Corrosion-resistant treatment method for stainless steel pipe

Abstract

The invention relates to the technical field of stainless steel tube processing, in particular to a stainless steel tube corrosion-resistant treatment method which comprises the following steps: S1, placing a cleaned stainless steel tube in a treatment device which is in a nitrogen environment with the temperature of 30-50 DEG C and the pressure of 100-110 kPa, the elastic grinding material and nitrogen are mixed and sprayed to the inner surface and the outer surface of the stainless steel at the pressure intensity of 2-4 MPa for 15-20 min; s2, the temperature in the treatment device is raised to 500-530 DEG C, the pressure intensity of nitrogen is 130-160 kPa, and the temperature is kept for 13-16 h; s3, the temperature in the treatment device is reduced to 90-110 DEG C, the pressure intensity of nitrogen is reduced to 100-110 kPa, the elastic abrasive and the nitrogen are mixed, and the mixture is sprayed to the inner surface and the outer surface of the stainless steel at the pressure intensity of 5-7 MPa for 4-6 min; and S4, the temperature in the treatment device is raised to 550-580 DEG C, the nitrogen pressure intensity is 170-200 kPa, and the temperature is kept for 22-26 h. By implementing the method, the corrosion resistance and smoothness of the stainless steel pipe can be improved, and the influence on the appearance of the stainless steel pipe is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel pipe processing, in particular to a corrosion-resistant processing method for a stainless steel pipe. Background Art

[0002] After the stainless steel pipe is produced, it is generally subjected to corrosion resistance treatment, the main function of which is to improve the corrosion resistance of the stainless steel pipe so that it can adapt to the relatively harsh use environment. Secondly, the anti-corrosion treatment of stainless steel also has the advantages of extending the service life, reducing maintenance costs, ensuring fluid quality, preventing environmental pollution, improving system safety, enhancing market competitiveness, and meeting environmental protection requirements.

[0003] In the prior art, the corrosion resistance treatment of stainless steel pipes is generally divided into two categories: chemical treatment and physical treatment. Regardless of whether it is a chemical treatment or a physical treatment, the stainless steel surface must be pre-cleaned first to remove surface oil stains, welding spatter and metal defects. The chemical treatment method is generally to soak the pre-treated stainless steel pipe in a pickling solution and then in a passivation solution to form a dense passivation film to improve corrosion resistance; while the physical treatment method is to sandblast the pre-cleaned stainless steel pipe and then apply an anti-corrosion coating.

[0004] In these two ways, when the stainless steel pipe forms a passivation film or is coated with an anti-corrosion coating, it will inevitably come into contact with oxygen in the air, forming some easily detached oxide films, which will reduce the anti-corrosion performance of the stainless steel pipe. In addition, since the stainless steel pipe with a sprayed anti-corrosion layer has a low finish, it affects the appearance of the stainless steel pipe. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a corrosion-resistant treatment method for a stainless steel pipe, which can improve the corrosion resistance and smoothness of the stainless steel pipe and reduce the impact on the appearance of the stainless steel pipe.

[0006] In order to solve the above technical problems, a corrosion-resistant treatment method for a stainless steel pipe of the present invention comprises the following steps:

[0007] S1, placing the cleaned stainless steel pipe in a treatment device, which is in a nitrogen environment with a temperature of 30-50°C and a pressure of 100-110 kPa, mixing the elastic abrasive with nitrogen and spraying it toward the inner and outer surfaces of the stainless steel at a pressure of 2-4 MPa for 15-20 minutes;

[0008] S2, raising the temperature in the treatment device to 500-530°C and the nitrogen pressure to 130-160 kPa and maintaining for 13-16 hours;

[0009] S3, the temperature in the treatment device is reduced to 90-110°C, the nitrogen pressure is reduced to 100-110 kPa, the elastic abrasive is mixed with nitrogen and sprayed toward the inner and outer surfaces of the stainless steel at a pressure of 5-7 MPa for 4-6 minutes;

[0010] S4, raising the temperature in the treatment device to 550-580°C and the nitrogen pressure to 170-200 kPa and maintaining it for 22-26 hours.

[0011] As an improvement of the above scheme, in steps S1 and S3, the elastic abrasive and nitrogen mixture is sprayed on the stainless steel pipe in multiple spraying actions, and each spraying action lasts for 40-50 seconds, and the interval time between the spraying actions on the two adjacent sides is 10-20 seconds.

[0012] As an improvement of the above scheme, the processing device is provided with a spray mechanism and a rotating mechanism for driving the spray mechanism to rotate, the spray mechanism includes two outer spray vertical pipes arranged at intervals and an inner spray vertical pipe located in the middle of the two outer spray pipes, the outer spray pipe is provided with a plurality of outer spray ports for spraying the outer surface of the stainless steel pipe at intervals above and below, the inner spray pipe is provided with a plurality of inner spray ports for spraying the inner surface of the stainless steel pipe at intervals on the two back sides, and the elastic abrasive and nitrogen mixture is introduced into the outer spray pipe and the inner spray pipe through a pipeline to spray the inner and outer surfaces of the stainless steel.

[0013] As an improvement of the above solution, a plurality of jet ports are further provided in the processing device, and the jet ports are used to spray nitrogen with a pressure of 8-9 MPa onto the inner and outer surfaces of the stainless steel during the duration of each jet action.

[0014] As an improvement of the above scheme, within the duration of each injection action, nitrogen is sprayed to the stainless steel pipe in multiple pulse actions, and the duration of each pulse action is 1-2s, and the time interval between the adjacent pulse actions on both sides is 10-15s.

[0015] As an improvement of the above solution, the temperature of the nitrogen gas ejected from the jet nozzle is 10-20°C.

[0016] As an improvement of the above solution, a temperature adjustment mechanism and an air pressure adjustment mechanism are provided in the processing device.

[0017] As an improvement of the above solution, the abrasive particle size is 0.2-0.8 mm, and the particle size of the elastic abrasive in step S3 is one half to one third of the particle size of the elastic abrasive in step S1.

[0018] As an improvement of the above solution, the distance between the outer injection port and the outer side of the stainless steel tube and the distance between the inner injection port and the inner side of the stainless steel tube are both less than or equal to 50 mm.

[0019] As an improvement of the above scheme, in step S1, the elastic abrasive and nitrogen mixture leaves the outer injection port and the inner injection port at a speed of 60-70 m / s; in step S3, the elastic abrasive and nitrogen mixture leaves the outer injection port and the inner injection port at a speed of 80-100 m / s.

[0020] The implementation of the present invention has the following beneficial effects:

[0021] The corrosion-resistant treatment method for a stainless steel pipe of the present invention can improve the corrosion resistance and smoothness of the stainless steel pipe and reduce the impact on the appearance of the stainless steel pipe by step-by-step spraying of elastic abrasives for polishing and step-by-step nitriding of the cleaned stainless steel pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of a method for treating a stainless steel pipe against corrosion in an embodiment of the present invention;

[0023] Figure 2 is an internal structure diagram of a processing device in an embodiment of the present invention;

[0024] Figure 3 for Figure 2 Magnified view at A in the middle.

[0025] In the figure: 100, processing device; 200, injection mechanism; 210, external injection pipe; 211, external injection port; 220, internal injection pipe; 221, internal injection port; 300, rotating mechanism; 400, injection port. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0027] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0028] like Figure 1As shown, a corrosion-resistant treatment method for a stainless steel pipe in an embodiment of the present invention comprises the following steps:

[0029] S1, placing the cleaned stainless steel pipe in a processing device 100, the processing device 100 is in a nitrogen environment with a temperature of 30-50°C and a pressure of 100-110 kPa, mixing the elastic abrasive with nitrogen and spraying it toward the inner and outer surfaces of the stainless steel at a pressure of 2-4 MPa for 15-20 minutes.

[0030] In fact, before the stainless steel pipe enters the processing device 100, it is necessary to perform pre-treatment operations such as grinding and cleaning on the stainless steel pipe to pre-clean the stainless steel surface in order to remove surface oil stains, welding spatter and metal defects; when the stainless steel pipe enters the processing device 100, it is in a nitrogen environment with a temperature of 90-110°C and a pressure of 100-110kPa. This pressure is close to the horizontal atmospheric pressure, which prevents the inner and outer surfaces of the stainless steel pipe from contacting with oxygen and prevents the stainless steel pipe from continuing to oxidize when the surface oxide layer is removed.

[0031] It should be noted that the elastic abrasive can be made of one or more hard abrasive particles such as diamond powder, silicon carbide powder, titanium carbide powder, titanium nitride powder, carbon nitride powder and boron nitride powder filled in one or more soft substrates such as rubber, polyurethane, porous fiber, isoprene rubber and natural rubber. In fact, a group of soft substrates is filled with multiple hard abrasives. The hard abrasives of the outer ring protrude from the outer ring of the soft substrate. When the elastic abrasive contacts the surface of the stainless steel pipe, the soft substrate undergoes elastic deformation, so that the hard abrasives of the outer ring cut the stainless steel pipe. By continuously spraying the elastic abrasive, the oxide layer on the surface of the stainless steel pipe is removed and polished, and the oxide layer on the surface of the stainless steel pipe is prevented from re-forming in the nitrogen environment of the processing device 100 and when the elastic abrasive is mixed with nitrogen. At a temperature of 90-110° C., the stainless steel pipe becomes slightly softer than at room temperature, ensuring that the oxide layer can be removed.

[0032] S2, raising the temperature in the treatment device 100 to 500-530°C and the nitrogen pressure to 130-160kPa and maintaining for 13-16h. In fact, in step 2, the main purpose is to form a nitride layer on the surface of the stainless steel pipe under the conditions of a temperature of 500-530°C and a nitrogen pressure of 130-160kPa, and providing the nitride layer can significantly improve the corrosion resistance of the stainless steel pipe surface.

[0033] S3, the temperature in the processing device 100 is reduced to 90-110°C, the nitrogen pressure is reduced to 100-110kPa, and the elastic abrasive is mixed with nitrogen and sprayed toward the inner and outer surfaces of the stainless steel at a pressure of 5-7MPa for 4-6min. In fact, the temperature in step S3 is higher than the temperature in step S1. At this time, the mechanical properties of the stainless steel pipe, including yield strength and tensile strength, will decrease, while the elongation will increase. At this time, the polishing difficulty of the stainless steel pipe is higher, and the nitride layer on the surface of the stainless steel pipe is avoided. In this step, the mixture of elastic abrasive and nitrogen is sprayed again to trim the position that was not polished in step S1 and the deformation caused by heating and cooling the stainless steel pipe, ensuring that most of the nitride layer is retained while further polishing the stainless steel pipe.

[0034] S4, the temperature in the processing device 100 is raised to 550-580°C and the nitrogen pressure is 170-200 kPa and maintained for 22-26 hours. In fact, in this step, the nitriding layer is deepened again to ensure the corrosion resistance of the stainless steel pipe. After completing this step, the temperature and pressure in the processing device 100 are gradually reduced to the same as those outside, and then the stainless steel pipe is taken out.

[0035] At this point, after steps S1 to S4, the corrosion-resistant treatment method for stainless steel pipes of the present invention is completed. By step-by-step spraying of elastic abrasives for polishing and step-by-step nitriding of the cleaned stainless steel pipes, the corrosion resistance and smoothness of the stainless steel pipes can be improved, and the impact on the appearance of the stainless steel pipes can be reduced.

[0036] Specifically, in steps S1 and S3, the elastic abrasive and nitrogen mixture is preferably sprayed on the stainless steel pipe in multiple spraying actions, and each spraying action lasts for 40-50 seconds, and the interval time between the spraying actions on the adjacent two sides is 10-20 seconds. By spraying the elastic abrasive and nitrogen mixture on the stainless steel pipe in multiple spraying actions, leaving an interval time between the spraying actions on the adjacent two sides, the heat generated by the continuous polishing of the stainless steel pipe can be dissipated, so that the polishing operation is smoother.

[0037] More specifically, Figure 2 and Figure 3 As shown, the processing device 100 is preferably provided with a spray mechanism 200 and a rotating mechanism 300 for driving the spray mechanism 200 to rotate, the spray mechanism 200 includes two outer spray vertical pipes arranged at intervals and an inner spray vertical pipe located in the middle of the two outer spray pipes 210, the outer spray pipe 210 is provided with a plurality of outer spray ports 211 for spraying the outer surface of the stainless steel pipe at intervals above and below, the inner spray pipe 220 is provided with a plurality of inner spray ports 221 for spraying the inner surface of the stainless steel pipe at intervals on both back sides, and the elastic abrasive and nitrogen mixture is introduced into the outer spray pipe 210 and the inner spray pipe 220 through a pipeline to spray the inner and outer surfaces of the stainless steel.

[0038] In fact, the inner spray pipe 220 can spray at two positions on the inner surface of the stainless steel pipe in reverse, and similarly, the two outer spray pipes 210 can spray at two positions on the outer surface of the stainless steel pipe. The rotating mechanism 300 can be a motor, which can drive the spray mechanism 200 to rotate at a set speed to spray the inner and outer surfaces of the stainless steel pipe in full coverage, thereby reducing the polishing dead angle area of ​​the inner and outer surfaces of the stainless steel pipe.

[0039] Further, the processing device 100 is preferably provided with a plurality of jet ports 400, and the jet ports 400 are used to spray nitrogen with a pressure of 8-9MPa on the inner and outer surfaces of the stainless steel during the duration of each jet action. By additionally spraying nitrogen with a higher pressure, turbulence is generated in the movement of the elastic abrasive in the processing device 100, and the stainless steel pipe is contacted at more angles and positions, further reducing the polishing dead angle area of ​​the inner and outer surfaces of the stainless steel pipe. Preferably, during the duration of each jet action, nitrogen is sprayed on the stainless steel pipe in a plurality of pulse actions, and the duration of each pulse action is 1-2s, and the time interval between the adjacent two-side pulse actions is 10-15s, which can ensure the generation of turbulence, and has little effect on the injection of the mixture of elastic abrasive and nitrogen, ensuring the polishing effect of step S1 and step S3. It is worth mentioning that the temperature of the nitrogen sprayed from the jet port 400 is preferably 10-20°C, which is lower than the ambient temperature in the processing device 100 where the stainless steel pipe is located, and can better take away the heat generated by the stainless steel pipe due to polishing, and further reduce the polishing dead angle area of ​​the inner and outer surfaces of the stainless steel pipe to ensure the polishing effect.

[0040] It should be noted that the processing device 100 is preferably provided with a temperature adjustment mechanism and an air pressure adjustment mechanism (omitted in the drawings). In fact, the temperature adjustment mechanism may include a temperature sensor and a temperature control component (such as a combination of a heater and a refrigerator). When the temperature sensor detects that the temperature in the processing device 100 exceeds or is lower than the temperature set at this stage, the temperature control starts to work to cool down or heat up; similarly, the air pressure adjustment mechanism may include a barometer and a two-way pump. When the barometer detects that the air pressure in the processing device 100 exceeds or is lower than the pressure set at this stage, the two-way pump starts to work to pump nitrogen out of the processing device 100 or into the processing device 100.

[0041] Specifically, the abrasive particle size is preferably 0.2-0.8 mm, and the particle size of the elastic abrasive in step S3 is one-half to one-third of the particle size of the elastic abrasive in step S1. The elastic abrasive particle size in step S3 is finer, ensuring higher precision of the second step polishing and making it more difficult to remove the nitride layer on the surface of the stainless steel pipe.

[0042] Furthermore, the distance between the outer jet port 211 and the outside of the stainless steel pipe and the distance between the inner jet port 221 and the inside of the stainless steel pipe are preferably less than or equal to 50 mm, so as to ensure that the elastic abrasive can quickly contact the surface of the stainless steel pipe after leaving the inner jet port 221 or the outer jet port 211, thereby ensuring the polishing effect.

[0043] Specifically, in step S1, the elastic abrasive and nitrogen mixture leaves the outer injection port 211 and the inner injection port 221 at a speed of 60-70 m / s; in step S3, the elastic abrasive and nitrogen mixture leaves the outer injection port 211 and the inner injection port 221 at a speed of 80-100 m / s. Ensure that the soft base of the elastic abrasive is elastically deformed to expose the hard abrasive, and the hard abrasive is in contact with the surface of the stainless steel pipe to achieve polishing of the stainless steel pipe surface. Since the elastic abrasive in step S3 has a finer particle size and is more difficult to expose the hard abrasive, the injection speed of step three should be faster.

[0044] The above are only specific embodiments of the present invention, which show and describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. The above embodiments and descriptions only describe the principles of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for treating a stainless steel pipe against corrosion, characterized in that: The steps include: S1, placing the cleaned stainless steel pipe in a treatment device, which is in a nitrogen environment with a temperature of 30-50°C and a pressure of 100-110 kPa, mixing the elastic abrasive with nitrogen and spraying it toward the inner and outer surfaces of the stainless steel at a pressure of 2-4 MPa for 15-20 minutes; S2, raising the temperature in the treatment device to 500-530°C and the nitrogen pressure to 130-160 kPa and maintaining for 13-16 hours; S3, the temperature in the treatment device is reduced to 90-110°C, the nitrogen pressure is reduced to 100-110 kPa, the elastic abrasive is mixed with nitrogen and sprayed toward the inner and outer surfaces of the stainless steel at a pressure of 5-7 MPa for 4-6 minutes; S4, raising the temperature in the treatment device to 550-580°C and the nitrogen pressure to 170-200 kPa and maintaining it for 22-26 hours.

2. A method for treating a stainless steel pipe against corrosion as claimed in claim 1, characterized in that: In steps S1 and S3, the elastic abrasive and nitrogen mixture is sprayed on the stainless steel pipe in multiple spraying actions, and each spraying action lasts for 40-50 seconds, and the interval time between the spraying actions on the two adjacent sides is 10-20 seconds.

3. A method for treating a stainless steel pipe against corrosion as claimed in claim 2, characterized in that: The processing device is provided with a spraying mechanism and a rotating mechanism for driving the spraying mechanism to rotate. The spraying mechanism includes two outer spraying vertical pipes arranged at intervals and an inner spraying vertical pipe located in the middle of the two outer spraying pipes. The outer spraying pipes are provided with a plurality of outer spraying ports for spraying the outer surface of the stainless steel pipe at intervals above and below. The inner spraying pipes are provided with a plurality of inner spraying ports for spraying the inner surface of the stainless steel pipe at intervals on the two back-facing sides. The elastic abrasive and nitrogen mixture is introduced into the outer spraying pipes and the inner spraying pipes through pipelines to spray the inner and outer surfaces of the stainless steel.

4. A method for treating a stainless steel pipe against corrosion as claimed in claim 3, characterized in that: The processing device is also provided with a plurality of jet ports, which are used to spray nitrogen gas with a pressure of 8-9 MPa onto the inner and outer surfaces of the stainless steel during the duration of each jet action.

5. A method for treating a stainless steel pipe against corrosion as claimed in claim 4, characterized in that: During the duration of each injection action, nitrogen is injected into the stainless steel pipe in multiple pulse actions, and the duration of each pulse action is 1-2s, and the time interval between the adjacent pulse actions on both sides is 10-15s.

6. A method for treating a stainless steel pipe against corrosion as claimed in claim 4, characterized in that: The temperature of the nitrogen gas ejected from the jet nozzle is 10-20°C.

7. A method for treating a stainless steel pipe against corrosion as claimed in claim 6, characterized in that: The processing device is provided with a temperature adjustment mechanism and an air pressure adjustment mechanism.

8. A method for treating a stainless steel pipe against corrosion as claimed in claim 3, characterized in that: The abrasive particle size is 0.2-0.8 mm, and the particle size of the elastic abrasive in step S3 is one half to one third of the particle size of the elastic abrasive in step S1.

9. A method for treating a stainless steel pipe against corrosion as claimed in claim 8, characterized in that: The distance between the outer injection port and the outer side of the stainless steel pipe and the distance between the inner injection port and the inner side of the stainless steel pipe are both less than or equal to 50 mm.

10. A method for treating a stainless steel pipe against corrosion as claimed in claim 9, characterized in that: In step S1, the elastic abrasive and nitrogen mixture leaves the outer injection port and the inner injection port at a speed of 60-70 m / s; in step S3, the elastic abrasive and nitrogen mixture leaves the outer injection port and the inner injection port at a speed of 80-100 m / s.

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