CN114182186A - Method for improving structure uniformity of near-beta titanium alloy fastener bar blank - Google Patents
Method for improving structure uniformity of near-beta titanium alloy fastener bar blank Download PDFInfo
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- CN114182186A CN114182186A CN202111331745.2A CN202111331745A CN114182186A CN 114182186 A CN114182186 A CN 114182186A CN 202111331745 A CN202111331745 A CN 202111331745A CN 114182186 A CN114182186 A CN 114182186A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
- C22F1/18—High-melting or refractory metals or alloys based thereon
- C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C14/00—Alloys based on titanium
Abstract
The invention relates to a method for improving the texture uniformity of a near-titanium alloy fastener bar blank, which comprises the steps of heating a titanium alloy ingot to the temperature of T1, preserving heat for T1 time, carrying out A extrusion forming treatment, and cooling the titanium alloy bar blank to the room temperature after the A extrusion forming treatment; cutting the long bar material into short forged bars by linear cutting, heating the titanium alloy bar material to T2 temperature, keeping the temperature for T2 time, carrying out B extrusion molding treatment, and air cooling the titanium alloy bar material to room temperature after B extrusion molding; and cutting the long bar stock into short bar stocks by adopting linear cutting, and then sequentially carrying out solid solution and aging strengthening treatment. The process is suitable for preparing a near-type titanium alloy bar blank with the ingot casting diameter less than or equal to 200 mm, the cast structure can be fully crushed by two times of extrusion processes, the stress is eliminated by combining the solid solution and aging heat treatment processes, the structure is uniform, and the mechanical property of the material is further improved so as to meet the requirements of the bar blank of the aerospace fastener.
Description
Technical Field
The invention relates to the field of preparation of near-beta titanium alloy bars, in particular to a method for improving the uniformity of a near-beta titanium alloy fastener bar blank structure.
Background
The near-beta titanium alloy bar material is used as an important material for manufacturing fasteners such as aerospace bolts and the like, and has an irreplaceable status in the field of aerospace industry. At present, the domestic near-beta titanium alloy bar is difficult to meet the high-performance requirements of aerospace, and the main reason is that the titanium alloy bar prepared by domestic traditional processing methods such as forging and rolling has poor microscopic uniformity and greatly reduced mechanical properties. And the near-beta titanium alloy bar is prepared by extrusion, and the cast structure can be fully crushed due to the compressive stress from three directions, so that the crystal grains are refined to a great extent, and the uniformity of the size and the shape distribution of the crystal grains is improved. Meanwhile, the reasonable solid solution and aging process is matched after extrusion, so that the residual stress after extrusion can be eliminated, the dissolution of the residual alpha phase is promoted, and the microstructure uniformity and the mechanical property of the bar are further improved.
Disclosure of Invention
Aiming at the defects of the conventional preparation technology of the near-beta titanium alloy bar, the invention provides a method for combining an extrusion process and a heat treatment process so as to improve the microstructure uniformity and the mechanical property of a bar blank.
The technical scheme adopted by the invention is as follows.
A method for improving the structure uniformity of a near-beta titanium alloy fastener bar blank. It is characterized in that.
And removing the riser end and the ingot bottom of the titanium alloy ingot in advance, and removing surface defects.
Heating the titanium alloy ingot to T degree1Temperature t1And performing A extrusion forming treatment on a 2500-4000 ton extruder, cooling the extruded product to room temperature in air, and cutting the product into short bars by linear cutting.
Heating the short titanium alloy bar to T degree2Temperature and heat preservation t2And time, carrying out B extrusion forming treatment on a 1000-2000-ton extruder, cooling the extruded material to room temperature in air, and cutting the obtained bar stock into short bar stock by adopting linear cutting.
The diameter specification of an ingot used for extrusion forming is less than or equal to 200 mm; the diameter specification of a bar used for B extrusion forming is less than or equal to 100 mm.
Carrying out solution treatment on the short titanium alloy bar stock, and heating the titanium alloy bar stock to T3Temperature and heat preservation t3And (5) cooling to room temperature after the time is over.
Carrying out aging treatment after the solution treatment is finished, and heating the titanium alloy bar stock to T4Temperature and heat preservation t4And after the time is over, air cooling to room temperature.
Wherein: t is1=∈[Tβ+20℃，Tβ+100℃]，T2=∈[Tβ+20℃，Tβ+100℃]，T3=∈[Tβ-150℃，Tβ-100℃]，T4=∈[Tβ-310℃，Tβ-260℃]，Tββ phase and α → β phase transition temperature.
The specific scheme is as follows.
A extrusion molding treatment stage, coating glass lubricant on the surface layer of the cast ingot copper steel film to reduce friction, and performing extrusion molding on the cast ingot copper steel film at T1Temperature t1And (3) forward extrusion is adopted on a 2500-4000 ton extruder, the extrusion speed is controlled to be 40-45 mm/s, and the extrusion ratio is controlled to be 4-9.
The extrusion forming treatment stage is as follows: and coating a glass lubricant on the surface layer of the bar copper steel film to reduce friction, and extruding the bar copper steel film on a 1000-2000 ton extruder in a forward direction at an extrusion speed of 45-50 mm/s and an extrusion ratio of 8.7-13.
When solid solution and aging strengthening treatment are carried out, titanium alloy bars are all put into the furnace after being heated.
Step c, solution treatment heat preservation time: (D)2/2 + 0~30） min。
D, preserving heat for the time from the aging treatment to the time after the furnace is heated: 480-600 min.
The invention has the beneficial effects.
The invention aims at the near-beta titanium alloy ingot (the diameter is less than or equal to 200 mm), adopts the forward hot extrusion molding, the solid solution treatment and the aging treatment, and compared with the traditional forging and rolling, the ingot is subjected to a stronger three-dimensional compressive stress state through a round through hole hot extrusion die, and the metal can exert the maximum plasticity, which is particularly important for the titanium alloy with poor plastic deformation capability. The hot extrusion molding process can fully crush large grains of the bar, and the size and the shape distribution of the grains are more uniform, so that the strength and the plasticity of the titanium alloy are improved.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Fig. 2 is a metallographic structure diagram (b) and a metallographic sampling position diagram (a) at the end of the second pass of extrusion in example 1.
Fig. 3 is a metallographic structure diagram (b) and a metallographic sampling position diagram (a) at the end of the second pass of extrusion in example 2.
Detailed Description
The following will clearly and completely describe the technical scheme in the embodiment of the invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
When the near-b titanium alloy cast ingot is extruded for the first time, the periphery of the near-b titanium alloy cast ingot is wrapped by a copper steel film and coated with a glass lubricant to reduce friction, and the near-b titanium alloy cast ingot is heated by a heating furnace at T1Thermal insulation t1And (3) forward hot extrusion is carried out on a 2500-4000 ton horizontal extruder, the extrusion ratio is 4-9, the preheating temperature of an extrusion die is 300 ℃, and the extrusion speed is controlled at 40-45 mm/s. Cutting the bar material obtained by the first extrusion into short bar material by adopting a line, then carrying out the second extrusion, and carrying out T2Thermal insulation t2After the time, forward hot extrusion is adopted in a 1000-2000-ton horizontal extruder, the extrusion ratio is 8.7-13, the extrusion speed is controlled at 45-50 mm/s, and the friction condition and the die temperature are the same as those of the first-time extrusion.
After extrusion, carrying out solution treatment on the bar stock at T3Temperature and heat preservation t3Air cooling to room temperature; followed by aging treatment at T4Temperature and heat preservation t4And (5) cooling the mixture to room temperature in air.
The invention carries out two times of positive hot extrusion on the near-b titanium alloy material to break the as-cast structure, refine the crystal grains and homogenize the structure, and simultaneously adopts the solid solution and aging treatment process to improve the strength and toughness of the material so as to meet the performance requirements of the rod blank of the aerospace fastener.
The invention is further illustrated by the following examples.
Example one: a method for improving the homogeneity of the structure of a near-b titanium alloy fastener bar blank.
The chemical composition of the Ti6554 titanium alloy is as follows (percent by mass): 5.7 parts of chromium, 4.7 parts of molybdenum, 4.8 parts of vanadium, 3.9 parts of aluminum, 0.08 part of iron, 0.028 part of silicon, 0.025 part of carbon and the balance of titanium. Ti6554 phase transition temperature Tβ=820 ℃, belonging to a novel near-beta titanium alloy.
The molding process includes the following steps.
(1) The diameter of a Ti6554 cast ingot is phi 200 multiplied by 240 mm during the first extrusion, the temperature is kept for 160 min at 980 ℃, forward hot extrusion is adopted in a 4000-ton horizontal extruder, the extrusion speed is 40mm/s, the extrusion ratio is 6.05, the preheating temperature of an extrusion die is 300 ℃, the inner diameter of the die is phi 85, and the Ti6554 cast ingot is longitudinally cut into phi 85 multiplied by 140 mm bars after the extrusion is finished.
(2) Preserving heat for 50 min at 940 ℃ by a heating furnace, adopting forward hot extrusion in a 2000-ton horizontal extruder, wherein the extrusion ratio is 10.56, the extrusion speed is 45mm/s, the preheating temperature of an extrusion die is 300 ℃, the inner diameter of the die is phi 25, and the warp is cut into phi 25 multiplied by 110 bars after the second-pass extrusion is finished.
(3) And (4) carrying out solution treatment, after the temperature of the heating furnace reaches 720 ℃, putting the bar stock into the heating furnace, keeping the temperature for 45 min, and cooling the bar stock to room temperature after the heat preservation time is ensured.
(4) And then, carrying out aging treatment, and after the temperature of the heating furnace reaches 550 ℃, putting the bar stock into the heating furnace for heat preservation for 600 min, and carrying out air cooling to room temperature after the heat preservation time is ensured to reach.
After the aging treatment is finished, the mechanical property of the bar stock is detected: the tensile strength is 1380MPa, the plastic elongation strength Rp0.2 is 1257MPa, and the elongation is 7.5 percent; compared with the properties of the bar material which adopts the traditional rolling, solid solution and aging treatment: the tensile strength is 1290MPa, the specified plastic elongation strength Rp0.2 is 1180MPa, the elongation is 6.0 percent, and the strength and the plasticity are both obviously improved.
Example two: a method for improving the homogeneity of the structure of a bar billet of an aviation titanium alloy fastener.
The chemical composition of the Ti55531 titanium alloy is as follows (mass fraction): 5.3 parts of aluminum, 5.2 parts of molybdenum, 5.2 parts of vanadium, 2.65 parts of chromium, 1.02 parts of zirconium and the balance of titanium. Ti55531 phase transition temperature Tβ=850 ℃, belonging to a novel near-beta titanium alloy.
The molding process includes the following steps.
(1) In the first extrusion, the forged rod with phi 160X 220 mm is heated in a heating furnace at 1010 ℃ for 128 min, and is subjected to forward hot extrusion in a 4000T horizontal extruder at the extrusion speed of 40mm/s and the extrusion ratio of 6.05, the preheating temperature of an extrusion die is 300 ℃, the inner diameter of the die is phi 65, and the forged rod is cut into phi 65X 140 bar stocks through warp cutting after the extrusion is finished.
(2) Preserving heat for 40 min at 970 ℃ by a heating furnace, adopting forward hot extrusion in a 2000T horizontal extruder, wherein the extrusion ratio is 10.56, the extrusion speed is 45mm/s, the preheating temperature of an extrusion die is 300 ℃, the inner diameter of the die is phi 20, and after the second-pass extrusion is finished, the warp is cut into phi 20 multiplied by 110 bars.
(3) And (3) carrying out solution treatment until the temperature of the heating furnace reaches 750 ℃, then placing the bar stock into the heating furnace for heat preservation for 40 min, and air-cooling to room temperature after the heat preservation time is ensured.
(4) And then, performing aging treatment until the temperature of the heating furnace reaches 600 ℃, putting the bar stock into the heating furnace, and keeping the temperature for 600 min, so as to ensure that the bar stock is cooled to room temperature after the heat preservation time reaches.
Detecting the mechanical property of the bar material which adopts the extrusion process and the solid solution aging treatment process: tensile strength is 1413MPa, plastic elongation strength Rp0.2 is 1298MPa, and elongation is 7.5%; compared with the properties of the bar material adopting the traditional rolling and heat treatment process, the tensile strength is 1250MPa, the specified plastic elongation strength Rp0.2 is 1100MPa, the elongation is 5.5 percent, and the strength and the plasticity are obviously improved.
The microstructure of the titanium alloy rods prepared in examples 1 and 2 was examined. Wherein, the microstructure detection adopts the conventional metallographic preparation and corrosion technology, and the Ti6554 corrosive liquid adopts: mixed liquid of hydrofluoric acid, nitric acid and water, the volume ratio is 1: 2: 5; the Ti55531 corrosive liquid adopts: mixed electrophoresis of hydrochloric acid, nitric acid and water, wherein the volume ratio is 1: 1: 16; the microstructure was observed under an optical microscope and the grain size and phase volume fraction were analyzed using Image-pro software. As shown in fig. 2 and 3, it can be observed that the microstructure uniformity of the bar is high, and the grains are sufficiently refined after extrusion.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention. Structures, devices, and methods of operation not specifically described or illustrated herein are generally practiced in the art without specific recitation or limitation.
Claims (7)
1. A method for improving the homogeneity of a near-titanium alloy fastener bar blank structure is characterized by comprising the following steps:
a. heating a copper steel film wrapped by a near-titanium alloy ingot (the diameter is less than or equal to 200 mm) to T1 temperature, preserving heat for T1 time, carrying out A extrusion forming treatment, cooling the extruded product in air to room temperature, and cutting the product into short bars by adopting linear cutting;
b. heating a short titanium alloy bar wrapped with a copper steel film to T2 temperature, keeping the temperature for T2 time, then carrying out B extrusion forming treatment, cooling the extruded bar in air to room temperature, and cutting the obtained bar into short bars by adopting linear cutting;
c. carrying out solution treatment on the short titanium alloy bar stock, heating the titanium alloy bar stock to the temperature of T3, keeping the temperature for T3 time, and then air-cooling to room temperature;
d. carrying out aging treatment after the solution treatment is finished, heating the titanium alloy bar stock to the temperature of T4, keeping the temperature for T4 time, and then air-cooling to room temperature
Wherein: t1= epsilon [ T beta +20 ℃, T beta +100 ℃ C ], T2= epsilon [ T beta +20 ℃, T beta +100 ℃ C ], T3= epsilon [ T beta-150 ℃, T beta-100 ℃ C ], T4= epsilon [ T beta-310 ℃, T beta-260 ℃ C ], and T beta is the transformation temperature of beta phase and alpha beta phase.
2. The method for improving the homogeneity of the structure of a near-titanium alloy fastener bar blank according to claim 1, characterized in that:
step a, in the extrusion molding treatment stage A, coating a glass lubricant on the surface layer of the cast ingot copper steel film to reduce friction, and extruding the cast ingot on a 2500-4000 ton extruder in a forward direction, wherein the extrusion speed is controlled to be 40-45 mm/s, and the extrusion ratio is controlled to be 4-9.
3. The method for improving the homogeneity of the structure of a near-titanium alloy fastener bar blank according to claim 1, characterized in that: and step B, the extrusion forming treatment stage of B is as follows: glass lubricant is coated on the surface layer of the bar copper steel film to reduce friction, the bar copper steel film is extruded in a forward direction on a 1000-2000 ton extruder, the extrusion speed is controlled to be 45-50 mm/s, and the extrusion ratio is controlled to be 8.7-13.
4. The method for improving the homogeneity of the structure of a near-titanium alloy fastener bar blank according to claim 1, characterized in that: when the extrusion forming A and B are processed, the extrusion cylinder and the extrusion die need to be preheated to 300 ℃.
5. The method for improving the homogeneity of the structure of the aviation titanium alloy fastener bar blank according to claim 1, characterized in that: the extrusion A needs to be carried out in a heating furnace for the heat preservation time t1= 0.8 XD, and D is the diameter of the cast ingot; and B, keeping the temperature of the extruded ingot in a heating furnace for t2=0.6 XD 1, wherein D1 is the diameter of the ingot after the first extrusion.
6. The method for improving the homogeneity of the structure of the aviation titanium alloy fastener bar blank according to claim 1, characterized in that: and c, keeping the temperature for the solution treatment in the step c for t3= (D2/2 + 0-30) min, wherein D2 is the diameter of the bar stock after the second extrusion is finished.
7. The method for improving the homogeneity of the structure of the aviation titanium alloy fastener bar blank according to claim 1, characterized in that: and d, preserving the heat for t4= 480-600 min during aging treatment in the step d.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61284560A (en) * | 1985-06-10 | 1986-12-15 | Sumitomo Metal Ind Ltd | Manufacture of alpha+beta titanium alloy |
| US20170306467A1 (en) * | 2016-04-22 | 2017-10-26 | Arconic Inc. | Methods for finishing extruded titanium products |
| CN108048678A (en) * | 2017-12-14 | 2018-05-18 | 西北有色金属研究院 | A kind of high-strength high-plastic high-precision beta-titanium alloy tubing preparation method |
| CN113416906A (en) * | 2021-05-24 | 2021-09-21 | 天津职业技术师范大学(中国职业培训指导教师进修中心) | Process for preparing titanium alloy bar blank by combining extrusion cogging and pulse current heat treatment |
| CN113493886A (en) * | 2021-06-11 | 2021-10-12 | 天津职业技术师范大学(中国职业培训指导教师进修中心) | Forming method for improving structure uniformity of titanium alloy bar by combining free forging and pulse current auxiliary extrusion |
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2021
- 2021-11-11 CN CN202111331745.2A patent/CN114182186A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61284560A (en) * | 1985-06-10 | 1986-12-15 | Sumitomo Metal Ind Ltd | Manufacture of alpha+beta titanium alloy |
| US20170306467A1 (en) * | 2016-04-22 | 2017-10-26 | Arconic Inc. | Methods for finishing extruded titanium products |
| CN108048678A (en) * | 2017-12-14 | 2018-05-18 | 西北有色金属研究院 | A kind of high-strength high-plastic high-precision beta-titanium alloy tubing preparation method |
| CN113416906A (en) * | 2021-05-24 | 2021-09-21 | 天津职业技术师范大学(中国职业培训指导教师进修中心) | Process for preparing titanium alloy bar blank by combining extrusion cogging and pulse current heat treatment |
| CN113493886A (en) * | 2021-06-11 | 2021-10-12 | 天津职业技术师范大学(中国职业培训指导教师进修中心) | Forming method for improving structure uniformity of titanium alloy bar by combining free forging and pulse current auxiliary extrusion |
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