High-strength Ti-6Al-4V titanium alloy and preparation method thereof

Abstract

The invention provides a high-strength Ti-6Al-4V titanium alloy. The high-strength Ti-6Al-4V titanium alloy comprises the following components in percentage by weight: 5.5%-7.06.75% of Al, 3.5%-4.5% of V, 0.15%-0.30% of Fe, 0.05%-0.15% of O, 0.02%-0.10% of C, 0.02%-0.10% of N and the balance of Ti. The invention further provides a preparation method of the high-strength Ti-6Al-4V titanium alloy. Compared with conventional Ti-6Al-4V, the high-strength Ti-6Al-4V disclosed by the invention has the advantages that the room-temperature mechanical property is obviously higher than that of common Ti-6Al-4V titanium alloy, the requirements on the fields of high-strength Ti-6Al-4V titanium processing materials, 3D printing and the like in China can be met, and the high-strength Ti-6Al-4V titanium alloy ingot casting is suitable for production of high-quality and high-strength Ti-6Al-4V titanium alloy ingot casting.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal processing, and specifically relates to a high-strength Ti-6Al-4V titanium alloy and a preparation method thereof. Background Art

[0002] Titanium and titanium alloys are indispensable key materials for important sectors such as aviation, aerospace, ships, petroleum, chemical industry, metallurgy, and electricity. They are also widely used in high-tech fields such as memory, superconductivity, and high-energy hydrogen storage. They are of great strategic significance to national defense, national economic construction, and social development.

[0003] Ti-6Al-4V alloy is an α+β two-phase alloy developed by the Illinois Institute of Technology in the United States in the early 1950s. It has a series of advantages such as low density, high specific strength, high temperature resistance, corrosion resistance, etc. It is widely used in various fields such as aerospace, petrochemical, shipbuilding and weapons industry. It is precisely because of the good comprehensive properties of Ti-6Al-4V alloy that it has become the most deeply studied and tested titanium alloy.

[0004] In recent years, with the rapid development of the domestic titanium processing industry and the 3D printing industry, especially the large and complex titanium alloy structural parts manufactured by metal 3D printing technology have completed engineering verification in the aviation field, making the application advantages of metal 3D printing technology more obvious. With the increasing maturity of 3D printing technology, the titanium market has an increasing demand for powder materials, and the use conditions of parts are becoming increasingly harsh. In order to meet the current market requirements for high-strength Ti-6Al-4V titanium alloy materials for 3D printing, this paper develops a new type of high-nitrogen content Ti-6Al-4V titanium alloy to meet the market demand for Ti-6Al-4V titanium alloy materials with better performance for 3D printing.

[0005] Therefore, it is necessary to provide a high-strength Ti-6Al-4V titanium alloy and a preparation method thereof to solve the above technical problems. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a high-strength Ti-6Al-4V titanium alloy and a preparation method thereof.

[0007] To solve the above technical problems, the present invention provides a high-strength Ti-6Al-4V titanium alloy, in which the amount of each raw material is calculated according to the mass percentage of each element, including: Al: 5.5%-7.06.75%, V: 3.5%~4.5%, Fe: 0.15%~0.30%, O: 0.05%~0.15%, C: 0.02%~0.10%, N: 0.02%~0.10%, and the rest is Ti.

[0008] Preferably, the amount of each raw material added is calculated based on the mass percentage of each element, including: Al: 6.5%, V: 4.2%, Fe: 0.20%, O: 0.08%, C: 0.06%, N: 0.04%, and the rest is Ti.

[0009] The present invention also provides a method for preparing a high-strength Ti-6Al-4V titanium alloy, comprising the following steps: S1, provide sponge titanium, Al-V master alloy, Al bean, Fe nail, carbon black, TiO2 and Fe-VN or VN master alloy as raw materials; mix them evenly and press them into electrode blocks with a hydraulic press, wherein the addition ratio of N master alloy is 0.05%~1.0%; in order to ensure the formability of the pressed electrode block, when the density of the electrode block is less than 3.0g / cm 3 When the electrode block is welded, the corners of the electrode block may fall off and the formability is poor, which will affect the welding of the electrode block in the next step. Therefore, the density of the electrode block must be ≥3.0g / cm 3 ; The addition ratio of titanium sponge is 89%~91%, the addition ratio of Al-V master alloy is 6%~7%, the addition ratio of Al bean is 3%~4%, the addition ratio of Fe nail is 0.01%~0.09%, the addition ratio of carbon black is 0.01%~0.2%, the addition ratio of TiO2 is 0.01%~0.24%, and the addition ratio of Fe-VN or VN master alloy is 0.05%~1.0%; S2, under argon protection, using plasma arc welding to weld the plurality of electrode blocks described in step S1 together to obtain a primary consumable electrode; S3, using a vacuum consumable arc furnace to perform multiple vacuum melting on the primary consumable electrode described in step S2, with the melting vacuum ≤10Pa, the leakage rate ≤1.0Pa / min, the melting current 8~40kA, and the melting voltage 20~45V to obtain a high-strength Ti-6Al-4V titanium alloy.

[0010] Preferably, in order to ensure the formability of the pressed electrode block, when the density of the electrode block is less than 3.0g / cm3, the electrode block will have corner chipping and poor formability, which will affect the next step of welding the electrode block. Therefore, the density of the electrode block must be ≥3.0g / cm3.

[0011] Preferably, the N content in the Fe-VN master alloy is 9% to 15%, and the N content in the VN master alloy is 10% to 18%.

[0012] Preferably, the master alloy Fe—VN or VN is in granular form with a particle size of ≤10 mm.

[0013] Preferably, the mass percentages of the initial alloy ratios of the electrode block pressed in step S1 are: the mass percentages of the initial alloy ratios of the electrode block pressed in step S1 are: Al: 5.5%-7.06.75%, V: 3.5%~4.5%, Fe: 0.15%~0.30%, O: 0.05%~0.15%, C: 0.02%~0.10%, N: 0.02%~0.10%, and the rest is Ti.

[0014] Preferably, the density of the electrode block pressed in step S1 is ≥3.0 g / cm 3 .

[0015] Preferably, the welding current in step S2 is ≥250A, and the welding voltage is ≥30V.

[0016] Preferably, the multiple vacuum consumable arc melting in step S3 is performed twice or three times, specifically: After two vacuum consumable arc melting: Primary smelting: crucible specifications are Φ440~Φ960mm, gas leakage rate ≤1.0Pa / min, smelting vacuum ≤10Pa, smelting current 8~30kA, smelting voltage 30~40V; Secondary finished product smelting: crucible specifications are Φ500~Φ1040mm, gas leakage rate ≤0.7Pa / min, smelting vacuum ≤5Pa, smelting current 15~40kA, smelting voltage 20~40V; After three times of vacuum consumable arc melting: Primary smelting: crucible specifications are Φ440~Φ820mm, gas leakage rate ≤1.0Pa / min, smelting vacuum ≤10Pa, smelting current 8~25kA, smelting voltage 20~40V; Secondary smelting: crucible specifications are Φ500~Φ960mm, gas leakage rate ≤0.7Pa / min, smelting vacuum ≤5Pa, smelting current 15~35kA, smelting voltage 20~40V; Three finished product melting: crucible specifications are Φ600~Φ1040mm, leakage rate ≤0.7Pa / min, melting vacuum ≤5Pa, melting current 20~40kA, melting voltage 20~45V.

[0017] Compared with the related art, the high-strength Ti-6Al-4V titanium alloy and the preparation method thereof provided by the present invention have the following beneficial effects: 1. The addition of nitrogen-containing multi-element master alloy ensures the uniformity of alloy composition and its metallurgical quality; 2. Compared with conventional Ti-6Al-4V, the room temperature mechanical properties of the high-strength Ti-6Al-4V in this application are significantly higher than those of ordinary Ti-6Al-4V titanium alloy, which can meet the domestic demand for high-strength Ti-6Al-4V titanium processing materials and 3D printing and other fields, and is suitable for the production of high-quality and high-strength Ti-6Al-4V titanium alloy ingots. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of sampling at five points in the longitudinal direction of the ingot obtained by the present invention; Figure 2 A schematic diagram of sampling 9 points on the cut surface of the ingot riser obtained by the present invention; Figure 3 This is a schematic diagram of the composition analysis results of the ingot at five points in the longitudinal direction of Example 1; Figure 4 This is a schematic diagram of the composition analysis results of 9 points on the cut surface of the ingot riser of Example 1; Figure 5 This is a schematic diagram of the composition analysis results of the ingot at five points in the longitudinal direction of Example 2; Figure 6 This is a schematic diagram of the composition analysis results of 9 points on the cut surface of the ingot riser of Example 2; Figure 7 This is a schematic diagram of the composition analysis results of the ingot at five points in the longitudinal direction of Example 3; Figure 8 This is a schematic diagram of the composition analysis results of 9 points on the cut surface of the ingot riser in Example 3. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0020] Example 1

[0021] Step S1, using titanium sponge, VN, Al-V master alloy, Al bean, Fe nail, carbon black and TiO2 as raw materials, the amount of each raw material is calculated by the mass percentage of each element, wherein: Al: 6.5%, V: 4.2%, Fe: 0.20%, O: 0.08%, C: 0.06%, N: 0.04%, the rest is Ti. After mixing them evenly, use a hydraulic press to press them into electrode blocks, and the density of the pressed electrode blocks is ≥3.0g / cm 3 ; Step S2, under argon protection, using plasma arc welding to weld the electrode blocks in step S1 to obtain a primary consumable electrode, with a welding current of 300-350A and a welding voltage of 35-40V; Step S3, using a vacuum consumable arc furnace to perform vacuum melting twice on the primary consumable electrode obtained in step S2, specifically: Primary smelting: crucible specification is Φ440mm, gas leakage rate is 0.7Pa / min, smelting vacuum is ≤7Pa, smelting current is 10~11kA, and smelting voltage is 32~35V; Secondary finished product smelting: crucible specification is Φ550mm, gas leakage rate is 0.5Pa / min, smelting vacuum is ≤3Pa, smelting current is 18~20kA, and smelting voltage is 32~38V; A high-strength Ti-6Al-4V titanium alloy ingot is obtained.

[0022] In order to evaluate the composition uniformity of the high-strength Ti-6Al-4V titanium alloy prepared by the present invention, composition analysis was performed at 5 points in the longitudinal direction of the ingot and 9 points on the cut surface of the head riser. The sampling diagram is shown in FIG. Figure 1 and Figure 2 ; Figure 3 The composition analysis results of the ingot at 5 points in the longitudinal direction of Example 1 are as follows: Figure 4 The 9-point composition analysis result of the riser cut surface of the ingot in Example 1 can be seen from the figure that the composition uniformity in the longitudinal and radial directions of the ingot is good and meets the requirements of relevant standards. The room temperature tensile strength of the ingot is Rm=1003MPa.

[0023] Example 2

[0024] Step S1, using titanium sponge, Fe-VN, Al-V master alloy, Al bean, Fe nail, carbon black and TiO2 as raw materials, the amount of each raw material is calculated by the mass percentage of each element, among which: Al: 6.6%, V: 4.3%, Fe: 0.23%, O: 0.08%, C: 0.06%, N: 0.035%, and the rest is Ti. After mixing them evenly, use a hydraulic press to press them into electrode blocks, and the density of the pressed electrode blocks is ≥3.1g / cm 3 ; Step S2, under argon protection, using plasma arc welding to weld the electrode blocks in step S1 to obtain a primary consumable electrode, with a welding current of 300-340A and a welding voltage of 37-42V; Step S3, using a vacuum consumable arc furnace to perform vacuum melting three times on the primary consumable electrode obtained in step S2, specifically: Primary smelting: crucible specification is Φ570mm, gas leakage rate is 0.7Pa / min, smelting vacuum is ≤5Pa, smelting current is 14~16kA, and smelting voltage is 32~37V; Secondary smelting: crucible specification is Φ650mm, gas leakage rate is 0.5Pa / min, smelting vacuum is ≤3Pa, smelting current is 22~25kA, and smelting voltage is 33~40V; Three finished product smelting: crucible specification is Φ720mm, gas leakage rate is 0.5Pa / min, smelting vacuum is ≤3Pa, smelting current is 22~28kA, and smelting voltage is 33~40V; A high-strength Ti-6Al-4V titanium alloy ingot is obtained.

[0025] In order to evaluate the composition uniformity of the high-strength Ti-6Al-4V titanium alloy ingot prepared by the present invention, composition analysis was performed at 5 points in the longitudinal direction of the ingot and 9 points on the cut surface of the head riser. The sampling diagram is shown in FIG. Figure 1 and Figure 2 ; Figure 5 The composition analysis results of the ingot at 5 points in the longitudinal direction of Example 2 are as follows: Figure 6 The composition analysis results of the 9-point cut surface of the ingot riser of Example 2 are shown in the figure. It can be seen from the figure that the composition uniformity of the ingot in the longitudinal and radial directions is good and meets the requirements of relevant standards. The room temperature tensile strength of the ingot is Rm=1012MPa; Example 3

[0026] Step S1, using titanium sponge, Fe-VN, Al-V master alloy, Al bean, Fe nail, carbon black and TiO2 as raw materials, the amount of each raw material is calculated by the mass percentage of each element, wherein: Al: 6.6%, V: 4.3%, Fe: 0.23%, O: 0.08%, C: 0.06%, N: 0.035%, the rest is Ti. After mixing them evenly, use a hydraulic press to press them into electrode blocks, and the density of the pressed electrode blocks is ≥3.2g / cm 3 ; Step S2, under argon protection, using plasma arc welding to weld the electrode blocks in step S1 to obtain a primary consumable electrode, with a welding current of 300-350A and a welding voltage of 40-45V; Step S3, using a vacuum consumable arc furnace to perform vacuum melting three times on the primary consumable electrode obtained in step S2, specifically: Primary smelting: crucible specification is Φ820mm, gas leakage rate is 0.65Pa / min, smelting vacuum is ≤4Pa, smelting current is 20~23kA, and smelting voltage is 31~38V; Secondary smelting: crucible specification is Φ940mm, gas leakage rate is 0.60Pa / min, smelting vacuum is ≤3.5Pa, smelting current is 25~35kA, and smelting voltage is 31~40V; Three finished product smelting: crucible specification is Φ1040mm, gas leakage rate is 0.52Pa / min, smelting vacuum is ≤3.0Pa, smelting current is 28~38kA, and smelting voltage is 33~42V; A high-strength Ti-6Al-4V titanium alloy ingot is obtained.

[0027] In order to evaluate the composition uniformity of the high-strength Ti-6Al-4V titanium alloy ingot prepared by the present invention, composition analysis was performed at 5 points in the longitudinal direction of the ingot and 9 points on the cut surface of the head riser. The sampling diagram is shown in FIG. Figure 1 and Figure 2 ; Figure 7 The composition analysis results of the ingot at 5 points in the longitudinal direction of Example 3 are as follows: Figure 8 The composition analysis results of the 9-point cut surface of the ingot riser of Example 3 are shown in the figure. It can be seen from the figure that the composition uniformity of the ingot in the longitudinal and radial directions is good and meets the requirements of relevant standards. The room temperature tensile strength of the ingot is Rm=1006MPa; It can be seen from Examples 1 to 3 that the high-strength Ti-6Al-4V titanium alloy ingots with specifications of Φ440mm to Φ1040mm produced by the method of the present invention have good longitudinal and radial chemical composition uniformity, and the use of Fe-VN and VN intermediate alloys can meet the requirements of the ingots for high nitrogen content.

[0028] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high-strength Ti-6Al-4V titanium alloy, characterized in that: The amount of each raw material is calculated based on the mass percentage of each element, including: Al: 5.5%-7.06.75%, V: 3.5%~4.5%, Fe: 0.15%~0.30%, O: 0.05%~0.15%, C: 0.02%~0.10%, N: 0.02%~0.10%, and the rest is Ti.

2. The high-strength Ti-6Al-4V titanium alloy according to claim 1, characterized in that: The amount of each raw material added is calculated based on the mass percentage of each element, including: Al: 6.5%, V: 4.2%, Fe: 0.20%, O: 0.08%, C: 0.06%, N: 0.04%, and the rest is Ti.

3. A method for preparing a high-strength Ti-6Al-4V titanium alloy, characterized in that: The steps include: S1, providing titanium sponge, Al-V master alloy, Al bean, Fe nail, carbon black, TiO2 and Fe-VN or VN master alloy as raw materials; mixing them evenly and pressing them into electrode blocks by a hydraulic press, wherein the titanium sponge addition ratio is 89%~91%, the Al-V master alloy addition ratio is 6%~7%, the Al bean addition ratio is 3%~4%, the Fe nail addition ratio is 0.01%~0.09%, the carbon black addition ratio is 0.01%~0.2%, the TiO2 addition ratio is 0.01%~0.24%, and the addition ratio of N, Fe-VN or VN master alloy is 0.05%~1.0%; S2, under argon protection, using plasma arc welding to weld the plurality of electrode blocks described in step S1 together to obtain a primary consumable electrode; S3, using a vacuum consumable arc furnace to perform multiple vacuum melting on the primary consumable electrode described in step S2, with the melting vacuum ≤10Pa, the leakage rate ≤1.0Pa / min, the melting current 8~40kA, and the melting voltage 20~45V to obtain a high-strength Ti-6Al-4V titanium alloy.

4. The method for preparing the high-strength Ti-6Al-4V titanium alloy according to claim 3, characterized in that: In order to ensure the formability of the pressed electrode block, when the density of the electrode block is less than 3.0g / cm 3 When the electrode block is welded, the corners of the electrode block may fall off and the formability is poor, which will affect the welding of the electrode block in the next step. Therefore, the density of the electrode block must be ≥3.0g / cm 3 .

5. The method for preparing the high-strength Ti-6Al-4V titanium alloy according to claim 4, characterized in that: The N content in the Fe-VN master alloy is 9%~15%, and the N content in the VN master alloy is 10%~18%.

6. The method for preparing the high-strength Ti-6Al-4V titanium alloy according to claim 5, characterized in that: The master alloy Fe-VN or VN is in granular form with a particle size of ≤10mm.

7. The method for preparing the high-strength Ti-6Al-4V titanium alloy according to claim 3, characterized in that: The initial alloy ratio of the electrode block pressed in step S1 is as follows: Al: 5.5%-7.06.75%, V: 3.5%-4.5%, Fe: 0.15%-0.30%, O: 0.05%-0.15%, C: 0.02%-0.10%, N: 0.02%-0.10%, and the rest is Ti.

8. The method for preparing the high-strength Ti-6Al-4V titanium alloy according to claim 3, characterized in that: The pressure of the electrode block pressed in step S1 is ≥ 25 MPa, and the density of the pressed electrode block is ≥ 2.5 g / cm 3 .

9. The method for preparing the high-strength Ti-6Al-4V titanium alloy according to claim 3, characterized in that: The welding current in step S2 is ≥250A, and the welding voltage is ≥30V.

10. The method for preparing the high-strength Ti-6Al-4V titanium alloy according to claim 3, characterized in that: The multiple vacuum consumable arc melting in step S3 is two or three times, specifically: After two vacuum consumable arc melting: Primary smelting: crucible specifications are Φ440~Φ960mm, gas leakage rate ≤1.0Pa / min, smelting vacuum ≤10Pa, smelting current 8~30kA, smelting voltage 30~40V; Secondary finished product smelting: crucible specifications are Φ500~Φ1040mm, gas leakage rate ≤0.7Pa / min, smelting vacuum ≤5Pa, smelting current 15~40kA, smelting voltage 20~40V; After three times of vacuum consumable arc melting: Primary smelting: crucible specifications are Φ440~Φ820mm, gas leakage rate ≤1.0Pa / min, smelting vacuum ≤10Pa, smelting current 8~25kA, smelting voltage 20~40V; Secondary smelting: crucible specifications are Φ500~Φ960mm, gas leakage rate ≤0.7Pa / min, smelting vacuum ≤5Pa, smelting current 15~35kA, smelting voltage 20~40V; Three finished product melting: crucible specifications are Φ600~Φ1040mm, leakage rate ≤0.7Pa / min, melting vacuum ≤5Pa, melting current 20~40kA, melting voltage 20~45V.

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