CN114457259A

CN114457259A - Fine-grain TC4 titanium alloy bar and preparation method thereof

Info

Publication number: CN114457259A
Application number: CN202210075927.6A
Authority: CN
Inventors: 刘向宏; 王凯旋; 张小航; 王文盛; 陈海生; 田彦文; 陈小苗
Original assignee: Western Superconducting Technologies Co Ltd
Current assignee: Western Superconducting Technologies Co Ltd
Priority date: 2022-01-23
Filing date: 2022-01-23
Publication date: 2022-05-10

Abstract

The invention belongs to the technical field of titanium alloy processing, and particularly relates to a fine-grained TC4 titanium alloy bar and a preparation method thereof, which are suitable for industrial production of fine-grained TC4 titanium alloy ingots with the specification of phi 280-phi 920 mm. By adding trace P element and S element in the allowed range of the national standard of TC4 titanium alloy, the beta grain size of the TC4 titanium alloy bar can be rapidly refined through subsequent forging. According to the fine-grain TC4 titanium alloy bar prepared by the preparation method, under the same forging deformation, the average grain size of beta grains can be improved by 4-5 levels, the average grain size of the beta grains is reduced by 50-80%, and the beta grain size of the bar is not larger than 1 mm.

Description

Fine-grain TC4 titanium alloy bar and preparation method thereof

Technical Field

The invention belongs to the technical field of titanium alloy processing, relates to a TC4 titanium alloy bar, and particularly relates to a fine-grain TC4 titanium alloy bar and a preparation method thereof.

Background

The TC4 titanium alloy has the nominal component of Ti-6Al-4V, is an alloy developed in the United states in 1954, is a King brand alloy in the titanium alloy industry due to good heat resistance, strength, toughness, formability, weldability, corrosion resistance and biocompatibility, and accounts for 75-85% of the total titanium alloy.

At present, most TC4 titanium alloy products are produced by forging or rolling, thick columnar grains of a TC4 titanium alloy ingot are required to be fully deformed to refine beta grains, the required deformation amount is not less than 80% under general conditions, and the required deformation amount is more than 300% to meet the use requirements if some severe military standards are met. Therefore, how to rapidly refine the as-cast structure of the TC4 titanium alloy ingot to reduce the manufacturing cost is one of the important research directions in the titanium alloy processing industry.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a titanium alloy bar with a fine crystalline structure TC4 and a preparation method thereof.

In order to achieve the purpose, the invention provides the following technical scheme:

on one hand, the invention provides a fine-grain structure TC4 titanium alloy bar, which is prepared by adding P element and S element into TC4 titanium alloy and controlling the mass ratio of the P element to the S element to be (1-40): (1-10).

Further, the content of the P element is 0.0005 to 0.02%, and the content of the S element is 0.0005 to 0.005%.

Further, the P element is added by adopting an AlV alloy containing the P element, and the S element is added by adopting an AlV alloy containing the S element.

On the other hand, the invention also provides a preparation method of the titanium alloy bar based on part or all of the fine-grain structure TC4, which specifically comprises the following steps:

1) preparing an electrode block: the method comprises the following steps of (1) using an AlV alloy containing a P element and an AlV alloy containing an S element, wherein the addition amount of the P element is 0.0005-0.02%, the addition amount of the S element is 0.0005-0.005%, and the rest components are added according to the proportion of TC4 titanium alloy national standard requirements;

2) welding the consumable electrode: carrying out assembly welding on the electrode block obtained in the step 1) to obtain a consumable electrode;

3) carrying out three times of vacuum melting on the consumable electrode obtained in the step 2) by adopting a vacuum consumable electric arc furnace to obtain a TC4 titanium alloy ingot;

4) heating the TC4 titanium alloy ingot obtained in the step 3) above a phase transformation point to 1010-1200 ℃ for 2-time upsetting forging, keeping the temperature for 120-1000 min, discharging, upsetting forging, controlling the total deformation at 30-80% to break an as-cast structure; heating to T below the transformation point_βForging for 2-4 times at the temperature of minus 30-80 ℃, controlling the total deformation amount to be 30-70%, and air-cooling after forging to obtain the TC4 titanium alloy bar with uniform structure.

Further, compared with the average beta crystal grain size of the TC4 titanium alloy bar which is not added with the P element and the S element, the average beta crystal grain size of the TC4 titanium alloy bar added with the P element and the S element is improved by 4-5 grades and is reduced by 50-80 percent through the same total forging deformation amount.

Further, compared with the TC4 titanium alloy bar without the P element and the S element, if the TC4 titanium alloy bar with the P element and the S element added is the bar with the same size, the average grain size of beta grains is achieved, and the total forging deformation amount required by adding is reduced by 25% -50% compared with that without adding.

Further, the electrode block in the step 1) is pressed into an electrode by adopting a large hydraulic press.

Further, the welding current of the electrode block in the step 2) is 180-400A, and the welding voltage is 25-45V.

Further, the specific parameters of the third vacuum melting in the step 3) are as follows:

smelting for the first time: the specification of the crucible is phi 160 mm-phi 640mm, the vacuum degree before melting is less than or equal to 2.0Pa, the gas leakage rate is less than or equal to 1.0Pa/min, the melting voltage is 30V-40V, the melting current is 8 kA-24 kA, the arc stabilizing current is 3.0A-14.0A, and the cooling time is 6 h-10 h;

smelting for the second time: the specification of the crucible is phi 220 mm-phi 850mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.8Pa/min, the melting voltage is 34V-40V, the melting current is 10 kA-28 kA, the arc stabilizing current is 5.0A-16.0A, and the cooling time is 6 h-12 h;

smelting for the third time: the specification of the crucible is phi 280 mm-phi 920mm, the vacuum degree before melting is less than or equal to 1.8Pa, the air leakage rate is less than or equal to 0.5Pa/min, the melting voltage is 34V-40V, the melting current is 5 kA-28 kA, the arc stabilizing current is 8.0A-18.0A, and the cooling time is 6 h-12 h.

Further, the beta grain size of the TC4 titanium alloy bar obtained by forging in the step 4) is not more than 1 mm.

Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects: the method is characterized in that trace P elements and S elements are added on the basis of the existing TC4 titanium alloy, and the mass ratio of the trace P elements to the S elements is controlled to be (1-4): (1-10), P element and S element are utilized to weaken the grain boundary bonding force of the titanium alloy, and convenience is brought to the upsetting-drawing forging process of subsequent preparation. Although the P element is generally regarded as a harmful impurity, the present invention can improve the endurance and creep properties of the titanium alloy by controlling the P element within a certain content range. In addition, if the average grain size of the beta grains with the same size is to be achieved, the total forging deformation amount required by adding the trace P element and the S element fine-grain structure TC4 titanium alloy bar is reduced by 25-50% compared with the case of no addition, and through the same forging deformation amount, the average grain size of the beta grains is improved by 4-5 levels compared with the case of no addition, and the average grain size of the beta grains is reduced by 50-80%.

In addition, the preparation method adopts a single electrode to mix materials before the electrode is pressed, and the materials are fully and uniformly mixed; the electrode block completes the whole electrode welding process in a non-tungsten electrode vacuum plasma welding box, thereby avoiding the pollution of tungsten or other impurities and the oxidation of the electrode; the vacuum consumable electrode arc furnace is adopted for carrying out three times of smelting, parameters such as vacuum degree, gas leakage rate and the like are strictly controlled in the smelting process, so that the transverse and longitudinal uniformity of the components of the whole cast ingot is improved, the technology for controlling the uniformity of the chemical components of industrial large-scale cast ingots of 1 ton to 8 ton is successfully broken through, and the vacuum consumable electrode arc furnace is suitable for industrial production of the TC4 titanium alloy cast ingot with the fine grain structure of phi 280 mm-phi 920 mm.

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 schematic longitudinal 5-point sampling view of a TC4 titanium alloy ingot prepared by the preparation method provided by the invention;

FIG. 2 is a photograph of a macrostructure of a common TC4 titanium alloy bar;

FIG. 3 is a photograph of a high magnification structure of a common TC4 titanium alloy bar;

fig. 4 is a microstructure photograph of a conventional TC4 titanium alloy bar subjected to beta grain size examination.

FIG. 5 is a photograph of the macrostructure of a bar obtained in example 1 of the present invention;

FIG. 6 is a photograph of a high magnification structure of a bar obtained in example 1 of the present invention;

FIG. 7 is a photograph of the microstructure of a bar obtained in example 1 of the present invention examined for the beta crystal grain size;

FIG. 8 is a photograph of the macrostructure of a bar obtained in example 2 of the present invention;

FIG. 9 is a photograph of a high magnification structure of a bar obtained in example 2 of the present invention;

FIG. 10 is a photograph of the microstructure of a bar obtained in example 2 of the present invention examined for the beta crystal grain size.

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 methods consistent with certain aspects of the invention, as detailed in the appended claims.

The invention provides a fine-grain TC4 titanium alloy bar, which is prepared by adding P element and S element into TC4 titanium alloy and controlling the mass ratio of the P element to the S element to be (1-40): (1-10).

Furthermore, the P element is added by adopting an AlV alloy containing the P element, the S element is added by adopting an AlV alloy containing the S element, the P element and the S element can be uniformly distributed by adopting the adding mode, and the segregation of the alloy elements caused by the uncontrollable adding amount of the P element and the S element can be avoided.

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.

Example 1

The embodiment provides a preparation method of a titanium alloy bar with a fine crystalline structure TC4, which specifically comprises the following steps:

1) preparing an electrode block: the method comprises the following steps of (1) using an AlV alloy containing a P element and an AlV alloy containing an S element, wherein the addition amount of the P element is 0.0005%, the addition amount of the S element is 0.0005%, and the rest components are added according to the proportion of TC4 titanium alloy national standard requirements;

2) welding the consumable electrode: clamping the electrode block obtained in the step 1) by using a clamp, and welding the electrode block into a consumable electrode by using a non-tungsten argon protection plasma welding box;

3) carrying out three times of vacuum melting on the consumable electrode obtained in the step 2) by adopting a vacuum consumable electric arc furnace:

smelting for the first time: the specification of the crucible is phi 160mmmm, the vacuum degree before melting is less than or equal to 2.0Pa, the gas leakage rate is less than or equal to 1.0Pa/min, the melting voltage is 30V, the melting current is 8kA, the arc stabilizing current is 3.0A, and the cooling time is 6 h;

smelting for the second time: the specification of the crucible is phi 220mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.8Pa/min, the melting voltage is 34V, the melting current is 10kA, the arc stabilizing current is alternating current at 5.0A, and the cooling time is 6 h;

smelting for the third time: the specification of the crucible is phi 280mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.5Pa/min, the melting voltage is 34V, the melting current is 5kA, the arc stabilizing current is 8.0A, and the cooling time is 6h, thus obtaining the fine grain structure TC4 titanium alloy ingot with the specification of phi 280 mm.

4) Heating the fine-grained TC4 titanium alloy ingot with the diameter of 280mm obtained in the step 3) above a phase transformation point to 1100 ℃ for the 1 st fire upsetting forging, keeping the temperature for 200min, discharging, upsetting forging, controlling the deformation at 15%, and cooling in air after forging; heating to 1050 ℃ above the phase transformation point, performing 2 nd heating upsetting-drawing forging, keeping the temperature for 200min, discharging, upsetting-drawing forging, controlling the deformation at 15%, and cooling in air after forging; heating to T below the transformation point_βCarrying out 3 rd-time forging at the temperature of minus 30 ℃, controlling the deformation to be 15%, and cooling in air after forging; heating to T below the transformation point_βAnd (3) carrying out 4 th-time forging at the temperature of minus 40 ℃, controlling the deformation to be 15%, and carrying out air cooling after forging to obtain the TC4 titanium alloy bar with uniform structure.

According to the figure 1, the longitudinal head, upper, middle, lower and tail 5 points of the TC4 titanium alloy 1 ton grade industrial ingot with the specification of phi 280mm prepared by the embodiment are sampled, and the chemical composition detection is listed in the table 1. Finally, a TC4 titanium alloy bar with a diameter of 300mm is prepared through ingot cogging and forging, fig. 5 is a macroscopic structure photograph of the bar obtained in this example, fig. 6 is a macroscopic structure photograph of the bar obtained in this example, and fig. 7 is a microscopic structure photograph of the bar obtained in this example, which is subjected to β grain size inspection.

TABLE 1 chemical composition List of longitudinal 5-point of fine-grained TC4 Ti alloy ingot with phi 280mm specification

Chemical elements wt%	Al	V	O	P	S	Ti
							Head with a rotatable shaft	6.05	4.08	0.17	0.0005	0.0005	Bal.
On the upper part	6.01	4.08	0.17	0.0005	0.0005	Bal.
							In	6.04	4.08	0.18	0.0005	0.0005	Bal.
Lower part	6.01	4.08	0.18	0.0005	0.0005	Bal.
							Tail	6.06	4.08	0.18	0.0006	0.0006	Bal.

As can be seen from the test results in Table 1: the titanium alloy ingot with the phi-280 mm fine crystal structure TC4 produced by the preparation process provided by the invention has uniform components and is suitable for industrial production.

Comparative example 1

Compared with the common TC4 alloy (trace P and S elements are not added), referring to fig. 2-4, the fine-grain TC4 titanium alloy bar prepared by the preparation method provided by the invention is referring to fig. 5-7, and the comparison between fig. 2 and 5, fig. 3 and 6, and fig. 4 and 7 shows that after the trace P and S elements are added, the average grain size of beta grains of the bar is improved by 4-5 grades compared with that without the addition, and the average grain size of the beta grains is reduced by 50-80% after the bar is subjected to the same forging deformation. .

Example 2

1) preparing an electrode: the P-containing AlV alloy and the S-containing AlV alloy were used, and the amount of P element added was 0.0200% and the amount of S element added was 0.0050%. The other components are added according to the proportion required by the national standard of TC4 titanium alloy;

smelting for the first time: placing the consumable electrode obtained in the step 2) in a crucible with the specification of phi 160mmmm, wherein the vacuum degree before melting is less than or equal to 2.0Pa, the gas leakage rate is less than or equal to 1.0Pa/min, the melting voltage is 40V, the melting current is 24kA, the arc stabilizing current is 14.0A, and the cooling time is 10 h;

smelting for the second time: the specification of the crucible is phi 850mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.8Pa/min, the melting voltage is 34V, the melting current is 28kA, the arc stabilizing current is alternating current at 16.0A, and the cooling time is 12 h;

smelting for the third time: the specification of the crucible is phi 920mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.5Pa/min, the melting voltage is 40V, the melting current is 28kA, the arc stabilizing current is 18.0A, and the cooling time is 12h, thus obtaining the fine grain structure TC4 titanium alloy ingot with the specification of phi 920 mm;

4) heating the fine grain TC4 titanium alloy ingot with the specification of phi 920mm obtained in the step 3) to 1200 ℃ above the phase transformation point, carrying out 1 st fire upsetting forging, keeping the temperature for 1000min, discharging, upsetting forging, controlling the deformation at 40%, and cooling in air after forging; heating to 1080 ℃ above the transformation point, performing 2 nd heating upsetting-drawing forging, keeping the temperature for 1000min, discharging, upsetting-drawing forging, controlling the deformation at 40%, and cooling in air after forging; heating to T below the transformation point_βCarrying out 3 rd-time forging at the temperature of minus 30 ℃, controlling the deformation to be 25%, and cooling in air after forging; heating to T below the transformation point_βForging for the 4 th time at the temperature of minus 40 ℃, controlling the deformation at 20 percent, and cooling in air after forging; heating to T below the transformation point_βForging at the temperature of minus 50 ℃ for the 5 th time, controlling the deformation to be 15%, and cooling in air after forging; heating to T below the transformation point_βAnd (3) carrying out 6 th-time forging at the temperature of minus 80 ℃, controlling the deformation to be 10 percent, and carrying out air cooling after forging to obtain the bar with uniform structure.

As shown in FIG. 1, 5 points of the longitudinal head, upper, middle, lower and tail of a TC4 titanium alloy 1 ton grade industrial ingot with a fine grain structure of phi 920mm prepared in the example were sampled, and the chemical composition test thereof is listed in Table 2. A bar with the diameter of 300mm is finally prepared through ingot cogging and forging, fig. 8 is a macroscopic structure photograph of the bar obtained in the example 2 of the invention, fig. 9 is a macroscopic structure photograph of the bar obtained in the example 2 of the invention, and fig. 10 is a microscopic structure photograph of the bar obtained in the example 2 of the invention, which is subjected to beta grain size inspection.

TABLE 2 chemical composition List of longitudinal 5-point of fine-grained TC4 Ti alloy ingot with phi 920mm specification

The test results in the table 2 show that the fine-grain TC4 titanium alloy cast ingot with the phi 920mm specification produced by the preparation process provided by the invention has uniform components and is suitable for industrial production.

Example 3

1) preparing an electrode: p-containing AlV alloy and S-containing AlV alloy are used, and the addition amount of P is as follows: 0.0100%; the S content is 0.0025%. The rest components are added according to the proportion of TC4 titanium alloy;

2) welding the consumable electrode: clamping the electrode block obtained in the step 1) by using a clamp, and welding the electrode block into a consumable electrode by using a non-tungsten argon protection plasma box;

smelting for the first time: placing the consumable electrode obtained in the step 2) in a crucible with the specification of phi 440mmmm, wherein the vacuum degree before melting is less than or equal to 2.0Pa, the gas leakage rate is less than or equal to 1.0Pa/min, the melting voltage is 32V, the melting current is 14kA, the arc stabilizing current is 6.0A, and the cooling time is 8 h;

and (3) smelting for the second time: the specification of the crucible is phi 520mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.8Pa/min, the melting voltage is 32V, the melting current is 16kA, the arc stabilizing current is 10.0A, and the cooling time is 8 h;

smelting for the third time: the specification of the crucible is phi 640mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.5Pa/min, the melting voltage is 36V, the melting current is 20kA, the arc stabilizing current is alternating current at 14.0A, and the cooling time is 10h, so that the fine grain structure TC4 titanium alloy ingot with the specification of phi 640mm is obtained;

4) heating the cast ingot with the specification of phi 640mm to 1200 ℃ above the phase transformation point, carrying out 1 st fire upsetting forging, keeping the temperature for 1000min, then discharging, upsetting forging, controlling the deformation at 25%, and cooling in air after forging; heating to 1080 ℃ above the transformation point, performing 2 nd heating upsetting-drawing forging, keeping the temperature for 1000min, discharging, upsetting-drawing forging, controlling the deformation at 25%, and cooling in air after forging; heating to T below the transformation point_βCarrying out 3 rd-time forging at the temperature of minus 30 ℃, controlling the deformation to be 20%, and cooling in air after forging; heating to T below the transformation point_βForging for the 4 th time at the temperature of minus 40 ℃, controlling the deformation to be 15 percent, and cooling in air after forging; heating to T below the transformation point_βAnd (3) carrying out 5 th fire forging at the temperature of minus 50 ℃, controlling the deformation to be 10%, and carrying out air cooling after forging to obtain the bar with uniform structure.

The longitudinal head, upper, middle, lower and tail 5 points of the fine grain structure TC4 titanium alloy 3 ton grade industrial ingot with the specification of phi 640mm prepared in the embodiment were sampled and the chemical composition detection is listed in Table 3. And finally preparing the bar with the diameter of 300mm through ingot casting, cogging and forging.

TABLE 3 TABLE 640mm Specification Fine-grained TC4 titanium alloy ingot longitudinal 5-point chemical composition List

Chemical elements wt%	Al	V	O	P	S	Ti
							Head with a rotatable shaft	6.01	4.08	0.17	0.0109	0.0025	Bal.
On the upper part	6.06	4.08	0.17	0.0108	0.0026	Bal.
							In	6.03	4.04	0.17	0.0106	0.0025	Bal.
Lower part	5.98	4.08	0.16	0.0108	0.0026	Bal.
							Tail	6.01	4.09	0.17	0.0107	0.0026	Bal.

The test results in the table 3 show that the fine grain TC4 titanium alloy cast ingot with the phi 640mm specification produced by the preparation process provided by the invention has uniform components and is suitable for industrial production.

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

Claims

1. A fine-grain structure TC4 titanium alloy bar is characterized in that a P element and an S element are added into a TC4 titanium alloy, and the mass ratio of the P element to the S element is controlled to be (1-40): (1-10).

2. The fine crystalline structure TC4 titanium alloy bar according to claim 1, wherein the content of the added P element is 0.0005% to 0.02%, and the content of the added S element is 0.0005% to 0.005%.

3. The fine crystalline TC4 titanium alloy bar of claim 1, wherein the P element is added as a P-containing AlV alloy and the S element is added as an S-containing AlV alloy.

4. The preparation method of the fine-grain TC4 titanium alloy bar based on any one of claims 1-3, characterized by comprising the following steps:

5. The method of producing the fine crystalline TC4 titanium alloy bar according to claim 4, wherein the average beta grain size of the TC4 titanium alloy bar with the added P and S elements is improved by 4-5 grade and reduced by 50-80% compared with the average beta grain size of the TC4 titanium alloy bar without the added P and S elements under the same forging deformation.

6. The method of producing a fine crystalline TC4 titanium alloy bar according to claim 4, wherein the average beta grain size is reduced by 25% -50% when compared with TC4 without P and S elements, if the bar is made of TC4 with P and S elements added thereto.

7. The method for preparing the fine crystalline TC4 titanium alloy bar as claimed in claim 4, wherein the electrode block in step 1) is pressed into an electrode by using a large hydraulic press.

8. The method for preparing the fine crystalline TC4 titanium alloy bar according to claim 4, wherein the welding current of the electrode block in the step 2) is 180-400A, and the welding voltage is 25-45V.

9. The method for preparing the fine crystalline structure TC4 titanium alloy bar according to claim 4, wherein the specific parameters of the three times of vacuum melting in the step 3) are as follows:

10. The method for preparing the fine crystalline TC4 titanium alloy bar according to claim 4, wherein the beta grain size of the TC4 titanium alloy bar forged in the step 4) is not more than 1 mm.