Water-based expansion liquid and hydraulic expansion processing method of metal corrugated pipe

Abstract

The invention discloses a water-based expansion liquid and a hydraulic expansion processing method of a metal corrugated pipe. The water-based expansion liquid comprises 8-15% of emulsified oil, 1-3% of an antirust agent, 2-4% of a viscosity modifier and the balance of a solvent, the antirust agent is prepared from comonomers through free radical copolymerization, and the comonomers comprise unsaturated carboxylic acid monomers, allyl imidazole and siloxane monomers with alkenyl in a mass ratio of (30-50): (15-45): (5-15). The water-based expansion liquid can guarantee the anti-rust performance of the metal corrugated pipe in the machining process, and the product reject ratio of a water-based hydraulic expansion process is reduced.

Description

Technical Field

[0001] The present application relates to the field of metal processing, and in particular to a water-based expansion fluid and a hydraulic expansion processing method for a metal bellows. Background Art

[0002] In the fields of automobiles, gas, air conditioning, refrigerators, heating, etc., metal bellows can be used as components to achieve functions such as flow control, compensating seals and pressure sensing. Specifically, metal bellows can connect different components, compensate for thermal expansion and contraction in the pipeline system, provide reliable sealing, reduce vibration and noise, and as part of the pressure sensing element, convert pressure changes into deformation for easy sensor detection. This type of bellows is usually open at one end and sealed at the other end. It is mostly made of copper alloy and stainless steel and has good corrosion resistance and mechanical properties.

[0003] At present, the production and preparation of metal bellows is mainly achieved through hydraulic expansion process. The specific steps of this process are as follows: first, put the metal tube with an opening into a special mold, and then pass high-pressure liquid from the opening of the cylinder to expand the metal tube radially to form an expanded intermediate with multiple uniform bands along the axial direction. Next, axial pressure is applied to the expanded intermediate, and it is pressed and formed to finally obtain the required metal bellows. This process can accurately control the shape and size of the bellows, ensuring that it has excellent mechanical properties and sealing properties.

[0004] At present, the expansion fluid commonly used in the hydraulic expansion process is mostly oil, which has good lubricity, sealing and pressure transmission, and can effectively ensure the smooth progress of the hydraulic expansion process, but it also has obvious defects. First, the oil is easy to cause environmental pollution during use, especially in the production and subsequent processing, the leakage and volatilization of the oil will cause pollution to the air and water sources. Secondly, the cleaning cost of the oil is high, requiring special cleaning equipment and chemical reagents, which increases the production cost. In addition, the recovery and treatment of the oil is also relatively complicated, which does not meet the requirements of environmental protection and sustainable development.

[0005] To solve the above problems, the prior art also provides a water-based expansion process, such as the patent with publication number CN204866973U, which provides a water-forming device for the production of metal bellows, which has the characteristics of simple structure, energy saving, environmental protection and stable product performance. However, it should be noted that the use of water-based expansion fluid can easily cause the metal bellows to rust, affecting its performance and life. Summary of the invention

[0006] In order to solve the problem that the current water-based swelling fluid easily causes the metal bellows to rust during the processing, the present application provides a water-based swelling fluid and a hydraulic swelling processing method for the metal bellows, which has a good anti-rust effect.

[0007] In a first aspect, the present application provides a water-based swelling fluid, comprising the following components in percentage by weight: Emulsified oil 8-15%, rust inhibitor 1-3%, viscosity regulator 2-4%, solvent as the balance; The rust inhibitor is prepared by free radical copolymerization of comonomers, wherein the comonomers include unsaturated carboxylic acid monomers, allyl imidazole, and siloxane monomers having alkenyl groups in a mass ratio of 30 to 50:15 to 45:5 to 15.

[0008] Preferably, the unsaturated carboxylic acid monomer is selected from at least one of acrylic acid, itaconic acid, maleic acid and fumaric acid.

[0009] Preferably, the siloxane monomer having an alkenyl group is at least one selected from methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, vinyltrimethoxysilane and vinyltriethoxysilane.

[0010] In the present application, the rust inhibitor adopts unsaturated carboxylic acid monomer, allyl imidazole, and siloxane monomer with alkenyl, which can firmly adhere to the metal surface to form a pre-film with rust prevention effect. Specifically, in the comonomer of the rust inhibitor, the unsaturated carboxylic acid monomer can provide a carboxylic acid group, which can give the product hydrophilicity and a certain complexation effect. Allyl imidazole can coordinate with the copper metal ion on the metal surface through its nitrogen-containing heterocycle to form a relatively stable connection. In addition, the siloxane monomer can also strengthen the chemical connection with the metal surface through the silicon hydroxyl group, so as to achieve firm attachment and effective rust prevention effect.

[0011] Preferably, the comonomer further comprises allyl imidazole salt, and the mass ratio of allyl imidazole to allyl imidazole salt is 15-45:10-20.

[0012] Preferably, the allyl imidazolium salt is selected from at least one of 1-allyl-3-methylimidazolium chloride, 1-allyl-3-ethylimidazolium chloride, 1-allyl-3-butylimidazolium chloride, 1-allyl-3-methylimidazolium bromide, 1-allyl-3-ethylimidazolium bromide and 1-allyl-3-butylimidazolium bromide.

[0013] After allyl imidazole salt participates in the copolymerization reaction, charged groups can be introduced into the rust inhibitor. On the one hand, the film-forming stability is improved through electrostatic action, and the rust-proof ability of the rust inhibitor is enhanced. On the other hand, since the rust inhibitor can form a complex with the metal ions or metal particles in the swelling liquid, the complex is easy to form flocculation precipitation through the bridging effect of the ligand, causing pipeline blockage and other phenomena that affect operation. By introducing charged groups, the flocculation precipitation of the complex can be effectively reduced to ensure the normal operation of the equipment.

[0014] Preferably, the solvent is a mixture of water, short-chain alcohol and citric acid in a mass ratio of 85-90:3-5:6-12.

[0015] Preferably, the short-chain alcohol is selected from at least one of ethanol, isopropanol and ethylene glycol.

[0016] Short-chain alcohols and citric acid can improve the solubility of rust inhibitors and ensure the rust prevention effect. In addition, limonin can provide an acidic environment for the complexation reaction between the rust inhibitor and the metal bellows, thereby enhancing the film fastness.

[0017] This application has no special requirements for the selection of emulsified oil, and its base oil can be mineral oil, vegetable oil or synthetic oil; appropriate amounts of extreme pressure agents, rust inhibitors, antioxidants, defoaming agents and other additives can be added to the emulsified oil according to usage requirements.

[0018] Preferably, the viscosity modifier is cellulose ether and epoxidized soybean oil in a mass ratio of 2 to 3:1.

[0019] Preferably, the cellulose ether is selected from at least one of methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, ethyl cellulose, benzyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose, more preferably at least one of methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose and hydroxyethyl cellulose.

[0020] Preferably, the viscosity of the cellulose ether is 5000 to 20000 mPa·s.

[0021] Preferably, the viscosity of the epoxidized soybean oil is 200-400 cSt (25° C.).

[0022] Compared with hydraulic oil, water-based swelling fluid has lower viscosity and poor pressure transmission ability. During the molding process, there are defects such as insufficient local pressure and uneven thickness of molded parts. The present application helps to increase the viscosity of the water-based swelling fluid by adding cellulose ether, so that the swelling force can be more evenly distributed on the surface of the workpiece and reduce stress concentration. Moreover, the increase in viscosity helps to reduce the occurrence of flocculation and precipitation. In addition, the addition of epoxy soybean oil can reduce the friction coefficient between the metal pipe workpiece and the mold without significantly affecting the viscosity, so that the swelling force can be more evenly distributed on the surface of the workpiece, reduce the stress concentration caused by uneven friction, and reduce the possibility of defects such as cracks and deformation in the product. In addition, the epoxy soybean oil of the present application has good solubility in short-chain alcohols such as ethanol.

[0023] In a second aspect, the present application provides a method for hydraulically forming a metal bellows, which comprises the following steps: The metal tube is placed in a forming mold, and any of the above-mentioned water-based expansion liquids is injected into the inner cavity of the metal tube through a hydraulic expansion device to expand the metal tube to form an expanded intermediate having multiple bands along the axial direction; axial pressure is applied to the expanded intermediate to press and form it to obtain a metal bellows.

[0024] The metal tube is opened at least at one end, and is placed in a mold. The expansion liquid inlet pipe is inserted into the metal tube, and then the expansion liquid is injected through a high-pressure pump until a predetermined pressure is reached. In this process, the metal tube gradually expands to fit the inner wall of the mold, and then the expansion liquid is slowly discharged and the pressure is released to obtain an expansion intermediate of a preset shape, which has multiple uniform bands along the axial direction to facilitate the subsequent formation of a corrugated structure. The use of hydraulic equipment can achieve axial compression of the expansion intermediate to obtain a metal bellows with axial deformation ability.

[0025] Preferably, the material of the metal tube is selected from tin bronze, beryllium bronze or stainless steel.

[0026] In summary, this application has the following beneficial effects: The present application uses unsaturated carboxylic acid monomers, allyl imidazole, allyl imidazole salts, and siloxane monomers with alkenyl groups as raw materials for free radical copolymerization to obtain a rust inhibitor that can be coordinated and complexed with metal bellows to achieve long-term and efficient rust prevention. It can also prevent the rust inhibitor from forming flocculated precipitates with metal particles in the swelling liquid to prevent pipe blockage. In addition, the present application can reduce the uneven pressure distribution during the swelling process, reduce stress concentration problems, and reduce the defective rate of formed workpieces by adding cellulose ether and epoxy soybean oil to the water-based swelling liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the expansion intermediate in this application.

[0028] Figure 2 It is a schematic diagram of the structure of the metal bellows in this application. DETAILED DESCRIPTION Preparation Example

[0029] Preparation Example 1, a rust inhibitor, the preparation steps are as follows: 6L of isopropanol was added to the reaction vessel, followed by 420g of maleic acid, 330g of 1-allylimidazole, 120g of 1-allyl-3-methylimidazole chloride, and 80g of methacryloxypropyltriethoxysilane, and stirred to dissolve. Nitrogen was introduced into the reaction vessel to exhaust the air in the reaction vessel.

[0030] Weigh 14.3g of dibenzoyl peroxide and dissolve it in acetone to prepare a 10wt% initiator solution for use. Heat the reaction vessel. When the reaction temperature rises to 55°C, pump the initiator solution into the reaction vessel through a micro pump, and control the pumping time to be 0.5h. After the addition is completed, heat to 65°C and keep the reaction for 6h. After the reaction is completed, cool to room temperature, then add sodium hydroxide solution dropwise to the reaction vessel to make the pH value of the system 7.5-8.0, discharge the material, remove the solvent by reduced pressure distillation, obtain the product, wash it twice with ether, put it in an oven, and dry it at 50°C to constant weight to obtain a rust inhibitor.

[0031] Preparation Example 2, a rust inhibitor, the preparation steps are as follows: Add 5L of isopropanol to the reaction container, then add 350g of acrylic acid, 160g of 1-allylimidazole, 110g of 1-allyl-3-methylimidazole chloride, and 150g of vinyltriethoxysilane in sequence, stir and dissolve. Pass nitrogen into the reaction container to exhaust the air in the reaction container.

[0032] Weigh 10.0g of dibenzoyl peroxide and dissolve it in acetone to prepare a 10wt% initiator solution for use. Heat the reaction vessel. When the reaction temperature rises to 60°C, pump the initiator solution into the reaction vessel through a micro pump, and control the pumping time to be 0.5h. After the addition is completed, heat to 70°C and keep the reaction for 5h. After the reaction is completed, cool to room temperature, then add sodium hydroxide solution dropwise to the reaction vessel to make the pH value of the system 7.5-8.0, discharge the material, remove the solvent by reduced pressure distillation, obtain the product, wash it twice with ether, put it in an oven, and dry it at 50°C to constant weight to obtain a rust inhibitor.

[0033] Preparation Example 3, a rust inhibitor, the preparation steps are as follows: 6L of isopropanol was added to the reaction vessel, followed by 500g of maleic acid, 430g of 1-allylimidazole, 200g of 1-allyl-3-methylimidazolium bromide, and 50g of vinyltriethoxysilane, and stirred to dissolve. Nitrogen was introduced into the reaction vessel to exhaust the air in the reaction vessel.

[0034] Weigh 15g of dibenzoyl peroxide and dissolve it in acetone to prepare a 10wt% initiator solution for use. Heat the reaction vessel. When the reaction temperature rises to 55°C, pump the initiator solution into the reaction vessel through a micro pump, and control the pumping time to be 1h. After the addition is completed, heat to 68°C and keep the reaction for 7h. After the reaction is completed, cool to room temperature, then add sodium hydroxide solution dropwise to the reaction vessel to make the pH value of the system 7.5-8.0, discharge the material, remove the solvent by reduced pressure distillation, obtain the product, wash it twice with ether, put it in an oven, and dry it at 50°C to constant weight to obtain a rust inhibitor.

[0035] Preparation Example 4, a rust inhibitor, is different from Preparation Example 1 in that 1-allylimidazole is used to replace 1-allylimidazole chloride in an equal amount.

[0036] Preparation Example 5, a rust inhibitor, is different from Preparation Example 1 in that 1-allylimidazole is replaced by an equal amount of methacryloxypropyltriethoxysilane. Example

[0037] In the embodiment, the raw materials are selected as follows: the emulsified oil is Great Wall anti-rust emulsified oil M1010, the viscosity of carboxymethyl cellulose is 10000 mPa·s, the viscosity of hydroxyethyl methyl cellulose is 10000 mPa·s; the viscosity of epoxidized soybean oil is 200 cSt (25°C).

[0038] Embodiment 1, a method for hydraulically forming a metal bellows, comprising the following steps: The tin bronze metal tube is placed in the forming mold of the hydraulic expansion equipment, and a water-based expansion liquid is injected into the inner cavity of the metal tube from the open end of the metal tube by a high-pressure pump to expand the metal tube to form an expansion intermediate with multiple bands along the axial direction. Axial pressure is applied to the expansion intermediate to press and form it to obtain a metal bellows.

[0039] The raw material ratio of each 1000g water-based swelling liquid is: 100g of emulsified oil, 20g of the rust inhibitor of Preparation Example 1, 30g of viscosity modifier, and 850g of solvent. Among them, the viscosity modifier is carboxymethyl cellulose and epoxy soybean oil in a mass ratio of 2:1; the solvent is water, ethanol and citric acid in a mass ratio of 85:5:10. The above raw materials are mixed and stirred for 30 minutes to obtain the water-based swelling liquid.

[0040] Embodiment 2, a method for hydraulically forming a metal bellows, comprising the following steps: The tin bronze metal tube is placed in the forming mold of the hydraulic expansion equipment, and a water-based expansion liquid is injected into the inner cavity of the metal tube from the open end of the metal tube by a high-pressure pump to expand the metal tube to form an expansion intermediate with multiple bands along the axial direction. Axial pressure is applied to the expansion intermediate to press and form it to obtain a metal bellows.

[0041] The raw material ratio of each 1000g water-based swelling liquid is: 150g of emulsified oil, 10g of the rust inhibitor of Preparation Example 2, 20g of viscosity modifier, and 820g of solvent. Among them, the viscosity modifier is hydroxyethyl methyl cellulose and epoxy soybean oil in a mass ratio of 3:1; the solvent is water, ethanol and citric acid in a mass ratio of 90:3:7. The above raw materials are mixed and stirred for 30 minutes to obtain the water-based swelling liquid.

[0042] Embodiment 3, a method for hydraulically forming a metal bellows, comprising the following steps: The beryllium bronze metal tube is placed in the forming mold of the hydraulic expansion equipment, and a water-based expansion liquid is injected into the inner cavity of the metal tube from the open end of the metal tube by a high-pressure pump to expand the metal tube to form an expanded intermediate with multiple bands along the axial direction. Axial pressure is applied to the expanded intermediate to form a metal bellows.

[0043] The raw material ratio of each 1000g water-based swelling liquid is: 80g of emulsified oil, 30g of the rust inhibitor of Preparation Example 3, 40g of viscosity modifier, and 850g of solvent. Among them, the viscosity modifier is carboxymethyl cellulose and epoxy soybean oil in a mass ratio of 2:1; the solvent is water, ethylene glycol, and citric acid in a mass ratio of 85:3:12. The above raw materials are mixed and stirred for 30 minutes to obtain the water-based swelling liquid.

[0044] Example 4, a method for hydraulic expansion of a metal bellows, differs from Example 1 in that the rust inhibitor of Preparation Example 1 is replaced by an equal amount of the rust inhibitor of Preparation Example 4.

[0045] Example 5, a method for hydraulic expansion of a metal bellows, differs from Example 1 in that an equal amount of carboxymethyl cellulose is used to replace the epoxidized soybean oil.

[0046] Example 6, a method for hydraulic expansion of a metal bellows, differs from Example 1 in that an equal amount of epoxy soybean oil is used to replace carboxymethyl cellulose.

[0047] Example 7, a method for hydraulic expansion processing of a metal bellows, differs from Example 1 in that an equal amount of water is used to replace citric acid in the solvent.

[0048] Example 8, a method for hydraulic expansion processing of a metal bellows, differs from Example 1 in that equal amounts of water are used to replace citric acid and ethanol in the solvent. Comparative Example

[0049] Comparative Example 1, a method for hydraulic expansion of a metal bellows, differs from Example 8 in that the rust inhibitor of Preparation Example 1 is replaced by an equal amount of the rust inhibitor of Preparation Example 5.

[0050] Comparative Example 2, a method for hydraulic expansion of a metal bellows, differs from Example 8 in that the rust inhibitor of Preparation Example 1 is replaced by an equal amount of triethanolamine rust inhibitor. Performance testing

[0051] Test 1: Anti-rust performance test Three specimens were selected from the metal bellows prepared in the above-mentioned embodiments and comparative examples, respectively. The specimens were sheared and flattened along the axial direction to expose the inner wall as the evaluation surface. The specimens were placed in a wet heat test chamber for testing with reference to the test conditions specified in GB / T 2361-1992. The test period when rust appeared on the evaluation surface was taken as the anti-rust time.

[0052] Test 2: Water-based swelling fluid performance test Take 1L of the water-based swelling liquid of the above example and comparative example, add 100ml of 1mol / L CuCl2 aqueous solution respectively, stir for 1h, and observe whether flocculation precipitate is generated in the solution.

[0053] Test 3: Metal bellows yield test The finished metal bellows products obtained in the embodiment and the comparative example were observed, and those with cracks, deformation, and uneven thickness were recorded as defective products, and their yield rates were obtained by statistics.

[0054] Table 1. Performance test results

[0055] Combining Examples 1 to 8 and Comparative Examples 1 to 2 with Table 1, it can be seen that the rust inhibitor prepared by copolymerization of unsaturated carboxylic acid monomers, allyl imidazoles, and siloxane monomers having alkenyl groups in the present application is far superior to commercially available rust inhibitors in terms of rust prevention period. The reason may be that the rust inhibitor of the present application can form a more firm and stable chemical connection with the metal surface by introducing imidazole groups and siloxane groups, thereby obtaining a more durable pre-film structure.

[0056] Combining Example 1 with Examples 4 and 6, it can be seen that the introduction of allyl imidazole salts into the rust inhibitor or the addition of cellulose ethers into the swelling liquid can help reduce the generation of flocculated precipitates in the swelling liquid. The reason may be that the use of allyl imidazole salts is that the rust inhibitor has charged groups, which can inhibit the bridging effect between complexes through electrostatic action and inhibit the generation of macromolecular flocculated precipitates. The viscosity-increasing effect of cellulose ethers also helps to inhibit the aggregation and precipitation tendency between complexes.

[0057] Combining Example 1 with Examples 7 and 8, it can be seen that the addition of organic acid and short-chain alcohol in the solvent helps to improve the anti-rust effect of the swelling liquid. The reason may be that organic acid and short-chain alcohol can increase the solubility of each component and promote the coordination and complex reaction between the rust inhibitor and the surface of the metal bellows.

[0058] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A water-based swelling fluid, characterized in that: The components include the following mass percentages: Emulsified oil 8-15%, rust inhibitor 1-3%, viscosity regulator 2-4%, solvent as the balance; The rust inhibitor is prepared by free radical copolymerization of comonomers, wherein the comonomers include unsaturated carboxylic acid monomers, allyl imidazole, and siloxane monomers having alkenyl groups in a mass ratio of 30 to 50:15 to 45:5 to 15.

2. The water-based swelling fluid according to claim 1, characterized in that: The unsaturated carboxylic acid monomer is selected from at least one of acrylic acid, itaconic acid, maleic acid and fumaric acid.

3. The water-based swelling fluid according to claim 1, characterized in that: The siloxane monomer having an alkenyl group is selected from at least one of methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, vinyltrimethoxysilane and vinyltriethoxysilane.

4. The water-based swelling fluid according to claim 1, characterized in that: The comonomer further comprises allyl imidazole salt, and the mass ratio of the allyl imidazole to the allyl imidazole salt is 15-45:10-20.

5. The water-based swelling fluid according to claim 4, characterized in that: The allyl imidazolium salt is selected from at least one of 1-allyl-3-methylimidazolium chloride, 1-allyl-3-ethylimidazolium chloride, 1-allyl-3-butylimidazolium chloride, 1-allyl-3-methylimidazolium bromide, 1-allyl-3-ethylimidazolium bromide and 1-allyl-3-butylimidazolium bromide.

6. The water-based swelling fluid according to claim 1, characterized in that: The solvent is a mixture of water, short-chain alcohol and citric acid in a mass ratio of 85-90:3-5:6-12.

7. The water-based swelling fluid according to claim 6, characterized in that: The short-chain alcohol is selected from at least one of ethanol, isopropanol and ethylene glycol.

8. The water-based swelling fluid according to claim 1, characterized in that: The viscosity modifier is cellulose ether and epoxidized soybean oil in a mass ratio of 2 to 3:

1.

9. The water-based swelling fluid according to claim 8, characterized in that The cellulose ether is selected from at least one of methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, ethyl cellulose, benzyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

10. A method for hydraulically forming a metal bellows, characterized in that: The steps include: A metal tube is placed in a forming mold, and a water-based expansion liquid as described in any one of claims 1 to 9 is injected into the inner cavity of the metal tube through a hydraulic expansion device to expand the metal tube to form an expanded intermediate having multiple bands along the axial direction; an axial pressure is applied to the expanded intermediate to press and form it to obtain a metal corrugated tube.

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