Method for improving yield of TA16 titanium alloy seamless tube

Abstract

The invention provides a method for improving the yield of TA16 titanium alloy seamless tubes, which specifically comprises the following steps of: 1, mixing and pressing raw materials into a plurality of electrode blocks, welding to obtain a consumable electrode, and adding an alloy element cerium with the mass percent of 0.005-0.02% into the raw materials; 2, a titanium alloy cast ingot is obtained through smelting; thirdly, a titanium alloy bar is formed through hot continuous rolling; in the hot rolling process, the pass deformation is firstly increased and then reduced, the maximum deformation does not exceed 50%, and the first pass deformation and the last pass deformation are not larger than 15%; 4, performing cross piercing to form a tubular billet; fifthly, first-time precision forging is carried out after acid pickling; sixthly, the pipe blank is internally bored and externally lathed, after annealing is conducted, multi-pass warm precision forging is conducted, the temperature ranges from 100 DEG C to 200 DEG C, the deformation of each pass is larger than or equal to 50%, and Q ranges from 0.8 to 1.5; seventhly, cold rolling is conducted after acid pickling and annealing; eighthly, acid pickling and vacuum annealing are conducted; and ninthly, magnetic polishing is conducted. By means of the method, the yield of the TA16 titanium alloy seamless tube can be increased by 40% or above.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy seamless pipe production, and in particular to a method for improving the yield rate of TA16 titanium alloy seamless pipes. Background Art

[0002] TA16 (Ti-2Al-2.5Zr) alloy is a medium-strength, high-plastic single-phase α titanium alloy with high specific strength, good corrosion resistance and excellent processability. The seamless pipes prepared from it are widely used in pipeline systems in the fields of aerospace, nuclear power, ships, etc. The processing technologies commonly used for TA16 titanium alloy seamless pipes are smelting, forging, extrusion, machining, cold rolling, annealing and other processes. However, due to the narrow temperature range of the high-temperature deformation process of TA16 titanium alloy materials and high resistance to low-temperature deformation, a certain yield rate is lost in forging, and the loss of machining materials before and after extrusion in the later stage is even greater, resulting in a low yield rate of existing processing methods, especially for TA16 titanium alloy seamless pipes with a diameter of no more than 18 mm, the yield rate is less than 30%. Summary of the invention

[0003] In order to solve the technical problem of low yield rate of existing TA16 titanium alloy seamless pipe processing methods, the present invention provides a method for improving the yield rate of TA16 titanium alloy seamless pipes.

[0004] The technical means adopted by the present invention are as follows:

[0005] A method for improving the yield rate of TA16 titanium alloy seamless pipe, specifically comprising the following steps:

[0006] Step 1: Pressing the raw material mixture into a plurality of electrode blocks, and then welding the plurality of electrode blocks to obtain a consumable electrode, wherein the raw material is added with an alloy element cerium having a mass percentage between 0.005% and 0.02%;

[0007] Step 2: Melting the consumable electrode to obtain a titanium alloy ingot, wherein the diameter of the titanium alloy ingot is ≤750 mm;

[0008] Step 3: directly heat the titanium alloy ingot at 1050°C to 1150°C for 4.5h to 7.5h without peeling, and hot-roll it into a titanium alloy bar with a diameter of ≥150mm; the deformation of each pass in the hot rolling process increases first and then decreases, and the maximum deformation does not exceed 50%; the deformation of the first and last passes in the hot rolling process is not more than 15%;

[0009] Step 4: The titanium alloy bar is obliquely rolled and punched into a rough tube with a deformation amount of 15% to 30%;

[0010] Step 5: After pickling the rough tube, perform the first fine forging, and the fine forging deformation is ≤10%;

[0011] Step 6: boring and turning the tube obtained in step 5, annealing and then performing multiple passes of warm forging, the temperature of the multiple passes of warm forging is 100°C to 200°C, the deformation amount of each pass is ≥50%, and the ratio Q of the relative wall reduction to the relative diameter reduction is 0.8 to 1.5;

[0012] Step 7: pickling and annealing the tube obtained in step 6 and then cold rolling to obtain a TA16 titanium alloy seamless tube semi-finished product, the outer diameter of the tube is ≤18mm, and the deformation amount of the last pass in the cold rolling process is ≤20%;

[0013] Step 8: pickling and vacuum annealing the seamless pipe semi-finished product obtained in step 7;

[0014] Step nine: Magnetic polishing is performed on the pipe obtained in step eight.

[0015] Furthermore, the raw materials also include titanium sponge, zirconium sponge, aluminum beans, titanium iron alloy and titanium dioxide.

[0016] Furthermore, step four specifically includes: polishing the surface of the titanium alloy rod, keeping it at 950°C to 1050°C for 2.0h to 3.5h, and then obliquely rolling and punching it into a rough tube, wherein the ratio of the rough tube diameter to the titanium alloy rod diameter is 1 to 1.2.

[0017] Furthermore, in step six, annealing is performed before each warm finish forging, the annealing temperature is 700° C. to 800° C., and the holding time is 1 h to 2.5 h.

[0018] Furthermore, if more than one cold rolling is performed in step seven, annealing is performed between two cold rolling passes, with the annealing temperature being 650° C. to 750° C. and the holding time being 1 to 2.5 h.

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

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

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

[0022] The method for improving the yield rate of TA16 titanium alloy seamless pipe provided by the present invention optimizes the composition of TA16 titanium alloy, improves the hot deformation ability of the ingot, and allows it to be directly hot-rolled into a rod blank, thereby replacing forging to improve the rod yield rate; as the hot rolling proceeds, the alloy structure is improved, the deformation ability is improved, and the deformation amount is gradually increased. The subsequent temperature rise pass due to hot rolling needs to reduce the deformation amount; oblique rolling and perforation are used instead of drilling before machining or extrusion to improve the yield rate of the rough pipe; the first pass of small deformation precision forging of the rough pipe improves the ovality of the rough pipe and improves the yield rate of subsequent internal boring and external turning; the subsequent multiple passes of warm precision forging and cold rolling basically do not lose material, the warm precision forging can increase the deformation amount and improve production efficiency, and the final cold rolling is beneficial to improving the accuracy of small-diameter seamless pipes, and the final seamless pipe yield rate can reach more than 40%; the final magnetic polishing is used to eliminate burrs that may exist on the inner and outer surfaces of small-diameter seamless pipes and improve the roughness, thereby improving the qualified product rate of the pipe.

[0023] Based on the above reasons, the present invention can be widely promoted in the field of titanium alloy seamless pipe production. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in combination with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention provides a method for improving the yield rate of TA16 titanium alloy seamless pipe, which specifically comprises the following steps:

[0026] Step 1: Pressing the raw material mixture into a plurality of electrode blocks, and then welding the plurality of electrode blocks to obtain a consumable electrode, wherein the raw material is added with an alloy element cerium in an amount of 0.005% to 0.02% by mass, and the addition of cerium is used to improve the plasticity and processability of the alloy;

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

[0028] Step 3: directly heat the titanium alloy ingot at 1050°C to 1150°C for 4.5h to 7.5h without peeling, and hot-roll it into a titanium alloy bar with a diameter of ≥150mm; the deformation of each pass in the hot rolling process increases first and then decreases, and the maximum deformation does not exceed 50%; the deformation of the first and last passes in the hot rolling process is not more than 15%;

[0029] Step 4: The titanium alloy bar is subjected to oblique rolling and punching to form a rough tube, and the deformation amount is 15% to 30%. The oblique rolling and punching is used instead of machining or drilling before extrusion to improve the rough tube yield rate;

[0030] Step 5: After pickling the rough tube, perform the first fine forging, with the fine forging deformation ≤10%, to improve the rough tube ovality and dimensional accuracy, and increase the rough tube yield rate;

[0031] Step 6: The tube blank obtained in step 5 is internally bored and externally turned, and then subjected to multiple passes of warm forging after annealing. The temperature of the multiple passes of warm forging is 100°C to 200°C, the deformation amount of each pass is ≥50%, and the ratio Q of the relative wall reduction to the relative diameter reduction is 0.8 to 1.5. The Q value is controlled in this range because too large a Q value will result in the tube obtaining an excessively strong radial texture after multiple passes of forging, and an excessively strong texture will result in cold rolling cracking, greatly reducing the yield rate;

[0032] Step 7: pickling and annealing the tube obtained in step 6 and then cold rolling to obtain a TA16 titanium alloy seamless tube semi-finished product, the outer diameter of the tube is ≤18mm, and the deformation amount of the last pass in the cold rolling process is ≤20%;

[0033] The multi-pass warm forging and cold rolling process in step 6 and step 7 basically does not lose material. The warm forging can increase the deformation and improve the production efficiency. The cold rolling is beneficial to improve the precision of the small diameter seamless pipe, so that the yield rate of the seamless pipe can reach more than 40%;

[0034] Step 8: pickling and vacuum annealing the seamless pipe semi-finished product obtained in step 7;

[0035] Step nine: The pipe obtained in step eight is subjected to magnetic polishing to eliminate burrs that may exist on the inner and outer surfaces of the small-diameter seamless pipe and improve the roughness, thereby increasing the qualified product rate of the pipe.

[0036] Furthermore, the raw materials also include titanium sponge, zirconium sponge, aluminum beans, titanium iron alloy and titanium dioxide.

[0037] Furthermore, step four specifically includes: polishing the surface of the titanium alloy rod, keeping it at 950°C to 1050°C for 2.0h to 3.5h, and then obliquely rolling and punching it into a rough tube, wherein the ratio of the rough tube diameter to the titanium alloy rod diameter is 1 to 1.2.

[0038] Furthermore, in step six, annealing is performed before each warm finish forging, the annealing temperature is 700° C. to 800° C., and the holding time is 1 h to 2.5 h.

[0039] Furthermore, if more than one cold rolling is performed in step seven, annealing is performed between two cold rolling passes, with the annealing temperature being 650° C. to 750° C. and the holding time being 1 to 2.5 h.

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

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

[0042] Example 1

[0043] This embodiment adopts the method of the present invention to produce a TA16 titanium alloy seamless pipe with a specification of Φ15×1.7 mm, which specifically includes the following steps:

[0044] Step 1: Pressing the raw material mixture into a plurality of electrode blocks, and then welding the plurality of electrode blocks to obtain a consumable electrode, wherein 0.01% of the alloy element cerium is added to the raw material;

[0045] Step 2: Smelt the consumable electrode twice in a vacuum consumable arc furnace to obtain a Φ730 mm titanium alloy ingot;

[0046] Step 3: The titanium alloy ingot is directly kept at 1150°C for 7.5h without peeling, and hot-rolled into titanium alloy bars. The deformation amount of the hot rolling is 13% in the first pass, 22% in the second pass, 36% in the third pass, 47% in the fourth pass, 36% in the fifth pass, 20% in the sixth pass, and 12% in the seventh pass, and finally a Φ235mm titanium alloy bar is obtained;

[0047] Step 4: The surface of the titanium alloy bar is polished to obtain a Φ225mm bar with a yield rate of 91.6%. After being kept at 1030°C for 2.5 hours, it is obliquely rolled and punched into a Φ240*48mm rough tube with a deformation of 27%;

[0048] Step 5: After pickling the rough tube, perform a fine forging to Φ230*46mm, and the fine forging deformation is 8%;

[0049] Step 6: The tube obtained in step 5 is internally bored and externally turned to Φ226*42mm, with a yield rate of 91.3%; after annealing, multiple passes of warm forging are performed, including: vacuum annealing at 780℃ for 2.5h, 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 2h, followed by warm forging at 150℃ to Φ112*14, with a deformation of 59.9% and a Q value of 1.4; vacuum annealing at 750℃ for 2h, followed by warm forging at 150℃ to Φ112*14, with a deformation of 59.9% and a Q value of 1.4 The precision forging at 150℃ is Φ75*9, Q value 1.1, deformation 56.7%; after vacuum annealing at 750℃ for 2h, the precision forging at 150℃ is Φ50*6, Q value 1.0, deformation 55.6%; after vacuum annealing at 750℃ for 2h, the precision forging at 150℃ is Φ32*4, Q value 0.9, deformation 57.6%; after vacuum annealing at 750℃ for 1.5h, the precision forging at 150℃ is Φ21*2.8, deformation 54.5%;

[0050] Step 7: The tube obtained in step 6 is pickled, vacuum annealed at 750°C for 1.5h, and then cold rolled to Φ16*2mm, and then vacuum annealed at 750°C for 2h and then cold rolled to Φ15*1.7mm, with a deformation of 19.3%;

[0051] Step 8: pickling and vacuum annealing at 700°C for 2h on the semi-finished seamless pipe obtained in step 7;

[0052] Step nine: Magnetic polishing is performed on the pipe obtained in step eight.

[0053] In this embodiment, after the tube is internally bored and externally turned, the yield rate of each fine forging and cold rolling is 95%. The yield rate of the produced TA16 titanium alloy seamless tube from the ingot casting is 91.6%*91.3%*95%*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 adopts the method of the present invention to produce a TA16 titanium alloy seamless pipe with a specification of Φ18×1.8 mm, which specifically includes the following steps:

[0056] Step 1: Pressing the raw material mixture into a plurality of electrode blocks, and then welding the plurality of electrode blocks to obtain a consumable electrode, wherein 0.006% of the alloy element cerium is added to the raw material;

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

[0058] Step 3: The titanium alloy ingot is kept at 1150°C for 5 hours without peeling, and hot-rolled into titanium alloy bars. The deformation of the first hot rolling pass is 11.6%, the deformation of the second pass is 27.6%, the deformation of the third pass is 36%, the deformation of the fourth pass is 43.8%, the deformation of the fifth pass is 37.3%, the deformation of the sixth pass is 29.1%, and the deformation of the seventh pass is 12.1%, and finally a Φ150mm titanium alloy bar is obtained;

[0059] Step 4: The surface of the titanium alloy bar is polished to obtain a Φ140 mm bar with a yield rate of 87.1%. After being kept at 1030°C for 2.5 hours, it is obliquely rolled and punched into a Φ150*30 mm rough tube with a deformation of 26.5%;

[0060] Step 5: After pickling the rough tube, perform a fine forging to Φ145*28mm, and the fine forging deformation is 9%;

[0061] Step 6: The tube obtained in step 5 is internally bored and externally turned into Φ141*24mm, with a yield rate of 85.7%; after annealing, multiple warm forgings are performed, including: vacuum annealing at 780℃ for 2.5h, followed by warm forging at 150℃ for Φ90*15, Q value 1.0, and deformation amount 59.9%; vacuum annealing at 780℃ for 2h, followed by warm forging at 150℃ for Φ63*8.5, Q value 1.4, and deformation amount 58.8%; after 750℃ vacuum annealing for 2h, it is Φ45*5 with Q value of 1.4 and deformation of 56.8%; after 750℃ vacuum annealing for 1.5h, it is Φ32*3 with Q value of 1.4 and deformation of 56.5%; after 750℃ vacuum annealing for 1.5h, it is Φ20*2 with Q value of 0.9 and deformation of 58.6%;

[0062] Step 7: The tube obtained in step 6 is pickled, vacuum annealed at 750°C for 1.5h, and then cold rolled to Φ18*1.8mm with a deformation of 19%;

[0063] Step 8: pickling and vacuum annealing at 700°C for 2h on the semi-finished seamless pipe obtained in step 7;

[0064] Step nine: Magnetic polishing is performed on the pipe obtained in step eight.

[0065] In this embodiment, after the tube is internally bored and externally turned, the yield rate of each fine forging and cold rolling is 95%. The yield rate of the produced TA16 titanium alloy seamless tube from the ingot casting is 87.1%*85.7%*95%*95%*95%*95%*95%*95%*95%*95%*95%*95%=47.3%. After magnetic polishing, the inner surface roughness is 250nm, the outer surface roughness is 200nm, 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 rate of TA16 titanium alloy seamless pipe, characterized in that: The specific steps include: Step 1: Pressing the raw material mixture into a plurality of electrode blocks, and then welding the plurality of electrode blocks to obtain a consumable electrode, wherein the raw material is added with an alloy element cerium having a mass percentage between 0.005% and 0.02%; Step 2: Melting the consumable electrode to obtain a titanium alloy ingot, wherein the diameter of the titanium alloy ingot is ≤750 mm; Step 3: directly heat the titanium alloy ingot at 1050°C to 1150°C for 4.5h to 7.5h without peeling, and hot-roll it into a titanium alloy bar with a diameter of ≥150mm; the deformation of each pass in the hot rolling process increases first and then decreases, and the maximum deformation does not exceed 50%; the deformation of the first and last passes in the hot rolling process is not more than 15%; Step 4: The titanium alloy bar is obliquely rolled and punched into a rough tube with a deformation amount of 15% to 30%; Step 5: After pickling the rough tube, perform the first fine forging, and the fine forging deformation is ≤10%; Step 6: boring and turning the tube obtained in step 5, annealing and then performing multiple passes of warm forging, the temperature of the multiple passes of warm forging is 100°C to 200°C, the deformation amount of each pass is ≥50%, and the ratio Q of the relative wall reduction to the relative diameter reduction is 0.8 to 1.5; Step 7: pickling and annealing the tube obtained in step 6 and then cold rolling to obtain a TA16 titanium alloy seamless tube semi-finished product, the outer diameter of the tube is ≤18mm, and the deformation amount of the last pass in the cold rolling process is ≤20%; Step 8: pickling and vacuum annealing the seamless pipe semi-finished product obtained in step 7; Step nine: Magnetic polishing is performed on the pipe obtained in step eight.

2. The method for improving the yield rate of TA16 titanium alloy seamless pipe according to claim 1, characterized in that: Step 4 specifically includes: polishing the surface of the titanium alloy rod, keeping it at 950°C to 1050°C for 2.0h to 3.5h, and then obliquely rolling and punching it into a rough tube, wherein the ratio of the rough tube diameter to the titanium alloy rod diameter is 1 to 1.

2.

3. The method for improving the yield rate of TA16 titanium alloy seamless pipe according to claim 1, characterized in that: In step six, annealing is performed before each warm finish forging, the annealing temperature is 700° C. to 800° C., and the holding time is 1 h to 2.5 h.

4. The method for improving the yield rate of TA16 titanium alloy seamless pipe according to claim 1, characterized in that: If more than one cold rolling is performed in step seven, annealing is performed between two cold rolling passes, with the annealing temperature being 650° C. to 750° C. and the holding time being 1 to 2.5 h.

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

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