Wear-resistant, high-temperature-oxidation-resistant and anti-deformation small-caliber composite pipe and preparation method thereof

Abstract

The invention discloses a wear-resistant, high-temperature-oxidation-resistant and anti-deformation small-caliber composite pipe and a preparation method thereof, and belongs to the technical field of composite pipe materials. The composite pipe comprises an inner layer (Al2O3 ceramic), a middle layer pipe (310S or 314 stainless steel), a protective layer (Gr2O3 or SiO2), a heat insulation air gap layer and an anti-deformation pipe. And the combination of wear resistance, high-temperature oxidation resistance and deformation prevention functions is realized through the cooperation of multiple layers of structures. The inner layer is prepared by adopting a self-propagating self-weight separation process, the Vickers hardness is greater than or equal to 1500HV, and the wear resistance is excellent; the middle-layer pipe is resistant to high temperature and provides structural support, and a Gr2O3 or SiO2 protective layer is formed on the outer layer of the middle-layer pipe in situ to enhance the high-temperature oxidation resistance; 0.1-1 mm heat insulation air gap layers are reserved between the middle layer pipe and the anti-deformation pipes and between the multiple layers of anti-deformation pipes to slow down heat transfer; the anti-deformation pipe is of a segmented structure (each segment is 100-500 mm), the anti-deformation pipe is dip-coated with high-temperature-resistant paint, segments are distributed in a staggered mode at intervals of 0.2-10 mm telescopic gaps, the anti-deformation pipe is fixed through plug welding, thermal stress is relieved, and the functions of abrasion resistance, high-temperature oxidation resistance and deformation prevention are cooperatively achieved. And the deflection resistance is enhanced. The composite pipe is suitable for high-temperature and high-wear-resistance working conditions at the temperature of 1000-1350 DEG C, excellent in comprehensive performance and stable in structure, and can be widely applied to industries such as metallurgy and chemical engineering.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite pipes, and specifically relates to a composite pipe suitable for high-temperature and high-wear working conditions, and in particular to a multi-layer small-diameter composite structure pipe with wear resistance, high-temperature oxidation resistance and deformation resistance, and a preparation method thereof. The pipe can be widely used in metallurgy, chemical industry, electric power, mining and other industries in high-temperature and high-wear working conditions as a material conveying pipeline, furnace connecting pipe, coal injection pipe and other scenarios. Background Art

[0002] In industrial production, pipes exposed to high temperature and high wear conditions face multiple performance challenges: on the one hand, the conveying medium (such as high-temperature slag, slurry, blast furnace coal injection, etc.) will cause severe wear on the inner wall of the pipe, resulting in pipe wall thinning and leakage; on the other hand, high temperature environments (above 1000°C) will accelerate high-temperature oxidation of the pipe and reduce structural strength; in addition, uneven thermal expansion under high temperature causes pipe deformation (such as bending, bulging, and cracking), which directly affects system safety and service life.

[0003] Existing pipes made of a single material or simple composite pipes struggle to meet these comprehensive requirements. While stainless steel pipes (such as 310S) offer some high-temperature resistance, they oxidize rapidly at temperatures above 1000°C and exhibit poor wear resistance. They are prone to failure due to wear and oxidation over long periods of use and are also susceptible to deformation and warping in high-temperature environments. Ceramic pipes (such as Al2O3 ceramics) offer excellent wear resistance, but they are brittle, have poor impact resistance, are difficult to connect to metals, and are prone to fracture due to thermal stress at high temperatures. Traditional composite pipes (such as stainless steel-ceramic composite pipes) often utilize a monolithic outer layer wrapping structure. The large difference in thermal expansion coefficients between the outer and inner layers easily generates interfacial stress at high temperatures, leading to delamination and overall deformation. Furthermore, prolonged exposure to high temperatures results in severe oxidation of the outer surface. Furthermore, these pipes are susceptible to deformation and warping at high temperatures. Currently, composite pipes are available that combine multiple layers of high-temperature-resistant steel pipes with ceramic composite pipes. However, because the sustained high-temperature resistance of these multilayered high-temperature-resistant steel pipes is limited to below 1100°C, they do not fundamentally address the issues of high-temperature oxidation and thermal deformation.

[0004] Therefore, developing a composite pipe that achieves synergistic effects of wear resistance, high-temperature oxidation resistance, and deformation resistance through structural optimization has become the key to solving the above technical difficulties. Summary of the Invention

[0005] (1) Purpose of the invention

[0006] The purpose of the wear-resistant, high-temperature oxidation-resistant and deformation-resistant small-diameter composite pipe (hereinafter referred to as "composite pipe") of the present invention is to overcome the defects of the composite pipe in the prior art, such as single performance and easy deformation under high-temperature and high-wear conditions, and to provide a small-diameter composite pipe (diameter DN10-DN40) with stable structure and excellent comprehensive performance and a preparation method thereof. Through the coordinated design of multi-layer structure and process, an organic combination of wear resistance, high-temperature oxidation resistance and deformation resistance is achieved.

[0007] (2) Technical solution

[0008] To achieve the above objectives, the present invention provides a small-diameter composite pipe with wear resistance, high-temperature oxidation resistance, and deformation resistance. The pipe comprises five components: an inner layer (Al2O3 ceramic), an intermediate layer, a protective layer, a heat-insulating air gap layer, and an anti-deformation pipe. The anti-deformation pipe can be a single layer, or two or more layers can be added to the other four components. The details are as follows:

[0009] The inner layer (Al2O3 ceramic) is produced using a self-propagating gravity separation process. With a Vickers hardness exceeding 1500 HV and wear resistance 10-20 times that of stainless steel, the ceramic effectively resists abrasion from the conveying medium. The self-propagating process utilizes an exothermic chemical reaction to melt the ceramic precursor and bond it to the inner surface of the intermediate layer tube. The bond strength can exceed 100 MPa, preventing the ceramic layer from shedding.

[0010] The intermediate layer is made of 314 or 310S stainless steel. The presence of Gr and Ni elements allows for a stable oxide layer to form at high temperatures, extending the service temperature to over 1200°C. This layer offers superior oxidation resistance, and both possess excellent high-temperature strength. The close integration of the intermediate layer and the inner layer (Al203 ceramic) enhances overall rigidity (bending strength is over 30% higher than that of stainless steel alone). The intermediate layer provides basic structural support.

[0011] The protective layer is a high-temperature in-situ protective layer formed by the self-propagating reaction at a high temperature of about 2200℃, in which Gr2O3 (1-5μm) is formed on the outer layer of the 310S tube and SiO2 (3-8μm) is formed on the outer layer of the 314 tube, which significantly improves the high-temperature oxidation resistance.

[0012] A 0.1-1mm gap is left between the outer surface of the middle layer tube and the inner surface of the anti-deformation tube, forming a heat-insulating air gap layer. If the anti-deformation tube is two-layered or multi-layered, then a 0.1-1mm gap is also left between the inner and outer layers of the anti-deformation tube, also forming a heat-insulating air gap layer. This serves to slow down the temperature transfer between each layer of the anti-deformation tube and the middle layer tube, significantly improving the high-temperature oxidation resistance and high-temperature anti-deformation performance of the middle layer tube and each layer of the anti-deformation tube. Among them, the base of each section of the anti-deformation tube is 310S or 314 stainless steel tube, and the entire section is dipped in a high-temperature resistant heat-insulating coating (such as ZS-322 coating, which can stably operate at high temperatures of around 2000°C).

[0013] The anti-deformation tube has a segmented structure, and each segment is selected between 100-500mm in length. The expansion gap is maintained between 0.2-10mm (selected according to the length, thickness and other technical requirements of the composite tube). If two or more layers are nested, the expansion gaps are maintained at the same value of 0.2-10mm, but the expansion gaps of each layer should be staggered and cannot be located on the same axis. Segmented nesting can provide local support and enhance the anti-flexure capacity of the composite tube. Symmetrical plug welding or multi-point uniform plug welding in the middle of each segment fixes the anti-deformation tube to the middle layer tube or each layer of anti-deformation tube, ensuring that the middle layer tube and the anti-deformation tube or each anti-deformation tube are subjected to synchronous force, avoiding thermal expansion differences and reducing warping caused by thermal stress. The overall structure has the ability to insulate, resist high-temperature oxidation, and prevent high-temperature deformation.

[0014] The synergistic effect of the above structures significantly improves the comprehensive performance of the composite pipe, such as wear resistance, high temperature oxidation resistance, and deformation resistance, in a high temperature environment above 1200°C.

[0015] The present invention also provides a method for preparing a composite pipe, comprising the following steps:

[0016] Step 1: Preparation of inner and middle layer tubes

[0017] Material selection: Select appropriate 310S and 314 stainless steel pipes as the intermediate layer pipes according to market and technical requirements, and use ultrasonic cleaning (cleaning agent is 5% NaOH solution, temperature 60℃, time 30min) to remove surface oil stains.

[0018] Inner layer preparation: The inner layer (Al2O3 ceramic) is prepared using a self-propagating gravity separation process, and the thermite ratio is appropriately adjusted to control the combustion temperature to around 2200°C. At the same time, the outer surface of the intermediate layer tube is naturally oxidized at high temperature to form a Gr2O3 or SiO2 protective layer.

[0019] Step 2: Assemble the anti-deformation tube

[0020] Preparation of anti-deformation tubes: Select 310S and 314 stainless steel tubes according to market and technical requirements (the inner diameter of the anti-deformation tube should be 0.1-1mm larger than the outer diameter of the middle layer tube to ensure clearance. For two or more layers of anti-deformation tubes, the inner diameter of the outer layer should also be 0.1-1mm larger than the outer diameter of the inner layer. The thickness of the anti-deformation tube should be between 2-3mm). Cut the tube into 100-500mm segments according to the length of the middle layer tube and technical requirements, and reserve 0.2-10mm expansion gaps between segments. If two or more layers are nested, the expansion gaps should retain the same gap value of 0.2-10mm, but the expansion gaps of each layer should be staggered and cannot be located on the same axis. (To avoid defects such as thermal cracking, folding, and bulging caused by thermal expansion and contraction due to temperature fluctuations)

[0021] Clean the anti-deformation pipes of each section with 5% NaOH solution at 60°C for 30 minutes to remove surface oil stains. Dip-coat the entire pipe with a high-temperature resistant heat-insulating coating (such as ZS322). The working temperature during dipping should be controlled between 10-70°C, and cooled to room temperature with natural air.

[0022] Fitting and Gap Control: The segmented anti-deformation tubes are fitted sequentially along the axial direction of the intermediate tube. A fusible ring (ring diameter = the size of the thermal insulation gap) is placed against the outer surface of the intermediate tube to control the gap. If the anti-deformation tube consists of two or more layers, each layer is fitted and gap controlled in the same manner, but one layer must be fitted and secured before the next layer is fitted. Graphite gaskets (gasket thickness = the size of the expansion gap) are placed at both ends of each anti-deformation tube segment to ensure uniform gaps. After fitting, a temporary fixture is used to secure the tubes to prevent slippage. (Note: Fusible rings can naturally melt at temperatures above 500°C. Graphite gaskets can naturally break during expansion and contraction.)

[0023] Step 3: Fix the anti-deformation tube

[0024] Plug welding process: Use CNC plug welding equipment (such as NBC-500) to symmetrically distribute two plug welding holes or evenly distribute multiple plug welding holes in the middle of each anti-deformation tube (the hole diameter is selected as Φ6-Φ10 according to the diameter of the outer tube): Welding parameters: current 80-150A (the thicker the outer layer, the greater the current), welding time 1-2S, shielding gas is Ar (flow rate is 15-20L / min), remove spatter after welding, and check whether the weld has pores or cracks.

[0025] (3) Beneficial effects

[0026] Compared with the prior art, the present invention has the following significant effects:

[0027] 1. Excellent comprehensive performance: the inner layer of Al2O3 ceramics achieves high wear resistance (wear loss ≤ 0.01g / h); the outer surface protective layer of the intermediate layer tube makes the high temperature oxidation weight loss rate ≤ 0.5g / m 2 .·h, the high-temperature oxidation resistance at around 1200℃ is significantly improved; the anti-deformation pipe is dipped in heat-insulating and high-temperature resistant thermal insulation coating as a whole and adopts a segmented structure design to ensure that the composite pipe does not deform under thermal shock at around 1200℃, meeting harsh working conditions.

[0028] 2. High structural stability; segmented fitting + plug welding + gap design + coating protection synergistically solve the problem of thermal expansion mismatch, with high interface bonding strength (≥100Mpa) and no risk of delamination; overall bending strength ≥300MPa, deflection ≤0.5mm / m (load 1000N). The anti-deformation tube is dipped in heat-insulating and high-temperature resistant thermal insulation coating. The high-temperature resistant metal oxides in the coating will produce lattice phase changes at high temperatures, resulting in changes in the coating's packing density, naturally forming a mesh vacuum grid that acts as a heat insulator to shield heat energy. The thermal conductivity can reach 0.035W / mk (measured when the coating is heated above 1000°C and cooled to 70°C)

[0029] 3. Good process economy: The self-propagating gravity separation process can simultaneously complete the preparation of the ceramic inner layer and the protective layer, without the need for additional high-temperature oxidation treatment. The plug welding process is simple and easy to operate, and can be used for batch production, with low manufacturing costs. The dip coating process is simple and convenient and is also suitable.

[0030] 4. Wide range of applications: The material of the intermediate layer tube and anti-deformation tube (310S or 314), ceramic thickness, layered and segmented length and other parameters can be selected according to working conditions. It is suitable for various occasions with temperatures of 1000-1350℃ and wear rate of 0.05-0.5g / h. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the structure of the present invention, the following description is made with reference to the accompanying drawings;

[0032] Figure 1 Schematic diagram of radial section of the composite tube of the present invention

[0033] Figure 2 A schematic diagram of the axial part of the composite tube of the present invention

[0034] In the figure: 1-intermediate layer tube, 2-inner layer (Al2O3 ceramic), 3-protective layer (Gr2O3, SiO2), 4-anti-deformation tube, 5-insulating air gap layer, 6-plug welding point Note: In the accompanying drawings, the inner surface of the intermediate tube 1 is an Al2O3 ceramic layer 2, and the outer surface is a Gr2O3 or SiO2 protective layer 3. The anti-deformation tubes 4 are respectively sleeved onto the outer sides of the intermediate tubes 1, with a thermal insulation air gap 5 between them. If the anti-deformation tubes 4 are sleeved in two or more layers, the outer diameter of the inner anti-deformation tube and the inner diameter of the outer anti-deformation tube also form a thermal insulation air gap 5. Plug welds 6 are symmetrically distributed (or evenly distributed at multiple points) across the center of the anti-deformation tube 4, securing the anti-deformation tube 4 to the intermediate tube 1 or to each layer of anti-deformation tube 4. DETAILED DESCRIPTION

[0035] The present invention is further described below by means of specific examples, but the present invention is not limited to these examples.

[0036] Embodiment: A composite pipe (coal injection gun) suitable for conveying pulverized coal in 1350°C wind-temperature metallurgical ironmaking.

[0037] Intermediate layer tube 1: 310S stainless steel tube, specification Φ27mm×3mm×1000mm (outer diameter×wall thickness×length), inner surface 2.5mm thick inner layer (Al2O3 ceramic) 2, outer surface formed with a 10μm thick protective layer (Gr2O3) 3 Anti-deformation tube 4: 314 stainless steel tube, specification: 32mm×2.2mm (outer diameter×inner wall); cut into 200mm long segments, with 2mm expansion joints between segments; 0.3mm gap with intermediate layer tube 1. (This composite tube is a single-layer anti-deformation tube) dipped in ZS-322 high-temperature resistant thermal insulation coating.

[0038] Plug welding point 6: Two plug welding points 6 are symmetrically distributed in the middle of each anti-deformation tube 4, with a welding point diameter of 8mm; welding current is 100A, and the welding time is 2s.

[0039] Preparation method:

[0040] 1. After the 310S stainless steel tube is cleaned with NaOH, the inner layer (Al2O3 ceramic) is obtained by self-propagating gravity separation process.

[0041] 2. When preparing the inner layer (Al2O3 ceramic) 2, appropriately adjust the ratio of thermite to control the reaction temperature at around 2200℃ to obtain the Gr2O3 oxidation protection layer 3

[0042] The anti-deformation tube 4 is cut into 200mm sections. Surface oil is removed using a 5% NaOH solution at 60°C for 30 minutes, followed by natural drying. The entire tube is then dip-coated with ZS-322 high-temperature-resistant thermal insulation coating, operating at a temperature between 10-70°C, and allowed to dry naturally. Φ8 holes are then punched in the middle of each section of the anti-deformation tube to fit together. During this process, a 0.3mm diameter fusible ring is placed against the outer surface of the intermediate tube layer to ensure a 0.3mm gap in the thermal insulation air gap. 1mm graphite gaskets are used to control the gap between each section, and the tube is secured with a clamp.

[0043] 3. Composite pipe obtained after CNC plug welding

[0044] Use CNC plug welding equipment NBC-500 to plug weld the holes of the anti-deformation tube. The welding parameters are: current 100A, welding time 2S, shielding gas is Ar (flow rate is 15L / min). Remove spatter after welding and check whether there are pores and cracks in the weld.

[0045] Performance test: conveying pulverized coal (Vickers hardness 1500HV) at 1350°C wind temperature, inner wall wear after 1000 hours: 0.08mm; oxidation weight loss rate: 0.3g / m 2 .·h; The straightness deviation of pulverized coal conveyed at 1350℃ wind temperature is 0.1mm / m, with no obvious change.

[0046] The above examples are only preferred embodiments of the present invention and are not limitations of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A small-diameter composite pipe that is wear-resistant, high-temperature resistant, and anti-deformation, characterized in that: It includes an inner layer (Al2O3 ceramic), an intermediate layer tube, a protective layer, a heat-insulating air gap layer and an anti-deformation tube arranged in sequence from the inside to the outside; The inner layer is an Al2O3 ceramic layer, which is prepared by a self-propagating gravity separation process and is bonded to the inner surface of the intermediate layer tube with a bonding strength of ≥100MPa; The intermediate layer tube is a 310S or 314 stainless steel tube; The protective layer is an oxide layer formed in situ on the outer surface of the intermediate tube at high temperature, wherein the outer layer of the 310S stainless steel tube forms a 1-5 μm Gr2O3 layer, and the outer layer of the 314 stainless steel tube forms a 3-8 μm SiO2 layer. The heat-insulating air gap layer is the gap between the outer surface of the intermediate layer tube and the inner surface of the anti-deformation tube, and the gap size is 0.1-1mm; The anti-deformation tube has a segmented structure, each segment is 100-500mm long, and a 0.2-10mm expansion gap is reserved between segments. The anti-deformation tube base is a 310S or 314 stainless steel tube, and the entire tube is dipped in high-temperature resistant heat-insulating coating. The anti-deformation tube is fixed to the middle layer tube by symmetrical plug welding or multi-point uniformly distributed plug welding.

2. The composite pipe according to claim 1, characterized in that The anti-deformation tube is two or more layers, with a 0.1-1mm heat-insulating air gap layer left between two adjacent layers of anti-deformation tubes, and the expansion and contraction gaps of each layer of anti-deformation tubes are staggered and not located on the same axis.

3. The composite pipe according to claim 1, characterized in that The high temperature resistant heat insulating coating is ZS-322 coating.

4. The composite pipe according to claim 1, characterized in that The diameter of the composite pipe is DN10-DN40.

5. A method for preparing a wear-resistant, high-temperature oxidation-resistant and deformation-resistant small-diameter composite pipe according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Preparation of inner and middle layer tubes Material selection: 310S or 314 stainless steel pipe is selected as the middle layer pipe, and the surface oil is removed by ultrasonic cleaning. The cleaning agent is 5% NaOH solution, the cleaning temperature is 60℃, and the cleaning time is 30 minutes. Inner layer preparation: The Al2O3 ceramic inner layer is prepared on the inner surface of the intermediate layer tube by using a self-propagating gravity separation process, so that the ceramic layer is combined with the inner surface of the intermediate layer tube. Step 2: Processing and assembly of anti-deformation tube Pretreatment of anti-deformation pipes: Cut 310S or 314 stainless steel pipes into 100-500mm segments. Degrease the surface with ultrasonic cleaning using a 5% NaOH solution at 60°C for 30 minutes, followed by drying. Dip-coat the entire pipe with a high-temperature resistant thermal insulation coating and allow to dry. Fitting and fixing: Fit the pretreated anti-deformation tube in sections onto the outside of the intermediate tube, forming a 0.1-1mm heat-insulating air gap layer between the outer surface of the intermediate tube and the inner surface of the anti-deformation tube, and retaining a 0.2-10mm expansion gap in sections. Fix the anti-deformation tube and the intermediate tube by symmetrical plug welding or multi-point evenly distributed plug welding.

6. The preparation method according to claim 5, characterized in that When the anti-deformation tube consists of two or more layers, after each layer is segmented and fitted together, a heat-insulating air gap of 0.1-1 mm is retained between adjacent layers, and the expansion and contraction gaps of each layer are staggered and distributed, and each layer of anti-deformation tube is fixed by plug welding.

7. The preparation method according to claim 5, characterized in that The high temperature resistant heat insulating coating described in step 2 is ZS-322 coating.

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