Method for improving yield of TA18 titanium alloy seamless tube

Abstract

The invention provides a method for improving the yield of TA18 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 0.001 to 0.03 mass percent of alloy element yttrium into the raw materials; 2, a titanium alloy cast ingot is obtained through smelting; thirdly, the titanium alloy cast ingot is directly subjected to heat preservation for 4.5 h to 7.5 h at the temperature of 1050 DEG C to 1150 DEG C without scaling, and hot continuous rolling is conducted to form a titanium alloy bar; 4, performing cross piercing to form a tubular billet; fifthly, the tubular billet is subjected to one-pass cold rolling after being subjected to acid pickling; sixthly, the pipe blank is internally bored and externally lathed, and hot continuous rolling is conducted after annealing; seventhly, after acid pickling, the outer surface is polished, and the inner surface is honed; eighthly, cold rolling does not exceed four passes; ninthly, straightening, acid pickling and vacuum annealing are conducted; and tenthly, magnetic polishing is conducted. By means of the method, the yield of the TA18 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 TA18 titanium alloy seamless pipes. Background Art

[0002] TA18 titanium alloy seamless pipe has good room temperature mechanical properties and corrosion resistance, and is widely used in aerospace, oil fields and other fields, especially in aviation hydraulic pipeline systems. With the increase of hydraulic system pressure, the requirements for TA18 titanium alloy seamless pipes are getting higher and higher. At present, the processing technologies commonly used for TA18 titanium alloy seamless pipes are smelting, forging, extrusion, machining, cold rolling, annealing and other processes. Due to the narrow temperature range of the high-temperature deformation process of TA18 titanium alloy and the high resistance to low-temperature deformation, the above-mentioned processing methods are complicated, the forging and machining losses are large, and the yield rate is low. In particular, the diameter of seamless pipes for aviation hydraulic pipelines is less than 25mm. In order to reduce the number of cold rolling passes and the end reduction production cycle, the diameter of the extruded pipe is smaller, which greatly reduces the machining yield rate, resulting in a final yield rate of less than 30%. Summary of the invention

[0003] In order to solve the technical problem of low yield rate of existing TA18 titanium alloy seamless pipe processing methods, the present invention provides a method for improving the yield rate of TA18 titanium alloy seamless pipes.

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

[0005] A method for producing a TA18 titanium alloy seamless pipe specifically comprises 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 yttrium of between 0.001% and 0.03% by mass;

[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, the diameter of which is ≥200mm; 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 a cold rolling, the cold rolling deformation is ≤10%, and the rough tube ovality is improved;

[0011] Step 6: The tube obtained in step 5 is internally bored and externally turned, and then hot-rolled after annealing, with the starting rolling temperature being 300°C to 400°C, the deformation amount of each pass gradually decreasing, 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, the outer surface is polished and the inner surface is honed;

[0013] Step 8: cold rolling the tube obtained in step 7 into a titanium alloy seamless tube semi-finished product in no more than 4 passes, with the outer diameter of the tube being ≤20 mm and the deformation of the last pass being ≤20%;

[0014] Step nine: straightening, pickling and vacuum annealing the seamless pipe semi-finished product obtained in step eight;

[0015] Step 10: Magnetic polishing is performed on the pipe obtained in step 9.

[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 with a deformation amount of 15% to 30%, and a ratio of the rough tube diameter to the rod diameter of 1 to 1.2.

[0017] Furthermore, in step eight, annealing is performed before each cold rolling, the annealing temperature is 600° C. to 750° C., and the annealing temperature of each pass is not greater than the annealing temperature of the previous pass, and the holding time is 1 h to 2.5 h.

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

[0019] Furthermore, in step ten, the magnetic abrasive particles used in magnetic polishing are SiC with a particle size of 0.005 mm to 0.1 mm, and the roughness of the inner and outer surfaces of the pipe 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 rate of TA18 titanium alloy seamless pipes provided by the present invention optimizes the composition of TA18 titanium alloy, improves the thermal deformation capacity of the ingot, and enables 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 capacity is improved, and the deformation amount is gradually increased, and the subsequent temperature rise passes due to hot rolling need to reduce the deformation amount; oblique rolling and perforation are used instead of drilling before machining or extrusion to improve the yield rate of rough pipes; the first cold rolling of the rough pipe with a small deformation amount improves the ovality of the rough pipe and improves the yield rate of subsequent internal boring and external turning; the subsequent multiple cold rolling passes basically do not lose material, and the yield rate of seamless pipes can reach more than 40%; the final 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 pipes.

[0022] Based on the above reasons, the present invention can be widely promoted in the field of titanium alloy seamless pipe production. DETAILED DESCRIPTION

[0023] 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.

[0024] The present invention provides a method for producing a TA18 titanium alloy seamless pipe, which specifically comprises the following steps:

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

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

[0027] 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, the diameter of which is ≥200mm; 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%;

[0028] 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;

[0029] Step 5: After pickling the rough tube, perform a cold rolling, the cold rolling deformation is ≤10%, and the rough tube ovality is improved;

[0030] Step 6: The tube obtained in step 5 is internally bored and externally turned, and then hot-rolled after annealing, with the starting rolling temperature being 300°C to 400°C, the deformation amount of each pass gradually decreasing, 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, the outer surface is polished and the inner surface is honed;

[0032] Step 8: cold rolling the tube obtained in step 7 into a titanium alloy seamless tube semi-finished product in no more than 4 passes, with the outer diameter of the tube being ≤20 mm and the deformation of the last pass being ≤20%;

[0033] Step nine: straightening, pickling and vacuum annealing the seamless pipe semi-finished product obtained in step eight;

[0034] Step 10: The pipe obtained in step 9 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.

[0035] Furthermore, the raw materials also include titanium sponge, aluminum beans, titanium iron alloy, aluminum vanadium alloy and titanium dioxide.

[0036] 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 with a deformation amount of 15% to 30%, and a ratio of the rough tube diameter to the rod diameter of 1 to 1.2.

[0037] Furthermore, in step eight, annealing is performed before each cold rolling, the annealing temperature is 600° C. to 750° C., and the annealing temperature of each pass is not greater than the annealing temperature of the previous pass, and the holding time is 1 h to 2.5 h.

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

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

[0040] Example 1

[0041] This embodiment adopts the method of the present invention to produce a TA18 titanium alloy seamless pipe with a specification of Φ19×2.2 mm, which specifically includes the following steps:

[0042] 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 yttrium is added to the raw material;

[0043] Step 2: Smelt the consumable electrode three times in a vacuum consumable arc furnace to obtain a titanium alloy ingot with a diameter of Φ730 mm;

[0044] 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;

[0045] 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%;

[0046] Step 5: After pickling, the rough tube is cold rolled to Φ230*46mm, and the cold rolling deformation is 8%;

[0047] Step 6: The tube obtained in step 5 is internally bored and externally turned to Φ226*42mm, with a yield rate of 91.3%, and then hot-rolled after vacuum annealing at 400℃ for 2.5h, with an opening temperature of 350℃, a first pass deformation of 55.7%, a second pass deformation of 49%, a third pass deformation of 43.1%, a fourth pass deformation of 39.6%, a fifth pass deformation of 30.7%, a sixth pass deformation of 29.3%, and a seventh pass deformation of 13%, and finally a Φ52*5.5 tube is obtained with a yield rate of 90%;

[0048] Step 7: After pickling the tube obtained in step 6, the outer surface is polished and the inner surface is honed to obtain a Φ51.5*5 cold-rolled tube blank with a yield rate of 90.9%;

[0049] Step 8: The pipe obtained in step 7 is cold-rolled 4 times into a titanium alloy seamless pipe semi-finished product:

[0050] After 750℃ vacuum annealing for 2h, cold rolling is Φ42*3.2mm; after 750℃ vacuum annealing for 2h, cold rolling is Φ30*2.6mm; after 750℃ vacuum annealing for 1.5h, cold rolling is Φ22*2.3mm; after 750℃ vacuum annealing for 1.5h, cold rolling is Φ19*2.2mm, deformation is 18.4%;

[0051] Step nine: straighten, pickle and vacuum anneal at 600°C for 2h the seamless pipe semi-finished product obtained in step eight;

[0052] Step 10: Magnetic polishing is performed on the pipe obtained in step 9.

[0053] In this embodiment, after the tube is internally bored and externally turned, the yield rate of each cold rolling pass is 95%. The yield rate of the produced TA18 titanium alloy seamless tube from the ingot casting 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 adopts the method of the present invention to produce a TA18 titanium alloy seamless pipe with a specification of Φ14×1.7 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 0.008% of the alloy element yttrium is added to the raw material;

[0057] Step 2: Smelt the consumable electrode three times in a vacuum consumable arc furnace to obtain a titanium alloy ingot with a diameter of Φ690 mm;

[0058] Step 3: The titanium alloy ingot is kept at 1150°C for 7 hours without peeling, and hot-rolled into titanium alloy bars. The deformation of the first hot rolling pass is 14%, the deformation of the second hot rolling pass is 26%, the deformation of the third hot rolling pass is 39%, the deformation of the fourth hot rolling pass is 44.6%, the deformation of the fifth hot rolling pass is 28.8%, and the deformation of the sixth hot rolling pass is 7.3%, and finally a Φ260mm titanium alloy bar is obtained;

[0059] Step 4: The surface of the titanium alloy bar is polished to obtain a Φ250mm bar with a yield rate of 92.4%. After being kept at 1030°C for 2.5 hours, it is obliquely rolled and punched into a Φ275*50mm rough tube with a deformation of 28%;

[0060] Step 5: After pickling, the rough tube is cold-rolled to Φ265*47mm, and the cold-rolling deformation is 8.9%;

[0061] Step 6: The tube obtained in step 5 is internally bored and externally turned to Φ261*43mm, with a yield rate of 91.4%, and then hot-rolled after vacuum annealing at 450℃ for 2.5h, with an opening rolling temperature of 380℃, a first pass deformation of 57.9%, a second pass deformation of 53.4%, a third pass deformation of 49%, a fourth pass deformation of 42.7%, a fifth pass deformation of 34%, a sixth pass deformation of 29.4%, a seventh pass deformation of 26.4%, and an eighth pass deformation of 14.9%, and finally a Φ46*3.7 tube is obtained with a yield rate of 90%;

[0062] Step 7: After pickling the tube obtained in step 6, the outer surface is polished and the inner surface is honed to obtain a Φ45.5*3.2 cold-rolled tube blank with a yield rate of 86.4%;

[0063] Step 8: The pipe obtained in step 7 is cold-rolled 4 times into a titanium alloy seamless pipe semi-finished product:

[0064] After 750℃ vacuum annealing for 2h, cold rolling is Φ30*2.6mm; after 750℃ vacuum annealing for 2h, cold rolling is Φ20*2.3mm; after 750℃ vacuum annealing for 1.5h, cold rolling is Φ15*2mm; after 750℃ vacuum annealing for 1.5h, cold rolling is Φ14*1.7mm, deformation is 19.6%;

[0065] Step nine: straighten, pickle and vacuum anneal at 550° C. for 2 h on the seamless pipe semi-finished product obtained in step eight;

[0066] Step 10: Magnetic polishing is performed on the pipe obtained in step 9.

[0067] In this embodiment, after the tube is internally bored and externally turned, the yield rate of each cold rolling pass is 95%. The yield rate of the produced TA18 titanium alloy seamless tube from the ingot casting is 92.4%*91.4%*90%*86.4%*95%*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, 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 TA18 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 yttrium of between 0.001% and 0.03% by mass; 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, the diameter of which is ≥200mm; 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 a cold rolling, the cold rolling deformation is ≤10%, and the rough tube ovality is improved; Step 6: The tube obtained in step 5 is internally bored and externally turned, and then hot-rolled after annealing, with the starting rolling temperature being 300°C to 400°C, the deformation amount of each pass gradually decreasing, 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, the outer surface is polished and the inner surface is honed; Step 8: cold rolling the tube obtained in step 7 into a titanium alloy seamless tube semi-finished product in no more than 4 passes, with the outer diameter of the tube being ≤20 mm and the deformation of the last pass being ≤20%; Step nine: straightening, pickling and vacuum annealing the seamless pipe semi-finished product obtained in step eight; Step 10: Magnetic polishing is performed on the pipe obtained in step 9.

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

2.

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

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

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