Preparation method and application of TC11 titanium alloy cake with high flaw detection level

Abstract

The application discloses a preparation method of TC11 titanium alloy cake blank with high flaw detection level. The method comprises the following steps: adopting the mode of above-phase transition point forging, below-phase transition point forging and above-phase transition point forging to open the blank of TC11 titanium alloy ingot, adopting two-phase zone forging for multiple forging times to form a rod blank, and adopting isothermal forging to perform cake blank forming forging after blanking. The temperature, forging mode, forging ratio and other parameters of each stage are precisely controlled in the whole forging process, the deformation uniformity and the uniformity of the structure are improved, and especially, the cake is formed by isothermal forging, so that the uniformity of the structure of the cake blank can be obviously improved. The preparation method is suitable for the industrial production of TC11 titanium alloy cake blanks with the thickness of 100-200 mm and the diameter of 400-600 mm, the production process is advanced, the preparation flow is short, the operation is simple and effective, the product has the characteristics of high uniformity of the structure, high flaw detection noise level and the like.

Description

Technical Field

[0001] This invention relates to the field of forging technology, and to a method for preparing TC11 titanium alloy blanks with high flaw detection level. Background Technology

[0002] Titanium alloys are widely used in aerospace and other fields due to their high specific strength and excellent corrosion resistance. Titanium alloy compressor discs and fan discs are generally produced by die forging from blanks. High-level flaw detection of the blank is a key step in preparing high-quality disc forgings. With the rapid development of high-thrust aero engines, the size of disc parts required for engines is increasing, and the manufacturing difficulty of large-size blanks is also increasing. A prominent example is the requirement for high-level flaw detection of flat-bottomed holes (φ0.8-12dB) on large-size blanks.

[0003] Currently, large-sized TC11 titanium alloy blanks are mostly produced by multiple upsetting and drawing of bar stock. For example, CN 109622839 proposes a method for obtaining uniformly structured TC11 titanium alloy round blanks through multiple upsetting and drawing of bar stock; CN 109622837 proposes a method and apparatus for obtaining high-flaw-detection-level TC11 titanium alloy blanks through multiple upsetting and drawing of bar stock after isothermal forging; CN202011374096.X proposes a forging method and apparatus for optimizing the uniformity of the microstructure of the blank through multiple upsetting and drawing of bar stock. While these inventions can all obtain blanks with high flaw-detection levels, the multiple forging processes and complex operations increase the risk of microstructure inhomogeneity and flaw detection inconsistencies (resulting in low blank yield rates in practice). Therefore, there is an urgent need to develop a simple and effective method for preparing large-sized TC11 titanium alloy blanks with high flaw detection capabilities. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to develop a simple and effective method for preparing TC11 titanium alloy blanks with high flaw detection capabilities.

[0005] The technical solution of this invention is a method for preparing a TC11 titanium alloy blank with high flaw detection level, comprising the following steps:

[0006] Step 1: Forging the billet

[0007] The TC11 titanium alloy ingot is prepared by forging above the phase transformation point → forging below the phase transformation point → forging above the phase transformation point; upset forging is performed at 100℃~200℃ above the phase transformation point; upset forging is performed at 30~50℃ below the phase transformation point; after forging, it is directly returned to the furnace for recrystallization heat treatment at a temperature 30~50℃ above the β transformation temperature, held at the temperature for an appropriate time, and then removed from the furnace, followed by one upset forging, and then cooled.

[0008] Step 2: Forging of intermediate billets

[0009] The billet after the initial forging is heated to 30-60°C below the phase transformation point and subjected to 3-4 upsetting and drawing forging cycles, with the forging ratio controlled between 2.0 and 3.0. After forging, it is cooled.

[0010] Step 3: Billet forging

[0011] The billet after forging in step 2 is heated to 30-60°C below the phase transformation point and drawn into a bar in one pass with a forging ratio of 1.8-2.5. After forging, it is cooled.

[0012] Step 4: Forging the blank

[0013] After the bar stock obtained in step 3 is finished and cut, it is heated to 30℃~60℃ below the β phase transformation point and subjected to one-time isothermal forging upsetting and rounding to obtain the target billet, which is then cooled after forging. The isothermal forging deformation rate ranges from 2 to 10 mm / s, the deformation amount is 50~85%, and the die heating temperature is 920~950℃.

[0014] According to claim 1, the method for preparing a high-flaw-detection-level TC11 titanium alloy blank is preferably characterized in that, in step 1, the forging process involves 2 to 3 upsetting and drawing forging cycles at a temperature 100°C to 200°C above the phase transformation point; and 1 to 2 upsetting and drawing forging cycles at a temperature 30°C to 50°C below the phase transformation point; with the forging ratio per cycle controlled between 1.8 and 3.0.

[0015] According to claim 1, the method for preparing a high-level flaw detection TC11 titanium alloy blank is preferably wherein, in step 2, the heating temperature is 30-50°C below the phase transformation point; and in step 3, the heating temperature is 30-50°C below the phase transformation point.

[0016] In step 3, the mold heating temperature is 930-950℃.

[0017] According to claim 1, in the method for preparing a high-flaw-detection-level TC11 titanium alloy blank, preferably, in the isothermal forging step 4, the height-to-diameter ratio of the blank is 1.8 to 3.2, and the rounded corners of the blank are r = 10 to 15 mm.

[0018] According to claim 1, in the method for preparing a high-level flaw detection TC11 titanium alloy blank, preferably, in the isothermal forging step 4, graphite powder is applied to the mold for lubrication.

[0019] Preferably, the post-forging cooling described in steps 1-4 is post-forging air cooling.

[0020] According to claim 1, the method for preparing a high-level flaw detection TC11 titanium alloy blank is preferably characterized in that the holding time coefficient of the blank in steps 1 to 4 is in the range of 0.7 to 1.0 min / mm.

[0021] According to claim 1, the method for preparing a high-level flaw detection TC11 titanium alloy blank is preferably wherein, in step 4, the thickness of the TC11 titanium alloy target blank is 100-200 mm.

[0022] According to claim 1, a method for preparing a high-level flaw detection TC11 titanium alloy blank is preferably described in step 4, wherein the cross-sectional diameter of the TC11 titanium alloy target blank is 400-600 mm.

[0023] The design concept of the technical solution of this invention is as follows: (1) The alternating design of the ingot at the phase transformation point temperature can make the grains fine and uniform by recrystallization. (2) During ultrasonic non-destructive testing, the level of noise signal reflects the uniformity of the structure. Coarse non-uniform structure and lamellar α bundles (or Widmanstätten structure) may cause high noise in titanium alloys. In traditional free forging, the metal in contact with the tool cools down quickly and the friction is large, resulting in a deformation dead zone, which leads to the poor uniformity of the TC11 material. Isothermal forging can improve and eliminate the deformation non-uniformity of the blank. At 30℃~60℃ below the β phase transformation point and at a low deformation rate of 2-10 mm / s, the α grains recrystallize completely, and the obtained structure is uniform. If the temperature is too low, the deformation resistance is too high; if the temperature is too high, the temperature rise is likely to occur during large deformation, which can easily produce non-uniform structure. Using a large deformation of 50-85% results in good forging penetration and a more uniform and fine equiaxed structure, which is beneficial for improving the flaw detection level of TC11 titanium alloy discs.

[0024] This invention also provides the application of the high-flaw-detection-level TC11 titanium alloy blank prepared by the above method in aero-engine disc forgings. The high flaw-detection level is φ0.8-12dB.

[0025] The beneficial effects of this invention are:

[0026] This invention effectively reduces the number of forging passes from TC11 titanium alloy bar to billet (this invention actually only requires one pass, and the process from bar to billet is only one pass, whereas in the prior art, the process from bar to billet requires multiple upsetting and drawing processes). The resulting TC11 titanium alloy billet has a uniform microstructure and flaw detection noise reaching 0.8-12dB in the flat-bottomed hole. The entire process is short, simple, and effective. Attached Figure Description

[0027] Figure 1 This is a physical image of the Φ450mm×150mm blank obtained by the forging method of the present invention.

[0028] Figure 2 The image shows the water immersion test results for a Φ450mm×150mm blank obtained by the forging method of this invention. The reflected wave amplitude is uniform, and the clutter does not exceed φ0.8-12dB.

[0029] Figure 3 These are macroscopic photographs of the Φ450mm×150mm blank obtained by the forging method of this invention, showing its transverse and longitudinal directions.

[0030] Figure 4a and Figure 4b The microstructure at the center of the cross section at half the thickness of the Φ450mm×150mm blank obtained by the forging method of the present invention. Figure 4a and Figure 4b The corresponding microstructures at different magnifications.

[0031] Figure 5a and Figure 5b The microstructure is the area at half the radius of half the thickness of the Φ450mm×150mm blank obtained by the forging method of this invention. Figure 5a and Figure 5b The corresponding microstructures at different magnifications.

[0032] Figure 6a and Figure 6b The microstructure is the edge of a Φ450mm×150mm blank at half its thickness obtained by the forging method of this invention. Figure 6a and Figure 6b The corresponding microstructures at different magnifications.

[0033] Figure 7 The results of water immersion testing of the blank obtained by the traditional free forging method show that the reflected wave amplitude is not uniform, and the clutter in the center and edge parts exceeds φ0.8-12dB. Detailed Implementation

[0034] Example 1: Preparation of TC11 titanium alloy blank with dimensions of Φ450mm×150mm.

[0035] Step 1: Opening the blank

[0036] Using φ760 TC11 ingots as raw material, with a phase transformation point of 1010℃, the material is heated to 200℃ above the phase transformation point and held for 8 hours. Then, it undergoes two upsetting and drawing processes, with the forging ratio controlled at approximately 2.5 per process. After forging, the material is returned to the furnace at 50℃ below the phase transformation point and held for 2 hours. Then, it undergoes two more upsetting and drawing processes, with the forging ratio controlled between 2 and 2.5 per process. After forging, the material is returned to the furnace at 30℃ above the phase transformation point and held for 4 hours. Then, it undergoes upsetting and square drawing. After forging, the material is air-cooled to room temperature to remove surface cracks.

[0037] Step 2: Forging of intermediate billets

[0038] The billet, after being forged in the first stage, is heated to 50°C below the phase transformation point and held for 5 hours. It is then forged in four stages, with a 1-2 hour reheat in between. The forging ratio is controlled between 2 and 2.5. The forging method involves repeated upsetting and squaring with chamfering. The forging is followed by air cooling and grinding.

[0039] Step 3: Billet forging

[0040] The billet after forging in step 2 is heated to 50°C below the phase transformation point, held for 5 hours, and then drawn in one pass with a forging ratio of 2.2. After forging, it is air-cooled and machined into a φ230mm bar.

[0041] Step 4: Forging the blank

[0042] The light bar prepared in step 3 is cut and chamfered, with a height-to-diameter ratio of 2.8. It is then upset to Φ460mm×160mm in a single pass using isothermal forging equipment. The billet heating temperature is 40℃ below the β phase transformation point (i.e., 970℃), and the die temperature is set to 950℃. The deformation rate is 10mm / s for the first 300mm of travel and 2mm / s for the next 180mm; the forging upsetting deformation is 75%.

[0043] The TC11 titanium alloy blank prepared in this embodiment was surface-machined ( Figure 1 The dimensions are Φ450mm×150mm. Ultrasonic testing and acceptance were performed according to HB5265 and HB5266. The noise in the φ0.8 flat-bottom hole of this TC11 titanium alloy blank did not exceed -12dB (Figure 2 and Table 1); after dissection, the low magnification ( Figure 3 The microstructure of the cross-section center, half radius, and edge regions at half thickness ( ) and ( ) Figure 4a and Figure 4b The results were uniform. The dough was kept at 950℃ for 1 hour, then air-cooled and kept at 530℃ for 6 hours, followed by air cooling. The performance is shown in Table 2, and it can be seen that all the technical requirements are met.

[0044] Table 1 Water Immersion Testing of TC11 Titanium Alloy Blanks

[0045]

[0046] Note: Reflected wave φ0.8-12dB (corresponding to 20%)

[0047] Table 2 Properties of TC11 titanium alloy blanks

[0048]

[0049] Example 2:

[0050] Preparation of TC11 titanium alloy blanks with dimensions of Φ600mm×100mm.

[0051] Step 1: Opening the blank

[0052] Using φ760 TC11 ingots as raw material, with a phase transformation point of 1010℃, the material is heated to 200℃ above the phase transformation point and held for 8 hours. Then, it undergoes two upsetting and drawing processes, with the forging ratio controlled at approximately 2.5 per process. After forging, the material is returned to the furnace at 50℃ below the phase transformation point and held for 2 hours. Then, it undergoes two more upsetting and drawing processes, with the forging ratio controlled between 2 and 2.5 per process. After forging, the material is returned to the furnace at 30℃ above the phase transformation point and held for 4 hours. Then, it undergoes upsetting and square drawing. After forging, the material is air-cooled to room temperature to remove surface cracks.

[0053] Step 2: Forging of intermediate billets

[0054] The billet, after being forged in the first stage, is heated to 50°C below the phase transformation point and held for 5 hours. It is then forged in four stages, with a 1-2 hour reheat in between. The forging ratio is controlled between 2.2 and 2.5. The forging method involves repeated upsetting and squaring with chamfering. The forging is followed by air cooling and grinding.

[0055] Step 3: Billet forging

[0056] The billet after forging in step 2 is heated to 50°C below the phase transformation point, held for 5 hours, and then drawn in one pass with a forging ratio of 2.0. After forging, it is air-cooled and machined into a φ275mm bar.

[0057] Step 4: Forging the blank

[0058] The light bar prepared in step 3 is cut and chamfered, with a height-to-diameter ratio of 2.1. It is then upsetting to Φ615mm×115mm in a single pass using isothermal forging equipment. The billet heating temperature is 40℃ below the β phase transformation point (i.e., 970℃), and the die temperature is set to 930℃. The deformation rate is 10mm / s for the first 300mm of travel and 2mm / s for the next 160mm; the forging upsetting deformation is 80%.

[0059] The TC11 titanium alloy blank prepared in this embodiment, after surface polishing, has a size of Φ600mm×100mm. Ultrasonic testing and acceptance were performed according to HB5265 and HB5266. The clutter in the φ0.8 flat-bottom hole of the TC11 titanium alloy blank did not exceed -12dB; the low-magnification and microstructure of the blank after dissection were uniform. The blank was held at 950℃ for 1 hour, then air-cooled, held at +530℃ for 6 hours, and then air-cooled again. The properties are shown in Table 3, and all meet the technical requirements.

[0060] Table 3 Properties of TC11 titanium alloy blanks

[0061]

[0062] Example 3:

[0063] Preparation of TC11 titanium alloy blanks with dimensions of Φ400mm×200mm.

[0064] Step 1: Opening the blank

[0065] Using φ580 TC11 ingots as raw material, with a phase transformation point of 1010℃, the material is heated to 200℃ above the phase transformation point and held for 8 hours. Then, it undergoes two upsetting and drawing processes, with the forging ratio controlled at approximately 2.5 per process. After forging, the material is returned to the furnace at 50℃ below the phase transformation point and held for 2 hours. Then, it undergoes two more upsetting and drawing processes, with the forging ratio controlled between 2 and 2.5 per process. After forging, the material is returned to the furnace at 30℃ above the phase transformation point and held for 4 hours. Then, it undergoes upsetting and square drawing. After forging, the material is air-cooled to room temperature to remove surface cracks.

[0066] Step 2: Forging of intermediate billets

[0067] The billet, after being forged in the first stage, is heated to 50°C below the phase transformation point and held for 5 hours. It is then forged in four stages, with a 1-2 hour reheat in between. The forging ratio is controlled between 2.4 and 2.8. The forging method involves repeated upsetting and squaring with chamfering. The forging is followed by air cooling and grinding.

[0068] Step 3: Billet forging

[0069] The billet after step 2 forging is heated to 50°C below the phase transformation point, held for 5 hours, and then drawn in one pass with a forging ratio of 2.1. After forging, it is air-cooled and machined into φ250mm bars.

[0070] Step 4: Forging the blank

[0071] The light bar prepared in step 3 is cut and chamfered, with a height-to-diameter ratio of 2.3. It is then upsetting to Φ410mm×210mm in a single pass using isothermal forging equipment. The billet heating temperature is 40℃ below the β phase transformation point (i.e., 970℃), and the die temperature is set to 950℃. The deformation rate is 10mm / s for the first 200mm of stroke and 2mm / s for the next 160mm; the forging upsetting deformation is 63%.

[0072] The TC11 titanium alloy blank prepared in this embodiment, after surface polishing, has a size of Φ400mm×200mm. Ultrasonic testing and acceptance were performed according to HB5265 and HB5266. The noise in the φ0.8 flat-bottom hole of the TC11 titanium alloy blank did not exceed -12dB; the low-magnification and microstructure of the blank after dissection were uniform. The blank was held at 950℃ for 1 hour, then air-cooled, held at +530℃ for 6 hours, and then air-cooled again. The properties are shown in Table 4, and all meet the technical requirements.

[0073] Table 3 Properties of TC11 titanium alloy blanks

[0074]

[0075] Comparative Example 1:

[0076] Using φ230mm TC11 bar stock forging in step 1, the heating temperature was 40℃ below the β phase transformation point. Conventional free forging was employed in 5 passes. The first 4 passes involved 4 forgings and 4 drawings along the axial direction, with the forging ratio controlled between 2 and 2.5 per pass. The final pass involved upsetting to 160mm, resulting in a Φ460mm × 160mm blank. The flaw detection results after surface finishing of the blank are as follows... Figure 5a and Figure 5b The flaw detection result did not meet the φ0.8-12dB requirement. After dissection of the billet, it was found that there was uneven microstructure on the surface, core, and edges.

[0077] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing a TC11 titanium alloy blank with high flaw detection level, characterized in that: Includes the following steps: Step 1: Forging the billet The TC11 titanium alloy ingot is prepared by forging above the phase transformation point → forging below the phase transformation point → forging above the phase transformation point; it is then subjected to 2 to 3 upsetting and drawing forgings at 100℃ to 200℃ above the phase transformation point; and 1 to 2 upsetting and drawing forgings at 30℃ to 50℃ below the phase transformation point; the forging ratio per forging is controlled between 1.8 and 3.0; after forging, it is directly returned to the furnace for recrystallization heat treatment at a temperature 30 to 50℃ above the β transformation temperature, held at the temperature for an appropriate time, and then removed from the furnace, followed by one upsetting and drawing forging, and then cooled. Step 2: Forging of intermediate billets The billet after the initial forging is heated to 30-60°C below the phase transformation point and subjected to 3-4 upsetting and drawing forging cycles, with the forging ratio controlled between 2.0 and 3.

0. After forging, it is cooled. Step 3: Billet forging The billet after forging in step 2 is heated to 30-60°C below the phase transformation point and drawn into a bar in one pass with a forging ratio of 1.8-2.

5. After forging, it is cooled; the die heating temperature is 930-950°C. Step 4: Forging the blank After the bar stock obtained in step 3 is finished and cut, it is heated to 30℃~60℃ below the phase transformation point and subjected to one-pass isothermal forging upsetting and rounding to obtain the target billet, which is then cooled after forging. In the isothermal forging, the height-to-diameter ratio of the billet is 1.8~3.2, and the rounded corners of the billet are r=10~15mm. The deformation rate of the isothermal forging ranges from 2-10 mm / s, the deformation amount is 50~85%, and the die heating temperature is 920~950℃. The heat preservation time coefficient of the billet in steps 1 to 4 is in the range of 0.7 to 1.0 min / mm.

2. The method for preparing a high-level flaw detection TC11 titanium alloy blank according to claim 1, characterized in that: In step 2, the heating temperature is 30-50°C below the phase transition point; in step 3, the heating temperature is 30-50°C below the phase transition point.

3. The method for preparing a high-level flaw detection TC11 titanium alloy blank according to claim 1, characterized in that: The post-forging cooling described in steps 1-4 is post-forging air cooling.

4. The method for preparing a high-level flaw detection TC11 titanium alloy blank according to claim 1, characterized in that: In the isothermal forging process described in step 4, graphite powder is applied to the mold for lubrication.

5. The method for preparing a high-level flaw detection TC11 titanium alloy blank according to claim 1, characterized in that: In step 4, the thickness of the TC11 titanium alloy target blank is 100-200 mm.

6. The method for preparing a high-level flaw detection TC11 titanium alloy blank according to claim 1, characterized in that: In step 4, the diameter of the TC11 titanium alloy target blank cross section is 400-600 mm.

7. The application of the high-flaw-detection-level TC11 titanium alloy blank prepared by the method of claim 1 in the field of aero-engine disc forgings.

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