A method for improving the yield of TA18 titanium alloy seamless pipe

Abstract

The application provides a method for improving the yield of TA18 titanium alloy seamless pipe, and specifically comprises the following steps: step one, pressing raw materials into multiple electrode blocks to obtain consumable electrodes after welding, wherein the raw materials contain yttrium alloy elements with a mass percentage of 0.001% to 0.03%; step two, melting to obtain titanium alloy ingots; step three, directly hot continuous rolling the titanium alloy ingots without skinning at 1050-1150 DEG C for 4.5-7.5 hours to obtain titanium alloy rods; step four, slanting piercing to obtain a blank pipe; step five, pickling the blank pipe and then cold rolling it in one pass; step six, boring the pipe blank from inside to outside, annealing and then hot continuous rolling; step seven, polishing the outer surface and grinding the inner surface after pickling; step eight, cold rolling no more than 4 times; step nine, straightening, pickling and vacuum annealing; and step ten, magnetic polishing. The application can improve the yield of TA18 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 TA18 titanium alloy seamless tubes. Background Technology

[0002] TA18 titanium alloy seamless tubes possess excellent room-temperature mechanical properties and corrosion resistance, making them widely used in aerospace, oilfield, and other fields, particularly in aviation hydraulic piping systems. With increasing hydraulic system pressures, the requirements for TA18 titanium alloy seamless tubes are also rising. Currently, the common processing techniques for TA18 titanium alloy seamless tubes include melting, forging, extrusion, machining, cold rolling, and annealing. Due to the narrow temperature range during high-temperature deformation and high resistance to low-temperature deformation of TA18 titanium alloy, the above processing methods are complex, resulting in significant losses during forging and machining, and low yields. Especially for seamless tubes used in aviation hydraulic piping with diameters less than 25mm, to reduce cold rolling passes and shorten the production cycle, the extruded tube diameter is smaller, significantly reducing the machining yield and resulting in a final yield of less than 30%. Summary of the Invention

[0003] To address the technical problem of low yield in existing TA18 titanium alloy seamless tube processing methods, this invention provides a method for improving the yield of TA18 titanium alloy seamless tubes.

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

[0005] A method for producing TA18 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. Yttrium, an alloying element, is added to the raw material at a mass percentage of 0.001% to 0.03%.

[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 ≥200mm. 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 tube, perform a single cold rolling process with a cold rolling deformation of ≤10% to improve the ovality of the tube.

[0011] Step 6: The tube blank obtained in Step 5 is internally bored and externally turned, annealed, and then hot continuously rolled. The initial rolling temperature is 300℃~400℃, the deformation amount of each pass gradually decreases, and the deformation amount of the first pass is ≤60%, and the deformation amount of the last pass is ≤15%.

[0012] Step 7: After pickling the pipe obtained in Step 6, polish the outer surface and hon the inner surface;

[0013] Step 8: The tube obtained in Step 7 is cold rolled into a titanium alloy seamless tube semi-finished product in no more than 4 passes. The outer diameter of the tube is ≤20mm and the deformation in the last pass is ≤20%.

[0014] Step 9: Straighten, pickle, and vacuum anneal the seamless tube semi-finished product obtained in Step 8;

[0015] Step 10: Perform magnetic polishing on the pipe obtained in Step 9.

[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 a deformation of 15%~30% and a tube diameter to bar diameter ratio of 1~1.2.

[0017] Furthermore, in step eight, annealing is performed before each cold rolling pass, with an annealing temperature of 600℃~750℃, and the annealing temperature of each pass is not higher than the annealing temperature of the previous pass, and the holding time is 1h~2.5h.

[0018] Furthermore, in step nine, the annealing temperature is 400℃~600℃, and the holding time is 1h~2h.

[0019] Furthermore, in step ten, the magnetic abrasive particles used for magnetic polishing are SiC with a particle size of 0.005 mm to 0.1 mm, and the surface roughness of the inner and outer surfaces of the tube after magnetic polishing is ≤200 nm.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] The method for improving the yield of TA18 titanium alloy seamless tubes provided by this invention optimizes the composition of TA18 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 cold rolling of the tube blank improves the ovality of the tube blank, increasing the yield of subsequent internal boring and external turning. Subsequent multi-pass cold rolling results in minimal material loss, and the yield of seamless tubes can reach over 40%. Finally, polishing is used to eliminate burrs that may exist on the inner and outer surfaces of small-diameter seamless tubes and improve roughness, increasing the pass rate of the tubes.

[0022] Based on the above reasons, this invention can be widely promoted in the field of titanium alloy seamless tube production. Detailed Implementation

[0023] 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.

[0024] This invention provides a method for producing TA18 titanium alloy seamless tubes, specifically including the following steps:

[0025] 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. Yttrium, an alloying element with a mass percentage between 0.001% and 0.03%, is added to the raw material. The addition of yttrium is used to improve the plasticity and processability of the alloy.

[0026] Step 2: Melt the consumable electrode three times in a vacuum consumable arc furnace to obtain a titanium alloy ingot with a diameter ≤750mm.

[0027] 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 ≥200mm. 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%.

[0028] 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.

[0029] Step 5: After pickling the tube, perform a single cold rolling process with a cold rolling deformation of ≤10% to improve the ovality of the tube.

[0030] Step 6: The tube blank obtained in Step 5 is internally bored and externally turned, annealed, and then hot continuously rolled. The initial rolling temperature is 300℃~400℃, the deformation amount of each pass gradually decreases, and the deformation amount of the first pass is ≤60%, and the deformation amount of the last pass is ≤15%.

[0031] Step 7: After pickling the pipe obtained in Step 6, polish the outer surface and hon the inner surface;

[0032] Step 8: The tube obtained in Step 7 is cold rolled into a titanium alloy seamless tube semi-finished product in no more than 4 passes. The outer diameter of the tube is ≤20mm and the deformation in the last pass is ≤20%.

[0033] Step 9: Straighten, pickle, and vacuum anneal the seamless tube semi-finished product obtained in Step 8;

[0034] Step 10: Perform magnetic polishing on the pipe obtained in Step 9 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.

[0035] Furthermore, the raw materials also include sponge titanium, aluminum briquettes, titanium-iron alloys, aluminum-vanadium alloys, and titanium dioxide.

[0036] 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 a deformation of 15%~30% and a tube diameter to bar diameter ratio of 1~1.2.

[0037] Furthermore, in step eight, annealing is performed before each cold rolling pass, with an annealing temperature of 600℃~750℃, and the annealing temperature of each pass is not higher than the annealing temperature of the previous pass, and the holding time is 1h~2.5h.

[0038] Furthermore, in step nine, the annealing temperature is 400℃~600℃, and the holding time is 1h~2h.

[0039] Furthermore, in step ten, the magnetic abrasive particles used for magnetic polishing are SiC with a particle size of 0.005 mm to 0.1 mm, and the surface roughness of the inner and outer surfaces of the tube after magnetic polishing is ≤200 nm.

[0040] Example 1

[0041] This embodiment uses the method described in this invention to produce TA18 titanium alloy seamless tubes with specifications of Φ19×2.2mm, specifically including the following steps:

[0042] 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 yttrium is added to the raw material.

[0043] Step 2: Melt the consumable electrode three times in a vacuum consumable arc furnace to obtain a titanium alloy ingot with a diameter of Φ730mm.

[0044] 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.

[0045] 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%.

[0046] Step 5: After pickling, the tube is cold rolled in one pass to Φ230*46mm with a cold rolling deformation of 8%.

[0047] 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 vacuum annealing at 400℃ for 2.5h, it is hot rolled continuously at an initial rolling temperature of 350℃. The deformation amount in the first pass is 55.7%, the deformation amount in the second pass is 49%, the deformation amount in the third pass is 43.1%, the deformation amount in the fourth pass is 39.6%, the deformation amount in the fifth pass is 30.7%, the deformation amount in the sixth pass is 29.3%, and the deformation amount in the seventh pass is 13%, finally obtaining a tube with Φ52*5.5, with a yield of 90%.

[0048] Step 7: Pickle the pipe obtained in Step 6, then polish the outer surface and hon the inner surface to obtain a Φ51.5*5 cold-rolled pipe blank with a yield of 90.9%.

[0049] Step 8: The tube obtained in Step 7 is cold-rolled four times to form a seamless titanium alloy tube semi-finished product.

[0050] After vacuum annealing at 750℃ for 2 hours, the material was cold-rolled to Φ42*3.2mm; after vacuum annealing at 750℃ for 2 hours, the material was cold-rolled to Φ30*2.6mm; after vacuum annealing at 750℃ for 1.5 hours, the material was cold-rolled to Φ22*2.3mm; after vacuum annealing at 750℃ for 1.5 hours, the material was cold-rolled to Φ19*2.2mm, with a deformation of 18.4%.

[0051] Step 9: Straighten, pickle, and vacuum anneal at 600℃ for 2 hours the seamless tube semi-finished product obtained in Step 8;

[0052] Step 10: Perform magnetic polishing on the pipe obtained in Step 9.

[0053] In this embodiment, after internal boring and external turning of the tube, the yield of each cold rolling pass is 95%. The yield of the TA18 titanium alloy seamless tube from the ingot is 91.6%*91.3%*90%*90.9%*95%*95%*95%*95%=55.7%. After magnetic polishing, the inner surface roughness is 180nm, the outer surface roughness is 150nm, and the qualified product rate is 95%.

[0054] Example 2

[0055] This embodiment uses the method described in this invention to produce TA18 titanium alloy seamless tubes with specifications of Φ14×1.7mm, 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. 0.008% of the alloying element yttrium is added to the raw material.

[0057] Step 2: Melt the consumable electrode three times in a vacuum consumable arc furnace to obtain a titanium alloy ingot with a diameter of Φ690mm.

[0058] Step 3: Without peeling, the titanium alloy ingot is held at 1150℃ for 7 hours and then hot-rolled into titanium alloy bars. The deformation amount of the first pass of hot rolling is 14%, the deformation amount of the second pass is 26%, the deformation amount of the third pass is 39%, the deformation amount of the fourth pass is 44.6%, the deformation amount of the fifth pass is 28.8%, and the deformation amount of the sixth pass is 7.3%, finally obtaining Φ260mm titanium alloy bars.

[0059] Step 4: The surface of the titanium alloy bar is machined to obtain a Φ250mm bar with a yield of 92.4%. After holding at 1030℃ for 2.5h, it is skew-rolled and pierced to form a Φ275*50mm tube with a deformation of 28%.

[0060] Step 5: After pickling, the tube is cold rolled in one pass to Φ265*47mm, with a cold rolling deformation of 8.9%;

[0061] Step Six: The tube blank obtained in Step Five is internally bored and externally machined to Φ261*43mm, with a yield of 91.4%. After vacuum annealing at 450℃ for 2.5h, it is hot rolled continuously at an initial rolling temperature of 380℃. The deformation amounts are as follows: first pass 57.9%, second pass 53.4%, third pass 49%, fourth pass 42.7%, fifth pass 34%, sixth pass 29.4%, seventh pass 26.4%, and eighth pass 14.9%, finally yielding a tube with a diameter of Φ46*3.7 and a yield of 90%.

[0062] Step 7: Pickling the pipe obtained in Step 6, polishing the outer surface and honing the inner surface to obtain a Φ45.5*3.2 cold-rolled pipe blank with a yield of 86.4%.

[0063] Step 8: The tube obtained in Step 7 is cold-rolled four times to form a seamless titanium alloy tube semi-finished product.

[0064] After vacuum annealing at 750℃ for 2 hours, the material was cold-rolled to Φ30*2.6mm; after vacuum annealing at 750℃ for 2 hours, the material was cold-rolled to Φ20*2.3mm; after vacuum annealing at 750℃ for 1.5 hours, the material was cold-rolled to Φ15*2mm; after vacuum annealing at 750℃ for 1.5 hours, the material was cold-rolled to Φ14*1.7mm, with a deformation of 19.6%.

[0065] Step 9: Straighten, pickle, and vacuum anneal at 550℃ for 2 hours the seamless tube semi-finished product obtained in Step 8;

[0066] Step 10: Perform magnetic polishing on the pipe obtained in Step 9.

[0067] In this embodiment, after internal boring and external turning of the tube, the yield of each cold rolling pass is 95%. The yield of the TA18 titanium alloy seamless tube from the ingot is 92.4% * 91.4% * 90% * 86.4% * 95% * 95% * 95% * 95% = 53.6%. After magnetic polishing, the inner surface roughness is 160nm, the outer surface roughness is 120nm, and the qualified product rate is 93%.

[0068] 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 TA18 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. Yttrium, an alloying element, is added to the raw material at a mass percentage of 0.001% to 0.03%. 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 ≥200mm. 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 tube, perform a single cold rolling process with a cold rolling deformation of ≤10% to improve the ovality of the tube. Step 6: The tube blank obtained in Step 5 is internally bored and externally turned, annealed, and then hot continuously rolled. The initial rolling temperature is 300℃~400℃, the deformation amount of each pass gradually decreases, and the deformation amount of the first pass is ≤60%, and the deformation amount of the last pass is ≤15%. Step 7: After pickling the pipe obtained in Step 6, polish the outer surface and hon the inner surface; Step 8: The tube obtained in Step 7 is cold rolled into a titanium alloy seamless tube semi-finished product in no more than 4 passes. The outer diameter of the tube is ≤20mm and the deformation in the last pass is ≤20%. Step 9: Straighten, pickle, and vacuum anneal the seamless tube semi-finished product obtained in Step 8; Step 10: Perform magnetic polishing on the pipe obtained in Step 9.

2. The method for improving the yield of TA18 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 with a deformation of 15%~30% and a tube diameter to bar diameter ratio of 1~1.

2.

3. The method for improving the yield of TA18 titanium alloy seamless tubes according to claim 1, characterized in that, In step eight, annealing is performed before each cold rolling pass. The annealing temperature is 600℃~750℃, and the annealing temperature of each pass is not higher than the annealing temperature of the previous pass. The holding time is 1h~2.5h.

4. The method for improving the yield of TA18 titanium alloy seamless tubes according to claim 1, characterized in that, In step nine, the annealing temperature is 400℃~600℃, and the holding time is 1h~2h.

5. The method for improving the yield of TA18 titanium alloy seamless tubes according to claim 1, characterized in that, In step ten, the magnetic abrasive particles used for magnetic polishing are SiC with a particle size of 0.005 mm to 0.1 mm. After magnetic polishing, the surface roughness of the inner and outer surfaces of the tube is ≤200 nm.