Method for producing high-quality casting refractory brick by adopting negative pressure shell mold process

Abstract

The invention discloses a method for producing a high-quality casting refractory brick by adopting a negative pressure shell mold process. The method comprises a shell mold processing procedure and a heat preservation casting procedure, the composite high-temperature-resistant coating is coated outside the EPS model, so that a shell mold with high strength and a good anti-burning sand effect can be obtained, and the smoothness of the outer surface of a casting refractory brick product is greatly improved; the EPS model is fed into the shell burning furnace to be heated twice, waste obtained after the EPS model is melted can be recycled, residual EPS in the shell mold can be gasified, slag is not left in an inner cavity of the shell mold, and the situation that corners and edges are lacked in a cast brick body is avoided; meanwhile, before casting, heat preservation materials are placed at the bottom and the periphery of the shell mold for effective heat preservation, the cooling speed of the refractory brick can be delayed after casting, cracks and deformation of the brick body caused by rapid cooling are effectively prevented, and the performance of the finished brick body is greatly improved; the negative pressure shell mold process can be used for producing the special-shaped casting refractory brick with a complex structure, and the actual production requirement is met.

Description

Technical Field

[0001] The invention relates to a fused-cast refractory material technology, in particular to a method for producing high-quality fused-cast refractory bricks by adopting a negative pressure shell mold process. Background Art

[0002] Fused refractory bricks are an important core material for building glass kilns. They are made by melting inorganic non-metallic high-temperature materials in an electric arc furnace, casting and forming, and then annealing. Since fused refractory bricks are hard and brittle, cracks and pores are easily generated during production. Therefore, it is very necessary to adopt effective insulation measures and control the cooling rate during the solidification and annealing of the melt. By slowing down the cooling rate during the solidification and annealing of the melt, the gas in the melt can be quickly discharged upward, and the crystals in the melt can grow fully to form coarse crystals, so that the brick body has a dense structure. When used in a glass kiln, it not only has high mechanical strength and high temperature strength, but also has good resistance to glass scouring and erosion, which prolongs the service life of the kiln; at the same time, effective insulation measures also help reduce the stress inside the brick body and prevent cracks and deformation caused by rapid cooling.

[0003] At present, there are five main molding processes used in the production of fused-cast refractory bricks: 1. Ordinary water glass sand mold process; 2. Modified water glass sand mold process; 3. Furan resin sand mold process; 4. V-method vacuum negative pressure empty mold molding process; 5. Negative pressure solid mold process.

[0004] The above five molding processes have their own advantages and disadvantages, but the best collapsibility is the V-method vacuum negative pressure air mold molding, followed by the furan resin sand mold, and the third is the modified water glass sand mold. Ordinary water glass sand mold technology has been gradually eliminated; the modified water glass sand mold has poor collapsibility and is prone to cracks and deformation; the furan resin sand mold has slightly better collapsibility, and the cracks will be reduced but not eliminated. The large amount of gas emission will cause pores in the product. At the same time, a large amount of unpleasant and harmful gases will be generated during the reaction of resin and curing agent, polluting the air and damaging the health of workers; the V-method vacuum negative pressure air mold molding is a molding technology that does not use binders and other additives, only uses sand, uses plastic film to seal, and then draws negative pressure. It has the advantages of low cost, precise size, and clear contours, but the use of this process in the casting refractory industry has just started, and there are many problems that need to be solved. The more prominent problem is that the insulation cannot be strengthened, resulting in poor quality of the bricks produced.

[0005] At present, there are three main measures to enhance insulation in the production of fused-cast refractory bricks: 1. Use annealing furnace to accurately control the temperature to achieve enhanced insulation, that is, after the brick body is cast and formed, when the outer shell is initially solidified, it is taken out and sent to the annealing furnace to achieve precise temperature annealing. Although this method has good effect, it is costly and difficult to operate; 2. Use hollow insulation balls to enhance insulation. Although this process has good effect, it cannot be used in the V-method vacuum negative pressure air molding process, because the use of alumina hollow balls used in the negative pressure process to enhance insulation will cause product deformation and local loss, causing the mold box to collapse; 3. Use insulation bricks or a combination of insulation bricks and hollow insulation balls to enhance insulation. This method is also not suitable for use in the V-method vacuum negative pressure air molding process, because the insulation bricks will hinder the air chamber from being exhausted, and the sand at the contact between the insulation bricks and the model is too little and has no strength, resulting in the collapse of the mold box.

[0006] Domestic V-method negative pressure molding technology can refer to the Chinese invention patent "Method for producing fused-cast refractory materials by negative pressure air mold" (patent number 200710055073.0, authorization announcement number CN 101143460 B) (referred to as patent 1) and the Chinese invention patent "Vacuum solid mold process for producing fused-cast refractory products" (patent number 201310325294.0, authorization announcement number CN103360095 B) (referred to as patent 2). However, during casting, the burning of the plastic film in patent 1 will produce a large amount of black smoke, which will not only pollute the environment, but also cause blackheads in the pores of the product; at the same time, due to the need for demolding, only simple castings can be produced, and castings with complex shapes cannot be produced; the models used in patent 2 are all disposable, and the burning will not only cause waste of model materials, but also produce a large amount of black smoke with a pungent smell during the burning. Moreover, whether it is burned first and then cast or burned while casting, the model cannot be fully and completely burned, and the slag remaining in the cavity will cause defects such as product scars or slag inclusions. Moreover, when melting and casting refractory bricks, if one wants to increase insulation measures, both methods have the defects of being difficult to operate and prone to box collapse.

[0007] China's invention patent "Short-process V-method Molding Technology" (2020105060377) (referred to as Patent 3) uses a 0.02mm thick high-pressure polyethylene film to replace the conventionally used EVA negative pressure casting film, which not only simplifies the molding process, but also eliminates the appearance of black smoke during casting, thereby protecting the environment and preventing the surface of the casting from blackening, thereby improving the yield of the casting. However, this molding method is still not suitable for the production of castings with complex shapes.

[0008] How to use the negative pressure shell mold process to produce high-quality fused-cast refractory bricks is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0009] The object of the present invention is to provide a method for producing high-quality fused-cast refractory bricks by using a negative pressure shell mold process.

[0010] To achieve the above purpose, the present invention can adopt the following technical solutions: The method for producing high-quality fused-cast refractory bricks by using a negative pressure shell mold process of the present invention comprises a shell mold processing step and a heat-insulating casting step; wherein The shell processing step comprises the following steps: S11, make a mold with a riser using flammable EPS material according to the product size and shape; S12, applying a high temperature resistant composite coating on the outer surface of the manufactured EPS model, with a coating thickness of 4-7 mm; S13, after the coating is dried (if it is mass production, it can be processed by drying equipment), the EPS model riser is placed downward on the tray of the trolley and pushed into the shell burning furnace for heating; S14, when the temperature in the shell burning furnace rises to 280-300℃, keep warm for 1h, the EPS model in the coating melts at high temperature and flows into the trolley tray, and the high temperature resistant coating forms a shell; S15, pull the trolley out of the shell burning furnace, recycle the EPS model waste in the tray, and then put the shell mold riser upward into the shell burning furnace again; because the melted EPS model waste solidifies when it is cold, it can be used again after recycling, thus avoiding the waste of model materials; S16, continue to heat the shell burning furnace until the temperature reaches 820℃±20℃, keep the temperature for 10~20min, and obtain a high-strength shell mold for standby use; the continuous high temperature can not only improve the shell mold strength but also promote the gasification of the residual EPS inside, ensuring that no residue is left in the shell mold; The heat preservation casting process comprises the following steps: S21, placing the processed high-strength shell mold on the sand box bottom plate that has been added with sand and compacted, placing thermal insulation materials on the bottom and around it, and then placing the sand box on the sand box bottom plate, adding sand and compacting it; S22, sealing the upper surface of the sand box with a film, connecting the vacuum tube on the sand box to an external vacuum device, vacuuming the sand mold to form a shell sand mold with a reinforced insulation layer; S23, maintaining the vacuum state, pouring the melted refractory liquid into the shell mold, releasing the vacuum after a few minutes (depending on the size of the finished brick body, it can be maintained for 1 to 20 minutes); after cooling for 8 to 20 days (depending on the size of the product), opening the sand box, and obtaining a fused-cast refractory brick with a riser.

[0011] After cutting off the riser, high-quality fused-cast refractory bricks can be obtained.

[0012] The present invention improves the shell mold processing and heat preservation casting processes at the same time, thereby improving the anti-corrosion quality of the fused-cast refractory bricks. Tests have shown that after this improvement, the fused-cast refractory bricks produced have a regular appearance, no cracks and deformations, and the quality can meet the erosion resistance and anti-corrosion performance of the glass kiln, greatly extending the service life of the glass kiln.

[0013] Since conventional shell mold coatings can ensure no sand sticking (or less sand sticking) when used for casting iron and steel castings at a casting temperature below 1600°C, sand sticking is very serious when casting fused-cast refractory bricks at 1870-1900°C; in order to improve the surface finish of the finished brick body, the high-temperature resistant coating applied to the outer surface of the EPS model in the shell mold processing step of the present invention is composed of a composite inner layer resistant to 1900°C and an outer layer resistant to 1600°C; The inner layer of the high temperature resistant coating has a thickness of 0.8~1mm and is made of 100 parts of aggregate, 4~7 parts of additives, 6~7 parts of binder and 50~60 parts of water; The aggregate includes 30 parts of 400-mesh zircon powder, 40 parts of 200-mesh magnesia powder, and 30 parts of 800-mesh quartz powder; The additives include 1-4 parts of 400 mesh talc and 3 parts of xanthan gum; The binder includes 6 to 7 parts of polyvinyl alcohol.

[0014] Due to the high strength of the coating material, the shell mold can meet the casting temperature of 1870-1900°C of the refractory brick, and the specially formulated inner coating of the present invention can effectively prevent sand sticking, so that the surface of the finished brick body is smooth and flat without cracks and deformation.

[0015] In order to obtain high-quality fused-cast refractory bricks, the present invention adopts effective insulation measures, that is, in the casting and insulation process, insulation materials such as insulation bricks, insulation balls or dry sand are placed at the bottom and around the high-strength shell; or the above insulation materials are combined.

[0016] Experiments have shown that the insulation material, which consists of an insulation brick layer placed close to the bottom and around the high-strength shell and a mixture of dry sand and / or insulation balls filled between the insulation brick layer and the sand box, has the best insulation effect.

[0017] The advantages of the present invention are that the V-method negative pressure method is used to produce high-quality fused-cast refractory bricks by means of an improved shell mold process and effective heat preservation measures; specifically: 1. The present invention can obtain a shell mold with high strength and good anti-sand sticking effect by brushing a composite high-temperature resistant coating on the outside of the EPS model - an inner layer resistant to high temperatures of 1900°C and an outer layer resistant to high temperatures of 1600°C, thereby greatly improving the smoothness of the outer surface of the fused-cast refractory brick product; the EPS model is sent into a shell burning furnace for heating twice, which can not only recycle the waste after the EPS model is melted, but also gasify the EPS remaining in the shell mold, so that no slag is left in the inner cavity of the shell mold, and the brick body after casting will not have missing corners or edges.

[0018] 2. Before casting, the present invention places insulation materials (insulation bricks are placed on the inner layer, and insulation balls and / or dry sand are filled on the outer layer) at the bottom and around the shell mold for effective insulation. After casting, the cooling rate of the refractory bricks can be slowed down, effectively preventing cracks and deformation of the brick body caused by rapid cooling, and greatly improving the performance of the finished brick body.

[0019] 3. The negative pressure shell mold process of the present invention can produce special-shaped fused-cast refractory bricks with complex structures, meeting actual production needs.

[0020] The experiment proves that compared with the short-process V-method molding process of Patent 3, the physical and chemical performance indicators of the finished refractory bricks of the present invention and the finished refractory bricks of Patent 3 are compared as follows: It can be seen from the test data that the physical and chemical performance indicators of the fused-cast refractory bricks produced by the present invention are better than those of the refractory bricks of Patent 3. When used in a glass kiln, the good effect of extending the service life of the kiln can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a brick structure diagram of Example 1 of the present invention (with a riser).

[0022] Figure 2 is in accordance with Figure 1 A brick model made of bricks and coated with a high-strength and high-temperature resistant coating.

[0023] Figure 3 It is a shell-shaped finished product obtained after the EPS material is melted.

[0024] Figure 4 Yes Figure 2 The brick body model is processed into a shell mold and placed in a sand box to form a shell sand mold.

[0025] Figure 5 The actual product of fused-cast refractory bricks (with risers) produced by the method of the present invention.

[0026] Figure 6 It is a brick body model coated with a high-strength and high-temperature resistant coating produced in Example 2 of the present invention.

[0027] Figure 7 Yes Figure 6 The brick body model is processed into a shell mold and placed in a sand box to form a shell sand mold.

[0028] Figure 8 It is a fused-cast refractory brick product that is cast in a shell mold by simply painting the outside of the EPS model with commercially available shell paint. DETAILED DESCRIPTION

[0029] The method of the present invention is described in more detail below in conjunction with a specific produced fused-cast refractory brick product to facilitate understanding by those skilled in the art.

[0030] The fused-cast refractory bricks produced by the present invention mainly involve the three most commonly used bricks at present: 1) fused-cast zirconium corundum AZS, the raw materials of which are: zircon sand, alumina and soda ash; 2) fused-cast electric-fused mullite bricks, the main raw materials of which are aluminum ore and zircon sand; 3) fused-cast chrome corundum bricks, the main raw materials of which are green chrome ore and magnesium spinel.

[0031] Obviously, this method can also be used for the production of other fused-cast refractory bricks.

[0032] According to the method of producing high-quality fused-cast refractory bricks by using a negative pressure shell mold process of the present invention, two coatings for painting the EPS model need to be prepared first: 1) Prepare the inner layer of high temperature resistant coating that can withstand 1900℃ high temperature: Based on 100kg aggregate (the proportion can be increased or decreased according to actual needs), the raw material formula is as follows: Aggregates include 30 kg of 400-mesh zircon powder, 40 kg of 200-mesh magnesia powder, and 30 kg of 800-mesh quartz powder; Additives include 400-mesh talc 1-4 kg, xanthan gum 3 kg; The binder includes 6-7 kg of polyvinyl alcohol; Water 50~60kg; When preparing, first pour cold water (temperature range is 20-30℃) into the container, gradually add cold water instant polyvinyl alcohol into the water, stirring while adding, until the cold water instant polyvinyl alcohol is completely dissolved in the cold water for standby use; Mix zircon powder, magnesia powder, quartz powder and talcum powder evenly, then add xanthan gum and polyvinyl alcohol solution and mix thoroughly to obtain the inner layer of high temperature resistant coating for use.

[0033] The present invention combines high melting point materials (zircon powder, magnesia powder, quartz powder) with a small amount of low melting point materials (talcum powder), and reasonably adjusts the particle sizes of each material to achieve the effect of resisting the impact of high temperature melt at 1800-1900°C.

[0034] It should be noted that the role of talcum powder is to promote sintering, and its dosage must be strictly controlled. If the dosage is too large, it will affect the sintering of the coating, resulting in the inner layer of coating being difficult to peel off from the brick body after casting.

[0035] 2) Prepare the outer coating. You can purchase commercially available shell coatings (such as the casting-specific empty shell coatings produced by Henan Tianjuyuan New Materials Technology Co., Ltd.).

[0036] Shell burning furnace: 500KW desktop shell burning furnace can be used.

[0037] The present invention is described in more detail below by taking the production of the most conventional rectangular fused-cast refractory bricks as an example.

[0038] Example 1 A relatively conventional rectangular brick is produced, wherein the brick body Z (dimensions 250×400×1100) (length unit mm), wherein the size of the upper riser M is 400×500×600 (length unit mm), such as Figure 1 .

[0039] When producing the above-mentioned fused-cast refractory bricks according to the method of the present invention, the shell mold is first processed, and the specific steps are as follows: The first step is to follow Figure 1 According to the product size and shape, the model with riser is made of flammable EPS material; The second step is to apply the high temperature resistant coating on the outer surface of the finished EPS model in sequence: first, apply the prepared inner layer coating to make the coating thickness reach 0.8-1mm (when applying, it needs to be dried after one application before applying the next application); after the inner layer coating is applied and dried, apply the commercially available outer layer coating in the same way as the inner layer, so that the outer layer coating thickness reaches 4-6mm, and a brick model with a high-strength and high temperature resistant composite coating is obtained, such as Figure 2 As shown; If it is urgent or for continuous production, the coating can be dried at 35-45℃ in a drying equipment after it is applied. Note: When applying the high temperature resistant composite coating, the top surface of the EPS model riser should not be coated.

[0040] Step 3: After the outer coating is completely dried, place the EPS model with the riser facing downward (or tilted downward) on the tray of the trolley, push the trolley (with the tray and model) into the shell burning furnace, close the furnace door, and start heating; The fourth step is to wait for the temperature in the shell burning furnace to rise to 280-300℃ and keep it warm for 1 hour. At this time, the EPS model in the coating melts at high temperature, forming liquid that flows into the trolley tray, and the high temperature resistant coating forms a shell shape; The fifth step is to pull the trolley tray out of the shell burning furnace. The model liquid in the tray is solidified when it is cold, and the waste formed is recycled and utilized, thus avoiding the burning and waste of model materials. Then, the shell mold is put back into the shell burning furnace with the riser facing upward (or tilted upward). Step 6: Continue to heat the shell burning furnace until the temperature reaches about 820°C, and keep it warm for 10-20 minutes to gasify the EPS material remaining inside the shell mold, ensuring that no residue is left in the shell mold. At the same time, the continuous high temperature can make the shell mold stronger. Then lower the shell burning furnace temperature, pull out the trolley tray, and let it dry to room temperature to obtain a high-strength shell mold A1, as shown in the figure. Figure 3 .

[0041] The finished shell has no defects in appearance and will not rot or break when transported in the conventional manner.

[0042] After the shell mold is made, the next step of heat preservation casting process can be carried out. The specific steps include: The first step is to place the processed high-strength shell A1 on the sand-added and vibrated sandbox bottom plate A2, and place two layers of insulation bricks A3 on the bottom and around the shell A1 (M-06 mullite insulation bricks are used and laid neatly, and the two layers of bricks are staggered so that the total thickness of the insulation brick layer is about 230 mm). In order to prevent the insulation brick layer from tipping over, plastic film can be used to fix it after it is placed; then place the sandbox A4 on the sandbox bottom plate A2, add dry sand A5 into the sandbox A4 and vibrate it; In the second step, the film A6 is covered to seal the upper surface of the sand box A4, and the vacuum tube A7 on the sand box is connected to the external vacuum device to vacuumize the sand mold to obtain a shell sand mold with a reinforced insulation layer, such as Figure 4 ; The third step is to maintain a vacuum state (vacuum degree 0.05-0.09), pour the melted refractory material into the shell cavity A8, and release the vacuum for about 5 minutes; after cooling for 8-10 days, open the sand box to obtain a fused-cast refractory brick with a riser, such as Figure 5 shown.

[0043] After cutting off the riser, high-quality fused-cast refractory bricks can be obtained.

[0044] Note: After casting, the vacuum state cannot be maintained for a long time, otherwise the heat will be lost quickly and cause cracks in the brick body.

[0045] Example 2 Production of complex-shaped fused zirconium corundum fused-cast refractory bricks The specific steps for processing the shell mold are the same as those in Example 1: First, process the brick body model with a high-strength and high-temperature resistant coating, such as Figure 6As shown (due to the complexity of the brick shape, the inner layer of the EPS model needs to be painted multiple times to make the coating thickness reach 1mm, and the thickness of the outer layer of the coating needs to reach 6mm; then it is placed in a shell burning furnace and fired into a high-strength shell mold according to the method of Example 1. The finished shell mold after firing has no defects in appearance and is not rotten or damaged when transported in a conventional manner.

[0046] After the shell mold is made, casting and heat preservation are carried out. The specific steps include: The first step is to place the processed high-strength shell B1 on the sand-added and vibrated sandbox bottom plate B2, and place two layers of insulation bricks B3 on the bottom and around it (M-06 mullite insulation bricks are used and laid neatly, and the two layers of bricks are staggered so that the total thickness of the insulation brick layer is about 230mm). Due to the complex brick structure, in order to prevent the insulation brick layer from tipping over, it needs to be fixed with plastic film after placement; then place the sandbox B4 on the sandbox bottom plate B2, add dry sand B5 (or insulation balls, or dry sand and insulation balls can be mixed and added) into the sandbox B4 and vibrate it; The second step is to cover the film B6 to seal the upper surface of the sand box, connect the vacuum tube B7 on the sand box to the external vacuum device, and then vacuumize the sand mold to fix the sand mold, so as to obtain a shell sand mold with a reinforced insulation layer, such as Figure 7 ; The third step is to cast according to the method of Example 1, and open the sand box after cooling to obtain a fused-cast refractory brick product with a complex structure and a specific purpose and with a riser.

[0047] The riser will be cut off during use.

[0048] Comparative Example: In contrast, the applicant only used commercially available shell coating to paint the outside of the EPS model of another product, and cast the shell mold after obtaining it according to the same method as the present invention. The surface of the finished brick body was seriously sanded, such as Figure 8 , proving that the existing shell coatings cannot meet the production of fused-cast refractory bricks with a casting temperature of 1850-1900°C; the present invention first applies a high-temperature resistant inner layer to the outside of the EPS model and then applies a high-temperature resistant outer layer. Since the inner layer coating has a good anti-sand sticking effect, the surface of the brick body obtained by casting is free of sand sticking and is smooth and flat. Figure 5 .

Claims

1. A method for producing high-quality fused-cast refractory bricks using a negative pressure shell mold process, characterized in that: It includes shell mold processing process and heat preservation casting process; The shell processing step comprises the following steps: S11, make a mold with a riser using flammable EPS material according to the product size and shape; S12, applying a high temperature resistant composite coating on the outer surface of the manufactured EPS model, with a coating thickness of 4-7 mm; S13, after the coating is dried, the EPS model riser is placed downward on the tray of the trolley and pushed into the shell burning furnace for heating; S14, when the temperature in the shell burning furnace rises to 280-300℃, keep warm for 1h, the EPS model in the coating melts at high temperature and flows into the trolley tray, and the high temperature resistant coating forms a shell; S15, pull the trolley out of the shell burning furnace, recycle the EPS model waste in the tray, and then put the shell mold riser upward into the shell burning furnace again; S16, continue to heat the shell burning furnace until the temperature reaches 820℃±20℃, keep it warm for 10~20min, and obtain a high-strength shell mold for standby use; The heat preservation casting process comprises the following steps: S21, placing the processed high-strength shell mold on the sand box bottom plate that has been added with sand and compacted, placing thermal insulation materials on the bottom and around it, and then placing the sand box on the sand box bottom plate, adding sand and compacting it; S22, sealing the upper surface of the sand box with a film, connecting the vacuum tube on the sand box to an external vacuum device, vacuuming the sand mold to form a shell sand mold with a reinforced insulation layer; S23, maintaining the vacuum state, pouring the melted refractory liquid into the shell mold, and releasing the vacuum after a few minutes; opening the sand box after cooling for 8 to 20 days to obtain the fused-cast refractory bricks with risers.

2. The method for producing high-quality fused-cast refractory bricks using a negative pressure shell mold process according to claim 1, characterized in that: The high temperature resistant composite coating applied to the outer surface of the EPS model in the shell processing step is composed of an inner layer resistant to high temperatures of 1900°C and an outer layer resistant to high temperatures of 1600°C. The thickness of the inner layer of the high temperature resistant coating is 0.8-1 mm, and it is prepared from 100 parts of aggregate, 4-7 parts of additives, 6-7 parts of binder and 50-60 parts of water; The aggregate includes 30 parts of 400-mesh zircon powder, 40 parts of 200-mesh magnesia powder, and 30 parts of 800-mesh quartz powder; The additives include 1-4 parts of 400 mesh talc and 3 parts of xanthan gum; The binder includes 6 to 7 parts of polyvinyl alcohol.

3. The method for producing high-quality fused-cast refractory bricks using a negative pressure shell mold process according to claim 1, characterized in that: The insulation materials placed at the bottom and around the high-strength shell mold in the insulation casting process include insulation bricks, insulation balls or dry sand; Or the above insulation materials can be used in combination.

4. The method for producing high-quality fused-cast refractory bricks using a negative pressure shell mold process according to claim 3, characterized in that: The heat-insulating material consists of a heat-insulating brick layer placed close to the bottom and around the high-strength shell mold and a dry sand and / or heat-insulating ball mixture filled between the heat-insulating brick layer and the sand box.

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