Protective coating technology for inhibiting generation of wall-climbing titanium

Abstract

The invention relates to the technical field of metal materials, and provides a protective coating technology for inhibiting generation of wall-climbing titanium, a coating is applied to the inner surface of a titanium production reactor and is used for inhibiting generation of wall-climbing titanium, and the protective coating technology comprises the following steps: pretreating the inner surface of the reactor; applying a coating, wherein the raw material of the coating comprises Y2O3; a heat treatment curing process; and cooling. The method can reduce the generation amount of wall-climbing titanium, improve the rate of certified sponge titanium and prolong the service life of equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and more specifically, to a protective coating technology for inhibiting the formation of wall-climbing titanium. Background Art

[0002] Currently, in the industrial production of sponge titanium, the Kroll process is usually adopted, in which titanium tetrachloride is reduced by liquid magnesium at high temperature to produce metallic titanium and magnesium chloride by-products. The reaction is carried out in a closed high-temperature resistant metal reactor, and the temperature is usually controlled between 800 and 950 °C. During the reduction process, the chemical reaction is a strong exothermic reaction, with significant local temperature fluctuations. In addition, the gas-phase diffusion of titanium tetrachloride and the liquid surface fluctuation are remarkable, which easily causes the reduction product (titanium) to deposit along the reactor wall, forming "wall-climbing titanium".

[0003] The formation of wall-climbing titanium not only reduces the recovery rate of titanium, but also increases the intensity of subsequent slag cleaning operations, equipment wear, and even causes local reactor wall expansion and deformation, shortening the equipment life. Traditional measures to inhibit wall-climbing titanium, such as optimizing the feeding speed, controlling the reaction temperature field, and adjusting the gas flow field, although having certain effects, have limited functions and cannot fundamentally eliminate the tendency of titanium to adhere to the metal reactor wall.

[0004] Chinese Patent CN112323011A discloses a plasma spraying process method applicable to VW75 rare earth magnesium alloy. First, the surface of the VW75 rare earth magnesium alloy substrate is cleaned with acetone, compressive stress is applied to cause a 1-10% distortion of the crystal lattice, and sandblasting pretreatment is carried out; the grit or dust adhering to the roughened surface is blown off with dry compressed air, and no reflective bright spots are observed on the sandblasted surface from all angles; within 1-3 hours after sandblasting, an adhesive layer is sprayed on the roughened substrate surface, and the material of the adhesive layer is NiCrAlY alloy powder; a surface layer is sprayed on the adhesive layer, and the surface layer is prepared by an atmospheric plasma spraying process, and the material of the surface layer is nano-particle agglomerated yttrium partially stabilized zirconia powder; after spraying, the sample is slowly cooled to room temperature to reduce internal stress. A coating with a higher heat-resistant temperature can be prepared on the surface of VW75 magnesium alloy, and for insulating samples with a large thickness, the overall performance can be steadily improved. However, this method is not the same as the process of the present invention, and this coating is not suitable for inhibiting the formation of wall-climbing titanium.

[0005] Chinese Patent CN115895311A discloses a protective coating applicable to co-firing high-sulfur and high-alkali coal and a method for preparing the coating, which consists of a base coating and a surface coating, and also discloses a method for preparing a double-layer protective coating from the protective coating. The invention aims to solve the problem of corrosion and coking on the heat transfer surface of the boiler. Although yttrium oxide is contained in the raw materials, its process method and purpose effects are different from those of the present invention.

[0006] Therefore, a protective coating technology for inhibiting the formation of wall-climbing titanium is needed to meet the actual production requirements. Summary of the Invention

[0007] The object of the present invention is to provide a protective coating technology for inhibiting the formation of wall-climbing titanium, which is specifically applied to the preparation and application method of an anti-titanium adhesion coating on the inner wall of a reactor during the production process of titanium sponge, so as to reduce the amount of wall-climbing titanium generated, improve the yield rate of high-quality titanium sponge, and extend the service life of the equipment.

[0008] To achieve the above object, the present invention provides a protective coating technology for inhibiting the formation of wall-climbing titanium. The technical solution of the present invention is realized as follows:

[0009] A protective coating technology for inhibiting the formation of wall-climbing titanium, the coating is applied on the inner surface of a titanium production reactor to inhibit the formation of wall-climbing titanium, and includes the following steps:

[0010] S1: Pretreatment of the inner surface of the reactor;

[0011] S2: Applying the coating, the coating raw materials include Y2O3;

[0012] S3: Heat treatment and curing process;

[0013] S4: Cooling treatment.

[0014] Through the present invention, a stable, dense, and excellent anti-titanium adhesion protective layer can be formed on the inner wall of the reactor. By utilizing its low wettability and chemical inertness, it blocks the contact between the product titanium and the metal wall, effectively prevents the deposition of titanium on the wall surface, significantly reduces the amount of wall-climbing titanium generated, thereby improving the recovery rate of titanium, improving the thermal field distribution of the reduction system, and extending the service life of the equipment.

[0015] Further, in the step S2, the coating raw materials further include MgO. After adding MgO, the mechanical strength of the coating is improved, taking into account the anti-titanium adhesion performance of Y2O3 and the heat shock resistance performance of MgO.

[0016] Further, in the step S2, the coating is a double-layer structure: Y2O3 is the surface layer and MgO is the bottom layer. This structural form is stable, can effectively prevent the adhesion and diffusion of titanium, improve the overall bonding force, and has the characteristics of easy removal for reprocessing and easy repair.

[0017] Further, in the step S2, the coating is a sandwich structure: Y2O3 is the surface layer and the bottom layer, and MgO is the intermediate layer. The surface layer prevents the adhesion and diffusion of titanium, the intermediate layer prevents the coating from cracking and has strong impact resistance, and the bottom layer provides a further buffering effect.

[0018] Further, in the step S2, the coating raw material is 99.9% Y2O3 powder. The anti-titanium adhesion material uses Y2O3 to ensure its stable structure in the high-temperature reaction environment. At the same time, Y2O3 has the characteristics of low wettability, high-temperature stability, and chemical inertness.

[0019] Further, in the step S2, the coating application position is on the upper half of the inner wall of the reactor. During production, wall-climbing titanium is likely to be generated in this area, and the coating is applied to the area where wall-climbing titanium is concentrated.

[0020] Further, in the step S2, the coating thickness is 50 - 200 μm. This coating thickness results in a dense coating structure, no pores, and is not easily detached.

[0021] Further, in the step S2, the coating is applied using thermal spraying or plasma spraying processes to meet the requirements of the reactor structure and coating uniformity.

[0022] Further, in the step S3, first heat to 800 - 900 °C and hold for 10 - 14 hours, then raise the temperature to 900 - 1000 °C and hold for 2 - 6 hours to ensure that the internal stress of the material is effectively released and at the same time promote the full progress of the chemical reaction. This method can effectively avoid material cracking or performance deterioration caused by sudden temperature changes, thereby improving product quality and process stability.

[0023] Further, in the step S4, first use indirect water cooling for 4 - 8 hours, then use direct water cooling for 2 - 6 hours. By slowly reducing the temperature, it promotes coating densification and eliminates internal stress, and improves the adhesion strength.

[0024] Compared with the prior art, the anti-wall-climbing titanium generation protective coating technology of the present invention has the following advantages:

[0025] ① Significantly reduce the amount of wall-climbing titanium generated, reduce the thickness of the titanium deposition layer on the reactor wall by more than 60%, and reduce the manual cleaning intensity.

[0026] ② The low wettability of the coating is beneficial to the uniform distribution of the temperature field and the thermal control optimization of the reaction process. Combined with on-line monitoring and control, it improves product quality and the qualified rate of titanium sponge.

[0027] ③ It is not easily corroded and deformed, effectively prevents the direct contact between the product titanium and the steel matrix, reduces the risk of reactor wall corrosion and deformation, and extends the service life of the reactor.

[0028] ④ The coating has good stability and effectively supports the coordinated operation of the automatic feeding and temperature control systems. Description of the Drawings

[0029] Figure 1Schematic structural diagram of the coating applied to the inner wall of the reduction reactor according to Embodiment 1 of the present invention;

[0030] Figure 2 Schematic diagram of the position where the coating in the reactor according to Embodiment 1 of the present invention is added.

[0031] Description of reference numerals:

[0032] 1. Reactor; 2. Coating; 3. Product titanium deposition; 4. Furnace shell; 11. Reactor flange. Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0034] The following specifically describes a protective coating technology for suppressing the generation of wall-climbing titanium in an embodiment of the present invention with reference to the drawings.

[0035] Embodiment 1

[0036] A protective coating technology for suppressing the generation of wall-climbing titanium, wherein the coating 2 is applied to the inner surface of the titanium production reactor 1 to suppress the generation of wall-climbing titanium, and includes the following steps:

[0037] S1: Pretreatment of the inner surface of the reactor 1.

[0038] The titanium production reactor 1 is usually made of stainless steel or alloy steel. The inner wall of the reactor 1 is subjected to sandblasting or mechanical grinding treatment. The original scale, carbon deposits, residues, etc. are removed to improve the surface roughness of the substrate, so as to enhance the mechanical bonding force of the coating 2. The surface roughness of the substrate is preferably Ra = 2 - 4 μm. The sandblasting treatment preferably uses Al2O3 sand with a particle size of 60 - 120 μm. An interfacial reaction will occur between the Y2O3 coating and Al2O3 at high temperature, and the reaction product is Y3Al5O 12 , enabling good bonding between layers and being not easily peeled off and broken.

[0039] S2: Apply the coating 2.

[0040] The raw material of coating 2 includes Y2O3, preferably industrial grade 99.9% high purity Y2O3 powder with an average particle size of 5~25μm. Y2O3 can withstand 2000°C in an inert or reducing atmosphere, and its chemical stability is significantly better than Al2O3, ZrO2, etc. The anti-titanium adhesion material uses Y2O3 to ensure that it maintains a stable structure in a high-temperature reaction environment. At the same time, Y2O3 has the characteristics of low wettability, high-temperature stability and chemical inertness. For molten metal, Y2O3 coating 2 especially exhibits excellent non-wettability. Experiments show that the contact angle between Y2O3 and high-temperature metal melt is usually greater than 140°, and in some cases can reach 157°, which indicates that its surface has a significant repelling effect on metal liquid, and this non-wetting property is used to effectively prevent titanium from adhering to and diffusing on the inner wall of reactor 1.

[0041] The raw materials of coating 2 may also include MgO, and Y2O3 and MgO powder are mixed and sprayed in a mass ratio (such as 7:3, 4:1, 3:1) to form a dual-phase coating. On the one hand, MgO is also a high melting point metal and is stable at high temperatures. Y2O3 and MgO will not undergo violent chemical reactions at high temperatures and can coexist to form a stable solid solution system. On the other hand, the thermal expansion coefficients of Y2O3 and MgO are close, and the thermal stress matching is good after the composite, and the coating 2 will not be damaged due to cyclic heating. After adding MgO, the mechanical strength of coating 2 is improved, taking into account the anti-titanium adhesion performance of Y2O3 and the heat shock resistance of MgO.

[0042] Coating 2 can be sprayed in a single layer or in a composite multilayer structure. The composite multilayer structure includes the following two structural forms:

[0043] Coating 2 is a double-layer (gradient layer) structure, with Y2O3 as the surface layer and MgO as the bottom layer. This structure is stable, can effectively prevent the adhesion and diffusion of titanium, improve the overall bonding strength, and has the characteristics of easy removal, reprocessing and repair.

[0044] The coating 2 is a sandwich structure, a Y2O3-MgO-Y2O3 sandwich structure, Y2O3 is the surface layer and the bottom layer, and MgO is the middle layer. The surface layer prevents the adhesion and diffusion of titanium, the sandwich prevents the coating 2 from cracking and has strong impact resistance, and the bottom layer provides a further buffering effect.

[0045] At the same time, the multi-layer structure of the coating 2 produces a synergistic effect, which can improve the ductility of the coating 2, reduce the possibility of crack propagation, and also improve the fatigue resistance of the coating 2 and extend the fatigue life.

[0046] like Figure 2As shown, the application position of the coating 2 is on the upper half of the inner wall of the reactor 1 below the reactor flange 11. Preferably, it is in the annular area of the inner wall of the reactor 1, 500 cm to 1600 cm from the lower edge of the reactor flange 11. During production, wall-climbing titanium is likely to be generated in this area, and the coating 2 is applied to the area where wall-climbing titanium is concentrated. The remaining area of the inner wall is subjected to titanium infiltration treatment by spraying titanium powder.

[0047] The coating 2 is uniformly applied to the inner wall by thermal spraying or plasma spraying processes to meet the requirements of the structure of the reactor 1 and the uniformity of the coating 2. Preferably, the yttrium oxide coating 2 is prepared under the condition of Ar / H2 or Ar / H e ion gas, which can help the powder to melt and enhance the density and corrosion resistance of the coating 2. Preferably, the coating thickness is 50~200 μm. Through experiments, the coating 2 with this coating thickness has a dense structure, no pores and is not easy to fall off.

[0048] During the application of the coating 2, an intelligent induction device is equipped to monitor the temperature and pressure changes in real time, so as to ensure the reliability of the coating 2 application. The intelligent induction device is not only used to monitor the temperature change, but also has an abnormal alarm function. During the operation, once an abnormality in the system is detected, the intelligent induction device will promptly issue an alarm to remind the operator and take corresponding measures, thereby effectively improving the stability of the process.

[0049] S3: Heat treatment and curing process.

[0050] The heat treatment and curing process adopts a method of segmented temperature increase and heat preservation control. During the heat treatment and curing process, the temperature is gradually increased according to the predetermined stages, and a specific heat preservation time is set at each stage to ensure the effective release of the internal stress of the material and promote the full progress of the chemical reaction. This method can effectively avoid the cracking or performance deterioration of the material caused by sudden temperature changes, thereby improving the product quality and process stability.

[0051] Specifically, after the application of the coating 2 is completed, the reactor 1 is evacuated to remove waste gas, and the coating application area of the reactor 1 is heated to 800~900 °C. During the reduction process of sponge titanium production, the temperature in the furnace is controlled to reach about 860 °C. This temperature range is set to make the coating 2 adapt to the temperature of normal production. Then, argon gas is filled to ensure positive pressure in the reactor 1 and heat is preserved for the first preset time to promote the physical / chemical combination between the coating 2 and the substrate. The first preset time is 10~14 hours, preferably 12 hours. Further, the temperature is increased to 900~1000 °C and heat is preserved for the second preset time to improve the thermal stability and peel strength of the coating 2. The second preset time is 2~6 hours, preferably 2 hours.

[0052] S4: Cooling treatment.

[0053] The coating 2 is cooled by a slow cooling process. By slowly reducing the temperature, the densification of the coating 2 is promoted and internal stress is eliminated, thereby improving the adhesion strength. Preferably, indirect water cooling is first used for a third preset time, and then direct water cooling is used for a fourth preset time. During the cooling process, argon gas is filled in the reactor 1 to maintain a positive pressure. The third preset time is 4 to 8 hours, preferably 6 hours; the fourth preset time is 2 to 6 hours, preferably 4 hours.

[0054] S5: Regular inspection and maintenance.

[0055] During the production break, the integrity of the coating 2 is detected using ultrasonic waves or a coating 2 thickness gauge. In case of damage, it is promptly repaired by spraying to ensure the continuous stability of the protective ability of the coating 2. The process state data of the operation of adding the coating 2 is input into the automated DCS control system to achieve dynamic maintenance scheduling.

[0056] The technology of the present invention can form a stable, dense, and excellent anti-titanium adhesion performance protective layer on the inner wall of the reactor 1. By utilizing its low wettability and chemical inertness, the contact between the product titanium and the metal wall is blocked, effectively preventing the deposition of titanium on the wall surface, significantly reducing the generation amount of wall-climbing titanium, thereby improving the titanium recovery rate, improving the thermal field distribution of the reduction system, and extending the service life of the equipment.

[0057] The coating 2 technology of the present invention has been experimentally applied in the reduction and distillation reaction device. The experimental results show that this technology exhibits significant superiority compared with the traditional sponge titanium production process.

[0058] First, the titanium wetting angle on the surface of the coating 2 increases significantly, reducing the probability of titanium nucleation and adhesion on the wall surface; according to the actual measurement data, the thickness of the titanium deposition layer on the reactor wall is reduced by more than 60%, and the wall-climbing titanium after the product is taken out of the furnace is significantly reduced, reducing the cleaning workload of the reactor 1. Second, the low wettability of the coating 2 is beneficial to the uniform distribution of the temperature field, reducing by-products and increasing the proportion of high-quality products, having good economic value. Third, after the present invention is applied to production, no obvious corrosion and expansion deformation are found on the inner wall of the reactor 1, and the integrity rate of the coating 2 exceeds 95%, effectively preventing the direct contact between the product titanium and the metal matrix of the reactor 1, reducing the risk of reactor wall corrosion and deformation, and extending the service life of the reactor 1. Fourth, the coating 2 has good stability and effectively supports the coordinated operation of the automated feeding and temperature control systems.

[0059] It should be noted that all the terms indicating direction and position in the present invention, such as: "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", "top", "bottom", "tail end", "head end", "center", etc., are only used to explain the relative position relationship and connection situation between components in a certain specific state, and are only for the convenience of describing the present invention, rather than requiring the present invention to be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0060] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope defined by the claims.

Claims

1. A protective coating technology for suppressing the generation of wall-climbing titanium, characterized in that, The coating (2) is applied to the inner surface of the titanium production reactor (1) to inhibit the formation of wall-climbing titanium, and includes the following steps: S1: Pretreatment of the inner surface of the reactor (1); S2: Applying the coating (2), the raw materials of the coating (2) including Y2O3; S3: Heat treatment and curing process; S4: Cooling treatment.

2. The protective coating technology according to claim 1, wherein, In the step S2, the raw materials of the coating (2) further include MgO.

3. The protective coating technology according to claim 2, characterized in that, In the step S2, the coating (2) has a double-layer structure: Y2O3 is the surface layer and MgO is the bottom layer.

4. The protective coating technology according to claim 2, wherein, In the step S2, the coating (2) has a sandwich structure: Y2O3 is the surface layer and the bottom layer, and MgO is the intermediate layer.

5. The protective coating technology according to any one of claims 1-4, characterized in that, In the step S2, the raw materials of the coating (2) are 99.9% Y2O3 powder with an average particle size of 5 - 25 μm.

6. The protective coating technology according to claim 1, wherein In the step S2, the application position of the coating (2) is on the upper half of the inner wall of the reactor (1).

7. The protective coating technology according to claim 1, characterized in that, In the step S2, the thickness of the coating (2) is 50 - 200 μm.

8. The protective coating technology according to claim 1, wherein In the step S2, the coating (2) is applied by thermal spraying or plasma spraying process.

9. The protective coating technology according to claim 1, characterized in that, In the step S3, it is first heated to 800 - 900 °C and kept warm for 10 - 14 hours, and then the temperature is raised to 900 - 1000 °C and kept warm for 2 - 6 hours.

10. The protective coating technology according to claim 1, wherein In the step S4, it is first indirectly water-cooled for 4 - 8 hours, and then directly water-cooled for 2 - 6 hours.

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