A composite pipe for a thermal power plant cleaning system and a method of manufacturing the same

Abstract

The application provides a composite pipe for a thermal power generation cleaning system and a preparation method thereof. The application takes 316L stainless steel as a base pipe material, adopts a flux-cored arc welding technology, and electric arc cladding Fe-Cr-Mn alloy welding wire into the stainless steel base pipe through an intelligent cladding forming equipment controlled by a PLC, so that Fe-Cr-Mn alloy / stainless steel bimetallic composite pipes of different specifications can be prepared by adjusting and controlling a cladding process. The bimetallic composite pipe prepared by the application has few defects, high interface bonding strength, small crystal grains and dense structure, and thus has high hardness and impact toughness, the hardness is up to 820HV, the room temperature impact energy is up to 160J, the tensile strength is up to 860MPa, the yield strength is up to 620MPa, and the elongation after fracture is up to 20%. The composite pipe for the thermal power generation cleaning system has good comprehensive mechanical properties, and thus the service life of the composite pipe is greatly improved.

Description

Technical Field

[0001] This invention relates to composite pipe manufacturing technology, and more particularly to a composite pipe for a clean system in thermal power generation and its manufacturing method. Background Technology

[0002] In the piping systems of clean power generation equipment, desulfurization pipelines and ash / flue gas conveying pipelines suffer from severe corrosion and wear due to long-term use in harsh environments such as high temperatures, acidic solutions, flue gas, and fly ash. Damage or leakage in these pipelines directly reduces pollutant treatment efficiency and can even lead to forced unit shutdowns and damage to the clean power generation system. Therefore, mass-producing pipelines with stable performance that meet the long-term requirements of clean power generation systems is the main direction for future development.

[0003] Research results show that corrosion-resistant stainless steels such as 316L have good resistance to chloride ion corrosion and can be used to manufacture desulfurization system pipelines. However, 316L stainless steel has low hardness and wear resistance. Under the combined effects of scouring and corrosion from desulfurization slurry, the pipeline damage rate will increase significantly, seriously affecting the service life of 316L stainless steel. Therefore, researchers used 316L stainless steel as the base pipe and lined it with metal materials, rubber, glass flake resin, etc., to form a pipeline composite material, which can effectively improve the service life of the pipeline. Among these composite materials, rubber as the lining is easily eroded and corroded through the pipeline when subjected to high-velocity scouring of solid particles entrained in the medium; while glass flake resin as the lining requires maintenance to prevent the lining coating from peeling off; in comparison, corrosion-resistant alloy linings are more suitable for long-term use. In comparison, lining the base pipe with metal materials to form a bimetallic composite pipeline can combine the advantages of the base steel pipe and the lining, maximizing the complementary advantages of the materials and reducing engineering costs and maintenance costs.

[0004] Currently, common manufacturing methods for bimetallic composite pipes include centrifugal casting, hot extrusion, and induction brazing. Centrifugal casting utilizes centrifugal force to cast molten metals of different compositions in layers, controlling the fusion layer between the inner and outer metals within a certain thickness range to form a complete metallurgical composite pipe. Bimetallic composite pipes prepared by this process have advantages such as dense structure, fine grains, wide transition layers, low stress, and low inclusion content. However, this process also has certain drawbacks, such as a tendency for segregation in the castings, a relatively rough surface, and difficulty in controlling the internal surface dimensions.

[0005] Hot-extruded composite pipes are produced by cleaning the surfaces of dissimilar metals, assembling them into extruded blanks, heating them to a specific temperature, and extruding them according to a certain extrusion ratio. Under pressure, the metals come into close contact and achieve metallurgical composite bonding. This process is simple and produces strong bonding. However, it is prone to wall thickness fluctuations, and due to the inconsistent deformation resistance of the bimetallic materials during hot deformation, defects such as cracks are easily generated.

[0006] Induction brazing involves placing a filler metal between an alloy tube and a base tube, and then continuously induction heating under inert gas protection. The filler metal melts and reacts between the base tube and the alloy tube, rapidly solidifying under the action of cooling water to form a metallurgical bond. However, this process is relatively complex, consumes a lot of materials, and is energy-intensive. Summary of the Invention

[0007] The purpose of this invention is to address the problems of high forming costs, pipe deformation during the welding process, and weld cracking, poor quality, coarse grain structure, and poor overall mechanical properties of composite pipes caused by various aspects of existing composite pipe welding forming technologies. This invention proposes a method for preparing composite pipes for clean systems in thermal power generation. This method uses an electric arc as a heat source to melt welding wire material and metallurgically bond it with a stainless steel base pipe to prepare a bimetallic composite pipe. By optimizing and matching process parameters such as welding wire feed speed, welding current, and welding voltage, this method produces bimetallic composite pipes with fewer defects, high interfacial bonding strength, fine and dense grains, high hardness, and excellent overall mechanical properties. During the welding process, this invention uses a water-cooling device to rapidly cool the welding zone, reducing heat input, improving welding efficiency, reducing welding deformation, and providing significant advantages for precise control of the bimetallic pipe.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing a composite pipe for a clean power generation system, comprising the following steps:

[0009] (1) Arc welding: using stainless steel pipe as the base pipe, the base pipe is placed on the workbench and arc welding is performed using gas metal arc welding technology. During the welding process, the welding torch is inserted into the stainless steel pipe and the solid welding wire is loaded into the wire feeding mechanism. The wire is fed to the welding position through the wire feeding hose. The welding process is controlled by the welding forming equipment to weld Fe-Cr-Mn alloy welding wire onto the inner wall of the base pipe. During the welding process, the water-cooled spray device located on the outer surface of the base pipe is moved synchronously to spray water to cool the welding position.

[0010] (2) Cleaning: After the base tube with Fe-Cr-Mn alloy deposited in step (1) has cooled down, clean the surface of the deposited layer with a nitrogen spray gun.

[0011] Repeat steps (1) and (2) to repeatedly stack the fusion plating until the total thickness of the Fe-Cr-Mn alloy reaches the set thickness, thus preparing a composite pipe for a clean system of thermal power generation (i.e., Fe-Cr-Mn alloy / 316L stainless steel bimetallic composite pipe).

[0012] Furthermore, the stainless steel pipe is a 316L stainless steel pipe.

[0013] Furthermore, the base tube is pretreated before arc welding to remove surface oil and oxide film, giving the surface a metallic luster.

[0014] Furthermore, the inner diameter of the stainless steel tube is 100-800mm.

[0015] Furthermore, the mass percentages of each component in the Fe-Cr-Mn alloy welding wire are as follows: C: 0.2-6.5 wt.%, Cr: 10-34 wt.%, Mn: 0.5-2.8 wt.%, Si: 0.5-3.0 wt.%, Ni: 0.05-5 wt.%, Fe: balance, and unavoidable impurities.

[0016] Furthermore, the preparation method of the Fe-Cr-Mn alloy welding wire includes the following steps: mixing the components according to the mass percentage to obtain a metal powder core, then filling it into a molded metal groove, sealing it, and then drawing it multiple times on a wire drawing machine to obtain a welding wire of the required diameter.

[0017] Furthermore, the diameter of the Fe-Cr-Mn alloy welding wire is 1.2mm-3.0mm, preferably 1.6mm.

[0018] Further, in the gas metal arc welding (GMAW) technique described in step (1), the inert gas is 99.99% argon, and the inert gas flow rate is 10 L / min to 20 L / min, preferably 10 L / min. Unless otherwise specified, all percentages in this invention refer to mass percentages.

[0019] Furthermore, the fusion molding equipment is a PLC-controlled intelligent fusion molding equipment.

[0020] Furthermore, the pipe cladding forming equipment includes a platform base, a servo motion mechanism, a wire feeding mechanism, an electric arc cladding system, a water cooling system, a workpiece rotation control system, a workpiece support system, and a control system;

[0021] The servo motion mechanism, workpiece support system, and workpiece rotation control system are respectively fixed on the platform base;

[0022] The servo motion mechanism is equipped with a wire feeding mechanism at its top. The end of the wire feeding mechanism is fixed to the arc welding system via an aluminum tube fixing block. Under the control of the control system, the servo motion mechanism can drive the wire feeding mechanism to deliver the wire to the area below the welding torch of the arc welding system, and drive the welding torch of the arc welding system to move along the workpiece axis and the inner circumference of the workpiece. The end of the water cooling system away from the workpiece is fixed to the aluminum tube via a support fixing tube. The distance between the nozzle of the water cooling system and the welding torch of the arc welding system is greater than the workpiece wall thickness. That is, when the welding torch penetrates into the workpiece, the water cooling system is located opposite to the outer wall of the workpiece. During the welding process, the welding system and the water cooling system move synchronously along the workpiece axis, and the water cooling device sprays water to cool the welding position synchronously. The top of the workpiece support system is equipped with rollers, which abut against the lower surface of the workpiece to support it. The workpiece rotation control system can drive the workpiece to rotate along the axis.

[0023] The control system is communicatively connected to the servo motion mechanism, the arc welding system, the water cooling system, and the workpiece rotation control system, respectively, and controls the welding torch motion, the welding process, the water cooling process, and the workpiece rotation process.

[0024] Furthermore, the servo motion mechanism can move the welding torch of the arc welding system along the workpiece axially according to the operating speed and trajectory commands input from the control system. The servo motion mechanism includes a worm gear reducer, a motor, a lifting screw, a lifting support plate, and a double-slider linear guide. The motor, worm gear reducer, and workpiece are coaxially connected via a coupling, enabling the welding torch of the arc welding system to move along the workpiece axially. The output shaft of the worm gear reducer is equipped with a lifting screw, and the bottom of the lifting screw is fitted with a lifting support plate via a lifting screw cap. The lifting support plate is bolted to a double-slider linear guide, and the slider moves linearly along the guide to adjust the radial distance between the welding torch and the inner wall of the workpiece, thereby achieving multi-layer welding.

[0025] Furthermore, the wire feeding mechanism includes a wire feeding hose, an aluminum tube fixing block, an aluminum tube, and four wire feeding wheels. The wire feeding wheels are fixed on the welding machine bracket and have wire feeding grooves inside. The outlet end of the wire feeding wheel is connected to the wire feeding hose. The end of the wire feeding hose is fitted with an aluminum tube through the aluminum tube fixing block. The four wire feeding wheels include two driving wheels and two driven wheels. The driving wheels and driven wheels mesh in pairs. The driving wheels are driven by a motor to provide power for wire feeding. The driven wheels are equipped with adjustable preload pressure rods that can be used to adjust the tension of the welding wire. The welding wire is tightly wrapped by the wire feeding grooves to ensure that the welding wire will not deform.

[0026] Furthermore, the arc welding system includes: a welding torch, a welding torch holder, a high-temperature water-cooled camera, and a display. The welding torch holder is located at one end of the welding torch near the wire feeding mechanism, fixing the welding torch to the aluminum tube. The high-temperature water-cooled camera is fixed at one end of the welding torch near the workpiece. The high-temperature water-cooled camera is communicatively connected to the display, which can display the welding status in real time.

[0027] Furthermore, the water cooling system includes a nozzle and a nozzle support and fixing tube. The nozzle support and fixing tube is parallel to the welding torch and is fixed by the support and fixing tube. The nozzle faces the outer wall of the workpiece.

[0028] Furthermore, the workpiece rotation control system includes a workpiece chuck and a rotary motor for driving the workpiece chuck. The workpiece to be processed is fixed on the workpiece chuck, and the control system controls the rotation speed of the motor. The rotary motor can drive the workpiece chuck to rotate, thereby driving the workpiece to rotate along the axis.

[0029] Furthermore, the control system is a PLC control system.

[0030] Furthermore, the PLC control system includes a database and an artificial neural network model calculation module. The PLC control system can control the wire feeding speed, current intensity, voltage intensity, pipe rotation speed, welding torch movement trajectory, water cooling intensity, and argon flow rate. It can display the complete path of the arc deposition process and the current status of each device in the equipment system. At the same time, the PLC control system has an embedded control database. This database takes the welding wire material, workpiece inner diameter, welding wire diameter, current intensity, and welding speed as input quantities. Through the artificial neural network model algorithm, it matches the corresponding workpiece rotation speed, wire feeding speed, and welding voltage.

[0031] Further, the welding process parameters in step (1) are: current intensity 150-400A, voltage intensity 16-32V, and wire feeding rate 2.0-6.0m / min. Preferably, the current intensity is 160A, the voltage intensity is 18V, and the wire feeding rate is 2.5m / min.

[0032] Furthermore, the water flow rate for the water spray cooling is 15L / h-45L / h, preferably 20L / h.

[0033] Furthermore, the thickness of a single Fe-Cr-Mn alloy deposition is 3-5 mm.

[0034] Furthermore, the thickness of the Fe-Cr-Mn alloy plating is set to 3mm-30mm.

[0035] Furthermore, the number of repeated overlapping and welding processes is 1-8 times.

[0036] Another objective of this invention is to disclose a composite pipe for a clean system in thermal power generation, prepared using the method described above. This invention improves the hardness, wear resistance, and corrosion resistance of the composite pipe by fusing Fe-Cr-Mn alloy composite material onto the inner surface of a 316L stainless steel base pipe, thereby extending the service life of the composite pipe.

[0037] Furthermore, the hardness of the composite pipe used in the thermal power generation cleaning system is 300-820 HV.

[0038] Furthermore, the impact energy of the composite pipe used in the clean system for thermal power generation is 45J-160J.

[0039] Furthermore, the composite pipe used in the clean system for thermal power generation has a tensile strength of 650-860 MPa, a yield strength of 380-620 MPa, and an elongation after fracture of 10-20%.

[0040] Methods for testing and characterization:

[0041] The prepared Fe-Cr-Mn alloy / 316L stainless steel bimetallic composite tube was subjected to surface morphology and related tests and characterization. The hardness value of the cladding layer of the Fe-Cr-Mn alloy / 316L stainless steel bimetallic composite tube was measured by Vickers hardness tester. The impact energy of the Fe-Cr-Mn alloy / 316L stainless steel bimetallic composite tube was tested by pendulum impact testing machine (using a 10mm×10mm×55mm specimen with a 2mm deep U-shaped notch). The microstructure of the composite tube cross section was observed by metallographic microscope. The results show that the prepared Fe-Cr-Mn alloy / stainless steel bimetallic composite tube has few defects, high interfacial bonding strength, fine grains and dense structure, thus exhibiting high hardness and impact toughness.

[0042] The composite pipe and its preparation method for a clean system in thermal power generation, as described in this invention, have the following advantages compared to existing technologies:

[0043] 1) This invention uses 316L stainless steel as the base pipe material and adopts gas metal arc welding technology. Through PLC-controlled intelligent deposition forming equipment, Fe-Cr-Mn alloy welding wire is arc-deposited into the inside of the stainless steel base pipe. By adjusting the deposition process (including deposition current intensity, voltage intensity, and welding wire feed rate), Fe-Cr-Mn alloy / stainless steel bimetallic composite pipes of different specifications can be prepared.

[0044] 2) This invention implements a water-cooling process for small-diameter, long-distance welded pipes to ensure rapid cooling during the welded process and prevent pipe deformation caused by continuous high heat input during the welded process.

[0045] 3) The Fe-Cr-Mn alloy / 316L stainless steel bimetallic composite pipe prepared by this invention has few defects, high interfacial bonding strength, fine grains and dense structure, thus having high hardness and impact toughness. The maximum hardness of the cladding layer is 820HV; the maximum room temperature impact energy of the bimetallic composite pipe is 160J.

[0046] 4) The composite pipe of the present invention used in the clean system of thermal power generation has good comprehensive mechanical properties. The tensile strength of the bimetallic composite pipe is 860MPa, the yield strength is 620MPa, and the elongation after fracture is 20%, thus its service life is greatly improved.

[0047] 5) Arc welding forming technology features low cost, high efficiency, and a metallurgical bond between the welded layer and the substrate. By cooling the outer wall of the base pipe with water during the welding process, rapid cooling is achieved, making it easier to obtain a fine-grained structure or generate new phases that are impossible to obtain in equilibrium. This effectively improves the strength, wear resistance, and corrosion resistance of the welded layer. Therefore, using arc welding forming technology to prepare small-diameter, long-distance composite steel pipes is a major future development direction. Attached Figure Description

[0048] Figure 1 This is a surface view of the composite pipe used in the cleaning system for thermal power generation in Example 1;

[0049] Figure 2 This is a microstructure image of a single-pass sublayer weld deposition process in Example 1;

[0050] Figure 3 The images show the microstructure of each of the four passes of the weld bonding process in Example 1; the left image shows the two-layer weld bonding zone, the middle image shows the two-layer to three-layer weld bonding transition zone, and the right image shows the three-layer weld bonding zone; a. Substrate to one-layer weld bonding transition zone b. One-layer weld bonding zone c. One-layer to two-layer weld bonding transition zone d. Two-layer weld bonding zone e. Two-layer to three-layer weld bonding transition zone f. Three-layer weld bonding zone g. Three-layer to four-layer weld bonding transition zone h. Four-layer weld bonding zone;

[0051] Figure 4 Microhardness diagram of the four weld layers in Example 1;

[0052] Figure 5 Image of the surface after fusion deposition in Example 2;

[0053] Figure 6 A schematic diagram of the intelligent cladding and forming equipment for bimetallic composite pipes of the present invention;

[0054] Figure 7 A schematic diagram of the PLC control neural algorithm for the intelligent cladding and forming equipment for bimetallic composite pipes of the present invention;

[0055] Figure 8 Schematic diagram of the servo motion system of this invention;

[0056] Figure 9 Schematic diagram of the four-wheel wire feeding mechanism of the present invention;

[0057] Figure 10 A schematic diagram of the arc welding system of the present invention. Detailed Implementation

[0058] The present invention will be further described below with reference to the embodiments:

[0059] Example 1

[0060] This embodiment discloses a method for preparing a composite pipe for a clean system in thermal power generation, including the following steps:

[0061] (1) The interior of the 316 stainless steel base tube is pretreated before fusion deposition, oil stains are cleaned and oxide layer is polished so that the surface has a metallic luster. In this embodiment, the 316L base tube is selected with an inner diameter of 200mm. The pretreated base tube is placed on the workbench.

[0062] (2) The solid welding wire is loaded into the wire feeding mechanism, which feeds the welding wire to the deposition position through the wire feeding hose; wherein the diameter of the welding wire is 1.6 mm, and the Fe-Cr-Mn alloy welding wire comprises the following components by weight percentage: C: 4.5 wt.%, Cr: 30.12 wt.%, Mn: 1.05 wt.%, Ni: 1.30 wt.%, Si: 0.8 wt.%, Fe: balance, and unavoidable impurities.

[0063] The preparation method of the Fe-Cr-Mn alloy welding wire includes the following steps: mixing the components according to the mass percentage to obtain a metal powder core, then filling it into a molded metal groove, sealing it, and then drawing it multiple times on a wire drawing machine to obtain a welding wire of the required diameter.

[0064] (3) Start arc deposition. The deposition equipment is a PLC-controlled intelligent deposition equipment, which includes a welding machine, a robotic arm, and a worktable. During operation, the robotic arm clamps the welding torch for precise positioning and executes the motion trajectory strictly according to the previously input robot assembly language, moving while deposition, thus achieving fully automatic welding deposition. The deposition process parameters input into the equipment are: current intensity 160A, voltage intensity 18V, and wire feed rate 2.5m / min. At the same time, argon gas protection is introduced throughout the laser deposition process. The protective gas used is 99.99% argon gas with a gas flow rate of 10L / min.

[0065] (4) During the laser cladding process, the water cooling device is turned on simultaneously. The water cooling device is evenly distributed along the circumference of the 316L stainless steel pipe. The water cooling spray device is connected to the axial moving guide rail. By controlling the speed of the axial moving guide rail, the axial moving speed of the water cooling spray device is made consistent with the moving speed of the welding gun, so that the water cooling spray device always sprays water to cool the cladding position. The water flow rate is 20L / h.

[0066] (5) When the arc welding gun reaches the end point, the wire feeding mechanism first stops feeding the wire, then turns off the welding power, and then turns on the shielding gas for 10 seconds to prevent the weld layer from being oxidized. This completes the single-pass welding, and the single-pass welding thickness is 3mm.

[0067] (6) After a single pass of deposition is completed, wait 60 seconds to prevent the heat accumulation effect from affecting the additive forming. Move the arc welding gun to the starting point of the deposition pass. Repeat steps 3 to 5 to complete multiple passes of deposition. Repeat the deposition 4 times to achieve a deposition layer thickness of 12mm.

[0068] Macroscopic forming: After the deposition is completed, the surface is first polished with a steel brush to remove slag and other impurities. Then, the deposition layers with different numbers of layers are compared to observe the forming condition and whether there are cracks, pores, or metallic luster on the surface. Figure 1 The sample surface shown has formed a full fish scale pattern and is smooth, without defects such as edge bite, pores, or cracks.

[0069] Microstructure: After the arc welding test, the sample needs to be left to stand for 24 hours before metallographic sample preparation. Then, the microstructure of the welded area is analyzed using a metallographic microscope. Figure 2 The microstructure of the fused layer shown is a fine needle-like crystal structure, such as... Figure 3 The microstructure of each of the four fusion passes is shown; the left side shows the two-layer fusion zone, the middle side shows the two-to-three-layer fusion transition zone, and the right side shows the three-layer fusion zone. As the number of layers increases, the grains show a clear trend of continuous enlargement, and a large number of needle-like and columnar crystals are produced.

[0070] Performance experiments: Microhardness tests were performed on samples with one and four weld layers using a microhardness tester, and hardness variation curves were plotted. For example... Figure 4 As shown, the hardness of the cladding layer is significantly improved compared to the substrate, with a maximum hardness of up to 820 HV.

[0071] The deposition modeling equipment used in this embodiment is as follows: Figure 6-10 As shown, it includes a platform base 1, a servo motion mechanism 2, a wire feeding mechanism 3, an arc welding system 4, a water cooling system 5, a workpiece rotation control system 7, a workpiece support system 8, and a control system 9; the servo motion mechanism 2, the workpiece support system 8, and the workpiece rotation control system 7 are sequentially fixed on the platform base 1.

[0072] like Figure 10 As shown, the arc welding system is horizontally arranged and includes: a welding torch 41, a welding torch clamping block 42, a high-temperature water-cooled camera 43, and a display. The welding torch clamping block 42 is located at one end of the welding torch 41 near the wire feeding mechanism 3, fixing the welding torch 41 to the aluminum tube 34. The high-temperature water-cooled camera 43 is fixed at one end of the welding torch 41 near the workpiece. The high-temperature water-cooled camera is communicatively connected to the display, which can display the workpiece welding status in real time.

[0073] The servo motion mechanism 2 is equipped with a wire feeding mechanism 3 at its top. The end of the wire feeding mechanism is fixed to the arc welding system 4 by an aluminum tube fixing block. Under the control of the control system 9, the servo motion mechanism 2 can drive the wire feeding mechanism 3 to deliver the wire to the area below the welding torch 41 of the arc welding system, and drive the arc welding system to move along the workpiece axis and the inner circumference of the workpiece. Specifically, as shown... Figure 8 As shown, the servo motion mechanism 2 can move according to the running speed and trajectory commands input in the control system 9. The servo motion mechanism 2 includes a worm gear reducer 21, a motor 22, a lifting screw 23, a lifting support plate 24, and a double slider linear guide 25. The motor 22, the worm gear reducer 2, and the workpiece are coaxially connected by a coupling, so that the welding torch 41 of the arc welding system moves axially in the workpiece. The output shaft end of the worm gear reducer 21 is equipped with a lifting screw 23. The bottom of the lifting screw 23 is equipped with a lifting support plate 24 through a lifting screw cap. The lifting support plate 24 is bolted to the double slider linear guide 25. The slider moves linearly on the guide rail to adjust the radial distance between the welding torch 41 and the inner wall of the workpiece, thereby realizing multi-layer welding.

[0074] like Figure 9 As shown, the wire feeding mechanism 3 is fixed on the welding machine bracket. The wire feeding mechanism 3 can transport the wire to the area below the welding torch 41 of the arc welding system. The wire feeding mechanism 3 includes a wire feeding hose 32, an aluminum tube 34, and four wire feeding wheels 31. The wire feeding wheels 31 are fixed on the welding machine bracket and have wire feeding grooves inside. The outlet end of the wire feeding wheel is connected to the wire feeding hose 32. The end of the wire feeding hose 32 is fitted with an aluminum tube 34 through an aluminum tube fixing block 33. The four wire feeding wheels 31 include two driving wheels and two driven wheels. The driving wheels and driven wheels mesh in pairs. The driving wheels are driven by a motor to provide power for wire feeding. The driven wheels are equipped with adjustable preload pressure rods that can be used to adjust the tension of the welding wire. The welding wire is tightly wrapped by the wire feeding groove to ensure that the welding wire will not deform.

[0075] The water cooling system 5 and the arc welding system 4 are fixed at the ends away from the workpiece by a support and fixing pipe 6. The distance between the nozzle of the water cooling system and the welding gun of the arc welding system is greater than the workpiece wall thickness. That is, when the welding gun is inserted into the workpiece, the water cooling system is located at the opposite position on the outer wall of the workpiece. During the welding process, the welding system and the water cooling system move synchronously along the workpiece axis, and the water cooling device sprays water to cool the welding position synchronously. The water cooling system 5 includes a nozzle and a nozzle support and fixing pipe. The nozzle support and fixing pipe is parallel to the welding gun and is fixed by the support and fixing pipe 6. The nozzle faces the outer wall of the workpiece.

[0076] The workpiece support system 8 is provided with rollers at the top, and the rollers abut against the lower surface of the workpiece to support the workpiece.

[0077] The workpiece rotation control system 7 can drive the workpiece to rotate along the axis. The workpiece rotation control system 7 includes a workpiece chuck and a rotary motor for driving the workpiece chuck. The workpiece to be processed is fixed on the workpiece chuck. The control system controls the rotation speed of the motor. The rotary motor can drive the workpiece chuck to rotate, thereby driving the workpiece to rotate along the axis.

[0078] The control system 9 is communicatively connected to the servo motion mechanism 2, the arc welding system 4, the water cooling system 5, and the workpiece rotation control system 7. The control system 9 can control the welding torch motion, the welding process, the water cooling process, and the workpiece rotation process. Figure 7 As shown, the control system 9 is a PLC control system. The PLC control system includes a database and an artificial neural network model calculation module. The PLC control system can control wire feeding speed, current intensity, voltage intensity, pipe rotation speed, welding torch movement trajectory, water cooling intensity, and argon flow rate. It can display the complete path of the arc deposition process and the current status of each device in the system. Simultaneously, the PLC control system embeds a control database, which takes welding wire material, workpiece inner diameter, welding wire diameter, current intensity, and welding speed as input values. Through an artificial neural network model algorithm, it matches the corresponding workpiece rotation speed, wire feeding speed, and welding voltage.

[0079] Comparative Example 1

[0080] This comparative example discloses an arc cladding process for bimetallic composite pipes, comprising the following steps:

[0081] (1) Pre-treatment of the inside of the 316 stainless steel base pipe before fusion deposition, cleaning oil stains and grinding oxide layer to make the surface show a metallic luster. Usually, the 316L base pipe specification is selected with an inner diameter of 200mm. The pre-treated base pipe is placed on the workbench.

[0082] (2) The solid welding wire is loaded into the wire feeding mechanism, which feeds the welding wire to the deposition position through the wire feeding hose; wherein the diameter of the welding wire is 1.6 mm, and the Fe-Cr-Mn alloy welding wire comprises the following components by weight percentage: C: 6.5 wt%, Cr: 31.5 wt%, Mn: 1.15 wt%, Si: 1.20 wt.%, Ni: 0.8 wt.%, Fe: balance and unavoidable impurities.

[0083] The preparation method of the Fe-Cr-Mn alloy welding wire includes the following steps: mixing the components according to the mass percentage to obtain a metal powder core, then filling it into a molded metal groove, sealing it, and then drawing it multiple times on a wire drawing machine to obtain a welding wire of the required diameter.

[0084] (3) Start arc deposition. The deposition equipment is the same as in Example 1. During operation, the robotic arm clamps the welding torch for precise positioning and executes the motion trajectory strictly according to the previously input robot assembly language, moving while deposition, thus achieving fully automatic welding deposition. The deposition process parameters input into the equipment are: current intensity 420A, voltage intensity 35V, wire feed rate 8m / min. At the same time, argon gas protection is introduced throughout the laser deposition process. The protective gas used is 99.99% argon gas with a gas flow rate of 10L / min.

[0085] (4) During the laser cladding process, the water cooling device is turned on simultaneously. The water cooling device is evenly distributed along the circumference of the 316L stainless steel pipe. The water cooling spray device is connected to the axial moving guide rail. By controlling the speed of the axial moving guide rail, the axial moving speed of the water cooling spray device is made consistent with the welding gun cladding speed, so that the water cooling spray device always sprays water to cool the cladding position. The water flow rate is 20L / h.

[0086] (5) When the arc welding gun reaches the end point, the wire feeding mechanism first stops feeding the wire, then turns off the welding power, and then turns on the shielding gas for 10 seconds to prevent the weld layer from being oxidized, thus completing a single pass of welding. The thickness of a single pass of welding is 2mm.

[0087] Macroscopic forming: After the fusion is completed, the surface is first polished with a steel brush to remove impurities such as slag. Then, the fusion layers with different numbers of fusion layers are compared to observe the forming condition and whether there are defects such as cracks and pores on the surface.

[0088] By observing the samples taken from the bimetallic composite pipes after fusion deposition in the comparative examples and Comparative Example 1, it was found that the fusion deposition quality of Comparative Example 1 was poor, with welding defects such as porosity and cracks, and multi-layer fusion was difficult to achieve. Figure 5 As shown in the comparison, the main reasons for the above results are the mismatch of process parameters and different welding wire compositions.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a composite pipe for a clean system in thermal power generation, characterized in that, Includes the following steps: (1) Arc welding: using stainless steel pipe as the base pipe, the base pipe is placed on the workbench and arc welding is performed using gas metal arc welding technology. During the welding process, the welding torch is inserted into the stainless steel pipe and the solid welding wire is loaded into the wire feeding mechanism. The wire is fed to the welding position through the wire feeding hose. The welding process is controlled by the welding forming equipment. Fe-Cr-Mn alloy welding wire is welded on the inner wall of the base pipe. During the welding process, the water-cooled spray device located on the outer surface of the base pipe is moved synchronously to spray water to cool the welding position. (2) Cleaning: After the base tube with Fe-Cr-Mn alloy deposited in step (1) has cooled, clean the surface of the deposited layer with a nitrogen spray gun. Repeat steps (1) and (2) to repeatedly stack the molten metal until the total thickness of the Fe-Cr-Mn alloy reaches the set thickness, and prepare a composite pipe for a clean system for thermal power generation. The mass percentages of each component in the Fe-Cr-Mn alloy welding wire are as follows: C: 0.2-6.5 wt.%, Cr: 10-34 wt.%, Mn: 0.5-2.8 wt.%, Si: 0.5-3.0 wt.%, Ni: 0.05-5 wt.%, Fe: balance and unavoidable impurities; The composite pipe used in the clean system for thermal power generation has a hardness of 300-820 HV, an impact energy of 45J-160J, a tensile strength of 650-860MPa, a yield strength of 380-620MPa, and an elongation after fracture of 10-20%. The fusion forming equipment used includes a platform base (1), a servo motion mechanism (2), a wire feeding mechanism (3), an electric arc fusion system (4), a water cooling system (5), a workpiece rotation control system (7), a workpiece support system (8), and a control system (9). The servo motion mechanism (2), the workpiece support system (8) and the workpiece rotation control system (7) are respectively fixed on the platform base (1); The servo motion mechanism (2) is equipped with a wire feeding mechanism (3) at its top. The end of the wire feeding mechanism is fixed to the arc welding system (4) by an aluminum tube fixing block (33). Under the control of the control system (9), the servo motion mechanism (2) can drive the wire feeding mechanism (3) to deliver the wire to the bottom of the welding torch (41) of the arc welding system, and drive the welding torch (41) of the arc welding system to move along the workpiece axis and the inner wall of the workpiece circumferentially. The water cooling system (5) is connected to the end of the arc welding system (4) away from the workpiece by a support. The fixed tube (6) is fixed on the aluminum tube (34). The distance between the nozzle of the water cooling system and the welding gun of the arc welding system is greater than the thickness of the workpiece wall. That is, when the welding gun is inserted into the workpiece, the water cooling system is located at the opposite position on the outer wall of the workpiece. During the welding process, the welding system and the water cooling system move synchronously along the axis of the workpiece. The water cooling device sprays water to cool the welding position synchronously. The top of the workpiece support system (8) is provided with rollers. The rollers abut against the lower surface of the workpiece to support the workpiece. The workpiece rotation control system (7) can drive the workpiece to rotate along the axis. The control system (9) is connected to the servo motion mechanism (2), the arc welding system (4), the water cooling system (5), and the workpiece rotation control system (7) respectively.

2. The method for preparing the composite pipe for a clean power generation system according to claim 1, characterized in that, The stainless steel pipe is a 316L stainless steel pipe. Before arc welding, the stainless steel pipe is pretreated to remove surface oil and oxide film.

3. The method for preparing the composite pipe for a clean power generation system according to claim 1, characterized in that, The preparation method of the Fe-Cr-Mn alloy welding wire includes the following steps: mixing the components according to the mass percentage to obtain a metal powder core, then filling it into a molded metal groove, sealing it, and then drawing it multiple times on a wire drawing machine to obtain a welding wire of the required diameter.

4. The method for preparing the composite pipe for a clean power generation system according to claim 1, characterized in that, The inert gas is 99.99% argon, and the inert gas flow rate is 10L / min-20L / min.

5. The method for preparing the composite pipe for a clean system in thermal power generation according to claim 1, characterized in that, The welding process parameters in step (1) are: current intensity 150-400A, voltage intensity 16-32V, and wire feeding rate 2.0-6.0m / min.

6. The method for preparing the composite pipe for a clean power generation system according to claim 1, characterized in that, The thickness of a single Fe-Cr-Mn alloy deposition is 3-5 mm, and the number of repeated depositions is 1-8 times, with the total thickness of the Fe-Cr-Mn alloy deposition set at 3 mm-30 mm.

7. A composite pipe for a clean system in thermal power generation, characterized in that, It is prepared by the method described in any one of claims 1-6.

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