TC4 titanium alloy bar for high-performance blade and preparation method of TC4 titanium alloy bar

Abstract

The invention belongs to the technical field of titanium alloy machining, and relates to a TC4 titanium alloy bar for a high-performance blade and a preparation method of the TC4 titanium alloy bar. According to the method, all raw materials are mixed and pressed into an electrode, and qualified TC4 titanium alloy cast ingots are obtained through three times of VAR smelting; then, the TC4 titanium alloy cast ingot is subjected to multi-heating-number upsetting and drawing forging above and below the phase transformation point to form an intermediate bar blank A; rolling the intermediate bar blank A for multiple heating numbers to obtain an intermediate bar blank B; and finally, surface defects and oxide skin of the middle bar billet B are removed, and the TC4 titanium alloy finished bar for the high-performance blade is obtained. According to the TC4 titanium alloy bar prepared through the preparation method, the primary alpha phase content is larger than or equal to 65%, the average grain size of the alpha phase is smaller than or equal to 15 micrometers, and the room-temperature tensile strength, the room-temperature impact energy, the 400-DEG C high-temperature tensile strength, the 400-DEG C / 350 MPa / 100 h creep plasticity elongation and the fatigue limit that the room-temperature smooth high-cycle fatigue cycle number is larger than 1.0 * 10 < 7 > can all meet relevant standard requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy processing, relates to the preparation of TC4 titanium alloy, and specifically relates to a TC4 titanium alloy rod for high-performance blades and a preparation method thereof. Background Art

[0002] TC4 titanium alloy has high specific strength, wide operating temperature range and excellent corrosion resistance, and is one of the preferred materials for manufacturing aircraft engine compressor blades. The working conditions of aircraft engine blades are extremely complex and harsh, and they need to withstand huge aerodynamic stress, centrifugal stress and temperature load. Therefore, high requirements are placed on the microstructure and mechanical properties of titanium alloy bars used to manufacture blades. For example, the microstructure requires that the primary α phase content of the bar is more than 30%, and the α phase size cannot exceed 0.06mm. Not only are conventional mechanical properties required to meet the requirements of GJB494A-2008 Specification for Titanium Alloy Bars for Aircraft Engine Compressor Blades (Rm≥895MPa at room temperature, Ak≥31J at room temperature, Rm≥615MPa at 400℃), but there are also high requirements for creep and fatigue properties (e.g., a certain engine model requires TC4 titanium alloy bars for blades to meet creep plastic elongation εp≤0.20% at 400℃ / 350MPa / 100h, room temperature smooth high cycle fatigue cycle >1.0×10 7 The fatigue limit of the second time is ≥480MPa).

[0003] The traditional production process of TC4 titanium alloy bars for blades is that the ingot is forged through multiple draw forgings above or below the phase transformation point to a precision forging blank, and then the precision forging is used to obtain the required microstructure and mechanical properties. The disadvantage of the traditional process is that in order to ensure the uniformity of the structure and performance consistency of the precision forging bars, the precision forging blanks are subjected to multiple draw forgings and multiple grindings between the forgings, resulting in a long production cycle and large material loss. At the same time, the precision forging force is small and the forging speed is slow, resulting in a coarse microstructure of the precision forging bars, low mechanical properties (especially tensile strength and fatigue strength), and a large difference in the organizational properties at both ends of the bars, which seriously affects the quality stability of the final blades. Therefore, it is very difficult to prepare TC4 titanium alloy bars for high-performance blades using traditional process methods, and the production cycle is long.

[0004] In view of this, the present 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 TC4 titanium alloy rod for high-performance blades and a preparation method thereof, so as to solve the problems of coarse microstructure of the rod, low mechanical properties and long production cycle.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The preparation method of the TC4 titanium alloy rod for high-performance blades comprises the following steps: firstly, mixing and pressing various raw materials into electrodes and subjecting them to three VAR smelting processes to obtain qualified TC4 titanium alloy ingots; then, forging the TC4 titanium alloy ingots through multiple drawing processes above and below the phase transformation point to obtain intermediate rod blanks A; then, rolling the intermediate rod blanks A through multiple rolling processes to obtain intermediate rod blanks B; finally, removing defects and oxide scales on the surface of the intermediate rod blanks B to obtain finished TC4 titanium alloy rods for high-performance blades.

[0008] Specifically, the preparation method comprises the following steps:

[0009] Step 1, ingot smelting: Sponge titanium, aluminum beans, aluminum vanadium alloy, aluminum silicon alloy, and titanium dioxide are mixed and pressed into electrodes, and qualified TC4 titanium alloy ingots are obtained through three VAR smeltings;

[0010] Step 2, forging of rod blanks: placing the TC4 titanium alloy ingot in a gas furnace or a resistance heating furnace, and continuously forging the ingots above and below the phase transformation point for multiple times to obtain intermediate rod blanks A (with a specification of Φ140 mm to Φ180 mm) having a primary α phase content of ≥70% and a fine and uniform structure;

[0011] Step 3, finished product rolling: placing the intermediate bar billet A obtained in step 2 in a resistance heating furnace, and rolling the intermediate bar billet B (with a specification of Φ13.5 mm to Φ75 mm) through multiple fires and large deformation;

[0012] Step 4, surface treatment: removing the surface defects and oxide scale of the intermediate bar blank B to obtain a finished TC4 titanium alloy bar for high-performance blades (with a specification of Φ12 mm to Φ70 mm).

[0013] Specifically, in step 1, the specifications of the TC4 ingot are Φ440mm~Φ720mm, and the weight percentages of each element are as follows: 6.0~6.7% Al, 4.0~4.4% V, 0.05~0.08% Si, 0.12~0.18% O, Fe≤0.20%, C≤0.02%, N≤0.01%, H≤0.008%, and the remainder is Ti and unavoidable impurities.

[0014] Specifically, in step 2, the specification of the intermediate billet A is Φ140mm-Φ180mm, and the forging is divided into three steps with a total of 8 fires, among which:

[0015] The first step is two-fire continuous re-furnace forging (gas furnace or resistance heating furnace), the first fire heating temperature is 1150 ~ 1180 ℃, the second fire heating temperature is T β +(70~110)℃, forging ratio 1.2~1.9, air cooling after forging;

[0016] The second step is two-fire continuous re-melting (resistance heating furnace) forging, the first fire heating temperature is T β -(50~80)℃, the second heating temperature is T β +(20~50)℃, forging ratio 1.5~2.0, water cooling after forging;

[0017] The third process is four-fire continuous re-melting (resistance heating furnace) forging, and the heating temperature is T β -(50~80)℃, forging ratio 1.2~1.5, air cooling after forging.

[0018] Specifically, in step 3, the specification of the intermediate bar billet B after rolling is Φ13.5mm~Φ75mm; the rolling fire is 1~3 fires, the single fire rolling deformation is 57.41%~93.26%, and the heating temperature is T β -(60~80)℃, holding time 1h~3h, air cooling after rolling. Among them, 62mm<Φ≤75mm billet is rolled in one fire, with a deformation of 71.30%~88.14%; 32mm≤Φ≤62mm billet is rolled in two fires, with a deformation of 53.95%~72.15% in the first fire, and 57.41%~88.65% in the second fire; 13.5mm≤Φ<32mm billet is rolled in three fires, with a deformation of 53.95%~72.15% in the first fire, 70.04% in the second fire, and 62.13%~93.26% in the third fire.

[0019] Specifically, the finished bar specifications in step 4 are Φ12mm to Φ70mm.

[0020] In addition, the present invention also provides a TC4 titanium alloy finished bar prepared by the preparation method described in part or in whole, wherein the primary α phase content is ≥65%, the average α phase grain size is ≤15μm, the room temperature tensile strength Rm is ≥980MPa, the room temperature impact energy Ak is ≥35J, the 400℃ high temperature tensile strength Rm is ≥715MPa, the creep plastic elongation εp is ≤0.18% at 400℃ / 350MPa / 100h, the room temperature smooth high cycle fatigue cycle is >1.0×10 7 The fatigue limit is ≥480MPa.

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

[0022] 1. The present invention increases the Si element content of the TC4 titanium alloy ingot by adding aluminum silicon alloy, thereby ensuring good creep performance of the finished bar; through multiple fires of continuous re-forging above and below the phase transformation point, combined with air cooling and water cooling in the intermediate process, the β grain size is effectively refined, and an intermediate bar blank A with a primary α phase content of ≥70% and a fine and uniform structure is obtained; through 1 to 3 fires of high-speed rolling with a large deformation amount, the consistency of the final rolling temperature at the head and tail ends of the bar is ensured, the structure is further refined, and the high tensile strength, high impact performance, and high fatigue strength of the finished bar are ensured, and the difference between the two ends is reduced.

[0023] 2. The TC4 titanium alloy rod produced by the present invention has a short production cycle but a high primary α phase content and a fine and uniform structure. It has high tensile strength, high impact performance, high fatigue strength and excellent creep performance, and can meet the requirements of relevant standards.

[0024] 3. The preparation process of the present invention is simple and feasible, and the equipment used is common, and is particularly suitable for the industrial production of TC4 titanium alloy rods for high-performance blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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.

[0026] 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 labor.

[0027] Figure 1 A flow chart of a method for preparing a TC4 titanium alloy rod for high-performance blades provided by the present invention;

[0028] Figure 2 This is a high-magnification microstructure diagram of the original 180 mm TC4 titanium alloy bar obtained in Example 1 of the present invention;

[0029] Figure 3 This is a high-magnification microstructure diagram of the original 180 mm TC4 titanium alloy bar produced by conventional technology.

[0030] Figure 4 This is a high-magnification microstructure diagram of a typical TC4 titanium alloy bar with a diameter of 70 mm prepared in Example 1 of the present invention;

[0031] Figure 5 This is a high-magnification microstructure diagram of a TC4 titanium alloy Φ70 mm typical specification bar prepared by conventional process in Comparative Example 1;

[0032] Figure 6This is a high-magnification microstructure diagram of a typical TC4 titanium alloy Φ50 mm bar prepared in Example 2 of the present invention;

[0033] Figure 7 This is a high-magnification microstructure diagram of a TC4 titanium alloy Φ50 mm typical specification bar prepared by conventional process in Comparative Example 2;

[0034] Figure 8 This is a high-magnification microstructure diagram of a typical TC4 titanium alloy Φ20 mm bar prepared in Example 3 of the present invention;

[0035] Fig. 9 This is a high-magnification microstructure diagram of a TC4 titanium alloy Φ20 mm typical specification bar prepared by conventional process in Comparative Example 3;

[0036] Fig.10 The room temperature tensile strength of the TC4 titanium alloy bar with a typical specification of Φ12mm to Φ70mm prepared by the present invention;

[0037] Fig.11 The room temperature impact performance of the TC4 titanium alloy bar with a typical specification of Φ16mm to Φ70mm prepared by the present invention;

[0038] Fig.12 The 400°C high temperature tensile strength of the TC4 titanium alloy bar with a typical specification of Φ12mm to Φ70mm prepared by the present invention;

[0039] Fig.13 The creep properties of the TC4 titanium alloy bars with typical specifications of Φ16mm to Φ70mm prepared by the present invention;

[0040] Fig.14 The room temperature smooth high cycle fatigue cycle number of the TC4 titanium alloy Φ70mm typical specification bar prepared by Example 1 of the present invention is greater than 1.0×10 7 Fatigue limit of times;

[0041] Fig.15 The room temperature smooth high cycle fatigue cycle number of the TC4 titanium alloy Φ50mm typical specification bar prepared by Example 2 of the present invention is greater than 1.0×10 7 Fatigue limit of times;

[0042] Fig.16 The room temperature smooth high cycle fatigue cycle number of the TC4 titanium alloy Φ20mm typical specification bar prepared by Example 3 of the present invention is greater than 2.0×10 7 times the fatigue limit. DETAILED DESCRIPTION

[0043] Here, exemplary embodiments will be described in detail, and 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 described in detail in the appended claims.

[0044] 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.

[0045] Example 1

[0046] This embodiment provides a method for preparing TC4 titanium alloy rods for high-performance blades. Figure 1 , specifically including the following steps:

[0047] Step 1, ingot smelting: Sponge titanium, aluminum beans, aluminum-vanadium alloy, aluminum-silicon alloy, and titanium dioxide are mixed and pressed into electrodes. After three VAR smeltings, qualified TC4 titanium alloy Φ440 mm ingots are obtained. The weight percentage of each element content is as follows: 6.0% Al, 4.4% V, 0.05% Si, 0.12% O, 0.05% Fe, 0.01% C, 0.008% N, 0.001% H, and the remainder is Ti and unavoidable impurities.

[0048] Step 2, forging of billet: Place the Φ440 mm ingot obtained in step 1 in a heating furnace, and continuously forge it into a Φ180 mm intermediate billet A through three steps above and below the phase change point, a total of 8 fires, see Figure 2 ; Figure 3 This is a high-magnification microstructure diagram of the original 180 mm TC4 titanium alloy bar produced by conventional technology. Figure 2 and 3 It can be seen that the present invention uses multiple fires above and below the phase transformation point forging continuously, combined with air cooling and water cooling in the intermediate process, to effectively refine the β grain size, and obtain an intermediate billet A with a primary α phase content of ≥70% and a fine and uniform structure;

[0049] The above three steps are specifically as follows:

[0050] The first step is two-fire continuous re-furnace (gas furnace) forging, the first fire heating temperature is 1160℃, the second fire heating temperature is T β +110℃, forging ratio 1.2~1.5, air cooling after forging;

[0051] The second step is two-fire continuous re-melting (resistance heating furnace) forging, the first fire heating temperature T β -80℃, 2nd heating temperature T β +50℃, forging ratio 1.5~1.8, water cooling after forging;

[0052] The third step is four-fire continuous re-melting (resistance heating furnace) forging, the heating temperature is T β -80℃, forging ratio 1.2~1.5, air cooling after forging.

[0053] Step 3, finished product rolling: Place the Φ180 mm intermediate bar A obtained in step 2 in a resistance heating furnace, and obtain the Φ75 mm intermediate bar B by rolling once. The deformation of the single rolling is 82.64%, and the heating temperature is T β -80℃, holding time 3h, air cooling after rolling.

[0054] Step 4, surface treatment: The Φ75 mm intermediate bar blank B obtained in step 3 is peeled to Φ70 mm using a peeling machine to obtain a TC4 titanium alloy bar for high-performance blades (I). The high-magnification structure diagram is shown in Figure 4 .

[0055] The above-obtained TC4 titanium alloy Φ70 mm bar (I) was subjected to corresponding tests (all of which are the average values ​​of 3 test values): the primary α phase content is about 70%, the average grain size is about 12 μm, the room temperature tensile strength Rm: 990 MPa, the room temperature impact energy Ak: 38 J, the 400°C high temperature tensile strength Rm: 725 MPa, the 400°C / 350 MPa / 100h creep plastic elongation εp: 0.160%, the room temperature smooth high cycle fatigue cycle number > 1.0×10 7 Fatigue limit: 480MPa.

[0056] Comparative Example 1

[0057] The high-magnification structure diagram of the Φ70mm rod prepared by traditional technology is shown in Figure 5 The primary α phase content is about 50%, the average grain size is 15-20μm, the room temperature tensile strength Rm: 980MPa, the room temperature impact energy Ak: 33J, the high temperature tensile strength Rm: 690MPa, the creep plastic elongation εp at 400℃ / 350MPa / 100h: 0.250%, the room temperature smooth high cycle fatigue cycle > 1.0×10 7 Fatigue limit: 470MPa.

[0058] Compared with the rods prepared by the traditional process, the TC4 titanium alloy rods prepared in this Example 1 have a higher primary α phase content, are finer, and are equiaxed, and the uniformity of the organization is significantly improved. In addition to the basically equivalent room temperature smooth high-cycle fatigue limit, the tensile strength, impact performance, and creep performance all have obvious advantages. In addition, due to the continuous re-forging of the billet combined with the large deformation rolling of the finished product, the production cycle is shortened by more than 50%.

[0059] Example 2

[0060] This embodiment provides another method for preparing TC4 titanium alloy rod for high-performance blades, which specifically includes the following steps:

[0061] Step 1, ingot smelting: Sponge titanium, aluminum beans, aluminum-vanadium alloy, aluminum-silicon alloy, and titanium dioxide are mixed and pressed into electrodes. After three VAR smeltings, qualified TC4 titanium alloy Φ640 mm ingots are obtained. The weight percentage of each element content is as follows: 6.4% Al, 4.2% V, 0.08% Si, 0.16% O, 0.03% Fe, 0.015% C, 0.005% N, 0.003% H, and the remainder is Ti and unavoidable impurities.

[0062] Step 2, forging of billets: Place the Φ640 mm ingot obtained in step 1 in a heating furnace, and continuously forge it into a Φ160 mm intermediate billet A through three steps above and below the phase change point, a total of 8 fires.

[0063] The first step is two-fire continuous re-melting (resistance heating furnace) forging, the first fire heating temperature is 1180℃, the second fire heating temperature is T β +70℃, forging ratio 1.5~1.8, air cooling after forging;

[0064] The second step is two-fire continuous re-melting (resistance heating furnace) forging, the first fire heating temperature T β -60℃, 2nd heating temperature T β +30℃, forging ratio 1.6~2.0, water cooling after forging;

[0065] The third step is four-fire continuous re-melting (resistance heating furnace) forging, the heating temperature is T β -60℃, forging ratio 1.2~1.5, air cooling after forging.

[0066] Step 3, finished product rolling: Place the Φ160mm intermediate bar A obtained in step 2 in a resistance heating furnace and obtain the Φ52mm intermediate bar B through two rounds of rolling; wherein, the first round is rolled from Φ160mm to Φ95mm, with a deformation of 64.75% and a holding time of 2.5h; the second round is rolled from Φ95mm to Φ52mm, with a deformation of 70.04% and a holding time of 2h. The heating temperature of both rounds is T β -70℃, air cooling after rolling.

[0067] Step 4: Use a peeling machine to peel the Φ52 mm intermediate bar blank B obtained in step 3 to Φ50 mm, and obtain a TC4 titanium alloy bar for high-performance blades (II). Figure 6 .

[0068] The above-obtained TC4 titanium alloy Φ50 mm rod was subjected to corresponding tests (all of which are the average values ​​of 3 test values): the primary α phase content is about 68%, the average grain size is about 10 μm, the room temperature tensile strength Rm: 1000 MPa, the room temperature impact energy Ak: 39 J, the high temperature tensile strength Rm: 730 MPa, the creep plastic elongation εp at 400 ° C / 350 MPa / 100 h: 0.155%, the room temperature smooth high cycle fatigue cycle > 1.0 × 10 7 Secondary fatigue limit: 637MPa.

[0069] Comparative Example 2

[0070] The high-magnification structure diagram of the Φ50mm rod prepared by traditional technology is shown in Figure 7 The primary α phase content is about 50%, the average grain size is 13-15μm, the room temperature tensile strength Rm: 985MPa, the room temperature impact energy Ak: 34J, the high temperature tensile strength Rm: 705MPa, the creep plastic elongation εp at 400℃ / 350MPa / 100h: 0.230%, the room temperature smooth high cycle fatigue cycle > 1.0×10 7 Fatigue limit: 490MPa.

[0071] Example 3

[0072] This embodiment provides another method for preparing TC4 titanium alloy rod for high-performance blades, which specifically includes the following steps:

[0073] Step 1, ingot smelting: Sponge titanium, aluminum beans, aluminum-vanadium alloy, aluminum-silicon alloy, and titanium dioxide are mixed and pressed into electrodes. After three VAR smeltings, qualified TC4 titanium alloy Φ720 mm ingots are obtained. The weight percentage of each element content is as follows: 6.7% Al, 4.0% V, 0.06% Si, 0.18% O, 0.08% Fe, 0.005% C, 0.003% N, 0.002% H, and the remainder is Ti and unavoidable impurities.

[0074] Step 2, forging of billets: Place the Φ720 mm ingot obtained in step 1 in a heating furnace, and continuously forge it into a Φ140 mm intermediate billet A through three steps above and below the phase change point, a total of 8 fires.

[0075] The first step is two-fire continuous re-furnace (gas furnace) forging, the first fire heating temperature is 1150℃, the second fire heating temperature is T β +80℃, forging ratio 1.6~1.9, air cooling after forging;

[0076] The second step is two-fire continuous re-melting (resistance heating furnace) forging, the first fire heating temperature T β -50℃, 2nd heating temperature T β+20℃, forging ratio 1.5~1.9, water cooling after forging;

[0077] The third step is four-fire continuous re-melting (resistance heating furnace) forging, the heating temperature is T β -50℃, forging ratio 1.2~1.5, air cooling after forging.

[0078] Step 3, finished product rolling: Place the Φ140mm intermediate billet A obtained in step 2 in a resistance heating furnace, and obtain the Φ21.5mm intermediate billet B through three rounds of rolling; wherein, the first round is rolled from Φ140mm to Φ95mm, with a deformation of 53.95% and a holding time of 2.5h; the second round is rolled from Φ95mm to Φ52mm, with a deformation of 70.04% and a holding time of 2h; the third round is rolled from Φ52mm to Φ21.5mm, with a deformation of 82.90% and a holding time of 1h. The heating temperatures of the three rounds are all T β -60℃, air cooling after rolling.

[0079] Step 4: Use a peeling machine to peel the Φ21.5 mm intermediate bar blank B obtained in step 3 to Φ20 mm to obtain a TC4 titanium alloy bar for high-performance blades (III). Figure 8 .

[0080] The above-obtained TC4 titanium alloy Φ20 mm rod was subjected to corresponding tests (all of which are the average values ​​of 3 test values): the primary α phase content is about 70%, the average grain size is about 8 μm, the room temperature tensile Rm: 1020 MPa, the room temperature impact Ak: 45 J, the high temperature tensile Rm: 735 MPa, the creep plastic elongation εp at 400 ° C / 350 MPa / 100 h: 0.138%, the room temperature smooth high cycle fatigue cycle number > 2.0 × 10 7 Fatigue limit: 503MPa.

[0081] Comparative Example 3

[0082] The high-magnification structure diagram of the Φ20mm rod prepared by traditional technology is shown in Fig. 9 The primary α phase content is about 45%, the average grain size is 10-13μm, the room temperature tensile strength Rm: 1005MPa, the room temperature impact energy Ak: 38J, the high temperature tensile strength Rm: 710MPa, the creep plastic elongation εp at 400℃ / 350MPa / 100h: 0.205%, the room temperature smooth high cycle fatigue cycle number> 1.0×10 7 Fatigue limit: 490MPa.

[0083] In summary, see Figure 10 to Figure 13It can be seen that the room temperature tensile strength, room temperature impact performance, and 400°C high temperature tensile strength of the TC4 titanium alloy typical specification bars prepared by the preparation method provided by the present invention all stably meet the requirements of the GJB494A standard with sufficient surplus, and the creep plastic elongation εp at 400°C / 350MPa / 100h is less than 0.18%.

[0084] Fig.14 The SN curve of the rotating bending fatigue of TC4 titanium alloy Φ70mm bar is as follows: cantilever beam rotating bending; room temperature, stress ratio R = -1, frequency f = 100Hz, life Nf = 1×10 7 , Equipment model: QBWP-10000 simply supported cantilever rotating bending fatigue testing machine, Specimen: stress concentration factor Kt = 1, diameter d = 4mm, quantity 16, fatigue limit

[0085] Fig.15 The room temperature rotating bending fatigue SN curve of TC4 titanium alloy Φ50mm bar is as follows: room temperature, stress ratio R = -1, frequency f = 80Hz, life Nf = 1×10 7 , Equipment model: QBWP-6000 simply supported cantilever rotating bending fatigue testing machine, specimen: stress concentration factor Kt = 1, diameter d = 6mm, quantity 28. Fatigue limit The median SN curve fitting equation is: lgN = 9.8776-2.7751lg (Smax-626.1106), regression determination coefficient r 2 :0.9983,Applicable life span N / cycle:4×10 4 ~1.0×10 7 .

[0086] Fig.16 The room temperature rotating bending fatigue SN curve of TC4 titanium alloy Φ20mm bar is as follows: room temperature, stress ratio R = -1, frequency f = 80Hz, life Nf = 2×10 7 , Equipment model: QBWP-6000 simply supported cantilever rotating bending fatigue testing machine, specimen: stress concentration factor Kt = 1, diameter d = 6mm, quantity 28. Fatigue limit The median SN curve fitting equation is: lgN = 6.8113-0.9926lg (Smax-502.6789), regression determination coefficient r 2 :0.9999,Applicable life span N / cycle:8×10 4 ~2.0×10 7 .

[0087] Combination Figure 14 to Figure 16It can be seen that the room temperature smooth high cycle fatigue cycle number of the typical specification bar of TC4 titanium alloy prepared by the preparation method provided by the present invention is greater than 1.0×10 7 The fatigue limits of each time are ≥480MPa.

[0088] 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.

[0089] 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 method for preparing TC4 titanium alloy rods for high-performance blades, characterized in that: First, various raw materials are mixed and pressed into electrodes, and then subjected to three VAR smeltings to obtain qualified TC4 titanium alloy ingots; then, the TC4 titanium alloy ingots are subjected to multiple-time drawing forging above and below the phase transformation point to obtain intermediate bar blanks A; then, the intermediate bar blanks A are subjected to multiple-time rolling to obtain intermediate bar blanks B; finally, surface defects and oxide scales of the intermediate bar blanks B are removed to obtain TC4 titanium alloy finished bars for high-performance blades.

2. The method for preparing the TC4 titanium alloy rod for high-performance blades according to claim 1, characterized in that: The specific steps include: Step 1, ingot smelting: Sponge titanium, aluminum beans, aluminum vanadium alloy, aluminum silicon alloy, and titanium dioxide are mixed and pressed into electrodes, and qualified TC4 titanium alloy ingots are obtained through three VAR smeltings; Step 2, forging of billets: placing the TC4 titanium alloy ingot in a gas furnace or a resistance heating furnace, and continuously forging it in multiple fires above and below the phase transformation point to obtain an intermediate billet A with a primary α phase content of ≥70% and a fine and uniform structure; Step 3, finished product rolling: placing the intermediate bar blank A in a resistance heating furnace, and obtaining the intermediate bar blank B after multiple times of large deformation rolling; Step 4, surface treatment: removing the surface defects and oxide scale of the intermediate bar blank B to obtain a finished TC4 titanium alloy bar for high-performance blades.

3. The method for preparing the TC4 titanium alloy rod for high-performance blades according to claim 1 or 2, characterized in that: In step 1, the TC4 titanium alloy ingot includes the following elements in weight percentage: 6.0-6.7% Al, 4.0-4.4% V, 0.05-0.08% Si, 0.12-0.18% O, Fe≤0.20%, C≤0.02%, N≤0.01%, H≤0.008%, and the remainder is Ti and unavoidable impurities.

4. The method for preparing the TC4 titanium alloy rod for high-performance blades according to claim 1 or 2, characterized in that: The specification of the intermediate bar blank A is Φ140mm~Φ180mm, the specification of the intermediate bar blank B is Φ13.5mm~Φ75mm, and the specification of the TC4 titanium alloy finished bar is Φ12mm~Φ70mm.

5. The method for preparing the TC4 titanium alloy rod for high-performance blades according to claim 2, characterized in that: In step 2, the intermediate bar blank A is divided into three steps with a total of 8 steps, wherein: The first step is two-fire continuous re-forging, the first fire heating temperature is 1150~1180℃, the second fire heating temperature is T β +(70~110)℃, forging ratio 1.2~1.9, air cooling after forging; The second step is two-fire continuous re-forging, the first fire heating temperature is T β -(50~80)℃, second heating temperature T β +(20~50)℃, forging ratio 1.5~2.0, water cooling after forging; The third process is four-fire continuous re-forging, and the heating temperature is T β -(50~80)℃, forging ratio 1.2~1.5, air cooling after forging.

6. The method for preparing the TC4 titanium alloy rod for high-performance blades according to claim 2, characterized in that: In step 3, the rolling number is 1 to 3, the rolling deformation of a single rolling number is 57.41% to 93.26%, and the heating temperature is T β -(60~80)℃, holding time is 1h~3h, air cooling after rolling.

7. A TC4 titanium alloy bar for high-performance blades, characterized in that: The TC4 titanium alloy finished bar is prepared by the preparation method according to any one of claims 1 to 6, characterized in that the primary α phase content of the finished TC4 titanium alloy bar is ≥ 65%, and the average α phase grain size is ≤ 15 μm.

8. The TC4 titanium alloy bar for high-performance blades according to claim 7 is characterized in that: The room temperature tensile strength Rm of the TC4 titanium alloy finished bar is ≥980MPa, and the room temperature impact energy Ak is ≥35J.

9. The TC4 titanium alloy bar for high performance blades according to claim 7, characterized in that: The TC4 titanium alloy finished bar has a 400°C high temperature tensile strength Rm≥715MPa, a 400°C / 350MPa / 100h creep plastic elongation εp≤0.18%, and a room temperature smooth high cycle fatigue cycle number>1.0×10 7 The fatigue limit is ≥480MPa.

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