1300MPa-grade high-strength titanium alloy forge piece as well as preparation process and application thereof

Abstract

The invention belongs to the technical field of titanium alloy material processing, and particularly discloses a 1300MPa-grade high-strength titanium alloy forge piece and a preparation process and application thereof, and the preparation process comprises the following steps: 1) preparing a near-beta-type high-strength titanium alloy bar; (2) blanking is conducted according to the specification of a to-be-prepared forge piece, and a blank is sequentially preheated, coated with a lubricant and heated; (3) the heated blank is placed in a die to be subjected to die forging; and (4) the forge piece obtained through die forging is subjected to solid solution and aging treatment, finally, the surface is cleaned, and the target forge piece is obtained. According to the preparation process provided by the invention, through precise control and optimization of each link and precise regulation and control of parameters such as temperature and time in the process from raw material selection to machining, the comprehensive mechanical properties such as strength, toughness and plasticity of the forge piece are effectively improved, and the stability and consistency of product quality are ensured; the forge piece obtained through the process can completely replace a traditional steel forge piece, and the effects of reducing the weight of an engine and improving the thrust-weight ratio are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy material processing, and in particular relates to a 1300MPa-grade high-strength titanium alloy forging, a preparation process and an application thereof. Background Art

[0002] In the field of modern aerospace, with the continuous improvement of aircraft performance requirements, more stringent standards have been put forward for the performance of structural materials. Titanium and titanium alloys, with their outstanding advantages such as high specific strength and good corrosion resistance, occupy an important position in the field of load-bearing structural materials and have become one of the first choices for structural materials of many high-speed aircraft (including aircraft, rockets, etc.). For example, the proportion of titanium used in fighter jets has shown a clear upward trend, which has jumped from the initial 1% to 41% today, which fully reflects the key role of titanium alloys in the field of aerospace and its broad application prospects.

[0003] Among them, in the design and manufacture of rocket engines, reducing the structural mass to improve the engine thrust-to-weight ratio is of vital significance for enhancing the carrying capacity of rockets, which has become one of the key technical goals in the industry. At present, large and medium-sized rocket engines have partially adopted titanium alloy parts in components such as turbo pumps, valves, and ducts, but mainly medium-strength TC4 titanium alloys. However, when it comes to key components of engines such as nozzles that have strict requirements on material properties, since these components need to withstand high-intensity mechanical loads at room temperature and high temperature environments, existing medium-strength titanium alloys are difficult to meet their strict requirements for strength, so they still have to rely on traditional steel forgings for production and manufacturing. However, the inherent disadvantage of steel forgings is that the density is relatively high, which makes the overall weight of the engine high, seriously restricting the further optimization and improvement of the thrust-to-weight ratio, and unable to meet the urgent demand for high-performance and lightweight engines in the rapid development of modern aerospace technology. In this context, it is urgent to develop a high-strength titanium alloy forging with high strength performance and good comprehensive mechanical properties.

[0004] In view of this, this invention is proposed. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a 1300MPa grade high-strength titanium alloy forging and a preparation process and application thereof, which are mainly used to solve the material performance bottleneck problem currently faced in the manufacture of key components of aerospace engines (such as nozzles, etc.).

[0006] The purpose of the present invention is to be solved by the following technical solutions:

[0007] In a first aspect, the present invention provides a process for preparing a 1300 MPa grade high-strength titanium alloy forging, comprising the following steps:

[0008] Step 1: The titanium alloy ingot melted in a vacuum consumable arc furnace is first forged above the phase change point, then free forged in the two-phase region, and finally fine forged in the two-phase region into a bar with a diameter of Φ80 to Φ130 mm;

[0009] Step 2: dividing the bar obtained in step 1 into blanks according to the specifications of the forging to be prepared, then preheating the blanks, evenly applying protective lubricant on the surface of the preheated blanks, and then heating and keeping the blanks warm;

[0010] Step 3, placing the blank heated and kept warm in step 2 into a die designed and processed according to the forging to be prepared, and forging to produce a titanium alloy forging;

[0011] Step 4: subjecting the titanium alloy forging obtained in step 3 to solid solution and aging treatment, and cleaning the surface after the treatment, to obtain a 1300 MPa grade high-strength titanium alloy forging.

[0012] Furthermore, in step one, the titanium alloy ingot is a near-β-type titanium alloy, and its chemical composition by mass percentage is: Mo: 14% to 16%; Al: 2.5% to 3.5%; Nb: 2.4% to 3.2%; Si: 0.15% to 0.25%, and the rest is Ti and unavoidable impurity elements.

[0013] Furthermore, in step one, the (α+β) / β transformation temperature of the bar is tested by metallographic method, and ultrasonic flaw detection is performed on the bar.

[0014] Furthermore, in step 2, when preheating the blank, it is preheated at a temperature of 300° C. to 400° C. for 30 min to 60 min.

[0015] Furthermore, in step 2, when the blank is heated and kept warm, it is heated within a range of 50°C to 100°C above the phase change point, and the holding time is calculated based on the blank diameter*(0.6min / mm to 0.8min / mm).

[0016] Furthermore, in step three, the material of the mold is 5CrNiMo or H13.

[0017] Furthermore, in step 4, when the titanium alloy forging is subjected to solution treatment, the titanium alloy forging is heated to 50° C. to 20° C. below the phase transition point, kept warm for 60 min to 120 min, and water-cooled to room temperature.

[0018] Furthermore, in step 4, when the titanium alloy forging is subjected to aging treatment, the titanium alloy forging is heated to 480° C. to 550° C., kept warm for 360 min to 600 min, and air-cooled to room temperature.

[0019] In a second aspect, the present invention provides a 1300MPa grade high-strength titanium alloy forging, which is prepared based on the above-mentioned preparation process. The titanium alloy forging has a tensile strength ≥1300MPa, a yield strength ≥1200MPa, and an elongation ≥8%, while the cross-sectional shrinkage rate is ≥30%.

[0020] In the third aspect, the present invention also provides a titanium alloy forging prepared by the above-mentioned preparation process, or the application of the above-mentioned titanium alloy forging in the field of aerospace engines, which is mainly used for preparing the nozzle and other parts of the engine to achieve weight reduction and improve the thrust-to-weight ratio of the engine.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The preparation process provided by the present invention selects a nearly β-type titanium alloy ingot as a raw material, and adopts a die forging process, so as to realize the direct and efficient forming of various complex and special-shaped target forgings. On this basis, the microstructure and performance of the forgings are precisely regulated through a carefully designed solid solution and aging strengthening heat treatment process. After actual testing and verification, the strength of the titanium alloy forgings finally prepared reaches a high standard of 1300MPa and above, and it also has good elongation and cross-sectional shrinkage, achieving a perfect balance between high strength and good comprehensive performance, overcoming the problems of insufficient strength of existing medium-strong titanium alloys and poor comprehensive performance of traditional steel forgings, greatly improving the reliability and service life of key components of aerospace engines (such as nozzles, etc.), and effectively reducing the risk of component failure. In addition, from the perspective of weight reduction and thrust-to-weight ratio improvement, the use of titanium alloys to replace steel forgings significantly reduces the weight of the engine structure, strongly promotes the improvement of the engine thrust-to-weight ratio, enhances the rocket carrying capacity, and meets the urgent needs of modern aerospace for high-performance and lightweight engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the present invention.

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a flow chart of the process for preparing 1300MPa grade high-strength titanium alloy forgings of the present invention;

[0026] Figure 2 is a schematic structural diagram of the target titanium alloy nozzle of Example 1 of the present invention;

[0027] Figure 3 It is a schematic diagram of the structure of the titanium alloy nozzle forging prepared in Example 1 of the present invention.

[0028] Figure 4 Schematic diagram of the die structure used in preparing the titanium alloy nozzle forging in Example 1 of the present invention;

[0029] Figure 5 Schematic diagram of the blank structure used in preparing the titanium alloy nozzle forging in Example 1 of the present invention;

[0030] Among them: 1 is the upper die; 2 is the lower die. DETAILED DESCRIPTION

[0031] Here, exemplary embodiments will be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are only examples consistent with some aspects of the present invention as detailed in the appended claims.

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0033] like Figure 1 As shown, the present invention provides a preparation process for a 1300MPa grade high-strength titanium alloy forging, which specifically includes the following steps:

[0034] Step 1: The titanium alloy ingot obtained by smelting in a vacuum consumable arc furnace is first subjected to a blanking forging process above the phase transformation point, followed by a free forging operation in the two-phase region, and finally finely forged into a bar with a diameter ranging from Φ80 to Φ130 mm in the two-phase region. In this process, the metallographic method is used to accurately determine the (α+β) / β transformation temperature, and the ultrasonic flaw detection technology is used to conduct a comprehensive inspection of the bar to ensure that its internal quality meets the A-level requirements in GB / T5193-2007.

[0035] Step 2: Cut the bar in step 1 into corresponding billets according to the actual specifications of the forging to be prepared; then preheat the billet in a temperature range of 300°C to 400°C for 30min to 60min; then evenly apply protective lubricant on the surface of the preheated billet, and then heat the billet in the range of 50°C to 100°C above the phase change point. The holding time is accurately calculated according to the ratio of 0.6min / mm to 0.8min / mm based on the billet diameter.

[0036] Step 3: Place the heated and heat-insulated blank in step 2 into a die specially designed and processed according to the forging to be prepared for forging, and the die material is selected to be 5CrNiMo or H13, so as to produce a titanium alloy forging.

[0037] Step 4: Perform solid solution and aging treatment on the titanium alloy forgings obtained in step 3. During the solid solution treatment, the titanium alloy forgings are heated to 50℃~20℃ below the phase transition point, kept warm for 60min~120min, and then quickly cooled to room temperature with water; during the aging treatment, the titanium alloy forgings are heated to 480℃~550℃, kept warm for 360min~600min, and then air cooled to room temperature. After the treatment, the surface of the forgings is cleaned, and finally a 1300MPa grade high-strength titanium alloy forging is obtained.

[0038] Among them, in step one, the titanium alloy ingot is a near-β-type titanium alloy, and its chemical composition mass percentage is: Mo: 14% to 16%; Al: 2.5% to 3.5%; Nb: 2.4% to 3.2%; Si: 0.15% to 0.25%, and the rest is Ti and unavoidable impurity elements.

[0039] In order to further verify the efficacy of the preparation process of the present invention, the inventors conducted the following specific experiments:

[0040] Example 1

[0041] The embodiment of the present invention provides a preparation process of a 1300MPa grade high-strength titanium alloy forging, which is used to prepare a model A engine nozzle forging, and specifically comprises the following steps:

[0042] 1) Preparation of near-β high-strength titanium alloy bars: Sponge titanium and master alloys are used as raw materials, and titanium alloy ingots are prepared after electrode pressing, electrode welding and vacuum consumable arc melting. The ingots are forged above the phase change point, free forged in the two-phase zone, and finally fine forged in the two-phase zone into bars with a diameter of Φ80 mm. The surface of the bars is descaled by a lathe;

[0043] 2) Phase transition point test: The (α+β) / β transition temperature of the bar obtained in step 1) is 830°C by metallographic test;

[0044] 3) Ultrasonic flaw detection of blanks: ultrasonic flaw detection is performed on the bar obtained in step 1), which meets the requirements of Class A in GB / T5193-2007;

[0045] 4) Forging design: according to Figure 2 The target titanium alloy nozzle has the following specifications and is designed as shown in Figure 3 The titanium alloy nozzle forging shown;

[0046] 5) Mold design and processing: According to the design drawings of titanium alloy nozzle forgings and equipment interfaces in step 4, design the Figure 4 The mold drawing shown in the figure is used to process the mold using mold steel 5CrNiMo material;

[0047] 6) Blank cutting and processing: According to the forging design requirements, the bar obtained in step 1) is divided into Figure 5 The blank shown in the figure is polished on both ends of the blank and chamfered on both ends;

[0048] 7) Preheating, coating of protective lubricant and heating of the billet: The billet is preheated at 400°C for 30 minutes, then the protective lubricant is evenly coated on the surface, and then the billet is heated at 50°C above the phase change point (i.e. 880°C). The holding time is calculated according to the billet diameter*(0.8min / mm), i.e. the billet holding time is 64min;

[0049] 8) Die forging: The blank heated and kept warm in step 7) is placed in the die designed and processed in step 5) for die forging to form a shape such as Figure 3 The titanium alloy nozzle forging shown;

[0050] 9) Solution treatment and aging treatment of forgings: The titanium alloy nozzle forging obtained in step 8) is heated to 35°C below the phase transition point (i.e., 795°C), kept at this temperature for 80 minutes, and water-cooled to room temperature, thereby completing the solution treatment; then, the titanium alloy nozzle forging after the solution treatment is heated to 510°C, kept at this temperature for 480 minutes, and air-cooled to room temperature, thereby completing the failure treatment;

[0051] 10) Forging surface cleaning: The surface oxide scale of the titanium alloy nozzle forging after the solution treatment and aging treatment in step 9) is cleaned by shot peening, so as to prepare the A-type engine nozzle forging.

[0052] In order to further illustrate the effect of the preparation process of the present invention, the inventors conducted relevant mechanical property tests on both ends of the forging prepared in Example 1. The test results are shown in Table 1 below:

[0053] Table 1 Mechanical properties test results of the two ends of the forgings prepared in Example 1

[0054]

[0055] Example 2

[0056] The embodiment of the present invention provides a preparation process of a 1300MPa grade high-strength titanium alloy forging, which is used to prepare a B-type engine nozzle forging, and specifically includes the following steps:

[0057] 1) Preparation of near-β high-strength titanium alloy bars: Sponge titanium and master alloys are used as raw materials, and titanium alloy ingots are prepared after electrode pressing, electrode welding and vacuum consumable arc melting. The ingots are forged above the phase change point, free forged in the two-phase zone, and finally fine forged in the two-phase zone into bars with a diameter of Φ130 mm. The surface of the bars is descaled by a lathe;

[0058] 2) Phase transition point test: The (α+β) / β transition temperature of the bar obtained in step 1) is 830°C by metallographic test;

[0059] 3) Ultrasonic flaw detection of blanks: ultrasonic flaw detection is performed on the bar obtained in step 1), which meets the requirements of Class A in GB / T5193-2007;

[0060] 4) Forging design: Design the titanium alloy nozzle forging drawings according to the specifications of the target titanium alloy nozzle;

[0061] 5) Mold design and processing: According to the design drawings of the titanium alloy nozzle forgings and the equipment interface in step 4), design the mold drawings and use mold steel H13 material to process the mold;

[0062] 6) Blank cutting and processing: according to the forging design requirements, the bar obtained in step 1) is divided into blanks, and both ends of the blanks are polished and chamfered;

[0063] 7) Preheating, coating of protective lubricant and heating of the billet: The billet is preheated at 300°C for 60 minutes, then the protective lubricant is evenly coated on the surface, and then the billet is heated at 100°C above the phase change point (i.e. 930°C). The holding time is calculated according to the billet diameter*(0.6min / mm), i.e. the billet holding time is 78 minutes;

[0064] 8) Die forging: placing the blank heated and kept in step 7) in the die designed and processed in step 5) for die forging to produce a titanium alloy nozzle forging;

[0065] 9) Solution treatment and aging treatment of forgings: The titanium alloy nozzle forging obtained in step 8) is heated to 50°C below the phase transition point (i.e., 780°C), kept at this temperature for 120 minutes, and water-cooled to room temperature, thereby completing the solution treatment; then, the titanium alloy nozzle forging after the solution treatment is heated to 480°C, kept at this temperature for 600 minutes, and air-cooled to room temperature, thereby completing the failure treatment;

[0066] 10) Forging surface cleaning: The surface oxide scale of the titanium alloy nozzle forging after the solution treatment and aging treatment in step 9) is cleaned by shot peening, so as to prepare a B-type engine nozzle forging.

[0067] In order to further illustrate the effect of the preparation process of the present invention, the inventors conducted relevant mechanical property tests on both ends of the forging prepared in Example 2. The test results are shown in Table 2 below:

[0068] Table 2 Mechanical properties test results of the forging ends prepared in Example 2

[0069]

[0070] Example 3

[0071] The embodiment of the present invention provides a preparation process of a 1300MPa grade high-strength titanium alloy forging, which is used to prepare a C-type engine nozzle forging, and specifically includes the following steps:

[0072] 1) Preparation of near-β high-strength titanium alloy bars: Sponge titanium and master alloys are used as raw materials, and titanium alloy ingots are prepared after electrode pressing, electrode welding and vacuum consumable arc melting. The ingots are forged above the phase change point, free forged in the two-phase zone, and finally fine forged in the two-phase zone into bars with a diameter of Φ130 mm. The surface of the bars is descaled by a lathe;

[0073] 2) Phase transition point test: The (α+β) / β transition temperature of the bar obtained in step 1) is 830°C by metallographic test;

[0074] 3) Ultrasonic flaw detection of blanks: ultrasonic flaw detection is performed on the bar obtained in step 1), which meets the requirements of Class A in GB / T5193-2007;

[0075] 4) Forging design: Design the titanium alloy nozzle forging drawings according to the specifications of the target titanium alloy nozzle;

[0076] 5) Mold design and processing: According to the design drawings of the titanium alloy nozzle forgings and the equipment interface in step 4), the mold drawings are designed, and the mold is processed using mold steel 5CrNiMo material;

[0077] 6) Blank cutting and processing: according to the forging design requirements, the bar obtained in step 1) is divided into blanks, and both ends of the blanks are polished and chamfered;

[0078] 7) Preheating, coating of protective lubricant and heating of the billet: preheat the billet at 350°C for 45 minutes, then evenly coat the surface with protective lubricant, and then heat the billet at 80°C (i.e. 910°C) above the phase change point. The holding time is calculated by the billet diameter*(0.7min / mm), i.e. the billet holding time is 70 minutes;

[0079] 8) Die forging: placing the blank heated and kept in step 7) in the die designed and processed in step 5) for die forging to produce a titanium alloy nozzle forging;

[0080] 9) Solution treatment and aging treatment of forgings: The titanium alloy nozzle forging obtained in step 8) is heated to 20°C below the phase transition point (i.e., 810°C), kept at this temperature for 60 minutes, and water-cooled to room temperature, thereby completing the solution treatment; then, the titanium alloy nozzle forging after the solution treatment is heated to 550°C, kept at this temperature for 360 minutes, and air-cooled to room temperature, thereby completing the failure treatment;

[0081] 10) Forging surface cleaning: The surface oxide scale of the titanium alloy nozzle forging after the solution treatment and aging treatment in step 9) is cleaned by shot peening, so as to prepare a C-type engine nozzle forging.

[0082] In order to further illustrate the effect of the preparation process of the present invention, the inventors conducted relevant mechanical property tests on both ends of the forging prepared in Example 3. The test results are shown in Table 3 below:

[0083] Table 3 Mechanical properties test results of the forging ends prepared in Example 3

[0084]

[0085] In summary, the 1300MPa grade high-strength titanium alloy forging preparation process proposed in the present invention successfully prepares titanium alloy forgings that meet high strength requirements by rationally selecting titanium alloy ingots, combining strict billet processing, mold design and processing, and precise solid solution and aging treatment parameters. In addition, Examples 1 to 3 were prepared and performance tested for A, B, and C model engine nozzle forgings, respectively. From the test results, it can be seen that the prepared forgings have excellent mechanical properties such as tensile strength, yield strength, elongation, and cross-sectional shrinkage, and the performance data at both ends of different embodiments are relatively stable, which proves the reliability and repeatability of the preparation process, and can completely replace steel forgings to produce engines, thereby achieving the purpose of reducing weight and improving the engine thrust-to-weight ratio.

[0086] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0087] It should 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 its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A process for preparing a 1300MPa grade high-strength titanium alloy forging, characterized in that: The following steps are involved: Step 1: The titanium alloy ingot melted in a vacuum consumable arc furnace is first forged above the phase change point, then free forged in the two-phase region, and finally fine forged in the two-phase region into a bar with a diameter of Φ80 to Φ130 mm; Step 2: dividing the bar obtained in step 1 into blanks according to the specifications of the forging to be prepared, then preheating the blanks, evenly applying protective lubricant on the surface of the preheated blanks, and then heating and keeping the blanks warm; Step 3, placing the blank heated and kept warm in step 2 into a die designed and processed according to the forging to be prepared, and forging to produce a titanium alloy forging; Step 4: subjecting the titanium alloy forging obtained in step 3 to solid solution and aging treatment, and cleaning the surface after the treatment, to obtain a 1300 MPa grade high-strength titanium alloy forging.

2. The process for preparing a 1300MPa high-strength titanium alloy forging according to claim 1, characterized in that: In step 1, the titanium alloy ingot is a near-β-type titanium alloy, and its chemical composition by mass percentage is: Mo: 14% to 16%; Al: 2.5% to 3.5%; Nb: 2.4% to 3.2%; Si: 0.15% to 0.25%, and the rest is Ti and unavoidable impurity elements.

3. The process for preparing a 1300MPa high-strength titanium alloy forging according to claim 1, characterized in that: In step 1, the (α+β) / β transformation temperature of the bar is tested by metallographic method, and the bar is subjected to ultrasonic flaw detection.

4. The process for preparing a 1300MPa high-strength titanium alloy forging according to claim 1, characterized in that: In step 2, the blank is preheated at 300° C. to 400° C. for 30 min to 60 min.

5. The process for preparing a 1300MPa high-strength titanium alloy forging according to claim 1, characterized in that: In step 2, when the blank is heated and kept warm, it is heated within a range of 50°C to 100°C above the phase change point, and the holding time is calculated based on the blank diameter*(0.6min / mm to 0.8min / mm).

6. The process for preparing a 1300MPa high-strength titanium alloy forging according to claim 1, characterized in that: In step three, the material of the mold is 5CrNiMo or H13.

7. The process for preparing a 1300MPa high-strength titanium alloy forging according to claim 1, characterized in that: In step 4, when the titanium alloy forging is subjected to solution treatment, the titanium alloy forging is heated to 50° C. to 20° C. below the phase transition point, kept warm for 60 min to 120 min, and water-cooled to room temperature.

8. The process for preparing a 1300MPa high-strength titanium alloy forging according to claim 1, characterized in that: In step 4, when the titanium alloy forging is subjected to aging treatment, the titanium alloy forging is heated to 480° C. to 550° C., kept at this temperature for 360 min to 600 min, and air-cooled to room temperature.

9. A 1300MPa grade high-strength titanium alloy forging, characterized in that: The titanium alloy forging is prepared based on the preparation process described in any one of claims 1 to 8, and the titanium alloy forging has a tensile strength of ≥1300MPa, a yield strength of ≥1200MPa, an elongation of ≥8%, and a cross-sectional shrinkage of ≥30%.

10. A titanium alloy forging prepared by the preparation process according to any one of claims 1 to 8, or use of the titanium alloy forging according to claim 9 in the field of aerospace engines.

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