CN114669700A

CN114669700A - Forging method of ultra-high-strength high-toughness TB18 titanium alloy large-size bar

Info

Publication number: CN114669700A
Application number: CN202210351698.6A
Authority: CN
Inventors: 刘向宏; 冯军; 王涛; 李少强; 王凯旋; 杨晶; 杜予晅; 张新全; 付杰; 何永胜; 崔林林; 李辉; 冯勇; 张平祥; 李波; 秦锋英
Original assignee: Western Superconducting Technologies Co Ltd
Current assignee: Western Superconducting Technologies Co Ltd
Priority date: 2022-04-02
Filing date: 2022-04-02
Publication date: 2022-06-28
Anticipated expiration: 2042-04-02
Also published as: CN114669700B

Abstract

The invention discloses a forging method of a high-strength and high-toughness TB18 titanium alloy large-size bar, which comprises the following steps: firstly, carrying out 1-time cogging forging on an ingot; then, four times of intermediate fire times of re-forging are carried out on the blank; finally, heating the steel bar at the temperature of 40-70 ℃ below the phase transformation point, and performing round forming to obtain the TB18 large-specification bar. In the invention, the wide anvil is used for upsetting in the cogging forging and the round-falling forming stages, so that the forging double-drum phenomenon caused by the narrow anvil is avoided; water cooling is selected during forging above the phase change point, so that crystal grains are fully refined; a V-shaped anvil is adopted during the round-throwing forming, so that the blank is uniformly deformed during the round-throwing, and the regular shape of the finished bar is ensured; and controlling corresponding temperature and forging ratio in each stage, finally obtaining the TB18 large-size bar with uniform and fuzzy macrostructure and uniform and fine macrostructure, and through mechanical test, the tensile strength, the impact toughness and the fracture toughness of the TB18 large-size bar can meet the use requirements of the service environment of the aviation aircraft.

Description

Forging method of ultra-high-strength and high-toughness TB18 titanium alloy large-size bar

Technical Field

The invention belongs to the technical field of nonferrous metal processing, and particularly relates to a forging method of a TB18 titanium alloy large-size bar with ultrahigh strength and toughness, which is particularly suitable for producing a TB18 titanium alloy large-size bar (phi is not less than 100mm and not more than 400mm) with good structural uniformity.

Background

The existing high-strength titanium alloy mainly comprises TC18, Ti1023, Ti55531 and the like, after heat treatment, the strength can reach 1100-1200 MPa, and the fracture toughness can reach 50-60 MPa.m^1/2On the other hand, although the mechanical properties of the alloy are relatively high, the requirement of the aviation field on ultrahigh-strength and high-toughness titanium alloy is still difficult to meet, and the alloy is required to have the strength of more than 1280MPa and the fracture toughness of not less than 65 MPa.m^1/2And the like, and has good comprehensive mechanical properties. Particularly, the key bearing members of the aviation equipment, such as bearing frames and beams on the airframe, are the 'ridge beams' of the aircraft, and play an important role in ensuring the development and capacity of the aviation equipment.

Based on the reasons, the inventor independently develops the ultra-high strength and high toughness titanium alloy TB18 (the nominal component is Ti-4Al-5Mo-5V-5Cr-1Nb), which is a typical metastable beta type titanium alloy, the phase change point of the alloy is about 800 ℃, the alloy is prepared by trial production of small-specification bars through the traditional forging method, the structural uniformity of the alloy is good through detection, and the mechanical property of the alloy can completely meet the requirement of a key bearing component of aviation equipment.

However, with the establishment of advanced warplanes and mass transport in China and the development of large commercial airplanes, the requirement for large-diameter materials is increased, so that the specification requirement for the bars is increased, and in order to meet various performance indexes of aviation equipment, the performance requirement for large-size bars is not reduced, but the inspection standard for small-size bars is adopted. Therefore, when the specification of the required bar is larger and larger, the high requirement on the preparation level of the large-specification bar is provided, particularly for the large-specification TB18 titanium alloy bar with the diameter of 100mm and phi of 400mm, the deformation temperature of the alpha + beta phase region is about 40-60 ℃ below the phase change point, the forging temperature is lower, the deformation resistance of the two phase regions is increased violently, the forging permeability of the deformation center is poor, the deformation rate is higher, the overheating of the material is easy to cause, if the deformation rate is lower, the uniformity of the tissues of different parts is poorer, the deformation is smaller or the heating temperature is higher, and the good tissue refining effect is difficult to realize. That is, according to the conventional forging method for producing small-size TB18, a large-size bar of the ultra-high strength and high toughness titanium alloy TB18 cannot be produced.

In view of the above, the present inventors propose a forging method for a large-sized TB18 titanium alloy bar with ultra-high strength and toughness, so as to overcome the defects in the prior art.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the forging method of the ultra-high-strength and high-toughness TB18 titanium alloy large-size bar, the forging method starts from a processing technology, improves the uniformity of the structure, improves the comprehensive mechanical property of the titanium alloy, and can successfully produce the ultra-high-strength and high-toughness titanium alloy bar with the tensile strength of more than 1300MPa and the impact toughness of more than 25J/cm²Fracture toughness of more than 65 MPa.m^1/2The diameter of the TB18 titanium alloy bar is not less than 100mm and not more than 400 mm.

The purpose of the invention is solved by the following technical scheme:

a forging method of a high-strength and high-toughness TB18 titanium alloy large-size bar is characterized in that a TB18 titanium alloy 5-7 ton-grade ingot is produced by adopting a vacuum consumable arc furnace as a raw material of the TB18 titanium alloy large-size bar, and the ingot comprises the following chemical components in percentage by mass: al: 3.7% -5.0%, Mo: 4.7% -6.0%, V: 4.5% -5.5%, Cr: 4.5% -6.0%, Nb: 0.5% to 2.0% and the balance titanium and inevitable impurity elements, characterized in that the forging method comprises the steps of:

step one, cogging and forging:

1, cogging and forging the cast ingot for 1 time, wherein the cogging and forging adopt a two-upsetting and two-drawing mode, and water cooling is adopted after forging;

step two, intermediate forging:

performing secondary forging on the blank subjected to cogging forging in the first step for 2-4 times above a phase transformation point, further crushing as-cast crystal grains and homogenizing the structure of the blank, selecting a reversing upsetting mode in the secondary forging process for improving forging permeability of the center of the blank, and performing water cooling on the blank to obtain a first intermediate forged blank;

carrying out 1-3 times of fire forging change on the blank subjected to the first intermediate forging below the phase transformation point, wherein the drawing length is selected in the forging change process, and the cooling mode is air cooling to obtain a blank subjected to second intermediate forging;

carrying out 1-3 times of hot forging on the blank subjected to the second intermediate forging above the phase transformation point, selecting upsetting and drawing in the forging changing process for refining the core structure, and carrying out water cooling in a cooling mode to obtain a third intermediate forged blank;

forging the blank subjected to the third intermediate forging for 4-7 times at the temperature below the phase transformation point, further refining the structure of grains and homogenizing the blank, selectively drawing out the blank in the forging process, carrying out inverse-eight-direction treatment on the blank after forging, and carrying out air cooling in the cooling mode to obtain a blank subjected to the fourth intermediate forging;

step three, forging a finished product:

and (3) heating the blank forged in the second and fourth steps at the temperature of 40-70 ℃ below the phase transformation point for forming forging, wherein the forming forging is completed by 1-2 times of fire, and air cooling is adopted after forging to obtain the TB18 titanium alloy bar.

Further, the heating temperature of the blank opening forging in the first step is 1100-1200 ℃, the heat preservation time is 10-30 hours, the forging ratio is controlled to be 1.5-2.5, and an anvil with the thickness of 600-1200 mm is used for forging the cast ingot.

Furthermore, in the first intermediate forging modification process in the second step, the heating temperature is 150-300 ℃ above the phase transformation point every time, the materials are discharged from the furnace and then are subjected to reversing upsetting and drawing out in sequence, and the forging ratio every time is controlled to be 1.5-2.5.

Furthermore, in the second intermediate forging in the second step, heating temperature is 40-60 ℃ below the phase change point in each fire, drawing is carried out after the material is discharged, and the forging ratio in each fire is controlled to be 1.2-2.2.

Furthermore, in the third intermediate forging in the second step, heating temperature is 60-150 ℃ above the phase transformation point every time, upsetting and drawing are sequentially carried out after the materials are discharged from the furnace, the forging ratio is controlled to be 1.5-2.5 every time, and upsetting and drawing are carried out on the blank by using an anvil tool of 600-1200 mm.

Furthermore, in the fourth intermediate forging in the second step, heating temperature is 40-60 ℃ below the phase change point every time, drawing is sequentially carried out after materials are discharged from a furnace, and the forging ratio every time is controlled to be 1.2-2.2.

Furthermore, the forging ratio during the forming forging in the third step is controlled to be 1.0-2.0, and a V-shaped anvil is selected to carry out the rounding forming on the blank.

Further, the forging method is used for producing TB18 titanium alloy bars with the diameter of 100-400 mm, the tensile strength of the bars is larger than 1300MPa, and the impact toughness of the bars is larger than 25J/cm²Fracture toughness of more than 65 MPa.m^1/2。

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

the forging method of the ultra-high strength and toughness TB18 titanium alloy large-size bar adopts the preparation process route of cogging forging → forging above the phase change point → forging below the phase change point → finished product forging, combines the adaptive process parameters, uses a wide anvil to upset in the cogging forging and the round-falling forming stages, avoids the forging double-drum phenomenon caused by the narrow anvil, and can ensure that the cast ingot carries out integral plastic deformation; water cooling is selected during forging above the phase change point, so that crystal grains are fully refined; when the round bar is thrown, a V-shaped anvil is selected, so that the bar can be uniformly deformed, and the regular shape of the finished bar is ensured; in the second step, the titanium alloy blank is subjected to inverse octagonal processing after being forged, so that the phenomena of large specification of the blank, rapid temperature drop at sharp edges and corners and uneven distribution of the temperature field of the blank are avoided; in addition, in the second step, through the first middle forging and the third middle forging, through deformation and recrystallization heating, the blank is ensured to obtain a homogenized structure, and finally, a TB18 titanium alloy large-sized bar with uniform and fuzzy macrostructure and uniform and fine macrostructure is obtained, and in addition, the mechanical property test is carried out on the bar actually produced, the tensile strength (Rm) is more than 1300MPa, and the impact toughness (aku) is more than 25J/cm²A fracture toughness (KIC) of more than 65MPa m^1/2Satisfy the aviation aircraftService environment use requirements.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.

FIG. 1 is a flow chart of a forging method of a high-strength and high-toughness TB18 titanium alloy large-size bar;

FIG. 2 is a macrostructure diagram of a bar of 400mm diameter prepared in example 1 of the present invention;

FIG. 3 is a side microstructure of a bar of 400mm diameter prepared in example 1 of the present invention;

FIG. 4 is a r/2 section microstructure of a bar of 400mm diameter prepared in example 1 of the present invention;

FIG. 5 is a microstructure diagram of a core of a phi 400mm bar prepared in example 1 of the present invention;

FIG. 6 is a macrostructure diagram of a bar of phi 210mm prepared in example 2 of the present invention;

FIG. 7 is a graph of the edge microstructure of a bar of phi 210mm prepared in example 2 of the present invention;

FIG. 8 is a r/2 section microstructure of a bar of 210mm diameter prepared in example 2 of the present invention;

FIG. 9 is a microstructure diagram of a 210mm diameter bar core prepared in example 2 of the present invention.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of devices consistent with certain aspects of the invention, as detailed in the appended claims.

In order to make those skilled in the art better understand the technical solution of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings and examples.

Referring to fig. 1, the invention provides a forging method of a high-strength and high-toughness TB18 titanium alloy large-size bar, wherein a TB18 titanium alloy 5-7 ton-grade ingot is produced by a raw material of the TB18 titanium alloy large-size bar in a vacuum consumable arc furnace, and the ingot comprises the following chemical components in percentage by mass: al: 3.7% -5.0%, Mo: 4.7% -6.0%, V: 4.5% -5.5%, Cr: 4.5% -6.0%, Nb: 0.5% to 2.0% and the balance titanium and inevitable impurity elements, characterized in that the forging method comprises the steps of:

step one, cogging and forging:

the method comprises the following steps of 1-step forging the TB18 titanium alloy ingot for cogging, wherein the forging heating temperature is 1100-1200 ℃, heating for 10-30 hours, discharging, carrying out primary two-upsetting two-drawing deformation on the ingot, controlling the forging ratio to be 11.5-2.5, forging the ingot by using an anvil with the thickness of 600-1200 mm, ensuring integral plastic deformation during cogging of the ingot, avoiding the use of an anvil with a smaller width, avoiding the double-drum phenomenon during upsetting, and carrying out water cooling after forging.

Step two, intermediate forging:

performing first intermediate forging change on the cast ingot subjected to cogging forging in the first step above a phase transformation point, wherein the forging change fire time is 2-4 times, the heating temperature of each time is 150-300 ℃ above the phase transformation point, reversing upsetting and drawing out the material after the material is discharged from the furnace, the forging ratio of each time is controlled to be 1.5-2.5, further crushing the as-cast structure and homogenizing the structure of the blank, and performing water cooling after forging to obtain a blank subjected to first intermediate forging;

performing second intermediate forging change on the blank subjected to the first intermediate forging change below a phase change point, wherein the forging change fire is 1-3 times, the heating temperature is 40-60 ℃ below the phase change point each time, drawing out the material after discharging the material, the forging ratio of each time is controlled to be 1.2-2.2, and air cooling is adopted after forging to obtain a blank subjected to second intermediate forging;

carrying out third intermediate forging modification on the blank subjected to the second intermediate forging modification above the phase transformation point, wherein the forging modification fire time is 1-3 fires, the heating temperature of each firing time is 60-150 ℃ above the phase transformation point, upsetting and drawing out are sequentially carried out after the material is discharged from the furnace, the forging ratio of each firing time is controlled to be 1.5-2.5, upsetting and drawing out are carried out by using a wide anvil (600-1200 mm), and water cooling is adopted after forging to obtain a blank subjected to third intermediate forging;

and (3) performing fourth intermediate forging change on the blank subjected to third intermediate forging change below the phase transformation point, wherein the forging change fire is 4-7 times, the heating temperature is 40-60 ℃ below the phase transformation point in each time, drawing and inverting eight directions of the material after discharging the material, the forging ratio in each time is controlled to be 1.2-2.2, and air cooling is adopted after forging to obtain the blank subjected to fourth intermediate forging.

Step three, forging a finished product:

and (3) heating the blank forged in the middle of the second step and the fourth step at the temperature of 40-70 ℃ below the phase transition point, performing round-falling forming, wherein the forging ratio is controlled to be 1.0-2.0 when the round-falling is completed by 1-2 times of fire, selecting a V-shaped anvil during the round-falling, and performing air cooling after forging to obtain the TB18 titanium alloy bar.

To further verify the efficacy of the forging method of the present invention, the inventors conducted the following specific examples:

example 1

1) Cogging and forging:

the heating temperature of ingot cogging forging is 1170 ℃, heating is carried out for 20 hours, then discharging is carried out, the ingot is subjected to two-upsetting and two-drawing deformation by using an anvil with the specification of 800mm width, the forging ratio is 2.0, and water cooling is adopted after forging.

2) Intermediate forging:

and (2) carrying out first intermediate forging change on the cast ingot subjected to cogging forging in the step 1) above a phase transformation point, changing the forging fire time to 3 times, selecting the heating temperature above the phase transformation point for each time at 300 ℃, carrying out reversing upsetting and drawing out the material after discharging the material out of the furnace, controlling the forging ratio at about 1.8 for each time, further crushing the as-cast structure and homogenizing the structure of the blank, and carrying out water cooling after forging.

And (3) performing second intermediate forging change on the blank subjected to the first intermediate forging change below the phase change point, changing the forging fire number to 2, selecting the heating temperature below the phase change point for each fire number to perform 40 ℃, discharging the material out of the furnace, sequentially performing drawing treatment, controlling the forging ratio of each fire number to be 1.7, and performing air cooling after forging.

And (3) performing third intermediate forging change on the blank subjected to the second intermediate forging change above the phase change point, changing the forging heat number to 1, selecting the heating temperature of 150 ℃ above the phase change point for each heat number, sequentially performing upsetting and drawing after discharging the material from the furnace, controlling the forging ratio of each heat number to about 1.6, performing upsetting and drawing by using a 800mm wide anvil, and performing water cooling after forging.

And (3) performing fourth intermediate forging change on the blank subjected to third intermediate forging change below the phase change point, changing the forging fire number to 5, selecting the heating temperature below the phase change point for each fire number to perform 40 ℃, drawing out and reversing eight directions after discharging the material, controlling the forging ratio between 1.6 for each fire number, and performing air cooling after forging.

3) Forging a finished product:

heating the bar forged in the middle of the step 2) below the phase change point at 40 ℃, performing round-falling forming, wherein the round-falling forming is completed by 2 times, the forging ratio is controlled to be 1.5 during the round-falling, a V-shaped anvil is selected during the round-falling, the bar is forged to the finished product size phi of 400mm, and the TB18 titanium alloy bar is obtained by air cooling after the forging.

Wherein, fig. 2 is the macroscopic structure diagram of the finished product of the bar material with the phi 400mm specification prepared by the forging of the process in the embodiment 1, and the macroscopic structure is mainly characterized by fine fuzzy crystals, which shows that the bar material is fully deformed above the phase transition point. FIGS. 3 to 5 are the microstructure diagrams of the edge, r/2 and center of the bar, respectively, the microstructure is basically composed of a beta matrix and a spherical alpha phase. A sample of the obtained large-size bar is subjected to heat treatment, and the mechanical property of the large-size bar is tested, and the result is shown in Table 1.

TABLE 1 tabulation of mechanical properties of bar material with 400mm diameter

Example 2

1) Cogging and forging:

the heating temperature for cogging and forging the cast ingot is 1150 ℃, the cast ingot is discharged after being heated for 15 hours, the cast ingot is subjected to two-upsetting and two-drawing deformation by using an anvil with the specification of 600mm width, the forging ratio is 2.2, and water cooling is adopted after forging.

2) Intermediate forging:

carrying out first intermediate forging change on the cast ingot subjected to cogging forging in the step 1) above a phase transformation point, changing forging fire times to 2 fire times, selecting heating temperature of 200 ℃ above the phase transformation point for each fire time, carrying out reversing upsetting and drawing out the material after discharging the material out of the furnace, controlling the forging ratio of each fire time to be about 2.0, further crushing an as-cast structure and homogenizing the structure of the blank, and carrying out water cooling after forging.

And (3) performing second intermediate forging change on the blank subjected to the first intermediate forging change below the phase change point, changing the forging fire number to 3, selecting the heating temperature below the phase change point for each fire number to be 60 ℃, discharging the material out of the furnace, sequentially performing drawing treatment, controlling the forging ratio of each fire number to be 1.8, and performing air cooling after forging.

And (3) performing third intermediate forging change on the blank subjected to the second intermediate forging change above the phase change point, changing the forging fire time to 2 times, selecting the heating temperature of 80 ℃ above the phase change point for each time, sequentially upsetting and drawing out the material after discharging the material from the furnace, controlling the forging ratio of each time to be 1.5, upsetting and drawing out the material by using an anvil with the width of 800mm, and performing water cooling after forging.

And (3) performing fourth intermediate forging change on the blank subjected to third intermediate forging change below the phase change point, changing the forging fire number to 7, selecting the heating temperature below the phase change point for each fire number to be 60 ℃, discharging the material, then sequentially performing stretching and reverse eight-direction treatment, controlling the forging ratio at about 1.5 for each fire number, and performing air cooling after forging.

3) Forging a finished product:

heating the bar subjected to intermediate forging in the step 2) below a phase transition point at 70 ℃, performing round-falling forming, wherein the round-falling forming is completed by 2 fire times, the forging ratio is controlled to be 1.3 during the round-falling, a V-shaped anvil is selected during the round-falling, the bar is forged to a finished product size of phi 210mm, and the TB18 titanium alloy bar is obtained by air cooling after the forging.

FIG. 6 is a macroscopic structure diagram of a finished bar with a diameter of 200mm prepared by forging in example 2 by the process, and it can be seen that the macroscopic structure has fine fuzzy crystals as the main characteristic, which shows that the bar is sufficiently deformed above the phase transition point. FIGS. 7 to 9 are the microstructure diagrams of the edge, r/2 and center of the bar, respectively, the microstructure is basically composed of a beta matrix and a spherical alpha phase. A sample of the obtained large-size bar is subjected to heat treatment, and the mechanical property of the large-size bar is tested, and the result is shown in Table 2.

TABLE 2 tabulation of mechanical properties of bar material with 210mm diameter

In summary, the data in tables 1 and 2 show that the TB18 titanium alloy forged by the process of the invention (phi 400mm and phi 210mm specification bars) has good matching of room temperature strength, impact toughness and fracture toughness, the tensile strength (Rm) is greater than 1300MPa, and the impact toughness (aku) is greater than 25J/cm²The fracture toughness (KIC) is more than 65 MPa.m^1/2And the service requirement of the aviation aircraft in service environment can be completely met.

The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention.

It is to be understood that the present invention is not limited to what has been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims

1. A forging method of a high-strength and high-toughness TB18 titanium alloy large-size bar is characterized in that a TB18 titanium alloy 5-7 ton-grade ingot is produced by adopting a vacuum consumable arc furnace as a raw material of the TB18 titanium alloy large-size bar, and the ingot comprises the following chemical components in percentage by mass: al: 3.7% -5.0%, Mo: 4.7% -6.0%, V: 4.5% -5.5%, Cr: 4.5% -6.0%, Nb: 0.5% to 2.0% and the balance titanium and inevitable impurity elements, characterized in that the forging method comprises the steps of:

step one, cogging and forging:

step two, intermediate forging:

performing 1-3 times of heating forging on the blank subjected to the second intermediate forging above the phase transformation point, selecting upsetting in the forging process for refining the core part structure, and performing water cooling in a cooling mode to obtain a blank subjected to third intermediate forging;

step three, forging a finished product:

2. The forging method of the ultra-high strength and toughness TB18 titanium alloy large-size bar according to claim 1, wherein in the first step, the cogging forging heating temperature is 1100-1200 ℃, the holding time is 10-30 hours, the forging ratio is controlled to be 1.5-2.5, and an anvil with the thickness of 600-1200 mm is used for forging the ingot.

3. The forging method of the ultra-high strength and toughness TB18 titanium alloy large-size bar according to claim 1, wherein in the first intermediate forging in the second step, the heating temperature is 150-300 ℃ above the phase transition point every fire, the material is discharged from the furnace and then is subjected to reversing upsetting and drawing out in sequence, and the forging ratio every fire is controlled to be 1.5-2.5.

4. The forging method of the ultra-high-strength-toughness TB18 titanium alloy large-size bar according to claim 1, wherein in the second intermediate forging step in the second step, the heating temperature is 40-60 ℃ below the phase change point every fire, drawing out is performed after discharging the material, and the forging ratio is controlled to be 1.2-2.2 every fire.

5. The forging method of the ultra-high strength and toughness TB18 titanium alloy large-size bar according to claim 1, wherein in the third intermediate forging in the second step, the heating temperature is 60-150 ℃ above the transformation point every fire, the upsetting and the drawing out are sequentially performed after the material is discharged from the furnace, the forging ratio is controlled to be 1.5-2.5 every fire, and an anvil with the thickness of 600-1200 mm is used for upsetting and drawing out the blank.

6. The forging method of the ultra-high strength and toughness TB18 titanium alloy large-size bar according to claim 1, wherein in the fourth intermediate forging in the second step, the heating temperature is 40-60 ℃ below the transformation point every fire, the material is drawn out of the furnace and then sequentially elongated, and the forging ratio of each fire is controlled to be 1.2-2.2.

7. The forging method of the ultra-high-strength-toughness TB18 titanium alloy large-size bar according to claim 1, wherein the forging ratio during the forming forging in the third step is controlled to be 1.0-2.0, and a V-shaped anvil is selected to perform rounding forming on the blank.

8. The forging method of the ultra-high strength and toughness TB18 titanium alloy large-size bar according to any one of claims 1 to 7, wherein the forging method is used for producing a TB18 titanium alloy bar with the diameter of 100-400 mm, the tensile strength of the bar is greater than 1300MPa, and the impact toughness of the bar is greater than 25J/cm²Fracture toughness of more than 65 MPa.m^1/2。