Multifunctional isothermal forming performance test method for high temperature titanium alloy

Abstract

The present invention belongs to the technical field of plastic forming processing, and proposes a multifunctional isothermal forming performance testing method for high-temperature titanium alloys. The bending, flanging, and sinking features of sheet metal parts are integrated into a structural part for isothermal forming. Through the use of this structural part, the formability of different sheet metal features of different high-temperature titanium alloy materials can be judged. The drawbacks of the original process forming verification process of new high-temperature titanium alloy materials are avoided, and a technical basis is provided for the subsequent application of high-temperature titanium alloys in new models. Through the present invention, experiments can be carried out in advance to verify the process formability of new materials. It is estimated that the entire design and manufacturing cycle can be shortened by at least 50%, thereby improving production efficiency; the formability of high-temperature titanium alloys can be obtained before formal production, avoiding the "trial and error" exploration of process performance by using designed parts, saving materials; and it can be applied to any newly developed titanium alloy material for sheet metal formability verification.

Description

Technical Field

[0001] The invention relates to the technical field of plastic forming processing, and in particular to a multifunctional isothermal forming performance testing method for high-temperature titanium alloys. Background Art

[0002] As the requirements for high temperature resistance of new aircraft are getting higher and higher, the requirements for the material performance of aviation parts are also getting higher and higher. At present, new high-temperature titanium alloy materials TA32 and Ti65 have been used in new aircraft. TA32 is a kind of high-temperature titanium alloy with a long-term use temperature of 550℃, and its performance meets the requirements of future new aircraft. The material has been developed maturely, has stable performance, and is in sufficient supply. It has been used in other fields. Overcoming the technical difficulties of hot forming of this type of titanium alloy is the basis for this type of titanium alloy to move towards large-scale engineering applications. Ti65 is a T1-Al-Sn-Zr-Mo-Si-Nb-Ta-WC near-α-type high-temperature titanium alloy with a long-term use temperature of 650℃ and a use temperature of 650℃-750℃ under short-term high stress conditions. The alloy adopts the traditional smelting-hot processing-heat treatment process route, and has completed laboratory stage research, industrial production trial production and typical parts trial production, and has achieved research results that are higher than expected. Ti65 high-temperature titanium alloy material technology has matured, but there is a lack of relevant manufacturing standards in the aviation field.

[0003] For the process testing of new machine models and new material parts, trial production is usually carried out directly with the designed parts according to past experience. If the test piece is qualified, production can be carried out according to the original plan; if the test piece is not qualified, the part needs to be redesigned and changed, and this "failure" experience is only for this part or parts with similar structures to this part, and cannot be applied to parts with different structures.

[0004] Therefore, in order to smoothly apply TA32 and Ti65 in new aircraft models, a multifunctional isothermal forming performance test method for high-temperature titanium alloys was invented. By testing the forming quality of structural parts tested by this method, the sheet metal formability of high-temperature titanium alloy materials can be determined, so that feasibility suggestions can be given on the forming process at the beginning of aircraft part design, avoiding the waste of time and cost caused by multiple changes in design and manufacturing plans due to the inability to form parts. Summary of the invention

[0005] In view of the above shortcomings, a multifunctional isothermal forming performance test method for high-temperature titanium alloy is proposed. That is, multiple features of sheet metal parts such as bending, flanging, and sinking are integrated into a structural part for isothermal forming. Through the use of this structural part, the formability of different sheet metal features of different high-temperature titanium alloy materials can be judged. Avoid the drawbacks of the original new high-temperature titanium alloy material process forming verification process, and provide a technical basis for the subsequent application of high-temperature titanium alloys in new models.

[0006] The technical solution of the present invention is as follows: a multifunctional isothermal forming performance testing method for high-temperature titanium alloy, by integrating bending, flanging, and sinking features into a structural part, and isothermally forming in sequence to obtain formability with different characteristics; the specific steps are as follows:

[0007] 1) Construct structural parts, which are designed as box-shaped parts;

[0008] 1.1) Determine the thickness t of the structural part according to the use of high-temperature titanium alloy materials;

[0009] 1.2) Design the bending structure 01; two bending structures 01 are respectively set on the two short sides of the structural member, and the two bending structures 01 are separated by a rectangular hole. The bending radii of the four bending structures 01 are respectively set to 1.67t, 2t, 3t and 4t, and the bending angles are all 90 degrees;

[0010] 1.3) Design a sunken structure 02; the sunken type is side sunken; two sunken structures 02 are respectively set on the two long sides of the structural member, and the two sunken structures 02 are separated by a rectangular hole; the sunken heights of the four sunken structures 02 are the same as the bending radius, and the transition zone lengths are different; the bending radius is set to 3t; the theoretical value of the transition zone length is 1mm according to the thickness of the structural member; the transition zone lengths of the four sunken structures 02 are 1-5mm, 1mm, 1+2mm, and 1+4mm respectively;

[0011] 1.4) Design of flange structure 03: Three flange structures 03 are set on the web surface of the structural member, the diameter of the flange rear hole is 100mm, the flange height is 7mm, the flange bending radius is 7mm, and the flange coefficients are 0.8, 0.9, and 1.0 respectively; the center distances of adjacent flange structures 03 are 150mm and 160mm respectively;

[0012] 1.5) The four corners of the box-shaped member are provided with cutouts to separate the sunken structure 02 from the curved structure 01;

[0013] 2) Conduct isothermal forming tests on structural parts;

[0014] 2.1) Conduct high temperature tensile tests on high temperature titanium alloy materials to obtain simulation data, isothermal hot forming process parameters and thermal expansion coefficient of high temperature titanium alloy materials;

[0015] 2.2) Design a high-temperature titanium alloy sheet metal forming performance verification mold according to the characteristics of the structural parts, including an upper mold 04 and a lower mold 05. The upper mold 04 and the lower mold 05 are provided with pressure plate grooves on the left and right sides for connecting with the equipment, and the side is provided with a temperature measuring hole 06 and a lifting ring 07;

[0016] 2.3) Simulate the isothermal hot forming process of the structural parts to obtain the sheet metal forming quality; the sheet metal forming simulation results meet the inspection requirements, and the mold design is carried out; the mold surface is optimized to meet the requirements according to the forming effect; the simulation results also provide the optimized forming pressure;

[0017] 2.4) Determine the final mold size at room temperature based on the mold's thermal expansion coefficient;

[0018] Calculation formula: Lcm=Lcj(1+αj△t) / (1+αm△t)

[0019] Where, Lcm is the mold surface size at room temperature, Lcj is the required size of the part at room temperature, △t is the difference between the forming temperature and room temperature, αj is the high-temperature thermal expansion coefficient of the part material, and αm is the high-temperature thermal expansion coefficient of the mold material;

[0020] 2.5) Forming of test pieces;

[0021] 2.6) Check the forming state of the test piece and perform fluorescent penetrant testing to check whether the parts have microcracks;

[0022] 2.7) Based on the inspection results, the forming limits of the three sheet metal forming features of the new material, namely bending, flanging and sinking, can be determined.

[0023] When the thickness of the structural part is 1.4-1.8mm, the theoretical value of the transition zone length is l=16mm; when the thickness of the structural part is 2.0mm, the theoretical value of the transition zone length is l=17mm; when the thickness of the structural part is 2.5mm, the theoretical value of the transition zone length is l=18mm; when the thickness of the structural part is 3.0mm, the theoretical value of the transition zone length is l=19mm; when the thickness of the structural part is 4.0mm, the theoretical value of the transition zone length is l=20mm.

[0024] Beneficial effects of the present invention:

[0025] (1) Shortened cycle: The process formability of new materials can be verified in advance. This can provide support for the design of new models at the beginning, and the design and manufacturing cycle is reduced. It is estimated that the entire design and manufacturing cycle can be shortened by at least 50%, thereby improving production efficiency.

[0026] (2) Cost reduction: By using the hot forming verification structural parts of the present invention, the forming performance of high-temperature titanium alloy can be obtained before formal production, avoiding the "trial and error" exploration of process performance by using designed parts, which leads to tooling scrapping and rework; at the same time, the utilization rate of materials and energy is improved, and manpower and material resources are reduced accordingly. The use of each new titanium alloy material can save at least 1 million yuan;

[0027] (3) Diverse functions: The present invention integrates the typical features of titanium alloy sheet metal parts. The formability of three features can be determined through one-time forming, and can be applied to any newly developed titanium alloy material for sheet metal formability verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of structural parts for verifying the sheet metal forming performance of high-temperature titanium alloy materials.

[0029] Figure 2 Schematic diagram of the forming die for verifying the sheet metal forming performance of high-temperature titanium alloy materials. (a) is the schematic diagram of the upper die; (b) is the schematic diagram of the lower die.

[0030] Among them: 01-bending structure; 02-sunken structure; 03-flanging structure; 04-upper die; 05-lower die; 06-temperature measuring hole; 07-lifting ring. DETAILED DESCRIPTION

[0031] 1. Structural parts,

[0032] 1.1 Determination of the thickness of structural parts

[0033] According to the use of high-temperature titanium alloy materials in new aircraft, the thickness of this structural part is determined to be 1.5mm.

[0034] 1.2. Design of curved structure 01

[0035] This structural component is designed with four bending radii, namely R2.5, R3, R4.5, and R6, with the unit being mm, and the bending angles are all 90°.

[0036] 1.3 Design of the sunken structure 01

[0037] The sinking type of this structure is side sinking, marked as 1S300-2-6C-1.5, that is, the material thickness is 1.5mm, the sinking height is 6mm, and the bending radius is R4.5mm; the lengths of the 4 sinking transition zones are 11mm, 16mm, 18mm, and 20mm respectively.

[0038] 1.4. Design of flange structure 03:

[0039] This structure is designed with three flanging structures 03, the flange bending radius is 7mm, the flange height is 7mm, the diameter of the hole after the flanging is 100mm, and the three flanging coefficients are determined to be 0.8, 0.9, and 1.0 respectively. The center distances of the three flanging structures 03 are 150mm and 160mm.

[0040] 1.5. Overall design of structural parts

[0041] The overall design of this structural member is a box-shaped member with a length of 600mm, a width of 200mm, and a height of 20mm. 100mm×40mm openings are designed at the four corners of the box-shaped member to separate the sinking structure 02 and the bending structure 01 to prevent the two parts from affecting each other. The two sides of the short side are designed as bending performance verification structures, and a 60mm×20mm rectangular hole is opened in the middle of each short side. The two sides of the long side are designed as sinking performance verification structures, and a 60mm×20mm rectangular hole is opened in the middle of each long side. Three flange structures are designed on the web surface of the box-shaped member, and the distance between the flange structure 03 and the edge is 110mm and 140mm respectively. This distance ensures that the flange structure 03 and the sinking structure 02 and the bending structure 01 will not affect each other when the structural member is in use.

[0042] 2. Usage

[0043] 2.1. Conduct high temperature tensile tests on new titanium alloy materials to obtain material simulation data, isothermal hot forming process parameters and thermal expansion coefficient of the material;

[0044] 2.2. Design a set of titanium alloy sheet metal forming performance verification forming die structure based on the structural part, such as Figure 2 As shown, the mold includes an upper mold 04 and a lower mold 05. Press plate grooves are set on the left and right sides of the upper mold 04 and the lower mold 05 for connecting with the equipment, and temperature measuring holes 06 and lifting rings 07 are set on the sides.

[0045] 2.3. Use simulation software to simulate the isothermal hot forming process of the designed sheet metal structural parts to predict the sheet metal forming quality; if the sheet metal forming simulation results meet the inspection requirements, then carry out detailed mold design; if the forming effect is not good, then optimize the mold profile until the profile is reasonable. The simulation results also provide optimized forming pressure.

[0046] 2.4. According to the thermal expansion coefficient of the selected mold material, determine the final mold size at room temperature, that is, after scaling. Calculation formula: Lcm = Lcj (1 + αj△t) / (1 + αm△t), where Lcm is the mold surface size at room temperature, Lcj is the required size of the part at room temperature, △t is the difference between the forming temperature and room temperature, αj is the high-temperature thermal expansion coefficient of the part material, and αm is the high-temperature thermal expansion coefficient of the mold material. The mold material is cast and processed with XZ19-4N alloy steel with good casting performance.

[0047] 2.5. Forming of test piece.

[0048] 2.5.1. After checking the material grade, thickness and surface condition, cut the material and grind the edge of the sheet to remove burrs. The surface roughness should be Ra6.3.

[0049] 2.5.2. Remove marks and oil stains from the sheet in an organic solvent, clean the isothermal hot forming mold, and evenly apply lubricant graphite on the sheet and mold surface;

[0050] 2.5.3 Use a crane to place the mold into the thermoforming machine through the lifting ring 07. The upper platform of the thermoforming machine is connected and fixed to the pressing plate groove of the upper mold 04. The lower platform of the thermoforming machine is connected and fixed to the pressing plate groove of the lower mold 05. Temperature measuring holes with a diameter of 10 mm are installed on both sides of the upper mold 04 and the lower mold 05 respectively.

[0051] 2.5.4 Heat the mold at 75℃ / h and stabilize it at the forming temperature, put the sheet into the mold and preheat it to the forming temperature, and close the mold to form the part. The forming process parameters of each new material are determined based on the high-temperature tensile test. The following are the isothermal forming process parameters of TA32: forming temperature: 775℃, preheating time: 10-15 minutes, mold closing pressure: 500KN, holding time: 15-20 minutes; demold the part and place it on an asbestos pad to cool;

[0052] 2.5.5 After the parts are formed, they are subjected to processes such as contour making, hole milling, and pickling.

[0053] 2.6. Check the forming state of the test piece and conduct fluorescent penetrant testing to check whether there are micro cracks on the parts;

[0054] 2.7. Based on the inspection results, the forming limits of the three sheet metal forming characteristics of the new material, namely bending, flanging and sinking, can be determined.

Claims

1. A multifunctional isothermal forming performance testing method for high-temperature titanium alloy, characterized in that the multifunctional isothermal forming performance testing method for high-temperature titanium alloy integrates bending, flanging, and sinking features into a structural part, and sequentially performs isothermal forming to obtain formability with different features; the specific steps are as follows: 1) Construct structural parts, which are designed as box-shaped parts; 1.1) Determine the thickness t of the structural part according to the use of high-temperature titanium alloy materials; 1.2) Designing a bending structure (01); two bending structures (01) are respectively arranged on the two short sides of the structural member, and the two bending structures (01) are separated by a rectangular hole. The bending radii of the four bending structures (01) are respectively set to 1.67t, 2t, 3t and 4t, and the bending angles are all 90 degrees; 1.3) Design a sunken structure (02); the sunken type is side sunken; two sunken structures (02) are respectively arranged on the two long sides of the structural member, and the two sunken structures (02) are separated by a rectangular hole; the sunken heights of the four sunken structures (02) are the same as the bending radius, and the transition zone lengths are different; the bending radius is set to 3t; the theoretical value of the transition zone length is 1mm according to the thickness of the structural member; the transition zone lengths of the four sunken structures (02) are 1-5mm, 1mm, 1+2mm, and 1+4mm respectively; 1.4) Design of flange structure (03): Three flange structures (03) are set on the web surface of the structural member, the diameter of the flange rear hole is 100mm, the flange height is 7mm, the flange bending radius is 7mm, and the flange coefficients are 0.8, 0.9, and 1.0 respectively; the center distances of adjacent flange structures (03) are 150mm and 160mm respectively; 1.5) The four corners of the box-shaped member are provided with cutouts for separating the sunken structure (02) from the curved structure (01); 2) Conduct isothermal forming tests on structural parts; 2.1) Obtain simulation data, isothermal hot forming process parameters and thermal expansion coefficient of high temperature titanium alloy materials; 2.2) Designing a high-temperature titanium alloy sheet metal forming performance verification die according to the characteristics of the structural parts, including an upper die (04) and a lower die (05), with pressing plate grooves on the left and right sides of the upper die (04) and the lower die (05) for connection with the equipment, and temperature measuring holes (06) and lifting rings (07) on the sides; 2.3) Simulate the isothermal hot forming process of the structural parts to obtain the sheet metal forming quality; The sheet metal forming simulation results meet the inspection requirements, and the mold design is carried out; Optimize the mold surface to meet the requirements according to the forming effect; The simulation results also provide optimized forming pressure; 2.4) Determine the final mold size at room temperature based on the mold's thermal expansion coefficient; Calculation formula: Lcm=Lcj(1+αj△t) / (1+αm△t) Where, Lcm is the mold surface size at room temperature, Lcj is the required size of the part at room temperature, △t is the difference between the forming temperature and room temperature, αj is the high-temperature thermal expansion coefficient of the part material, and αm is the high-temperature thermal expansion coefficient of the mold material; 2.5) Forming of test pieces; 2.6) Check the forming state of the test piece and perform fluorescent penetrant testing to check whether the parts have microcracks.

2. The high temperature titanium alloy multifunctional isothermal forming performance testing method according to claim 1, characterized in that: When the thickness of the structural part is 1.4-1.8mm, the theoretical value of the transition zone length is l=16mm; when the thickness of the structural part is 2.0mm, the theoretical value of the transition zone length is l=17mm; when the thickness of the structural part is 2.5mm, the theoretical value of the transition zone length is l=18mm; when the thickness of the structural part is 3.0mm, the theoretical value of the transition zone length is l=19mm; when the thickness of the structural part is 4.0mm, the theoretical value of the transition zone length is l=20mm.

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