Repair material for cracks in hot metal pretreatment desulfurization spray guns

Abstract

The present invention discloses a repair material for cracks in a molten iron pretreatment desulfurization spray gun. The repair material is composed of the following raw materials in percentage by weight: 71-82% 85-88 alumina, 4-9% activated alumina powder, 1-3% silica powder, 3-7% ash clay, 0.5-1.5% chrome green, 1.5-6% chrome concentrate, 0.3-1.5% boric acid, 3-6% PA80, 0.1-0.3% CMC, 0.05-0.15% organic chemical fiber, and 0.03-0.1% iron ore concentrate powder. The raw materials are uniformly mixed in proportion to produce a repair material that exhibits good pre-sintering air permeability and adhesion, rapid sintering, and thus thermal stability. The material also exhibits strong bonding strength, strong anti-stripping properties, and extrusion rheology.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking, and more particularly to a repairing material for cracks in a desulfurization lance for molten iron pretreatment. Background Art

[0002] Domestic steel companies use a variety of methods for hot metal pretreatment, including continuous ditch treatment (spreading), ladle spraying, mechanical stirring, dedicated furnaces, shake ladle, drum, bell jar, and spraying. Ladle spraying involves spraying a pretreatment agent into the hot metal in the ladle using a spray gun (with the nozzle at the bottom or near the bottom of the gun on the side wall) to allow the pretreatment agent to fully react with the hot metal, thereby purifying the hot metal. The lance used is called a hot metal pretreatment desulfurization lance. The lance is inserted into the molten iron to a certain depth. The refractory material in the inserted portion of the lance develops transverse or longitudinal cracks due to the intense erosion of the molten iron and the frequent rapid cooling and heating (one insertion typically lasts from a few minutes to more than ten minutes or even longer, with each tank of desulfurization completed and then removed from service, waiting for the next tank, repeating this intermittent operation). (The refractory material expands less than the steel structure embedded within it, and such cracks are currently unavoidable.) These cracks expand with increased use, causing the molten iron to penetrate and contact the steel structure, resulting in burn-through and unavailability. Severe cracking in the refractory reduces the service life of the lance and affects the technical and economic indicators of the desulfurization process.

[0003] At present, in order to effectively extend the service life of the spray gun, many manufacturers have successively adopted a variety of repair materials for repair. However, as steel companies carry out deep desulfurization at a fast pace to reduce the cooling of molten iron and improve efficiency or the need for high-quality steel, the desulfurization time is extended. The original repair time is also shortened accordingly, and the use time of each spray gun is extended. The repair materials currently on the market generally have the problem of needing to use the repair material layer before it has time to sinter. Such repair materials fall off after one or two uses, requiring frequent repairs, resulting in waste and increased work intensity. There is even a risk of the repair material falling off midway (not completing one use or falling off several times), resulting in the risk of steel penetration, seriously affecting the economic benefits and desulfurization effect of the steel plant, and shortening the service life of the desulfurization spray gun.

[0004] Therefore, how to provide a fast-sintering repair material that can increase the service life of the molten iron pretreatment desulfurization lance is a problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a repair material for cracks in a molten iron pretreatment desulfurization lance, which has good hot air permeability and adhesion, rapid sintering properties, and strong bonding strength.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: a repair material for cracks in a desulfurization lance for pretreatment of molten iron, comprising the following raw materials in weight percentage: 85-88 bauxite 71-82%, activated alumina powder 4-9%, silicon dioxide 1-3%, ash clay 3-7%, chrome green 0.5-1.5%, chrome concentrate 1.5-6% 、 Boric acid 0.3-1.5%, PA803-6%, CMC 0.1-0.3%, organic chemical fiber 0.05-0.15%, iron ore powder 0.03-0.1%.

[0007] Preferably, the raw materials are composed of the following weight percentages: 85-88 bauxite 74-82%, activated alumina powder 6-9%, silica powder 1-3%, ash clay 4-7%, chrome green 0.5-1.5%, chrome concentrate 2-5%, boric acid 0.3-1.1%, PA804-6%, CMC 0.1-0.3%, organic chemical fiber 0.05-0.15%, and iron ore powder 0.03-0.1%.

[0008] Preferably, the raw materials are composed of the following weight percentages: 78% alumina, 6% activated alumina powder, 3% silica powder, 5% ash clay, 1% chrome green, 1.5% chrome concentrate, 1.1% boric acid, 4% PA80, 0.25% CMC, 0.1% organic chemical fiber, and 0.05% iron ore powder.

[0009] The beneficial effects of the above technical solution are: the repair material obtained by using the above raw material formula has good air permeability and adhesion performance before sintering of the mud material, rapid sintering performance, thereby ensuring thermal stability, high-temperature volume stability, strong bonding force, strong anti-stripping performance and extrusion rheology, and is suitable for deep desulfurization and fast-paced production in steel mills.

[0010] Preferably, the particle size of the 85-88 alumina is 0.074-3 mm;

[0011] The particle size of the activated alumina powder is 1 μm-5 μm;

[0012] The particle size of the silicon dioxide powder is 1 μm-5 μm;

[0013] The particle size of the ash clay is 0.04mm -0.074mm;

[0014] The particle size of the chrome green is 0.04mm -0.074mm;

[0015] The particle size of the chromium concentrate is 0.15-0.3 mm;

[0016] The particle size of the boric acid is 0.1mm -3mm;

[0017] The particle size of the PA80 is 0.1mm -3mm;

[0018] The length of the organic chemical fiber is 2-5 mm;

[0019] The particle size of the iron ore concentrate powder is 0.1 mm to 0.2 mm.

[0020] Preferably, in the 85-88 alumina, the 85-88 alumina with a particle size of 1-3 mm accounts for 15-30% of the total mass of the 85-88 alumina.

[0021] Preferably, the mass percentage of Al2O3 of the 85-88 bauxite is 85-88%;

[0022] The Al2O3 mass percentage of activated alumina micropowder is ≥99%;

[0023] The SiO2 mass percentage of silica powder is 92-96%;

[0024] The mass percentage of Al2O3 in ash clay is 30-32%;

[0025] The mass percentage of Cr2O3 in chrome green is ≥99%;

[0026] The Cr2O3 mass percentage of chrome concentrate is 45-47%;

[0027] The Tfe content of the iron ore concentrate is 65-68% by mass.

[0028] The beneficial effects of the above technical solution are as follows: controlling the particle size of 85-88 bauxite and the content of Al2O3 can ensure the high-temperature performance of the repair material; controlling the particle size of activated alumina micropowder and the content of Al2O3, as well as the particle size of chrome green and the content of Cr2O3 can enhance the high-temperature volume stability and thermal shock stability of the repair material, because alumina and chrome green can form spinel; controlling the particle size of silica micropowder and the content of SiO2 can enhance the high-temperature strength of the repair material; adding organic fiber can prevent the repair material of the present invention from bursting during use; adding iron ore concentrate powder and chrome concentrate can ensure high-temperature permeability, and utilizing the channels generated when PA80 reacts with iron to release gas, the repair material can quickly remove water vapor and sinter; adding boric acid and PA80 to jointly promote sintering, and PA80 is also a binder, with adhesion and plasticity; adding CMC and ash clay makes the repair material plastic and moisturizing.

[0029] The present invention also provides a method for preparing a repair material for cracks in a molten iron pretreatment desulfurization lance, comprising the following steps:

[0030] Mix the raw materials evenly according to the above proportions and pack them in small plastic bags.

[0031] The present invention also provides an application of the repair material for cracks in molten iron pretreatment desulfurization spray guns. When the repair material is used, it can be applied by adding water and stirring it into a spreadable state. The viscosity (jump table method) can be between 44-75%. The repair material can be used for one day after being stirred once (placed naked). If it is sealed in a plastic bag and placed, it can be kept for more than 15 days (just add a small amount of water to adjust it when used), and the usage amount is small.

[0032] It can be seen from the above technical solutions that, compared with the prior art, the present invention has at least the following technical effects:

[0033] (1) The repair material of the present invention has good hot air permeability and adhesion, rapid sintering, and strong bonding force, and therefore has strong anti-scouring and anti-stripping properties and thermal shock stability, plasticity and compressive rheology; at 1100℃*20min, water-cooled high-temperature thermal shock is carried out 9 times, and its residual flexural strength is 0.3-0.7MPa, and the residual compressive strength is 13-15MPa. After 9 water-cooled thermal shocks, the mass loss is 1.85-3.47% (stripping rate of anti-stripping performance).

[0034] (2) The preparation is simple, the dry mixing is uniform, and the product can be packaged in moisture-proof small bags. When using, take the required amount of material (a small amount of material is needed), add water and stir until it is spreadable and can be squeezed into any shape. The mud material can be kept for 1 day, which provides convenience for the transportation and storage of the product. DETAILED DESCRIPTION

[0035] 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 some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0036] Example 1

[0037] The repair material for cracks in the desulfurization lance for hot metal pretreatment is composed of the following raw materials in percentage by mass:

[0038] 85-88 bauxite 78%, activated alumina powder 6%, silica powder 3%, ash clay 5%, chrome green 1%, chrome concentrate 1.5%, boric acid 1.1%, PA804%, CMC 0.25%, organic chemical fiber 0.1%, iron ore powder 0.05%;

[0039] The Al2O3 content of 85-88 bauxite is 87.5% by mass and the particle size is 0.074-3mm; the Al2O3 content of activated alumina powder is 99.5% by mass and the particle size is 1-5μm; the SiO2 content of silica powder is 92.8% by mass and the particle size is 1-5μm; the Al2O3 content of ash clay is 30.2% by mass and the particle size is 0.04-0.074mm. The mass percentage of Cr2O3 in chrome green is 99%, and the particle size is 0.04-0.074mm; the mass percentage of Cr2O3 in chrome concentrate is 46%, and the particle size is 0.15-0.3mm; the particle size of boric acid is 0.1-3mm; the particle size of PA80 is 0.1-3mm; the length of organic chemical fiber is 2-5mm; the mass percentage of Tfe in iron ore powder is 65%, and the particle size is 0.1-0.2mm.

[0040] After 1100℃*20min water cooling thermal shock, the residual flexural strength is 0.41MPa and the residual compressive strength is 14.8MPa.

[0041] Example 2

[0042] The repair material for cracks in the desulfurization lance for hot metal pretreatment is composed of the following raw materials in percentage by mass:

[0043] 85-88 bauxite 77.42%, activated alumina powder 7%, silica powder 2%, ash clay 5%, chrome green 0.5%, chrome concentrate 3%, boric acid 0.3%, PA804.5%, CMC 0.1%, organic chemical fiber 0.15%, iron ore powder 0.03%;

[0044] The Al2O3 mass percentage of 85-88 bauxite is 86.7% and the particle size is 0.074-3mm; the Al2O3 mass percentage of activated alumina powder is 99.3% and the particle size is 1-5μm; the SiO2 mass percentage of silica powder is 93.5% and the particle size is 1-5μm; the Al2O3 mass percentage of ash clay is 32% and the particle size is 0.04-0.074mm; chrome green The mass percentage of Cr2O3 in the chromium concentrate is 99.2%, and the particle size is 0.04-0.074mm; the mass percentage of Cr2O3 in the chromium concentrate is 46.1%, and the particle size is 0.15-0.3mm; the particle size of boric acid is 0.1-3mm; the particle size of PA80 is 0.1-3mm; the length of the organic chemical fiber is 2-5mm; the mass percentage of Tfe in the iron ore powder is 66%, and the particle size is 0.1-0.2mm.

[0045] After 1100℃*20min water cooling thermal shock, the residual flexural strength is 0.39MPa and the residual compressive strength is 14.6MPa.

[0046] Example 3

[0047] The raw material ratio, chemical composition and particle size are basically the same as those in Example 1, with the only difference being that the Al2O3 content in the bauxite is 85%. After 9 water-cooled thermal shocks at 1100℃*20min, the residual flexural strength is 0.38Pa and the residual compressive strength is 13.2MPa.

[0048] Example 4

[0049] The raw material ratio, chemical composition and particle size are basically the same as those in Example 1, except that the Al2O3 content in the bauxite is 88%. After 9 thermal shocks at 1100°C for 20 minutes, the residual flexural strength is 0.64 MPa and the residual compressive strength is 15 MPa.

[0050] Example 5

[0051] The raw material ratio, chemical composition and particle size are basically the same as those in Example 1, except that the SiO2 content in the silica powder is 92.3%. After 9 thermal shocks at 1100℃*20min, the residual flexural strength is 0.55MPa and the residual compressive strength is 13.5MPa.

[0052] Example 6

[0053] The raw material ratio, chemical composition and particle size are basically the same as those in Example 1, except that the mass percentage of SiO2 in the silica powder is 95.8%. After 9 thermal shocks at 1100℃*20min, the residual flexural strength is 0.7MPa and the residual compressive strength is 14.3MPa.

[0054] Example 7

[0055] The raw material ratio, chemical composition and particle size are basically the same as those in Example 1, except that the mass percentage of Al2O3 in the ash clay is 30.3%. After thermal shock at 1100℃*20min, the residual flexural strength is 0.57MPa and the residual compressive strength is 14.2MPa.

[0056] Example 8

[0057] The raw material ratio, chemical composition and particle size are basically the same as those in Example 1, except that the mass percentage of Al2O3 in the ash clay is 31.7%, and after thermal shock at 1100℃*20min, the residual flexural strength is 0.56MPa and the residual compressive strength is 14.5MPa.

[0058] Comparative Example 1

[0059] The raw material ratio and chemical composition are basically the same as those in Example 1, with the only difference being that the alumina particle size is increased to 5 mm. After 9 thermal shocks at 1100°C*20 min, the residual flexural strength is 0.8 MPa and the residual compressive strength is 16 MPa.

[0060] Comparative Example 2

[0061] The raw material ratio, chemical composition and particle size are basically the same as those in Example 1, except that the addition ratio of PA80 is reduced to 2%. After three thermal shocks at 1100°C*20min, the residual flexural strength is 0.1MPa and the residual compressive strength is 0.7MPa.

[0062] The comparison of tracking Example 1 when used in a steel plant in Liaoning is shown in Table 1:

[0063] Table 1

[0064]

[0065] The experimental results show that when used in a steel plant in Liaoning, the overall life of the desulfurization spray gun is increased by more than 35%; at the same time, the use of the coating material of the present invention can save an average of 18.3 spray guns and increase the service life by 10.9 times, which is an average increase of 42.3% compared to not using the coating material of the present invention.

[0066] The hot-state rapid sintering repair material of the present invention can eliminate water vapor and sinter within 3-8 minutes (the coating thickness is 7-25 mm), which can meet the fast-paced production needs of steel mills and the needs of deep desulfurization and long-term work.

[0067] The refractory cracks of the molten iron pretreatment desulfurization spray gun must be coated before they are smaller than 5mm. If the cracks exceed 5mm, the refractory thickness is thin, and the steel structure inside is directly in contact with the molten iron and burned. The coating material particle size is larger than the crack gap and cannot be coated.

[0068] The disclosed embodiments are described 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 to be construed in the widest possible manner consistent with the principles and novel features disclosed herein.

Claims

1. A repair material for cracks in a molten iron pretreatment desulfurization lance, characterized in that: The invention is composed of the following raw materials in weight percentage: 71-82% of 85-88 bauxite, 4-9% of activated alumina powder, 1-3% of silicon dioxide powder, 3-7% of ash clay, 0.5-1.5% of chrome green, 1.5-6% of chrome concentrate, 0.3-1.5% of boric acid, 3-6% of PA80, 0.1-0.3% of CMC, 0.05-0.15% of organic chemical fiber, and 0.03-0.1% of iron ore concentrate powder; The particle size of the 85-88 bauxite is 0.074mm-3mm; The particle size of the activated alumina powder is 1 μm-5 μm; The particle size of the silicon dioxide powder is 1 μm-5 μm; The particle size of the ash clay is 0.04mm-0.074mm; The particle size of the chrome green is 0.04mm-0.074mm; The particle size of the chromium concentrate is 0.15-0.3 mm; The particle size of the boric acid is 0.1 mm to 3 mm; The particle size of the PA80 is 0.1mm-3mm; The length of the organic chemical fiber is 2-5 mm; The particle size of the iron ore concentrate powder is 0.1 mm to 0.2 mm.

2. The repair material for cracks in molten iron pretreatment desulfurization lance according to claim 1, characterized in that: The invention is composed of the following raw materials in weight percentage: 74-82% of 85-88 bauxite, 6-9% of activated alumina fine powder, 1-3% of silicon dioxide fine powder, 4-7% of ash clay, 0.5-1.5% of chrome green, 2-5% of chrome concentrate, 0.3-1.1% of boric acid, 4-6% of PA80, 0.1-0.3% of CMC, 0.05-0.15% of organic chemical fiber and 0.03-0.1% of iron ore concentrate powder.

3. The repair material for cracks in molten iron pretreatment desulfurization lance according to claim 1, characterized in that: The invention is composed of the following raw materials in percentage by weight: 78% of 85-88 alumina, 6% of activated alumina powder, 3% of silica powder, 5% of ash clay, 1% of chrome green, 1.5% of chrome concentrate, 1.1% of boric acid, 4% of PA80, 0.25% of CMC, 0.1% of organic chemical fiber and 0.05% of iron ore concentrate powder.

4. The repair material for cracks in molten iron pretreatment desulfurization lance according to claim 1, characterized in that: In the 85-88 bauxite, the 85-88 bauxite with a particle size of 1-3 mm accounts for 15-30% of the total mass of the 85-88 bauxite.

5. The repair material for cracks in molten iron pretreatment desulfurization lance according to claim 4, characterized in that: The Al2O3 mass percentage of the 85-88 bauxite is 85-88%; The Al2O3 mass percentage of the activated alumina micropowder is ≥99%; The SiO2 mass percentage of the silicon dioxide powder is 92-96%; The Al2O3 mass percentage of the ash clay is 30-32%; The Cr2O3 mass percentage of the chrome green is ≥99%; The chromium concentrate has a Cr2O3 mass percentage of 45-47%; The Tfe content of the iron ore concentrate powder is 65-68% by mass.

6. The use of the repair material for cracks in a molten iron pretreatment desulfurization lance according to any one of claims 1 to 5, characterized in that: When the repair material is used, it can be applied after being stirred with water into a spreadable state; the viscosity measured by the jumping table method is between 44-75%.

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