A method for preparing an anti-burn loss cannon cap

Abstract

The present application relates to a kind of preparation methods of anti-burn loss cannon cap, comprising the following steps: (1) preparation cannon cap cast iron piece: the chemical composition of cannon cap cast iron piece is: C: 3.0~3.5%, Si: 1.2~1.5%, Mn: 0.2~0.5%, P≤0.1%, S≤0.04%, Ni: 0.004~0.008%, the balance is Fe and impurities, pouring, natural cooling;(2) cannon cap cast iron piece hot-dip alloy coating: 35 steel high temperature melts, add Mn, Cr, Ni alloy, adjust Mn in steel: 2~3%, Cr: 0.25~0.55%, Ni: 0.5~0.9%, obtain alloy molten liquid, cannon cap cast iron piece is immersed in alloy molten liquid, soak 30~60s take out natural cooling;(3) cannon cap brushes high-temperature resistant coating: preparation high-temperature resistant coating, and brush in the cannon cap inside and outside surface after hot-dip alloy coating, coating is dried after cannon cap can be put into production use;The cannon cap prepared by the present application greatly reduces the maintenance cost and maintenance frequency of blast furnace, improves blast furnace production efficiency, realizes long-term smooth running of blast furnace, and stable yield.

Description

Technical Field

[0001] This invention relates to the field of blast furnace maintenance technology in ironmaking plants, and in particular to a method for preparing a burn-resistant blast furnace cap. Background Technology

[0002] Previously, the blast furnaces in ironmaking plants used cast steel mud cannon caps. These cast steel caps were used in blast furnaces with a capacity of 2000m³ to 3000m³. The hot blast pressure in the blast furnace is high, and the physical temperature of the molten iron is above 1500℃. The cast steel caps are not resistant to high temperature and high pressure erosion, which often causes the caps to burn out when the mud cannon is blocked. This results in mud coming out of the cap or the cap failing to seal the taphole. It is necessary to reduce the blast furnace smelting intensity in order to replace the cap and block the taphole. This causes the taphole depth to be substandard for a long time, which threatens the cooling intensity of the taphole area. The thickness of the carbon bricks in the taphole area will be burned off prematurely and become thinner. The cooling intensity will increase, the amount of cap burn-off will be large, the replacement of the cap will be difficult, and the monthly cost of cap consumption will be high.

[0003] As blast furnaces enter production and use, those that have been in operation for more than 10 years reach the middle and later stages of their lifespan, making it even more crucial to maintain proper taphole depth and improve the taphole depth compliance rate to ensure normal taphole heat load. To reduce the safety threat posed by shallow tapholes to the taphole area and ensure a taphole depth compliance rate of >95%, it is essential to prevent taphole blockage and mud leakage caused by burnt taphole caps and inability to seal the taphole, which leads to persistent substandard taphole depth. Therefore, it is necessary to develop a taphole cap that can withstand the high temperature and pressure of molten iron and the erosion of slag and iron without easily burning out. Summary of the Invention

[0004] The purpose of this invention is to address the problem that in the later stages of blast furnace operation, cast steel tappets are not resistant to high temperatures and high pressures, often resulting in tappet burn-out when the mud gun is blocked. This causes mud to escape from the tappet or the tappet cannot be sealed properly, requiring a reduction in blast furnace smelting intensity to replace the tappet. Consequently, the taphole depth is consistently below standard, the carbon brick thickness in the taphole area is prematurely burned off, and the amount of tappet burn-out increases, making tappet replacement difficult. This cyclical deterioration severely affects blast furnace production efficiency and service life. The invention provides a method for preparing a burn-resistant tappet.

[0005] The present invention provides a method for preparing a burn-resistant cast gun cap, comprising the following steps: (1) Preparation of cast iron gun caps: molten iron is smelted according to the following chemical composition by mass fraction: C: 3.0~3.5%, Si: 1.2~1.5%, Mn: 0.2~0.5%, P≤0.1%, S≤0.04%, Ni: 0.004~0.008%, with the balance being Fe and unavoidable impurities; after the molten iron is qualified, the gun caps are cast, and after casting, they are naturally cooled to 230~280℃; (2) Hot-dip alloy coating of cast iron gun cap: 35 steel is melted at high temperature and heated to above 1530°C. Mn, Cr and Ni alloy are added and the steel is adjusted to Mn: 2-3%, Cr: 0.25-0.55% and Ni: 0.5-0.9% to obtain alloy melt. Cast iron gun caps cooled to 230-280°C are immersed in the above alloy melt for 30-60 seconds and then taken out and naturally cooled to 60-80°C. (3) Applying a high-temperature resistant coating to the gun cap: Prepare a high-temperature resistant coating and apply it to the inner and outer surfaces of the gun cap that has been hot-dip coated with an alloy. The coating thickness is 1.0 to 1.2 mm. After the coating dries, the gun cap can be put into production and use. The high-temperature resistant coating is prepared by mixing powder and solvent in a mass ratio of 3:2. The mass percentage of each substance in the powder is as follows: refractory cement: 5%, brown corundum powder: 15%, high alumina clay: 80%, and the solvent is water glass with a modulus of 3.2, a specific gravity of 1.38, and a SiO2 content of 27%.

[0006] Furthermore, in step (2) above, after the cast iron part of the gun cap is hot-dip coated with alloy molten liquid, an alloy coating is formed on the surface of the cast iron part of the gun cap. The alloy coating contains the following chemical composition in terms of mass fraction: Mn: 2.3-2.5%, Cr: 0.33-0.38%, Ni: 0.6-0.8%.

[0007] Preferably, in step (3) above, the refractory cement is refractory cement with a grade of 628, the brown corundum powder has an Al2O3 mass fraction of 95-97% and a particle size of 200 mesh, and the high alumina clay has an Al2O3 mass fraction of ≥25% and a particle size of 200 mesh.

[0008] Furthermore, in step (3) above, the temperature of the gun cap is raised to 60-80°C before applying the high-temperature resistant coating.

[0009] Preferably, in step (3) above, the high-temperature resistant coating on the gun cap can be applied by immersion. That is, the gun cap that has been hot-dip coated with alloy and naturally cooled to 60-80°C is directly immersed in the high-temperature resistant coating for 30-60 seconds. After taking it out, it can be dried in 2-3 minutes and put into production.

[0010] This invention improves the production process of the gun cap while maintaining its original shape. Specifically, the gun cap is first changed from a cast steel part to a cast iron part. A small amount of manganese alloy and nickel alloy are added to the molten iron before casting. After the cast iron gun cap with added manganese and nickel is cast and formed, the inner and outer surfaces of the gun cap are then hot-dip coated with an alloy layer. The surface of the gun cap after hot-dip coating forms an alloy coating containing the following chemical composition by mass fraction: Mn: 2.3-2.5%, Cr: 0.33-0.38%, Ni: 0.6-0.8%. This improves the hardening properties of the cast gun cap, forming a hard outer shell on the inner and outer surfaces, making it more resistant to erosion. After the hot-dip alloy coating is completed, a high-temperature resistant coating is applied to the entire inner and outer surfaces of the gun cap. The high-temperature resistant coating contains Al2O3 ≥ 70%, has a refractoriness ≥ 1650℃, and its temperature resistance is 50-100℃ higher than that of molten iron. The hardened gun cap shell is coated with a high-temperature resistant coating, which makes the gun cap resistant to both high temperature and high pressure when plugging the muzzle. The surface of the gun cap is not easily burned by high-temperature and high-pressure slag iron, thus achieving the purpose of modifying the gun cap.

[0011] The improvement principle of this invention is as follows: Cast iron cannon caps are relatively resistant to high-temperature burning, but they are not resistant to high-pressure, high-temperature slag and iron erosion, and are not resistant to pressure shock, making them easily damaged. Nickel and manganese are added before casting the cannon cap. After the cannon cap is formed, the inner and outer surfaces are hot-dip coated with an alloy coating, and then coated with a high-temperature resistant paint that can withstand molten iron temperatures of 50-100℃. This makes the inner and outer surfaces of the cannon cap resistant to both high temperatures and high-pressure slag and iron erosion, increasing hardness and resistance to pressure shock, making it less prone to breakage. After the cannon cap comes into contact with the high-temperature, high-pressure slag and iron erosion for 2-3 seconds, it comes into contact with the mud sleeve at the iron opening. Mud is immediately pushed into the iron opening channel. Simultaneously, water is sprayed in front of the cannon cap to cool it down, preventing the cannon cap temperature from reaching the melting point. This ensures the cannon cap is not easily burned, maintains good integrity, and achieves the effect of preventing mud from escaping from the iron opening.

[0012] This invention was used simultaneously in two blast furnaces of the applicant's company from 2021 to 2023 and achieved the following beneficial effects: 1. The cannon cap is resistant to burn damage, and the number of cannon caps burned has been greatly reduced, resulting in a significant decrease in the number of cannon caps that need to be replaced. Previously, one cannon cap was replaced after each furnace blockage, but now one cannon cap is replaced after four or five furnace blockages. The labor intensity of replacing cannon caps at the furnace has been greatly reduced, and the cost of using cannon caps has been significantly reduced.

[0013] 2. The cannon cap is resistant to burn-through and high-pressure erosion. The cannon cap is less prone to burn-through when plugging the sluice gate, reducing mud leakage by 80%. The sluice gate depth compliance rate has increased from 75% to over 95%, significantly improving the production safety factor in the sluice gate area. Currently, there has not been a single instance of the sluice gate being unable to be plugged due to cannon cap burn-through.

[0014] 3. With the improvement of the qualified rate of taphole depth, the uniformity of blast furnace tapping is improved, and slag and iron can be completely discharged within the specified time, so as to achieve long-term smooth operation, stable production and high output of blast furnace. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural schematic diagram of the cannon cap obtained in Embodiment 1 of the present invention; Figure 2 This is a three-dimensional structural schematic diagram of the gun cap obtained in Embodiment 1 of the present invention from another perspective.

[0016] In the picture, 1—cannon cap. Detailed Implementation

[0017] To better explain the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments. The following embodiments are merely illustrative of the technical solution of the present invention and do not limit the present invention in any way. The sequence numbers of the following embodiments are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0018] Example 1 A method for preparing a burn-resistant cast gun cap includes the following steps: (1) Preparation of cast iron gun caps: molten iron is smelted according to the following chemical composition by mass fraction: C: 3.0~3.5%, Si: 1.2~1.5%, Mn: 0.2~0.5%, P≤0.1%, S≤0.04%, Ni: 0.004~0.008%, with the balance being Fe and unavoidable impurities; after the molten iron is qualified, the gun caps are cast, and after casting, they are naturally cooled to 250℃; (2) Hot-dip alloy coating of cast iron gun cap: 35 steel is melted at high temperature and heated to above 1530°C. Mn, Cr and Ni alloy are added and the steel is adjusted to Mn: 2-3%, Cr: 0.25-0.55% and Ni: 0.5-0.9% to obtain alloy melt. The cast iron gun cap, cooled to 250°C, is immersed in the above alloy melt for 45 seconds and then taken out and naturally cooled to 70°C. After hot-dip alloy coating, an alloy coating is formed on the surface of the cast iron gun cap. The alloy coating contains the following chemical composition by mass fraction: Mn: 2.5%, Cr: 0.35%, Ni: 0.72%. (3) Applying a high-temperature resistant coating to the gun cap: Prepare a high-temperature resistant coating and apply it to the inner and outer surfaces of the gun cap that has been hot-dip coated with an alloy. The coating thickness is 1.0 mm. After the coating dries, the gun cap 1 can be put into production and use. The high-temperature resistant coating is prepared by mixing powder and solvent in a mass ratio of 3:2. The mass percentage of each substance in the powder is as follows: refractory cement: 5%, brown corundum powder: 15%, high alumina clay: 80%, the solvent is water glass with a modulus of 3.2, a specific gravity of 1.38, and a SiO2 content of 27%.

[0019] In the above steps, the refractory cement used is refractory cement with a grade of 628, the brown corundum powder has an Al2O3 mass fraction of 97% and a particle size of 200 mesh, and the high alumina clay has an Al2O3 mass fraction of 25% and a particle size of 200 mesh.

[0020] The gun cap 1 prepared in Example 1 was used in the applicant's No. 1 and No. 2 blast furnaces. The production situation after one year of use was statistically analyzed, and the results are shown in Table 1 below: Table 1. Statistics on the average daily production rate of the gun caps prepared in Example 1.

[0021] Table 2. Statistics on the production status of the gun caps prepared in Example 1 for one year.

[0022] The above statistics only include the cost savings of 1.573 million yuan per year from replacing the taphead. The impact of uneven tapping caused by the burning of the taphead has not been included in the furnace condition. If this item were included, the annual production cost savings would be even higher.

[0023] Example 2 A method for preparing a burn-resistant cast gun cap includes the following steps: (1) Preparation of cast iron gun caps: molten iron is smelted according to the following chemical composition by mass fraction: C: 3.0~3.5%, Si: 1.2~1.5%, Mn: 0.2~0.5%, P≤0.1%, S≤0.04%, Ni: 0.004~0.008%, with the balance being Fe and unavoidable impurities; after the molten iron is qualified, the gun cap is cast, and after casting, it is naturally cooled to 230℃; (2) Hot-dip alloy coating of cast iron gun cap: 35 steel is melted at high temperature and heated to above 1540°C. Mn, Cr and Ni alloy are added and the steel is adjusted to Mn: 2-3%, Cr: 0.25-0.55% and Ni: 0.5-0.9% to obtain alloy melt. The cast iron gun cap, cooled to 230°C, is immersed in the above alloy melt for 60 seconds and then taken out and naturally cooled to 80°C. After hot-dip alloy coating, an alloy coating is formed on the surface of the cast iron gun cap. The alloy coating contains the following chemical composition by mass fraction: Mn: 2.3%, Cr: 0.38%, Ni: 0.60%. (3) Applying a high-temperature resistant coating to the gun cap: Prepare a high-temperature resistant coating, immerse the gun cap, which has been hot-dip coated with an alloy and naturally cooled to 80°C, directly into the high-temperature resistant coating for 30 seconds, remove it, and allow the coating to dry for 2 minutes before putting the gun cap into production use; the high-temperature resistant coating is prepared by mixing powder and solvent in a mass ratio of 3:2. The mass percentage of each substance in the powder is as follows: refractory cement: 5%, brown corundum powder: 15%, high alumina clay: 80%, the solvent is water glass, modulus is 3.2, specific gravity: 1.38, SiO2 content is 27%. The refractory cement is refractory cement with a grade of 628, the brown corundum powder has an Al2O3 mass fraction of 96% and a particle size of 200 mesh, and the high alumina clay has an Al2O3 mass fraction of 28.5% and a particle size of 200 mesh.

[0024] Example 3 A method for preparing a burn-resistant cast gun cap includes the following steps: (1) Preparation of cast iron gun caps: molten iron is smelted according to the following chemical composition by mass fraction: C: 3.0~3.5%, Si: 1.2~1.5%, Mn: 0.2~0.5%, P≤0.1%, S≤0.04%, Ni: 0.004~0.008%, with the balance being Fe and unavoidable impurities; after the molten iron is qualified, the gun caps are cast, and after casting, they are naturally cooled to 280℃; (2) Hot-dip alloy coating of cast iron gun cap: 35 steel is melted at high temperature and heated to above 1550°C. Mn, Cr and Ni alloy are added and the steel is adjusted to Mn: 2-3%, Cr: 0.25-0.55% and Ni: 0.5-0.9% to obtain alloy melt. The cast iron gun cap, cooled to 280°C, is immersed in the above alloy melt for 60 seconds and then taken out and naturally cooled to 60°C. After hot-dip alloy coating, an alloy coating is formed on the surface of the cast iron gun cap. The alloy coating contains the following chemical composition by mass fraction: Mn: 2.4%, Cr: 0.33%, Ni: 0.80%. (3) Applying a high-temperature resistant coating to the gun cap: Prepare a high-temperature resistant coating, immerse the gun cap, which has been hot-dip coated with an alloy and naturally cooled to 80°C, directly into the high-temperature resistant coating for 60 seconds, remove it, and allow the coating to dry for 3 minutes before putting the gun cap into production use; the high-temperature resistant coating is prepared by mixing powder and solvent in a mass ratio of 3:2. The mass percentage of each substance in the powder is as follows: refractory cement: 5%, brown corundum powder: 15%, high alumina clay: 80%, the solvent is water glass, modulus is 3.2, specific gravity: 1.38, SiO2 content is 27%. The refractory cement is refractory cement with a grade of 628. The brown corundum powder has an Al2O3 mass fraction of 96% and a particle size of 200 mesh. The high alumina clay has an Al2O3 mass fraction of 29% and a particle size of 200 mesh.

[0025] After the blast furnace caps produced in Examples 1, 2, and 3 were put into blast furnace production, the number of burnt caps decreased significantly, each cap could be used for 4-5 heats, the number of times mud came out of the taphole decreased by 80%, and the taphole depth compliance rate increased from 75% to over 95%. The production safety factor in the taphole area was greatly improved, and there were no instances of the taphole not being blocked due to cap burnout. Furthermore, with the improvement in the taphole depth compliance rate, the uniformity of blast furnace tapping improved, and slag and iron could be completely removed within the specified time, achieving long-term smooth operation and stable high production of the blast furnace. This indicates that the blast furnace caps produced by this invention have good performance in actual production and are suitable for large-scale promotion and use.

[0026] The above embodiments are merely specific examples exemplified to explain the present invention and do not limit the present invention in any way. Any non-substantial changes made by any person based on the above content and form that do not depart from the scope of protection of the claims of the present invention should be considered to fall within the scope of protection of the claims of the present invention. The present invention is not limited to the specific embodiments described above, nor is the structure of the gun cap of the present invention limited to the drawings shown in the present invention.

Claims

1. A method for preparing a burn-resistant cast gun cap, characterized in that... Includes the following steps: (1) Preparation of cast iron gun caps: molten iron is smelted according to the following chemical composition by mass fraction: C: 3.0~3.5%, Si: 1.2~1.5%, Mn: 0.2~0.5%, P≤0.1%, S≤0.04%, Ni: 0.004~0.008%, with the balance being Fe and unavoidable impurities; after the molten iron is qualified, the gun caps are cast, and after casting, they are naturally cooled to 230~280℃; (2) Hot-dip alloy coating of cast iron gun cap: 35 steel is melted at high temperature and heated to above 1530°C. Mn, Cr and Ni alloy are added and the steel is adjusted to Mn: 2-3%, Cr: 0.25-0.55% and Ni: 0.5-0.9% to obtain alloy melt. Cast iron gun caps cooled to 230-280°C are immersed in the above alloy melt for 30-60 seconds and then taken out and naturally cooled to 60-80°C. (3) Applying a high-temperature resistant coating to the gun cap: Prepare a high-temperature resistant coating and apply it to the inner and outer surfaces of the gun cap that has been hot-dip coated with an alloy. The coating thickness is 1.0 to 1.2 mm. After the coating dries, the gun cap can be put into production and use. The high-temperature resistant coating is prepared by mixing powder and solvent in a mass ratio of 3:

2. The mass percentage of each substance in the powder is as follows: refractory cement: 5%, brown corundum powder: 15%, high alumina clay: 80%, and the solvent is water glass with a modulus of 3.2, a specific gravity of 1.38, and a SiO2 content of 27%.

2. The method for preparing a burn-resistant cast gun cap according to claim 1, characterized in that: In step (2), after the cast iron part of the gun cap is hot-dip coated with alloy molten liquid, an alloy coating is formed on the surface of the cast iron part of the gun cap. The alloy coating contains the following chemical composition by mass fraction: Mn: 2.3-2.5%, Cr: 0.33-0.38%, Ni: 0.6-0.8%.

3. The method for preparing a burn-resistant cast gun cap according to claim 1, characterized in that: In step (3), the refractory cement is refractory cement with a grade of 628, the brown corundum powder has an Al2O3 mass fraction of 95-97% and a particle size of 200 mesh, and the high alumina clay has an Al2O3 mass fraction of ≥25% and a particle size of 200 mesh.

4. The method for preparing a burn-resistant cast gun cap according to claim 1, characterized in that: In step (3), the temperature of the gun cap is raised to 60-80℃ before applying the high-temperature resistant coating.

5. The method for preparing a burn-resistant cast gun cap according to claim 1, characterized in that: In step (3), the high-temperature resistant coating on the gun cap can be applied directly by immersion. The gun cap, which has been hot-dip coated with alloy and naturally cooled to 60-80°C, is directly immersed in the high-temperature resistant coating for 30-60 seconds. After taking it out, it can be dried in 2-3 minutes and put into production.

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