A method for improving the yield of titanium alloy seamless pipe

Abstract

The present invention discloses a method for improving the yield rate of titanium alloy seamless tubes. By optimizing the composition of the titanium alloy, the plasticity of the titanium alloy is improved. A titanium alloy bar with radial texture is obtained by switching between reversing upsetting and diagonal upsetting. The bar is machined to obtain a seamless tube blank. After glass lubrication, a new die extruder is used for extrusion. The arc of the extrusion die entrance follows the binary function formula Y=0.04X 2 +3X+A (A is a constant), an extrusion die outlet cone angle of 25° to 35°, an extrusion ratio of 10 to 18, and an extrusion speed of 90 to 120 mm / s. This method improves the uniformity of metal flow on the titanium alloy surface, avoids problems such as surface cracking during extrusion, and achieves low extrusion force, high flatness, high surface quality, minimal excess material, and a high yield rate. This comprehensive preparation method not only improves the surface quality and flatness of titanium alloy seamless pipes, but also significantly increases the yield rate of seamless pipes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy processing, and particularly relates to a method for improving the yield of titanium alloy seamless pipes. BACKGROUND

[0002] Titanium alloy seamless pipes have excellent mechanical properties and corrosion resistance, and have been widely applied in the fields of aerospace, ship power systems, seawater desalination heat exchangers, ship and offshore oil platform water and oil pipelines, and island municipal engineering pipe networks in recent years. The existing preparation processes of titanium alloy seamless pipes mainly include an extrusion process and a cross-rolling piercing-rolling process. Compared with the cross-rolling piercing process, the extrusion method is the earliest and most mature in China, but the titanium alloy has poor flowability due to its large friction coefficient in the extrusion process, so the extruded products are prone to breakage or cracking, resulting in a low yield of titanium alloy seamless pipes. SUMMARY

[0003] To solve the bottleneck problems existing in the prior art, the plasticity of titanium alloy is improved by optimizing the composition of the titanium alloy, the titanium alloy bar with radial texture is obtained by switching the upsetting and diagonal upsetting modes, the seamless pipe rough blank is obtained after machining the bar, the extrusion is performed by using a new type of die extruder after glass lubrication, the uniformity of the surface metal flow of the titanium alloy is improved, the problems such as surface cracking in the extrusion process are avoided, the extrusion force is small, the flatness is high, the surface quality is high, the excess material is small, and the yield is high. Through the above comprehensive preparation method, not only the flatness of the titanium alloy seamless pipe is improved, but also the yield of the seamless pipe is greatly improved.

[0004] To achieve the above-mentioned purposes, the application provides a method for improving the yield of titanium alloy seamless pipes, which comprises the following steps:

[0005] ①The raw materials are mixed and pressed into multiple electrode blocks, and the multiple electrode blocks are welded to obtain a consumable electrode, a transition element Cu is added, the mass content of the Cu element is 3% to 7%, and the plasticity of the alloy is improved by adding the transition element Cu.

[0006] ②The consumable electrode obtained in step 1 is melted 2 to 3 times by using a vacuum consumable arc furnace to obtain a titanium alloy ingot.

[0007] ③ The titanium alloy ingot obtained in step ② is kept at 880℃ to 1100℃ for 4 to 5 hours, and then subjected to six fires of upsetting and rounding to form titanium alloy bars. The upsetting adopts a switching mode of xyz reversing upsetting and diagonal reversing upsetting; the xyz reversing upsetting adopts three upsetting and three drawing, and the diagonal reversing upsetting adopts four upsetting and four drawing, with a deformation of 40% to 50% per fire. After the first fire of xyz reversing upsetting, the second fire is subjected to diagonal reversing upsetting, and so on. That is, each xyz reversing upsetting is replaced by diagonal reversing upsetting, and the two upsetting modes are operated alternately. The last fire is drawn and rounded into bars. This forging method can significantly improve the structural uniformity of the forged bars, reduce Cu element segregation, and improve the subsequent extrusion pass rate and surface quality.

[0008] ④ The bar obtained in step ③ is subjected to at least two heats of fine forging. The fine forging bar is annealed at an annealing temperature of [T-(120-200)]°C for 1-2 hours, where T is the phase transition temperature in °C. After annealing and straightening, the bar is subjected to lathing and drilling to obtain a titanium alloy seamless tube rough billet.

[0009] ⑤Heat the titanium alloy seamless pipe rough blank obtained in step ④ to a temperature of [T β -(50~80)]℃, where T β is the phase transition point temperature, in degrees Celsius; then glass lubricant is applied to the inner and outer surfaces of the tube.

[0010] ⑥ The lubricated seamless tube obtained in step ⑤ is extruded by a horizontal extruder. The arc of the extrusion die entrance follows the binary function formula Y = 0.04X 2 +3X+A (A is a constant), the extrusion die outlet cone angle is 25°~35°; the extrusion ratio is 10~18, and the extrusion speed is 90~120mm / s.

[0011] ⑦ The seamless pipe obtained in step ⑥ is vacuum annealed, straightened, pickled and then put into storage.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The present invention optimizes the composition of titanium alloys, improving their plasticity. A switching mode between reversing upsetting and diagonal upsetting is used to produce titanium alloy rods with radial textures. The rods are machined to produce seamless tube blanks, which are then lubricated with glass and extruded using a new die extruder. This improves the uniformity of metal flow on the titanium alloy surface and avoids problems such as surface cracking during extrusion. The process results in low extrusion force, high straightness, high surface quality, minimal excess material, and a high yield rate. This comprehensive preparation method not only improves the surface quality and straightness of titanium alloy seamless tubes, but also significantly increases the yield rate of seamless tubes. DETAILED DESCRIPTION

[0014] The present invention will be further described below with reference to specific examples, but the present invention is not limited in any way. To avoid redundancy, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0015] Example 1

[0016] A method for improving the yield rate of titanium alloy seamless pipes, producing TA18 titanium alloy seamless pipes with a specification of Φ48×12mm, the specific process is as follows:

[0017] ① The raw materials are mixed to press a plurality of electrode blocks, and the plurality of electrode blocks are welded to obtain a consumable electrode, and a transition element Cu is added; the mass content of the Cu element is 3%.

[0018] ② The consumable electrode obtained in step ① is melted twice in a vacuum consumable arc furnace to obtain a titanium alloy ingot; the ingot specification is Φ550mm.

[0019] ③ The titanium alloy ingot obtained in step ② is kept at 880℃ for 5h, and is subjected to 6 fire upsetting and rounding to form a titanium alloy bar (machining). The upsetting adopts the switching mode of xyz reversing upsetting and diagonal reversing upsetting; odd-numbered fire reversing upsetting (three upsetting and three drawing) → even-numbered fire diagonal upsetting (four upsetting and four drawing), and the last fire (sixth fire) upsetting forging (drawing and lengthening and rounding).

[0020] ④ The bar obtained in step ③ is subjected to no less than two rounds of fine forging. The fine forged bar (Φ150mm bar) is annealed (750℃ / 2h), and after annealing and straightening, it is polished and drilled to Φ130*Φ30mm to obtain a titanium alloy seamless pipe rough blank.

[0021] ⑤Heat the titanium alloy seamless pipe rough blank obtained in step ④ to a temperature of [T β -(50~80)]℃, where T β is the phase transition point temperature; then apply glass lubricant on the inner and outer surfaces of the tube.

[0022] ⑥ The lubricated seamless tube obtained in step ⑤ was extruded using a horizontal extruder with an extrusion force of 20 N, an extrusion ratio of 12.5, and an extrusion speed of 100 mm / s to obtain a Φ48×12 mm seamless tube.

[0023] ⑦ The seamless pipe obtained in step ⑥ is vacuum annealed, straightened, pickled and then stored; the annealing temperature is 700°C and the holding time is 2h.

[0024] The TA18 titanium alloy seamless tube prepared in Example 1 has a smooth outer surface, a straightness of 4 mm / m, and a yield rate of 97%.

[0025] Example 2

[0026] A method for improving the yield rate of titanium alloy seamless pipes, producing TA18 titanium alloy seamless pipes with a specification of Φ48×12mm, the specific process is as follows:

[0027] ① The raw materials are mixed to press a plurality of electrode blocks, and the plurality of electrode blocks are welded to obtain a consumable electrode, and a transition element Cu is added; the mass content of the Cu element is 7%.

[0028] ② The consumable electrode obtained in step ① is melted three times in a vacuum consumable arc furnace to obtain a titanium alloy ingot; the ingot specification is Φ550mm.

[0029] ③ The titanium alloy ingot obtained in step ② is kept at 1100℃ for 4h, and is subjected to 6 fire upsetting and rounding to form a titanium alloy bar (machining). The upsetting adopts the switching mode of xyz reversing upsetting and diagonal reversing upsetting; odd-numbered fire reversing upsetting (three upsetting and three drawing) → even-numbered fire diagonal upsetting (four upsetting and four drawing), and the last fire (sixth fire) upsetting forging (drawing and lengthening and rounding).

[0030] ④ The bar obtained in step ③ is subjected to no less than two rounds of fine forging. The fine forged bar (Φ150mm bar) is annealed (750℃ / 2h), and after annealing and straightening, it is polished and drilled to Φ130*Φ30mm to obtain a titanium alloy seamless pipe rough blank.

[0031] ⑤Heat the titanium alloy seamless pipe rough blank obtained in step ④ to a temperature of [T β -(50~80)]℃, where T β is the phase transition point temperature; then apply glass lubricant on the inner and outer surfaces of the tube.

[0032] ⑥ The lubricated seamless tube obtained in step ⑤ was extruded using a horizontal extruder with an extrusion force of 18 N, an extrusion ratio of 12.5, and an extrusion speed of 100 mm / s to obtain a Φ48×12 mm seamless tube.

[0033] ⑦ The seamless pipe obtained in step ⑥ is vacuum annealed, straightened, pickled and then stored; the annealing temperature is 700°C and the holding time is 2h.

[0034] The TA18 titanium alloy seamless tube prepared in Example 2 has a smooth outer surface, a straightness of 3 mm / m, and a yield rate of 98%.

[0035] Anyone skilled in the art will be able to utilize the above-disclosed technical content to make many possible changes and modifications to the technical solution of the present invention, or to modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention that do not depart from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for improving the yield rate of titanium alloy seamless pipes, characterized in that: The method comprises the following steps: ① The raw materials are mixed and pressed into a plurality of electrode blocks, and the plurality of electrode blocks are welded to obtain a consumable electrode, and a transition element Cu is added; the mass content of the Cu element is 3% to 7%; ② The consumable electrode obtained in step ① is melted 2 to 3 times in a vacuum consumable arc furnace to obtain a titanium alloy ingot; ③ The titanium alloy ingot obtained in step ② is kept at 880°C to 1100°C for 4 to 5 hours, and is subjected to 6 rounds of upsetting and rounding to form a titanium alloy bar. The upsetting adopts a switching mode of xyz reversing upsetting and diagonal reversing upsetting; The xyz reversing upsetting and drawing adopts three upsetting and three drawing, and the diagonal reversing upsetting and drawing adopts four upsetting and four drawing, and the deformation amount of each fire is 40% to 50%; The two upsetting modes are operated alternately, and each time the xyz reversing upsetting is replaced by the diagonal reversing upsetting; ④ The bar obtained in step ③ is subjected to at least two rounds of fine forging, the fine forged bar is annealed, and after annealing and straightening, it is subjected to lathing and drilling to obtain a titanium alloy seamless tube rough blank; The annealing temperature is [T-(120-200)]°C, and the holding time is 1-2h, wherein T is the phase transition point temperature; ⑤Heat the titanium alloy seamless pipe rough blank obtained in step ④ to a temperature of T β -(50~80)℃, where T β is the phase transition point temperature; then the glass lubricant is applied to the inner and outer surfaces of the tube; ⑥ The lubricated seamless tube obtained in step ⑤ is extruded by a horizontal extruder. The arc of the extrusion die entrance follows the binary function formula Y = 0.04X 2 +3X+A, extrusion die outlet cone angle 25°~35°; extrusion ratio 10~18, extrusion speed 90~120mm / s; ⑦ The seamless pipe obtained in step ⑥ is vacuum annealed, straightened, pickled and then put into storage.