Manufacturing method of TA24 titanium alloy cold-rolled pipe for ships and warships

Abstract

The invention discloses a manufacturing method of a TA24 titanium alloy cold-rolled pipe for a ship. The method comprises the following steps: 1, forging a TA24 titanium alloy cast ingot to prepare a bar billet; 2, after drilling the bar billet, performing hot extrusion on the bar billet in a sheath to obtain an extruded tube billet; 3, shaping and rolling the extruded tube blank, and performing inner and outer surface treatment and heat treatment to obtain a rolled tube blank; fourthly, cold rolling, middle-pass heat treatment, inner surface sand blasting treatment and acid pickling treatment are conducted; 5, performing cold rolling to obtain a finished-size pipe; and 6, carrying out heat treatment, straightening and ultrasonic flaw detection on a finished product to obtain the TA24 titanium alloy cold-rolled pipe. By strictly controlling the chemical components of the bar blank, the extrusion and cold rolling process, the heat treatment system and the surface treatment, the problems of cracks and cracking in cold rolling machining are solved, the smooth proceeding of the cold rolling process is ensured, the TA24 titanium alloy cold-rolled pipe with excellent mechanical properties and stable surface quality is prepared, the use requirements of ships and warships are met, the quality is stable, and the production cost is low. The method is high in operability and suitable for popularization.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material processing, and in particular relates to a method for manufacturing a TA24 titanium alloy cold-rolled tube for ships. Background Art

[0002] TA24 (also known as Ti75) is a near-α-type titanium alloy with a nominal chemical composition of Ti-3Al-2Mo-2Zr. It is the first 730MPa-grade marine titanium alloy independently developed in my country. It has the characteristics of medium strength, high toughness, corrosion resistance, hydrogen embrittlement resistance, and weldability. Its comprehensive performance is superior to the same-level marine titanium alloys at home and abroad, and it has broad application prospects in the fields of shipbuilding, petroleum, and chemical industry. In the field of ships, TA24 is used in power plant equipment, ship welding structural parts, reciprocating salt water pumps, sea-going systems, seawater four-way, pipes and side double seats, double ball valve stems, etc., and is actually used in a submarine secondary circuit system.

[0003] The smelting, forging, bar and plate processing technologies of TA24 titanium alloy have become mature, and the demand for tubes and pipes has gradually increased. At present, there are many domestic studies and literatures on forging and bars of TA24 titanium alloy, but there are few literatures on tube manufacturing technology, and all of them are hot processing, and there are almost no cold-rolled tubes. This is because TA24 titanium alloy has high strength and poor cold processing performance, and it is difficult to process tubes through cold rolling.

[0004] At present, the main production methods of TA24 titanium alloy pipes are hot extrusion, forged bar drilling, and oblique rolling and piercing. All three methods are hot processing for tube blanks and then machining to finished product size, and each has its own limitations. The rod drilling method can machine most of the outer diameters and wall thicknesses of the pipes and has good performance, but the pipe length is short, the yield rate is low, and the cost is high; the TA24 pipes produced by the extrusion method have good performance, but the production of longer and thin-walled pipes is difficult and the cost is high; the oblique rolling and piercing method is easy and low in cost, but it can only produce pipes with larger outer diameters (generally outer diameter ≥ 70mm) and thicker walls, and the performance is not easy to control, the machining is difficult, and the surface quality is poor.

[0005] Therefore, it is necessary to develop a cold rolling manufacturing process for TA24 titanium alloy tubes to obtain TA24 titanium alloy tubes with excellent mechanical properties and qualified length, and the process is relatively simple and low in cost. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a manufacturing method for cold-rolled TA24 titanium alloy tubes for ships in view of the deficiencies of the above-mentioned prior art. By limiting the chemical composition and metallographic structure of the billet, the good plastic processing performance of the billet is ensured. Combining the preparation of the billet by envelope extrusion limiting, an extrusion tube blank with good performance is obtained. Then, the tube blank is cold-rolled and the process parameters of cold rolling and the post-rolling heat treatment system are strictly controlled, ensuring the smooth progress of the cold rolling process, and preparing cold-rolled TA24 titanium alloy tubes with excellent mechanical properties and stable surface quality, solving the problems of great difficulty in cold processing of cold-rolled TA24 titanium alloy tubes, easy occurrence of surface cracks and even easy cracking during the processing process.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is: a manufacturing method for cold-rolled TA24 titanium alloy tubes for ships, characterized in that the method comprises the following steps:

[0008] Step 1: Select a TA24 titanium alloy ingot obtained by three times of vacuum arc furnace melting as raw material for forging to prepare a billet; the chemical composition of the billet meets the requirements of the standard of GB / T3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Compositions", and the metallographic structure is an equiaxed plus elongated processing structure without original β grain boundaries;

[0009] Step 2: Drill the billet prepared in Step 1 first, then envelope it, and use an extruder to extrude it after heating and insulation to prepare an extrusion tube blank;

[0010] Step 3: Use a tube rolling mill to shape and roll the extrusion tube blank obtained in Step 2, then perform internal and external surface treatments to remove surface defects, and then perform heat treatment to obtain a rolled tube blank;

[0011] Step 4: Cold-roll the rolled tube blank obtained in Step 3 using an LG type two-high rolling mill or an LD type multi-high rolling mill, and perform intermediate pass heat treatment. Perform internal surface sandblasting treatment and pickling treatment on the rolled tube blank after heat treatment to remove internal wall defects to obtain a semi-finished tube blank;

[0012] Step 5: Cold-roll the semi-finished tube blank obtained in Step 4 using an LG type two-high rolling mill or an LD type multi-high rolling mill to obtain a finished size tube;

[0013] Step 6: Perform finished product heat treatment on the finished size tube obtained in Step 5, and then perform straightening and ultrasonic flaw detection to obtain cold-rolled TA24 titanium alloy tubes.

[0014] The manufacturing method of the above-mentioned TA24 titanium alloy cold-rolled tube for ships is characterized in that the elemental composition and mass content of the billet in Step 1 meet the standard requirements of GB / T3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Compositions", and the mass content of oxygen element is controlled to be 0.07% - 0.11%. By limiting the oxygen element content in the billet, it is avoided that the strength of the produced tube does not meet the standard requirements due to too low oxygen element content, and at the same time, it is avoided that too high oxygen element content leads to easy cracking during subsequent rolling and a reduction in the flaw detection qualification rate.

[0015] The manufacturing method of the above-mentioned TA24 titanium alloy cold-rolled tube for ships is characterized in that the sleeve in Step 2 adopts a double-sleeve form of inner steel skin and outer copper skin. Among them, the steel skin is made of soft steel with a thickness of 0.5 mm - 0.8 mm, and the copper skin is made of red copper with a thickness of 0.7 mm - 1.2 mm. The heating temperature is (T β - 30) °C - (T β - 80) °C, where T β is the phase transformation point temperature, with the unit of °C. The extruder is a 20MN - 45MN horizontal extruder, and the extrusion ratio used in extrusion is 5 - 15.

[0016] The manufacturing method of the above-mentioned TA24 titanium alloy cold-rolled tube for ships is characterized in that the deformation amount of the sizing rolling in Step 3 does not exceed 35%. The method for inner and outer surface treatment is as follows: Use a boring machine or a lathe to bore the inner hole of the tube blank after sizing rolling unilaterally by 0.4 mm - 0.7 mm, and use a centerless lathe, a grinding machine or a planer to turn or grind the outer surface of the tube blank after sizing rolling to remove the defects completely. The present invention adopts small-deformation sizing rolling combined with surface treatment to remove the inner and outer surface defects of the extruded tube blank completely, avoiding the phenomenon that local defects of the rolled tube blank cannot be completely removed only by surface treatment and the defects expand during subsequent cold rolling.

[0017] The manufacturing method of the above-mentioned TA24 titanium alloy cold-rolled tube for ships is characterized in that the deformation amount of the cold rolling in Step 4 is 25% - 55%, the vehicle speed does not exceed 60 times / min, and the rolling feed amount does not exceed 4 mm / time. Based on the characteristics of TA24 titanium alloy, the present invention controls the rolling parameters of cold rolling to avoid cracking of the finished size tube due to too large deformation amount, and at the same time, avoids uneven deformation and inability to break the structure due to too small deformation amount.

[0018] The manufacturing method of the above-mentioned TA24 titanium alloy cold-rolled tube for ships is characterized in that the heat treatments in Step 3 and Step 4 are both vacuum annealing, and the holding temperature of the vacuum annealing is 600 °C - 800 °C. Among them, when the cumulative cold rolling deformation amount before vacuum annealing is greater than 30%, the holding temperature is 700 °C - 800 °C, and when the cumulative cold rolling deformation amount does not exceed 30%, the holding temperature is 600 °C - 690 °C.

[0019] The manufacturing method of the above-mentioned TA24 titanium alloy cold-rolled tube for ships is characterized in that in step four, the internal surface sandblasting treatment uses sand grains with a mesh size of 50 to 100 meshes, the air pressure is 0.5 MPa to 1.0 MPa, and the sandblasting time is not less than 2 minutes, based on the uniformity of the internal surface, no visible horizontal and vertical micro-cracks and other defects to the naked eye. The sandblasting process is used to remove the defects on the internal surface of the semi-finished tube blank, and improve the flaw detection qualification rate of the TA24 titanium alloy cold-rolled tube product.

[0020] The manufacturing method of the above-mentioned TA24 titanium alloy cold-rolled tube for ships is characterized in that in step five, the deformation amount of the cold rolling is 30% to 50%, the vehicle speed does not exceed 50 times / min, and the rolling feed amount does not exceed 3 mm / time. Based on the characteristics of TA24 titanium alloy, the present invention controls the rolling parameters of cold rolling, avoids cracking of the semi-finished tube blank caused by excessive deformation amount, and at the same time avoids uneven deformation and inability to break the structure due to too small deformation amount.

[0021] The manufacturing method of the above-mentioned TA24 titanium alloy cold-rolled tube for ships is characterized in that in step six, the finished product heat treatment is vacuum annealing, and the holding temperature of the vacuum annealing is 650 °C to 780 °C. The straightening uses a multi-roll straightening machine with more than six rolls, and the straightening method is cold straightening or warm straightening, and the warm straightening temperature is 300 °C to 520 °C.

[0022] The present invention has the following advantages compared with the prior art:

[0023] 1. By limiting the chemical composition and metallographic structure of the bar blank prepared from the raw material TA24 titanium alloy ingot, the present invention ensures that the bar blank has good plastic processing performance. Combining the extrusion of the bar blank with a sheath and limiting the process parameters, an extrusion tube blank with good performance is prepared. Then, cold rolling is carried out on the tube blank, and the process parameters of cold rolling including deformation amount, vehicle speed, feed amount and post-rolling heat treatment system are strictly controlled, ensuring the smooth progress of the cold rolling process, effectively solving the defects of difficult cold processing of TA24 titanium alloy cold-rolled tubes, easy appearance of surface cracks and even easy cracking during the processing process, avoiding problems such as unqualified performance detection of finished tubes and low flaw detection qualification rate, and preparing TA24 titanium alloy cold-rolled tubes with excellent mechanical properties and stable surface quality, meeting the requirements of ship use.

[0024] 2. The present invention uses the cold rolling processing method to manufacture TA24 titanium alloy cold-rolled tubes. By controlling the cold rolling process parameters for large deformation to break grains, and combining with post-rolling heat treatment, the structure of the TA24 titanium alloy cold-rolled tubes is fine and uniform, and its mechanical properties are more excellent and stable.

[0025] 3. The present invention performs sandblasting and pickling treatment on the inner surface of the rolled tube blank to remove inner surface defects generated during the processing, thereby improving the surface quality of the TA24 titanium alloy cold-rolled tube, thereby improving the ultrasonic flaw detection pass rate of the finished TA24 titanium alloy cold-rolled tube.

[0026] 4. Compared with the existing process of machining thin-walled pipes after hot processing, which is difficult to machine and most of the materials are turned into chips with huge loss, the present invention directly adopts cold rolling process to the finished pipe size, with high dimensional accuracy and no need for a lot of turning, which greatly improves the yield rate and reduces costs. At the same time, the manufacturing method of the present invention is simple, does not require special equipment, has low manufacturing cost, and is easy to realize industrial production.

[0027] 5. Compared with the existing hot processing method which is limited by the problem of finished product size, the present invention adopts a cold rolling production method to prepare TA24 titanium alloy cold-rolled pipes with an outer diameter of 6mm to 114mm, a wall thickness of 1mm to 10mm, and a length of 3m to 10m, which greatly expands the production specification range of TA24 titanium alloy cold-rolled pipes and broadens their application fields.

[0028] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0029] Example 1

[0030] This embodiment includes the following steps:

[0031] Step 1, selecting a TA24 titanium alloy ingot obtained by three vacuum arc furnace smelting as a raw material for forging to prepare a rod blank with a diameter of Φ178 mm; the chemical composition of the rod blank, i.e., the element composition and mass content, meet the requirements of GB / T3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Compositions" standard, wherein the mass content of oxygen element is 0.10% to 0.11%, the phase transition point is 945°C to 950°C, the metallographic structure is an equiaxed and elongated processed structure, and there is no original β grain boundary;

[0032] Step 2: Drill holes in the bar blank prepared in step 1, and then cover it. The cover adopts a double cover form of inner steel skin and outer copper skin, wherein the steel skin is made of mild steel with a thickness of 0.7mm-0.8mm, and the copper skin is made of red copper with a thickness of 1.0mm-1.2mm, to obtain a cover body, heat the cover body to 900℃±15℃, and extrude it using a 25MN horizontal extruder, using an extrusion ratio of 14-15, to prepare a size (outer diameter×wall thickness) Φ68 ±2 mm×9 ±1 mm extrusion tube billet;

[0033] Step 3: Shape and roll the extruded tube blank obtained in Step 2 using a tube rolling mill with a deformation rate of 18% - 20%. Then, perform internal and external surface treatments. Use a boring machine or a lathe to bore the inner hole of the shaped and rolled tube blank unilaterally by 0.4 mm - 0.5 mm. Use a centerless lathe, a grinding machine, or a planer to turn or grind the outer surface of the shaped and rolled tube blank to completely remove the defects. Then, perform vacuum annealing at a holding temperature of 620°C ± 15°C to obtain a rolled tube blank.

[0034] Step 4: Cold roll the rolled tube blank obtained in Step 3 using an LG60 rolling mill for 4 passes. The cold rolling deformation rate is 27% - 52%, the vehicle speed is 20 times / min - 60 times / min, and the rolling feed is 2 mm / pass - 4 mm / pass. Perform vacuum annealing after each pass of cold rolling. When the cumulative cold rolling deformation rate before vacuum annealing is greater than 30%, the holding temperature is 700°C - 780°C; when the cumulative cold rolling deformation rate does not exceed 30%, the holding temperature is 600°C - 680°C. Perform internal surface sandblasting on the rolled tube blank after vacuum annealing. Use sand grains of 50 - 100 mesh, with an air pressure of 0.5 MPa - 1.0 MPa, and the sandblasting time at each end is not less than 2 minutes. After sandblasting, the internal surface is uniform, without visible transverse and longitudinal microcracks and other defects. After sandblasting, use a mixed acid solution of HF, HNO 3 and water for pickling treatment to remove internal wall defects and obtain a semi-finished tube blank.

[0035] Step 5: Cold roll the semi-finished tube blank obtained in Step 4 using an LD40 multi-roll rolling mill. The cold rolling deformation rate is 32% - 34%, the vehicle speed is 30 times / min - 50 times / min, and the rolling feed is 2 mm / pass - 3 mm / pass to obtain a finished size tube with an outer diameter × wall thickness × length of Φ36 mm × 2 mm × 10000 mm.

[0036] Step 6: Perform finished heat treatment on the finished size tube obtained in Step 5. Use a vacuum furnace for vacuum annealing, and the holding temperature of the vacuum annealing is 760°C ± 10°C. Then, perform cold straightening using a seven-roll straightening machine. After straightening, the straightness meets the usage requirements, and perform ultrasonic flaw detection. The standard flaw meets: depth 0.2 mm × width 0.8 mm × length 25 mm, the flaw detection qualification rate exceeds 80%, and the length of a single tube is greater than 9 m to obtain TA24 titanium alloy cold-rolled tubes.

[0037] After testing, the measured properties of the TA24 titanium alloy cold-rolled tubes prepared in this example are: tensile strength Rm = 790 MPa - 800 MPa, yield strength Rp 0.2 = 665 MPa - 690 MPa, elongation after fracture A = 20% - 22%, fully meeting the performance requirements of the standard specifications: tensile strength Rm ≥ 730 MPa, yield strength Rp 0.2≥580 MPa, elongation after fracture A ≥ 13%.

[0038] Example 2

[0039] This example includes the following steps:

[0040] Step 1: Select a TA24 titanium alloy ingot obtained by three times of vacuum arc furnace melting as the raw material for forging to prepare a billet with a diameter of Φ213 mm; the chemical composition of the billet, that is, the element composition and mass content, meets the requirements of the standard GB / T3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Compositions", where the mass content of oxygen element is 0.07% - 0.08%, the phase transformation point is 935 °C - 940 °C, the metallographic structure is equiaxed plus elongated processed structure, and there is no original β grain boundary;

[0041] Step 2: Drill the billet prepared in Step 1 first, and then sleeve it. The sleeve adopts a double-sleeve form of inner steel skin and outer copper skin. The steel skin uses soft steel with a thickness of 0.5 mm - 0.6 mm, and the copper skin uses red copper with a thickness of 0.7 mm - 0.8 mm to obtain a sleeve body. Heat the sleeve body to 870 °C ± 15 °C and then use a 40 MN horizontal extrusion press for extrusion. The extrusion ratio used is 5 - 6 to prepare an extruded tube blank with dimensions (outer diameter × wall thickness) of Φ130 ±2 mm × 15 ±1 mm.

[0042] Step 3: Use an LG150 two-high rolling mill to shape and roll the extruded tube blank obtained in Step 2, with a deformation amount of 22% - 25%. Then, perform internal and external surface treatment. Use a boring machine or a lathe to bore the inner hole of the shaped and rolled tube blank unilaterally by 0.5 mm - 0.6 mm, and use a centerless lathe, grinder or planer to turn or grind the outer surface of the shaped and rolled tube blank to remove the defects completely. Then, perform vacuum annealing with a holding temperature of 650 °C ± 15 °C to obtain a rolled tube blank;

[0043] Step 4: Use an LG150 rolling mill and an LG60 rolling mill to perform two-pass cold rolling on the rolled tube blank obtained in Step 3. The deformation amounts of cold rolling are 35% and 53% respectively, the vehicle speed is 40 times / min - 60 times / min, the rolling feed is 2 mm / time - 4 mm / time. After each pass of cold rolling, perform vacuum annealing, and the holding temperatures are 700 °C ± 15 °C and 760 °C ± 15 °C respectively. Perform internal surface sandblasting treatment on the rolled tube blank after vacuum annealing. Use 50 - 100 mesh sand grains, the air pressure is 0.5 MPa - 1.0 MPa, and the sandblasting time at each end is not less than 2 min. After sandblasting, the internal surface is uniform, without visible transverse and longitudinal micro-cracks and other defects to the naked eye. After sandblasting, use a mixed acid solution of HF, HNO 3 and water for pickling treatment to remove the inner wall defects and obtain a semi-finished tube blank;

[0044] Step 5: Cold roll the semi-finished tube blank obtained in Step 4 using an LG60 two-high rolling mill. The cold rolling deformation is 48%, the vehicle speed is 30 times / min to 40 times / min, and the rolling feed is 1 mm / time to 2 mm / time, to obtain a finished size tube with an outer diameter × wall thickness × length of Φ76 mm × 3.5 mm × 8000 mm;

[0045] Step 6: Perform finish heat treatment on the finished size tube obtained in Step 5. Use a vacuum furnace for vacuum annealing, and the holding temperature for vacuum annealing is 740 °C ± 10 °C. Then use a multi-roll straightening machine for warm straightening, and the warm straightening temperature is 300 °C to 520 °C. The straightness after straightening meets the use requirements, and ultrasonic flaw detection is performed. The standard flaw meets: depth 0.35 mm × width 0.8 mm × length 25 mm, the flaw detection qualification rate exceeds 80%, and the length of a single tube is greater than 6 m, to obtain TA24 titanium alloy cold-rolled tubes.

[0046] After testing, the measured properties of the TA24 titanium alloy cold-rolled tubes prepared in this example are: tensile strength Rm = 800 MPa to 820 MPa, yield strength Rp 0.2 = 650 MPa to 670 MPa, elongation after fracture A = 21% to 22%, fully meeting the performance requirements of the standard specifications: tensile strength Rm ≥ 730 MPa, yield strength Rp 0.2 ≥ 580 MPa, elongation after fracture A ≥ 13%.

[0047] Example 3

[0048] This example includes the following steps:

[0049] Step 1: Select a TA24 titanium alloy ingot obtained by three times of vacuum arc furnace melting as the raw material for forging to prepare a bar blank with a diameter of Φ273 mm; the chemical composition of the bar blank, that is, the element composition and mass content, meets the standard requirements of GB / T3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Compositions", in which the mass content of oxygen element is 0.08% to 0.10%, the phase transformation point is 940 °C to 945 °C, the metallographic structure is equiaxed plus elongated processed structure, and there is no original β grain boundary;

[0050] Step 2: First drill the bar blank prepared in Step 1, and then perform cladding. The cladding adopts a double-cladding form of inner steel skin and outer copper skin. The steel skin uses soft steel with a thickness of 0.5 mm to 0.6 mm, and the copper skin uses red copper with a thickness of 0.7 mm to 0.8 mm, to obtain a cladding body. Heat the cladding body to 880 °C and then use a 45MN to 63MN horizontal extrusion press for extrusion. The extrusion ratio used is 7 to 8, to prepare an extruded tube blank with a size (outer diameter × wall thickness) of Φ152 ±2 mm × 16 ±1 mm;

[0051] Step 3: Shape and roll the extruded tube blank obtained in Step 2 using an LG150 two-high rolling mill with a deformation of 32% - 34%. Then, perform internal and external surface treatment. Use a boring machine or a lathe to bore the inner hole of the tube blank after shape rolling unilaterally by 0.6 mm - 0.7 mm. Use a centerless lathe, a grinding machine, or a planer to turn or grind the outer surface of the tube blank after shape rolling to remove the defects completely. Then, perform vacuum annealing at a holding temperature of 720°C ± 15°C to obtain a rolled tube blank;

[0052] Step 4: Perform one-pass cold rolling on the rolled tube blank obtained in Step 3 using an LG150 two-high rolling mill. The deformation of cold rolling is 40% - 43%, the vehicle speed is 40 times / min - 50 times / min, and the rolling feed is 2 mm / time - 3 mm / time. After cold rolling, perform vacuum annealing at a holding temperature of 750°C ± 15°C. Perform internal surface sandblasting on the rolled tube blank after vacuum annealing. Use sand grains of 50 - 100 mesh, with an air pressure of 0.5 MPa - 1.0 MPa, and the sandblasting time for each end is not less than 2 min. After sandblasting, the internal surface is uniform, without visible transverse and longitudinal micro-cracks and other defects. After sandblasting, use a mixed acid solution of HF, HNO 3 and water for pickling treatment to remove the inner wall defects and obtain a semi-finished tube blank;

[0053] Step 5: Perform cold rolling on the semi-finished tube blank obtained in Step 4 using an LG150 two-high rolling mill. The deformation of cold rolling is 38%, the vehicle speed is 30 times / min - 40 times / min, and the rolling feed is 2 mm / time - 3 mm / time to obtain a finished size tube with an outer diameter × wall thickness × length of Φ108 mm × 4.5 mm × 7000 mm;

[0054] Step 6: Perform finished heat treatment on the finished size tube obtained in Step 5. Use a vacuum furnace for vacuum annealing, and the holding temperature of vacuum annealing is 680°C ± 10°C. Then, use a multi-roll straightening machine for warm straightening, and the warm straightening temperature is 300°C - 520°C. After straightening, the straightness meets the use requirements, and perform ultrasonic flaw detection. The standard flaw meets: depth 0.45 mm × width 0.8 mm × length 25 mm, the flaw detection qualification rate exceeds 70%, and the length of a single tube is greater than 6 m to obtain TA24 titanium alloy cold-rolled tubes.

[0055] After testing, the measured properties of the TA24 titanium alloy cold-rolled tubes prepared in this example are: tensile strength Rm = 790 MPa - 820 MPa, yield strength Rp 0.2 = 640 MPa - 660 MPa, elongation after fracture A = 15% - 17%, fully meeting the performance requirements of the standard specifications: tensile strength Rm ≥ 730 MPa, yield strength Rp 0.2≥580 MPa, elongation after fracture A ≥ 13%.

[0056] As mentioned above, it is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for manufacturing TA24 titanium alloy cold-rolled tube for ships, characterized in that: The method comprises the following steps: Step 1: Select the TA24 titanium alloy ingot obtained by three vacuum arc furnace smelting as the raw material for forging to prepare a rod blank; the chemical composition of the rod blank meets the requirements of GB / T3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Compositions" standard, and the metallographic structure is an equiaxed and elongated processed structure without original β grain boundaries; Step 2: drilling holes in the rod blank prepared in step 1, then covering it, and extruding it using an extruder after heating and heat preservation to prepare an extruded tube blank; Step 3: The extruded tube obtained in step 2 is shaped and rolled using a tube rolling mill, and then the inner and outer surfaces are treated to remove surface defects, and then heat treated to obtain a rolled tube; Step 4: cold rolling the rolled tube obtained in step 3 using an LG two-roll mill or an LD multi-roll mill, and performing intermediate heat treatment, and performing inner surface sandblasting and pickling treatment on the rolled tube after heat treatment to remove inner wall defects to obtain a semi-finished tube; Step 5: cold rolling the semi-finished tube obtained in step 4 using an LG two-roll mill or an LD multi-roll mill to obtain a finished size tube; Step 6: The finished size pipe obtained in step 5 is subjected to finished heat treatment, and then straightened and ultrasonically inspected to obtain a TA24 titanium alloy cold-rolled pipe.

2. The method for manufacturing a TA24 titanium alloy cold-rolled tube for ships according to claim 1, characterized in that: The element composition and mass content of the rod blank described in step 1 meet the requirements of GB / T3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Compositions" standard, and the mass content of oxygen element is controlled to be 0.07% to 0.11%.

3. The method for manufacturing a TA24 titanium alloy cold-rolled tube for ships according to claim 1, characterized in that: In step 2, the sheath is a double sheath with inner steel and outer copper, wherein the steel is made of mild steel with a thickness of 0.5 mm to 0.8 mm, and the copper is made of red copper with a thickness of 0.7 mm to 1.2 mm. The heating temperature is (T β -30)℃~(T β -80)℃, where T β is the phase transition point temperature, in degrees Celsius; the extruder is a 20MN-45MN horizontal extruder, and the extrusion ratio used in the extrusion is 5-15.

4. The method for manufacturing a TA24 titanium alloy cold-rolled tube for ships according to claim 1, characterized in that: The deformation amount of the shaping rolling in step three does not exceed 35%, and the method of the inner and outer surface treatment is: using a boring machine or a lathe to bore a single-side hole of 0.4mm to 0.7mm on the inner hole of the tube blank after shaping rolling, and using a centerless lathe, a grinder or a planer to turn or grind the outer surface of the tube blank after shaping rolling to remove defects.

5. The method for manufacturing a TA24 titanium alloy cold-rolled tube for ships according to claim 1, characterized in that: The deformation amount of the cold rolling in step 4 is 25% to 55%, the vehicle speed does not exceed 60 times / min, and the rolling feed amount does not exceed 4 mm / time.

6. The method for manufacturing a TA24 titanium alloy cold-rolled tube for ships according to claim 1, characterized in that: The heat treatment in step three and step four is vacuum annealing, and the holding temperature of vacuum annealing is 600°C to 800°C, wherein the holding temperature is 700°C to 800°C when the cumulative cold rolling deformation before vacuum annealing is greater than 30%, and the holding temperature is 600°C to 690°C when the cumulative cold rolling deformation does not exceed 30%.

7. The method for manufacturing a TA24 titanium alloy cold-rolled tube for ships according to claim 1, characterized in that: The inner surface sandblasting treatment described in step 4 uses 50-100 mesh sand particles, an air pressure of 0.5MPa-1.0MPa, and a sandblasting time of not less than 2 minutes, with the inner surface being uniform and free of visible horizontal and vertical microcracks and other defects.

8. The method for manufacturing a TA24 titanium alloy cold-rolled tube for ships according to claim 1, characterized in that: The cold rolling deformation in step 5 is 30% to 50%, the vehicle speed does not exceed 50 times / min, and the rolling feed amount does not exceed 3mm / time.

9. The method for manufacturing a TA24 titanium alloy cold-rolled tube for ships according to claim 1, characterized in that: The finished product heat treatment in step six is ​​vacuum annealing, and the insulation temperature of vacuum annealing is 650°C to 780°C. Straightening uses a multi-roll straightening machine with more than six rollers. The straightening method is cold straightening or warm straightening, and the warm straightening temperature is 300°C to 520°C.