A forging method of an oversized TC32 titanium alloy forging blank

Abstract

This invention belongs to the field of metal materials science and technology processing, and relates to a forging method for ultra-large TC32 titanium alloy forging billets. This invention proposes a maximum diagonal length Dmax for large-sized billets, where the ingot or billet satisfies 1.0 ≤ H / D. 始max ≤2.5 range, and h 始 = (0.01~0.3)×D 始max When upsetting at a uniform speed within the hot working temperature range of 840℃~1200℃, the bulging deformation in the middle of large-sized TC32 titanium alloy ingots or billets is uniform, and the deformation dead zone range at the upper and lower ends of the billet is small. This process variable was introduced in stage I, and the optimal D for this stage was determined. max The amount of pull-out per hammer blow and D max The two-stage hammer reduction is also specified in the process specifications, which significantly improves the forging penetration and uniformity of large-size TC32 titanium alloy billets during the drawing stage within the corresponding range. Through reasonable process settings, this invention achieves precise control of the entire forging process, improves the stability and consistency of forging processes in different batches, and thus improves batch stability.

Description

Technical Field

[0001] This invention belongs to the field of metal materials science and technology processing, and relates to a forging method for ultra-large TC32 titanium alloy forging billets. Background Technology

[0002] TC32 titanium alloy (Ti-5Al-3Mo-3Cr-1Zr) is a new type of low-cost, high-performance titanium alloy developed by the Beijing Institute of Aeronautical Materials through low-cost alloying and comprehensive strengthening technologies (authorized patent number: ZL201218001211.9). This alloy has a wide hot working process window, excellent impact performance, high fatigue performance, and especially excellent strength-toughness matching. While significantly improving fracture toughness, it maintains high strength, and its comprehensive performance is significantly higher than that of TC4 and TA15 titanium alloys. Moreover, the overall processing cost is low, making it most suitable for development into a new generation of backbone structural titanium alloy materials in my country.

[0003] With the increasing demands on aircraft design performance, the high performance, large size, and integrated construction of key titanium alloy components have become important development directions. Over the past two decades, my country's large-scale integral forging technology has developed rapidly, and the country has successively acquired forging hydraulic presses of different levels, some exceeding 10,000 tons, such as the 200MN forging hydraulic press from Shaanxi Hongyuan Forging, the 400MN forging hydraulic press from Triangle Defense, and the 800MN forging hydraulic press from Deyang Erzhong. These advancements have already overcome the challenge of forging hydraulic presses with a projected area of ​​2m². 2 The manufacturing technology of large integral forgings is also crucial. Equally important is the development of homogenization forging technology for large / ultra-large forging billets or bars, which provides a solid raw material foundation for overcoming the challenges in manufacturing large integral forgings. Currently, raw material plants use free forging methods to produce large / ultra-large titanium alloy forging billets or bars. This involves multiple upsetting and drawing processes on hydraulic equipment to obtain bars or intermediate billets that meet performance specifications. However, with the increase in ingot / forging billet size and weight, the forging technology becomes significantly more difficult. The most common problems are: high overall deformation resistance of the billet, multiple forging processes, and high equipment tonnage requirements; difficulty in refining the microstructure at high and low magnification levels, leading to unevenness; high noise levels and severe attenuation in ultrasonic testing; large fluctuations in mechanical property data; and poor batch stability.

[0004] Currently, existing forging technology cannot solve the technical challenges of uniformity of forging microstructure and properties and batch stability of ultra-large TC32 titanium alloy forgings. Summary of the Invention

[0005] The purpose of this invention is to provide a forging method for ultra-large TC32 titanium alloy forging billets, breaking through the technical bottleneck of forging large / ultra-large titanium alloy forging billets or bars, and meeting the demand of my country's new generation of aircraft for large integral titanium alloy forgings.

[0006] It is well known that titanium alloy ingot is subjected to multi-process upsetting and elongation deformation when free forging, so as to finally obtain a billet or a rod with uniform structure and performance. The forging temperature, the forging deformation, the forging rate, the reduction rate, the reduction amount and other variables are the most important key process parameters. The existing public literatures propose a large number of free forging methods or technologies in view of the characteristics of different alloys. It is found through experimental research that there are certain limitations in the preparation of TC32 titanium alloy super-large specification TC32 titanium alloy forging billet through the existing multi-parameter variable combined forging process, especially the high and low magnification structure and performance uniformity is not ideal, and the batch stability is poor. On the one hand, it is related to the characteristics of the free forging method. When the billet is subjected to upsetting deformation, the free flow of the metal is affected due to the contact friction of the upper and lower surfaces with the anvil, so there is a considerable degree of deformation dead zone, and there is a significant difference between the core and the edge deformation. These deformation differences that cannot be eliminated during upsetting must be improved during subsequent elongation forging, so the accurate control of the elongation process is extremely critical. On the other hand, the existing technologies mainly focus on the accurate control of the forging temperature, the deformation amount and the deformation rate between forging heats, and pay insufficient attention to the accurate control of the billet size design, the upsetting and elongation stages, especially the control of the per-anvil reduction amount parameter, which causes large differences in the action on the billet by each anvil. Considering the complexity of the billet change in each stage of the actual free forging, the deformation inhomogeneity accumulated on the billet is finally reflected in the inhomogeneity of the billet structure and performance. Obviously, the larger the billet size or single weight, the more obvious the accumulation effect, and the higher the difficulty of the billet forging technology.

[0007] The present application proposes an important characteristic parameter of the billet cross section during free forging: the maximum diagonal length Dmax. Obviously, for a circular ingot, the maximum diagonal length is the ingot diameter; for a square billet, the maximum diagonal length is equal to the diagonal length; for an octagonal or hexadecagonal billet, the maximum diagonal length can better reflect the meaning of Dmax, which is the largest value among all the diagonal lengths. The maximum diameter of the billet after upsetting is significantly related to the deformation amount, and obviously determines the Dmax size of the billet in the subsequent stage. In each anvil pressing of the subsequent elongation, the upper anvil always preferentially presses the position corresponding to the billet cross section Dmax, and finally the overall uniform elongation deformation of the billet is achieved. Obviously, as the billet size becomes larger, the Dmax size changes more greatly in the change process of the billet cross section shape from circle to square to octagon / hexadecagon / circle, and the existing technology does not pay attention to this change characteristic. The single pressing amount in the whole process easily causes the per-anvil reduction amount to be too small (insufficient forging penetration) or too large and the rate to be too large (local deformation zone) in the elongation process, so that the homogenization and fine-grain refinement of the large-size billet are difficult to increase.

[0008] Therefore, the technical scheme adopted by the present application is:

[0009] A forging method of a super large size TC32 titanium alloy forging blank, the raw material of the super large size TC32 titanium alloy forging blank is a 3-10 ton class ingot; characterized in that the method comprises the following steps:

[0010] Step 1, the size design of the starting forging ingot or blank, the ingot is made into a height H, and the maximum diagonal length D 始max , and the starting blank satisfies 1.0≤H / D 始max ≤2.5, and the blank is heated and kept;

[0011] Step 2, the upsetting deformation of the starting blank, the upsetting deformation amount ε: 15%≤ε≤50%, the upsetting stroke per hammer: h 始 =(0.01-0.3)×D 始max , the stroke speed V 始 : 10mm / s≤V 始 ≤50mm / s;

[0012] Step 3, the first stage of elongation of the blank deformed in step 2, the blank is finally a square cross section, D 四方max =(n1+upsetting deformation amount ε)×D 始max , wherein the deformation coefficient n1: 0.5≤n1≤1.2, the stroke per hammer h1=(0.01-0.3)×D 始max , the stroke speed V1: 10mm / s≤V1≤35mm / s;

[0013] Step 4, the second stage of elongation, the blank is finally an octagonal cross section, D 八方max =n2×D 四方max , wherein the deformation coefficient n2: 0.3≤n2≤1.0, the stroke per hammer h2=(0.01-0.3)×D 四方max , the stroke speed V2: 5mm / s≤V2≤30mm / s.

[0014] In steps 2-4, the blank is pressed by the upper anvil in a uniform speed.

[0015] When the blank heating temperature T is 1000℃≤T≤1200℃ in step 1, the forging deformation of steps 2-4 can be repeated for 2 or 3 times.

[0016] When the blank heating temperature T is 950℃≤T<1000℃ in step 1, the forging deformation of steps 2-4 can be repeated for 1 or 2 times.

[0017] When the blank heating temperature T is 840℃≤T<950℃ in step 1, the forging deformation of steps 2-4 is 1 time.

[0018] In steps 2 to 4, when the forging deformation is completed, the final forging temperature of the billet is ≥760℃.

[0019] When the billet has completed upsetting and drawing deformation and is finally formed into a large-sized square billet, the forging drawing and widening process is preferably carried out in step 3.

[0020] When the billet has completed upsetting and drawing deformation and is finally formed into a large-size bar, the forging and drawing process preferably adopts step 4.

[0021] In steps 2 through 4, the upper hammer anvil always prioritizes pressing the position corresponding to the billet cross section Dmax.

[0022] The ingot is smelted in a vacuum arc furnace. The chemical composition of the ingot by weight percentage is as follows: Al 4.5%–5.5%, Mo 2.5%–3.5%, Cr 2.5%–3.5%, Zr 0.5%–1.5%, Si 0.1%–0.2%, Fe ≤0.3%, C ≤0.08%, N ≤0.05%, H ≤0.0125%, O ≤0.2%, and the balance is Ti.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] Based on the deformation characteristics of the free forging method, this invention proposes a maximum diagonal length D for large-size billets. max And by closely combining this parameter with the actual process parameters, it has the following advantages: (1) the ingot or billet satisfies 1.0≤H(L) / D 始max ≤2.5 range, and h 始 = (0.01~0.3)×D 始max When upsetting at a uniform speed within the hot working temperature range of 840℃~1200℃, the bulging deformation in the middle of the large-size TC32 titanium alloy ingot or billet is uniform, and the deformation dead zone range at the upper and lower ends of the billet is small; (2) In the first and second stages of drawing, this invention takes into account that the billet diameter after upsetting is closely related to the upsetting deformation amount, and thus introduces this process variable in the first stage to determine the optimal D for this stage. max As analyzed above, the amount of pressure applied per hammer during the pull-out process is related to D. max The two-stage hammer reduction is also given specific process specifications, which significantly improve the forging penetration and uniformity of the large-size billet drawing stage of TC32 titanium alloy within the corresponding range; (3) Compared with the existing process, by proposing the maximum diagonal length D max This invention decomposes the upsetting and drawing stages of large-size ingots or billets. Through reasonable process settings, it achieves precise control of the entire forging process, improves the stability and consistency of forging processes in different batches, and thus improves batch stability. DETAILED DESCRIPTION

[0025] Chinese material brand TC32 (α+β) type two-phase titanium alloy, the chemical composition meets the requirements of "Titanium and Titanium Alloy Brand and Chemical Composition (GB / T 3620.1-2016)", the main chemical element content (wt%) is: Al content 4.5%~5.5%, Mo content 2.5%~3.5%, Cr content 2.5%~3.5%, Zr content 0.5%~1.5%, Si content 0.1%~0.2%, Fe content ≤0.3%, C content ≤0.08%, N content ≤0.05%, H content ≤0.0125%, O content ≤0.2%, the balance is Ti.

[0026] Example 1: TC32 titanium alloy ingot forging breakdown, ingot specification: Φ750x1600mm, single weight 3.2t, heating temperature 1150℃.

[0027] First pass upsetting and elongation forging:

[0028] Upsetting deformation, upsetting deformation amount ε: 45.5%, upsetting per hammer reduction amount: h 始 =150mm, reduction speed V 始 : 45mm / s, uniform speed pressing;

[0029] Elongation stage I, per hammer reduction amount h1=90mm, reduction speed V1: 35mm / s, uniform speed pressing, the final blank is a square section, D 四方max =962mm;

[0030] Elongation stage II, per hammer reduction amount h2=77mm, reduction speed V2: 25mm / s, uniform speed pressing, the final blank is a square section, D 八方max =786mm;

[0031] Second pass upsetting and elongation forging:

[0032] Upsetting deformation, upsetting deformation amount ε: 42%, upsetting per hammer reduction amount: h 始 =130mm, reduction speed V 始 : 40mm / s, uniform speed pressing;

[0033] Elongation stage I, per hammer reduction amount h1=80mm, reduction speed V1: 33mm / s, uniform speed pressing, the final blank is a square section, D 四方max =962mm;

[0034] Elongation stage II, per hammer reduction amount h2=70mm, reduction speed V2: 25mm / s, uniform speed pressing, the final blank is a square section, D 八方max= 786 mm;

[0035] First upsetting and drawing forging:

[0036] Upsetting deformation, upsetting deformation ε: 38%, upsetting per stroke h 始 = 120 mm, pressing speed V 始 : 40 mm / s, uniform speed;

[0037] First stage of drawing, per stroke h1 = 80 mm, pressing speed V1: 33 mm / s, uniform speed, the final blank is a square section, D 四方max = 962 mm;

[0038] Second stage of drawing, per stroke h2 = 70 mm, pressing speed V2: 25 mm / s, uniform speed, the final blank is a square section, D 八方max = 786 mm.

[0039] High and low magnification corrosion detection was performed on the blank, the overall blank was clear equiaxed grains, the structure was uniform, the grain size was between 10-15 mm, there was no coarse casting structure, and the refinement was obvious.

[0040] Example 2: TC32 titanium alloy blank cogging forging, blank specification: square section, D max = 773 mm, length 1600 mm, single weight 3 t, heating temperature 970 °C.

[0041] First upsetting and drawing forging:

[0042] Upsetting deformation, upsetting deformation ε: 47%, upsetting per stroke h 始 = 140 mm, pressing speed V 始 : 48 mm / s, uniform speed;

[0043] First stage of drawing, per stroke h1 = 85 mm, pressing speed V1: 38 mm / s, uniform speed, the final blank is a square section (650x700 mm), D 四方max = 955 mm;

[0044] Second stage of drawing, per stroke h2 = 75 mm, pressing speed V2: 30 mm / s, uniform speed, the final blank is a square section, D 八方max = 773 mm;

[0045] Second upsetting and drawing forging:

[0046] Upsetting deformation, upsetting deformation ε: 41%, upsetting per stroke h 始 = 140 mm, pressing speed V 始: 47 mm / s, uniform speed;

[0047] Stretching the first phase, each hammer h1 = 80 mm, the pressure V1: 38 mm / s, uniform speed, the final blank four square cross-section (650 x 700 mm), D 四方max = 955 mm;

[0048] Stretching the second phase, each hammer h2 = 70 mm, the pressure V2: 30 mm / s, uniform speed, the final blank octagonal cross-section, D 八方max = 773 mm;

[0049] The blank is subjected to high and low corrosion detection, the overall blank is clear equiaxed grain, uniform structure, grain size 8-12 mm, compared with the previous fire, obvious refinement.

[0050] Example 3: TC32 titanium alloy blank homogenization forging, blank specification: square cross-section, D max = 778 mm, length 1200 mm, single weight 1.6 t, heating temperature 870 °C.

[0051] The first week of upsetting and stretching forging:

[0052] Upsetting deformation, upsetting deformation ε: 45%, each hammer h 始 = 120 mm, the pressure V 始 : 55 mm / s, uniform speed;

[0053] Stretching the first phase, each hammer h1 = 60 mm, the pressure V1: 28 mm / s, uniform speed, the final blank is a square cross-section, D 四方max = 820 mm;

[0054] Stretching the second phase, each hammer h2 = 40 mm, the pressure V2: 15 mm / s, uniform speed, the final blank is a square cross-section, D 八方max = 655 mm;

[0055] Continuous hot material recycling (1 fire), heating temperature 870 °C.

[0056] The second week of upsetting and stretching forging:

[0057] Upsetting deformation, upsetting deformation ε: 45%, each hammer h 始 = 120 mm, the pressure V 始 : 55 mm / s, uniform speed;

[0058] Stretching the first phase, each hammer h1 = 50 mm, the pressure V1: 25 mm / s, uniform speed, the final blank is a square cross-section, D四方max = 820 mm;

[0059] The second stage of drawing, h2 = 30 mm per hammer, V2: 15 mm / s, uniform speed, the final blank is a regular octagonal section, D 八方max = 655 mm;

[0060] The high and low magnification corrosion detection is performed on the blank, the overall blank is clear and fuzzy grain, the structure is uniform, and the lamellar alpha phase in the core, middle and edge is dynamically spheroidized without large alpha clusters.

[0061] Example 4: TC32 titanium alloy blank forming forging, blank specification: regular square section, D max = 733 mm, length 1200 mm, single weight 2 t, heating temperature 880 °C.

[0062] The first cycle of upsetting and drawing forging:

[0063] Upsetting deformation, upsetting deformation ε: 23%, h 始 = 120 mm per hammer, V 始 : 48 mm / s, uniform speed;

[0064] The first stage of drawing, h1 = 40 mm per hammer, V1: 35 mm / s, uniform speed, the final blank is a regular square section, D 四方max = 777 mm;

[0065] The second stage of drawing, h2 = 16 mm per hammer, V2: 12 mm / s, uniform speed, the final blank is a regular octagonal section, D 八方max = 629 mm;

[0066] Continuous hot material recycling (2-3 times), heating temperature 870 °C, continue the second stage of drawing forging of the blank.

[0067] h2 = 12 mm per hammer, V2: 10 mm / s, uniform speed, the final blank is a regular octagonal section, D 八方max = 419 mm, and the blank is straightened and rounded to obtain a Φ400 x L mm finished rod;

[0068] The finished rod is subjected to ultrasonic flaw detection, which meets the standard requirements. The physical and chemical materials are subjected to mechanical property testing after 880 °C / 2 h, AC + 550 °C / 6 h, AC heat treatment, the high and low magnification structure is uniform, and the mechanical property difference is small, and the results are shown in Table 1.

[0069] Table 1 Mechanical properties of TC32 titanium alloy Φ400 x L mm finished rod

[0070]

Claims

1. A forging method for an ultra-large TC32 titanium alloy forging billet, wherein the raw material for the ultra-large TC32 titanium alloy forging billet is a 3-10 ton ingot; characterized in that, The method includes the following steps: Step 1: Design the initial forging ingot or billet dimensions, shaping the ingot to a height H and a maximum diagonal length D. 始max And satisfy 1.0≤H / D 始max The initial forging billet is ≤2.5 mm thick, and the billet is heated and held at that temperature. Step 2: Upset the initial forging billet. Upsetting deformation ε: 15% ≤ ε ≤ 50%. Downsizing per hammer blow: h 始 =(0.01~0.3)×D 始max Pressing speed V 始 10mm / s≤V 始 ≤50mm / s; Step 3: The billet deformed in Step 2 is drawn out in the first stage. The final billet has a square cross-section, D. 四方max = (n1 + upsetting deformation ε) × D 始max Where the deformation coefficient n1 is 0.5 ≤ n1 ≤ 1.2, and the amount of pressure applied per hammer blow is h1 = (0.01 ~ 0.3) × D 始max Pressing speed V1: 10mm / s≤V1≤35mm / s; Step 4, the second stage of drawing, the billet finally has an octagonal cross section, D 八方max =n2×D 四方max Where the deformation coefficient n2 is 0.3≤n2≤1.0, and the amount of pressure applied per hammer blow h2=(0.01~0.3)×D 四方max Pressing speed V2: 5mm / s≤V2≤30mm / s.

2. The forging method for an ultra-large TC32 titanium alloy forging billet according to claim 1, characterized in that, In steps 2 to 4, the billet is pressed down at a uniform speed using the upper hammer anvil.

3. The forging method for an ultra-large TC32 titanium alloy forging billet according to claim 1, characterized in that, When the billet heating temperature T is between 1000℃ and 1200℃, repeat steps 2 to 4 forging deformation 2 or 3 times.

4. The forging method for an ultra-large TC32 titanium alloy forging billet according to claim 1, characterized in that, When the billet heating temperature T is between 950℃ and 1000℃, repeat steps 2 to 4 forging deformation once or twice.

5. The forging method for an ultra-large TC32 titanium alloy forging billet according to claim 1, characterized in that, In step 1, when the billet heating temperature T is between 840℃ and 950℃, the forging deformation is carried out once according to steps 2 to 4.

6. The forging method for an ultra-large TC32 titanium alloy forging billet according to claim 1, characterized in that, In steps 2 to 4, when the forging deformation is completed, the final forging temperature of the billet is ≥760℃.

7. The forging method for an ultra-large TC32 titanium alloy forging billet according to claim 1, characterized in that, When the billet has completed upsetting and drawing deformation and is finally formed into a large-sized square billet, the forging drawing and widening process is carried out in step 3.

8. The forging method for an ultra-large TC32 titanium alloy forging billet according to claim 1, characterized in that, When the billet has completed upsetting and drawing deformation and is finally formed into a large-size bar, the forging and drawing process is carried out in step 4.

9. The forging method for an ultra-large TC32 titanium alloy forging billet according to claim 1, characterized in that, In steps 2 through 4, the upper hammer anvil always prioritizes pressing the position corresponding to the billet cross section Dmax.

10. A forging method for an ultra-large TC32 titanium alloy forging billet according to claim 1, characterized in that, The ingot is smelted in a vacuum arc furnace. The chemical composition of the ingot by weight percentage is as follows: Al 4.5%~5.5%, Mo 2.5%~3.5%, Cr 2.5%~3.5%, Zr 0.5%~1.5%, Si 0.1%~0.2%, Fe ≤0.3%, C ≤0.08%, N ≤0.05%, H ≤0.0125%, O ≤0.2%, and the balance is Ti.

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