Preparation method and device of centrifugal sintering type slender pipe inner wall coating

Abstract

The invention discloses a centrifugal sintering method and device for an inner wall coating of a slender pipe, and relates to the technical field of part surface strengthening treatment. The slender pipe and a high-speed motor are arranged in a vacuum box; one end of the slender pipe is positioned and supported by a bearing, and the other end is clamped by a chuck which is connected with the output end of a high-speed motor; a vacuum pump and an air pump are arranged on the outer side of the vacuum box, the vacuum pump is used for adjusting air pressure in the vacuum box, and the air pump is used for coating the inner side wall of the long and thin pipe with slurry; and the coating on the inner side wall of the slender pipe is heated through a graphite rod. According to the method, a pulse temperature field formed by a graphite rod through transient current is used as a radiation heat source, and a centrifugal assisted slender pipe inner wall coating is added, so that the slender pipe inner wall coating which is high in binding force, uniform and compact is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of part surface strengthening treatment, and particularly relates to a centrifugal sintering method and device for an inner wall coating of an elongated tube. Background Art

[0002] In the petrochemical field, since pipelines are usually used in extremely challenging operating environments, the inner walls of pipelines are often severely damaged, including corrosion and physical damage, etc. These damages will result in huge property losses and potential risks of personal injury. Therefore, it is necessary to strengthen the inner walls of many tubular workpieces, including pipelines for transporting corrosive media in chemical enterprises, components in heat exchangers, and workpieces for collecting samples during oil exploration and chemical analysis, etc. To solve this problem, a series of pipeline inner wall surface treatment technologies have been developed to improve the properties of the pipeline inner walls, such as hardness, wear resistance, high temperature resistance, and corrosion resistance.

[0003] Common ceramic layer sintering methods include: plasma spraying, laser cladding, chemical vapor deposition, etc.

[0004] Plasma spraying is to spray ceramic powder onto the metal surface using a plasma flame, and then cure the ceramic layer through high-temperature sintering. It can process workpieces with large and complex shapes, but the density and roughness of the coating are relatively high, and further high-temperature sintering is required to improve the performance. Moreover, due to the limitations of the spraying equipment, it is impossible to process the inner wall of a straight tube with an ultra-small inner diameter.

[0005] Laser cladding is to use a laser beam to melt ceramic powder and precisely clad it onto the metal surface to form a ceramic coating. It can achieve high precision and low heat output, and is suitable for processing workpieces with complex shapes and high requirements. However, due to the limitations of its equipment volume and processing method, it is difficult to process the inner wall of a straight tube with an ultra-small inner diameter.

[0006] Chemical vapor deposition is to deposit a ceramic thin film on the workpiece surface using gas chemical reactions, which has a relatively high purity. However, it needs to face the problems of dealing with harmful gases and waste gas emissions, and it is also impossible to process the inner wall of a straight tube with an ultra-small inner diameter.

[0007] Nowadays, most laser claddings in industry use lasers such as carbon dioxide lasers and fiber lasers to generate a laser beam with a high energy density and irradiate it onto a flat substrate pre-coated with powder. This method is mostly suitable for flat cladding, so it greatly limits the cladding range and the use of expensive lasers greatly increases the cost.

[0008] At present, elongated tubes are widely used in industries such as petroleum and chemical industries. However, their inner walls are extremely prone to wear and corrosion under complex working conditions, resulting in a greatly shortened service life. Summary of the Invention

[0009] In view of the deficiencies in the prior art, the present invention provides a centrifugal sintering method and device for the inner wall coating of a slender tube. By means of centrifugal assistance and using the pulsed temperature field formed by passing a transient current through a graphite rod as a radiation heat source, an inner wall coating of the slender tube is obtained to prepare an inner wall coating of the slender tube with strong bonding force, uniform density and compactness.

[0010] The present invention achieves the above technical objectives through the following technical means.

[0011] A device for preparing an inner wall coating of a centrifugal sintering type slender tube includes a slender tube, a vacuum chamber, a chuck and a high-speed motor; the vacuum chamber is internally provided with a slender tube and a high-speed motor; one end of the slender tube is positioned and supported by a bearing, and the other end is clamped by a chuck, and the chuck is connected to the output end of the high-speed motor; a vacuum pump and an air pump are arranged outside the vacuum chamber, wherein the vacuum pump is used to adjust the air pressure in the vacuum chamber, and the air pump is used to coat the slurry on the inner side wall of the slender tube; the coating on the inner side wall of the slender tube is heated by a graphite rod.

[0012] In the above solution, the electrode is connected to a controllable DC power supply through a wire; the power of the controllable DC power supply is 0.8 - 2.5 KW.

[0013] In the above solution, the electrode is inserted into the slender tube with a coating.

[0014] In the above solution, the diameter of the slender tube is not greater than 10 mm.

[0015] In the above solution, when the coating needs to be heated, one end of the graphite rod is arranged on an adjustable lifting table through an electrode, and the other end extends into the slender tube.

[0016] In the above solution, the air pump transports the slurry to the inner side of the slender tube through a pipeline, and during the transportation process, the slender tube rotates at a certain speed.

[0017] A preparation method for a device for preparing an inner wall coating of a centrifugal sintering type slender tube includes the following steps:

[0018] Step 1: Treat the inner wall of the slender tube;

[0019] Step 2: Ball mill powder A and powder B to obtain a mixed powder, and mix it with a binder in proportion and ball mill to obtain a slurry;

[0020] Step 3: Rotate the slender tube at a low speed, and use an airless spray gun to evenly spray the slurry on the inner wall of the slender tube;

[0021] Step 4: The slender tube rotates at a high speed, and the inner wall coating of the slender tube is sintered by using the pulsed temperature field formed by passing an instantaneous current through the electrode, ensuring that the powder A with low melting point and small particle size is completely melted, and the powder B with high melting point and large particle size is not melted. The melted A uniformly wraps the unmelted powder B, and the powder B particles act as a skeleton in the coating, which can prevent the coating from shrinking;

[0022] Step 5: Cut off the current input. The high-speed motor continues to work until the inner wall of the slender tube cools down to room temperature, and then the high-speed motor stops working and the electrode is taken out.

[0023] In the above solution, in Step 3, when the slender tube rotates at a low speed, the rotation speed of the high-speed motor is 30 - 40 r / min.

[0024] In the above solution, in Step 4, when the slender tube rotates at a high speed, the rotation speed of the high-speed motor is 40 - 1200 r / min; the output current of the controllable DC power supply is 40 - 500 A, the voltage is 20 - 50 V, the power-on time is 30 - 60 s, and the vacuum pressure is -0.1 MPa.

[0025] In the above solution, in Step 2, the powders A and B are Ni60 powder and nano - CeO2 powder. The ball - milling rotation speed is set to 100 r / min, the total ball - milling duration is 2 h, the single - run duration is 2 min, and the single - pause duration is 2 min. Finally, the mixed powder of powders A and B is obtained; the mixed powder formed by powders A and B is mixed with the binder in a ratio of 10:1 to form a uniform slurry, and left standing for a period of time to remove the air inside the slurry.

[0026] After the present invention adopts the above technical solutions, the beneficial effects are as follows:

[0027] (1) The present invention controls the temperature to achieve complete melting of the powder A with low melting point and small particle size, and non - melting of the powder B with high melting point and large particle size. With the assistance of the centrifugal device, the two are uniformly combined. The powder particles with high melting point and large particle size act as a skeleton, playing a supporting role for the entire coating, and the coating will not shrink;

[0028] (2) The present invention uses a graphite rod as a radiation heat source, which has a wide radiation temperature range and small thermal inertia, can accurately control the temperature, and can adjust the heating and cooling speed of the coating by outputting pulsed current, preventing the coating from cracking, and has great practical value;

[0029] (3) The present invention realizes controllable pickling by attaching a layer of corrosion - resistant porous film on the airbag and inflating the airbag to lay the film on the inner wall of the slender tube;

[0030] (4) The centrifugal auxiliary device used in the present invention effectively guarantees the uniformity of the coating.

[0031] (5) The method of the present invention can prepare coatings with wear-resistant and corrosion-resistant properties, which can not only repair damaged surfaces but also play a role in isolating and preventing corrosion. The method of preparing a ceramic layer on the inner wall of an ultra-small inner diameter straight pipe is to energize a graphite rod extending into the inside of a circular pipe, heat the ceramic powder to a molten or semi-molten state, and finally achieve a metallurgical bond between the ceramic layer and the substrate. Using this technology, the operation is simple, the cost is low, and the heating speed is fast, with broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the coating on the slender pipe obtained by the centrifugal sintering method for the inner wall coating of the slender pipe related to the present invention;

[0033] Figure 2 Schematic process flow diagram of the method of the present invention;

[0034] Figure 3 Schematic diagram of pickling and texturing of the inner wall of the slender pipe;

[0035] Figure 4 Schematic diagram of the device of the present invention and the slurry spraying involved;

[0036] Figure 5 Schematic diagram of the device of the present invention and the centrifugal sintering involved.

[0037] Reference numerals:

[0038] 1 - Vacuum pump, 2 - Air valve, 3 - Bearing support, 4 - Slender pipe, 5 - Vacuum chamber, 6 - Chuck, 7 - High-speed motor, 8 - Moving base, 9 - Pipeline, 10 - Slurry, 11 - Air pump, 12 - Graphite rod, 13 - Electrode, 14 - Adjusting lifting table, 15 - Wire, 16 - Controllable DC power supply. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0041] In the present invention, unless otherwise clearly specified and defined, the terms "install", "connect", "join", "fix", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] A preparation method for an inner wall coating of a centrifugal sintered slender tubular shape, comprising the following steps:

[0043] (1) First, clean the inner wall of the pipe fitting. Before removing the oil stain on the inner wall of the slender pipe 4, cover a layer of corrosion-resistant porous film on the inner wall to avoid damaging the inner wall of the slender pipe 4 during subsequent operations. First, wrap the porous film on the surface of a slender cylindrical airbag, then insert the airbag into the inner wall of the slender pipe 4 and slowly inflate the airbag. At this time, the volume of the airbag gradually increases. When the airbag is about to contact the inner wall surface of the slender pipe 4, it will evenly squeeze the porous film onto the inner wall of the slender pipe 4. Finally, carefully and slowly remove the airbag to avoid affecting the distribution of the film when removing it. After covering the film, pickle the inner wall. Use a sprayer to spray the diluted HCl solution in the axial direction of the slender straight pipe. Repeat this 2 - 3 times to complete the cleaning of the inner wall, and then leave the workpiece in a cool and dry environment. Finally, carefully take out the film with slender tweezers to avoid insufficient bonding between the subsequent ceramic powder and the inner wall of the slender pipe 4, which may affect the quality of the sintered layer. Then clean and dry the slender pipe 4 to wash away the residual HCl solution on the inner wall;

[0044] (2) Add powder A with a high melting point and large particle size and powder B with a low melting point and small particle size into a ball milling tank in a predetermined ratio. During the ball milling process, fill the tank with Ar gas and seal it. Set the ball milling speed to 100 r / min, the total ball milling duration to 2 h, the single - run duration to 2 min, and the single - pause duration to 2 min. Finally, obtain the mixed powder of A and B.

[0045] (3) Referring to the ball milling parameters in step (2), mix the mixed powder and the binder in a ratio of 10:1 to form a uniform slurry, and let it stand for a period of time to remove the air inside the slurry.

[0046] (4) Add the prepared slurry 10 into the slurry box. The slurry box is connected to an air pump 11 through a pipeline 9 with a nozzle. One end of a slender tube 4 passes through a bearing support 3 connected to the inner wall of a vacuum box 5, and the other end is connected to a high - speed motor 7 placed on a moving base 8 through a chuck 6. Insert the slender nozzle 9 at the front end of the pipeline into the interior of the slender tube 4. Start the high - speed motor 7 and make the slender tube 4 rotate at a speed of 30 - 40 r / min. The nozzle 9 reciprocates along the axis of the slender tube 4 so that the slurry can be evenly coated on the inner wall. After removing the nozzle 9, the high - speed motor 7 continues to run for 5 min.

[0047] (5) Insert a graphite rod 12 into the slender tube 4. An electrode 13 clamps the graphite rod 12 and is fixed on an adjustable lifting platform 14. Adjust the height of the lifting platform 14 to ensure that the graphite rod 12 is concentric with the slender tube 4. Finally, connect the electrode 13 and a controllable DC power supply 16 with a wire 15.

[0048] (6) Close the vacuum box 5, open the vacuum pump 1 and the air valve 2, evacuate the air inside the vacuum box 5 so that its air pressure is - 0.1 MPa, and then close the air valve 2 and the vacuum pump 1.

[0049] (7) Start the high - speed motor 7 again, make it rotate at a speed of 40 - 1200 r / min. After stable operation, turn on the DC power supply 16, set the current to 40 - 500 A, the voltage to 20 - 50 V, and the power - on time to 30 - 60 s. Pass a transient current through the graphite rod 12 to form a pulsed temperature field. Control the magnitude of the current passed to control the temperature radiated by the graphite rod 12, ensuring that the B particles with low melting point and small particle size are completely melted, and the A particles with high melting point and large particle size are not melted. Under the action of centrifugal force, the A particles will be evenly dispersed, and the molten B particles will be evenly spread on the surface of the textured inner wall and tightly wrap the A particles. In the coating formed in this way, the B powder acts as a binder phase and the A powder acts as a skeleton, which can effectively improve the strength of the coating.

[0050] (8) Turn off the power supply 16, and the high - speed motor 7 continues to operate until the inner wall of the slender tube 4 cools down to room temperature, then the said slender pipe fitting is obtained.

[0051] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0052] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A centrifugal sintering elongated tube inner wall coating preparation device, characterized in that: The invention comprises a slender tube (4), a vacuum box (5), a chuck (6) and a high-speed motor (7); the vacuum box (5) has the slender tube (4) and the high-speed motor (7) built therein; one end of the slender tube (4) is positioned and supported by a bearing (3), and the other end is clamped by a chuck (6), and the chuck (6) is connected to the output end of the high-speed motor (7); a vacuum pump (1) and an air pump (11) are arranged outside the vacuum box (5), wherein the vacuum pump (1) is used to adjust the air pressure in the vacuum box (5), and the air pump (11) is used to apply slurry (10) to the inner wall of the slender tube (4); and the coating on the inner wall of the slender tube (4) is heated by a graphite rod (12).

2. The device for preparing the inner wall coating of a centrifugal sintering elongated tube according to claim 1, characterized in that: The electrode (13) is connected to a controllable DC power supply (16) via a wire; the power of the controllable DC power supply (16) is 0.8-2.5KW.

3. The device for preparing the inner wall coating of a centrifugal sintering elongated tube according to claim 1, characterized in that: The electrode (13) is inserted into the elongated tube (4) with the coating.

4. The device for preparing the inner wall coating of a centrifugal sintering elongated tube according to claim 1, characterized in that: The diameter of the slender tube (4) is no greater than 10 mm.

5. The device for preparing the inner wall coating of a centrifugal sintering elongated tube according to claim 1, characterized in that: When the coating needs to be heated, one end of the graphite rod (12) is arranged on the adjustment lifting platform (14) through the electrode (13), and the other end extends into the slender tube (4).

6. The device for preparing the inner wall coating of a centrifugal sintering elongated tube according to claim 1, characterized in that: The air pump (11) transports the slurry (10) to the inside of the slender tube (4) through the pipeline (9). During the transportation process, the slender tube (9) rotates at a certain speed.

7. The method for preparing the centrifugal sintering type elongated tube inner wall coating preparation device according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: treating the inner wall of the elongated tube (4); Step 2: ball-milling powder A and powder B to obtain a mixed powder, and mixing and ball-milling with a binder in proportion to obtain a slurry; Step 3: The slender tube (4) rotates at a low speed, and the slurry is evenly sprayed on the inner wall of the slender tube (4) using an airless spray gun; Step 4: The slender tube (4) rotates at a high speed, and a pulse temperature field formed by passing an instantaneous current through the electrode (13) is used to sinter the coating on the inner wall of the slender tube (4), so as to ensure that the powder A with a low melting point and a small particle size is completely melted, and the powder B with a high melting point and a large particle size is not melted, and the melted powder A evenly wraps the unmelted powder B, and the powder B particles act as a skeleton in the coating, which can prevent the coating from shrinking; Step 5: Cut off the current input, and the high-speed motor (7) continues to work until the inner wall of the slender tube (4) cools to room temperature, then the high-speed motor (7) stops working and the electrode (13) is taken out.

8. The method for preparing the centrifugal sintering type elongated tube inner wall coating preparation device according to claim 7, characterized in that: In step 3, when the slender tube (4) rotates at a low speed, the speed of the high-speed motor is 30 to 40 r / min.

9. The method for preparing the centrifugal sintering type elongated tube inner wall coating preparation device according to claim 7, characterized in that: In step 4, when the slender tube (4) rotates at high speed, the speed of the high-speed motor is 40 to 1200 r / min; the output current of the controllable DC power supply (16) is 40 to 500 A, the voltage is 20 to 50 V, the power-on time is 30 to 60 s, and the vacuum pressure is -0.1 MPa.

10. The method for preparing the centrifugal sintering type elongated tube inner wall coating preparation device according to claim 7, characterized in that: In step 2, powder A and powder B are Ni60 powder and nano CeO2 powder, the ball mill speed is set to 100r / min, the total ball milling time is 2h, the single operation time is 2min, and the single pause time is 2min, and finally a mixed powder of powder A and powder B is obtained; the mixed powder formed by powder A and powder B is mixed with a binder in a ratio of 10:1 into a uniform slurry, and the slurry is allowed to stand for a period of time to remove the air inside the slurry.

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