Cold rolling machining process for titanium alloy pipe

Abstract

The invention relates to the technical field of metal processing, and discloses a titanium alloy pipe cold rolling processing technology which comprises the steps of blank pretreatment, surface coating treatment, multi-pass cold rolling, intermediate annealing, precise sizing and straightening, final heat treatment and cleaning inspection. In the surface coating treatment, a special polymer lubricating coating is coated and cured to form a continuous film, so that the surface cleanliness and lubricating performance of the pipe blank are improved, friction and surface damage in the cold rolling process are reduced, and it is guaranteed that the surface quality of the pipe is good and machining is conducted smoothly; through multi-pass cold rolling, deformation is controlled, rolling force is monitored, work hardening is eliminated in combination with intermediate annealing, and size precision and straightness are adjusted through precise sizing and straightening, so that the machining process is stable and controllable, internal stress is released, pipe deformation and cracks are avoided, and forming consistency and geometric precision are improved.

Description

Technical Field

[0001] This invention relates to the field of metal processing technology, specifically to a cold rolling process for titanium alloy tubes. Background Technology

[0002] Titanium alloy tubing is a tubular material made from titanium alloy. This type of tubing has excellent corrosion resistance to chlorides, sulfides, and seawater, and strong resistance to water impact, making it suitable for high-velocity polluted seawater environments. Titanium and its alloys are already used in general industries for making electrodes in the electrolysis industry, condensers in power plants, heaters in petroleum refining and seawater desalination, and environmental pollution control devices, etc.

[0003] Currently, in the cold rolling process of titanium alloy tubes, insufficient surface cleanliness and lubrication of the tube blank can easily lead to excessive frictional resistance during cold rolling, causing scratches on the tube surface or internal stress concentration. At the same time, improper control of processing deformation or lack of effective intermediate annealing can easily cause work hardening accumulation, resulting in cracks or out-of-tolerance dimensional accuracy of the tube. In addition, if the final heat treatment process is unstable or the cleaning and inspection are not thorough, it will affect the uniformity of the tube's structure and mechanical properties, making it difficult to guarantee the reliability and consistency of the finished product quality.

[0004] Therefore, a cold rolling process for titanium alloy tubes is proposed to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a cold rolling process for titanium alloy tubes, which solves the problems mentioned in the background art, such as surface scratches or internal stress concentration, cracks or dimensional inaccuracies, and difficulty in ensuring the reliability and consistency of finished product quality.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a cold rolling process for titanium alloy tubes, comprising the following steps:

[0007] Step 1: Billet pretreatment. Select titanium alloy tube billets and perform cleaning, degreasing, drying, and dimensional and surface defect inspection.

[0008] Step 2: Surface coating treatment. A special polymer lubricating coating is applied to the inner and outer surfaces of the tube blank and cured at 80-120℃ for 10-30 minutes to form a continuous film.

[0009] Step 3: Multi-pass cold rolling. The tube blank is subjected to multi-pass cold rolling with small deformation at room temperature. The total deformation and the deformation per pass are controlled, and the rolling force and dimensional changes are monitored.

[0010] Step 4: Intermediate annealing, stress-relief annealing at 550-650℃ under a protective atmosphere to eliminate work hardening;

[0011] Step 5: Precision sizing and straightening. Perform 1-2 passes of precision cold rolling sizing, followed by straightening to ensure dimensional accuracy and straightness.

[0012] Step Six: Final heat treatment, including solution treatment and aging treatment of the pipe to adjust its microstructure and properties;

[0013] Step 7: Cleaning and inspection to remove residual coatings and oxides, followed by non-destructive testing and dimensional inspection;

[0014] In step two, the special polymer lubricating coating is composed of the following raw materials in parts by weight:

[0015] 60% solids content polytetrafluoroethylene dispersion: 30-50 parts;

[0016] Ultra-high molecular weight polyethylene powder with a particle size of 1-5 μm: 10-20 parts;

[0017] Nano-molybdenum disulfide: 5-10 parts;

[0018] Silane coupling agent KH-550: 1-3 parts;

[0019] Thickener, hydroxymethyl cellulose: 2-5 parts;

[0020] Deionized water: 20-35 parts.

[0021] Preferably, the titanium alloy tube blank in step one is made of TC4 or TC11, with an outer diameter range of Φ50-150mm, a wall thickness range of 5-15mm, and a length-to-diameter ratio of less than 30.

[0022] The pretreatment includes: first soaking and cleaning with alkaline degreasing solution at 50-70℃ for 10-20 minutes, then rinsing with deionized water, followed by dehydration with anhydrous ethanol, and finally drying in a circulating hot air drying oven at 60-80℃ for 30-60 minutes.

[0023] Preferably, in step two, the special polymer lubricating coating is applied using a high-pressure airless spraying device, with the spraying pressure controlled at 8-15 MPa, the wet film thickness of the coating being 50-100 μm, and the dry film thickness being 15-30 μm.

[0024] The curing process is carried out in a circulating hot air oven, with the heating rate controlled at 2-5℃ / minute.

[0025] Preferably, in step three, the deformation of the multi-pass cold rolling is carried out on a two-roll or three-roll cold rolling mill, and the total deformation is controlled within the range of 50%-75%.

[0026] The deformation per pass is less than 15%, and the rolling speed is controlled at 20-60 meters per minute;

[0027] During the cold rolling process, emulsion is used for cooling and auxiliary lubrication. The emulsion concentration is 3%-8%, the flow rate is 50-150L / min, and the inlet temperature is below 35℃.

[0028] Preferably, the deformation amount of cold rolling passes follows the principle of "larger at the beginning and smaller at the end, gradually decreasing". The deformation amount of the first 3 passes is set at 12%-15%, the middle passes at 8%-12%, and the last 2-3 passes at 5%-8%.

[0029] The emulsion is composed of the following components: 40-60% mineral oil base fluid, 10-15% nonionic surfactant, 3-5% rust inhibitor, 2-4% extreme pressure anti-wear agent, 0.1-0.5% defoamer, 0.5-1% bactericide, and the balance being deionized water.

[0030] Preferably, in step four, the stress-relief annealing is carried out under an argon protective atmosphere, with an annealing temperature of 550-650℃ and a holding time of 60-120 minutes. After cooling in the furnace to below 300℃, the furnace is removed and air-cooled. The oxygen content in the protective atmosphere furnace is controlled below 10ppm.

[0031] Preferably, the deformation amount of the precision sizing pass in step five is strictly controlled between 1% and 3%, and the rolling speed is stabilized at 10-20 meters per minute;

[0032] The straightening process uses a six- or seven-roller straightening machine. The straightening force is adjusted according to the pipe specifications and yield strength. The straightness error of the pipe after straightening is less than 0.5 mm / m.

[0033] Preferably, the solution treatment in step six is ​​carried out in a vacuum furnace or under the protection of high-purity argon, with a solution temperature of 920-980℃ and a holding time of 30-60 minutes, followed by oil quenching or strong cooling with high-purity argon.

[0034] The aging treatment is carried out in an air-circulating furnace at an aging temperature of 500-600℃ for 2-6 hours, followed by air cooling to room temperature.

[0035] Preferably, the cleaning in step seven employs a two-stage cleaning process:

[0036] First, use a weak alkaline cleaning agent at 60-80℃ with a pH of 8-10 to spray and rinse for 5-10 minutes, then use deionized water for ultrasonic cleaning for 5-15 minutes.

[0037] The non-destructive testing includes eddy current testing and ultrasonic testing, and the dimensional inspection includes the measurement of outer diameter, wall thickness, ellipticity, and wall thickness non-uniformity.

[0038] Preferably, in the multi-pass cold rolling process of step three, after every 3-4 rolling passes, the billet is subjected to online dimensional measurement and shape correction. The measurement interval is controlled at 15-30 minutes. The correction is performed by locally fine-tuning the roll gap, with the adjustment range being less than ±10% of the deformation amount set for the current pass.

[0039] Furthermore, during the final heat treatment process in step six, the quenching transfer time after solution treatment is strictly controlled to be completed within 8-15 seconds.

[0040] Compared with the prior art, the present invention provides a cold rolling process for titanium alloy tubes, which has the following beneficial effects:

[0041] 1. In this invention, the billet pretreatment is carried out to clean and degrease and inspect for surface defects, and a special polymer lubricating coating is applied and cured to form a continuous film, which improves the surface cleanliness and lubrication performance of the billet, reduces friction and surface damage during cold rolling, and ensures the integrity of the pipe surface quality and smooth processing.

[0042] 2. In this invention, the deformation is controlled by multiple cold rolling passes and the rolling force is monitored. Combined with intermediate annealing to eliminate work hardening, and precision sizing and straightening to adjust dimensional accuracy and straightness, the processing is stable and controllable, internal stress is released, tube deformation and cracks are avoided, and forming consistency and geometric accuracy are improved.

[0043] 3. In this invention, the mechanical properties and corrosion resistance of the pipe are optimized by adjusting the microstructure through final heat treatment, and by performing non-destructive testing and dimensional measurement through cleaning and inspection. At the same time, it ensures that product defects are detected in a timely manner and that the dimensions meet the requirements, thereby ensuring product quality reliability and extending service life. Attached Figure Description

[0044] Figure 1 This is a flowchart of a cold rolling process for titanium alloy tubing according to the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1: A cold rolling process for titanium alloy tubing, comprising the following steps:

[0047] Step 1: Billet pretreatment. Select titanium alloy tube billets and perform cleaning, degreasing, drying, and dimensional and surface defect inspection.

[0048] Step 2: Surface coating treatment. A special polymer lubricating coating is applied to the inner and outer surfaces of the tube blank and cured at 80°C for 10 minutes to form a continuous film.

[0049] Step 3: Multi-pass cold rolling. The tube blank is subjected to multi-pass cold rolling with small deformation at room temperature. The total deformation and the deformation per pass are controlled, and the rolling force and dimensional changes are monitored.

[0050] Step 4: Intermediate annealing, stress-relief annealing at 550℃ under a protective atmosphere to eliminate work hardening;

[0051] Step 5: Precision sizing and straightening. Perform one pass of precision cold rolling sizing, followed by straightening to ensure dimensional accuracy and straightness.

[0052] Step Six: Final heat treatment, including solution treatment and aging treatment of the pipe to adjust its microstructure and properties;

[0053] Step 7: Cleaning and inspection to remove residual coatings and oxides, followed by non-destructive testing and dimensional inspection;

[0054] In step two, the special polymer lubricating coating is composed of the following raw materials in parts by weight:

[0055] 30 parts of polytetrafluoroethylene dispersion with 60% solid content;

[0056] 10 parts of ultra-high molecular weight polyethylene powder with a particle size of 1 μm;

[0057] Nano-molybdenum disulfide: 5 parts;

[0058] Silane coupling agent KH-550: 1 part;

[0059] Thickener, carboxymethyl cellulose: 2 parts;

[0060] Deionized water: 20 parts.

[0061] In step one, the titanium alloy tube blank is made of TC4 or TC11, with an outer diameter of Φ50mm, a wall thickness of 5mm, and a length-to-diameter ratio of less than 30.

[0062] The pretreatment includes: first soaking and washing with alkaline degreasing solution at 50°C for 10 minutes, then rinsing with deionized water, followed by dehydration with anhydrous ethanol, and finally drying in a circulating hot air drying oven at 60°C for 30 minutes.

[0063] In step two, the special polymer lubricating coating is applied using a high-pressure airless spraying device, with the spraying pressure controlled at 8MPa. The wet film thickness of the coating is 50μm, and the dry film thickness is 15μm.

[0064] Curing is carried out in a circulating hot air oven, with the heating rate controlled at 2℃ / minute.

[0065] In step three, the multi-pass cold rolling deformation is carried out on a two- or three-roll cold rolling mill, and the total deformation is controlled at 50%.

[0066] The deformation per pass is less than 15%, and the rolling speed is controlled at 20 meters per minute;

[0067] During the cold rolling process, an emulsion is used for cooling and auxiliary lubrication. The emulsion concentration is 3%, the flow rate is 50L / min, and the inlet temperature is below 35℃.

[0068] The deformation amount of cold rolling passes follows the principle of "larger at the beginning and smaller at the end, gradually decreasing". The deformation amount of the first 3 passes is set at 12%, the middle passes at 8%, and the last 2 passes at 5%.

[0069] The emulsion is composed of the following components: 40% mineral oil base fluid, 10% nonionic surfactant, 3% rust inhibitor, 2% extreme pressure anti-wear agent, 0.1% defoamer, 0.5% bactericide, and the balance is deionized water.

[0070] In step four, stress-relief annealing is carried out under an argon protective atmosphere at a temperature of 550°C and a holding time of 60 minutes. After cooling in the furnace to below 300°C, the furnace is removed and air-cooled.

[0071] The oxygen content in the protective atmosphere furnace is controlled below 10 ppm.

[0072] In step five, the deformation amount of each pass in precision sizing is strictly controlled within 1%, and the rolling speed is stabilized at 10 meters per minute;

[0073] Precision straightening uses a six- or seven-roller straightening machine. The straightening force is adjusted according to the pipe specifications and yield strength. The straightness error of the pipe after straightening is less than 0.5 mm / m.

[0074] In step six, the solution treatment is carried out in a vacuum furnace or under the protection of high-purity argon gas. The solution temperature is 920℃ and the holding time is 30 minutes, followed by oil quenching or strong cooling with high-purity argon gas.

[0075] The aging treatment was carried out in an air-circulating furnace at an aging temperature of 500℃ for 2 hours, followed by air cooling to room temperature.

[0076] Step seven involves a two-stage cleaning process:

[0077] First, use a weak alkaline cleaning agent at 60℃ with a pH of 8 to spray and rinse for 5 minutes, then use deionized water for ultrasonic cleaning for 5 minutes.

[0078] Non-destructive testing includes eddy current testing and ultrasonic testing, while dimensional inspection includes the measurement of outer diameter, wall thickness, ellipticity, and wall thickness non-uniformity.

[0079] In the multi-pass cold rolling process of step three, after every three rolling passes, the billet is subjected to online dimensional measurement and shape correction. The measurement interval is controlled within 15 minutes. The correction is carried out by local fine adjustment of the roll gap, and the adjustment range is less than ±10% of the deformation amount set for the current pass.

[0080] Furthermore, during the final heat treatment process in step six, the quenching transfer time after solution treatment is strictly controlled to be completed within 8 seconds.

[0081] Example 2: A cold rolling process for titanium alloy tubing, comprising the following steps:

[0082] Step 1: Billet pretreatment. Select titanium alloy tube billets and perform cleaning, degreasing, drying, and dimensional and surface defect inspection.

[0083] Step 2: Surface coating treatment. A special polymer lubricating coating is applied to the inner and outer surfaces of the tube blank and cured at 100°C for 20 minutes to form a continuous film.

[0084] Step 3: Multi-pass cold rolling. The tube blank is subjected to multi-pass cold rolling with small deformation at room temperature. The total deformation and the deformation per pass are controlled, and the rolling force and dimensional changes are monitored.

[0085] Step 4: Intermediate annealing, stress-relief annealing at 600℃ under a protective atmosphere to eliminate work hardening;

[0086] Step 5: Precision sizing and straightening. Two passes of precision cold rolling are performed for sizing, followed by straightening to ensure dimensional accuracy and straightness.

[0087] Step Six: Final heat treatment, including solution treatment and aging treatment of the pipe to adjust its microstructure and properties;

[0088] Step 7: Cleaning and inspection to remove residual coatings and oxides, followed by non-destructive testing and dimensional inspection;

[0089] In step two, the special polymer lubricating coating is composed of the following raw materials in parts by weight:

[0090] 60% solids content polytetrafluoroethylene dispersion: 40 parts;

[0091] 15 parts of ultra-high molecular weight polyethylene powder with a particle size of 3 μm;

[0092] Nano-molybdenum disulfide: 8 parts;

[0093] Silane coupling agent KH-550: 2 parts;

[0094] Thickener, carboxymethyl cellulose: 3.5 parts;

[0095] Deionized water: 28 parts.

[0096] In step one, the titanium alloy tube blank is made of TC4 or TC11, with an outer diameter of Φ100mm, a wall thickness of 10mm, and a length-to-diameter ratio of less than 30.

[0097] The pretreatment process includes: first, soaking and washing with an alkaline degreasing solution at 60°C for 15 minutes, then rinsing with deionized water, followed by dehydration with anhydrous ethanol, and finally drying in a circulating hot air drying oven at 70°C for 45 minutes.

[0098] In step two, the special polymer lubricating coating is applied using a high-pressure airless spraying device, with the spraying pressure controlled at 12MPa, the wet film thickness of the coating being 75μm, and the dry film thickness being 23μm.

[0099] The curing process is carried out in a circulating hot air oven, with the heating rate controlled at 4℃ / minute.

[0100] In step three, the deformation of the multi-pass cold rolling is carried out on a two- or three-roll cold rolling mill, and the total deformation is controlled at 63%.

[0101] The deformation per pass is less than 15%, and the rolling speed is controlled at 40 meters per minute;

[0102] During the cold rolling process, an emulsion is used for cooling and auxiliary lubrication. The emulsion concentration is 6%, the flow rate is 100L / min, and the inlet temperature is below 35℃.

[0103] The deformation amount distribution of cold rolling passes follows the principle of "larger at the beginning and smaller at the end, gradually decreasing". The deformation amount of the first 3 passes is set at 13.5%, the middle passes at 10%, and the last 3 passes at 6.5%.

[0104] The emulsion is composed of the following components: 50% mineral oil base fluid, 13% nonionic surfactant, 4% rust inhibitor, 3% extreme pressure anti-wear agent, 0.3% defoamer, 0.75% bactericide, and the balance is deionized water.

[0105] In step four, stress-relief annealing is carried out under an argon protective atmosphere at a temperature of 600°C and a holding time of 90 minutes. After cooling in the furnace to below 300°C, the furnace is removed and air-cooled. The oxygen content in the protective atmosphere furnace is controlled below 10 ppm.

[0106] In step five, the deformation amount of each pass in precision sizing is strictly controlled within 2%, and the rolling speed is stabilized at 15 meters per minute;

[0107] Precision straightening uses a six- or seven-roller straightening machine. The straightening force is adjusted according to the pipe specifications and yield strength. The straightness error of the pipe after straightening is less than 0.5 mm / m.

[0108] In step six, the solution treatment is carried out in a vacuum furnace or under the protection of high-purity argon gas. The solution temperature is 950℃ and the holding time is 45 minutes, followed by oil quenching or strong cooling with high-purity argon gas.

[0109] The aging treatment was carried out in an air-circulating furnace at an aging temperature of 550°C for 4 hours, followed by air cooling to room temperature.

[0110] Step seven involves a two-stage cleaning process:

[0111] First, use a weak alkaline cleaning agent at 70℃ with a pH of 9 to spray and rinse for 8 minutes, then use deionized water for ultrasonic cleaning for 10 minutes.

[0112] Non-destructive testing includes eddy current testing and ultrasonic testing, while dimensional inspection includes the measurement of outer diameter, wall thickness, ellipticity, and wall thickness non-uniformity.

[0113] In the multi-pass cold rolling process of step three, after every four rolling passes, the billet is subjected to online dimensional measurement and shape correction. The measurement interval is controlled at 23 minutes. The correction adopts the method of local fine adjustment of the roll gap, and the adjustment range is less than ±10% of the deformation amount set for the current pass.

[0114] Furthermore, during the final heat treatment process in step six, the quenching transfer time after solution treatment is strictly controlled to be completed within 12 seconds.

[0115] Example 3: A cold rolling process for titanium alloy tubing, comprising the following steps:

[0116] Step 1: Billet pretreatment. Select titanium alloy tube billets and perform cleaning, degreasing, drying, and dimensional and surface defect inspection.

[0117] Step 2: Surface coating treatment. A special polymer lubricating coating is applied to the inner and outer surfaces of the tube blank and cured at 120°C for 30 minutes to form a continuous film.

[0118] Step 3: Multi-pass cold rolling. The tube blank is subjected to multi-pass cold rolling with small deformation at room temperature. The total deformation and the deformation per pass are controlled, and the rolling force and dimensional changes are monitored.

[0119] Step 4: Intermediate annealing, stress-relief annealing at 650℃ under a protective atmosphere to eliminate work hardening;

[0120] Step 5: Precision sizing and straightening. Two passes of precision cold rolling are performed for sizing, followed by straightening to ensure dimensional accuracy and straightness.

[0121] Step Six: Final heat treatment, including solution treatment and aging treatment of the pipe to adjust its microstructure and properties;

[0122] Step 7: Cleaning and inspection to remove residual coatings and oxides, followed by non-destructive testing and dimensional inspection;

[0123] In step two, the special polymer lubricating coating is composed of the following raw materials in parts by weight:

[0124] 60% solids content polytetrafluoroethylene dispersion: 50 parts;

[0125] 20 parts of ultra-high molecular weight polyethylene powder with a particle size of 5 μm;

[0126] Nano-molybdenum disulfide: 10 parts;

[0127] Silane coupling agent KH-550: 3 parts;

[0128] Thickener, hydroxymethyl cellulose: 5 parts;

[0129] Deionized water: 35 parts.

[0130] In step one, the titanium alloy tube blank is made of TC4 or TC11, with an outer diameter of Φ150mm, a wall thickness of 15mm, and a length-to-diameter ratio of less than 30.

[0131] The pretreatment includes: first soaking and washing with alkaline degreasing solution at 70°C for 20 minutes, then rinsing with deionized water, followed by dehydration with anhydrous ethanol, and finally drying in a circulating hot air drying oven at 80°C for 60 minutes.

[0132] In step two, the special polymer lubricating coating is applied using a high-pressure airless spraying device, with the spraying pressure controlled at 15MPa, the wet film thickness of the coating being 100μm, and the dry film thickness being 30μm.

[0133] The curing process is carried out in a circulating hot air oven, with the heating rate controlled at 5℃ / minute.

[0134] In step three, the deformation of the multi-pass cold rolling is carried out on a two- or three-roll cold rolling mill, and the total deformation is controlled at 75%.

[0135] The deformation per pass is less than 15%, and the rolling speed is controlled at 60 meters per minute;

[0136] During the cold rolling process, an emulsion is used for cooling and auxiliary lubrication. The emulsion concentration is 8%, the flow rate is 150L / min, and the inlet temperature is below 35℃.

[0137] The deformation amount of cold rolling passes follows the principle of "larger at the beginning and smaller at the end, gradually decreasing". The deformation amount of the first 3 passes is set at 15%, the middle passes at 12%, and the last 3 passes at 8%.

[0138] The emulsion is composed of the following components: 60% mineral oil base fluid, 15% nonionic surfactant, 5% rust inhibitor, 4% extreme pressure anti-wear agent, 0.5% defoamer, 1% bactericide, and the balance being deionized water.

[0139] In step four, stress-relief annealing is carried out under an argon protective atmosphere at a temperature of 650°C and a holding time of 120 minutes. After cooling to below 300°C in the furnace, the furnace is removed and air-cooled. The oxygen content in the protective atmosphere furnace is controlled below 10 ppm.

[0140] In step five, the deformation amount of each pass in precision sizing is strictly controlled within 3%, and the rolling speed is stabilized at 20 meters per minute;

[0141] Precision straightening uses a six- or seven-roller straightening machine. The straightening force is adjusted according to the pipe specifications and yield strength. The straightness error of the pipe after straightening is less than 0.5 mm / m.

[0142] In step six, the solution treatment is carried out in a vacuum furnace or under the protection of high-purity argon gas. The solution temperature is 980℃ and the holding time is 60 minutes, followed by oil quenching or strong cooling with high-purity argon gas.

[0143] The aging treatment was carried out in an air-circulating furnace at an aging temperature of 600℃ for 6 hours, followed by air cooling to room temperature.

[0144] Step seven involves a two-stage cleaning process:

[0145] First, use a weak alkaline cleaning agent at 80℃ with a pH of 10 to spray and rinse for 10 minutes, then use deionized water for ultrasonic cleaning for 15 minutes.

[0146] Non-destructive testing includes eddy current testing and ultrasonic testing, while dimensional inspection includes the measurement of outer diameter, wall thickness, ellipticity, and wall thickness non-uniformity.

[0147] In the multi-pass cold rolling process of step three, after every four rolling passes, the billet is subjected to online dimensional measurement and shape correction. The measurement interval is controlled within 30 minutes. The correction is carried out by local fine adjustment of the roll gap, and the adjustment range is less than ±10% of the deformation amount set for the current pass.

[0148] Furthermore, in the final heat treatment process of step six, the quenching transfer time after solution treatment is strictly controlled to be completed within 15 seconds.

[0149] Comparative Example 1: The difference between this comparative example and Example 1 is that the surface coating treatment in step two was not performed in the cold rolling process of this comparative example.

[0150] Comparative Example 2 differs from Example 1 in that the intermediate annealing step four was not performed in the cold rolling process of this comparative example.

[0151] Comparative Example 3 differs from Example 1 in that the deformation amount of a single pass in the multi-pass cold rolling process of step three in this comparative example exceeds 15%, and the principle of "large at the beginning and small at the end, gradually decreasing" is not followed.

[0152] Comparative Example 4 differs from Example 1 in that the final heat treatment in step six was not performed in the cold rolling process of this comparative example.

[0153] The titanium alloy tubes prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests. The test items and test methods are as follows:

[0154] Tensile strength testing was conducted at room temperature using a universal testing machine to measure the maximum tensile strength.

[0155] Yield strength test, which determines the specified non-proportional elongation strength in a tensile test;

[0156] Elongation test: calculate the elongation at fracture after the tensile test;

[0157] Dimensional accuracy testing involves using an optical measuring instrument to measure the outer diameter and wall thickness non-uniformity of the pipe.

[0158] Surface quality testing was performed using eddy current testing and ultrasonic testing for non-destructive testing.

[0159] The test data of the titanium alloy tubes prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below:

[0160] Group Tensile strength (MPa) Yield strength (MPa) Elongation after fracture (%) Dimensional accuracy (outer diameter / wall thickness tolerance, mm) Surface quality (non-destructive testing results) Example 1 985 850 15 ±0.05 / ±0.03 Qualified, no defects Example 2 995 865 14 ±0.04 / ±0.02 Qualified, no defects Example 3 975 840 16 ±0.05 / ±0.03 Qualified, no defects Comparative Example 1 890 780 10 ±0.15 / ±0.08 Unacceptable, surface has scratches Comparative Example 2 1050 950 5 ±0.20 / ±0.10 Unqualified, contains microcracks Comparative Example 3 920 800 8 ±0.25 / ±0.15 Unacceptable, ellipticity out of tolerance Comparative Example 4 850 750 18 ±0.10 / ±0.05 It meets the requirements, but its strength is insufficient.

[0161] By comparing and analyzing the data in the table, it can be seen that the titanium alloy tubes prepared using the processes in Examples 1-3 have significantly better performance than those prepared using the processes in Comparative Examples 1-4. This indicates that the present invention improves the surface cleanliness and lubrication performance of the tube blank through pretreatment of the billet for cleaning, degreasing, and surface defect inspection, as well as surface coating treatment to apply a special polymer lubricating coating and cure it to form a continuous film. This reduces friction and surface damage during cold rolling, ensuring the integrity of the tube surface quality and smooth processing. By controlling the deformation amount and monitoring the rolling force through multi-pass cold rolling, combined with intermediate annealing to eliminate work hardening, and precision sizing and straightening to adjust dimensional accuracy and straightness, the processing process is stable and controllable, internal stress is released, tube deformation and cracks are avoided, and the forming consistency and geometric accuracy are improved. By adjusting the microstructure and properties through final heat treatment, and conducting non-destructive testing and dimensional measurement through cleaning and inspection, the mechanical properties and corrosion resistance of the tube are optimized. At the same time, it ensures timely detection of product defects and compliance with dimensional requirements, ensuring product quality reliability and extended service life.

[0162] By comparing and analyzing the relevant data in the table, it can be seen that the titanium alloy tubes prepared by the cold rolling process of the present invention have high mechanical properties, good dimensional accuracy and surface quality.

[0163] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0164] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A cold rolling process for titanium alloy tubing, characterized in that: Includes the following steps: Step 1: Billet pretreatment. Select titanium alloy tube billets and perform cleaning, degreasing, drying, and dimensional and surface defect inspection. Step 2: Surface coating treatment. A special polymer lubricating coating is applied to the inner and outer surfaces of the tube blank and cured at 80-120℃ for 10-30 minutes to form a continuous film. Step 3: Multi-pass cold rolling. The tube blank is subjected to multi-pass cold rolling with small deformation at room temperature. The total deformation and the deformation per pass are controlled, and the rolling force and dimensional changes are monitored. Step 4: Intermediate annealing, stress-relieving annealing at 550-650℃ under a protective atmosphere to eliminate work hardening; Step 5: Precision sizing and straightening. Perform 1-2 passes of precision cold rolling sizing, followed by straightening to ensure dimensional accuracy and straightness. Step Six: Final heat treatment, including solution treatment and aging treatment of the pipe to adjust its microstructure and properties; Step 7: Cleaning and inspection to remove residual coatings and oxides, followed by non-destructive testing and dimensional inspection; In step two, the special polymer lubricating coating is composed of the following raw materials in parts by weight: 60% solids content polytetrafluoroethylene dispersion: 30-50 parts; Ultra-high molecular weight polyethylene powder with a particle size of 1-5 μm: 10-20 parts; Nano-molybdenum disulfide: 5-10 parts; Silane coupling agent KH-550: 1-3 parts; Thickener, hydroxymethyl cellulose: 2-5 parts; Deionized water: 20-35 parts.

2. The cold rolling process for titanium alloy tubing according to claim 1, characterized in that: In step one, the titanium alloy tube blank is made of TC4 or TC11, with an outer diameter range of Φ50-150mm, a wall thickness range of 5-15mm, and a length-to-diameter ratio of less than 30. The pretreatment includes: first soaking and cleaning with alkaline degreasing solution at 50-70℃ for 10-20 minutes, then rinsing with deionized water, followed by dehydration with anhydrous ethanol, and finally drying in a circulating hot air drying oven at 60-80℃ for 30-60 minutes.

3. The cold rolling process for titanium alloy tubing according to claim 1, characterized in that: In step two, the special polymer lubricating coating is applied using a high-pressure airless spraying device, with the spraying pressure controlled at 8-15MPa, the wet film thickness of the coating being 50-100μm, and the dry film thickness being 15-30μm. The curing process is carried out in a circulating hot air oven, with the heating rate controlled at 2-5℃ / minute.

4. The cold rolling process for titanium alloy tubing according to claim 1, characterized in that: In step three, the deformation of the multi-pass cold rolling is carried out on a two-roll or three-roll cold rolling mill, and the total deformation is controlled within the range of 50%-75%. The deformation per pass is less than 15%, and the rolling speed is controlled at 20-60 meters per minute; During the cold rolling process, emulsion is used for cooling and auxiliary lubrication. The emulsion concentration is 3%-8%, the flow rate is 50-150L / min, and the inlet temperature is below 35℃.

5. The cold rolling process for titanium alloy tubing according to claim 4, characterized in that: The deformation amount of cold rolling passes follows the principle of "larger at the beginning and smaller at the end, gradually decreasing". The deformation amount of the first 3 passes is set at 12%-15%, the middle passes at 8%-12%, and the last 2-3 passes at 5%-8%. The emulsion is composed of the following components: 40-60% mineral oil base fluid, 10-15% nonionic surfactant, 3-5% rust inhibitor, 2-4% extreme pressure anti-wear agent, 0.1-0.5% defoamer, 0.5-1% bactericide, and the balance being deionized water.

6. The cold rolling process for titanium alloy tubing according to claim 1, characterized in that: In step four, stress-relief annealing is carried out under an argon protective atmosphere at a temperature of 550-650℃ and a holding time of 60-120 minutes. After cooling in the furnace to below 300℃, the furnace is removed and air-cooled. The oxygen content in the protective atmosphere furnace is controlled below 10ppm.

7. The cold rolling process for titanium alloy tubing according to claim 1, characterized in that: In step five, the deformation per pass of precision sizing is strictly controlled between 1% and 3%, and the rolling speed is kept stable at 10-20 meters per minute. The straightening process uses a six- or seven-roller straightening machine. The straightening force is adjusted according to the pipe specifications and yield strength. The straightness error of the pipe after straightening is less than 0.5 mm / m.

8. The cold rolling process for titanium alloy tubing according to claim 1, characterized in that: In step six, the solution treatment is carried out in a vacuum furnace or under the protection of high-purity argon gas. The solution temperature is 920-980℃ and the holding time is 30-60 minutes, followed by oil quenching or strong cooling with high-purity argon gas. The aging treatment is carried out in an air-circulating furnace at an aging temperature of 500-600℃ for 2-6 hours, followed by air cooling to room temperature.

9. The cold rolling process for titanium alloy tubing according to claim 1, characterized in that: The cleaning process in step seven employs a two-stage cleaning method: First, use a weak alkaline cleaning agent at 60-80℃ with a pH of 8-10 to spray and rinse for 5-10 minutes, then use deionized water for ultrasonic cleaning for 5-15 minutes. The non-destructive testing includes eddy current testing and ultrasonic testing, and the dimensional inspection includes the measurement of outer diameter, wall thickness, ellipticity, and wall thickness non-uniformity.

10. The cold rolling process for titanium alloy tubing according to claim 1, characterized in that: In the multi-pass cold rolling process of step three, after every 3-4 rolling passes, the billet is subjected to online dimensional measurement and shape correction. The measurement interval is controlled at 15-30 minutes. The correction is carried out by local fine adjustment of the roll gap, and the adjustment range is less than ±10% of the deformation amount set for the current pass. Furthermore, during the final heat treatment process in step six, the quenching transfer time after solution treatment is strictly controlled to be completed within 8-15 seconds.

Images