A method for preparing a corrosion-resistant heat exchange tube

Abstract

The present invention discloses a method for preparing a corrosion-resistant heat exchange tube, and belongs to the technical field of heat exchange tubes. The present invention adopts a vacuum induction furnace and an electroslag remelting double smelting process to prepare high-quality heat exchange tube steel; the present invention adds Cu and Ni elements to improve the corrosion resistance of the heat exchange tube, because the generated corrosion film is amorphous and a Cu enrichment layer is formed under the corrosion film; the benzoimidazole, ethyl acetate and neodymium complex generated by the fire extraction liquid of the present invention have good corrosion resistance, which can improve the corrosion resistance of the heat exchange tube; the reaction combines benzoimidazole, ethyl acetate and neodymium complex together through a mercapto-epoxy reaction to generate a neodymium-containing quenching agent with excellent corrosion resistance and nuclear shielding effect, thereby improving the performance of the corrosion-resistant heat exchange tube, and can further improve the corrosion resistance of the heat exchange tube.

Description

Technical Field

[0001] The invention relates to the technical field of heat exchange tubes, in particular to a method for preparing a corrosion-resistant heat exchange tube. Background Art

[0002] Heat exchangers are common equipment used in chemical, petroleum, power, food, and many other industrial sectors, playing a vital role in production. In chemical production, heat exchangers can serve as heaters, coolers, condensers, evaporators, and reboilers, making them particularly versatile. The corrosion resistance of heat exchange tubes determines the service life of the entire heat exchange equipment.

[0003] Chinese patent CN108823467A discloses a method for processing corrosion-resistant titanium tubes. The method comprises the following steps: (1) alloy smelting: placing the raw materials in a smelting furnace for smelting; (2) billet preparation: preparing the titanium tube billet by forging and then extrusion; (3) rolling: using a cold press to perform multiple rolling of the titanium tube billet, degreasing and annealing after each rolling; (4) surface treatment: soaking the rolled titanium tube billet in an anti-corrosion coating for 10-15 minutes and drying it to obtain the corrosion-resistant titanium tube. The alloy composition makes the titanium tube resistant to corrosion, and a layer of anti-corrosion coating is applied to the surface of the titanium tube to further prevent corrosion. The resulting titanium tube is suitable for use in heat exchangers.

[0004] Chinese patent CN107655358A: relates to the field of heat exchangers, and discloses a corrosion-resistant heat exchange tube and its preparation method. The heat exchange tube consists of a working tube and a porous coating, and its preparation method includes the following steps: 1) Cleaning: clean the working tube with pure water; 2) Degreasing: spray or soak the working tube with a degreasing agent to clean and remove oil; 3) Cleaning: clean the residual degreasing agent on the working tube with pure water; 4) Powder spraying: after the working tube is dried, use porous corrosion-resistant powder coating to spray the metal surface with powder coating, solidify and cool. Applying porous coating material to the inside of the heat exchange tube not only increases the heat exchange area and saves costs, but also increases the diameter of the heat exchange tube under the condition of the same heat transfer area, making it easier to clean and less prone to scaling and clogging. In addition, the porous coating material can also prevent boiling. Its preparation method and process flow are simple, low cost, and very suitable for industrial production.

[0005] Chinese Patent CN105711051A: This relates to the field of industrial heat exchange, providing a new composite plastic to replace the original metal heat exchange material, which can prevent corrosion and significantly extend the service life of the heat exchanger. It is characterized by the use of high-temperature and corrosion-resistant fluoroplastic as the outer layer of the pipe, with a thickness of ≤0.2mm. A polyamide resin material with 5% graphene added, which has good thermal conductivity and mechanical strength, is used as the inner layer of the pipe, with a thickness of ≤0.3mm. On multi-layer co-extrusion processing equipment, the barrel operating temperature is 205-260°C, and the die operating temperature is 220-275°C. Under melt extrusion process conditions, over 100 meters of composite pipe can be continuously produced.

[0006] The heat exchange tubes prepared by the above patents and prior art have poor corrosion resistance, which leads to leakage of the heat exchange tubes, thereby shortening the operation cycle of the heat exchanger and increasing maintenance costs. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art and provide a method for preparing a corrosion-resistant heat exchange tube, the operating steps of which are as follows:

[0008] S1: Smelting. After the ingot is taken out of the furnace, the temperature of the heating equipment is lowered to 700-800℃ and kept warm for 10-20 minutes;

[0009] S2: After quenching the ingot in a quenching agent containing neodymium at 120-150°C, the ingot is taken out and placed in air to cool to room temperature;

[0010] S3: The ingot cooled in step S2 is tempered at 400-420°C for 100-150 minutes;

[0011] S4: hot extrusion, cold rolling, heat treatment and annealing;

[0012] S5: Then it is sent to the tapered roller piercing machine. After piercing, it is extruded, rolled, and sized to form a steel pipe.

[0013] As a further supplement to the above technical solution, the smelting adopts vacuum induction melting / electroslag remelting.

[0014] As a further supplement to the above technical solution, the furnace is washed twice with pure iron before smelting.

[0015] As a further supplement to the above technical solution, the charge of the vacuum induction furnace is: 0.02-0.05% C, 0.08-0.2% Si, 0.01-0.04% Mn, 0.02-0.05% P, 0.001-0.002% S, 12-14% Cr, 0.3-0.6% Cu, 55-60% Ni, 3-5% Mo, 0.16-0.2% Al, 0.1-0.3% Co, 0.14-0.23% Ti, 3.2-4.2% Nb, and the rest is Fe.

[0016] As a further supplement to the above technical solution, the vacuum degree of the vacuum induction furnace is 0.8-1 Pa, and the melting power is 1200-1600 kW.

[0017] As a further supplement to the above technical solution, the melting rate of the electroslag remelting is 400-500 kg / h.

[0018] As a further supplement to the above technical solution, the slag forming period current of the electroslag remelting is 4-8KA, the voltage is 60-90V, and the time is 20-40min; the remelting period current is 10-16KA, the voltage is 80-100V, and the time is 500-600min; the feeding period current is 8-10KA, the voltage is 60-80V, and the time is 50-70min.

[0019] As a further supplement to the above technical solution, the heat treatment temperature is 950-1050° C. and the time is 15-30 minutes.

[0020] As a further supplement to the above technical solution, the preparation method of the neodymium-containing quenching agent is as follows:

[0021] M1: Add 1.6-3.2 parts of neodymium sulfate, 1.3-2.6 parts of epoxysuccinic acid, and 100-150 parts of ethanol to a stirred tank, stirring at 40-50°C for 30-50 minutes;

[0022] M2: Add 0.02-0.3 parts of mercaptobenzoimidazole and 1-4 parts of sodium ethoxide to a stirred kettle, stir at 60-80°C for 30-100 minutes; then add 17-34 parts of thioglycolic acid ethanol; stir at 60-70°C for 100-150 minutes; remove the ethanol by vacuum distillation, then add 100-150 parts of polyvinyl alcohol and 1000-1500 parts of water, stir at 40-50°C for 30-50 minutes to obtain a neodymium-containing quenching agent.

[0023] Compared with the prior art, the method for preparing a corrosion-resistant heat exchange tube of the present invention has the following significant effects:

[0024] 1. The present invention adopts a vacuum induction furnace and electroslag remelting double smelting process to produce high-quality heat exchange tube steel;

[0025] 2. The present invention adds Cu and Ni elements to improve the corrosion resistance of the heat exchange tube. This is because the generated corrosion film is amorphous and a Cu-rich layer is formed under the corrosion film.

[0026] 3. The benzoimidazole, ethyl acetate and neodymium complex generated by the fire extraction liquid of the present invention has good corrosion resistance and can improve the corrosion resistance of the heat exchange tube; the reaction combines benzoimidazole, ethyl acetate and neodymium complex together through a thiol-epoxy reaction to generate a neodymium-containing quenching agent with excellent corrosion resistance and nuclear shielding effect, thereby improving the performance of the corrosion-resistant heat exchange tube and further improving the corrosion resistance of the heat exchange tube. DETAILED DESCRIPTION

[0027] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with specific embodiments.

[0028] The corrosion rate was tested using ASTM A262 standard method C.

[0029] Example 1

[0030] A method for preparing a corrosion-resistant heat exchange tube, the operating steps of which are:

[0031] S1: Smelting. After the ingot is taken out of the furnace, the temperature of the heating equipment is lowered to 700℃ and kept warm for 10 minutes;

[0032] S2: After quenching the ingot in a quenching agent containing neodymium at 120°C, the ingot is taken out and placed in air to cool to room temperature;

[0033] S3: The ingot cooled in step S2 is tempered at 400°C for 100 minutes;

[0034] S4: hot extrusion, cold rolling, heat treatment and annealing;

[0035] S5: Then it is sent to the tapered roller piercing machine. After piercing, it is extruded, rolled, and sized to form a steel pipe.

[0036] The smelting adopts vacuum induction melting / electroslag remelting.

[0037] The furnace is washed twice with pure iron before smelting.

[0038] The charge of the vacuum induction furnace is: 0.02% C, 0.08% Si, 0.01% Mn, 0.02% P, 0.001% S, 12% Cr, 0.3% Cu, 55% Ni, 3% Mo, 0.16% Al, 0.1% Co, 0.14% Ti, 3.2% Nb, and the rest is Fe.

[0039] The vacuum degree of the vacuum induction furnace is 0.8 Pa, and the melting power is 1200 kW.

[0040] The melting rate of the electroslag remelting is 400 kg / h.

[0041] The slag forming period of the electroslag remelting is performed with a current of 4KA, a voltage of 60V, and a time of 20min; a remelting period with a current of 10KA, a voltage of 80V, and a time of 500min; and a feeding period with a current of 8KA, a voltage of 60V, and a time of 50min.

[0042] The heat treatment temperature is 950° C. and the time is 15 minutes.

[0043] The preparation method of the neodymium-containing quenching agent is as follows:

[0044] M1: Add 1.6 kg of neodymium sulfate, 1.3 kg of epoxysuccinic acid, and 100 kg of ethanol into a stirred tank and stir at 40°C for 30 minutes;

[0045] M2: Add 0.02 kg of mercaptobenzoimidazole and 1 kg of sodium ethoxide to the stirred kettle and stir at 60°C for 30 minutes; then add 17 kg of thioglycolic acid ethanol; stir at 60°C for 100 minutes; remove the ethanol by vacuum distillation, then add 100 kg of polyvinyl alcohol and 1000 kg of water; stir at 40°C for 30 minutes to obtain the neodymium-containing quenching agent.

[0046] Example 2

[0047] A method for preparing a corrosion-resistant heat exchange tube, the operating steps of which are:

[0048] S1: Smelting. After the ingot is taken out of the furnace, the temperature of the heating equipment is lowered to 740°C and kept warm for 15 minutes;

[0049] S2: After quenching the ingot in a quenching agent containing neodymium at 130°C, the ingot is taken out and placed in air to cool to room temperature;

[0050] S3: The ingot cooled in step S2 is tempered at 405°C for 110 minutes;

[0051] S4: hot extrusion, cold rolling, heat treatment and annealing;

[0052] S5: Then it is sent to the tapered roller piercing machine. After piercing, it is extruded, rolled, and sized to form a steel pipe.

[0053] The smelting adopts vacuum induction melting / electroslag remelting.

[0054] The furnace is washed twice with pure iron before smelting.

[0055] The charge of the vacuum induction furnace is: 0.03% C, 0.1% Si, 0.02% Mn, 0.03% P, 0.001% S, 13% Cr, 0.4% Cu, 56% Ni, 4% Mo, 0.17% Al, 0.2% Co, 0.18% Ti, 3.6% Nb, and the rest is Fe.

[0056] The vacuum degree of the vacuum induction furnace is 0.9 Pa, and the melting power is 1300 kW.

[0057] The melting rate of the electroslag remelting is 430 kg / h.

[0058] The slag forming period of the electroslag remelting is performed with a current of 5KA, a voltage of 70V, and a time of 25min; the remelting period is performed with a current of 12KA, a voltage of 85V, and a time of 540min; and the feeding period is performed with a current of 9KA, a voltage of 65V, and a time of 55min.

[0059] The heat treatment temperature is 980° C. and the time is 20 minutes.

[0060] The preparation method of the neodymium-containing quenching agent is as follows:

[0061] M1: Add 2.4 kg of neodymium sulfate, 1.8 kg of epoxysuccinic acid, and 110 kg of ethanol into a stirred tank and stir at 45 °C for 35 min;

[0062] M2: Add 0.1 kg of mercaptobenzoimidazole and 2 kg of sodium ethoxide to the stirred kettle and stir at 65°C for 50 minutes; then add 22 kg of thioglycolic acid ethanol; stir at 65°C for 110 minutes; remove the ethanol by vacuum distillation, then add 110 kg of polyvinyl alcohol and 1100 kg of water; stir at 45°C for 35 minutes to obtain a neodymium-containing quenching agent.

[0063] Example 3

[0064] A method for preparing a corrosion-resistant heat exchange tube, the operating steps of which are:

[0065] S1: Smelting. After the ingot is taken out of the furnace, the temperature of the heating equipment is lowered to 780℃ and kept warm for 15 minutes.

[0066] S2: After quenching the ingot in a quenching agent containing neodymium at 140°C, the ingot is taken out and placed in air to cool to room temperature;

[0067] S3: The ingot cooled in step S2 is tempered at 415°C for 140 minutes;

[0068] S4: hot extrusion, cold rolling, heat treatment and annealing;

[0069] S5: Then it is sent to the tapered roller piercing machine. After piercing, it is extruded, rolled, and sized to form a steel pipe.

[0070] The smelting adopts vacuum induction melting / electroslag remelting.

[0071] The furnace is washed twice with pure iron before smelting.

[0072] The charge of the vacuum induction furnace is: 0.04% C, 0.16% Si, 0.03% Mn, 0.04% P, 0.002% S, 13% Cr, 0.5% Cu, 58Ni, 4% Mo, 0.18% Al, 0.2% Co, 0.21% Ti, 3.9% Nb, and the rest is Fe.

[0073] The vacuum degree of the vacuum induction furnace is 0.9 Pa, and the melting power is 1500 kW.

[0074] The melting rate of the electroslag remelting is 480 kg / h.

[0075] The slag forming period of the electroslag remelting is characterized by a current of 7KA, a voltage of 80V, and a time of 35min; a current of 15KA, a voltage of 95V, and a time of 580min; and a current of 9KA, a voltage of 75V, and a time of 65min.

[0076] The heat treatment temperature is 1030° C. and the time is 25 minutes.

[0077] The preparation method of the neodymium-containing quenching agent is as follows:

[0078] M1: Add 2.8 kg of neodymium sulfate, 2.4 kg of epoxysuccinic acid, and 140 kg of ethanol into a stirred tank and stir at 45 °C for 45 min.

[0079] M2: Add 0.2 kg of mercaptobenzoimidazole and 3 kg of sodium ethoxide to the stirred kettle and stir at 75°C for 80 minutes; then add 32 kg of thioglycolic acid ethanol; stir at 65°C for 140 minutes; remove the ethanol by vacuum distillation, then add 140 kg of polyvinyl alcohol and 1400 kg of water; stir at 45°C for 45 minutes to obtain the neodymium-containing quenching agent.

[0080] Example 4

[0081] A method for preparing a corrosion-resistant heat exchange tube, the operating steps of which are:

[0082] S1: Smelting. After the ingot is taken out of the furnace, the temperature of the heating equipment is lowered to 800℃ and kept warm for 20 minutes;

[0083] S2: After quenching the ingot in a quenching agent containing neodymium at 150°C, the ingot is taken out and placed in air to cool to room temperature;

[0084] S3: The ingot cooled in step S2 is tempered at 420°C for 150 minutes;

[0085] S4: hot extrusion, cold rolling, heat treatment and annealing;

[0086] S5: Then it is sent to the tapered roller piercing machine. After piercing, it is extruded, rolled, and sized to form a steel pipe.

[0087] The smelting adopts vacuum induction melting / electroslag remelting.

[0088] The furnace is washed twice with pure iron before smelting.

[0089] The charge of the vacuum induction furnace is: 0.05% C, 0.2% Si, 0.04% Mn, 0.05% P, 0.002% S, 14% Cr, 0.6% Cu, 60% Ni, 5% Mo, 0.2% Al, 0.3% Co, 0.23% Ti, 4.2% Nb, and the rest is Fe.

[0090] The vacuum degree of the vacuum induction furnace is 1 Pa, and the melting power is 1600 kW.

[0091] The melting rate of the electroslag remelting is 500 kg / h.

[0092] The slag forming period of the electroslag remelting has a current of 8KA, a voltage of 90V, and a time of 40min; the remelting period has a current of 16KA, a voltage of 100V, and a time of 600min; and the feeding period has a current of 10KA, a voltage of 80V, and a time of 70min.

[0093] The heat treatment temperature is 1050° C. and the time is 30 minutes.

[0094] The preparation method of the neodymium-containing quenching agent is as follows:

[0095] M1: Add 3.2 kg of neodymium sulfate, 2.6 kg of epoxysuccinic acid, and 150 kg of ethanol into a stirred tank and stir at 50°C for 50 min;

[0096] M2: Add 0.3 kg of mercaptobenzoimidazole and 4 kg of sodium ethoxide to the stirred kettle, stir at 80°C for 100 minutes; then add 34 kg of thioglycolic acid ethanol; stir at 70°C for 150 minutes; remove the ethanol by vacuum distillation, then add 150 kg of polyvinyl alcohol and 1500 kg of water, stir at 50°C for 50 minutes to obtain the neodymium-containing quenching agent.

[0097] Comparative Example 1

[0098] In this comparative example, no neodymium-containing quenching agent is added during the preparation of the heat exchange tubes, and the other steps are the same as those in Example 1.

[0099] Comparative Example 2

[0100] In this comparative example, mercaptobenzoimidazole is not added in the preparation of the neodymium-containing quenching agent, and the other procedures are the same as in Example 1.

[0101] Comparative Example 3

[0102] In this comparative example, ethanol thioglycolate is not added in the preparation of the neodymium-containing quenching agent, and the other procedures are the same as in Example 1.

[0103] Test results:

[0104]

[0105] Through the data analysis of the above examples and comparative examples, the neodymium-containing quenching agent prepared by the present invention can further improve the corrosion resistance of the heat exchange tube.

[0106] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a corrosion-resistant heat exchange tube, the operating steps of which are: S1: Smelting. After the ingot is taken out of the furnace, the temperature of the heating equipment is lowered to 700-800℃ and kept warm for 10-20 minutes; S2: After quenching the ingot in a quenching agent containing neodymium at 120-150°C, the ingot is taken out and placed in air to cool to room temperature; S3: The ingot cooled in step S2 is tempered at 400-420°C for 100-150 minutes; S4: hot extrusion, cold rolling, heat treatment and annealing; The heat treatment temperature is 950-1050°C and the time is 15-30 minutes; S5: Then it is sent to the tapered roller piercing machine, and after piercing, it is extruded, rolled, and sized to form a steel pipe; The preparation method of the neodymium-containing quenching agent is as follows: M1: Add 1.6-3.2 parts of neodymium sulfate, 1.3-2.6 parts of epoxysuccinic acid, and 100-150 parts of ethanol to a stirred tank, stirring at 40-50°C for 30-50 minutes; M2: Add 0.02-0.3 parts of mercaptobenzoimidazole and 1-4 parts of sodium ethoxide to a stirred kettle, stir at 60-80°C for 30-100 minutes; then add 17-34 parts of thioglycolic acid ethanol; stir at 60-70°C for 100-150 minutes; remove the ethanol by vacuum distillation, then add 100-150 parts of polyvinyl alcohol and 1000-1500 parts of water, stir at 40-50°C for 30-50 minutes to obtain a neodymium-containing quenching agent; The charge of the vacuum induction furnace is: 0.02-0.05% C, 0.08-0.2% Si, 0.01-0.04% Mn, 0.02-0.05% P, 0.001-0.002% S, 12-14% Cr, 0.3-0.6% Cu, 55-60% Ni, 3-5% Mo, 0.16-0.2% Al, 0.1-0.3% Co, 0.14-0.23% Ti, 3.2-4.2% Nb, and the rest is Fe.

2. The method for preparing a corrosion-resistant heat exchange tube according to claim 1, characterized in that: The smelting adopts vacuum induction melting / electroslag remelting.

3. The method for preparing a corrosion-resistant heat exchange tube according to claim 2, characterized in that: The furnace is washed twice with pure iron before smelting.

4. The method for preparing a corrosion-resistant heat exchange tube according to claim 2, characterized in that: The vacuum degree of the vacuum induction furnace is 0.8-1 Pa, and the melting power is 1200-1600 kW.

5. The method for preparing a corrosion-resistant heat exchange tube according to claim 2, characterized in that: The melting rate of the electroslag remelting is 400-500 kg / h.

6. The method for preparing a corrosion-resistant heat exchange tube according to claim 2, characterized in that: The slag forming period of the electroslag remelting is characterized by a current of 4-8KA, a voltage of 60-90V, and a time of 20-40min; a current of 10-16KA, a voltage of 80-100V, and a time of 500-600min during the remelting period; and a current of 8-10KA, a voltage of 60-80V, and a time of 50-70min during the feeding period.

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