Spraying paint for RH furnace dip pipe lining and preparation method of spraying paint

Abstract

The invention discloses a spray coating for an RH (Ruhrstahl Heraeus) furnace dip pipe lining and a preparation method of the spray coating. The spray coating comprises certain components of magnesia aggregate, magnesium fine powder, chromium slag fine powder, an adhesive, a hardening agent and a sintering aid. The method comprises the following steps: putting the magnesia aggregate, the magnesium fine powder, the chromium slag fine powder, the adhesive, the hardening agent and the sintering aid into a stirrer, stirring for 3-5 minutes, and uniformly mixing, so as to obtain the spray coating with high erosion resistance and permeation resistance. According to the spray coating, the production cost of the existing RH spray coating is reduced, the erosion resistance and the permeation resistance of the RH spray coating are improved, and the application of the chromium slag with high additional value is expanded; the method is convenient to prepare, and the required spray coating can be obtained by stirring and uniformly mixing.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization, and in particular to a spray coating material for RH furnace immersion tube lining and a preparation method thereof. Background Art

[0002] The RH furnace is a kind of molten steel refining equipment with vacuum argon blowing and cyclic degassing. It is mainly used to produce low-carbon, low-nitrogen and low-hydrogen steel. In recent years, the proportion of low-carbon steel in the market has gradually increased, and the number of RH furnace applications has increased. The metallurgical chemical reaction of RH vacuum refining is mainly completed in the RH vacuum chamber. The middle and top of the vacuum chamber do not directly contact the molten steel. The parts with serious melting loss are mainly in the lower part of the vacuum chamber and the immersion tube. At present, the service life of the RH furnace immersion tube is relatively low, and the short service life affects the efficiency of the entire refining and degassing. In order to ensure the smooth progress of production, if the immersion tube with melting loss is shut down for cold repair, the long cooling time is not good for the lining. Hot spraying is convenient to operate and is suitable for mechanized operation. It is easier to meet the needs of industrial production. Therefore, hot repair is a simple and efficient way to increase the service life of the immersion tube.

[0003] Chromium slag is a byproduct of the aluminothermic chromium smelting process. Its main components are aluminum oxide, chromium oxide, and sodium oxide. Due to the environmental pollution problem of hexavalent chromium, the treatment of chromium slag is also a difficult problem. At present, a large amount of chromium slag not only occupies precious land resources but also poses a hidden danger of polluting the surrounding environment and groundwater. Therefore, how to effectively utilize the chromium slag of industrial waste with high added value is an urgent issue that needs to be solved. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a spray coating for the lining of the RH furnace immersion tube and a preparation method thereof. The spray coating reduces the production cost of the existing RH spray coating, improves the corrosion resistance and penetration resistance of the RH spray coating, and expands the application of high value-added chromium slag; the method is easy to prepare, and the required spray coating can be obtained by stirring and mixing.

[0005] In order to solve the above technical problems, the spray coating material for the lining of the RH furnace immersion tube of the present invention includes 50-70wt% of magnesia aggregate, 10-32wt% of magnesia fine powder, 5-10wt% of chromium slag fine powder, 3-8wt% of adhesive, 1-3wt% of hardener and 2-5wt% of sintering aid.

[0006] Furthermore, the adhesive is Vero mud, the hardener is slaked lime, and the sintering aid is sodium hexametaphosphate.

[0007] Furthermore, the median diameter of the chromium slag fine powder is less than 0.074 mm.

[0008] Furthermore, the particle size of the magnesia aggregate ranges from 0 to 1 mm and from 1 to 3 mm.

[0009] Furthermore, the magnesia fine powder is fused magnesia fine powder or light-burned magnesia fine powder with a MgO content of 96 wt %, and the median diameter of the fused magnesia fine powder or light-burned magnesia fine powder is less than 100 μm.

[0010] A preparation method based on the above-mentioned spray coating comprises the following steps: putting magnesia aggregate, magnesia fine powder, chromium slag fine powder, adhesive, hardener and sintering aid into a mixer and stirring for 3 to 5 minutes to obtain a highly erosion-resistant and anti-penetration spray coating. Since the spray coating material for the RH furnace immersion tube lining and the preparation method thereof of the present invention adopt the above-mentioned technical scheme, that is, the spray coating material comprises a certain component of magnesia aggregate, magnesia fine powder, chromium slag fine powder, adhesive, hardener and sintering agent; the method puts magnesia aggregate, magnesia fine powder, chromium slag fine powder, adhesive, hardener and sintering agent into a mixer and stirs for 3 to 5 minutes to mix well, and then obtains a highly erosion-resistant and permeation-resistant spray coating material. The spray coating material reduces the production cost of the existing RH spray coating material, improves the erosion-resistant and permeation-resistant performance of the RH spray coating material, and expands the application of high value-added chromium slag; the method is easy to make, and the desired spray coating material can be obtained by stirring and mixing well. DETAILED DESCRIPTION

[0011] Example 1 Take 55wt% of magnesia as aggregate, 30wt% of magnesia fine powder, 5wt% of chromium slag fine powder, 5wt% of adhesive, 2wt% of hardener and 3wt% of sintering aid as matrix material; put the above aggregate and matrix material into a mixer, stir for 3-5 minutes, and after mixing, you can get RH spray coating with high corrosion resistance and penetration resistance.

[0012] The highly erosion-resistant and permeation-resistant RH spray coating prepared in this embodiment was tested to have a flexural strength of 1.37 MPa, a compressive strength of 7.7 MPa, an apparent porosity of 28.8%, and a bulk density of 2.35 g / cm at 110°C. 3 After heat treatment at 1100℃×3h, its flexural strength is 0.79MPa, compressive strength is 1.72MPa, apparent porosity is 34.17%, and bulk density is 2.30g / cm 3 , linear change rate is -0.11%; after heat treatment at 1550℃×3h, its flexural strength is 4.5MPa, compressive strength is 12.43MPa, apparent porosity is 25.97%, and bulk density is 2.59g / cm 3 , the line change rate is -2.6%.

[0013] Example 2 55wt% of magnesia is used as aggregate, 28wt% of magnesia fine powder, 7wt% of chromium slag fine powder, 5wt% of adhesive, 2wt% of hardener and 3wt% of sintering aid are used as matrix material; the above aggregate and matrix are put into a mixer and stirred for 3-5 minutes, and after mixing, a highly erosion-resistant and anti-penetration RH spray coating is obtained.

[0014] The highly erosion-resistant and permeation-resistant RH spray coating prepared in this embodiment was tested to have a flexural strength of 1.30 MPa, a compressive strength of 5.7 MPa, an apparent porosity of 29.0%, and a bulk density of 2.32 g / cm at 110°C. 3 After heat treatment at 1100℃×3h, its flexural strength is 0.69MPa, compressive strength is 1.63MPa, apparent porosity is 34.5%, and bulk density is 2.25g / cm 3 , linear change rate is -0.03%; after heat treatment at 1550℃×3h, its flexural strength is 3.9MPa, compressive strength is 11.24MPa, apparent porosity is 26.03%, and bulk density is 2.56g / cm 3 , the line change rate is -1.72%.

[0015] Example 3 Take 55wt% of magnesia as aggregate, 32wt% of magnesia fine powder, 3wt% of chromium slag fine powder, 5wt% of adhesive, 2wt% of hardener and 3wt% of sintering aid as matrix material; put the above aggregate and matrix into a mixer, stir for 3-5 minutes, and after mixing, you can get the RH spray coating with high corrosion resistance and penetration resistance.

[0016] The highly erosion-resistant and permeation-resistant RH spray coating prepared in this embodiment was tested to have a flexural strength of 1.32 MPa, a compressive strength of 7.5 MPa, an apparent porosity of 28.3%, and a bulk density of 2.37 g / cm at 110°C. 3 After heat treatment at 1100℃×3h, its flexural strength is 0.71MPa, compressive strength is 1.68MPa, apparent porosity is 34.30%, and bulk density is 2.28g / cm 3 , linear change rate is -0.06%; after heat treatment at 1550℃×3h, its flexural strength is 4.2MPa, compressive strength is 12.1MPa, apparent porosity is 26.00%, and bulk density is 2.57g / cm 3 , the line change rate is -1.86%.

[0017] Chromium oxide exhibits excellent slag resistance and penetration resistance in refractory materials, but in order to prevent Cr 6+Pollution, chromium-containing refractory materials are included in the restricted category. However, there are literature studies reporting that the chromium oxide raw material is in the magnesium material matrix, and there is no hexavalent chromium pollution problem in the steel environment, and the conventional hot spraying immersion pipe generally uses magnesium calcium, magnesium and aluminum magnesium repair materials. Therefore, adding chromium slag to this spray coating is beneficial to the efficient utilization of chromium and the spray coating itself. The main components of chromium slag are aluminum oxide, chromium oxide and sodium oxide, among which aluminum oxide can react with the magnesium matrix to form magnesium aluminum spinel, chromium oxide and magnesium oxide to form magnesium chromium spinel, and the matrix of the double spinel solid phase structure can improve the corrosion resistance and permeability resistance of the magnesium material. In addition, the spray coating requires rapid sintering. When conventional raw materials are used, additional additives such as quick-dissolving sodium silicate are added for rapid sintering. Adding chromium slag to the magnesium RH spray coating, the evenly dispersed sodium oxide component contained in the chromium slag becomes a beneficial component in the spray coating system, which helps to accelerate the reaction of aluminum oxide and chromium oxide with magnesium oxide and promote the sintering of the system. Moreover, the slag material used in smelting chromium is considered industrial waste and its price is much lower than that of alumina and chromium oxide raw materials.

[0018] The spray coating reduces the production cost of existing RH spray coatings, improves the corrosion resistance and penetration resistance of RH spray coatings, and expands the application of high value-added chromium slag. The raw materials used in the spray coating are easy to obtain and low in price. The preparation process is simple and the production efficiency is high. When used, the semi-dry spraying process is used for construction, which is easy to realize industrial production.

Claims

1. A spray coating for RH furnace immersion tube lining, characterized in that: The invention comprises 50-70wt% of magnesia aggregate, 10-32wt% of magnesia fine powder, 5-10wt% of chromium slag fine powder, 3-8wt% of adhesive, 1-3wt% of hardener and 2-5wt% of sintering aid.

2. The spray coating material for RH furnace immersion pipe lining according to claim 1, characterized in that: The adhesive is Vero mud, the hardener is slaked lime, and the sintering aid is sodium hexametaphosphate.

3. The spray coating material for RH furnace immersion pipe lining according to claim 1, characterized in that: The median diameter of the chromium slag fine powder is less than 0.074 mm.

4. The spray coating material for RH furnace immersion pipe lining according to claim 1, characterized in that: The particle size of the magnesia aggregate ranges from 0 to 1 mm and from 1 to 3 mm.

5. The spray coating material for RH furnace immersion pipe lining according to claim 1, characterized in that: The magnesia fine powder is fused magnesia fine powder or light-burned magnesia fine powder with a MgO content of 96wt%, and the median diameter of the fused magnesia fine powder or light-burned magnesia fine powder is less than 100μm.

6. A method for preparing the spray coating according to any one of claims 1 to 5, characterized in that: Put magnesia aggregate, magnesia fine powder, chromium slag fine powder, adhesive, hardener and sintering aid into a mixer and stir for 3 to 5 minutes to obtain a highly erosion-resistant and anti-penetration spray coating.