A method for improving the yield of TA16 titanium alloy seamless pipe

Abstract

The application provides a method for improving the yield of TA16 titanium alloy seamless pipe, and specifically comprises the following steps: step one, mixing raw materials to press into multiple electrode blocks, and welding to obtain consumable electrode, wherein the alloying element cerium with a mass percentage of 0.005-0.02% is added into the raw materials; step two, smelting to obtain titanium alloy ingot; step three, hot continuous rolling to form titanium alloy bar; in the hot rolling process, the pass deformation amount is first increased and then decreased, the maximum deformation amount is not more than 50%, and the deformation amount of the first pass and the last pass is not more than 15%; step four, cross wedge rolling to form a pipe blank; step five, pickling and then performing first-time precision forging; step six, boring the pipe blank from the inside and turning the outside, and then performing multi-pass warm precision forging after annealing, the temperature is 100-200 DEG C, the deformation amount of each pass is greater than or equal to 50%, and Q is 0.8-1.5; step seven, pickling and annealing and then performing cold rolling; step eight, pickling and vacuum annealing; and step nine, magnetic polishing. The application can improve the yield of TA16 titanium alloy seamless pipe to more than 40%.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy seamless tube production technology, and more particularly to a method for improving the yield of TA16 titanium alloy seamless tubes. Background Technology

[0002] TA16 (Ti-2Al-2.5Zr) alloy is a medium-strength, high-ductility single-phase α-titanium alloy with high specific strength, good corrosion resistance, and excellent machinability. Seamless tubes made from it are widely used in piping systems in aerospace, nuclear power, and shipbuilding industries. Common processing techniques for TA16 titanium alloy seamless tubes include melting, forging, extrusion, machining, cold rolling, and annealing. However, due to the narrow temperature range during high-temperature deformation and high resistance to low-temperature deformation of TA16 titanium alloy, forging results in a certain yield loss, and the material loss during machining before and after extrusion is even greater. This leads to low yield rates with existing processing methods, especially for TA16 titanium alloy seamless tubes with a diameter of no more than 18mm, where the yield is less than 30%. Summary of the Invention

[0003] To address the technical problem of low yield in existing TA16 titanium alloy seamless tube processing methods, this invention provides a method for improving the yield of TA16 titanium alloy seamless tubes.

[0004] The technical means employed in this invention are as follows:

[0005] A method for improving the yield of TA16 titanium alloy seamless tubes specifically includes the following steps:

[0006] Step 1: The raw material mixture is pressed into multiple electrode blocks, and then the multiple electrode blocks are welded together to obtain a consumable electrode. The raw material contains cerium, an alloying element with a mass percentage between 0.005% and 0.02%.

[0007] Step 2: Melt the consumable electrode to obtain a titanium alloy ingot with a diameter ≤750mm;

[0008] Step 3: Without peeling, the titanium alloy ingot is held at 1050℃~1150℃ for 4.5h~7.5h and then hot-rolled into titanium alloy bars with a diameter ≥150mm. During the hot rolling process, the deformation per pass first increases and then decreases, and the maximum deformation does not exceed 50%. The deformation of the first and last passes during the hot rolling process does not exceed 15%.

[0009] Step 4: The titanium alloy bar is skew-rolled and pierced to form a rough tube, with a deformation of 15% to 30%.

[0010] Step 5: After pickling the capillary tube, perform the first precision forging, with a forging deformation of ≤10%;

[0011] Step 6: The tube blank obtained in Step 5 is internally bored and externally machined, annealed, and then subjected to multi-pass warm precision forging. The temperature of the multi-pass warm precision forging is 100℃~200℃, the deformation amount of each pass is ≥50%, and the ratio of relative wall reduction to relative diameter reduction Q is 0.8~1.5.

[0012] Step 7: Pickle and anneal the tube obtained in Step 6, and then cold roll it to obtain a semi-finished TA16 titanium alloy seamless tube. The outer diameter of the tube is ≤18mm, and the deformation in the last pass of the cold rolling process is ≤20%.

[0013] Step 8: Pickling and vacuum annealing are performed on the seamless tube semi-finished product obtained in Step 7;

[0014] Step 9: Perform magnetic polishing on the pipe obtained in Step 8.

[0015] Furthermore, the raw materials also include sponge titanium, sponge zirconium, aluminum briquettes, titanium-iron alloys, and titanium dioxide.

[0016] Further, step four specifically includes: polishing the surface of the titanium alloy bar, holding it at 950℃~1050℃ for 2.0h~3.5h, and then skew rolling and piercing it into a tube, with the tube diameter to the titanium alloy bar diameter ratio being 1~1.2.

[0017] Furthermore, in step six, annealing is performed before each pass of heated precision forging. The annealing temperature is 700℃~800℃, and the holding time is 1h~2.5h.

[0018] Furthermore, if more than one cold rolling pass is performed in step seven, annealing is carried out between the two cold rolling passes at a temperature of 650℃~750℃ and a holding time of 1~2.5h.

[0019] Furthermore, in step eight, the annealing temperature is 450℃~650℃, and the holding time is 1h~2h.

[0020] Furthermore, in step nine, the magnetic abrasive particles used for magnetic polishing are stainless steel needles with a particle size of 0.01mm to 0.5mm, and the surface roughness of the inner and outer surfaces of the tube after magnetic polishing is ≤300nm.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The method for improving the yield of TA16 titanium alloy seamless tubes provided by this invention optimizes the composition of TA16 titanium alloy, enhancing the hot deformation capability of the ingot to directly hot-roll into billets, replacing forging and improving the yield of billets. As hot rolling proceeds, the alloy microstructure is improved, the deformation capability is enhanced, and the deformation amount gradually increases. Subsequent hot rolling passes require reduced deformation due to temperature rise. Skew rolling piercing is used instead of drilling before machining or extrusion, improving the yield of the tube blank. The first pass of small-deformation precision forging of the tube blank improves the ovality of the tube blank, increasing the yield of subsequent internal boring and external turning. Subsequent multi-pass heated precision forging and cold rolling result in minimal material loss. Heated precision forging increases deformation and improves production efficiency. The final cold rolling helps improve the precision of small-diameter seamless tubes, ultimately achieving a seamless tube yield of over 40%. Finally, magnetic polishing eliminates burrs that may exist on the inner and outer surfaces of small-diameter seamless tubes and improves roughness, increasing the pass rate of the tubes.

[0023] Based on the above reasons, this invention can be widely promoted in the field of titanium alloy seamless tube production. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0025] This invention provides a method for improving the yield of TA16 titanium alloy seamless tubes, specifically including the following steps:

[0026] Step 1: The raw material mixture is pressed into multiple electrode blocks, and then the multiple electrode blocks are welded together to obtain a consumable electrode. The raw material contains cerium, an alloying element with a mass percentage between 0.005% and 0.02%. The addition of cerium is used to improve the plasticity and machinability of the alloy.

[0027] Step 2: Melt the consumable electrode twice in a vacuum consumable arc furnace to obtain a titanium alloy ingot with a diameter ≤750mm.

[0028] Step 3: Without peeling, the titanium alloy ingot is held at 1050℃~1150℃ for 4.5h~7.5h and then hot-rolled into titanium alloy bars with a diameter ≥150mm. During the hot rolling process, the deformation per pass first increases and then decreases, and the maximum deformation does not exceed 50%. The deformation of the first and last passes during the hot rolling process does not exceed 15%.

[0029] Step 4: The titanium alloy bar is skew-rolled and pierced to form a tube, with a deformation of 15% to 30%. Using skew rolling and piercing instead of drilling before machining or extrusion can improve the yield of the tube.

[0030] Step 5: After pickling, the tube is subjected to the first precision forging. The deformation amount of precision forging is ≤10%, which improves the ovality and dimensional accuracy of the tube and increases the yield of the tube.

[0031] Step Six: The tube blank obtained in Step Five is internally bored and externally machined, annealed, and then subjected to multi-pass warm precision forging. The temperature of the multi-pass warm precision forging is 100℃~200℃, the deformation amount of each pass is ≥50%, and the ratio of relative wall reduction to relative diameter reduction Q is 0.8~1.5. The Q value is controlled within this range because an excessively large Q value will cause the tube to obtain an excessively strong radial texture after multi-pass precision forging. An excessively strong texture will cause cold rolling cracking and greatly reduce the yield.

[0032] Step 7: Pickle and anneal the tube obtained in Step 6, and then cold roll it to obtain a semi-finished TA16 titanium alloy seamless tube. The outer diameter of the tube is ≤18mm, and the deformation in the last pass of the cold rolling process is ≤20%.

[0033] The multi-pass hot forging and cold rolling processes in steps six and seven result in minimal material loss. Hot forging increases deformation and improves production efficiency, while cold rolling helps improve the precision of small-diameter seamless tubes, enabling the yield of seamless tubes to reach over 40%.

[0034] Step 8: Pickling and vacuum annealing are performed on the seamless tube semi-finished product obtained in Step 7;

[0035] Step 9: Perform magnetic polishing on the pipe obtained in Step 8 to eliminate burrs that may exist on the inner and outer surfaces of the small-diameter seamless pipe and improve roughness, thereby increasing the yield of qualified pipes.

[0036] Furthermore, the raw materials also include sponge titanium, sponge zirconium, aluminum briquettes, titanium-iron alloys, and titanium dioxide.

[0037] Further, step four specifically includes: polishing the surface of the titanium alloy bar, holding it at 950℃~1050℃ for 2.0h~3.5h, and then skew rolling and piercing it into a tube, with the tube diameter to the titanium alloy bar diameter ratio being 1~1.2.

[0038] Furthermore, in step six, annealing is performed before each pass of heated precision forging. The annealing temperature is 700℃~800℃, and the holding time is 1h~2.5h.

[0039] Furthermore, if more than one cold rolling pass is performed in step seven, annealing is carried out between the two cold rolling passes at a temperature of 650℃~750℃ and a holding time of 1~2.5h.

[0040] Furthermore, in step eight, the annealing temperature is 450℃~650℃, and the holding time is 1h~2h.

[0041] Furthermore, in step nine, the magnetic abrasive particles used for magnetic polishing are stainless steel needles with a particle size of 0.01mm to 0.5mm, and the surface roughness of the inner and outer surfaces of the tube after magnetic polishing is ≤300nm.

[0042] Example 1

[0043] This embodiment uses the method described in this invention to produce TA16 titanium alloy seamless tubes with specifications of Φ15×1.7mm, specifically including the following steps:

[0044] Step 1: The raw material mixture is pressed into multiple electrode blocks, and then the multiple electrode blocks are welded together to obtain a consumable electrode. 0.01% of the alloying element cerium is added to the raw material.

[0045] Step 2: Melt the consumable electrode twice in a vacuum consumable arc furnace to obtain a Φ730mm titanium alloy ingot;

[0046] Step 3: Without peeling, the titanium alloy ingot is held at 1150℃ for 7.5 hours and then hot-rolled into titanium alloy bars. The deformation amount of the first pass of hot rolling is 13%, the deformation amount of the second pass is 22%, the deformation amount of the third pass is 36%, the deformation amount of the fourth pass is 47%, the deformation amount of the fifth pass is 36%, the deformation amount of the sixth pass is 20%, and the deformation amount of the seventh pass is 12%, finally obtaining Φ235mm titanium alloy bars.

[0047] Step 4: The surface of the titanium alloy bar is machined to obtain a Φ225mm bar with a yield of 91.6%. After holding at 1030℃ for 2.5h, it is skew-rolled and pierced to form a Φ240*48mm tube with a deformation of 27%.

[0048] Step 5: After pickling, the capillary tube is precision forged in one pass to Φ230*46mm, with a precision forging deformation of 8%.

[0049] Step Six: The tube blank obtained in Step Five is internally bored and externally machined to Φ226*42mm, with a yield of 91.3%. After annealing, it undergoes multiple passes of warm forging, including: vacuum annealing at 780℃ for 2.5 hours followed by warm forging at 150℃ to Φ162*25, with a deformation of 55.7% and a Q value of 1.4; vacuum annealing at 780℃ for 2 hours followed by warm forging at 150℃ to Φ112*14, with a deformation of 59.9% and a Q value of 1.4; and vacuum annealing at 750℃ for 2 hours followed by... The product was precision forged at 150℃ to a diameter of Φ75*9 with a Q value of 1.1 and a deformation of 56.7%. After vacuum annealing at 750℃ for 2 hours, it was precision forged at 150℃ to a diameter of Φ50*6 with a Q value of 1.0 and a deformation of 55.6%. After vacuum annealing at 750℃ for 2 hours, it was precision forged at 150℃ to a diameter of Φ32*4 with a Q value of 0.9 and a deformation of 57.6%. After vacuum annealing at 750℃ for 1.5 hours, it was precision forged at 150℃ to a diameter of Φ21*2.8 with a deformation of 54.5%.

[0050] Step 7: Pickle the pipe obtained in Step 6, vacuum anneal at 750℃ for 1.5h, then cold roll it to Φ16*2mm, then vacuum anneal at 750℃ for 2h, and then cold roll it to Φ15*1.7mm, with a deformation of 19.3%.

[0051] Step 8: Pickle the seamless tube semi-finished product obtained in Step 7 and vacuum anneal at 700℃ for 2 hours;

[0052] Step 9: Perform magnetic polishing on the pipe obtained in Step 8.

[0053] In this embodiment, after internal boring and external turning of the tube, the yield of each pass of precision forging and cold rolling is 95%. The yield of the TA16 titanium alloy seamless tube from the ingot is 91.6%*91.3%*95%*95%*95%*95%*95%*95%*95%*95%=50.9%. After magnetic polishing, the inner surface roughness is 280nm, the outer surface roughness is 250nm, and the qualified product rate is 90%.

[0054] Example 2

[0055] This embodiment uses the method described in this invention to produce TA16 titanium alloy seamless tubes with specifications of Φ18×1.8mm, specifically including the following steps:

[0056] Step 1: The raw material mixture is pressed into multiple electrode blocks, and then the multiple electrode blocks are welded together to obtain a consumable electrode. 0.006% of the alloying element cerium is added to the raw material.

[0057] Step 2: Melt the consumable electrode twice using a vacuum consumable arc furnace to obtain a Φ500mm titanium alloy ingot.

[0058] Step 3: Without peeling, the titanium alloy ingot is held at 1150℃ for 5 hours and then hot-rolled into titanium alloy bars. The deformation amount of the first pass of hot rolling is 11.6%, the second pass is 27.6%, the third pass is 36%, the fourth pass is 43.8%, the fifth pass is 37.3%, the sixth pass is 29.1%, and the seventh pass is 12.1%, finally obtaining Φ150mm titanium alloy bars.

[0059] Step 4: The surface of the titanium alloy bar is machined to obtain a Φ140mm bar with a yield of 87.1%. After holding at 1030℃ for 2.5h, it is skew-rolled and pierced to form a Φ150*30mm tube with a deformation of 26.5%.

[0060] Step 5: After pickling, the capillary tube is precision forged in one pass to Φ145*28mm, with a precision forging deformation of 9%.

[0061] Step Six: The tube blank obtained in Step Five is internally bored and externally machined to Φ141*24mm, with a yield of 85.7%. After annealing, it undergoes multiple passes of warm forging, including: vacuum annealing at 780℃ for 2.5 hours followed by warm forging at 150℃ to Φ90*15, Q value 1.0, deformation amount 59.9%; vacuum annealing at 780℃ for 2 hours followed by warm forging at 150℃ to Φ63*8.5, Q value 1.4, deformation amount... 58.8%; after vacuum annealing at 750℃ for 2 hours, it was precision forged at 150℃ to obtain Φ45*5, Q value 1.4, deformation amount 56.8%; after vacuum annealing at 750℃ for 1.5 hours, it was precision forged at 150℃ to obtain Φ32*3, Q value 1.4, deformation amount 56.5%; after vacuum annealing at 750℃ for 1.5 hours, it was precision forged at 150℃ to obtain Φ20*2, Q value 0.9, deformation amount 58.6%;

[0062] Step 7: Pickle the pipe obtained in Step 6, vacuum anneal at 750℃ for 1.5h, and then cold roll it to Φ18*1.8mm with a deformation of 19%.

[0063] Step 8: Pickle the seamless tube semi-finished product obtained in Step 7 and vacuum anneal at 700℃ for 2 hours;

[0064] Step 9: Perform magnetic polishing on the pipe obtained in Step 8.

[0065] In this embodiment, after internal boring and external turning of the tube, the yield of each pass of precision forging and cold rolling is 95%. The yield of the TA16 titanium alloy seamless tube from the ingot is 87.1% * 85.7% * 95% * 95% * 95% * 95% * 95% * 95% * 95% * 95% = 47.3%. After magnetic polishing, the inner surface roughness is 250 nm, the outer surface roughness is 200 nm, and the qualified product rate is 95%.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the yield of TA16 titanium alloy seamless tubes, characterized in that, Specifically, the following steps are included: Step 1: The raw material mixture is pressed into multiple electrode blocks, and then the multiple electrode blocks are welded together to obtain a consumable electrode. The raw material contains cerium, an alloying element with a mass percentage between 0.005% and 0.02%. Step 2: Melt the consumable electrode to obtain a titanium alloy ingot with a diameter ≤750mm; Step 3: Without peeling, the titanium alloy ingot is held at 1050℃~1150℃ for 4.5h~7.5h and then hot-rolled into titanium alloy bars with a diameter ≥150mm. During the hot rolling process, the deformation per pass first increases and then decreases, and the maximum deformation does not exceed 50%. The deformation of the first and last passes during the hot rolling process does not exceed 15%. Step 4: The titanium alloy bar is skew-rolled and pierced to form a rough tube, with a deformation of 15% to 30%. Step 5: After pickling the capillary tube, perform the first precision forging, with a forging deformation of ≤10%; Step 6: The tube blank obtained in Step 5 is internally bored and externally machined, annealed, and then subjected to multi-pass warm precision forging. The temperature of the multi-pass warm precision forging is 100℃~200℃, the deformation amount of each pass is ≥50%, and the ratio of relative wall reduction to relative diameter reduction Q is 0.8~1.

5. Step 7: Pickle and anneal the tube obtained in Step 6, and then cold roll it to obtain a semi-finished TA16 titanium alloy seamless tube. The outer diameter of the tube is ≤18mm, and the deformation in the last pass of the cold rolling process is ≤20%. Step 8: Pickling and vacuum annealing are performed on the seamless tube semi-finished product obtained in Step 7; Step 9: Perform magnetic polishing on the pipe obtained in Step 8.

2. The method for improving the yield of TA16 titanium alloy seamless tubes according to claim 1, characterized in that, Step four specifically includes: polishing the surface of the titanium alloy bar, holding it at 950℃~1050℃ for 2.0h~3.5h, and then skew rolling and piercing it into a tube. The ratio of the tube diameter to the diameter of the titanium alloy bar is 1~1.

2.

3. The method for improving the yield of TA16 titanium alloy seamless tubes according to claim 1, characterized in that, In step six, annealing is performed before each pass of heated precision forging. The annealing temperature is 700℃~800℃, and the holding time is 1h~2.5h.

4. The method for improving the yield of TA16 titanium alloy seamless tubes according to claim 1, characterized in that, If more than one cold rolling pass is performed in step seven, annealing is carried out between the two cold rolling passes at a temperature of 650℃~750℃ and a holding time of 1~2.5h.

5. The method for improving the yield of TA16 titanium alloy seamless tubes according to claim 1, characterized in that, In step eight, the annealing temperature is 450℃~650℃, and the holding time is 1h~2h.

6. The method for improving the yield of TA16 titanium alloy seamless tubes according to claim 1, characterized in that, In step nine, the magnetic abrasive particles used for magnetic polishing are stainless steel needles with a particle size of 0.01mm to 0.5mm. After magnetic polishing, the surface roughness of the inner and outer surfaces of the tube is ≤300nm.