阅读说明：本技术 一种薄壁高强度钛合金管材及其制备方法 (Thin-wall high-strength titanium alloy pipe and preparation method thereof ) 是由 张晖 袁利红 张旺峰 于 2020-04-10 设计创作，主要内容包括：本发明公开了一种薄壁高强度钛合金管材及其制备方法,通过在旋锻过程中主要调节壁厚变形量和减壁减径比Q值进行调控,细化晶粒,形成径向织构；然后再通过去应力退火去除冷变形后管材的残余应力。钛合金管材包括TA类；TB类和TC类钛合金,管材规格范围：外径25-6mm,壁厚2.5-0.6mm。与冷轧工艺相比,本发明钛合金管材的变形量可达50％,使管材有利的径向织构增强,获得了具有较高的塑性和强度及疲劳性能的高强度钛合金管材。本发明提出的方法可以更为有效地实现冷旋锻高强钛合金管织构和性能的精确控制,并且生产设备小巧,易操作实施,变形能量消耗少,具有广阔的应用前景。(The invention discloses a thin-wall high-strength titanium alloy pipe and a preparation method thereof, wherein the wall thickness deformation and the wall reduction ratio Q value are mainly adjusted and controlled in the rotary swaging process, crystal grains are refined, and a radial texture is formed; and then removing the residual stress of the pipe after cold deformation by stress annealing. The titanium alloy pipe comprises TA; TB and TC titanium alloys, and the specification range of the pipe is as follows: the outer diameter is 25-6mm, and the wall thickness is 2.5-0.6 mm. Compared with the cold rolling process, the deformation of the titanium alloy pipe can reach 50 percent, so that the favorable radial texture of the pipe is enhanced, and the high-strength titanium alloy pipe with higher plasticity, strength and fatigue performance is obtained. The method provided by the invention can more effectively realize the accurate control of the texture and the performance of the cold rotary swaging high-strength titanium alloy tube, and has the advantages of small production equipment, easy operation and implementation, less deformation energy consumption and wide application prospect.)

1. The preparation method of the thin-wall high-strength titanium alloy pipe is characterized by comprising the following steps of:

s1, selecting a hot-rolled bar drilled pipe blank as a rotary swaging pipe blank directly or obliquely rolling a perforated pipe blank, performing hot extrusion to form the rotary swaging pipe blank, performing cold rotary swaging deformation on the titanium alloy pipe by optimizing pass reduction amount in the rotary swaging process to obtain a radial texture, adjusting the overall deformation amount and deformation mode in the cold rotary swaging process to realize overall regulation and control on the pipe texture, representing the deformation amount of the pipe in the deformation process by using a wall thickness deformation amount, representing the deformation mode by using a wall-reducing and diameter-reducing ratio Q value, displaying the texture strength of the pipe after rotary swaging to be 3.25-5.59 in a polar diagram, and displaying the maximum strength value of an ODF (orientation distribution function) of the texture to be 6.68-10.17;

and S2, adjusting the temperature of the heat treatment after the rotary swaging to remove the residual stress, and obtaining the titanium alloy pipe.

2. The method according to claim 1, wherein step S1 is specifically:

s101, controlling the extrusion temperature to be 750-920 ℃, and performing hot extrusion to obtain a titanium alloy tube blank;

s102, chamfering the titanium alloy tube blank obtained in the step S101, setting the thickness deformation interval of the rotary swaging wall to be 20% -50% and the Q value interval to be 1-4, and processing the tube blank into titanium alloy tubes with various specifications and sizes according to different rotary swaging passes;

s103, controlling the annealing temperature to be 750-900 ℃, and carrying out intermediate annealing on the titanium alloy pipe subjected to the rotary swaging in the step S102;

and S104, controlling the deformation range of the wall thickness of the rotary swaging to be 20% -50% and the deformation Q value to be 1-4, carrying out rotary swaging on the titanium alloy pipe obtained in the step S103 again, and carrying out acid pickling to obtain the titanium alloy pipe.

3. The method of claim 2, wherein in step S102, the number of passes in the cold swaging process is 6-15.

4. The method according to claim 2, wherein in step S1, the swaging deformation range is 40% to 50%.

5. The method according to claim 1, wherein in step S2, the titanium alloy tube after swaging is subjected to vacuum stress relief annealing at 300-500 ℃ for 2-4 hours.

6. The method according to claim 5, wherein the vacuum destressing temperature of the swaged titanium alloy tube is 400 to 500 ℃.

7. The method according to claim 1, wherein in step S1, the polar diagram of the swaged titanium alloy tube shows a texture strength of 4.37-5.59 and an orientation distribution function ODF maximum strength value of 8.49-10.17.

8. A thin-walled high strength titanium alloy tube made according to the method of claim 1.

Technical Field

The invention belongs to the technical field of metal material processing, and particularly relates to a thin-wall high-strength titanium alloy pipe and a preparation method thereof.

Background

Titanium and titanium alloy have light in weight, specific strength is high, corrosion resistance is strong, advantages such as anti crack expansion, widely apply to trades such as aerospace, energy, ocean engineering. However, titanium alloy thin-walled tubes such as Ti-6Al-4V have large deformation resistance and poor room temperature plasticity, so that the thin-walled seamless tubes prepared by cold machining have certain difficulty and are difficult to manufacture.

At present, Ti-6Al-4V alloy pipes are mostly produced by hot extrusion or hot rolling. In addition, because the pipe wall of the hot extrusion or hot rolling pipe is thick and the pipe diameter is large, the hot extrusion or hot rolling pipe cannot be used in the fields of aerospace and the like at present. Because the deformation rate of the cold rolling processing mode is too low (only 10-15 percent), the requirements of structure control, production equipment limitation and cost saving can not be met. In this case, annealing treatment must be frequently performed during deformation. Otherwise, continued cold deformation will tend to initiate crack initiation and propagation, resulting in deformation failure. The plasticity of a metallic material depends not only on the material itself, but also on the stress state of the material. Swaging is considered a plastic strengthening process due to the three-way compressive stress. In addition to common plastic materials such as copper, aluminum, and steel, swaging is also used for processing materials that are difficult to deform. During the rotary swaging, the blank is under the action of three-way pressure stress under reasonable process conditions, the rotary swaging force changes periodically, and the external friction force is not large. Since the deformation of the metal material is relatively gentle, the swaging method is suitable for processing a material having low plasticity. The rotary swaging is an important metal plastic processing method and has the advantages of improving the surface precision, saving materials and reducing the cost.

Cold deformation is very important and necessary for the formation of texture and can improve the fatigue and tensile properties of the pipe. In the cold rolling process of high-strength titanium alloy pipes such as Ti-6Al-4V and the like, the density of the texture is increased along with the increase of the deformation rate. A larger amount of deformation may promote reorganization of the texture. The anisotropy of titanium is currently believed to be an advantage, referred to as texture strengthening. If the technological parameters can be controlled and optimized in the deformation process, the performance of the prepared tube is far better than that of the tube with randomly distributed crystals. Compared with the pipes with the tangential or randomly distributed crystals, the pipes with the radial texture have higher strength, better tensile property, better wall thickness reduction resistance and excellent fatigue resistance under biaxial stretching.

In the cold rotary swaging process, the high-strength titanium alloy tube often has large uneven deformation and generates residual stress. In general, residual stress has a significant effect on shape, fatigue strength, and stress corrosion resistance. Brittleness and residual stress caused by cold working should be eliminated by annealing, otherwise the subsequent working and service performance are adversely affected. High temperature annealing, while completely relieving residual stress from the pipe, can also destroy the good structure resulting from cold working. Therefore, it is necessary to optimize the annealing temperature to effectively eliminate the residual stress without affecting the radial texture of the titanium alloy tube.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a thin-wall high-strength titanium alloy pipe and a preparation method thereof, aiming at overcoming the defects in the prior art, solving the problems that the currently applied aviation hydraulic pipe is low in strength and the high-strength thin-wall pipe is difficult to produce, and obtaining the titanium alloy pipe with high radial texture, high strength and good plasticity.

The invention adopts the following technical scheme:

a preparation method of a thin-wall high-strength titanium alloy pipe comprises the following steps:

s1, selecting a hot-rolled bar drilled pipe blank as a rotary swaging pipe blank directly or obliquely rolling a perforated pipe blank, performing hot extrusion to form the rotary swaging pipe blank, performing cold rotary swaging deformation on the titanium alloy pipe by optimizing pass reduction amount in the rotary swaging process to obtain a radial texture, adjusting the overall deformation amount and deformation mode in the cold rotary swaging process to realize overall regulation and control on the pipe texture, representing the deformation amount of the pipe in the deformation process by using a wall thickness deformation amount, representing the deformation mode by using a wall-reducing and diameter-reducing ratio Q value, displaying the texture strength of the pipe after rotary swaging to be 3.25-5.59 in a polar diagram, and displaying the maximum strength value of an ODF (orientation distribution function) of the texture to be 6.68-10.17;

and S2, adjusting the temperature of the heat treatment after the rotary swaging to remove the residual stress, and obtaining the titanium alloy pipe.

Specifically, step S1 specifically includes:

s101, controlling the extrusion temperature to be 750-920 ℃, and performing hot extrusion to obtain a titanium alloy tube blank;

s102, chamfering the titanium alloy tube blank obtained in the step S101, setting the thickness deformation interval of the rotary swaging wall to be 20% -50% and the Q value interval to be 1-4, and processing the tube blank into titanium alloy tubes with various specifications and sizes according to different rotary swaging passes;

s103, controlling the annealing temperature to be 750-900 ℃, and carrying out intermediate annealing on the titanium alloy pipe subjected to the rotary swaging in the step S102;

and S104, controlling the deformation range of the wall thickness of the rotary swaging to be 20% -50% and the deformation Q value to be 1-4, carrying out rotary swaging on the titanium alloy pipe obtained in the step S103 again, and carrying out acid pickling to obtain the titanium alloy pipe.

Further, in step S102, the number of passes in the cold swaging process is 6 to 15.

Further, in step S1, the swaging deformation range is 40% to 50%.

Specifically, in step S2, the titanium alloy tube after swaging is subjected to vacuum stress relief annealing at 300 to 500 ℃ for 2 to 4 hours.

Further, the vacuum stress removal temperature of the rotary-forged titanium alloy pipe is 400-500 ℃.

Specifically, in step S1, the polar diagram of the swaged titanium alloy tube shows that the texture strength is 4.37-5.59, and the maximum strength value of the orientation distribution function ODF of the texture is 8.49-10.17.

According to another technical scheme, the thin-wall high-strength titanium alloy pipe is prepared according to the method.

Compared with the prior art, the invention has at least the following beneficial effects:

the invention relates to a preparation method of a thin-wall high-strength titanium alloy pipe, which controls the deformation and the deformation mode of the pipe by adjusting and improving the subsequent times, the pressing amount of each pass and even the swaging frequency value by adopting different swaging processes.

Furthermore, the integral regulation and fine regulation of the texture are carried out by optimizing the pass specification design and the process parameters, the material is ensured to have the optimal texture strength and orientation, and the regulation and control of the texture and the performance of the thin-wall high-strength titanium alloy pipe in the cold rotary swaging process can be more accurately realized.

Furthermore, large cold deformation is beneficial to the reorganization of the texture of the pipe in the deformation process, the grain size is reduced along with the increase of the deformation amount, the elongation is increased, and the mechanical property is improved.

Further, in the cold rotary swaging process, the Ti-6Al-4V alloy tube often has large uneven deformation, resulting in residual stress. Generally, the residual stress has important influence on the shape, the fatigue strength and the stress corrosion resistance, so that a proper annealing temperature is needed to be searched, so that the residual stress can be effectively eliminated, and the radial texture of the high-strength alloy pipe such as Ti-6Al-4V is not influenced.

Furthermore, the stress relief temperature is optimized, and a foundation is laid for optimizing heat treatment parameters which must be considered after large cold deformation.

The cold rotary swaging can obviously refine the radial grain size of the titanium alloy pipe and reduce the radial grain size by about 50 percent compared with the original material. In pole figure and ODF characterization results, after cold rotary swaging, the radial texture of the pipe is obviously enhanced, and the tangential texture in the original material is also converted into the radial texture. The microstructure and the mechanical property correspond to each other, and the pipe with the radial texture has higher strength, better wall thickness reduction resistance and excellent fatigue property under biaxial stretching.

In conclusion, the method has no production equipment limitation, is easy to operate and implement, saves cost and has wide application prospect.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

FIG. 1 is a polar view of TC4 tube obtained from different swaging processes, wherein (a) is the raw tube stock, (b) is the tube at 20% swaging deformation, (c) is the tube at 30% swaging deformation, (d) is the tube at 40% swaging deformation, and (e) is the tube at 50% swaging deformation;

FIG. 2 is a graph of the orientation distribution function of TC4 obtained from different swaging processes, wherein (a) is the raw pipe blank, (b) is the pipe with 20% swaging deformation, (c) is the pipe with 30% swaging deformation, (d) is the pipe with 40% swaging deformation, and (e) is the pipe with 50% swaging deformation;

FIG. 3 is a gold phase diagram of TC4 obtained from different swaging processes, wherein (a) is the raw pipe, (b) is the pipe with 20% swaging deformation, (c) is the pipe with 30% swaging deformation, (d) is the pipe with 40% swaging deformation, and (e) is the pipe with 50% swaging deformation.

Detailed Description

The invention provides a thin-wall high-strength titanium alloy pipe and a preparation method thereof, wherein the wall thickness deformation and the Q value are adjusted in the rotary swaging process to carry out integral regulation and control, and the cold rotary swaging deformation is carried out on the pipe to form a radial texture; and then removing the residual stress of the pipe after cold deformation by stress annealing. Compared with the cold rolling process, the deformation of the titanium alloy pipe can reach 50 percent, so that the favorable radial texture of the pipe is enhanced, and the titanium alloy pipe with higher plasticity, strength and fatigue property is obtained. The method provided by the invention can more effectively realize the accurate control of the texture and the performance of the cold rotary swaging high-strength titanium alloy tube, and has the advantages of small production equipment, easy operation and implementation, less deformation energy consumption and wide application prospect.

The invention relates to a preparation method of a thin-wall high-strength titanium alloy pipe, which comprises the following steps:

s1, selecting an annealed hot extruded tube blank, performing cold rotary swaging deformation on the tube blank by optimizing the pass reduction amount in the rotary swaging process to obtain a radial texture, adjusting the integral deformation amount and the deformation mode in the cold rotary swaging process to realize integral regulation and control on the tube blank texture, indicating the main deformation amount of the tube blank in the deformation process by using a wall thickness deformation amount, and indicating the deformation mode by using a Q value;

s101, controlling the extrusion temperature to be 750-920 ℃, and performing hot extrusion to obtain a titanium alloy tube blank;

the titanium alloy tube blank comprises TA; TB-based and TC-based titanium alloys; ti-3Al-2.5V is used in the experiment; Ti-15V-3Cr-3Sn-3Al and Ti-6 Al-4V.

S102, chamfering the titanium alloy tube blank obtained in the step S101, setting the rotary swaging deformation range to be 20% -50%, setting the deformation Q value range to be 1-4, and processing the tube blank into titanium alloy tubes with various specifications and sizes according to different rotary swaging passes;

according to samples with different deformation amounts, different rotary swaging processes are formulated, the subsequent times of the rotary swaging process, the pressing amount of each pass and even the rotary swaging frequency are adjusted and improved, and 6-15 passes are adopted in the cold rotary swaging process.

Preferably, the swaging deformation range is set to 40% to 50%.

S103, controlling the annealing temperature to be 750-900 ℃, and carrying out intermediate annealing on the titanium alloy pipe subjected to the rotary swaging in the step S102;

and S104, controlling the rotary swaging deformation interval to be 20% -50% and the deformation Q value to be 1-4, carrying out rotary swaging on the titanium alloy pipe obtained in the step S103 again, and carrying out acid pickling to obtain the titanium alloy pipe.

Preferably, the swaging deformation range is set to 40% to 50%.

When the diameter reduction process (Q <1) is adopted, a tangential texture is mainly formed; when the wall reduction process (Q >1) is adopted, radial texture is mainly formed.

The tube after rotary swaging forms stronger radial texture, and the crystal grains of the material are obviously refined and uniform.

The pole figure of the swaged pipe shows that the texture strength is 3.25-5.59, preferably 3.32-5.59, and more preferably 4.37-5.59.

The maximum intensity value of the ODF of the texture is 6.68-10.17, preferably 7.8-10.17, and more preferably 8.49-10.17.

And S2, removing residual stress and obtaining the titanium alloy pipe with better comprehensive mechanical property by adjusting the heat treatment temperature after swaging.

S201, performing stress relief annealing on the rotary-forged titanium alloy pipe at 300-500 ℃, and performing heat treatment and heat preservation for 2.5 hours;

the stress removing temperature of the titanium alloy pipe after the rotary swaging is preferably 400-500 ℃, and in the temperature range, the residual stress of the pipe can be effectively removed, and a radial texture which is obtained by cold machining of the pipe and is beneficial to improving the performance of the pipe is reserved.

The research shows that: when the stress removal temperature is lower than 400 ℃, the stress removal effect is not obvious, and when the stress removal temperature is gradually increased to 500 ℃, the residual stress in the material can be completely removed.

S202, preparing the titanium alloy pipe subjected to stress relief annealing into a metallographic test sample and a texture test sample; and testing the residual stress test sample and the mechanical property test sample.

The corrosion liquid used in the preparation of the metallographic test sample has the following composition relation: 10ml of HF: 10ml HNO₃：80ml H₂O。

The corrosion solution used for preparing the sample in the texture testing process comprises the following components: 10ml of HF: 10ml HNO₃：50mlH₂O。

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments 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.

The tubing used in the examples of the present invention was TA 18; TC 4; the TB5 high-strength titanium alloy pipe adopts cold rotary swaging technology in the pipe forming technology.