A Ti175 alloy rotor blade and a preparation method thereof

Abstract

The present invention belongs to the technical field of titanium alloy hot processing, and specifically provides a Ti175 alloy rotor blade and a preparation method thereof, wherein the forged structure of the rotor blade is an equiaxed structure, wherein the α phase has a strong wire texture of <10-10> parallel to the axial direction of the blade. After the blade is subjected to two-phase zone heat treatment, the secondary α phase has <0001> Strong wire texture parallel to the blade axis. The organization with the above texture characteristics can effectively take into account the strength and plasticity of the alloy, making the strength and plasticity of the alloy higher than that of general forgings.

Description

Technical Field

[0001] The invention belongs to the field of titanium and titanium alloy processing, and specifically relates to a preparation process of Ti175 alloy rotor blades for rotor blades. Background Art

[0002] Ti175 is an α+β type hot-strength two-phase titanium alloy that can be used at 500-600℃ and has excellent comprehensive performance. The alloy has good plasticity and can be processed into products in the form of bars, forgings, rings, etc. It is currently mainly used in the fields of aviation and aerospace to manufacture key load-bearing components such as disc forgings, blades, and casings.

[0003] Engine blades are subject to heavy vibration loads and harsh operating conditions, which places high demands on the high-cycle fatigue performance of materials. Recent studies have found that the texture of alloys is a key factor in the fatigue performance of blades. Obtaining a strong texture that takes into account both alloy strength and plasticity can significantly improve the high-cycle fatigue strength of blades. Summary of the invention

[0004] The purpose of the present invention is to provide a Ti175 alloy rotor blade and a preparation method thereof, and to design a primary α phase having a strong wire texture <10-10> parallel to the blade axis, and a secondary α phase having <0001> The dual-state structure with strong wire texture parallel to the blade axis. The dual-state structure with the above texture characteristics can effectively take into account the strength and plasticity of the alloy, making the strength and plasticity of the alloy higher than that of general forgings.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A Ti175 alloy rotor blade, characterized in that:

[0007] (1) The forged microstructure of the blade is an equiaxed microstructure, wherein the α phase has a strong wire texture of <10-10> parallel to the blade axis.

[0008] (2) After the blade is heat treated in the two-phase zone, the secondary α phase has <0001> Strong filament texture parallel to the blade axis. This texture combination can achieve different texture types and densities by adjusting the heat treatment temperature.

[0009] A method for preparing a Ti175 alloy rotor blade, characterized in that the preparation of the blade comprises the following steps:

[0010] 1) Forging of ingot: Heat the alloy ingot to 1150-1200℃, keep it warm for 10-24h, then forge it out of the furnace, with a forging ratio of not less than 4; then heat the ingot to T βAt 10℃~30℃ above the phase transformation point, 2~3 times of upsetting and drawing deformation are carried out, and the total forging ratio is not less than 8, to obtain the billet after blanking in the β phase region;

[0011] 2) Forging blank preparation: The blank obtained in step 1) is heated to T β The forging blank is subjected to 3-4 times of upsetting deformation at 70℃~40℃ below the phase transformation point, and then the forging blank is subjected to T β Lengthen and roll to target size at 70℃~40℃ below the phase transformation point, and the total forging ratio shall not be less than 10;

[0012] 3) Bar forming: The forging blank obtained in step 2) is heated to T β 50℃~40℃ below the phase transformation point, formed by 2-4 fires on the precision forging machine, requiring at least 2 fires with a single deformation of not less than 30%;

[0013] 4) Blade forming: The rod prepared in step 3) is heated to T β 50℃~40℃ below the phase transformation point, hammer forging is adopted on hammer forging machine with 1~2 passes.

[0014] The components of the Ti175 alloy of the present invention are, by mass percentage, Al: 6.2%-7.50%, Zr: 3.0%-4.0%, Sn: 1.50%-3.0%, Mo: 3.50%-4.5%, Si: 0.15%-0.35%, W: 0.9%-2.0%, and the remainder is Ti and unavoidable impurity elements.

[0015] As a preferred technical solution, in the Ti175 alloy, the contents of the elements W and Mo satisfy: W ≥ Mo / 4 and 2.8% ≤ (Mo / 2+W) ≤ 3.2%; the contents of the alloying elements Zr and Si satisfy an inverse relationship and satisfy: -(Zr / 20)+0.35% ≤ Si ≤ -(Zr / 20)+0.4%.

[0016] Preferably, the forging blank is heated to T β 50℃~40℃ below the phase transformation point, formed by 2-4 fires on the precision forging machine, requiring at least 2 fires with a single deformation of not less than 45%;

[0017] The heat treatment system of the blade is: keeping warm at 950-960°C for 1-3 hours and then air cooling + keeping warm at 530-570°C for 6-10 hours and then air cooling.

[0018] The room temperature strength of the blade after heat treatment is above 1180Mpa, the yield strength is above 1010Mpa, the elongation is above 20%, the cross-sectional shrinkage is above 50%, the room temperature high cycle fatigue limit is higher than 630Mpa, and the room temperature rotary bending fatigue limit of the rod is not less than 670Mpa.

[0019] The preparation method of the present invention is simple to implement and is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the α opposite pole figure of the blade prepared in Example 1 of the present invention before and after heat treatment.

[0021] Figure 2 This is the α opposite pole figure of the blade prepared in Example 2 of the present invention before and after heat treatment.

[0022] Figure 3 This is the α opposite pole figure of the blade prepared in Example 3 of the present invention before and after heat treatment.

[0023] Figure 4 This is the α opposite pole figure of the blade prepared in Example 4 of the present invention before and after heat treatment.

[0024] Figure 5 The metallographic structures of the blades prepared in Examples 1 to 4 of the present invention after heat treatment, wherein: (a) is the metallographic structure of Example 1, (b) is the metallographic structure of Example 2, (c) is the metallographic structure of Example 3, and (d) is the metallographic structure of Example 4. DETAILED DESCRIPTION

[0025] Embodiment 1:

[0026] A Ti175 alloy ingot with a diameter of 710 mm and a weight of 2850 kg is used. The chemical composition is Al: 6.8%, Zr: 3.5%, Sn: 2.4%, Mo: 3.9%, Si: 0.22%, W: 1.2%, and the balance is Ti and unavoidable impurity elements. The T β The phase transition point is 970°C. The preparation process of Ti175 alloy rotor blades is as follows:

[0027] 1) Ingot forging: Heat the Ti175 alloy ingot with a diameter of 710 mm to 1150°C, keep it warm for 24 hours, then take it out of the furnace for upsetting and drawing forging, the upsetting deformation is 60%, the height-to-diameter ratio after drawing is 2.2, and the forging ratio of this fire is 4.5. After air cooling, it is ground; keep the billet at 1000°C for 3 hours, then take it out of the furnace for upsetting and drawing forging, the upsetting deformation is 50%, the height-to-diameter ratio after drawing is 2, and the forging ratio of this fire is 3.8, and then it is ground after air cooling; keep the billet at 990°C for 3 hours, then take it out of the furnace for upsetting and drawing forging, the upsetting deformation is 50%, and it is drawn to a bar with a diameter of 350 mm, the forging ratio of this fire is 4.5, and then it is ground after sawing.

[0028] 2) Preparation of forging blank: The blank with a specification of Ф350×700mm obtained in step 1) is kept at 930°C for 2h, then subjected to one-upsetting-one-drawing forging, with an upsetting deformation of 50%, and a height-to-diameter ratio of 2 after drawing, and then subjected to grinding after air cooling; the blank is kept at 920°C for 3h, then taken out of the furnace for one-upsetting-one-drawing forging, with an upsetting deformation of 40%, drawn to Ф290mm, and then sawed in two equal parts for grinding; the blank is kept at 910°C for 2h, then taken out of the furnace for drawing-forging, drawn to a rod with a diameter of Ф190mm, and then sawed in two equal parts for grinding; the blank is kept at 910°C for 2h, then taken out of the furnace for drawing-forging, drawn to a rod with a diameter of Ф120mm, and the total forging ratio of the forging blank is 13.

[0029] 3) Rod forming: After sawing and grinding, the 120 mm diameter rod in step 2) is kept at 930°C for 70 minutes and forged into a 80 mm diameter rod with a drawing deformation of 55%; after sawing and grinding, it is kept at 920°C for 40 minutes and forged into a 55 mm diameter rod with a drawing deformation of 53%.

[0030] 4) Blade forming: saw the bar prepared in step 3) into a section of Ф55×220mm, keep it at 930℃ for 30min, forge it into a square billet with specifications of 40×50×220mm by a press, and grind it after air cooling: keep it at 925℃ for 30min, and use a press to forge the blade.

[0031] The Ti175 alloy rotor blades prepared in Example 1 were heat treated by heat preservation at 960°C for 2 hours and then air cooling, and heat preservation at 570°C for 8 hours and then air cooling. The room temperature performance data are shown in Table 1:

[0032] Table 1 Room temperature properties of Ti175 alloy rotor blades in Example 1

[0033]

[0034] Embodiment 2:

[0035] The difference between Example 2 and Example 1 is that the rod forming stage is different. The rod forming of Example 2 is as follows:

[0036] After sawing and grinding, the Φ120 mm diameter bar in step 2) is kept at 930°C for 70 minutes and forged into a Φ95 mm bar with a drawing deformation of 37%; after sawing and grinding, it is kept at 925°C for 50 minutes and forged into a Φ70 mm bar with a drawing deformation of 45%; after sawing and grinding, it is kept at 925°C for 40 minutes and forged into a Φ55 mm bar with a drawing deformation of 39%.

[0037] Example 2 adopts three-fire forming, and the forming amount of each fire is less than that of Example 1, which leads to a weaker texture of the blade (compared with Figure 1 and Figure 2 ), and the fatigue limit is slightly lower than that of Example 1.

[0038] Table 2 Room temperature properties of Ti175 alloy rotor blades in Example 2

[0039]

[0040] Example 3

[0041] Example 3 is a comparative example of Example 1. The difference from Example 1 is the bar forming step. Example 3 adopts a multi-fire small deformation method, which does not meet the requirement that the single deformation amount of at least 2 fires is not less than 30%. The other processes are the same as Example 1. The specific steps are as follows:

[0042] Rod forming: After sawing and grinding the 120 mm diameter rod in step 2), keep it at 930°C for 70 minutes, forge it into a 105 mm diameter rod, and the elongation deformation is 23%; keep it at 930°C for 60 minutes, forge it into a 95 mm diameter rod, and the elongation deformation is 19%; after sawing and grinding, keep it at 925°C for 50 minutes, forge it into a 82 mm diameter rod, and the elongation deformation is 29%; after sawing and grinding, keep it at 925°C for 45 minutes, forge it into a 70 mm diameter rod, and the elongation deformation is 27%; after sawing and grinding, keep it at 925°C for 40 minutes, forge it into a 55 mm diameter rod, and the elongation deformation is 39%.

[0043] By the attached Figure 5 It can be seen that the structure obtained by this process is not significantly different from that of Example 1, but the structure of Example 3 does not form a typical strong wire texture. From Table 3, it can be seen that the strength and plasticity of the alloy are not superior to those of Example 1, and the fatigue strength is also significantly lower than that of Example 1.

[0044] Table 3 Room temperature properties of Ti175 alloy rotor blades in Example 3

[0045]

[0046] Embodiment 4:

[0047] The alloy ingot with a diameter of 680 mm and a weight of 2615 kg is used. The chemical composition is Al: 7.3%, Zr: 4.2%, Sn: 1.9%, Mo: 4.0%, Si: 0.33%, W: 0.77%, and the balance is Ti and unavoidable impurity elements. The T β The phase transition point is 990°C. The preparation process of the alloy rotor blade is as follows:

[0048] 1) Open forging of ingot: heat the alloy ingot with a diameter of 680 mm to 1200°C, keep it warm for 10 hours, then take it out of the furnace for upsetting and drawing forging, the upsetting deformation is 50%, the height-to-diameter ratio after drawing is 2.3, and it is ground after air cooling; keep the billet at 1020°C for 3 hours, then take it out of the furnace for upsetting and drawing forging, the upsetting deformation is 45%, first draw it to a square billet of 550 mm, return it to the furnace and keep it at 1010°C for 2 hours, continue to draw it to 380 mm in square, return it to the furnace and keep it at 1005°C for 1 hour, continue to draw it to 340 mm in square, return it to the furnace and keep it at 1000°C for 1 hour, continue to draw it to a 300 mm bar, and grind it after sawing.

[0049] 2) Preparation of forging billet: The billet with a specification of Ф300×660 mm obtained in step 1) is kept at 945° C. for 3 hours and then subjected to one-upsetting-one-drawing forging, with an upsetting deformation of 55% and a height-to-diameter ratio of 2.2 after drawing, and then subjected to grinding after air cooling; the billet is kept at 940° C. for 3 hours and then taken out of the furnace for one-upsetting-one-drawing forging, with an upsetting deformation of 50% and a height-to-diameter ratio of 2.5 after drawing, and then subjected to grinding after air cooling; the billet is heated at 935° C. for 3 hours and then taken out of the furnace for one-upsetting-one-drawing forging, with an upsetting deformation of 50% and a height-to-diameter ratio of 2.5 after drawing, and then subjected to grinding after air cooling; After keeping warm for 3 hours, the billet is taken out of the furnace for one upsetting and one drawing forging, the upsetting deformation is 30%, and the billet is drawn to Ф200mm. After sawing and cutting, it is ground; the billet is kept warm at 930℃ for 2 hours, then taken out of the furnace for drawing forging, drawn to a bar with a diameter of Ф150mm, and cut into two equal parts for grinding; the billet is kept warm at 920℃ for 2 hours, then taken out of the furnace for drawing forging, drawn to a bar with a diameter of Ф120mm, and the total forging ratio of the forging billet is 14.4.

[0050] 3) Rod forming: After sawing and grinding, the 120 mm diameter rod in step 2) is kept at 950°C for 60 minutes and forged into a 100 mm diameter rod with a drawing deformation of 31%; after sawing and grinding, it is kept at 940°C for 50 minutes and forged into a 80 mm diameter rod with a drawing deformation of 36%; after sawing and grinding, it is kept at 940°C for 40 minutes and forged into a 65 mm diameter rod with a drawing deformation of 32%.

[0051] 4) Blade forming: The bar prepared in step 3) is sawn into a section of 65×200 mm in diameter, kept at 940° C. for 40 min, forged into a square billet of 55×60×200 mm using a press, and then the blade is die-forged.

[0052] The rotor blades prepared in Example 4 were heat treated by heat preservation at 960°C for 2 hours and then air cooling + heat preservation at 560°C for 6 hours and then air cooling. The room temperature performance data are shown in Table 4:

[0053] Table 4 Room temperature properties of alloy rotor blades in Example 4

[0054]

[0055] Matters not covered by the present invention are known technologies.

[0056] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A Ti175 alloy rotor blade, characterized in that: The blade forging structure is an equiaxed structure, wherein the primary α phase has a strong wire texture of <10-10> parallel to the blade axis; the secondary α phase of the blade after two-phase zone heat treatment has <0001> Strong filament texture parallel to the blade axis.

2. A method for preparing the Ti175 alloy rotor blade according to claim 1, characterized in that: The preparation of leaves includes the following steps: 1) Forging of ingot: Heat the alloy ingot to 1150-1200℃, keep it warm for 10-24h, then forge it out of the furnace, with a forging ratio of not less than 4; then heat the ingot to T β At 10℃~30℃ above the phase transformation point, 2~3 times of upsetting and drawing deformation are carried out, and the total forging ratio is not less than 8, to obtain the billet after blanking in the β phase region; 2) Forging blank preparation: The blank obtained in step 1) is heated to T β The forging blank is subjected to 3-4 times of upsetting deformation at 70℃~40℃ below the phase transformation point, and then the forging blank is subjected to T β Lengthen and roll to target size at 70℃~40℃ below the phase transformation point, and the total forging ratio shall not be less than 10; 3) Bar forming: The forging blank obtained in step 2) is heated to T β 50℃~40℃ below the phase transformation point, formed by 2~4 fires on the precision forging machine, requiring at least 2 fires with a single deformation of not less than 30%; 4) Blade forming: The rod prepared in step 3) is heated to T β 50℃~40℃ below the phase transformation point, hammer forging is adopted on hammer forging machine with 1~2 passes.

3. The method for preparing the Ti175 alloy rotor blade according to claim 2, characterized in that: The Ti175 alloy components are as follows: Al: 6.2% to 7.50%, Zr: 3.0% to 4.0%, Sn: 1.50% to 3.0%, Mo: 3.50% to 4.5%, Si: 0.15% to 0.35%, W: 0.9% to 2.0%, and the remainder is Ti and unavoidable impurity elements.

4. The method for preparing the Ti175 alloy rotor blade according to claim 3, characterized in that: In the Ti175 alloy, the contents of the elements W and Mo satisfy: W≥Mo / 4 and 2.8%≤Mo / 2+W≤3.2%; the contents of the alloying elements Zr and Si satisfy an inverse relationship and satisfy: -(Zr / 20)+0.35%≤Si≤-(Zr / 20)+0.4%.

5. The method for preparing the Ti175 alloy rotor blade according to claim 2, characterized in that: Step 3) The bar forming stage requires at least 2 fires with a single deformation of not less than 45%.

6. The method for preparing the Ti175 alloy rotor blade according to claim 2, characterized in that: The blades hammer-forged in step (4) are heat-treated, and the heat-treatment conditions of the blades are: heat preservation at 950-960°C for 1-3 hours and then air cooling + heat preservation at 530-570°C for 6-10 hours and then air cooling.

7. The method for preparing the Ti175 alloy rotor blade according to claim 6, characterized in that: The room temperature strength of the blade after heat treatment is above 1180Mpa, the yield strength is above 1010Mpa, the elongation is above 20%, the cross-sectional shrinkage is above 50%, the room temperature high cycle fatigue limit is higher than 630Mpa, and the room temperature rotary bending fatigue limit of the rod is not less than 670Mpa.

Images