A rolling method to significantly reduce defects in TA18 alloy tubes

Abstract

This invention discloses a rolling method for significantly reducing defects in TA18 alloy tubes, belonging to the field of titanium alloy processing technology. The rolling method for significantly reducing defects in TA18 alloy tubes includes the following steps: a. Two-roll cold rolling of the TA18 alloy tube billet, followed by sandblasting to remove inner surface defects; b. Annealing and straightening; c. Repeating steps A-B 2-3 times; d. Obtaining the finished TA18 alloy tube after two rotary forging processes. The rolling method of this invention enables more uniform deformation of the titanium alloy tube, resulting in a smoother surface and significantly reducing defect generation. It effectively solves the problems of surface defects and low yield in existing titanium alloy tube manufacturing processes.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy processing technology, and relates to a method for producing seamless titanium alloy tubes, specifically a rolling method for significantly reducing defects in TA18 alloy tubes. Background Technology

[0002] Lightweight, high-strength, corrosion-resistant titanium alloys, with excellent fatigue resistance and crack propagation resistance, are the preferred materials for achieving high performance, long service life, and high reliability in aerospace hydraulic piping systems. The most typical material is TA18 (Ti-3Al-2.5V) titanium alloy, which not only possesses good room-temperature mechanical properties and corrosion resistance, but also, more importantly, excellent cold and hot working plasticity, formability, and weldability. However, producing TA18 titanium alloy tubing suitable for aerospace applications is extremely difficult and has a low yield.

[0003] Two-roll cold rolling is used to reduce the diameter of titanium alloy tubes, resulting in a high pass rate and high production efficiency. However, the large contact area between the rolls and the titanium alloy tube during cold rolling generates significant friction, leading to strong shear forces on the tube surface and a substantial reduction in surface quality. Furthermore, the openings on both sides of the rolls cause inconsistent material flow directions at different locations, resulting in anisotropy in the cold-rolled material. Rotary forging is another method for reducing the diameter of titanium alloy tubes. Rotary forging produces smaller, more uniform deformation, a smoother surface, and higher precision. The triaxial compressive stress state in the forging area is beneficial for material deformation. However, rotary forging has lower production efficiency and smaller deformation per pass.

[0004] Based on the above, it is essential to fully utilize the advantages of two-roll cold rolling and rotary forging to conduct research on the preparation method of titanium alloy tubes with high flaw detection pass rate and good surface quality, so as to improve the yield of titanium alloy tubes, reduce costs, and achieve stable, mass production. Summary of the Invention

[0005] The technical problem to be solved by the present invention is the existence of surface defects and low yield in the existing titanium alloy tube manufacturing process.

[0006] The technical solution adopted by this invention to solve its technical problem is: a rolling method for significantly reducing defects in TA18 alloy tubes, comprising the following steps:

[0007] a. The TA18 alloy tube blank is cold rolled in two rolls and then sandblasted to remove inner surface defects;

[0008] b. Anneal and straighten the titanium alloy tube processed in step a;

[0009] c. Repeat steps AB 2-3 times to obtain a semi-finished titanium alloy tube;

[0010] d. The titanium alloy tube semi-finished product is obtained by two rotary forging processes using a rotary forging machine.

[0011] In step a above, the TA18 alloy tube blank does not have a special orientation texture, and its structure should be equiaxed.

[0012] In step a above, the TA18 alloy tube blank is free of burrs, pits and cracks on its surface before cold rolling.

[0013] In step a above, the cold rolling rate is greater than 0.5 and less than 0.7.

[0014] In step a above, the ratio Q of the relative wall reduction to the relative diameter reduction of the two-roll cold-rolled TA18 alloy tube blank should be greater than 1 and less than 1.5.

[0015] In step a above, the abrasive particle size used for sandblasting is not less than 100 mesh.

[0016] In step b above, the annealing temperature is 650-750℃ and the holding time is 1-3h; after annealing, the microstructure of the titanium alloy tube should be equiaxed.

[0017] In step b above, after the titanium alloy tube is straightened, the straightness of the titanium alloy tube is less than 1 mm / m.

[0018] In step d above, the die in the rotary forging machine is replaced with a die that is close to the target outer diameter, and the mandrel size is replaced with the target inner diameter.

[0019] In step d above, the processing rate of the titanium alloy tube after a single rotary forging is greater than 0.25 and less than 0.35, and the ratio Q of the relative wall reduction to the relative diameter reduction of the titanium alloy tube after a single rotary forging should be greater than 1.5 and less than 2.5.

[0020] The beneficial effects of this invention are as follows: The rolling method of this invention first involves alternating two-roll cold rolling and annealing to obtain a seamless tube semi-finished product with high dimensional accuracy, a more uniform and fine microstructure, and no defects on both the inner and outer surfaces. Subsequently, rotary forging is used to reduce the diameter of the titanium alloy tube. Through multiple passes of small deformation, not only is the deformation of the titanium alloy tube more uniform, but the friction between the titanium alloy tube and the mold is also effectively reduced, resulting in a smoother surface. Simultaneously, by controlling the deformation amount and the ratio Q of the relative wall reduction to the relative diameter reduction in each reduction pass, a smaller Q value is used in two-roll cold rolling to avoid the formation of strong radial texture, while a larger Q value is used in rotary forging to reduce the internal wall wrinkles caused by instability during the deformation of the TA18 alloy tube, significantly reducing the occurrence of defects. Detailed Implementation

[0021] The technical solution of the present invention can be implemented in the following manner.

[0022] 1. A rolling method for significantly reducing defects in TA18 alloy pipes, specifically including the following steps:

[0023] A. TA18 alloy tube blanks are subjected to two-roll cold rolling;

[0024] B. Sandblasting is used to remove inner surface defects from cold-rolled titanium alloy tubes.

[0025] C. The cold-rolled titanium alloy tube is annealed and straightened;

[0026] D. Repeat steps AC 2-3 times to obtain a titanium alloy tube semi-finished product;

[0027] E. Use a rotary forging machine to perform the first rotary forging of the titanium alloy tube semi-finished product;

[0028] F. The titanium alloy tube is subjected to a second rotary forging using a rotary forging machine.

[0029] In step A above, the TA18 alloy tube blank does not have a special orientation texture and its structure should be equiaxed; before cold rolling, the surface of the TA18 alloy tube blank is free of burrs, pits and cracks.

[0030] In step A above, the cold rolling rate is greater than 0.5 and less than 0.7; the ratio Q of the relative wall reduction to the relative diameter reduction of the two-roll cold-rolled TA18 alloy tube billet should be greater than 1 and less than 1.5.

[0031] In step B above, the abrasive particle size used for sandblasting is not less than 100 mesh.

[0032] In step C above, the annealing temperature is (650-750)℃ and the holding time is (1-3)h; after annealing, the microstructure of the TA18 alloy tube should be equiaxed; after straightening, the straightness of the titanium tube is less than 1mm / m.

[0033] In steps E and F above, the die in the rotary forging machine is replaced with a die that is similar to the target outer diameter, and the mandrel size is replaced with the target inner diameter. The processing rate of the titanium tube after a single rotary forging is greater than 0.25 and less than 0.35, and the ratio Q of the relative wall reduction to the relative diameter reduction of the titanium tube after a single rotary forging should be greater than 1.5 and less than 2.5.

[0034] The technical solution and effects of the present invention will be further explained below through practical examples.

[0035] Example

[0036] Example 1: This example illustrates the rolling method of TA18 alloy tube with diameter Φ33mm*4.3mm (outer diameter*wall thickness) → Φ8mm*0.6mm.

[0037] A. The heat-treated Φ33mm*4.3mm titanium tube is subjected to alternating two-roll cold rolling, sandblasting and annealing, in three passes: Φ33mm*4.3mm→Φ23mm*2.8mm→Φ16mm*1.8mm→Φ10mm*1mm. The first pass has a processing rate of 0.54 and a Q value of 1.15; the second pass has a processing rate of 0.55 and a Q value of 1.17; and the third pass has a processing rate of 0.65 and a Q value of 1.19.

[0038] B. Replace the rotary forging machine with a Φ9mm die and a Φ7.4 mandrel, and use the rotary forging machine to forge the Φ10mm*1mm titanium tube straightened in step A to Φ9mm*0.8mm in one go. The processing rate is 0.27 and the Q value is 2.

[0039] C. Replace the rotary forging machine with an 8mm die and a 7mm mandrel, and use the rotary forging machine to forge the 9mm*0.8mm titanium tube from step B to 8mm*0.6mm in one go. The machining rate is 0.32 and the Q value is 2.25.

[0040] The 8mm*0.6mm TA18 titanium alloy tube obtained after rotary forging has a smooth surface without scratches, pits, wrinkles or other defects.

[0041] Example 2: This example illustrates the rolling method of TA18 alloy tube with diameter Φ23mm*4.3mm (outer diameter*wall thickness) → Φ6mm*0.6mm.

[0042] A. The heat-treated Φ23mm*4.3mm titanium tube is subjected to alternating two-roll cold rolling, sandblasting and annealing, in three passes: Φ23mm*4.3mm→Φ17mm*2.8mm→Φ12mm*1.8mm→Φ8mm*1mm. The first pass has a processing rate of 0.51 and a Q value of 1.34; the second pass has a processing rate of 0.54 and a Q value of 1.21; and the third pass has a processing rate of 0.62 and a Q value of 1.33.

[0043] B. Replace the rotary forging machine with a Φ7mm die and a Φ5.4 mandrel, and use the rotary forging machine to forge the Φ8mm*1mm titanium tube straightened in step A to Φ7mm*0.8mm in one go. The processing rate is 0.29 and the Q value is 1.6.

[0044] C. Replace the rotary forging machine with a Φ6mm die and a Φ4.8 mandrel, and use the rotary forging machine to forge the Φ7mm*0.8mm titanium tube from step B to Φ6mm*0.6mm in one go. The machining rate is 0.35 and the Q value is 1.75.

[0045] The 6mm*0.6mm TA18 titanium alloy tube obtained after rotary forging has a smooth surface without scratches, pits, wrinkles or other defects.

[0046] Comparative Example 1: The rotary forging method of reducing the diameter of TA18 alloy tube from Φ33mm*4.3mm (outer diameter*wall thickness) to Φ8mm*0.6mm is followed in Example 1, except that the raw material is a titanium tube with a diameter of Φ33mm*9mm.

[0047] A. The heat-treated Φ33mm*9mm titanium tube is subjected to alternating two-roll cold rolling, sandblasting, and annealing. The rolling process involves three passes: Φ33mm*9mm → Φ23mm*4.5mm → Φ16mm*2.3mm → Φ10mm*1mm. The first pass has a processing rate of 0.61 and a Q value of 1.65; the second pass has a processing rate of 0.62 and a Q value of 1.61; and the third pass has a processing rate of 0.71 and a Q value of 1.51. The Q value for each pass is greater than 1.5.

[0048] B. Replace the rotary forging machine with a Φ9mm die and a Φ7.4 mandrel, and use the rotary forging machine to forge the Φ10mm*1mm titanium tube straightened in step A to Φ9mm*0.8mm in one go. The processing rate is 0.27 and the Q value is 2.

[0049] C. Replace the rotary forging machine with an 8mm die and a 7mm mandrel, and use the rotary forging machine to forge the 9mm*0.8mm titanium tube from step B to 8mm*0.6mm in one go. The machining rate is 0.32 and the Q value is 2.25.

[0050] When the 9mm*0.8mm TA18 titanium alloy tube was obtained after the first rotary forging, the strong radial texture had been formed by the previous two-roll cold rolling, making it difficult to perform subsequent rotary forging with a large Q value. Transverse cracks were present on both the inner and outer surfaces.

[0051] Comparative Example 2: Following the rotary forging method of reducing the diameter of TA18 alloy tube from Φ8mm*1mm (outer diameter*wall thickness) to Φ6mm*0.6mm in Example 2, the difference is that in step B, the rotary forging machine is replaced with a Φ6mm die and a Φ4.8 mandrel, and the rotary forging machine is used to rotary forge the titanium alloy tube straightened in step A to Φ6mm*0.6mm in one go.

[0052] The 6mm*0.6mm TA18 titanium alloy tube obtained after rotary forging has a single rotary forging rate of 53.7%. Both the inner and outer surfaces of the titanium tube have defects such as burrs, pits, and cracks.

Claims

1. A rolling method for substantially reducing defects in a TA18 alloy tube, characterized by The method comprises the following steps: a. the TA18 alloy pipe blank is subjected to two-roller cold rolling, and then sand blasting is performed to remove inner surface defects; the cold rolling processing rate is greater than 0.5 and less than 0.7, and the ratio Q of the relative wall thickness reduction amount to the relative diameter reduction amount of the two-roller cold rolled TA18 alloy pipe blank should be greater than 1 and less than 1.5; b. the titanium alloy pipe after step a is subjected to annealing and straightening; c. the steps a-b are repeated for 2-3 times to obtain a titanium alloy pipe semi-product; d. the titanium alloy pipe semi-product is subjected to two times of rotary swaging by using a rotary swaging machine to obtain a TA18 alloy pipe product; the processing rate of the titanium alloy pipe after single rotary swaging is greater than 0.25 and less than 0.35, and the ratio Q of the relative wall thickness reduction amount to the relative diameter reduction amount of the titanium alloy pipe after single rotary swaging should be greater than 1.5 and less than 2.

5.

2. The rolling method for greatly reducing the defects of TA18 alloy pipe according to claim 1, characterized in that: In step a, the TA18 alloy pipe blank does not have special orientation texture, and the structure thereof should be equiaxed structure.

3. The method of claim 1, wherein the TA18 alloy tube has a defect reduction of at least 90%. In step a, the TA18 alloy pipe blank does not have burrs, pits and cracks on the surface before cold rolling.

4. The method of claim 1, wherein the TA18 alloy tube has a defect reduction of at least 90%. In step a, the granularity of the abrasive used in sand blasting is not less than 100 mesh.

5. The method of claim 1 wherein the TA18 alloy tube has a substantially reduced defect level. In step b, the annealing temperature is 650-750 DEG C, and the holding time is 1-3 h; the structure of the titanium alloy pipe after annealing should be equiaxed structure.

6. The method of claim 1 wherein the TA18 alloy tube has a substantially reduced number of defects. In step b, the straightness of the titanium alloy pipe after straightening is less than 1 mm / m.

7. The method of claim 1 wherein the TA18 alloy tube has a substantially reduced defect level. In step d, the die in the rotary swaging machine is replaced by a die with a size close to the target outer diameter size, and the size of the mandrel is replaced by the target inner diameter size.