles are redistributed. Under the action of mechanical bonding force, electrostatic attraction and friction, the blank particles are tightly combined, elastic deformation and brittle deformation occur, air is discharged, and the blank particles are combined into products with a certain size, shape and strength.

The degree of action of the above forces depends on the particle shape, the physical and chemical properties of the blank and the surface state of the particles. For particles with complex shapes, mechanical bonding force plays a major role. For particles with simple shapes, friction and static electricity cause the main effects.

Within a certain range when other process conditions are the same, the pressure increases during pressing, the porosity of the blank decreases, the density increases, and the strength increases accordingly.

The blanks and bricks of refractory materials are three-phase systems composed of solid matter, water (or other binders in other states) and air. During the entire pressing process, because the amount of phase and liquid phase does not change, the amount of air in the blank is compressed and reduced, and the volume of the compressed blank is also reduced accordingly.

Slurry injection molding method

Use powdered raw materials, select appropriate degumming agents (deflocculating agents) to evenly suspend them in the solution, adjust them into mud, pour them into a water-absorbent mold (generally a gypsum mold) to absorb water, and form a green body according to the shape of the model. This method is called slurry injection molding.

For materials that do not react with water, water is generally used as a suspension, and the moisture content of the mud is as high as 35~45%. For some materials that are easy to react with water, such as CaO, MgO, etc., organic matter can be used as a suspension, such as anhydrous alcohol. This method is suitable for the production of thin-walled hollow products. Such as thermocouple sleeves, high-temperature furnace tubes and crucibles. Various oxide products, from small to large pieces, have adopted this method.

For thin-walled hollow products, hollow casting is generally used. Inject mud into the model, and after a certain period of time, the raw materials are adsorbed on the model wall. When the specified thickness is absorbed, the internal mud is discharged. Dry to an appropriate degree and then demold, the gypsum mold can be used repeatedly. The mud used should have good fluidity, and the density is generally between 1.65~1.80g/cm2.

For the casting of thick and large products, solid casting is suitable. The mud used should be large, and the density should generally be above 1.8g/cm3. The thick mud has thixotropy, so it should be strongly mechanically stirred before casting to make it fluid. After casting, it can be solidified by standing for a period of time. Therefore, the plaster mold used does not need to have high water absorption.

Plastic molding method

The moisture content of the blank used in the plastic method is generally above 16%. The prefabricated blank is put into the mud extruder, extruded into mud strips, and then cut. Then the blank is made into a blank according to the required size, and the blank is pressed by a press to make the blank have the specified size and shape.

The moisture content of the blank is related to different raw materials and products. For plastic clay materials, the moisture content can be appropriately reduced to 10~15%. The critical pressure of the mud extruder is related to the moisture content of the blank.

The plastic molding method is mostly used to prepare large products. Depending on the molding operation, it can be formed by hand, semi-mechanical (such as clamping hammer) or machine pressing.

With the improvement of refractory process technology and the development of molding machinery and equipment, the application of plastic molding methods in the refractory industry has a tendency to decrease.

Vibration molding

When the material vibrates at a frequency of about 3,000 times per minute, the particles of the blank collide with each other, and dynamic friction replaces the static friction between the particles, and the blank becomes a fluid particle. Due to the energy input by the vibration, the particles have the ability to move in three dimensions inside the blank, so that the particles can be densely packed and filled in every corner of the model and the air can be squeezed out. Therefore, even under very small pressure, a high-density product can be obtained. When molding a variety of products, vibration molding can effectively replace heavy high-pressure brick presses. For example, crank lever brick presses and hydraulic presses can mold complex special-shaped and giant bricks that require manual molding or ramming molding, greatly improving labor productivity and reducing labor intensity. Vibration molding is also suitable for molding materials with a large difference in density and molding fragile brittle materials. Since the material particles are not destroyed during molding, it is suitable for molding easily hydrated materials, such as tar dolomite, tar magnesia, etc.

Hot Pressing

Refractory products made by sintering require a long calcination time, and the porosity is still as high as 10~25%. Ceramic materials and products prepared by sintering still have a true porosity of 3~5% even under ideal conditions. Non-oxide ceramic materials, such as carbides and nitrides, have even greater porosity.

It is difficult to make very dense products. This is because during the sintering process, the gas pressure in the pores increases, offsetting the role of the interface energy as a driving force. On the other hand, closed pores can only be filled by diffusion of substances inside the crystal, but internal diffusion is much slower than interface diffusion. If the sintering process is carried out to the final stage and the product reaches an ideal dense state, there are two methods:

One is to use vacuum sintering to avoid gas accumulation in the pores.
The other is to apply pressure during sintering to ensure sufficient driving force.

The latter is called hot pressing.

Compared with the common sintering method, the advantage of hot pressing is that it can obtain special products with very high density, and its density value can almost reach the theoretical value. Adjusting the hot pressing conditions can control the grain formation, and hot pressing at high temperature is conducive to the contact and diffusion between particles. Thus, the sintering temperature is reduced (compared with the common sintering method).

Hot Pressing Molding (Hot Pressing Grouting)

Hot pressing is one of the grouting methods and is a relatively new method for producing ceramic products and special refractory materials.

Hot pressing generally uses an organic binder as a dispersion medium and silicate mineral powder as a dispersed phase. At a certain temperature (70~85℃), it is prepared into a slurry and then molded into a metal model. This method is suitable for the production of small products with complex shapes and special requirements. It is also suitable for the production of materials with low plasticity, such as the molding of high-aluminum materials. Its semi-finished products have high mechanical strength and can be turned and drilled by machine tools. The plaster model and drying process can be omitted, the equipment is simple, and mechanization is easy to achieve.

Electric Melting Method

The refractory raw materials are melted in an electric arc furnace, and then the melt is poured into a refractory casting mold for casting. Because the fluidity of the fluid must be good, the general pouring temperature must be between 1900~2000℃. The casting generates a stable crystal phase during the solidification process and forms a fine crystalline structure. After pouring, the casting mouth should be removed, and the casting should be slowly cooled for several days to prevent cracks from appearing during cooling. The casting block is finally processed on the surface to become a product. The products formed by this method are mainly fused zirconium mullite bricks, chrome corundum bricks, and fused quartz bricks. It is mainly used to build the bottom of the glass tank kiln. Most of the raw materials for producing rebonded bricks are also produced by this method.

Isostatic Pressing

Isostatic pressing is a new forming technology developed later. This method mainly applies the Pascal principle to pressurize the liquid and evenly transfer its pressure to the powder through the rubber film, so it has the following characteristics.

Formability. The pressurization is non-directional, and a green body with uniform density can be obtained, and there will be no layer density phenomenon during other mechanical pressing. It is easy to press into products with complex shapes.
Sinterability. Since the green body has uniform density and shrinkage during firing is non-directional, it will not cause stress due to density difference and cause firing cracks. Due to the high density, the firing temperature is relatively reduced.

The main equipment consists of a high-pressure container and a high-pressure pump. During molding, the powdered material is placed in a rubber film or a plastic film, placed in an ultra-high-pressure container with a thick steel wall, and a high-pressure liquid is injected by a high-pressure pump. The working pressure is generally above 343MPa. This method only formed small products at the beginning, and has now developed to press large products.

What are the Factors that Affect the Performance of Self-Flowing Castables?

2025-05-23 by globalrefractory

At present, most of the iron troughs of large blast furnaces use vibrating castables, which have many disadvantages due to the influence of many factors. For example, due to the influence of workers’ on-site operation technology, the vibrator does not vibrate enough, resulting in insufficient density of the cast body, excessive vibration and particle segregation, and it is easy to leave cavities when the vibrating spoon is pulled out. In addition, the vibrator is too noisy, affecting the construction environment. Self-flowing castables can automatically flow, flatten, compact and solidify without vibrating with a vibrator, avoiding the problems of vibrating castables. In order to meet the needs of the iron troughs of modern large blast furnaces, refractory manufacturers have developed self-flowing castables suitable for the iron troughs of large blast furnaces.

Rongsheng Self-Flowing Refractory Castable for Sale

Application Advantages of Self-Flowing Castables

After France developed self-flowing castables, Japan studied self-flowing iron channel castables, which were developed based on low-cement and ultra-low-cement castables. It is a viscoplastic material with a low yield value and a certain plastic viscosity developed based on the principle of rheology. Its advantages are:

(1) No vibration is required, and it can be automatically poured and compacted, greatly reducing labor intensity.
(2) Compared with vibrating castables, the pore size is small and evenly distributed.
(3) If the pumping process is used during construction, labor is reduced and work efficiency is improved.
(4) It has stronger adaptability than vibrating castables and can be cast in any shape.
(5) The performance is equivalent to or better than that of vibrating castables.
(6) Reduce noise pollution.
(7) It is easy to conduct construction performance tests on-site.

Therefore, the application of self-flowing castables has gradually become popular, and its scope is constantly expanding. Some people think that the performance of self-flowing castables is not as good as that of vibrating castables. It is outdated. By optimizing the particle size and matrix composition, self-flowing castables can be comparable to vibration castables of the same material in terms of water addition, density, and strength, and some properties are even better.

Factors Affecting the Fluidity of Self-Flowing Castables

There are many factors that affect the fluidity of self-flowing castables, mainly particle grading, water reducer, micro powder, cement type, and addition amount. They will be described below.

Effect of particle grading on the performance of self-flowing castables

The most famous and convenient stacking pattern in the field of refractory materials is the Andreassen distribution pattern. To obtain the best flow performance, an optimal stacking pattern is required. The Andreassen pattern basically solves this problem.

It is reported that when the particle composition is coarse particles (>1mm): 35%~50%; medium particles (1~0.045mm): 16%~30%; fine powder (<0.045mm): 23%~40%, vibration-free castables can be obtained. When the critical particle size is 8mm, the self-flowing castable can be obtained when its R (R=coarse particles/fine particles) is about 1.9. As the R value decreases, the self-flow value decreases significantly, and the viscosity of the castable increases. When the critical particle size is 5mm, the R value is between 1.5~1.85 to obtain self-flowing castables.

In addition, because self-flowing castables are developed based on rheological principles. It is a viscoplastic material with a low yield value and a certain plastic viscosity. Therefore, it requires a suitable particle size composition and an appropriate ratio of aggregate to matrix. As shown in the figure. When the particle composition is in zone 1, coarse and fine particle segregation will occur. When it is in zone 2, coarse particle collapse will occur. When it is in zones 3 and 4, a strong plastic state will occur. Only in zone 5 will it have self-flowing properties.

Effect of water reducer on the performance of self-flowing castables

Common water reducers include sodium hexametaphosphate, sodium tripolyphosphate, and high polymers. Different bonding systems should use appropriate water reducers. For example, sodium tripolyphosphate and sodium hexametaphosphate are more effective for silicon micropowder than for alumina micropowder. For silicon-free micropowder systems, high polymers are more effective as water reducers, and there are also quite strict requirements on the amount of water added.

Water reducer is a surfactant. The added inorganic and organic water reducers are both anionic. When dissolved in water, inorganic water reducers ionize anionic groups M and organic water reducers ionize anionic groups N. Since M is not a hydrophobic group, its surface activity is not significant, and it is mainly adsorbed on the surface of colloidal ions in the form of chemical adsorption. The organic anion group N is a hydrophobic group with strong surface activity, which is adsorbed on the surface of colloidal ions in the form of physical adsorption. A double electric layer is formed on the surface of cement and ultrafine powder particles, thereby changing the electromotive potential of the particle surface. Generate electrostatic repulsion between particles, so that cement ultrafine powder particles repel each other, disperse particles, and prevent the spontaneous formation of particle flocculation structure. And make the particles fully dispersed, homogenized and fill tiny gaps, release the water bound by the condensed particles, and fully wet the particle surface. It has a certain fluidity, and the macroscopic manifestation is that the rheological parameter shear stress of the slurry is reduced and the rheological properties are improved. In short, inorganic water reducers mainly rely on the electrostatic repulsion mechanism of changing and increasing the electromotive potential of the particle surface to achieve the purpose of dispersion. Organic water reducers mainly rely on the surface activity of organic water reducers to achieve the purpose of dispersion.

Effect of micropowder on the performance of self-flowing castables

1) Effect of silicon micropowder on self-flowing castables

Silicon micropowder has good rheological properties. When the same fluidity is achieved, as the amount of silica fume added increases, the amount of water added decreases, which enhances the filling property of the material, thereby increasing its volume density and reducing its apparent porosity. This is because there are a large number of ultrafine particles in SiO2 micropowder, which have a large specific surface area. In water, the surface of these particles is positively charged by adsorbing surfactants and has a certain zeta potential. The electrostatic repulsion between particles with the same charge causes the particles to disperse and form a uniform, low-viscosity slurry, which is dispersed between aggregate particles. It reduces the friction between aggregate particles, acts as a lubricant, and is conducive to improving the fluidity of the castable.

In ordinary castables, silicon micropowder becomes the first choice to obtain higher mechanical strength under the premise of lower water addition. The many chemical and physical properties of silicon micropowder directly affect the various properties of the castable. The higher the carbon content, the greater the pH value, and the construction time is drastically shortened. The higher the silica content, the better the construction performance when the pH value is around 7 and the carbon content is less than 0.5%.

When the same silicon powder is used, the mechanical strength at room temperature increases with the increase in the amount added, and the high-temperature flexural strength reaches the highest value at a certain value. After that, the flow value decreases with the increase in the amount added, the strength performance decreases, and the high-temperature performance also deteriorates. In particular, the linear change rate has a significant increasing trend.

Therefore, silica fume plays a good role in improving the construction performance of castables, but has an adverse effect on the strength after high-temperature firing.

2) Effect of alumina powder on the performance of self-flowing castables

In the Al2O3-SiO2 system, alumina powder is an indispensable filler. As a key parameter in the formulation, alumina powder affects the sintering degree and strength of the castable when determining the flow of the castable.

The literature points out that adding alumina powder with a moderate specific surface area and low Na2O content can obtain better flow properties. Of course, the additive system used for each alumina powder may be different.

Although alumina powder can promote sintering, it cannot be added too much because it can cause the castable to shrink significantly.

Both silicon powder and alumina powder have a filling effect on the capillaries, releasing the free water in them, increasing the solvent ratio of the system, weakening the thixotropic structure, and reducing the viscosity. When the amount of ultrafine powder added is small, there are a large number of capillaries, and the ultrafine powder mainly shows a filling effect. When the amount added is large, the capillaries are saturated and filled, and the ultrafine powder mainly shows a participating effect.

Effect of cement on the performance of self-flowing castables

The biggest influence of cement addition on the strength value of self-flowing castables is the strength value. As the amount of cement added increases, the drying strength also increases. For fluidity, it is not as sensitive as ultrafine powder and admixtures within a certain range. But relatively speaking, as the amount of cement added increases, its flow value tends to decrease.

In addition, the type and amount of cement added affect the initial setting time and final setting time. Therefore, the type and amount of cement added should be determined according to the construction conditions.

In addition to particle grading and particle shape, micro powder variety and addition, water reducer variety and addition, the factors affecting flow performance include cement fineness, activity and setting time, mixer type and mixing time, which all have an impact on self-flowing performance. This requires that, in the research and production of self-flowing castables, different measures should be taken according to the specific conditions of production and construction, and the best construction performance and use performance should be obtained through experiments.

The Important Role of Checker Bricks in Coke Oven Systems

2025-05-202025-05-02 by globalrefractory

Coke oven checker bricks play a vital role in the coke oven system. They are designed to absorb and release heat with high efficiency, transferring the heat of the exhaust gas to the cold air or blast furnace gas through the heat exchange process in the regenerator, thereby significantly increasing the temperature of these gases. This process not only helps to reduce the gas consumption required for coke oven heating, but also reduces energy consumption and carbon emissions in the coking process.

How do Checker Bricks Work in Coke Oven Systems?

Specifically, checker bricks work in the following ways:

‌Heat exchange‌: During the combustion process, when the hot exhaust gas passes through the regenerator, the checker bricks absorb most of the heat, significantly reducing the temperature of the exhaust gas. Subsequently, when the cold air or blast furnace gas passes through the regenerator, the checker bricks release their stored heat, preheating these gases to above 1000℃.

Reduce energy consumption and emissions‌: Through this heat exchange process of rising and falling airflows, the coke oven can effectively recover and utilize heat, thereby reducing dependence on external heat sources, reducing energy consumption and carbon emissions.

Maintain uniform furnace temperature‌: The unobstructed and good heat storage capacity of the regenerator is essential to maintaining uniform furnace temperature, which is of great significance for reducing production costs and reducing environmental pollution.

In summary, coke oven checker bricks, through their unique heat exchange mechanism, not only improve energy utilization efficiency, but also contribute to environmental protection, and are an indispensable component of the coke oven system.

Construction steps and methods for coke oven heat storage chamber masonry

Laying of sliding layer in coke oven heat storage chamber

Build the foundation platform first, adjust and correct the resistance wall, and prepare to lay the sliding layer after passing the inspection.
When using river sand to lay the sliding layer, the river sand must be flat and uniform in thickness.
A layer of petroleum asphalt felt must be laid between the refractory bricks and the river sand sliding layer before masonry.
When using thin steel plates as sliding layers, the following requirements should be observed:

- (1) The sliding layer should be laid once before bricklaying, and the bottom of the steel plate should be coated with yellow dry oil before laying.
- (2) After the steel plate is laid and inspected and passed, apply a thin layer of yellow dry oil on the surface of the steel plate, then lay a layer of petroleum asphalt felt, and then lay bricks.
- (3) It is strictly forbidden to recycle mud with oil stains.

Bricklaying process of small flue and regenerator wall in coke oven regenerator

Before laying the small flue, mark the width edge of each wall at the center line mark of the combustion chamber, and mark the height line of each brick layer on the vertical pole. You can also use the method of measuring and laying out the lines by wall.
The first layer of masonry of the small flue should be pre-laid dry. After checking that the width of the reserved expansion joint is qualified, lay out the lines to lay out the furnace head of the main wall of the small flue.
The furnace head position needs to be laid several layers of bricks at a time, and the wall should be stepped to prevent the furnace head from shifting on the sliding layer.
During masonry, check and verify the horizontal and vertical degree of the masonry according to the center line many times to prevent the furnace wall from twisting.
The masonry process should be cautious and careful, and the furnace head position should not collide. When changing shifts, first check and confirm whether the furnace head position has been moved and make adjustments.
Check the straightness of the masonry wall at any time. After the small flue wall is completed, check the brick layer elevation and gradually level it.

Laying process of lining bricks and grate bricks in coke oven regenerator

Lay the center partition wall first, and then lay the lining bricks after the masonry is completed and the construction area is cleaned. The laying order should be from the center to both sides.
Lay yellow cardboard when laying bricks, and use wooden supports to fix the lining bricks after they are laid to ensure that the width of the expansion joint between the lining bricks and the furnace wall does not change during laying.
After the lining bricks are laid, clean the bottom and wall of the small flue, lay a layer of 10-15 mm clean sawdust at the bottom of the small flue, and then lay the grate bricks layer by layer from the center to both sides. The refractory mud squeezed out of the brick seams of the brick layers should be cleaned at any time.
When laying grate bricks with holes, strictly check the aperture of the grate bricks, and then lay them after they are qualified. When laying grate bricks in air and gas regenerators, first carry out pre-laying dry laying and seam inspection respectively, and then formally lay them.
Use a wooden ruler to check the straightness of the grate brick leg platform. The gap error should meet the construction requirements.
After the grate brick is laid, clean the expansion joint and inspect it. If it is qualified, lay a wooden protective plate on the grate brick. The gap between the protective plate and the wall shall not exceed 15 mm.

Coke oven heat storage chamber wall brick laying process

Use the matching refractory mud for the corresponding masonry according to the design drawings. When changing the refractory mud material, the preparation utensils should be cleaned.
According to the elevation mark of the gas pipe brick, start from the first gas pipe brick on both sides of the furnace head, and then lay the gas pipe bricks in other parts in sequence.
During the laying process, the center distance between the gas pipe bricks should be corrected using a standard plate, and the length of the standard plate should be greater than half of the furnace length. The vertical center line of the coke oven, the front line and the center position of each gas pipe in between should be marked on the standard plate. The flatness of the masonry should be checked and aligned every two layers.
The refractory mud in the mortar joints of the gas pipe bricks should be filled full and dense, and the refractory mud entering the pipe brick hole should be cleaned. Before the end of work every day, the gas pipe bricks should be thoroughly cleaned from top to bottom to ensure that the gas pipe bricks are unobstructed.
The location of gas pipe bricks should be checked at any time during the construction, and the gas pipe bricks should not be collided or twisted when the heat storage room wall bricks are laid.
The central partition wall should be built after the main single wall is built to a certain height (generally not more than 1.2 meters). During the construction, expansion joints and sliding joints should be reserved according to the construction design requirements, and the filling should be full and dense.
The elevation between the main wall of the heat storage room and the adjacent single wall, between the main wall and the adjacent main wall, and between the walls should be checked frequently to keep them consistent.

Laying process of checker bricks in coke oven regenerator

After the furnace body is laid, blow and clean the secondary grooves on the top of the regenerator cover, and mark the control line between the central partition wall and the sealing wall on the regenerator wall.
Use compressed air to blow the checker bricks clean and start preparing to lay the checker bricks.
When the first layer of checker bricks is dry-laid, check the placement and stability of the checker bricks before the lower layer of checker bricks can be dry-laid.
The checker brick layers after the second layer should be stepped back from the central partition wall to the furnace head for dry-laying.
Frequently check the lattice holes of each layer of checker bricks for smoothness, and the upper and lower layers of checker bricks should be aligned.
Yellow cardboard can be used to maintain the gap width and stability between the checker bricks and the regenerator wall, and non-flammable materials must not be used as padding.
After the dry-laying of checker bricks in each regenerator is completed and the inspection is qualified, start laying the regenerator sealing wall.
The regenerator wall and checker bricks of the sectional regenerator coke oven should be laid alternately in sections. Before each section of checker bricks is laid, the sealing wall or partition wall of this section should be completed first, and the grooves on the wall should be cleaned. During the dry laying of checker bricks, pay attention to prevent the refractory mud from falling into the checker bricks of the next section. After the dry laying is completed and the inspection is qualified, immediately cover the protection plate. The protection plate should be set firmly and tightly, close to the wall of the regenerator to prevent the refractory mud from leaking into the checker bricks.

How to Repair Cooling Wall Damage After Carbon Bricks are Soaked in Water or Broken?

2025-04-142025-04-11 by globalrefractory

During the operation of the blast furnace, due to improper operation or different degrees of resistant material erosion, local cooling walls may burn out or wear and leak. Carbon bricks will undergo brittle fracture at a temperature of about 800°C. For cooling walls above the tuyere zone, the cooling walls can be quickly replaced by stopping the wind and lowering the material line or by emergency repair, and the lining can be hot-sprayed. Once the cooling wall in the furnace area leaks, the internal carbon bricks are soaked in water, or the carbon bricks are brittlely fractured, and heat conduction is blocked, there will be a risk of iron leakage from the furnace, causing major accidents. At present, the repair of carbon bricks in the furnace is generally to stop the furnace and clean the furnace. After replacing the cooling wall, carbon bricks are laid from the inside or high thermal conductivity materials are poured. The maintenance cycle lasting more than 20 days is inefficient and greatly affects the rhythm of blast furnace smelting.

In order to solve the defect of long repair period, a national new patent technology was developed – a repair method for damaged cooling staves and carbon bricks for blast furnace hearth after water immersion or brittle fracture. This repair method has the following characteristics:

First, the furnace skin at the damaged cooling stave is cut off and the damaged cooling stave is removed, the damaged carbon bricks are removed, and a new cooling stave and a new furnace skin are installed. There is a gap between the new cooling stave and the surrounding cooling staves. The lower part of the new furnace skin is provided with a first grouting hole, the middle part is provided with a second grouting hole, and the top is provided with an exhaust hole.
Second, the grouting pipe is passed through the first grouting hole and the new cooling stave in turn, and the pipe mouth is extended into the gap between the new cooling stave and the carbon brick after the gap between the surrounding cooling staves. The high thermal conductivity castable is injected through the grouting pipe at a certain pressure and begins to fill the gap between the new cooling stave and the carbon brick. During the injection process, the high thermal conductivity castable is injected into the gap between the new cooling stave and the surrounding cooling staves through the gap between the new cooling stave and the new furnace shell.
Third, observe the filling situation from the second grouting hole. When the high thermal conductivity castable spreads to the same height as the second grouting hole, stop filling and seal the first grouting hole.
Fourth, after the grouting pipe passes through the second grouting hole and the gap between the new cooling wall and the surrounding cooling wall in turn, the pipe mouth extends into the gap between the new cooling wall and the carbon brick. Pour the high thermal conductivity castable through the grouting pipe at a certain pressure and start filling the gap between the new cooling wall and the carbon brick. During the filling process, the high thermal conductivity castable is poured into the gap between the new cooling wall and the surrounding cooling wall into the gap between the new cooling wall and the new furnace shell.
Fifth, observe the filling situation from the exhaust hole. When the high thermal conductivity castable spreads to the same height as the exhaust hole, stop filling. Seal the second grouting hole and the exhaust hole.

The repair method has achieved the following beneficial effects:

First, the repair cycle of damaged cooling walls and carbon bricks is greatly reduced, and the repair can be completed in only 1 day.
Second, it ensures that each layer of gaps is fully filled, thereby ensuring normal heat transfer and gap-free insulation.
Third, the maintenance cost is extremely low, and only normal grouting is required.
Fourth, the economic benefits of blast furnaces are greatly improved, and the market prospects are extremely broad.

Raw Materials and Characteristics of Siliceous Refractory Materials

2025-05-192025-03-21 by globalrefractory

The raw material of siliceous refractory materials is mainly silica. Silica is not the name of a mineral but an industrial term. In industry, blocky siliceous raw materials are called silica. Its main mineral component is quartz, and its main chemical component is SiO₂. Silica can be classified according to the degree of structural density, crystal transformation speed and degree of heating expansion. For example, according to process classification, silica can be divided into crystalline silica, cemented silica, and silica sand. According to the rock classification method, silica can be divided into vein quartz, quartzite, quartz sandstone, flint rock, and quartz sand.

Silica Refractory Bricks Rongsheng Manufacturer

Quartzite

Quartzite is widely distributed in my country, mainly produced in Henan, Liaoning and other places. It has a grayish white or light gray appearance, and its SiO₂ content is above 98%. The main mineral composition is quartz, and the grains are generally between 0.15 and 0.25 mm. But it often contains clay, mica, chlorite, feldspar, rutile, hematite, limonite, etc. Its crystal form transformation is slow, and it can be used to make various silica bricks.

Vine quartz

Vine quartz is mainly produced in Jilin, and its appearance is milky white, and the SiO₂ content is above 99%. The main mineral phase quartz grains are large, generally larger than 2 mm, and the texture is pure, and some are interspersed with red or yellow-brown rust. Because of its slow SiO₂ crystal transformation, large expansion, and easy to loosen. If the process conditions are not appropriate when making silica bricks, cracks and cracking are prone to occur. The product has high porosity and low strength, but good slag resistance.

Quartz sandstone

Quartz sandstone is widely distributed in my country. There are quartz sandstone deposits of good quality and large scale in Hebei, Sichuan, Hunan, Hubei and other places. The appearance of quartz sandstone is light yellow and light red. The SiO₂ content is generally above 95%, mixed with certain impurities. The main crystal phase quartz coarse particles are about 1~0.5mm, and the fine particles are 0.25~0.1mm. Due to the large number of impurities in quartz sandstone, the density is poor, the strength is low, and the particles are small. The silicon oxide crystal form changes quickly during firing, and it is easy to loosen after firing. It can only be used to make general silica bricks.

Flint rock

Flint rock is mainly produced in Shanxi, China. The main component SiO₂ content is above 95%, and it also contains a certain amount of Al₂O₃, Fe₂O₃, MgO, CaO, Na₂O, K₂O, etc. The outside is red-white and bluish-white. When heated, the crystal form is easy to transform, and various silica bricks can be made.

Quartz sand

Quartz sand, also known as silica sand, has a main component SiO₂ of more than 90%, generally up to 95%. The main mineral phase quartz particles are uniform in size, smooth in surface, and excellent in sorting, with a particle size between 0.5 and 0.15 mm. Quartz sand can be used as a raw material for general silica bricks, mostly used as ramming material. There are quartz sand deposits with good texture in Shandong, Guangdong, Jilin, and Hunan, China. Siliceous refractory mud.

Crystalline silica and cemented silica

Crystalline silica has good purity and good density, and can be used as a raw material for brick making and preparing siliceous refractory castable. However, cemented silica contains more impurities and is easy to loosen after burning, so it is rarely used. Silica raw materials must be sorted and washed with water before use to reduce the content of Al₂O₃ in the raw materials. Because the source of Al₂O₃ in silica raw materials is mostly clay attachments on the surface of silica. One-third of the Al2O2 and residues bonded in quartz cracks can be removed by flushing.