Acid pickling method of stainless steel pipeline for gas turbine

Abstract

The invention provides a pickling method of a stainless steel pipeline for a gas turbine, which comprises the following steps: checking before pickling, clamping, chemical degreasing, cleaning a degreasing solution, washing and cooling, drying, isolating, removing welding flux, cleaning residual liquid for removing welding flux, pickling, supplementing pickling, recovering a pickling solution, cleaning pickling residues, cleaning the pickling solution, removing isolation, and cleaning residual liquid for removing isolation. And drying and storing. The method can effectively remove an oxide layer, soldering flux residues, oil stains and other impurities on the surface of the stainless steel pipeline, can avoid excessive corrosion to the surface of the pipeline, guarantees the quality and performance of the pipeline, prolongs the service life of the tank body, reduces the influence on the environment, is simple in operation, can improve the production efficiency, and reduces the production cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal surface treatment, and particularly relates to a pickling method for stainless steel pipes used in gas turbines. Background Art

[0002] In the operation of gas turbines, stainless steel pipes play a crucial role. They are responsible for transporting various media such as fuel, high-pressure air, and coolant. Therefore, the quality and performance of stainless steel pipes directly affect the reliability, efficiency, and safety of gas turbines.

[0003] During the manufacturing, transportation, and installation of stainless steel pipes, an oxide layer, flux residues, oil stains, and other impurities will inevitably form on their surfaces. These contaminants not only affect the appearance of the pipes but also reduce the corrosion resistance of the pipes, thereby shortening the service life of the pipes. To remove these contaminants and improve the surface quality and corrosion resistance of the pipes, pickling is a commonly used treatment method.

[0004] However, problems existing in the pickling methods in the prior art may lead to a series of adverse consequences during the operation of gas turbines. For example, incomplete pickling will cause impurities such as the oxide layer and flux residues on the surface of the stainless steel pipes not to be completely removed. These impurities may enter the internal components of the gas turbine, such as the compressor, combustion chamber, turbine, etc., along with the flow of the medium, thereby affecting the combustion efficiency and power output of the gas turbine. Excessive corrosion may cause the pipe wall thickness to decrease and the strength to reduce. During the operation of the gas turbine, the pipes need to withstand a high-temperature and high-pressure working environment. The reduction of the pipe wall thickness and strength will increase the risk of pipe rupture, thereby triggering safety accidents. The discharge of pickling solution pollutes the environment, which not only does not meet the environmental protection requirements but also may increase the operating costs of enterprises. Summary of the Invention

[0005] The purpose of the present invention is to provide a pickling method for stainless steel pipes used in gas turbines, which can effectively remove the oxide layer, flux residues, oil stains, and other impurities on the pipe surface, improve the surface quality and corrosion resistance of the pipes, while ensuring the quality and performance of the pipes and reducing the impact on the environment.

[0006] A pickling method for stainless steel pipes used in gas turbines includes the following steps:

[0007] S1, inspection before pickling: Inspect the surface quality of the stainless steel pipes;

[0008] S2, clamping: Bundle 10 - 15 stainless steel pipes into a group with steel wires and place them on a steel hook;

[0009] S3, Chemical degreasing: Conduct chemical degreasing treatment in a degreasing tank with a solution composition of 60 - 70 grams per liter of trisodium phosphate and 3 - 5 grams per liter of OP emulsifier. The degreasing temperature is 70 - 80 °C and the time is 20 - 40 minutes;

[0010] S4, Clean the degreasing solution: Immerse the stainless - steel pipe in a flowing hot - water tank at 50 - 70 °C and clean it 3 - 5 times, with each cleaning time being 2 - 3 minutes;

[0011] S5, Rinse and cool down: Immerse the stainless - steel pipe in a flowing cold - water tank and clean it 3 times, with each cleaning time being 1 - 2 minutes;

[0012] S6, Drying: Completely blow - dry the moisture on the surface of the stainless - steel pipe with clean compressed air;

[0013] S7, Isolation: Surfaces that do not require pickling should be coated with an isolation glue composed of 60% carnauba wax, 25% paraffin wax, and 15% turpentine by composition and mass fraction for isolation treatment. The coating thickness of the isolation glue is 2 - 3 mm;

[0014] S8, Remove the flux: Remove the flux in a flux - removing tank with a solution composition of 100 - 120 grams per cubic decimeter of potassium sulfate. The treatment temperature is 18 - 23 °C and the time is 20 - 30 minutes;

[0015] S9, Clean the residual flux solution: Immerse the stainless - steel pipe in a flowing cold - water tank and clean it 3 times, with each cleaning time being 0.5 - 1 minute;

[0016] S10, Pickling: Conduct pickling in a pickling tank with a solution composition of 30 - 40 grams per cubic decimeter of hydrofluoric acid with a specific gravity of 1.13 - 1.15 grams per cubic centimeter and 140 - 170 grams per cubic decimeter of nitric acid with a specific gravity of 1.34 - 1.44 grams per cubic centimeter. The treatment temperature is 18 - 25 °C and the time is 20 - 60 minutes;

[0017] S11, Supplementary pickling: Conduct supplementary pickling in a supplementary pickling tank with a solution composition of 1 volume of nitric acid with a specific gravity of 1.34 - 1.44 grams per cubic centimeter and 3 volumes of hydrochloric acid with a specific gravity of 1.14 - 1.19 grams per cubic centimeter. The treatment temperature is 15 - 30 °C and the time is 5 - 10 minutes;

[0018] S12, Recycle the pickling solution: Immerse the stainless - steel pipe in still cold water 3 times and collect the pickling solution into the pickling - solution collection tank;

[0019] S13, Remove the pickling residues: Use a pneumatic water gun to remove the pickling residues on the surface of the stainless - steel pipe;

[0020] S14, Clean the pickling solution: Immerse the stainless - steel pipe in a flowing cold - water tank and clean it 3 times, with each cleaning time being 0.5 - 1 minute;

[0021] S15, Demasking: Perform demasking treatment in a demasking tank with a solution composition of 10 - 20 grams per liter of sodium carbonate. The demasking temperature is 70 - 90 degrees Celsius until the masking glue is completely removed.

[0022] S16, Clean the residual liquid after demasking: Immerse the stainless - steel pipe in a flowing hot - water tank at 50 - 70 degrees Celsius and wash it 3 - 5 times, with each washing time being 2 - 3 minutes.

[0023] S17, Dry and store.

[0024] Furthermore, the degreasing tank in S3 is made of carbon steel and is equipped with an inner lining of polyvinyl chloride board, a side discharge port, a serpentine steam pipe, and a drain tank.

[0025] Furthermore, the hot - water tank in S4 is made of stainless steel and is equipped with a side discharge port and a serpentine steam pipe.

[0026] Furthermore, the cold - water tank in S5 is made of carbon steel and has an inner lining of polyvinyl chloride board.

[0027] Furthermore, the masking tank and the demasking tank in S7 and S15 are made of carbon steel and have a side discharge port and a serpentine steam pipe.

[0028] Furthermore, the pickling tank and the supplementary pickling tank in S10 and S11 are made of titanium alloy and are equipped with a side discharge port.

[0029] Furthermore, the pickling - solution collection tank in S12 is made of carbon steel and has an inner lining of polyvinyl chloride board and a side discharge port.

[0030] Furthermore, the air pressure used for the pneumatic water gun in S13 is 0.3 - 0.4 MPa, and the water pressure is not less than 4 MPa.

[0031] Furthermore, the drying and storing in S17 specifically mean completely drying the moisture on the surface of the stainless - steel pipe with clean compressed air, and removing the stainless - steel pipe from the steel hook and storing it in a dry, clean, and well - ventilated environment.

[0032] The beneficial effects of the present invention are as follows:

[0033] 1. The pickling method of the present invention can effectively remove the oxide layer, flux residue, oil stain, and other impurities on the surface of the stainless - steel pipe, improving the surface quality and corrosion resistance of the pipe.

[0034] 2. Reasonably controlling various parameters in the pickling process, such as temperature, time, solution composition, etc., can avoid over - corrosion of the pipe surface and ensure the quality and performance of the pipe.

[0035] 3. The material and structure of the treatment tank have been optimized, which can improve the corrosion resistance of the tank body, extend the service life of the tank body, reduce the discharge of waste liquid, and reduce the impact on the environment.

[0036] 4. The pickling method of the present invention is simple to operate and easy to realize automated production, which can improve production efficiency and reduce production costs. Brief Description of the Drawings

[0037] Figure 1 is a flow chart of the present invention. Detailed Description of the Invention

[0038] The present invention will be further described below with reference to the drawings.

[0039] As Figure 1 shown, a pickling method for a stainless steel pipe used in a gas turbine includes the following steps:

[0040] S1. Inspection before pickling: Inspect the surface quality of the stainless steel pipe;

[0041] S2. Clamping: Bundle 10 - 15 stainless steel pipes into a group with steel wires and place them on a steel hook;

[0042] S3. Chemical degreasing: Conduct chemical degreasing treatment in a degreasing tank with a solution composition of 60 - 70 grams per liter of trisodium phosphate and 3 - 5 grams per liter of OP emulsifier, with a degreasing temperature of 70 - 80 °C and a time of 20 - 40 minutes;

[0043] Among them, the degreasing tank is made of carbon steel and is provided with an inner lining of polyvinyl chloride board, a side discharge port, a serpentine steam pipe, and a drain tank;

[0044] S4. Cleaning the degreasing solution: Immerse the stainless steel pipe in a flowing hot water tank at 50 - 70 °C and wash it 3 - 5 times, with each washing time of 2 - 3 minutes;

[0045] Among them, the hot water tank is made of stainless steel and is provided with a side discharge port and a serpentine steam pipe;

[0046] S5. Rinsing and cooling: Immerse the stainless steel pipe in a flowing cold water tank and wash it 3 times, with each washing time of 1 - 2 minutes; Further rinse off the impurities not completely removed in step S4; On the other hand, the surface of the pipe can be quickly cooled by cold water washing to prepare for subsequent processes with temperature requirements;

[0047] Among them, the cold water tank is made of carbon steel and has an inner lining of polyvinyl chloride board;

[0048] S6. Drying: Completely dry the moisture on the surface of the stainless steel pipe with clean compressed air;

[0049] S7, Isolation: Surfaces that do not require pickling should be isolated by applying an isolation gel composed of 60% carnauba wax, 25% paraffin wax, and 15% turpentine by composition and mass fraction. The thickness of the applied isolation gel is 2 - 3 mm;

[0050] Among them, the isolation tank is made of carbon steel and has a side discharge port and a serpentine steam pipe;

[0051] S8, Flux Removal: Remove the flux in a flux removal tank with a solution composition of 100 - 120 g / dm³ of potassium sulfate. The treatment temperature is 18 - 23 °C and the time is 20 - 30 minutes;

[0052] Among them, the flux removal tank is made of stainless steel;

[0053] S9, Cleaning Residual Flux Solution: Immerse the stainless - steel pipe in a flowing cold - water tank and wash it 3 times, with each washing time being 0.5 - 1 minute; The flowing cold - water washing in this step is to remove the residual flux solution on the pipe surface, prevent the flux solution from contaminating the pickling solution, and affect the pickling effect;

[0054] S10, Pickling: Pickle in a pickling tank with a solution composition of 30 - 40 g / dm³ of hydrofluoric acid with a specific gravity of 1.13 - 1.15 g / cm³ and 140 - 170 g / dm³ of nitric acid with a specific gravity of 1.34 - 1.44 g / cm³. The treatment temperature is 18 - 25 °C and the time is 20 - 60 minutes;

[0055] Among them, the pickling tank is made of titanium alloy and has a side discharge port;

[0056] S11, Supplementary Pickling: Conduct supplementary pickling in a supplementary pickling tank with a solution composition of 1 volume of nitric acid with a specific gravity of 1.34 - 1.44 g / cm³ and 3 volumes of hydrochloric acid with a specific gravity of 1.14 - 1.19 g / cm³. The treatment temperature is 15 - 30 °C and the time is 5 - 10 minutes;

[0057] Among them, the supplementary pickling tank is made of titanium alloy and has a side discharge port;

[0058] S12, Recycling Pickling Solution: Immerse the stainless - steel pipe in non - flowing cold water 3 times and collect the pickling solution into the pickling solution collection tank;

[0059] Among them, the pickling solution collection tank is made of carbon steel and has a PVC lining board and a side discharge port;

[0060] S13, Removing Pickling Residue: Use a pneumatic water gun to remove the pickling residue on the surface of the stainless - steel pipe;

[0061] Among them, the air pressure used by the pneumatic water gun is 0.3 - 0.4 MPa, and the water pressure is not less than 4 MPa;

[0062] S14, Cleaning the pickling solution: Immerse the stainless-steel pipe in a flowing cold-water tank and clean it 3 times, with each cleaning time being 0.5 - 1 minute; The flowing cold-water cleaning in this step is to rinse off the residual pickling solution on the pipe surface, prevent the pickling solution from continuously corroding the pipe surface, and at the same time remove the impurities that may be generated during the pickling process, preparing for the subsequent step S15;

[0063] S15, Removing the isolation: Conduct the removal of isolation treatment in an isolation-removing tank with a sodium carbonate solution concentration of 10 - 20 grams per liter, and the isolation-removing temperature is 70 - 90 degrees Celsius until the isolation glue is completely removed;

[0064] Among them, the isolation-removing tank is made of carbon steel and has a side discharge port and a serpentine steam pipe;

[0065] S16, Cleaning the residual liquid after removing isolation: Immerse the stainless-steel pipe in a flowing hot-water tank at 50 - 70 degrees Celsius and clean it 3 - 5 times, with each cleaning time being 2 - 3 minutes; The flowing hot-water cleaning in this step can better remove the residual substances from the pipe surface by utilizing the better solubility and fluidity of hot water, making the pipe surface cleaner and preparing for subsequent processes such as drying and storage;

[0066] S17, Drying and storage;

[0067] Among them, drying and storage specifically mean using clean compressed air to completely blow dry the moisture on the surface of the stainless-steel pipe, and removing the stainless-steel pipe from the steel hook and storing it in a dry, clean, and well-ventilated environment.

[0068] Targeted treatment tank design: According to the requirements of different steps, the material and structure of each treatment tank have been optimized. For example, the degreasing tank is made of carbon steel and lined with polyvinyl chloride plates, and the pickling tank is made of titanium alloy, etc. Such a design can improve the corrosion resistance of the tank body, extend the service life of the tank body, and at the same time reduce the waste liquid discharge and the impact on the environment.

[0069] Environmentally friendly pickling solution recovery: A step for recovering the pickling solution is set. Immerse the stainless-steel pipe three times in non-flowing cold water, and collect the pickling solution into the pickling solution collection tank, reducing the discharge of the pickling solution, which has a positive significance for environmental protection.

[0070] Efficient removal of pickling residues: Use a pneumatic water gun to remove the pickling residues on the surface of the stainless-steel pipe, and specify the air pressure and water pressure for using the pneumatic water gun to ensure that the residues can be effectively removed, improving the cleanliness of the pipe surface.

[0071] Ensuring the pipe quality and performance: The design of the entire pickling method aims to improve the surface quality and corrosion resistance of the pipe, while ensuring that the quality and performance of the pipe are not damaged, providing a strong guarantee for the reliable operation of the gas turbine.

[0072] The outstanding advantages and improvements of the present invention compared with the prior art are as follows:

[0073] Improve pickling effect: By precisely controlling various parameters in the pickling process, such as temperature, time, solution composition, etc., the present invention can more effectively remove the oxide layer, flux residue, oil stain and other impurities on the surface of the stainless steel pipe, improving the surface quality and corrosion resistance of the pipe. The supplementary pickling step is adopted to further remove the impurities on the pipe surface, enhancing the pickling effect and making the pipe cleaner.

[0074] Protect the pipe quality: The reasonable step and parameter settings avoid excessive corrosion of the pipe surface, ensure the wall thickness and strength of the pipe, and extend the service life of the pipe. Applying isolation glue to the surfaces that do not require pickling effectively protects these parts from being corroded by the pickling solution, further ensuring the quality of the pipe.

[0075] Optimize the design of the treatment tank: According to the requirements of different treatment steps, select suitable treatment tank materials, such as carbon steel, stainless steel, titanium alloy, etc., and equip with corresponding linings and structures, improving the corrosion resistance of the tank body and reducing the damage and replacement frequency of the tank body. The structural design of the treatment tank, such as side discharge ports, serpentine steam pipes, etc., facilitates the discharge of waste liquid and the heating of the solution, improving the operation convenience and efficiency of the pickling process.

[0076] Reduce environmental pollution: The step of recycling the pickling solution reduces the discharge of the pickling solution and reduces the environmental pollution. The reasonable design and material selection of each treatment tank also reduce the leakage of waste liquid and the potential harm to the environment.

[0077] Simple operation: The pickling method of the present invention has a clear operation process, is easy to master and implement, facilitates automated production, and improves production efficiency.

[0078] Strong adaptability: The present invention is applicable to the pickling treatment of stainless steel pipes for gas turbines and can meet the high requirements for the quality and performance of pipes in this field.

[0079] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for pickling stainless steel pipes for gas turbines, characterized in that: The following steps are involved: S1, inspection before pickling: check the surface quality of stainless steel pipes; S2, clamping: 10 to 15 stainless steel pipes are bundled into a group with steel wire and placed on a steel hook; S3, chemical degreasing: chemical degreasing treatment is carried out in a degreasing tank with a solution composition of 60-70 g / L trisodium phosphate and 3-5 g / L OP emulsifier, the degreasing temperature is 70-80 degrees Celsius, and the time is 20-40 minutes; S4, cleaning degreasing solution: immerse the stainless steel pipe in a flowing hot water tank at 50 to 70 degrees Celsius for 3 to 5 times, each cleaning time is 2 to 3 minutes; S5, flushing and cooling: immerse the stainless steel pipe in a flowing cold water tank for 3 times, each cleaning time is 1 to 2 minutes; S6, Drying: Use clean compressed air to completely dry the moisture on the surface of the stainless steel pipe; S7， Isolation: Surfaces that do not require pickling should be coated with an isolation glue containing 60% insect wax, 25% paraffin and 15% turpentine by mass. The thickness of the isolation glue should be 2 to 3 mm. S8, removing flux: removing flux in a flux removal tank containing 100 to 120 g / cm3 potassium sulfate at a temperature of 18 to 23 degrees Celsius for 20 to 30 minutes; S9, cleaning the residual liquid of flux removal: immerse the stainless steel pipe in a flowing cold water tank for cleaning 3 times, each cleaning time is 0.5 to 1 minute; S10, pickling: pickling in a pickling tank having a solution composition of 30 to 40 g / cm3 of hydrofluoric acid with a specific gravity of 1.13 to 1.15 g / cm3 and 140 to 170 g / cm3 of nitric acid with a specific gravity of 1.34 to 1.44 g / cm3, at a treatment temperature of 18 to 25 degrees Celsius for 20 to 60 minutes; S11, supplementary pickling: supplementary pickling in a supplementary pickling tank containing 1 volume of nitric acid with a specific gravity of 1.34 to 1.44 g / cm3 and 3 volumes of hydrochloric acid with a specific gravity of 1.14 to 1.19 g / cm3, at a treatment temperature of 15 to 30 degrees Celsius for 5 to 10 minutes; S12, recovering the pickling solution: immersing the stainless steel pipe in still cold water for 3 times, and collecting the pickling solution into a pickling solution collecting tank; S13, removing pickling residue: using a pneumatic water gun to remove pickling residue on the surface of the stainless steel pipe; S14, cleaning the pickling solution: immerse the stainless steel pipe in a flowing cold water tank for cleaning 3 times, each cleaning time is 0.5 to 1 minute; S15, de-isolation: de-isolation treatment is performed in a de-isolation tank with a solution composition of 10 to 20 grams per liter of sodium carbonate at a de-isolation temperature of 70 to 90 degrees Celsius until the isolation glue is completely removed; S16, cleaning and removing the residual isolation liquid: immersing the stainless steel pipe in a flowing hot water tank at 50 to 70 degrees Celsius for 3 to 5 times, each cleaning time is 2 to 3 minutes; S17, Drying and storage.

2. A method for pickling a stainless steel pipe for a gas turbine according to claim 1, characterized in that: The degreasing tank in S3 is made of carbon steel and is provided with a polyvinyl chloride plate lining, a side discharge port, a serpentine steam pipe and a discharge tank.

3. The pickling method for a stainless steel pipe for a gas turbine according to claim 1, characterized in that: The hot water tank in S4 is made of stainless steel and is provided with a side discharge port and a serpentine steam pipe.

4. The pickling method for a stainless steel pipe for a gas turbine according to claim 1, characterized in that: The S5 cold water tank is made of carbon steel and lined with polyvinyl chloride plates.

5. The pickling method for a stainless steel pipe for a gas turbine according to claim 1, characterized in that: The isolation tank and de-isolation tank in S7 and S15 are made of carbon steel and have side discharge ports and serpentine steam pipes.

6. The pickling method for a stainless steel pipe for a gas turbine according to claim 1, characterized in that: The pickling tank and supplementary pickling tank in S10 and S11 are made of titanium alloy and are provided with side discharge ports.

7. The pickling method for a stainless steel pipe for a gas turbine according to claim 1, characterized in that: The pickling liquid collecting tank in S12 is made of carbon steel and is lined with polyvinyl chloride plates and has a side discharge port.

8. The pickling method for a stainless steel pipe for a gas turbine according to claim 1, characterized in that: The air pressure used by the pneumatic water gun in S13 is 0.3-0.4 MPa, and the water pressure is not less than 4 MPa.

9. The pickling method for a stainless steel pipe for a gas turbine according to claim 1, characterized in that: The drying and storage in S17 specifically involves completely drying the moisture on the surface of the stainless steel pipe with clean compressed air, and removing the stainless steel pipe from the steel hook and storing it in a dry, clean, well-ventilated environment.

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