Bimetal double-layer ceramic lining mitre elbow and manufacturing method thereof

Abstract

The invention relates to the technical field of wear-resistant pipelines, and discloses a bimetal double-layer ceramic lining mitre elbow and a manufacturing method thereof. The manufacturing method comprises the following specific steps: 1, rolling a steel plate mesh with rhombic holes, honeycomb hexagonal holes and the like into a barrel shape, and spot-welding the steel plate mesh on the inner surface of a straight steel pipe; 2, coating an alloy coating and a first ceramic coating through a centrifugal self-propagating process; 3, a mitre elbow structure is formed through cutting and welding; 4, coating a second layer of ceramic by adopting a static self-propagating process; and 5, processing a joint welded with the straight pipe to form a transition slope. In the process, ceramic coating gaps in the pipe generated by tailor welding are filled with static self-propagating reaction products. The total thickness of the ceramic layer of the elbow is 2-3.0 times that of a straight pipe, and the inner surface roughness Ra is smaller than or equal to 1.6 microns. The problem that the service life of an elbow is not matched with that of a straight pipe is effectively solved, the abrasion resistance is improved by 3.2-3.8 times, the impact strength is improved to 42 J / cm < 2 >, the equal-life design of a pipeline system can be achieved, and the cost of the whole cycle is reduced by 52% or above.

Description

Technical Field

[0001] This invention belongs to the field of wear-resistant pipe technology, and relates to a bimetallic double-layer ceramic-lined elbow and its manufacturing method. Background Technology

[0002] In wear-resistant pipeline systems, elbows are core functional components, and their performance directly determines the operational stability and service life of the entire pipeline system. Existing wear-resistant pipeline elbows suffer from several technical deficiencies that urgently need to be addressed:

[0003] Significant differences in wear rates: Although the wear-resistant layer thickness is the same for ceramic-lined elbows and ceramic-lined straight pipes, in a piping system composed of both, the wear rate of elbows is 3-5 times higher than that of straight pipes due to the local turbulent scouring and impact caused by fluid deflection. This leads to premature wear and thinning, local perforation, and other failures in elbows during system operation, significantly shortening their service life and significantly increasing maintenance costs and system downtime risks.

[0004] Bottlenecks in traditional manufacturing processes: Traditional ceramic-lined shrimp elbows adopt the process route of "centrifugal self-propagating (SHS) method for straight billet production - segmented welding - adhesive filling". Its key defects are: the epoxy resin-based wear-resistant adhesive used at the weld has a temperature resistance of <180℃, which cannot adapt to high-temperature conditions; and its wear resistance is only 15% of that of ceramics, which is very easy to fail under the scouring of high-speed fluids containing particles, becoming an inherent weak link in the elbow structure and seriously restricting the overall performance.

[0005] System-level failure chain reaction: Premature failure of elbows can force the entire pipeline system to shut down for replacement, causing not only production interruptions and soaring maintenance costs, but also reducing the overall lifespan of the pipeline transportation system by more than 40%. In typical scenarios such as pulverized coal transportation in thermal power plants, tailings slurry transportation in mines, and high-temperature flue gas pipelines, frequent replacement of elbows has become a key factor restricting production efficiency and economic benefits.

[0006] In contrast to the technical defects, such as the single-layer centrifugal ceramic-lined steel pipe disclosed in patent number 202311728631.0, the ceramic layer lacks structural reinforcement design and has insufficient impact toughness. It is prone to peeling under impact load, resulting in a sharp drop in wear resistance and failing to meet the stringent requirements of wear resistance and structural reliability of elbows under complex working conditions. Summary of the Invention

[0007] I. Technical Issues

[0008] This invention aims to solve the systemic failure problem caused by the mismatch between the lifespan of elbows and straight pipes in wear-resistant pipeline systems. At the same time, it improves the wear resistance, temperature resistance, and overall structural reliability of elbows, enabling the entire pipeline system to operate with equal lifespan, thereby reducing operation and maintenance costs and improving production efficiency.

[0009] II. Technical Solution

[0010] To solve the above-mentioned technical problems, the present invention provides a bimetallic double-layer ceramic-lined elbow and its manufacturing method, the specific technical solution of which is as follows:

[0011] (I) Design of Structure and Manufacturing Process for Bimetallic Double-Layer Ceramic Lined Shrimp-Shaped Elbow

[0012] In a piping system consisting of ceramic-lined straight pipes and ceramic-lined elbows, a differentiated lining design is adopted: the inner wall of the straight pipe is a bimetallic single-layer ceramic structure, and the inner wall of the elbow is a bimetallic double-layer ceramic structure. The total thickness of the ceramic coating at the elbow is designed to be 2-3 times the thickness of the ceramic lining of the straight pipe.

[0013] The bimetallic double-ceramic lined elbow is formed using a segmented welding process: first, the bimetallic single-layer ceramic lined straight pipe prepared by centrifugal self-propagating method is cut into multiple sections and welded to form the elbow substrate; then, a reinforcing ceramic coating is applied a second time to its inner wall using a static self-propagating method. The result is as follows: Figure 2 The illustrated bimetallic double-ceramic lined elbow features a reinforced ceramic layer whose thickness is precisely designed based on the wear gradient characteristics of different areas of the elbow. This ensures that the total thickness of the bimetallic double-layer ceramic coating meets the protection requirements of high-wear areas, thereby compensating for the localized high wear rate defects caused by fluid diversion.

[0014] At the joint on the inner surface of the elbow formed by welding multiple sections of pipe, there is a gap between the original ceramic linings of adjacent pipe sections. The reinforced ceramic layer, which is applied a second time using a static self-propagating method, can integrally fill and fully cover this gap. This structural design completely eliminates the traditional adhesive filling method, fundamentally eliminating the technical shortcomings of insufficient temperature resistance and poor wear resistance, and preventing the weld area from becoming a failure sensitive point of the elbow.

[0015] Through the above innovative design, a continuous and complete bimetallic double-layer ceramic protective structure is formed on the inner wall of the elbow. Its thickness is significantly greater than that of the single-layer ceramic lining of the straight pipe. This not only greatly improves the wear resistance, but also solves the gap defects through the integrated filling of the ceramic layer, providing core technical guarantee for the long-term operation of the pipeline system throughout its entire life cycle.

[0016] (II) Manufacturing Method of Double-Layer Ceramic Lined Shrimp-Shaped Elbow

[0017] A method for manufacturing a bimetallic double-layer ceramic liner shrimp-shaped bend, characterized by comprising the following steps:

[0018] Step (a): Prefabrication of steel plate mesh frame: Select as follows Figure 1The steel mesh shown has a diamond-shaped or honeycomb hexagonal pattern, with a thickness controlled at 4-6 mm, a short pitch of 5-10 mm, a long pitch of 15-18 mm, and a wire width of 3-6 mm. It is rolled into a cylindrical shape with an outer diameter slightly smaller than the inner diameter of the steel base pipe. This dimensional design aims to ensure a tight fit between the steel mesh cylinder and the elbow steel base pipe, laying the foundation for subsequent fabrication of the reinforcing structure.

[0019] Step (b): Frame Installation and Fixing: Accurately insert the rolled steel mesh cylinder into the elbow base pipe and fix it by spot welding at equal intervals along the axial direction, with a weld spacing ≤ 50mm. This method ensures the stability of the steel mesh frame within the base pipe, enabling it to effectively perform its reinforcing function and improve the overall structural strength and impact resistance of the elbow.

[0020] Step (c): Centrifugal self-propagating process simultaneously coats the inner wall of the pipe with an alloy layer and a first ceramic coating: A mixture of 2Al + Fe2O3 in a molar ratio of 2:1, along with alloying element powders such as Cr3C2-NiCr, is added to the base pipe of the elbow with a steel mesh skeleton. The mixture is then centrifuged at 800-1200 r / min, while simultaneously igniting the mixture to initiate a self-propagating reaction. This process sequentially generates an Fe-Cr3C2-NiCr alloy layer and an Al2O3 ceramic layer on the inner wall of the steel pipe, from the substrate outwards. The centrifugal force generated during the self-propagating process throws the molten alloy and molten ceramic produced by the self-propagating reaction into the steel mesh skeleton, where they are uniformly and tightly welded or adhered to the base pipe and the steel mesh, significantly improving the stability of the coating and the wear resistance of the elbow.

[0021] Step (d): Shrimp bending: Cut the bimetallic ceramic liner base tube obtained after the first layer of ceramic coating into sections and weld them into shrimp bends.

[0022] Step (e): Static self-propagating coating of the second ceramic layer: After the shrimp-shaped elbow is formed, it is placed vertically to the ground. A 2:1 molar ratio of 2Al + Fe₂O₃ aluminothermic agent is introduced into the bimetallic ceramic-lined shrimp-shaped elbow. The aluminothermic agent is ignited to initiate a static self-propagating reaction. The reaction products are molten Al₂O₃ and Fe, which gradually settle downwards in the pipe under gravity. Due to their different densities, Fe falls to the bottom of the pipe during settling, while the viscous Al₂O₃ floats on top and gradually descends. During the settling process, Al₂O₃ is evenly coated on the pipe wall, forming a second Al₂O₃ ceramic layer. This ceramic coating further improves the elbow's wear resistance, especially in terms of erosion and abrasion resistance. Simultaneously, it works synergistically with the first ceramic layer to enhance the stability and reliability of the entire ceramic composite structure.

[0023] Step (f): Interface processing: The ceramic layer at the elbow end is ground to form a transition slope of 15°-45°, and the slope length L is ≥ 3 times the ceramic layer thickness. This transition slope design helps improve the fluid flow at the connection between the elbow and the straight pipe, reduces local stress concentration, and improves the overall operational stability and service life of the pipeline system.

[0024] Ceramic coating gap treatment process inside the pipe: In step (d), the high-temperature melt (>2200℃) generated by static self-propagation automatically fills the gaps, thereby eliminating the gaps between the ceramic layers inside the pipe and forming a continuous ceramic coating inside the pipe. This gap-sealing process effectively improves the strength, wear resistance, and sealing performance of the gaps, eliminates potential defects caused by discontinuities in the ceramic coating at the pipe joints during welding, and enhances the overall quality and performance of the pipe elbow.

[0025] Product structural features: The total thickness δ of the elbow ceramic layer is designed to be the thickness of the straight pipe ceramic layer × (2-3.0). By increasing the thickness of the elbow ceramic layer, the wear resistance of the elbow is effectively improved to adapt to its higher wear rate. Simultaneously, the inner surface roughness Ra of the elbow is required to be ≤1.6μm. The smooth inner surface reduces fluid resistance and particle adhesion, further reducing wear and improving the conveying efficiency of the pipeline system. This solves the systemic failure problem caused by the mismatch between the lifespan of elbows and straight pipes in wear-resistant pipeline systems, achieving the goal of equal service life for the pipeline system.

[0026] The core innovation of this patent:

[0027] Structural innovation: Steel mesh reinforcement enhances resistance to mechanical impact and solves the problem of ceramic brittleness;

[0028] Technological innovation: Achieving continuous dense gradient ceramic layers through a combination of centrifugal and static processes;

[0029] Lifespan Design: By locally thickening the elbows, the lifespan of the ceramic-lined elbows is made comparable to that of the ceramic-lined straight pipes, achieving the same lifespan for the entire conveying system.

[0030] Cost control: Although the cost per unit has increased, the overall system maintenance cost has decreased by more than 50%. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. Those skilled in the art, guided by the teachings of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances.

[0033] Figure 1 Schematic diagram of the unfolded steel mesh frame:

[0034] In the diagram: TL - short pitch, TB - long pitch, d - plate thickness, - wire width, B - mesh width, L - mesh length.

[0035] Figure 2 Schematic diagram of the double-layer ceramic cross-section structure:

[0036] In the figure: 1-base tube, 2-iron generated by centrifugal self-propagating coating, 3-first layer of ceramic coating by centrifugal self-propagating coating, 4-steel mesh wire, 5-second layer of ceramic coating by static self-propagating coating. Detailed Implementation

[0037] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this application. In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the number itself, and "above," "below," "within," etc. are understood to include the number itself. If "first" or "second" is described, it is only for the purpose of distinguishing technical features, and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of indicated technical features. In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0038] Example 1: Coal pulverizer conveyor elbow (DN300) for thermal power plant

[0039] Base pipe material: Q345B seamless steel pipe is selected, and the wall thickness is set at 20mm. This material and wall thickness design can meet the basic requirements of strength and toughness for coal powder conveying pipelines in thermal power plants.

[0040] Expanded metal mesh: Made of 304 stainless steel, 5mm thick, with 12×25mm diamond-shaped holes. 304 stainless steel has good corrosion resistance and processing performance, and can stably perform its reinforcing function under complex working conditions.

[0041] First layer ceramic: An Al2O3-Fe-TiC-Ni layer is prepared by centrifugal self-propagating process with a thickness controlled at 3.0 mm. This first layer ceramic can effectively resist the erosion and wear of coal powder particles.

[0042] Two-layer ceramic: An Al2O3 layer with a thickness of 3.5mm is formed using static self-propagating technology, which further improves the wear resistance and erosion resistance of the elbow.

[0043] Weld treatment: Static self-propagating melt is used to fill the weld, achieving a filling rate of 92%. For any remaining unfilled pores, Fe2O3 / Al slurry is poured in for secondary reinforcement to ensure weld quality.

[0044] Transition slope: A 35° slope is machined as a transition slope with a length L = 15mm, which effectively improves the fluid flow at the connection between the elbow and the straight pipe.

[0045] Results: After actual operation testing, the elbow has a lifespan of 32 months, which is double that of the straight pipe's 16 months. This significantly extends the service life of the elbow in the coal powder conveying pipeline of thermal power plants and reduces maintenance costs and downtime risks.

[0046] Example 2: Mine tailings slurry elbow (DN500, containing quartz sand with a hardness of HV1200)

[0047] Base pipe: Duplex stainless steel 2205 is used as the base pipe material with a wall thickness of 25mm. Duplex stainless steel has excellent corrosion resistance and high strength, and can adapt to the harsh working conditions of mine tailings slurry.

[0048] Reinforcing mesh: Hastelloy C276 mesh with a thickness of 6mm was selected as the reinforcing mesh, and the aperture pattern was optimized into a honeycomb hexagonal shape. Hastelloy C276 has excellent corrosion resistance and high-temperature strength, and the honeycomb hexagonal aperture design further improves the structural stability and reinforcement effect of the reinforcing mesh.

[0049] Ceramic formulation: The first layer uses Al2O3-Fe-Cr3C2-NiCr ceramic, which has excellent resistance to abrasive wear and can effectively resist the wear of hard particles such as quartz sand in tailings slurry; the second layer uses Al2O3Si multiphase ceramic, which has significant advantages in erosion resistance and works synergistically with the first layer ceramic to greatly improve the wear resistance of the elbow.

[0050] Process innovation: Before step (c), the steel mesh is sandblasted to meet the Sa3.0 standard. Sandblasting effectively increases the surface roughness of the steel mesh and improves the bonding strength between the ceramic and the steel mesh. Tests show that the bonding strength has increased by 30%.

[0051] Wear resistance test: Wear test was conducted according to ASTM G65 standard. The wear amount of this elbow was only 0.08g, which is 28% lower than that of a single-layer alumina ceramic lined elbow. This fully demonstrates the excellent wear resistance of the present invention under high hardness particle wear conditions.

[0052] Example 3: High-temperature flue gas duct elbow (650℃ operating condition)

[0053] Temperature resistance design:

[0054] Steel mesh material: Inconel 625 is selected as the steel mesh material. Inconel 625 has excellent high-temperature strength, oxidation resistance and corrosion resistance, and can work stably in high-temperature flue gas environment of 650℃.

[0055] Ceramic layer: The first layer uses Al2O3-Fe-ZrO2-Y2O3 ceramic, which is prepared by centrifugal SHS process, which can improve the density and performance of the ceramic layer; the second layer uses Al2O3-Fe-ZrO2 multiphase ceramic prepared by static SHS process, which further improves the wear resistance and thermal stability of the elbow under high temperature environment.

[0056] Cooling process: After step (e), slow cooling is performed at a rate of ≤10℃ / min. Through slow cooling, thermal stress cracks caused by temperature changes between the ceramic layer and the base pipe are effectively eliminated, thereby improving the structural reliability and service life of the elbow.

[0057] Thermal shock test: After 20 thermal shock tests at 1100℃ followed by water quenching, the ceramic layer of the elbow showed no peeling, indicating that the elbow has good stability and reliability under high-temperature thermal shock conditions and can meet the actual use requirements of high-temperature flue gas pipelines.

[0058] Example 4: Manufacturing Optimization of Extra-Large Diameter Elbow (DN1200)

[0059] Improved Centrifugal Coating Process: For ultra-large diameter elbows, a three-stage centrifugal coating process is adopted. Each 120° arc zone is centrifuged separately, and speed gradient control is used to ensure a central speed of 1000 r / min and an end speed of 1200 r / min. This process improvement effectively solves the problem of controlling the uniformity of the ceramic layer during centrifugal coating of ultra-large diameter elbows, ensuring the quality and performance of the ceramic layer.

[0060] Static self-propagation: A multi-point synchronous ignition device is used for static self-propagation coating. This device can ensure that the coating is formed uniformly over a large area, improving the quality and efficiency of the second layer of ceramic coating on ultra-large diameter elbows.

[0061] Economic comparison: According to calculations, the cost of a single ultra-large diameter elbow increases by 35% compared to the traditional manufacturing process. However, due to its significantly extended service life, the total life cycle cost of the pipeline system decreases by 52%. From a long-term operation perspective, it has significant economic benefits and application value.

[0062] Technical effect

[0063] index Traditional elbow This invention Test Standards abrasion resistance Baseline value 1.0 3.2-3.8 times ASTM G105 Impact resistance <![CDATA[15J / cm 2 ]]> <![CDATA[42J / cm 2 ]]> GB / T 229 High temperature durability (600℃) Failed after 3000 hours >15000h ISO11114-4 Inner wall roughness Ra 6.3μm Ra 0.8-1.6μm ISO 4287 Full life cycle cost Baseline value 100% 48％ ISO 15663

[0064] This invention achieves significant improvements and optimizations over traditional elbows in key indicators such as wear resistance, impact strength, high-temperature durability, inner wall roughness, and total life cycle cost through unique structural innovations (such as the application of steel plate mesh skeleton), process innovations (combination of centrifugal and static self-propagating dual processes), and targeted life design and cost control strategies. It has extremely high engineering application value and market competitiveness.

[0065] In the description of this specification, the references to "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A bi-metallic double-pie ceramic lined elbow and a method of manufacturing the same, characterized in that, The method comprises the following steps: The steel pipe is prefabricated with steel mesh skeleton, centrifugal self-propagating high-temperature synthesis is used to melt and coat alloy coating and first layer ceramic on the inner surface of the steel pipe, shrimp-bend forming is performed, and static self-propagating high-temperature synthesis is used to melt and coat second layer ceramic.

2. The method according to claim 1, wherein the steel mesh has a diamond shape, a regular hexagon shape, a rectangle shape, a circle shape or the like, and the diamond-shaped steel mesh has a mesh thickness of 4-6 mm, a short pitch of 5-10 mm, a long pitch of 15-18 mm, and a filament width of 3-6 mm.

3. The method according to claim 1, wherein the centrifugal self-propagating high-temperature synthesis is used to prepare the alloy coating and the first layer Al2O3 ceramic coating in the steel pipe, and the second layer ceramic is Al2O3 ceramic prepared by static self-propagating high-temperature synthesis.

4. The method according to claim 1, wherein static self-propagating high-temperature synthesis melt is used to automatically fill the ceramic seam generated by pipe inner tailor-welding.

5. A wear-resistant curved head for shrimp, manufactured by any one of claims 1-4, characterized in that: The total thickness of the ceramic layer of the elbow is 2-3 times that of the ceramic layer of the straight pipe section, and the connecting transition slope angle between the inner surface of the double-layer ceramic lined elbow and the inner surface of the single-layer ceramic lined straight pipe is 15°-45°.

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