A corrosion-resistant and high-stability steel pipe and its preparation method

Abstract

The present invention relates to the technical field of advanced nonferrous metal materials, and discloses a corrosion-resistant and high-stability steel pipe and a preparation method thereof, wherein a protective layer is respectively covered on the inner surface and the outer surface of the steel pipe; wherein the inner surface of the steel pipe is covered with a rare earth-based protective layer; and the outer surface is covered with an aluminum oxide-based protective layer; wherein the rare earth-based protective layer and the aluminum oxide-based protective layer have the same thickness, both of which are 0.35-1.0 mm; and the rare earth-based protective layer and the aluminum oxide-based protective layer are both formed by a spraying process; the corrosion-resistant and high-stability steel pipe prepared by the present invention mainly forms a different protective layer on the inner wall and the outer surface of the steel pipe, respectively, and according to the difference between the inner wall environment and the outer wall environment of the steel pipe, a rare earth-based protective layer is formed on the inner wall of the steel pipe and an aluminum oxide-based protective layer is formed on the outer wall of the steel pipe, respectively, and the inner wall of the steel pipe needs to directly contact the conveying medium, therefore, it has a higher requirement for high corrosion resistance, while the outer wall of the steel pipe will not contact the conveying medium, therefore, it does not need excessively high corrosion resistance.

Description

Technical Field

[0001] The invention relates to the technical field of advanced nonferrous metal materials, and in particular to a corrosion-resistant and high-stability steel pipe and a preparation method thereof. Background Art

[0002] Steel pipe is a hollow, long, round steel product, which is widely used in industrial pipelines such as petroleum, chemical, medical, food, light industry, mechanical instruments, and mechanical structural components.

[0003] Anti-corrosion steel pipe is a steel pipe with certain anti-corrosion ability. It can effectively prevent or slow down the corrosion of chemical or electrochemical reactions during transportation and use. Therefore, the use of anti-corrosion steel pipe is increasing.

[0004] In our daily production and life, anti-corrosion steel pipes also play an extremely important role. Especially when transmitting some corrosive media, it is necessary to ensure that the inner surface of the steel pipe has good corrosion resistance and wear resistance. The improvement of wear resistance is mainly to reduce the wear of the steel pipe by the medium during transportation, while the improvement of corrosion resistance is mainly to prevent the transportation medium from corroding the inner surface of the steel pipe, which not only easily causes steel pipe leakage, but also introduces reactive impurities into the transportation medium during the corrosion process of the steel pipe, causing a significant reduction in the quality of the transportation medium and affecting the application of the transportation medium.

[0005] Although the steel pipes treated by the prior art have certain corrosion resistance, their wear resistance is relatively poor. After a long period of conveying the medium, the corrosion-resistant layer will be worn away due to wear, resulting in a significant reduction in its corrosion resistance. At the same time, the prior art performs uniform corrosion-resistant treatment on steel pipes, which is relatively costly, and due to the different environments of the inner and outer walls of the steel pipe, excessive corrosion protection may occur.

[0006] Based on this, we proposed a corrosion-resistant and high-stability steel pipe, hoping to solve the shortcomings of the existing technology. Summary of the invention

[0007] 1. Technical issues to be solved

[0008] In view of the deficiencies in the prior art, the present invention provides a corrosion-resistant and high-stability steel pipe and a preparation method thereof.

[0009] (II) Technical solution

[0010] To achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0011] A corrosion-resistant and high-stability steel pipe, with a protective layer covered on the inner surface and the outer surface of the steel pipe respectively;

[0012] Among them, the inner surface of the steel pipe is covered with a rare earth-based protective layer;

[0013] The outer surface is covered with an aluminum oxide-based protective layer;

[0014] The rare earth-based protective layer and the alumina-based protective layer have the same thickness, both of which are 0.35-1.0 mm;

[0015] The rare earth-based protective layer and the aluminum oxide-based protective layer are both formed by a spraying process.

[0016] As a further technical solution, the steel pipe is pretreated before spraying:

[0017] First, clean the steel pipe, then dry it, then shot peen the inner and outer surfaces of the steel pipe respectively, then preheat the shot peened steel pipe, and finally maintain a constant temperature.

[0018] As a further technical solution, the shot peening process is:

[0019] Use No. 70 spring steel shot, the shot peening distance is 100mm, and the shot peening angle is 35°;

[0020] The preheating treatment is:

[0021] Place the steel pipe in a resistance furnace, heat it to 300-350℃, keep it warm for 2 hours, then adjust the temperature to 110℃ and keep it constant.

[0022] As a further technical solution: the rare earth-based protective layer is obtained by plasma spraying rare earth-based spray powder;

[0023] The alumina-based protective layer is obtained by plasma spraying alumina-based spray powder.

[0024] As a further technical solution, the rare earth-based spray powder comprises, by weight: 1.0-1.4 parts of cerium hydride powder, 50-56 parts of silicon dioxide powder, 18-22 parts of aluminum oxide powder, and 10-14 parts of silicon carbide powder.

[0025] As a further technical solution, the weight ratio of the cerium hydride powder to the silicon carbide powder is 1:10.

[0026] As a further technical solution, the plasma spraying process using rare earth-based spray powder is:

[0027] A mixture of nitrogen and hydrogen is used as the working gas, with the volume ratio of hydrogen to the working gas being 3-5%, the moving speed of the spray gun being 850-900 mm / s, and the spray distance being 5 cm.

[0028] As a further technical solution, the alumina-based spray powder comprises, by weight: 40-50 parts of silicon dioxide powder, 36-42 parts of alumina powder, and 6-7 parts of zirconium oxide powder, and the weight ratio of the alumina powder to the zirconium oxide powder is 6:1.

[0029] As a further technical solution, the plasma spraying process using alumina-based spray powder is:

[0030] Argon was used as the working gas, the spray gun movement speed was 800-850 mm / s, and the spray distance was 8 cm.

[0031] The current of plasma spraying is 680A and the power is 50kW.

[0032] A method for preparing a corrosion-resistant and high-stability steel pipe. First, the steel pipe is subjected to ultrasonic and magnetic leakage nondestructive testing, and then pre-treated before spraying. After the pre-treatment is completed, the inner and outer walls of the steel pipe are sprayed respectively, and then formed.

[0033] (III) Beneficial effects

[0034] Compared with the prior art, the present invention provides a corrosion-resistant and high-stability steel pipe, which has the following beneficial effects:

[0035] The corrosion-resistant and high-stability steel pipe prepared by the present invention mainly forms a different protective layer on the inner wall and the outer surface of the steel pipe respectively. According to the difference between the inner wall environment and the outer wall environment of the steel pipe, a rare earth-based protective layer is formed on the inner wall of the steel pipe and an alumina-based protective layer is formed on the outer wall of the steel pipe respectively. The inner wall of the steel pipe needs to directly contact the conveying medium, so it has a higher requirement for high corrosion resistance, while the outer wall of the steel pipe will not contact the conveying medium, so it does not require excessively high corrosion resistance. Therefore, the present invention performs treatment according to the environments of the two, which is more economical. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] A corrosion-resistant and high-stability steel pipe, with a protective layer covered on the inner surface and the outer surface of the steel pipe respectively;

[0038] Among them, the inner surface of the steel pipe is covered with a rare earth-based protective layer;

[0039] The outer surface is covered with an aluminum oxide-based protective layer;

[0040] The rare earth-based protective layer and the alumina-based protective layer have the same thickness, both of which are 0.35-1.0 mm;

[0041] Among them, the thickness of the rare earth-based protective layer is preferably 0.5-0.8 mm, more preferably 0.68 mm, and the thickness of the alumina-based protective layer is preferably 0.35-0.45 mm, more preferably 0.40 mm;

[0042] The rare earth-based protective layer and the aluminum oxide-based protective layer are both formed by a spraying process.

[0043] The steel pipe is pre-treated before spraying:

[0044] First, clean the steel pipe, then dry it, then shot peen the inner and outer surfaces of the steel pipe respectively, then preheat the shot peened steel pipe, and finally maintain a constant temperature.

[0045] The steel pipe is cleaned by using anhydrous ethanol, acetone and clean water for 10 minutes respectively. When cleaning in acetone, ultrasonic treatment can be used to improve the cleaning efficiency and reduce the amount of attachment on the surface of the steel pipe.

[0046] The shot peening treatment is as follows:

[0047] Use No. 70 spring steel shot, the shot peening distance is 100mm, and the shot peening angle is 35°;

[0048] During shot peening, the pressure of shot peening is preferably 0.55 MPa;

[0049] The preheating treatment is:

[0050] Place the steel pipe in a resistance furnace, heat it to 300-350℃, keep it warm for 2 hours, then adjust the temperature to 110℃ and keep it constant.

[0051] The rare earth-based protective layer is obtained by plasma spraying rare earth-based spray powder;

[0052] The alumina-based protective layer is obtained by plasma spraying alumina-based spray powder.

[0053] The rare earth-based spray powder comprises, by weight: 1.0-1.4 parts of cerium hydride powder, 50-56 parts of silicon dioxide powder, 18-22 parts of aluminum oxide powder, and 10-14 parts of silicon carbide powder.

[0054] The weight ratio of the cerium hydride powder to the silicon carbide powder is 1:10.

[0055] The plasma spraying process using rare earth-based spray powder is:

[0056] A mixture of nitrogen and hydrogen is used as the working gas, with the volume ratio of hydrogen to the working gas being 3-5%, the moving speed of the spray gun being 850-900 mm / s, and the spray distance being 5 cm.

[0057] The current of the plasma spraying was 630A and the power was 40kW.

[0058] During spraying, plasma spraying heats the rare earth-based spray powder to a molten state. The different heating times caused by different particle sizes result in different molten states. The cooling times after impacting the substrate surface are different, resulting in certain pores in the coating. Therefore, the present invention introduces a certain mass ratio of cerium hydride powder and silicon carbide powder. The addition of cerium hydride powder has a significant effect on inhibiting oxidation, and at the same time greatly improves the density of the rare earth-based protective layer, especially when combined with silicon carbide powder, which can further promote tissue densification.

[0059] The alumina-based spray powder comprises, by weight: 40-50 parts of silicon dioxide powder, 36-42 parts of alumina powder, and 6-7 parts of zirconium oxide powder, wherein the weight ratio of the alumina powder to the zirconium oxide powder is 6:1.

[0060] The plasma spraying process using alumina-based spray powder is:

[0061] Argon was used as the working gas, the spray gun movement speed was 800-850 mm / s, and the spray distance was 8 cm.

[0062] The current of plasma spraying is 680A and the power is 50kW.

[0063] A method for preparing a corrosion-resistant and high-stability steel pipe. First, the steel pipe is subjected to ultrasonic and magnetic leakage nondestructive testing, and then pre-treated before spraying. After the pre-treatment is completed, the inner and outer walls of the steel pipe are sprayed respectively, and then formed.

[0064] The rare earth-based protective layer and the alumina-based protective layer respectively formed on the surface of the steel pipe in the present invention have densified tissue structures, which can not only effectively block moisture and oxygen in the air from contacting the surface of the steel pipe, but also the rare earth-based protective layer and the alumina-based protective layer in this application also have excellent chemical corrosion resistance, thereby broadening their application fields.

[0065] The following are specific embodiments:

[0066] Example 1

[0067] A corrosion-resistant and high-stability steel pipe, with a protective layer covered on the inner and outer surfaces of the steel pipe respectively; wherein the inner surface of the steel pipe is covered with a rare earth-based protective layer; and the outer surface is covered with an alumina-based protective layer; wherein the thickness of the rare earth-based protective layer is preferably 0.5 mm, and the thickness of the alumina-based protective layer is preferably 0.3 mm; and both the rare earth-based protective layer and the alumina-based protective layer are formed by a spraying process. The steel pipe is pretreated before spraying: first, the steel pipe is cleaned, then dried, and then the inner and outer surfaces of the steel pipe are shot peened respectively, and then the shot peened steel pipe is preheated, and the preheating treatment is: the steel pipe is placed in a resistance furnace, heated to 300°C, kept warm for 2 hours, and then the temperature is adjusted to 110°C and kept constant. Finally, keep the temperature constant. The shot peening treatment is as follows: No. 70 spring steel shot is used, the shot peening distance is 100mm, the shot peening angle is 35°, and the shot peening pressure is preferably 0.55MPa; the rare earth-based protective layer is obtained by plasma spraying using rare earth-based spray powder; the alumina-based protective layer is obtained by plasma spraying using alumina-based spray powder. The rare earth-based spray powder includes, by weight, 1.0 part of cerium hydride powder, 50 parts of silicon dioxide powder, 18 parts of alumina powder, and 10 parts of silicon carbide powder. The weight ratio of the cerium hydride powder to the silicon carbide powder is 1:10. The plasma spraying process using rare earth-based spray powder is as follows: a mixed gas of nitrogen and hydrogen is used as the working gas, the volume ratio of hydrogen to the working gas is 3%, the moving speed of the spray gun is 850mm / s, and the spray distance is 5cm. The alumina-based spray powder includes, by weight, 40 parts of silicon dioxide powder, 36 parts of alumina powder, and 6 parts of zirconium oxide powder, and the weight ratio of the alumina powder to the zirconium oxide powder is 6:1. The plasma spraying process using the alumina-based spray powder is as follows: argon gas is used as the working gas, the spray gun movement speed is 800 mm / s, and the spray distance is 8 cm. The current of the plasma spraying is 680 A and the power is 50 kW.

[0068] Example 2

[0069] A corrosion-resistant and high-stability steel pipe, with a protective layer covered on the inner and outer surfaces of the steel pipe respectively; wherein the inner surface of the steel pipe is covered with a rare earth-based protective layer; the outer surface is covered with an alumina-based protective layer; wherein the thickness of the rare earth-based protective layer is 0.68mm, and the thickness of the alumina-based protective layer is preferably 00.40mm; the rare earth-based protective layer and the alumina-based protective layer are both formed by a spraying process. The steel pipe is pretreated before spraying: first, the steel pipe is cleaned, then dried, and then the inner and outer surfaces of the steel pipe are shot peened respectively, and then the shot peened steel pipe is preheated, and the preheating treatment is: the steel pipe is placed in a resistance furnace, heated to 320°C, kept warm for 2 hours, and then the temperature is adjusted to 110°C and kept constant. Finally, keep the temperature constant. The shot peening treatment is as follows: No. 70 spring steel shot is used, the shot peening distance is 100mm, the shot peening angle is 35°, and the shot peening pressure is preferably 0.55MPa; the rare earth-based protective layer is obtained by plasma spraying using rare earth-based spray powder; the alumina-based protective layer is obtained by plasma spraying using alumina-based spray powder. The rare earth-based spray powder includes, by weight, 1.2 parts of cerium hydride powder, 51 parts of silicon dioxide powder, 19 parts of alumina powder, and 12 parts of silicon carbide powder. The weight ratio of the cerium hydride powder to the silicon carbide powder is 1:10. The plasma spraying process using rare earth-based spray powder is as follows: a mixed gas of nitrogen and hydrogen is used as the working gas, the volume ratio of hydrogen to the working gas is 3.5%, the moving speed of the spray gun is 880mm / s, and the spray distance is 5cm. The alumina-based spray powder includes, by weight, 45 parts of silicon dioxide powder, 39 parts of alumina powder, and 6.5 parts of zirconium oxide powder, and the weight ratio of the alumina powder to the zirconium oxide powder is 6:1. The plasma spraying process using the alumina-based spray powder is as follows: argon gas is used as the working gas, the spray gun movement speed is 820 mm / s, and the spray distance is 8 cm. The current of the plasma spraying is 680 A and the power is 50 kW.

[0070] Example 3

[0071] A corrosion-resistant and high-stability steel pipe, with a protective layer covered on the inner and outer surfaces of the steel pipe respectively; wherein the inner surface of the steel pipe is covered with a rare earth-based protective layer; and the outer surface is covered with an alumina-based protective layer; wherein the thickness of the rare earth-based protective layer is 0.6 mm, and the thickness of the alumina-based protective layer is preferably 0.38 mm; the rare earth-based protective layer and the alumina-based protective layer are both formed by a spraying process. The steel pipe is pretreated before spraying: first, the steel pipe is cleaned, then dried, and then the inner and outer surfaces of the steel pipe are shot peened respectively, and then the shot peened steel pipe is preheated, and the preheating treatment is: the steel pipe is placed in a resistance furnace, heated to 330°C, kept warm for 2 hours, and then the temperature is adjusted to 110°C and kept constant. Finally, keep the temperature constant. The shot peening treatment is as follows: No. 70 spring steel shot is used, the shot peening distance is 100mm, the shot peening angle is 35°, and the shot peening pressure is preferably 0.55MPa; the rare earth-based protective layer is obtained by plasma spraying with rare earth-based spray powder; the alumina-based protective layer is obtained by plasma spraying with alumina-based spray powder. The rare earth-based spray powder includes, by weight: 1.3 parts of cerium hydride powder, 54 parts of silicon dioxide powder, 20 parts of alumina powder, and 13 parts of silicon carbide powder. The weight ratio of the cerium hydride powder to the silicon carbide powder is 1:10. The plasma spraying process using rare earth-based spray powder is as follows: a mixed gas of nitrogen and hydrogen is used as the working gas, the volume ratio of hydrogen to the working gas is 4%, the moving speed of the spray gun is 860mm / s, and the spray distance is 5cm. The alumina-based spray powder includes, by weight, 48 parts of silicon dioxide powder, 37.2 parts of alumina powder, and 6.2 parts of zirconium oxide powder, and the weight ratio of the alumina powder to the zirconium oxide powder is 6:1. The plasma spraying process using the alumina-based spray powder is as follows: argon gas is used as the working gas, the spray gun movement speed is 830 mm / s, and the spray distance is 8 cm. The current of the plasma spraying is 680 A and the power is 50 kW.

[0072] Example 4

[0073] A corrosion-resistant and high-stability steel pipe, with a protective layer covered on the inner and outer surfaces of the steel pipe respectively; wherein the inner surface of the steel pipe is covered with a rare earth-based protective layer; and the outer surface is covered with an alumina-based protective layer; wherein the thickness of the rare earth-based protective layer is 0.8 mm, and the thickness of the alumina-based protective layer is preferably 0.45 mm; the rare earth-based protective layer and the alumina-based protective layer are both formed by a spraying process. The steel pipe is pretreated before spraying: first, the steel pipe is cleaned, then dried, and then the inner and outer surfaces of the steel pipe are shot peened respectively, and then the shot peened steel pipe is preheated, and the preheating treatment is: the steel pipe is placed in a resistance furnace, heated to 350°C, kept warm for 2 hours, and then the temperature is adjusted to 110°C and kept constant. Finally, keep the temperature constant. The shot peening treatment is as follows: No. 70 spring steel shot is used, the shot peening distance is 100mm, the shot peening angle is 35°, and the shot peening pressure is preferably 0.55MPa; the rare earth-based protective layer is obtained by plasma spraying with rare earth-based spray powder; the alumina-based protective layer is obtained by plasma spraying with alumina-based spray powder. The rare earth-based spray powder includes, by weight: 1.4 parts of cerium hydride powder, 56 parts of silicon dioxide powder, 22 parts of alumina powder, and 14 parts of silicon carbide powder. The weight ratio of the cerium hydride powder to the silicon carbide powder is 1:10. The plasma spraying process using rare earth-based spray powder is as follows: a mixed gas of nitrogen and hydrogen is used as the working gas, the volume ratio of hydrogen to the working gas is 5%, the moving speed of the spray gun is 900mm / s, and the spray distance is 5cm. The alumina-based spray powder includes, by weight, 50 parts of silicon dioxide powder, 42 parts of alumina powder, and 7 parts of zirconium oxide powder, and the weight ratio of the alumina powder to the zirconium oxide powder is 6:1. The plasma spraying process using the alumina-based spray powder is as follows: argon gas is used as the working gas, the spray gun moves at a speed of 850 mm / s, and the spray distance is 8 cm. The current of the plasma spraying is 680 A, and the power is 50 kW.

[0074] Comparative Example 1:

[0075] On the basis of Example 1, the raw materials were adjusted, the rare earth-based spray powder was not added with cerium hydride powder, and the rest of the technical scheme remained unchanged.

[0076] Comparative Example 2:

[0077] On the basis of Example 1, the raw materials were adjusted, zirconium oxide was not added to the alumina-based spray powder, and the rest of the technical solutions remained unchanged.

[0078] test:

[0079] The microhardness of the cross section of the rare earth-based protective layer samples in the embodiments and comparative examples was tested using a microhardness tester, with a loading load of 2.94 N and a loading time of 20 s. Five different points were tested for each sample, and the average value was taken.

[0080] Table 1

[0081] Hardness HV Example 1 737 Example 2 742 Example 3 732 Example 4 739 Comparative Example 1 702

[0082] It can be seen from Table 1 that the rare earth-based protective layer formed on the inner wall of the steel pipe according to the present invention has excellent surface hardness, and the improvement of the surface hardness can greatly improve the friction resistance of the inner wall of the steel pipe.

[0083] The phase structure of the coating was analyzed by X-ray diffractometer, Cu target Kα diffraction, the scanning range was 10° to 90°, the scanning speed was 0.02 (°) / min, the cross-section and surface morphology of the coating were observed by scanning electron microscopy, and the cross-section of the rare earth-based protective layer and the aluminum oxide-based protective layer of the embodiment and the comparative example was analyzed by Image J software to calculate the porosity:

[0084] Table 2

[0085]

[0086] It can be seen from Table 3 that the rare earth-based protective layer and the alumina-based protective layer formed on the inner wall and the outer surface of the steel pipe by the method of the present invention have lower porosity, and the density of the two surfaces is greatly improved. By improving the density of the rare earth-based protective layer and the alumina-based protective layer, it is possible to effectively prevent oxygen and moisture in the air from contacting the surface of the steel pipe, thereby reducing the probability of corrosion and improving the anti-corrosion effect of the steel pipe.

[0087] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A corrosion-resistant and high-stability steel pipe, characterized in that: A protective layer is respectively covered on the inner surface and the outer surface of the steel pipe; Among them, the inner surface of the steel pipe is covered with a rare earth-based protective layer; The outer surface is covered with an aluminum oxide-based protective layer; The rare earth-based protective layer and the alumina-based protective layer have the same thickness, both of which are 0.35-1.0 mm; The rare earth-based protective layer and the alumina-based protective layer are both formed by a spraying process; the steel pipe is pretreated before spraying: First, the steel pipe is cleaned and then dried, and then the inner and outer surfaces of the steel pipe are shot peened respectively, and then the shot peened steel pipe is preheated and finally kept at a constant temperature; the shot peening treatment is: Use No. 70 spring steel shot, the shot peening distance is 100mm, and the shot peening angle is 35°; The preheating treatment is: The steel pipe is placed in a resistance furnace, heated to 300-350°C, kept warm for 2 hours, and then adjusted to 110°C to maintain a constant temperature; the rare earth-based protective layer is obtained by plasma spraying rare earth-based spray powder; The alumina-based protective layer is obtained by plasma spraying alumina-based spray powder; the rare earth-based spray powder comprises, by weight: 1.0-1.4 parts of cerium hydride powder, 50-56 parts of silicon dioxide powder, 18-22 parts of alumina powder, and 10-14 parts of silicon carbide powder; The alumina-based spray powder comprises, by weight: 40-50 parts of silicon dioxide powder, 36-42 parts of alumina powder, and 6-7 parts of zirconium oxide powder, and the weight ratio of the alumina powder to the zirconium oxide powder is 6:

1.

2. The corrosion-resistant and high-stability steel pipe according to claim 1, characterized in that: The weight ratio of the cerium hydride powder to the silicon carbide powder is 1:

10.

3. The corrosion-resistant and high-stability steel pipe according to claim 1, characterized in that: The plasma spraying process using rare earth-based spray powder is: A mixture of nitrogen and hydrogen is used as the working gas, with the volume ratio of hydrogen to the working gas being 3-5%. The moving speed of the spray gun is 850-900 mm / s, and the spray distance is 5 cm.

4. The corrosion-resistant and high-stability steel pipe according to claim 1, characterized in that: The plasma spraying process using alumina-based spray powder is: Argon is used as the working gas, the spray gun movement speed is 800-850mm / s, and the spray distance is 8cm; The current of plasma spraying is 680A and the power is 50kW.

5. A method for preparing a corrosion-resistant and high-stability steel pipe according to any one of claims 1 to 4, characterized in that: First, the steel pipe is subjected to ultrasonic and magnetic leakage nondestructive testing, and then pre-treated before spraying. After the pre-treatment is completed, the inner and outer walls of the steel pipe are sprayed and formed respectively.

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