How to Solve the Problem of Tundish Refractory Lining Collapse?

The dry monolithic refractory material working layer of the tundish often collapses during the baking and use process. As shown in Figure 1. The left of Figure 1 shows the large-area collapse phenomenon of the long-face working layer after the tundish is baked on the line for 100 minutes. The right of Figure 1 shows the initial collapse of the steel pouring. So, how to solve the problem of dry unshaped refractory material collapse in the tundish? Next, Rongsheng refractory manufacturer will find solutions by analyzing the problem of tundish working lining collapse.

Figure 1 The collapse of dry materials in the tundish

Tundish Working Lining Dry Monolithic Refractory Material

The working layer of the tundish is the basis for protecting the normal use of the tundish. The development of the working layer of the continuous casting tundish can be divided into 4 stages, no working layer stage, insulation board stage, coating or spraying stage, and dry monolithic refractory material stage.

Compared with the coating material, the dry working lining of the tundish has the advantages of convenient construction, high thermal efficiency, fast turnover of the tundish, long service life, good disintegration of the residual lining, and low energy consumption. It is widely used in the continuous casting tundish metallurgical industry. Magnesia materials have good corrosion resistance to high-speed iron and high-alkaline slag and have the characteristics of long service life and no pollution to molten steel. It has been gradually applied in tundish working lining refractories, with good use effect and application prospects. However, the thermal expansion coefficient of periclase is large and increases with the increase of temperature, which requires a relatively high on-line baking system. In the case of an imperfect baking system, large areas of collapse and partial peeling are prone to occur. The main reasons leading to the collapse of dry materials are low strength at medium temperature, large thermal expansion, and poor air permeability.

1.1 Reasons for construction

During the demolding of the working layer of the dry material in the tundish, if improper operation occurs, bumps or uneven application of the release agent will cause cracks in the dry material. The defects formed by these processes will form weaknesses in the baking process of the working layer, and in severe cases will lead to baking collapse.

After baking, the working layer of the tundish prepared for pouring steel usually forms an oxidative decarburization layer only on one side of the heating surface, which is very weak, and the back is a high-strength carbonized layer. The broken fragment in the collapsed packet is divided into three layers: the carbonized layer is sandwiched, and the backside also forms a decarburized layer due to oxidation, and two decarburized layers appear. The main reason is that the construction performance of dry materials is not good. Or the new permanent lining is constructed, and the bonding performance with the permanent lining is not good during the baking process. After the knot is intact, it will form a drumming phenomenon with a permanent lining. The on-site operation and construction level is not good, and the tundish turnover is tight and there is hot pack construction (permanent lining temperature exceeds 100 ℃). The uneven layout of the burner or the long baking time results in the hardening of the working lining in some positions. All of these will cause the working liner to separate from the drum, and the aforementioned sandwich layer will be formed during the in-line baking process, which will lead to the collapse of the package.

Figure 2 Schematic diagram of layering

1.2 The online baking system is not perfect

During the baking process of the tundish dry material working lining, as the temperature of the tundish increases, the phenolic resin gradually solidifies. The cured resin decomposes at 200°C to 800°C, releasing gas while leaving fixed carbon, that is, the resin is carbonized to form a carbon network structure. Although this amount of gas is not as large as the amount of water vapor produced by the paint, if the heating rate is fast and the binder decomposes too quickly, a large amount of gas will accumulate and expand. In addition, the dry material working lining is dense, and the vibration is relatively dense, which will cause the working layer to bake and collapse in severe cases.

Therefore, choose a binder with a relatively slow cracking rate and a high residual carbon content, and the amount of decomposed gas is as little as possible, which has a certain effect on reducing the risk of collapse. From the perspective of explosion-proof performance, the same principle as the castable is to introduce some fibers that can conduct air passages, or gently shake to reduce the density of the dry material, so that the gas generated by the cracking can be quickly discharged and the internal stress is relieved.

1.3 Low-temperature strength of dry materials

After the tundish dry material working layer is baked and de-moulded at low temperature, it needs to be hoisted to the pouring position to continue baking and heated to above 1100°C before it can be put into use. The sintering temperature of magnesia is high, there is no sintering at 750~1100℃. At this time, the bonding strength of the dry material working layer is at a relatively low stage. The low mid-temperature strength of the dry material working layer is an important reason for the collapse of the bag during baking.

1.4 The thermal linear expansion of dry material is relatively large

Affected by the thermal expansion and contraction factors, coupled with the thermal expansion of the magnesia itself, the dry material will expand when it is baked online to 1100°C. The release of the stress concentration will cause the bulging and the formation of cracks at the weak points, resulting in steel drilling or collapse of the ladle after pouring.

Baking collapse solution measures

2.1 Optimize construction and reduce off-drum

(1) Before construction, use a temperature measuring gun to measure the temperature of the permanent lining. Start construction when the permanent lining temperature is lower than 100°C (phenolic resin softening point 103~106°C).

(2) When baking at low temperature, turn off the heat when the thickness of the dry material changes to 1/3 of the total thickness. Avoid too long baking time to cause the working layer to deviate from the drum.

(3) When demolding, use a crane to lift the fetal membrane to the designated position. Pay attention to the uniform force when demolding, and do not damage the dry material lining to cause cracks.

2.2 Optimize the dry material plan and strengthen the medium temperature strength

When the sintering accelerator of magnesia dry ramming material is selected, the clay can form a liquid phase at medium temperature to promote sintering. But because it is composed of a variety of minerals and has no fixed melting point, it will also cause a large shrinkage of the green body. By adding boric acid and glass powder, the medium temperature strength of the dry material is obviously improved. Mainly because of its low melting point, it promotes the medium temperature sintering of the material.

The organic fiber is introduced into the brittle dry material, and the fiber is melted at a high temperature to produce micro-pores, which facilitates the discharge of the gas from the decomposition of the resin and enhances the air permeability of the lining. However, the amount of fiber added should not be too much, otherwise, the slag resistance performance is unfavorable.

2.3 Adjust the dry material formula to reduce thermal linear expansion

Phenolic resins are mainly decomposed in the range below 500°C. When the temperature exceeds 800°C, the difference in linear expansion rate caused by raw materials and sintering accelerators will begin to become obvious. At high temperatures, fused magnesia has a larger linear expansion than re-burned magnesia, and there are more pores and impurities in re-burned magnesia, which can absorb part of the expansion at high temperatures. The fused magnesia has larger crystal grains, fewer impurities, small pores, direct bonding at high temperatures, and greater linear expansion.

By optimizing the particle ratio and the selection of sintering agents, the thermal expansion of the dry material can also be reduced to a certain extent.

2.4 Permanent lining inclination and baking system

According to the decomposition characteristics of the phenolic resin and the low-temperature strength of the dry material, the low-temperature baking time during baking should be appropriately extended. Quickly pass the middle-temperature baking stage, make the dry material working layer reach the sintering state as soon as possible, and reduce the high fire to quickly bake.

For the tundish with a small inclination, especially the tundish with thinner working layer, deep, narrow, and long cladding. When designing permanent lining and working layer fetal membranes, it is necessary to consider appropriately increasing the inclination, so that the probability of collapse of the dry material will be greatly reduced. Save production costs.

In view of the smooth surface of the new permanent lining that is not easy to adhere to the dry material, it is considered to treat its surface into a hemp surface, which is also helpful to reduce the risk of collapse of the dry material.

What should I do if the refractory material cracks, falls off, and is easy to wear? To completely solve the problem, you need to dig from the root cause and analyze the real bugs. Rongsheng refractory material manufacturer ( http://www.aluminabricks.com/ ) has been engaged in refractory production, research, and development services for many years, and can solve various difficult problems of the high-temperature furnace lining.

Refractory Anchors the Skeleton of Refractory Castable Lining

The Refractory Anchor is a non-metal or metal component installed on the furnace shell or steel structure supporting the furnace lining and is embedded in the lining body for anchoring and connection. It is an important part of modern unshaped refractory linings and a key technical measure to improve the service life of linings. Especially it is used as the skeleton structure of refractory castable lining.

RS High-Quality Refractory Anchor Bricks

Classification of Refractory Anchors

Anchors are divided into two categories: metal anchors and non-metal anchors, including supports, thrusts, and anchor nails. Hanging bricks are also refractory anchoring bricks(http://www.aluminabricks.com/refractory-bric/anchor-brick/). The technical requirements for anchoring bricks are high strength and good thermal stability. Therefore, three-level clinker is generally used as the raw material and fired at high temperatures. For example, the chemical composition of high alumina anchor bricks in a factory is mainly A1203≥50% and Si02≥46%. Refractoriness is 1750℃, strength is 3.8MPa, 1200℃ linear expansion coefficient is 5.8X10-6K-1, 1450℃ returning linear change +0.1%, load softening starting temperature is 1430℃.

There are various shapes and connection methods of anchor bricks, and their sizes are also different. The most commonly used anchor bricks are 330, 380, 440, and 500mm in length, and the thickness is generally about 100mm. Mainly used for refractory castable lining. The shape without holes is generally used in the refractory plastic lining.

Metal anchors are generally made of ordinary steel, heat-resistant steel is the best, but it increases the cost of thermal equipment. Metal supports and thrusts are generally made of heat-resistant cast steel.

Metal anchors are easily oxidized at high temperatures, so they should be buried in the lining. The distance between the hot end and the working surface of the lining body and the thickness of the dependent body need to be determined according to the operating temperature, generally 20-200mm.

Metal anchors are generally welded to the furnace shell and have various shapes. The most commonly used ones are Y, V, and L shapes. There are also several shapes of support and thrust. The former is used in higher furnace walls and the latter is used in furnace roofs with steep slopes.

The installation holes or necks of the anchor bricks shall not have cracks and the dimensions shall be accurate. The welding between the metal anchor and the furnace shell should be fully welded, and there should be no false welding or missing places, and the size should be accurate. The ceramic anchors and metal anchors of the refractory fiber lining also have various shapes and sizes, and their function is mainly to fix the refractory fiber lining.

Masonry of Refractory Anchor Bricks

How to Build Refractory Anchor Bricks

The anchor brick is a special type of refractory brick that adopts the hanging form to support the structure of the furnace roof and furnace wall. It can also be called hanging bricks and anchors. The anchor bricks are used to prevent the leakage of reactive gas and hot gas in the furnace from damaging the metal hangers and causing the furnace roof to collapse.

Industrial kiln and flue walls are composed of the inner lining, heat insulation layer, and outer wall layer. The refractory bricks for the lining and the fired bricks for the outer wall need to be connected with anchor bricks. The anchor has high tensile and flexural strength, especially the stress generated at the groove is blocked at the rib and cannot be transmitted. Therefore, it is not easy to break when the anchor brick is used in this structure.

Hanging Anchor Bricks

Precautions for refractory anchoring brick masonry

1. When laying bricks, apply mortar carefully from both sides to prevent gas from leaking from the stovetop.

2. The hanging part of the anchor brick should not be damaged.

3. Ensure the size of the joints, accurately determine the position when laying on the top, and let the hanging metal parts play a private role.

4. Expansion joints should be properly left between the furnace body and the anchor bricks.

5. Air hardening mud should be used for laying anchor bricks.

6. The arrangement of anchoring bricks should be determined according to the range and frequency of temperature changes and the size of the direct wall area. Usually, 6 anchor bricks are used per square.

7. When the masonry is close to the anchor brick position, the lower row of bricks should be made in advance to determine the accurate position of the anchor brick. Use a wire brush to thoroughly clean the welding parts of the metal shell, and use welding rods that are compatible with the welding parts to firmly weld the anchor pipe.

8. After the anchoring brick is built, insert the anchoring hook. Fill the airstrike with refractory fiber felt and plug it tightly to form a certain degree of protection for the anchors.

9. The thickness of the anchorage hook has certain requirements. Not too thin, too thin will burn slowly and cause early damage to the lining. The heat-resistant steel material of the anchoring hook must be selected according to the national standard heat-resistant steel to meet the demand.

 Learn more about the refractory anchors, please contact us by email: info@aluminabricks.com.

Relevant Instructions on Refractory Bricks Masonry

Regarding the problem of refractory brick masonry, there are many conventional steps, these steps generally cannot be ignored in the process of refractory brick masonry. Because this affects the working conditions of the entire thermal kiln. For example, refractory mortar is required to be coated on refractory bricks built on boilers. So, what kind of mortar is generally used for chimney refractory brick masonry? Is it possible to use ordinary masonry mortar? Questions and answers about refractory brick masonry, the following will be a good answer.

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Masonry of Refractory Bricks in Cement Kiln

Initially, when people used vertical kilns to burn cement clinker, due to the small size of the kiln and the low calcination temperature, only a single clay brick containing 30-40% Al2O3 was used. The initial rotary kiln was improved on this experience and used high alumina bricks and clay bricks. Since the 1960s, due to the large-scale and enhanced operation of the kiln, the high-temperature kiln lining has generally been constructed with alkaline bricks. The main varieties are magnesia chrome brick, spinel brick, and dolomite brick.

The Role of Refractory Brick Lining for Cement Kiln

• 1. Prevent direct damage to the kiln body caused by high-temperature flame or air current, and protect the kiln body.
• 2. Prevent the erosion of the kiln body by harmful substances (CO, SO2);
• 3. Prevent the corrosion of materials and airflow to the kiln body;
• 4. Reduce the temperature of the kiln body to prevent the kiln body from being oxidized and corroded;
• 5. It has the function of heat storage and heat preservation;
• 6. It can improve the performance of kiln hanging.

Requirements for Masonry Mortar of Refractory Bricks for Chimneys

What kind of mortar is generally used for chimney refractory brick masonry? First of all, we must choose according to the material of refractory bricks. The manufacturer will provide matching products when purchasing refractory bricks. For specific information, you can consult the refractory brick manufacturer. Refractory selection recommendations, relevant technical guidance, and provide samples. Refractory manufacturers http://www.aluminabricks.com/ generally provide a full range of refractory services.

Can ordinary masonry mortar be used for construction? It is not recommended, because ordinary masonry mortar does not have acid resistance and corrosion resistance, which will affect the service life of chimneys and refractory bricks. In addition, acid-resistant cement or refractory cement is generally used, and it is divided into one-component and two-component. Acid-resistant cement used in rare cases.

Refractory Bricks Lining for the Rotary Kiln

Refractory bricks masonry method

1. Refractory brick-flat laying method

The flat-laying method is mostly used for the furnace wall, and a few are used for the bottom layer of the furnace bottom. In our country, the most common method of flat laying is the "one smooth and one top" brick wall. Annular bricklaying (like the wall of a blast furnace) is also flat laid.

2. Refractory bricks-side laying method

The side-laying method is mainly used in two parts. One is to pave the bottom of the bricklayer, such as the bottom of the open hearth and heating furnace. The second is side arches, such as open-hearth tapping arches.

3. Refractory bricks-vertical laying method

Vertical masonry, also called vertical masonry, is mainly used in two parts. One is the uppermost layer of the furnace bottom, such as the open hearth and blast furnace bottom. The second is the working layer of the furnace bottom, such as the open hearth.

Take the straight standard brick as an example. When laying flat, its largest plane is placed in a horizontal position. When laying on the side, the side (also called the middle, 230x65 mm) is placed in a horizontal position. When laying vertically, the small face is placed in a horizontal position.

Precautions for the Masonry of Refractory Bricks

The top of the refractory brick lining should be fully attached to the surface of the cylinder, and no cracks should be left. Thorough contact should be made between the large surfaces of adjacent single bricks. The width of the polished refractory brick shall not be less than 50% of the original brick, and the thickness shall not be less than 80% of the original brick. Iron hammers cannot be used during construction. Prevent the following phenomena from refractory bricks: inverted heads and sizes, lottery, mixing, dislocation, inclination, uneven ash joints. Climbing, de-centering, re-stitching, mouth opening, voiding, hairy seam, snaking, brick bulging, missing edges, few corners, etc. http://www.aluminabricks.com/refractory-related-products/refractory-mortar-for-sale/.

The Difference between Sintered AZS Brick and Fused Recombinded AZS Brick

Sintered AZS Brick

Sintered AZS brick is a product made of zircon and alumina as main raw materials and pre-synthetic materials as aggregates. Since the billet is a barren material, only relying on increasing the forming pressure to increase the density of the refractory brick is not good. The increased number of pressings of large products can also lead to the phenomenon of spalling and uneven density. Measures such as adjusting the critical particle size composition, adding a composite binder and a small amount of Ti02, MgO sintering aid and strengthening sintering are needed to achieve the purpose of dense sintering.

3AI₂O₃+2ZrSiO4 —> 3AI₂O₃·2SiO₂+2ZrO₂

The production principle is based on the solid phase reaction between ZrSiO₄ - AI₂O₃:

3AI₂O₃+2ZrSiO₄ —> 3AI₂O₃·2SiO₂+2ZrO₂

This reaction is irreversible and is also called "in-situ reaction". Due to the large volume effect produced during the reaction sintering process, which leads to deformation and cracks of the green body, only pre-synthesized zirconium mullite aggregates can be prepared with sintered or fused corundum raw materials to produce mullite, oblique zircon and corundum. The material is superior to two-phase materials in terms of strength and thermal shock resistance. The microstructure of sintered AZS bricks is mainly characterized by fine zirconia particles uniformly distributed between the main crystalline phases of mullite and corundum.

Sintered AZS bricks should have a relatively stable and uniform phase composition, to avoid long-term non-uniform interphase reactions under the action of high-temperature glass solutions, so that they can operate stably in high-temperature glass solutions for a long time. For this reason, in the sintered AZS brick, the performance indicators and crystal phase structure of the raw materials, the proportion of ingredients and the required particle size composition of the ingredients must be strictly controlled, so that the product can achieve more satisfactory performance indicators and phase structure.

Fused and Recombined AZS Bricks

Fused and recombined AZS bricks are based on melting and casting AZS clinker, scrap or recycled residual bricks (clearly adhered glass) as raw materials, adding a small amount of kaolin or alumina as a binder. When heated to a high temperature, the fused AZS aggregate seeps out of the glass phase and the binder to form mullite, which promotes the sintering of the product. The peritectic reaction of the glass phase and the crystal phase in the fused AZS aggregate will also form mullite. At this time, mullite and Zr02 are in the form of being wrapped and wrapped, which is helpful for the sintering of fused cast AZS particles of different grain sizes. Using this "white sinterability" of fused cast AZS aggregate is the basic principle of producing recombined AZS bricks.

The main changes in the microstructure of AZS bricks after firing at high temperature are:

1. The glass phase of the coarse-grained material exudes to the surface of the particles and reacts with A1203, forming a mullite shell to close the exudation channel, so that the peritectic reaction proceeds inside the particles.
2. The glass phase of fusion cast AZS powder material reacts with active A1203, and the matrix is mulliteized. Combined with the microstructure of AZS bricks, the eutectic structure of mullite and corundum oblique zircon is densely combined.
3. The dialysis of the glass phase in the coarse particles is exhausted, leaving voids and gaps.

Combining the product with the electric fusion product, the phenomenon of glass phase exudation is greatly reduced, and the exudation temperature is increased, with good thermal shock resistance and high high-temperature mechanical properties. Especially the creep resistance and the glass erosion resistance are also good.

Anchor Bricks for Steel Rolling Heating Furnaces

Anchor bricks are divided into hanging bricks and bricks with holes. The anchor bricks are fired at high temperatures, with high strength, good erosion resistance, and high spalling resistance. It is an ordinary sintered brick. The role of anchor bricks is to anchor the refractory castables on the top of the heating furnace. The industrial furnace or flue wall is roughly composed of an inner lining layer, a heat insulation layer, and an outer wall layer. The inner lining is refractory bricks and the outer wall anchor bricks.

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Anchor Bricks for Steel Rolling Heating Furnace

The alumina content of anchor bricks is more than 55%, and the alumina content of excellent anchor bricks can reach 75%. This kind of brick body has a soft load temperature of 1550°C, which is a high alumina refractory brick product. However, in general, the alumina content of 55% is more, because the 55% content of the anchor brick has better flexibility. In addition, it should be noted that anchor bricks are used to anchor refractory castables. The properties of anchor bricks should be consistent with the material of the castable, and the expansion and contraction should be consistent, so as to form a close combination with the castable and extend the life of the furnace lining.

Masonry of Anchor Bricks

The layout and masonry of anchor bricks during use should follow the following principles:

1. The arrangement of anchoring bricks should be determined according to the range and frequency of temperature changes and the size of the direct wall area. Usually, it should not be less than 6 blocks/m2.

2. The anchor bricks must be checked carefully before laying. If the anchor bricks have cracks at the anchor holes that affect the overall strength of the anchor bricks, they cannot be used and should be resolutely discarded.

3. When the masonry is close to the anchor brick position, bricks should be arranged in advance to determine the accurate position of the anchor brick. Use a wire brush to clean the welding part of the metal shell. Adopt the welding rod suitable for the welding parts, and weld the anchor pipe firmly.

4. After the anchoring brick is built, insert the anchoring hook, and fill the airstrike with refractory fiber felt, and plug it tightly. To form a certain degree of protection for the anchor.

The anchor brick includes a column composed of a hanging end and an anchor solid. Spaced partial grooves are opened on the surface of the anchor solid, and ribs are arranged along the length direction on at least one surface of the anchor solid. After the ribs are installed, due to the reinforcement and traction of the ribs, the tensile and flexural strength of the anchor solid is significantly improved, and the stress generated at the groove is blocked at the ribs and cannot be transmitted. Therefore, the anchor brick of this kind of structure is not easy to break.

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Rongsheng Anchor Bricks Manufacturer

Note: Many users have used hanging bricks with insufficient tensile strength, resulting in a serious imbalance of forces and a collapse of the furnace roof. Therefore, here is a reminder that you must carefully choose the anchor brick manufacturer. Rongsheng refractory material manufacturer is an experienced refractory material manufacturer and sales company. Rongsheng can provide anchoring bricks for rolling steel heating furnace, including high-aluminum anchoring bricks and hanging bricks. Get detailed product prices, product pictures, and other product introduction information of various anchor bricks. Please contact us, we will provide you with services according to your specific needs.

 

What are the Mixing Steps of Ladle Refractory Castable

Ladles are used in steelmaking plants and foundries to receive molten steel and carry outpouring operations before open-hearth, electric furnace or converter. 45% of the ladle castables are aluminum-magnesium spinel castables. The alumina-magnesia spinel castables for ladle are mainly used on large, medium, and small ladles. Ladle castable refers to a mixture of granular and powdery materials made of refractory materials and a certain amount of binder for a ladle. This product has a long service life, safety, and stability, and is an ideal refractory material for a ladle. Therefore, it needs to be stirred before the ladle castable is used. Next, Rongsheng monolithic refractory castable manufacturer will introduce the mixing steps of ladle refractory castable for you.

The Mixing Steps of Ladle Refractory Castable

As we all know, the construction process of ladle castables includes construction preparation, mixing, pouring, demolding, baking, etc. The mixing of ladle castables is a very critical step after construction preparation.

1. The mixing of ladle castables must be mixed with a forced mixer. When mixing, do not mix in packaging bags, rope ends, and other sundries, so as not to affect the pouring effect and performance.

2. The ladle castable used for mixing must be unpacked after arriving on site. The mixing capacity of the mixer should be determined according to the capacity of the mixer. The amount of castable used should be accurately measured before being poured into the mixer.

3. When mixing, the process of dry mixing first and then wet mixing is required. After the castable is added to the mixer, first dry mix for 2 minutes, then add about 5.2~5.5% of water, add water while stirring, first add 80% of the total. Then, add as appropriate depending on the consistency of the mixture, and note that the mixing water must be clean tap water, not sewage. Wet mixing for 4 minutes, one-time mixing should not be less than 6 minutes, until the castable is uniform. Discharge after the surface is flooded. Generally speaking, the bottom of the package is slightly dry and the wall of the package is slightly thinner. The above-mentioned water addition is a reference value.

4. When mixing, strictly control the water consumption and mixing time to ensure the consistency required for construction. If the castable is too thin, it will seriously affect the performance and quality of the material. The amount of mixing, mixing time, and the amount of water added each time are uniform and should not be thick and thin. If it is found that the consistency of the mixing material does not meet the requirements, it should be returned to the mixer to add water or dry material to mix properly. It is strictly forbidden to temporarily add water during pouring.

5. The evenly stirred material should be poured within 20 minutes. In order to avoid being hardened for a long time and cannot be poured, it will affect the structural strength of the ladle lining.

6. The mixer should be cleaned every time the construction is completed or the variety of castables is changed.

7. It is strictly forbidden to stop the mixing operation halfway and put the materials that have already started mixing in the mixer. If the mixer breaks down during work, if it can be repaired in a short time, you must clear a part of the material before turning on the machine before it can be turned on. Put this part of the material into it after starting up. If it cannot be repaired in time, all the castables in the machine must be cleaned.

The above is the mixing steps of refractory castable for a ladle. Hope to help you with your construction. We are a Rongsheng Alumina Bricks manufacturer. http://www.aluminabricks.com/. Our main products are various types of refractory bricks and monolithic refractory materials. If you want to know our company or want to buy refractory castables for ladle, please contact us. We will provide you with services according to your specific needs. 

 

 

How to Reserve Expansion Joints for Refractory Bricks and Castables?

When refractory bricks or castables are used in the refractory lining of industrial kilns, due to the influence of temperature changes and thermal stresses formed by temperature gradients, the lining structure will deform and expand. Therefore, expansion joints should be left during the construction of refractory bricks and castables.

The raw materials used in refractory bricks and castables are different, and the expansion coefficients produced after heating are also different. During masonry, the size of expansion is mainly determined by the nature of refractory bricks or castables and the temperature it withstands. 

Reserved Expansion Joints for Refractory Bricks in Rotary Kiln

The expansion of refractory brick and castable heating surface at the highest temperature is (unit: mm):

• Clay brick masonry: 5-6
• High alumina brick masonry: 7-8
• Corundum brick masonry: 9-10
• Silica brick masonry: 12-13
• Magnesia brick masonry: 10-14
• Clay castable masonry: 4-6
• Phosphorus salt castable: 5-8
• High alumina cement castable: 6-8
• Water glass castable: 4-6

Rules for reserved expansion joints

Clay bricks and lightweight brick masonry whose temperature is lower than 800°C do not need to leave expansion joints. However, expansion joints are still required for clay bricks with too long dimensions. The location of the expansion joint must avoid the stressed part. If there are holes in the furnace body frame and lining, the expansion joints should be separated and the spacing should not exceed 2m.

The expansion joints of refractory bricks or castables at the bottom of the furnace should be staggered in the upper and lower bricklayers and the furnace bottom of the same layer. When building the furnace wall, the left expansion joints can also be left in a staggered pattern between the inner and outer layers and in the upper and lower layers. When the circular wall is constructed, a gap should be left between the shells to compensate for expansion.

In the vault construction, the expansion joints of the refractory bricks and the castable should be left straight at both ends. Consider the vertical expansion of the vault and the upward expansion of the furnace wall when setting it aside. When the length of the dome is greater than 5 meters, in addition to leaving expansion joints at both ends, expansion joints must be set in the middle of the dome according to the segmentation of the arch length. The expansion joints of the staggering vault are left straight through.

The expansion joints of each layer of the multi-layer vault should be staggered, and the expansion joints should be covered with a layer of flat bricks. If it is a dome made of silica bricks, cardboard of 1-2mm should be inserted every 3-5 bricks in the radial joint of the dome to compensate for expansion.

If refractory bricks or castables are used for suspended furnace roofs, expansion joints should be left around the furnace roof.

Rongsheng refractory material manufacturer provides high-quality refractory brick lining and castable lining for various thermal furnace equipment. For detailed price information, please contact us, http://www.aluminabricks.com/contact-us/.