CN117548520B - Titanium alloy seamless tube and method for improving plasticity of thin-wall titanium alloy seamless tube - Google Patents
Titanium alloy seamless tube and method for improving plasticity of thin-wall titanium alloy seamless tube Download PDFInfo
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- 229910001069 Ti alloy Inorganic materials 0.000 title claims abstract description 233
- 238000000034 method Methods 0.000 title claims abstract description 76
- 238000005097 cold rolling Methods 0.000 claims abstract description 160
- 238000000137 annealing Methods 0.000 claims abstract description 103
- 230000009467 reduction Effects 0.000 claims abstract description 29
- 238000005096 rolling process Methods 0.000 claims abstract description 22
- 238000003723 Smelting Methods 0.000 claims abstract description 17
- 238000004321 preservation Methods 0.000 claims abstract description 14
- 230000007704 transition Effects 0.000 claims abstract description 14
- 238000004381 surface treatment Methods 0.000 claims abstract description 11
- 239000002994 raw material Substances 0.000 claims abstract description 7
- 238000001125 extrusion Methods 0.000 claims description 35
- 238000000227 grinding Methods 0.000 claims description 22
- 238000005498 polishing Methods 0.000 claims description 13
- 230000009466 transformation Effects 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 12
- 229910045601 alloy Inorganic materials 0.000 claims description 10
- 239000000956 alloy Substances 0.000 claims description 10
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 10
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 10
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 8
- 229910052961 molybdenite Inorganic materials 0.000 claims description 5
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 claims description 5
- 229910052982 molybdenum disulfide Inorganic materials 0.000 claims description 5
- 230000008859 change Effects 0.000 claims description 3
- 238000010622 cold drawing Methods 0.000 claims description 3
- 239000003795 chemical substances by application Substances 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims 1
- 230000008569 process Effects 0.000 description 41
- 230000007547 defect Effects 0.000 description 12
- 230000009286 beneficial effect Effects 0.000 description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 238000005242 forging Methods 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 238000005336 cracking Methods 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 238000005554 pickling Methods 0.000 description 4
- 229910052719 titanium Inorganic materials 0.000 description 4
- 239000010936 titanium Substances 0.000 description 4
- HIMLGVIQSDVUJQ-UHFFFAOYSA-N aluminum vanadium Chemical compound [Al].[V] HIMLGVIQSDVUJQ-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 238000005553 drilling Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000002918 waste heat Substances 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000014509 gene expression Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 230000001050 lubricating effect Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000007517 polishing process Methods 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000009897 systematic effect Effects 0.000 description 1
- 238000000844 transformation Methods 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B23/00—Tube-rolling not restricted to methods provided for in only one of groups B21B17/00, B21B19/00, B21B21/00, e.g. combined processes planetary tube rolling, auxiliary arrangements, e.g. lubricating, special tube blanks, continuous casting combined with tube rolling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C23/00—Extruding metal; Impact extrusion
- B21C23/02—Making uncoated products
- B21C23/04—Making uncoated products by direct extrusion
- B21C23/08—Making wire, bars, tubes
- B21C23/085—Making tubes
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L9/00—Rigid pipes
- F16L9/02—Rigid pipes of metal
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Extrusion Of Metal (AREA)
Abstract
The invention belongs to the technical field of titanium alloy, and particularly relates to a titanium alloy seamless tube and a method for improving plasticity of a thin-wall titanium alloy seamless tube, wherein the method comprises the following steps: s10, smelting raw materials to obtain a titanium alloy cast ingot, and measuring the phase transition point temperature of the cast ingot; s20, perforating an unworked titanium alloy cast ingot into a blank pipe; s30, extruding the hollow billet into a hollow billet; s40, performing surface treatment on the hollow tube blank after preliminary cold rolling to obtain a cold-rolled tube blank; s50, performing multi-pass cold rolling on the cold-rolled tube blank to obtain a titanium alloy tube, and performing vacuum annealing on the titanium alloy tube subjected to each pass of cold rolling, wherein the deformation rate of each pass of cold rolling is more than or equal to 70%, the wall reduction of each pass is controlled to be more than or equal to 1.50, the rolling speed of each pass is controlled to be more than or equal to 120 times/min, the vacuum annealing temperature of the titanium alloy tube obtained by cold rolling is determined according to the phase transition point temperature and the cold rolling deformation rate, and the annealing heat preservation time is determined according to the wall thickness of the titanium alloy tube obtained by cold rolling.
Description
Technical Field
The invention relates to the technical field of titanium alloy, in particular to a titanium alloy seamless tube and a method for improving plasticity of a thin-wall titanium alloy seamless tube.
Background
The plasticity is an important index for measuring the performance of a titanium alloy pipe product, the plasticity index is generally described by the elongation of the titanium alloy pipe product, and in general, the larger the elongation of the product is, the better the plasticity of the product is. However, the existing titanium alloy pipe is not subjected to systematic optimization aiming at the improvement of the plasticity of the titanium alloy pipe in the aspects of raw material selection, component design, thermal deformation process, cold rolling deformation process, heat treatment process, internal and external surface treatment process, grain orientation regulation and control and the like, so that the plasticity of the thin-wall titanium alloy pipe is poor.
There are several reasons why the thin-walled titanium alloy tube finished product has poor plasticity, for example: firstly, the raw materials of the titanium alloy pipe contain more impurity elements; secondly, the crack defect of the inner surface and the outer surface of the titanium alloy pipe; thirdly, the crystal grains are large due to unreasonable rolling process and annealing process, and fourthly, the grain orientation distribution of the titanium alloy pipe is unreasonable.
Based on this, a method for improving the plasticity of the thin-wall titanium alloy seamless tube needs to be proposed.
Disclosure of Invention
In order to solve the technical problems, the invention provides a titanium alloy seamless tube and a method for improving the plasticity of a thin-wall titanium alloy seamless tube, which can solve the technical problem that the existing thin-wall titanium alloy seamless tube is poor in plasticity.
On one hand, the embodiment of the invention discloses a method for improving the plasticity of a thin-wall titanium alloy seamless pipe, which comprises the following steps:
s10, smelting raw materials to obtain a titanium alloy ingot, and measuring the phase transition point temperature of the titanium alloy ingot;
S20, heating and preserving heat of the titanium alloy cast ingot which is not forged, and then performing oblique rolling perforation to form a blank pipe;
s30, heating the hollow billet, extruding the heated hollow billet into a hollow billet, controlling the extrusion deformation rate to be more than or equal to 85 percent, annealing the hollow billet, and controlling the recrystallized grain diameter of the annealed hollow billet to be less than or equal to 5 microns;
S40, performing surface treatment on the annealed hollow tube blank after preliminary cold rolling to obtain a cold-rolled tube blank;
S50, performing multi-pass cold rolling on the cold-rolled tube blank to obtain a titanium alloy tube, and performing vacuum annealing on the titanium alloy tube subjected to each pass of cold rolling, wherein the deformation rate of each pass of cold rolling is controlled to be more than or equal to 70%, the wall reduction of each pass of cold-rolled tube blank is controlled to be more than or equal to 1.50, the rolling speed of each pass of cold-rolled tube blank is controlled to be more than or equal to 120 times/min, the vacuum annealing temperature of the titanium alloy tube obtained by each pass of cold rolling is determined according to the phase transition point temperature and the deformation rate of each pass of cold rolling, and the annealing heat preservation time is determined according to the wall thickness of the titanium alloy tube obtained by each pass of cold rolling.
According to one embodiment of the invention, in the step S10, titanium sponge and intermediate alloy with Brinell hardness HB less than or equal to 85 are adopted, and are smelted by a twice vacuum consumable electrode arc furnace to obtain a titanium alloy cast ingot.
According to one embodiment of the present invention, in the step S20, the titanium alloy ingot is heated to 80 ℃ above the transformation point temperature, and is kept for 1 to 2 hours.
According to one embodiment of the present invention, in the step S30, the hollow shell is heated to 60 ℃ below the phase transition point temperature, the preheating temperature of the extrusion die is controlled to 390-410 ℃, the extrusion speed is controlled to 55-65 mm/S, the length of the extruded hollow shell is not less than 15 times the length of the hollow shell, the annealing temperature of the hollow shell is 90 ℃ below the phase transition point temperature, and the annealing heat preservation time is 90-110 minutes.
According to one embodiment of the present invention, in the step S40, performing the preliminary cold rolling includes: performing 1-pass cold rolling on the hollow tube blank on a three-roller cold pilger mill to prepare a titanium alloy tube intermediate blank, and controlling the cold rolling deformation rate to be less than or equal to 20%; the surface treatment includes: performing internal boring, external grinding and external polishing on the intermediate billet of the titanium alloy pipe twice to prepare a cold-rolled pipe billet; and vacuum annealing the surface-treated cold-rolled tube blank.
According to one embodiment of the present invention, in the step S40, two times of internal boring are performed by using a YG8 cemented carbide tool, the vehicle speed is controlled to be 18-21 m/min, and the feeding amount of the second time of internal boring is controlled to be 1/6 of the feeding amount of the first time of internal boring; and/or the external grinding adopts a silicon carbide grinding wheel centerless grinding, and the external polishing adopts a green silicon carbide grinding belt with granularity more than or equal to 400 meshes for polishing; and/or the annealing temperature of the cold-rolled tube blank for vacuum annealing is (T/2+320×ε) DEG C, the annealing heat-preserving time is (40×S) minutes, wherein T is the transformation point temperature, ε is the cold-rolling deformation rate of 1-pass cold rolling, and S is the wall thickness of the cold-rolled tube blank, and the unit is mm.
According to one embodiment of the present invention, in the step S50, the vacuum annealing temperature of the titanium alloy tube obtained by each cold rolling pass is (T/2+320×ε) deg.c, and the annealing holding time is (40×s) minutes, where T is the transformation point temperature, ε is the cold rolling deformation rate of each cold rolling pass, and S is the wall thickness of the titanium alloy tube after each cold rolling pass, and the unit is mm.
According to one embodiment of the present invention, in the step S50, the titanium alloy tube is drawn on a drawing machine before the final 1-pass cold rolling, the inside and outside surfaces of the titanium alloy tube are lubricated by using a MoS2 aqueous agent before the drawing, and vacuum annealing is performed after the drawing, wherein the vacuum annealing temperature is (T/2+320×epsilon) deg.c, and the annealing holding time is (40×s) minutes, where T is the transformation point temperature, and epsilon is the drawing deformation rate.
According to one embodiment of the invention, the extrusion deformation rate, the cold rolling deformation rate per pass, the drawing deformation rate and the wall reduction per pass are calculated according to the following formula:
ε=（（D1-S1）*S1-（D2-S2）*S2）/（（D1-S1）*S1）
K=（S1-S2）*D1/（D1-D2）*S1
Wherein epsilon is extrusion deformation rate, cold rolling deformation rate or drawing deformation rate of each pass; k is the wall reduction amount of each pass; d1 and S1 are respectively the outer diameter and the wall thickness of the extruded, cold-rolled or drawn front pipe in each pass; d2 and S2 are the outer diameter and wall thickness of the tube after extrusion, cold rolling or drawing each pass, respectively.
On the other hand, the embodiment of the invention also discloses a titanium alloy seamless pipe, which is obtained by adopting the method of any one of the embodiments, wherein the titanium alloy seamless pipe is a TA18 titanium alloy seamless pipe, the wall thickness of the titanium alloy seamless pipe is less than or equal to 1mm, and the elongation of the titanium alloy seamless pipe is more than or equal to 26%.
By adopting the technical scheme, the invention has at least the following beneficial effects:
According to the method for improving the plasticity of the thin-wall titanium alloy seamless pipe, the conventional process of forging the cast ingot into the round rod through multiple fires, drilling, internally boring and externally turning the round rod into the hollow rod, and extruding the hollow rod into the hollow pipe blank is not adopted, but the cast ingot is directly extruded into the hollow pipe blank through the oblique rolling perforation without forging, so that the working procedure is greatly reduced, the yield is improved, the large deformation rate of the oblique rolling perforation is superposed, the superposition extrusion large deformation rate is beneficial to thinning the pipe blank crystal grains, the texture orientation of the pipe blank is optimized, the plasticity of a finished product of the titanium alloy pipe is improved, the recrystallized crystal grain diameter of the hollow pipe blank after annealing is controlled to be less than or equal to 5 microns, and the preparation of tissues can be made for the subsequent cold rolling procedure, so that the plasticity of the finished product of the titanium alloy pipe is beneficial to further improvement;
According to the invention, the hollow tube blank wire is subjected to preliminary cold rolling on the cold tube mill, so that the internal diameter of a regular tube blank is facilitated, the wall thickness deviation is reduced, the yield of an internal boring process is improved, and oxide layers and gas permeation layers on the inner surface and the outer surface of a titanium alloy tube can be removed through surface treatment, so that the defects of cracks and the like on the inner surface and the outer surface of the titanium alloy tube in the subsequent cold rolling process are prevented, and the plasticity of a titanium alloy finished tube is facilitated to be improved;
The cold-rolled tube blank is subjected to multi-pass cold rolling, and each pass of cold rolling adopts a large cold rolling deformation rate, a large wall reduction amount and a high rolling speed, so that cold rolling defects are greatly reduced, and the plasticity of a titanium alloy tube finished product is ensured to be improved; by controlling reasonable annealing process parameters, the titanium alloy tube can be ensured to be fully recovered and recrystallized, the plasticity is improved, and the cracking defect of the titanium alloy tube in the subsequent cold rolling deformation process is reduced.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a method for improving the plasticity of a thin-walled titanium alloy seamless tube according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
It should be noted that, in the embodiments of the present invention, all the expressions "first" and "second" are used to distinguish two entities with the same name but different entities or different parameters, and it is noted that the "first" and "second" are only used for convenience of expression, and should not be construed as limiting the embodiments of the present invention, and the following embodiments are not described one by one.
According to a first aspect of the present invention, as shown in fig. 1, an embodiment of the present invention discloses a method for improving plasticity of a thin-walled titanium alloy seamless tube, comprising the steps of:
s10, smelting raw materials to obtain a titanium alloy ingot, and measuring the phase transition point temperature of the titanium alloy ingot;
s20, heating and preserving heat of a titanium alloy cast ingot which is not forged, and then performing oblique rolling perforation to form a blank pipe;
S30, heating the hollow billet, extruding the hollow billet into a hollow billet, controlling the extrusion deformation rate to be more than or equal to 85 percent, annealing the hollow billet, and controlling the recrystallized grain diameter of the hollow billet after annealing to be less than or equal to 5 microns;
s40, performing surface treatment on the annealed hollow tube blank after preliminary cold rolling to obtain a cold-rolled tube blank;
s50, performing multi-pass cold rolling on the cold-rolled tube blank to obtain a titanium alloy tube, and performing vacuum annealing on the titanium alloy tube subjected to each pass of cold rolling, wherein the deformation rate of each pass of cold rolling is controlled to be more than or equal to 70%, the wall reduction of each pass of cold rolling is controlled to be more than or equal to 1.50, the rolling speed of each pass of cold rolling is controlled to be more than or equal to 120 times/min, the vacuum annealing temperature of the titanium alloy tube obtained by each pass of cold rolling is determined according to the phase change point temperature and the deformation rate of each pass of cold rolling, and the annealing heat preservation time is determined according to the wall thickness of the titanium alloy tube obtained by each pass of cold rolling.
In some embodiments, in step S20: perforating a titanium alloy cast ingot on a two-roller oblique rolling perforating machine to form a blank pipe; in some embodiments of the present invention, in step S50: and cold rolling the cold-rolled tube blank on a two-roller cold tube mill for 3-5 times to obtain the titanium alloy tube.
According to the method for improving the plasticity of the thin-wall titanium alloy seamless pipe, the conventional process of forging the cast ingot into a round rod through multiple fires, drilling, internally boring and externally turning the round rod into a hollow rod, and extruding the hollow rod into a pipe blank is not adopted, but the process of directly extruding the cast ingot into a hollow pipe blank through oblique rolling perforation without forging, so that the working procedures are greatly reduced, the yield is improved, the large deformation rate of the oblique rolling perforation is superposed, the superposition extrusion large deformation rate is beneficial to refining the pipe blank crystal grains, the texture orientation of the pipe blank is optimized, the plasticity of a finished titanium alloy pipe product is improved, the recrystallized crystal grain diameter of the hollow pipe blank after annealing is controlled to be less than or equal to 5 microns, and the preparation of tissues can be made for the subsequent cold rolling process, so that the plasticity of the titanium alloy finished pipe product is further improved;
According to the invention, the hollow tube blank wire is subjected to preliminary cold rolling on the cold tube mill, so that the internal diameter of a regular tube blank is facilitated, the wall thickness deviation is reduced, the yield of an internal boring process is improved, and oxide layers and gas permeation layers on the inner surface and the outer surface of a titanium alloy tube can be removed through surface treatment, so that the defects of cracks and the like on the inner surface and the outer surface of the titanium alloy tube in the subsequent cold rolling process are prevented, and the plasticity of a titanium alloy finished tube is facilitated to be improved;
The cold-rolled tube blank is subjected to multi-pass cold rolling, and each pass of cold rolling adopts a large cold rolling deformation rate, a large wall reduction amount and a high rolling speed, so that cold rolling defects are greatly reduced, and the plasticity of a titanium alloy tube finished product is ensured to be improved; by controlling reasonable annealing process parameters, the titanium alloy tube can be ensured to be fully recovered and recrystallized, the plasticity is improved, and the cracking defect of the titanium alloy tube in the subsequent cold rolling deformation process is reduced.
In some embodiments, in step S10, a titanium alloy ingot is obtained by smelting sponge titanium with Brinell hardness HB less than or equal to 85 and a master alloy in a twice vacuum consumable arc furnace, and the N content of the component of the titanium alloy ingot is controlled to be less than or equal to 0.001 percent. In some embodiments, in step S10, the master alloy is an aluminum-vanadium master alloy, and the titanium alloy ingot formed by the first smelting is turned around in the second smelting of the two vacuum consumable arc furnace smelting and then is smelted. The plasticity of the titanium alloy finished tube is ensured by selecting the titanium sponge with the Brinell hardness HB less than or equal to 85; the conventional three-time vacuum consumable arc furnace smelting is changed into two-time vacuum consumable arc furnace smelting, so that the situation that the oxygen and nitrogen contents in the titanium alloy cast ingot are increased due to the fact that smelting times are high is avoided, the oxygen and nitrogen contents in the titanium alloy cast ingot can be controlled, the uniformity of the components of the titanium alloy cast ingot is improved, and the uniformity of the components of the titanium alloy tube is guaranteed; the titanium alloy cast ingot formed by the first smelting is turned around in the second smelting, so that the uniformity of the components of the titanium alloy cast ingot is improved, and the plasticity of a titanium alloy finished tube is further improved.
In some embodiments, in step S20, the titanium alloy ingot is heated to 80 ℃ above the transformation point temperature and held for 1-2 hours.
In some embodiments, in step S30, the hollow billet is heated to 60 ℃ below the phase transition point temperature, the preheating temperature of the extrusion die is controlled to 390-410 ℃, the extrusion speed is controlled to 55-65 mm/S, the length of the extruded hollow billet is more than or equal to 15 times of the length of the hollow billet, the annealing temperature of the hollow billet in the resistance furnace is 90 ℃ below the phase transition point temperature, the annealing heat preservation time is 90-110 minutes, and then the hollow billet is cooled to 690-710 ℃ in the resistance furnace and is straightened by using waste heat after discharging. In the embodiment, the large deformation rate of the oblique rolling perforation is added to the large deformation rate of extrusion, so that the grain of the tube blank is thinned, the texture orientation of the tube blank is optimized, and the plasticity of a finished titanium alloy tube product is improved; the reasonable annealing process after extrusion is beneficial to controlling the recrystallized grain diameter of the hollow tube blank to be less than or equal to 5 microns, making tissue preparation for the subsequent cold rolling process and improving the plasticity of the finished titanium alloy tube product.
In some embodiments, in step S30, the extrusion die preheating temperature is controlled to 400℃and the extrusion speed is controlled to 60mm/S, the hollow shell is annealed in a resistance furnace for a holding time of 100 minutes, and then cooled to 700℃in the resistance furnace.
In some embodiments, in step S40, performing the preliminary cold rolling includes: performing 1-pass cold rolling on the hollow tube blank on a three-roller cold pilger mill to prepare a titanium alloy tube intermediate blank, and controlling the cold rolling deformation rate to be less than or equal to 20%; the surface treatment includes: performing internal boring, external grinding and external polishing on the intermediate billet of the titanium alloy pipe twice to prepare a cold-rolled pipe billet; and vacuum annealing the surface-treated cold-rolled tube blank.
In some embodiments, in step S40, two internal boring uses YG8 cemented carbide tools, the vehicle speed is controlled to 18-21 m/min, and the second internal boring feed is controlled to be 1/6 of the first internal boring feed. In the embodiment, the oxidation layer and the gas permeation layer on the inner surface of the intermediate blank of the titanium alloy tube can be completely removed by adopting the internal boring process parameters.
In some embodiments, in step S40, the outer mill is a centerless silicon carbide abrasive wheel and the outer polish is a green silicon carbide abrasive belt having a particle size of 400 mesh or greater. In the embodiment, the oxide layer and the gas permeation layer on the outer surface of the intermediate blank of the titanium alloy tube can be completely removed, so that the defects of cracks and the like on the inner surface and the outer surface of the titanium alloy tube in the subsequent cold rolling process are prevented, and the plasticity of a finished titanium alloy tube product is improved.
In some embodiments, in step S40, the vacuum annealing is performed at an annealing temperature (T/2+320×ε) DEG C and an annealing hold time (40×S) minutes, where T is the transformation point temperature, ε is the cold rolling deformation of 1 cold rolling pass, and S is the wall thickness of the cold rolled tube in mm.
In some embodiments, in step S50, the vacuum annealing temperature of the titanium alloy tube obtained by each cold rolling pass is (T/2+320×ε) DEG C, and the annealing hold time is (40×S) minutes, wherein T is the transformation point temperature, ε is the cold rolling deformation rate of each cold rolling pass, and S is the wall thickness of the titanium alloy tube after each cold rolling pass, and the unit is mm. The vacuum annealing temperature is calculated according to the transformation point temperature and the cold rolling deformation rate of the titanium alloy cast ingot, the annealing heat preservation time is calculated according to the wall thickness of the titanium alloy tube, the titanium alloy tube can be ensured to fully recover and recrystallize by controlling reasonable annealing process parameters, the plasticity is improved, the cracking defect of the titanium alloy tube in the subsequent cold rolling deformation process is reduced, and the plasticity of the titanium alloy finished tube is improved.
In some embodiments, in step S50, the titanium alloy tube is drawn on a drawing machine before the final 1-pass cold rolling, the inner and outer surfaces of the titanium alloy tube are lubricated by MoS2 aqueous solution before drawing, and vacuum annealing is performed after drawing, wherein the vacuum annealing temperature is (T/2+320×epsilon) deg.c, and the annealing holding time is (40×s) minutes, where T is the phase transition point temperature, and epsilon is the drawing deformation rate. In the embodiment, the grain orientation of the titanium alloy tube can be flexibly adjusted by adopting a mode of combining the two-roller cold rolling and the drawing deformation process, thereby being beneficial to improving the plasticity of the titanium alloy finished tube.
In some embodiments, the extrusion deformation rate, the cold rolling deformation rate per pass, the drawing deformation rate, and the wall reduction per pass are calculated according to the following formulas:
ε=（（D1-S1）*S1-（D2-S2）*S2）/（（D1-S1）*S1）
K=（S1-S2）*D1/（D1-D2）*S1
Wherein epsilon is extrusion deformation rate, cold rolling deformation rate or drawing deformation rate of each pass; k is the wall reduction amount of each pass; d1 and S1 are respectively the outer diameter and the wall thickness of the extruded, cold-rolled or drawn front pipe in each pass; d2 and S2 are the outer diameter and wall thickness of the tube after extrusion, cold rolling or drawing each pass, respectively.
Specifically, in the above formula: for example, in step S30 of some embodiments, epsilon is the extrusion deformation ratio, D1 and S1 are the outer diameter and wall thickness of the hollow shell, respectively, and D2 and S2 are the outer diameter and wall thickness of the hollow shell, respectively; in step S40 of some embodiments, epsilon is the cold rolling deformation ratio of the preliminary cold rolling, D1 and S1 are the outer diameter and wall thickness of the hollow shell, respectively, and D2 and S2 are the outer diameter and wall thickness of the intermediate blank of the titanium alloy tube obtained by the preliminary cold rolling, respectively; in step S50 of some embodiments, epsilon is the cold rolling deformation ratio, D1 and S1 are the outer diameter and the wall thickness of the cold rolled tube blank or the titanium alloy tube before each pass of cold rolling, respectively, and D2 and S2 are the outer diameter and the wall thickness of the titanium alloy tube after each pass of cold rolling, respectively; in step S50 of some embodiments, epsilon is the drawing deformation ratio, D1 and S1 are the outer diameter and wall thickness of the titanium alloy tube before drawing, respectively, and D2 and S2 are the outer diameter and wall thickness of the titanium alloy tube after drawing, respectively; wherein, the units of D1, S1, D2 and S2 are all mm.
According to a second aspect of the invention, an embodiment of the invention provides a titanium alloy seamless tube, which is obtained by the method as described in any of the above embodiments, wherein the titanium alloy seamless tube is a TA18 titanium alloy seamless tube, the wall thickness of the titanium alloy seamless tube is less than or equal to 1mm, and the elongation of the titanium alloy seamless tube is less than or equal to 26%.
The invention will now be described with reference to specific examples, which are intended to be illustrative only and not limiting in any way.
Example 1
This example produced TA18 thin-walled titanium alloy seamless tubes of gauge Φ12X0.6 mm (i.e., 12mm outside diameter, 0.6mm wall thickness).
The preparation process adopted in this example is as follows:
1. Adopting sponge titanium with Brinell hardness HB of 84 and aluminum vanadium intermediate alloy, smelting by a vacuum consumable arc furnace for two times to obtain a round TA18 titanium alloy cast ingot with phi 230 (diameter of 230 mm), wherein the content of N (mass fraction) of the titanium alloy cast ingot is 0.001%, and determining the phase transition point temperature T of the titanium alloy cast ingot to be 922 ℃;
2. Heating a phi 230 round TA18 titanium alloy cast ingot to 1002 ℃ (the calculation formula is (922+80) DEG C) in a resistance furnace, preserving heat for 1 hour, discharging, and perforating on a two-roll oblique rolling perforating machine to obtain a phi 220 multiplied by 50 (the outer diameter is 220mm, and the wall thickness is 50 mm) capillary;
3. Heating a phi 220 multiplied by 50 hollow billet to 862 ℃ (the calculation formula is (922-60)) DEG C, extruding the hollow billet into a phi 57 multiplied by 12 hollow billet (the outer diameter is 57mm and the wall thickness is 12 mm) on a horizontal extruder, preheating an extrusion die to 400 ℃, controlling the extrusion speed to be 60mm/s, calculating the length of the extruded hollow billet to be 15.74 times of the length of the hollow billet, obtaining the extrusion deformation rate to be 93.6% according to the following calculation formula (1), annealing the phi 57 multiplied by 12 hollow billet in a resistance furnace, annealing at 832 ℃ (the calculation formula is (922-90)) DEG C, cooling the hollow billet to 700 ℃ in the resistance furnace after the annealing heat preservation time is 100 minutes, and straightening the hollow billet by using the waste heat after the annealing, wherein the grain diameter of the recrystallized grain of the annealed hollow billet is less than or equal to 5 microns;
ε=（（D1-S1）*S1-（D2-S2）*S2）/（（D1-S1）*S1） （1）
In equation (1) of this flow: epsilon is extrusion deformation rate, D1 and S1 are respectively the outer diameter and the wall thickness of a hollow billet, D2 and S2 are respectively the outer diameter and the wall thickness of a hollow billet, and the units of D1, S1, D2 and S2 are all mm;
4. Pickling a phi 57 multiplied by 12 hollow tube blank, then performing 1-pass cold rolling on a three-roller cold pilger mill LD60 to obtain a phi 54 multiplied by 11 (with an outer diameter of 54mm and a wall thickness of 11 mm) titanium alloy tube intermediate blank, calculating according to a calculation formula (1) in the above procedure 3 to obtain a cold rolling deformation rate of 12.4%, and calculating according to the following calculation formula (2) to obtain a wall reduction of 1.58; sequentially carrying out internal boring, external grinding and external polishing on a phi 54 multiplied by 11 titanium alloy pipe intermediate blank twice to obtain a phi 52 multiplied by 8.6 (with an external diameter of 52mm and a wall thickness of 8.6 mm) cold-rolled pipe blank, and then carrying out vacuum annealing, wherein the two internal boring adopts YG8 hard alloy cutters, the speed of the internal boring is 20 m/min, the feeding amount of the first internal boring is 0.6mm, the feeding amount of the second internal boring is 0.1mm, the external grinding adopts a silicon carbide grinding wheel centerless grinding, and the external polishing adopts a green silicon carbide grinding belt with granularity more than or equal to 400 meshes; the annealing temperature of the cold-rolled tube blank for vacuum annealing is 501 ℃ (the calculation formula is (922/2+320 multiplied by 0.124) DEGC), the annealing heat-preserving time is 344 minutes (the calculation formula is (40 multiplied by 8.6) minutes);
K=（S1-S2）*D1/（D1-D2）*S1（2）
in equations (1) and (2) of this flow: epsilon is the cold rolling deformation rate of the primary cold rolling, K is the pass wall reduction, D1 and S1 are the outer diameter and the wall thickness of the hollow pipe blank respectively, D2 and S2 are the outer diameter and the wall thickness of a titanium alloy pipe intermediate blank obtained by the primary cold rolling respectively, and the units of D1, S1, D2 and S2 are all mm;
5. Cold rolling the phi 52 multiplied by 8.6 cold-rolled tube blank subjected to vacuum annealing into a phi 33 multiplied by 3.8 (with an outer diameter of 33mm and a wall thickness of 3.8 mm) titanium alloy tube on a two-roll cold-rolling tube mill LG40, and then performing vacuum annealing, wherein the cold-rolled deformation rate of the pass is 70.3% according to a calculation formula (1) in the above procedure 3, the wall reduction of the pass is 1.53 according to a calculation formula (2) in the above procedure 4, the vacuum annealing temperature of the titanium alloy tube obtained by the cold-rolled pass is 686 ℃ (the calculation formula is (922/2+320 multiplied by 0.703) DEG C, and the annealing heat-preserving time is 152 minutes (the calculation formula is (40 multiplied by 3.8)) min);
in equations (1) and (2) of this flow: epsilon is the cold rolling deformation rate of the pass, K is the wall reduction of the pass, D1 and S1 are the outer diameter and the wall thickness of the cold-rolled tube blank before the cold rolling of the pass, D2 and S2 are the outer diameter and the wall thickness of the titanium alloy tube after the cold rolling of the pass, and the units of D1, S1, D2 and S2 are all mm;
6. cold rolling a phi 33 multiplied by 3.8 titanium alloy pipe into a phi 21 multiplied by 1.7 (with an outer diameter of 21mm and a wall thickness of 1.7 mm) titanium alloy pipe on a two-roll cold pilger mill LG30, and then performing vacuum annealing, wherein the cold rolling deformation rate of the pass is 70.4% according to a calculation formula (1) in the process 3, the wall reduction of the pass is 1.52 according to a calculation formula (2) in the process 4, the vacuum annealing temperature of the titanium alloy pipe obtained by cold rolling of the pass is 686 ℃ (the calculation formula is (922/2+320 multiplied by 0.704)) DEG C, and the annealing heat preservation time is 68 minutes (the calculation formula is (40 multiplied by 1.7)) minutes;
in equations (1) and (2) of this flow: epsilon is the cold rolling deformation rate of the pass, K is the wall reduction of the pass, D1 and S1 are the outer diameter and the wall thickness of the titanium alloy tube before the cold rolling of the pass, D2 and S2 are the outer diameter and the wall thickness of the titanium alloy tube after the cold rolling of the pass, and the units of D1, S1, D2 and S2 are all mm;
7. Drawing a phi 21 multiplied by 1.7 titanium alloy pipe on a precise hydraulic drawing machine to form a phi 19 multiplied by 1.4 (the outer diameter is 19mm, the wall thickness is 1.4 mm) titanium alloy pipe, lubricating the inner surface and the outer surface of the titanium alloy pipe by adopting MoS2 aqua before drawing, and carrying out vacuum annealing after drawing; wherein, the drawing deformation rate is 24.9% according to the calculation formula (1) in the procedure 3, the vacuum annealing temperature of the titanium alloy tube obtained by the cold rolling in the pass is 541 ℃ (the calculation formula is (922/2+320 multiplied by 0.249)), and the annealing heat preservation time is 56 minutes (the calculation formula is (40 multiplied by 1.4)) minutes;
In the formula (1) of the flow, epsilon is the drawing deformation rate, D1 and S1 are the outer diameter and the wall thickness of the titanium alloy tube before drawing, D2 and S2 are the outer diameter and the wall thickness of the titanium alloy tube after drawing, and the units of D1, S1, D2 and S2 are all mm;
8. cold rolling a phi 19 multiplied by 1.4 titanium alloy tube into a phi 12 multiplied by 0.6 (with an outer diameter of 12mm and a wall thickness of 0.6 mm) titanium alloy tube on a two-roll cold-rolling tube mill LG15, and then performing vacuum annealing, wherein the cold-rolling deformation rate of the pass is 72.2% according to a calculation formula (1) in the above procedure 3, the wall reduction of the pass is 1.55 according to a calculation formula (2) in the above procedure 4, the vacuum annealing temperature of the titanium alloy tube obtained by the cold-rolling of the pass is 692 ℃ (a calculation formula is (922/2+320 multiplied by 0.722) DEG C, and the annealing heat-preserving time is 26 minutes (a calculation formula is (40 multiplied by 0.6)) min);
In equations (1) and (2) of this flow: epsilon is the cold rolling deformation rate of the pass, K is the wall reduction of the pass, D1 and S1 are the outer diameter and the wall thickness of the titanium alloy tube before the cold rolling of the pass (namely the outer diameter and the wall thickness of the titanium alloy tube after the drawing in the process 7), D2 and S2 are the outer diameter and the wall thickness of the titanium alloy tube after the cold rolling of the pass, and the units of D1, S1, D2 and S2 are all mm;
9. straightening and pickling a phi 12 multiplied by 0.6 titanium alloy tube to obtain a TA18 thin-wall titanium alloy seamless tube, and sampling and detecting the yield strength, the tensile strength and the elongation of the titanium alloy seamless tube.
The TA18 titanium alloy seamless tube with the specification of phi 12 multiplied by 0.6mm prepared in the embodiment has the yield strength of 565MPa, the tensile strength of 695MPa and the elongation of 26%.
Example 2
This example produced TA18 thin-walled titanium alloy seamless tubes of gauge Φ14X0.7 mm (i.e., 14mm outside diameter, 0.7mm wall thickness).
The preparation process adopted in this example is as follows:
1. Adopting sponge titanium with Brinell hardness HB of 84 and aluminum vanadium intermediate alloy, smelting by a vacuum consumable arc furnace for two times to obtain a round TA18 titanium alloy cast ingot with phi 230 (diameter of 230 mm), wherein the content of N (mass fraction) of the titanium alloy cast ingot is 0.001%, and determining the phase transition point temperature T of the titanium alloy cast ingot to be 922 ℃;
2. Heating a phi 230 round TA18 titanium alloy cast ingot to 1002 ℃ (the calculation formula is (922+80) DEG C) in a resistance furnace, preserving heat for 1 hour, discharging, and perforating on a two-roll oblique rolling perforating machine to obtain a phi 220 multiplied by 50 (the outer diameter is 220mm, and the wall thickness is 50 mm) capillary;
3. Heating a phi 220 multiplied by 50 hollow billet to 862 ℃ (the calculation formula is (922-60) DEG C, extruding the hollow billet into a phi 62 multiplied by 11 hollow billet (the outer diameter is 62mm, the wall thickness is 11 mm) on a horizontal extruder, preheating the extrusion die to 400 ℃, controlling the extrusion speed to be 60mm/s, calculating the length of the extruded hollow billet to be 15.15 times of the length of the hollow billet according to the calculation formula (1) in the embodiment 1 to obtain the extrusion deformation rate to be 93.4%, annealing the phi 62 multiplied by 11 hollow billet in a resistance furnace, annealing the hollow billet at 832 ℃ (the calculation formula is (922-90)) DEG C), cooling the hollow billet to 700 ℃ in the resistance furnace after the annealing heat preservation time is 100 minutes, discharging the hollow billet by using the waste heat, and controlling the recrystallized grain diameter of the annealed hollow billet to be less than or equal to 5 microns;
In equation (1) of this flow: epsilon is extrusion deformation rate, D1 and S1 are respectively the outer diameter and the wall thickness of a hollow billet, D2 and S2 are respectively the outer diameter and the wall thickness of a hollow billet, and the units of D1, S1, D2 and S2 are all mm;
4. Pickling a phi 62 multiplied by 11 hollow tube blank, then carrying out 1-pass cold rolling on a three-roller cold tube mill LD60 to obtain a phi 58 multiplied by 10 (with an outer diameter of 58mm and a wall thickness of 10 mm) titanium alloy tube intermediate blank, calculating according to a calculation formula (1) in the embodiment 1 to obtain a pass cold rolling deformation rate of 14.4%, and calculating according to a calculation formula (2) in the embodiment 1 to obtain a pass wall reduction of 1.41; sequentially carrying out internal boring, external grinding and external polishing on a phi 58 multiplied by 10 titanium alloy tube intermediate blank twice to obtain a phi 57 multiplied by 9 (the outer diameter is 57mm, the wall thickness is 9 mm) cold-rolled tube blank, and then carrying out vacuum annealing, wherein the two internal boring adopts YG8 hard alloy cutters, the speed of the vehicle is 20 m/min, the feeding amount of the first internal boring is 0.6mm, the feeding amount of the second internal boring is 0.1mm, the external grinding adopts a silicon carbide grinding wheel centerless grinding, and the external polishing adopts a green silicon carbide sand belt with granularity more than or equal to 400 meshes for polishing; the annealing temperature of the cold-rolled tube blank for vacuum annealing is 507 ℃ (the calculation formula is (922/2+320 multiplied by 0.144)) DEG C, and the annealing heat-preserving time is 360 minutes (the calculation formula is (40 multiplied by 9) minutes);
in equations (1) and (2) of this flow: epsilon is the cold rolling deformation rate of the primary cold rolling, K is the pass wall reduction, D1 and S1 are the outer diameter and the wall thickness of the hollow pipe blank respectively, D2 and S2 are the outer diameter and the wall thickness of a titanium alloy pipe intermediate blank obtained by the primary cold rolling respectively, and the units of D1, S1, D2 and S2 are all mm;
5. Cold rolling the phi 57 multiplied by 9 cold-rolled tube blank subjected to vacuum annealing into a phi 36 multiplied by 4 (with an outer diameter of 36mm and a wall thickness of 4 mm) titanium alloy tube on a two-roll cold-rolling tube mill LG40, and then performing vacuum annealing, wherein the cold-rolling deformation rate of the pass is 70.4% according to a calculation formula (1) in the embodiment 1, the wall reduction of the pass is 1.51 according to a calculation formula (2) in the embodiment 1, the vacuum annealing temperature of the titanium alloy tube obtained by cold-rolling of the pass is 686 ℃ (the calculation formula is (922/2+320 multiplied by 0.704)) DEG C, and the annealing heat-preserving time is 160 minutes (the calculation formula is (40 multiplied by 4)) minutes;
in equations (1) and (2) of this flow: epsilon is the cold rolling deformation rate of the pass, K is the wall reduction of the pass, D1 and S1 are the outer diameter and the wall thickness of the cold-rolled tube blank before the cold rolling of the pass, D2 and S2 are the outer diameter and the wall thickness of the titanium alloy tube after the cold rolling of the pass, and the units of D1, S1, D2 and S2 are all mm;
6. Cold rolling a phi 36 multiplied by 4 titanium alloy tube into a phi 23 multiplied by 1.8 (with an outer diameter of 23mm and a wall thickness of 1.8 mm) titanium alloy tube on a two-roll cold-rolling mill LG30, and then carrying out vacuum annealing, wherein the cold-rolling deformation rate of the pass is 70.2% according to a calculation formula (1) in example 1, the wall reduction of the pass is 1.52 according to a calculation formula (2) in example 1, the vacuum annealing temperature of the titanium alloy tube obtained by the cold-rolling of the pass is 686 ℃ (a calculation formula is (922/2+320 multiplied by 0.704)) DEG C, and the annealing heat-preserving time is 72 minutes (a calculation formula is (40 multiplied by 1.8)) min;
in equations (1) and (2) of this flow: epsilon is the cold rolling deformation rate of the pass, K is the wall reduction of the pass, D1 and S1 are the outer diameter and the wall thickness of the titanium alloy tube before the cold rolling of the pass, D2 and S2 are the outer diameter and the wall thickness of the titanium alloy tube after the cold rolling of the pass, and the units of D1, S1, D2 and S2 are all mm;
7. Drawing a phi 23 multiplied by 1.8 titanium alloy pipe on a precise hydraulic drawing machine to form a phi 22 multiplied by 1.6 (the outer diameter is 22mm, the wall thickness is 1.6 mm) titanium alloy pipe, lubricating the inner surface and the outer surface of the titanium alloy pipe by adopting MoS2 aqua before drawing, and carrying out vacuum annealing after drawing; wherein, the drawing deformation rate is 14.5% according to the calculation formula (1) in the embodiment 1, the vacuum annealing temperature of the titanium alloy tube obtained by the cold rolling in the pass is 507 ℃ (the calculation formula is (922/2+320 multiplied by 0.145)) DEG C, and the annealing heat preservation time is 64 minutes (the calculation formula is (40 multiplied by 1.6)) min;
In the formula (1) of the flow, epsilon is the drawing deformation rate, D1 and S1 are the outer diameter and the wall thickness of the titanium alloy tube before drawing, D2 and S2 are the outer diameter and the wall thickness of the titanium alloy tube after drawing, and the units of D1, S1, D2 and S2 are all mm;
8. Cold rolling a phi 22 multiplied by 1.6 titanium alloy tube into a phi 14 multiplied by 0.7 (with an outer diameter of 14mm and a wall thickness of 0.7 mm) titanium alloy tube on a two-roll cold-rolling tube mill LG15, and then carrying out vacuum annealing, wherein the cold-rolling deformation rate of the pass is 71.5% according to a calculation formula (1) in the embodiment 1, the wall reduction of the pass is 1.55 according to a calculation formula (2) in the embodiment 1, the vacuum annealing temperature of the titanium alloy tube obtained by the cold-rolling of the pass is 690 ℃ (a calculation formula is (922/2+320 multiplied by 0.715)) DEG C, and the annealing heat-preservation time is 28 minutes (a calculation formula is (40 multiplied by 0.7)) min;
In equations (1) and (2) of this flow: epsilon is the cold rolling deformation rate of the pass, K is the wall reduction of the pass, D1 and S1 are the outer diameter and the wall thickness of the titanium alloy tube before the cold rolling of the pass (namely the outer diameter and the wall thickness of the titanium alloy tube after the drawing in the process 7), D2 and S2 are the outer diameter and the wall thickness of the titanium alloy tube after the cold rolling of the pass, and the units of D1, S1, D2 and S2 are all mm;
9. Straightening and pickling a phi 14 multiplied by 0.7 titanium alloy tube to obtain a TA18 thin-wall titanium alloy seamless tube, and sampling and detecting the yield strength, the tensile strength and the elongation of the titanium alloy seamless tube.
The TA18 titanium alloy seamless tube with the specification of phi 14 multiplied by 0.7mm prepared in the embodiment has the yield strength of 560MPa, the tensile strength of 690MPa and the elongation of 28%.
The plasticity of the thin-wall titanium alloy seamless tube prepared in the embodiment 1 and the embodiment 2 is improved by selecting low-hardness sponge titanium, preparing a tube blank by combining a diagonal rolling perforation extrusion process, treating the inner surface and the outer surface of the tube blank by adopting an inner boring process, an outer grinding process and an outer polishing process, optimizing a titanium alloy tube cold rolling process, optimizing a titanium alloy tube annealing process and combining a two-roller cold rolling process and a drawing cold deformation process to regulate and control the comprehensive action of grain orientation of the titanium alloy tube, and the plasticity of the thin-wall titanium alloy tube finished product is greatly improved. In general, the elongation of the TA18 thin-wall titanium alloy seamless tube is below 20%, while the elongation of the TA18 thin-wall titanium alloy seamless tube prepared in the above embodiments 1 and 2 is above 26%, so that it can be obtained that the method for improving the plasticity of the titanium alloy seamless tube disclosed in the embodiments of the present invention is beneficial to improving the plasticity of the thin-wall titanium alloy seamless tube.
In summary, in the embodiment of the invention, the titanium sponge with the Brinell hardness HB less than or equal to 85 is selected, and contains less impurity elements, so that the plasticity of the titanium alloy finished product tube is ensured from the raw material; the oxygen and nitrogen content in the titanium alloy cast ingot is reduced by twice vacuum consumable arc furnace smelting, and the uniformity of the components of the titanium alloy tube is ensured, so that the plasticity of the titanium alloy finished tube is ensured; the method provided by the invention does not adopt the conventional process of forging the cast ingot into a round rod through multiple fires, drilling, internally boring and externally turning the round rod into a hollow rod, and extruding the hollow rod into a tube blank, but directly extruding the cast ingot into a hollow tube blank through two-roller oblique rolling perforation without forging, thereby greatly reducing the working procedures, improving the yield, superposing the large deformation rate of the oblique rolling perforation and extrusion, being beneficial to refining tube blank grains, optimizing the texture orientation of the tube blank, improving the plasticity of a titanium alloy tube finished product, controlling the diameter of the recrystallized grains of the hollow tube blank after annealing to be less than or equal to 5 microns, and being capable of preparing tissues for the subsequent cold rolling working procedure, thereby being beneficial to further improving the plasticity of the titanium alloy finished product tube;
according to the embodiment of the invention, the hollow tube blank is rolled on the three-roller cold pilger mill with small deformation of 1 pass, so that the inner diameter of the Yu Gui round tube blank is facilitated, the wall thickness deviation is reduced, the yield of an inner boring process is improved, the oxide layer and the gas permeation layer on the inner surface of the intermediate blank of the titanium alloy tube can be completely removed through twice inner boring, the oxide layer and the gas permeation layer on the outer surface of the intermediate blank of the titanium alloy tube can be completely removed through outer grinding and outer polishing processing, and the defects such as cracks and the like on the inner surface and the outer surface of the titanium alloy tube in the subsequent cold rolling process are prevented, so that the plasticity of a titanium alloy finished tube is facilitated to be improved;
The embodiment of the invention carries out cold rolling on the cold-rolled tube blank on a two-roller cold-rolling mill, adopts large cold-rolling deformation rate, large wall reduction and high rolling speed for each cold rolling pass, and is beneficial to greatly reducing cold-rolling defects so as to ensure that the plasticity of the finished titanium alloy tube product is improved; the titanium alloy tube can be guaranteed to be fully recovered and recrystallized by controlling reasonable annealing process parameters, the plasticity is improved, and the cracking defect of the titanium alloy tube in the subsequent cold rolling deformation process is reduced; the grain orientation of the titanium alloy tube can be flexibly adjusted by adopting a mode of combining the two-roller cold rolling and the drawing deformation process, thereby being beneficial to improving the plasticity of the titanium alloy finished tube.
It should be noted that, each component or step in each embodiment may be intersected, replaced, added, and deleted, and therefore, the combination formed by these reasonable permutation and combination transformations shall also belong to the protection scope of the present invention, and shall not limit the protection scope of the present invention to the embodiments.
The foregoing is an exemplary embodiment of the present disclosure, and the order in which the embodiments of the present disclosure are disclosed is merely for the purpose of description and does not represent the advantages or disadvantages of the embodiments. It should be noted that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest that the scope of the disclosure of embodiments of the invention (including the claims) is limited to these examples and that various changes and modifications may be made without departing from the scope of the invention as defined in the claims. The functions, steps and/or actions of the method claims in accordance with the disclosed embodiments described herein need not be performed in any particular order. Furthermore, although elements of the disclosed embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.
Those of ordinary skill in the art will appreciate that: the above discussion of any embodiment is merely exemplary and is not intended to imply that the scope of the disclosure of embodiments of the invention, including the claims, is limited to such examples; combinations of features of the above embodiments or in different embodiments are also possible within the idea of an embodiment of the invention, and there are many other variations of the different aspects of the embodiments of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, and the like, which are made within the spirit and principles of the embodiments of the invention, are included within the scope of the embodiments of the invention.
Claims (7)
1. A method for improving plasticity of a thin-wall titanium alloy seamless pipe, which is characterized by comprising the following steps:
s10, smelting raw materials to obtain a titanium alloy ingot, and measuring the phase transition point temperature of the titanium alloy ingot;
S20, heating and preserving heat of the titanium alloy cast ingot which is not forged, and then performing oblique rolling perforation to form a blank pipe;
S30, heating the hollow billet and extruding the heated hollow billet into a hollow billet, controlling the extrusion deformation rate to be more than or equal to 85%, controlling the length of the extruded hollow billet to be more than or equal to 15 times of the length of the hollow billet, annealing the hollow billet, controlling the recrystallized grain diameter of the hollow billet to be less than or equal to 5 microns after annealing, heating the hollow billet to 60 ℃ below the phase change point temperature, controlling the preheating temperature of an extrusion die to be 390-410 ℃, controlling the extrusion speed to be 55-65 mm/S, and controlling the annealing temperature of the hollow billet to be 90 ℃ below the phase change point temperature and the annealing heat preservation time to be 90-110 minutes;
S40, performing surface treatment on the annealed hollow tube blank after the primary cold rolling to obtain a cold-rolled tube blank, wherein the performing the primary cold rolling comprises: performing 1-pass cold rolling on the hollow tube blank on a three-roller cold pilger mill to prepare a titanium alloy tube intermediate blank, and controlling the cold rolling deformation rate to be less than or equal to 20%; the surface treatment includes: performing internal boring, external grinding and external polishing on the intermediate billet of the titanium alloy pipe twice to prepare a cold-rolled pipe billet; and carrying out vacuum annealing on the cold-rolled tube blank subjected to surface treatment, wherein YG8 hard alloy cutters are adopted for two times of internal boring, the speed of the vehicle is controlled to be 18-21 m/min, and the feeding amount of the second internal boring is controlled to be 1/6 of the feeding amount of the first internal boring; the external grinding adopts a silicon carbide grinding wheel centerless grinding, and the external polishing adopts a green silicon carbide grinding belt with granularity more than or equal to 400 meshes for polishing; the annealing temperature of the cold-rolled tube blank for vacuum annealing is (T/2+320×ε) DEG C, the annealing heat-preserving time is (40×S) minutes, wherein T is the transformation point temperature, ε is the cold-rolling deformation rate of 1-pass cold rolling, S is the wall thickness of the cold-rolled tube blank, and the unit is mm;
S50, performing multi-pass cold rolling on the cold-rolled tube blank to obtain a titanium alloy tube, and performing vacuum annealing on the titanium alloy tube subjected to each pass of cold rolling, wherein the deformation rate of each pass of cold rolling is controlled to be more than or equal to 70%, the wall reduction of each pass of cold-rolled tube blank is controlled to be more than or equal to 1.50, the rolling speed of each pass of cold-rolled tube blank is controlled to be more than or equal to 120 times/min, the vacuum annealing temperature of the titanium alloy tube obtained by each pass of cold rolling is determined according to the phase transition point temperature and the deformation rate of each pass of cold rolling, and the annealing heat preservation time is determined according to the wall thickness of the titanium alloy tube obtained by each pass of cold rolling.
2. The method for improving the plasticity of the thin-wall titanium alloy seamless pipe according to claim 1, wherein in the step S10, titanium sponge and intermediate alloy with Brinell hardness HB less than or equal to 85 are adopted, and the titanium alloy cast ingot is obtained through smelting in a twice vacuum consumable arc furnace.
3. The method for improving the plasticity of a thin-walled titanium alloy seamless tube according to claim 1, wherein in the step S20, the titanium alloy ingot is heated to 80 ℃ above the transformation point temperature and is kept for 1-2 hours.
4. The method according to claim 1, wherein in the step S50, the vacuum annealing temperature of the titanium alloy tube obtained by each cold rolling pass is (T/2+320×ε) DEG C, the annealing holding time is (40×s) minutes, wherein T is the transformation point temperature, ε is the cold rolling deformation rate per cold rolling pass, and S is the wall thickness of the titanium alloy tube after each cold rolling pass in mm.
5. The method for improving the plasticity of a thin-wall titanium alloy seamless pipe according to claim 1, wherein in the step S50, the titanium alloy pipe is drawn on a drawing machine before the last 1-pass cold rolling, the inner and outer surfaces of the titanium alloy pipe are lubricated by using a MoS2 water agent before the drawing, and vacuum annealing is performed after the drawing, wherein the vacuum annealing temperature is (T/2+320×epsilon) DEG C, and the annealing heat-preserving time is (40×s) minutes, wherein T is the transformation point temperature, and epsilon is the drawing deformation rate.
6. The method of improving the plasticity of a thin-walled titanium alloy seamless tube according to claim 5, wherein the extrusion deformation rate, the cold rolling deformation rate per pass, the drawing deformation rate and the wall reduction per pass are calculated according to the following formulas:
ε=（（D1-S1）*S1-（D2-S2）*S2）/（（D1-S1）*S1）
K=（S1-S2）*D1/（D1-D2）*S1
Wherein epsilon is extrusion deformation rate, cold rolling deformation rate or drawing deformation rate of each pass; k is the wall reduction amount of each pass; d1 and S1 are respectively the outer diameter and the wall thickness of the extruded, cold-rolled or drawn front pipe in each pass; d2 and S2 are the outer diameter and wall thickness of the tube after extrusion, cold rolling or drawing each pass, respectively.
7. A titanium alloy seamless tube obtained by the method according to any one of claims 1 to 6, wherein the titanium alloy seamless tube is a TA18 titanium alloy seamless tube, the wall thickness of the titanium alloy seamless tube is less than or equal to 1mm, and the elongation of the titanium alloy seamless tube is more than or equal to 26%.
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