A coating for dip tubes and a method of making the same

Abstract

The present invention discloses a coating material for an impregnated pipe and a preparation method thereof, comprising the following raw materials in parts by weight: 60-75 parts of 88 alumina, 5-10 parts of aluminum oxide powder, 1-3 parts of microsilica powder, 1-2 parts of chromium oxide green, 1-5 parts of bentonite, 1-9 parts of tertiary clay, 3-10 parts of Guangxi white mud, 0-1 parts of high-viscosity cellulose, 4-7 parts of solid aluminum dihydrogen phosphate, and ≤1 part of explosion-proof fiber. The coating material comprises the following preparation steps: (1) weighing the above raw materials in parts by weight and placing them in a blender; (2) dry-mixing the raw materials and adding water to mix them; (3) placing the mixed mud material in a sealed bag or a sealed barrel and trapping it at 16-25°C for more than 8 hours; (4) taking it out for use and baking it to improve its strength. Compared with most existing semi-dry gunning materials for RH impregnated pipes, the present invention has a larger limit particle size, stronger anti-scouring and anti-erosion capabilities, and can reduce the consumption of refractory materials.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and more particularly to a coating material for an impregnated pipe and a preparation method thereof. Background Art

[0002] RH vacuum degassing refining is currently a key process for molten steel refining. During production, an ascending and descending dip tube are immersed in molten steel. Argon gas is blown into the ascending tube through an argon pipe inside the ascending tube, driving the molten steel into the lower trough. After degassing in the near-vacuum RH furnace, the molten steel returns to the ladle through the downcomer. Some steel mills also perform alloying, oxygen blowing, and desulfurization. The reciprocating flow of the molten steel within the vacuum chamber achieves the refining goals of degassing, decarburization, desulfurization, and improving purity.

[0003] Because the immersion tube contains numerous metal components, it remains immersed in the molten steel during the refining process. Prolonged immersion in high-temperature molten steel causes the components to heat up and expand, exerting significant stress on the castable material within the tube, causing numerous cracks. Prolonged contact between slag and the castable at the slag line accelerates the melting of the castable material at the cracks, posing a risk of molten steel melting and damaging the metal components.

[0004] Currently, crack repairs are performed using gunning compound, a semi-dry method that requires skilled operators to operate the gunning equipment and adjust the air-water ratio to effectively maintain the immersion pipe. For construction teams with unstable personnel and varying operational skills, encountering wider or deeper cracks presents the risk of the immersion pipe failing to be effectively repaired quickly, leading to steel failure and loss of production. Using smearing compound to repair severe immersion pipe defects can improve operational efficiency for both refractory manufacturers and steel mills, mitigating the challenges of uneven gunning personnel skills.

[0005] Chinese patent CN101550016B discloses a "magnesia-chromium-carbon coating and its preparation method." The coating is produced from recycled magnesia-carbon bricks and can be used to repair the working lining of the lower tank of a RH furnace. The carbon content in the recycled magnesia-carbon material is 10%-40% of the recycled magnesia-carbon brick particles. First, under vacuum conditions, the presence of carbon reacts with MgO to produce Mg vapor, making the structure loose and susceptible to erosion by hot flue gases. Second, the recycled magnesia-carbon bricks are washed off and released into the molten steel, causing carbon enrichment in the molten steel and potentially contaminating ultra-low carbon molten steel.

[0006] Chinese patent document CN104230351B discloses "a chromium-free magnesia-alumina spinel brick repair material for RH furnaces," which uses periclase, sintered magnesia, magnesium chloride hexahydrate, and a coagulant as raw materials. After construction, it needs to be left to stand for 24 hours before being baked according to the magnesia-alumina spinel brick curve to complete the repair. Given the tight production rhythm, this solution is difficult to meet the production needs of steel mills.

[0007] Therefore, it is an urgent problem for technical personnel in this field to study the use of coatings to maintain key defective parts of the immersion pipe, thereby providing a coating for the immersion pipe and a preparation method thereof, and being able to improve the service life of the immersion pipe and the production efficiency of the steel plant. Summary of the Invention

[0008] In view of this, the present invention provides a coating material for an immersion tube and a preparation method thereof, which is used to fill wider cracks or small-scale material loss and exposed structural parts on the immersion tube, thereby increasing the service life of the immersion tube and improving the refining efficiency of the steel plant.

[0009] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a coating material for impregnated pipes, comprising the following raw materials in parts by weight: 60-75 parts of 88 alumina, 5-10 parts of alumina powder, 1-3 parts of microsilica powder, 1-2 parts of chromium oxide green, 1-5 parts of bentonite, 1-9 parts of third-grade clay, 3-10 parts of Guangxi white mud, 4-7 parts of solid aluminum dihydrogen phosphate, and explosion-proof fiber ≤1 part.

[0010] The above technical solution has the following advantages: first, it can overcome the problem of high turnover and uneven skill levels of gunning personnel, and is particularly beneficial for repairing cracks on the outer wall of immersion pipes. It can be used after the material is trapped, which is beneficial for short-term repair requirements. It does not require air or water sources, and is easy to operate.

[0011] Preferably, the raw material further comprises 0-1 part of high-viscosity cellulose.

[0012] The beneficial effects of the above technical solution are as follows: high-viscosity cellulose is a macromolecular chemical substance with strong hygroscopicity. It is soluble in water and forms a viscous solution with high transparency. Its aqueous solution has a certain viscosity and is heat-stable, with the viscosity increasing rapidly below 20°C. The addition of high-viscosity cellulose can increase the viscosity of the coating at room temperature, facilitating application.

[0013] Preferably, among the 88 alumina, 3-5 mm 88 alumina accounts for 10-16%; 1-3 mm 88 alumina accounts for 20-30%; 0.08-1 mm 88 alumina accounts for 20-30%; and 0.06-0.074 mm 88 alumina accounts for 30-45%.

[0014] The beneficial effects of the above technical solution are as follows: the basic particle size of the current coating materials is mostly concentrated in the range of 0-3mm, while the coating material of the present invention adjusts the maximum particle size to 3-5mm, reducing the overall specific surface area of ​​the granular material, making the matrix (fine powder) layer thinner, and reducing the erosion of the matrix part by molten steel and slag; and the current erosion of refractory materials is mainly caused by the reaction of molten steel or slag with the matrix part, which destroys the internal strength of the refractory material, thereby causing the granular material to fall off and reducing the service life of the refractory material. In addition, the existing coating material has a large proportion of powder and larger aggregate particles, which is conducive to the formation of bridges between particles and improves the structural stress of the refractory material.

[0015] The chemical indicators of the preferred main raw materials such as bauxite, aluminum oxide powder, bentonite, tertiary clay, Guangxi white mud, chromium oxide green, etc. are as follows:

[0016] 88 bauxite Al2O3 content ≥88%;

[0017] Alumina powder Al2O3 content ≥99%;

[0018] Bentonite SiO2 content ≥ 62%;

[0019] Guangxi white mud SiO2 content ≥48%;

[0020] The SiO2 content of the third-grade clay is ≥62%;

[0021] Chromium oxide green Cr2O3 content ≥99%.

[0022] A method for preparing a coating material for an impregnated pipe comprises the following steps:

[0023] (1) Weighing the raw materials by weight and placing them in a blender;

[0024] (2) dry-mixing the raw materials and then adding water to mix;

[0025] (3) The mixed mud material is placed in a sealed bag or a sealed barrel and sealed for more than 8 hours to obtain the coating material for the impregnated pipe.

[0026] Preferably, the dry mixing time in step (2) is 1-2 minutes, the water is added in an amount of 10-20 parts by weight, and the net mixing time after adding water is 2-4 minutes.

[0027] The beneficial effect of the above technical solution is that dry mixing for 1-2 minutes is conducive to the powder being fully stirred and evenly combined with water in the mill, so that a more uniform mud can be obtained.

[0028] Preferably, the entrainment in step (3) is carried out at an environment of 16-25°C.

[0029] The beneficial effect of the above technical solution is that it can lock moisture at a lower temperature and extend the construction time of the coating.

[0030] Preferably, the preparation method of the present invention further comprises step (4) of taking out the spread described in step (3) and baking it to enhance its strength.

[0031] The beneficial effect of the above technical solution is that the low-temperature section coating material uses water as a binder and is baked after coating, which is conducive to the coating material quickly crossing the low-temperature section and converting into orthophosphate bonding, thereby improving the strength of the coating material and preventing material shedding.

[0032] Preferably, the coating material in step (4) does not need to be cured after maintenance, and the baking curve can be consistent with the on-site baking curve of the steel plant.

[0033] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a coating material for impregnated pipes and a preparation method thereof, and the beneficial effects of the present invention are:

[0034] (1) Compared with most existing RH immersion tube semi-dry gunning materials, the present invention has a larger limit particle size, stronger anti-scouring and anti-erosion capabilities, and can reduce the consumption of refractory materials;

[0035] (2) Compared with the existing RH impregnation pipe maintenance bulk material operation, the present invention is simple, the trapped material can be pre-mixed in advance for standby use, and there is no need to connect the air duct and water pipe before the semi-dry method. The work efficiency is higher and the requirements on the operating level of the personnel are low. DETAILED DESCRIPTION

[0036] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0037] Example 1

[0038] A dip tube coating is prepared from the following raw materials in parts by weight:

[0039] 68.8 parts of 88 alumina, 8 parts of alumina powder, 3 parts of microsilica fume, 1 part of chromium oxide green, 3 parts of bentonite, 5 parts of tertiary clay, 7 parts of Guangxi white mud, 0.1 part of high-viscosity cellulose, 4 parts of solid aluminum dioxide phosphate, and 0.1 part of explosion-proof fiber;

[0040] Among 88 bauxite, 3-5mm 88 bauxite accounts for 15.3% of the total 88 bauxite, 1-3mm 88 bauxite accounts for 27.6% of the total 88 bauxite, 0.08-1mm 88 bauxite accounts for 24.7% of the total 88 bauxite, and 0.06-0.074mm 88 bauxite accounts for 32.4% of the total 88 bauxite;

[0041] The preparation method of the above-mentioned dip tube coating material comprises the following preparation steps:

[0042] (1) Take the above raw materials in parts by weight and add them into a blender;

[0043] (2) After dry mixing for 1 minute, 17 parts of water were added and then mixed for 3 minutes;

[0044] (3) After the mud material is mixed into a soft plasticine-like state, it is put into a plastic bucket and placed in a room at 18° C. for 12 hours to obtain the coating material for the impregnated pipe;

[0045] (4) Take out and use, apply the mud to the interface between the bottom brick of the immersion pipe and the castable. After applying, hang the RH furnace into the baking position and bake it for use.

[0046] Performance test: The coating material for the dip tube was prepared according to the raw material ratio of the above embodiment 1 and applied to the 180tRH refining furnace of a steel plant in Liaoning Province. The use effect was good. The coating material at the interface between the bottom brick of the dip tube and the castable can be used for about 5-10 furnaces, which extends the service life of the bottom castable.

[0047] Example 2

[0048] 65.8 parts of 88 alumina, 7 parts of alumina powder, 2 parts of microsilica fume, 1 part of chromium oxide green, 5 parts of bentonite, 5 parts of tertiary clay, 10 parts of Guangxi white mud, 0.1 part of high-viscosity cellulose, 4 parts of solid aluminum dioxide phosphate, and 0.1 part of explosion-proof fiber;

[0049] Among the 88 bauxite, 3-5mm 88 bauxite accounts for 12% of the total bauxite, 1-3mm 88 bauxite accounts for 22.5% of the total bauxite, 0.08-1mm 88 bauxite accounts for 22.5% of the total bauxite, and 0.06-0.074mm 88 bauxite accounts for 43% of the total bauxite;

[0050] The preparation method of the above-mentioned dip tube coating material comprises the following preparation steps:

[0051] (1) Take the above raw materials in parts by weight and add them into a blender;

[0052] (2) After dry mixing for 1 minute, 15 parts of water were added and then mixed for 3 minutes;

[0053] (3) After the mud material is mixed into a soft plasticine-like state, it is put into a plastic bucket and placed in a room at 18° C. for 12 hours to obtain the coating material for the impregnated pipe;

[0054] (4) Take it out for use. After the immersion pipe is broken, apply the mud to the wider cracks on the blackened surface of the outer wall casting of the immersion pipe. After the repair is completed, bake it over a high fire.

[0055] Performance test: The coating material for impregnated pipes was prepared according to the raw material ratio of the above embodiment 2, and applied to a 210tRH refining furnace of a steel plant in Guangxi. The actual use effect was good, and the wider cracks in the impregnated pipe body were effectively repaired. The average amount of gunning material used for each pair of pipes was reduced by 2-5t, and the defective parts could be effectively maintained for more than 4 furnaces, which solved the problem of uneven skills of on-site personnel and low maintenance level, and improved the service life of refractory materials.

[0056] Example 3

[0057] 68.8 parts of 88 alumina, 7 parts of alumina powder, 2 parts of microsilica fume, 1 part of chromium oxide green, 4 parts of bentonite, 5 parts of tertiary clay, 7 parts of Guangxi white mud, 0.1 part of high-viscosity cellulose, 5 parts of solid aluminum dioxide phosphate, and 0.1 part of explosion-proof fiber;

[0058] Among the 88 bauxite, 3-5mm 88 bauxite accounts for 14.5% of the total bauxite, 1-3mm 88 bauxite accounts for 22% of the total bauxite, 0.08-1mm 88 bauxite accounts for 22% of the total bauxite, and 0.06-0.074mm 88 bauxite accounts for 41.5% of the total bauxite;

[0059] The preparation method of the above-mentioned dip tube coating material comprises the following preparation steps:

[0060] (1) Take the above raw materials in parts by weight and add them into a blender;

[0061] (2) After dry mixing for 1 minute, 19.5 parts of water were added and then mixed for 3 minutes;

[0062] (3) After the mud material is mixed into a soft plasticine-like state, it is put into a plastic bucket and placed in a room at 18° C. for 12 hours to obtain the coating material for the impregnated pipe;

[0063] (4) Take it out for use. After the immersion pipe is adjusted to the standby position, apply the mud to the small area of ​​exposed steel on the surface of the immersion pipe. Use the smear to fill the cracks until the surface of the castable is flat or convex, then bake it over high heat. It can be used after baking for 5 hours.

[0064] Performance test: The coating material for the impregnated pipe was prepared according to the raw material ratio of the above embodiment 3 and applied to the 180tRH refining furnace of a steel plant in Liaoning Province. The actual application effect was good, so that the impregnated pipe with a small area of ​​exposed steel liner could continue to be used normally, thereby improving the service life of the refractory material.

[0065] Example 4

[0066] A dip tube coating is prepared from the following raw materials in parts by weight:

[0067] 67 parts of 88 bauxite, 8 parts of alumina powder, 2 parts of microsilica fume, 1 part of chromium oxide green, 3 parts of bentonite, 7.9 parts of tertiary clay, 6 parts of Guangxi white mud, 5 parts of solid aluminum dioxide phosphate, and 0.1 part of explosion-proof fiber;

[0068] Among the 88 bauxite, 3-5mm 88 bauxite accounts for 12% of the total bauxite, 1-3mm 88 bauxite accounts for 23% of the total bauxite, 0.08-1mm 88 bauxite accounts for 28% of the total bauxite, and 0.06-0.074mm 88 bauxite accounts for 37% of the total bauxite;

[0069] The preparation method of the above-mentioned dip tube coating material comprises the following preparation steps:

[0070] (1) Take the above raw materials in parts by weight and add them into a blender;

[0071] (2) After dry mixing for 1 minute, 18 parts of water were added and then mixed for 4 minutes;

[0072] (3) After the mud material is mixed into a soft plasticine-like state, it is put into a plastic bucket and placed in a room at 16° C. for 8 hours to obtain the coating material for the impregnated pipe;

[0073] (4) Take out and use, apply the mud to the cracks on the outer layer of the bottom of the immersion pipe, and bake the immersion pipe with fire after the application is completed.

[0074] Performance test: The coating material for the dip tube was prepared according to the raw material ratio of the above embodiment 4 and applied to a 180tRH refining furnace of a steel plant in Liaoning Province. The coating material was scraped to the cracks on the side wall of the dip tube and then shallowly treated with 4 furnaces of molten steel. The residual amount of the coating material in the dip tube was about 40-50%.

[0075] Comparative Example 1

[0076] The preparation method is the same as that of Example 1, except that 4% 70 cement is used instead of solid aluminum dihydrogen phosphate.

[0077] Comparative Example 2

[0078] The preparation method is the same as that of Example 1, except that no tertiary clay is added and the bentonite content is 8%.

[0079] The results of laboratory sample testing are shown in Table 1

[0080] Table 1

[0081]

[0082] The experimental results show that in Comparative Example 1, aluminum dihydrogen phosphate is not used as a binder, but cement is used as a binder (added in an amount of 5%-8%). First, the coating material will harden in a relatively short period of time (<2h), and it needs to be mixed before each use, which cannot achieve the effect of "ready to use and take it immediately". Compared with the gunning material, it does not have the advantage of shortening the maintenance time. In Example 1, aluminum dihydrogen phosphate is used as a binder. After mixing, the material can be stored for a period of time (sealed and stored indoors at 18℃-20℃, and can be used normally within 7 days); secondly, cement coating materials need a certain amount of time to cure and then bake to allow the cement to hydrate and produce bonding strength. If it is baked immediately after coating, it will not produce sufficient strength and the material will fall off. The present invention uses orthophosphate as a binder and adds low-melting materials such as clay and bentonite to ensure the strength of the coating material in the medium temperature section, and the adhesion viscosity in the low temperature section can also ensure normal construction.

[0083] In comparative example 2, the situation where no tertiary clay is added has a greater impact on the construction performance of the coating. After adding clay, the mud material is mixed with water, the adhesion of the coating is enhanced, the plasticity is reduced, the coating thickness is reduced, but the construction performance is better; in the solution of replacing clay with bentonite, the adhesion of the coating is reduced, the plasticity is enhanced, the coating thickness is increased, and it is not easy to stick during construction.

[0084] Compared with most existing RH immersion pipe semi-dry gunning materials, the coating material for the immersion pipe of the present invention has a larger limit particle size, stronger anti-scouring and erosion resistance, and can reduce the consumption of refractory materials; and compared with the existing RH immersion pipe maintenance bulk material operation, the present invention is simple to operate, and the trapped material can be pre-mixed in advance for standby use. There is no need to connect air ducts and water pipes before semi-dry gunning, so the work efficiency is higher and the requirements on the operating level of personnel are low.

[0085] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0086] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A coating material for dipping pipes, characterized in that: The invention comprises the following raw materials in parts by weight: 60-75 parts of 88 alumina, 5-10 parts of alumina powder, 1-3 parts of microsilica powder, 1-2 parts of chromium oxide green, 1-5 parts of bentonite, 1-9 parts of third-grade clay, 3-10 parts of Guangxi white mud, 4-7 parts of solid aluminum dihydrogen phosphate, and explosion-proof fiber ≤1 part.

2. The coating material for dipping pipe according to claim 1, characterized in that The raw materials also include 0-1 part of high-viscosity cellulose.

3. The coating material for dipping pipe according to claim 1, characterized in that Among the 88 alumina, 3-5 mm 88 alumina accounts for 10-16%; 1-3 mm 88 alumina accounts for 20-30%; 0.08-1 mm 88 alumina accounts for 20-30%; and 0.06-0.074 mm 88 alumina accounts for 30-45%.

4. The coating material for dipping pipe according to claim 1, characterized in that The Al2O3 content of the 88 bauxite is ≥88%; The Al2O3 content of the alumina micropowder is ≥99%; The SiO2 content in the bentonite is ≥62%; The SiO2 content of the Guangxi white mud is ≥48%; The SiO2 content of the third-grade clay is ≥62%; The Cr2O3 content in the chromium oxide green is ≥99%.

5. The method for preparing a coating material for an impregnated pipe according to any one of claims 1 to 4, characterized in that: The method comprises the following preparation steps: (1) Weighing the raw materials by weight and placing them in a blender; (2) dry-mixing the raw materials and then adding water to mix; (3) The mixed mud material is placed in a sealed bag or a sealed barrel and sealed for more than 8 hours to obtain the coating material for the impregnated pipe.

6. The method for preparing a coating material for an impregnated pipe according to claim 5, characterized in that: The dry mixing time in step (2) is 1-2 minutes, 10-20 parts of water are added by weight, and the net mixing time after adding water is 2-4 minutes.

7. The method for preparing a coating material for an impregnated pipe according to claim 5, characterized in that: The entrainment in step (3) is carried out at an environment of 16-25°C.

8. The method for preparing a coating material for an impregnated pipe according to claim 5, characterized in that: The method further includes step (4), wherein the coating material described in step (3) is taken out and used, and is baked to enhance its strength.

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