Manufacturing method of ultra-thin and ultra-wide TC18 titanium alloy structural member

Abstract

This invention discloses a method for manufacturing ultra-thin and ultra-wide TC18 titanium alloy structural components, comprising: performing vacuum induction melting to obtain a TC18 titanium alloy ingot; heating and holding the titanium alloy ingot at a temperature above its phase transformation point, and then forging it to obtain a TC18 titanium alloy forging billet; heating the titanium alloy forging billet and then performing a multi-stage plastic deformation process to obtain a TC18 titanium alloy intermediate square billet; rolling the titanium alloy intermediate square billet using a plate rolling mill to obtain a semi-finished TC18 titanium alloy structural component; and performing heat treatment and surface treatment on the semi-finished product to obtain the finished ultra-thin and ultra-wide TC18 titanium alloy structural component. This method can overcome the size limitations of TC18 titanium alloy and produce ultra-thin and ultra-wide structural components that meet the requirements of aerospace titanium applications.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal product preparation, specifically relating to a method for manufacturing ultra-thin and ultra-wide TC18 titanium alloy structural parts. Background Technology

[0002] TC18 titanium alloy is a high-strength, high-toughness titanium alloy developed by the Russian Academy of Aeronautical Materials in the 1960s. In its annealed state, this alloy contains approximately equal amounts of α and β phases, making it the strongest titanium alloy in the annealed state. Because its strength is comparable to that of high-strength steel 30CrMnSiA, and it possesses good plasticity, toughness, and weldability, it is widely used in aerospace, weaponry, and petroleum industries. Replacing high-strength steel with TC18 titanium alloy in the manufacture of load-bearing structural components can reduce aircraft weight by more than 20%. Furthermore, its high hardenability allows it to be used to produce large-section structural components with high load-bearing capacity, a feat difficult to achieve with existing manufacturing methods for ultra-thin and ultra-wide large-section structural components. Summary of the Invention

[0003] To address the aforementioned problems in the existing technology, this invention provides a method for manufacturing ultra-thin and ultra-wide TC18 titanium alloy structural components. The technical problem to be solved by this invention is achieved through the following technical solution:

[0004] A method for manufacturing ultra-thin and ultra-wide TC18 titanium alloy structural components includes:

[0005] Step 1: Vacuum induction melting is carried out using a vacuum self-consuming electric arc furnace to obtain TC18 titanium alloy ingots, and the diameter of the titanium alloy ingots is ≥800mm and the weight is ≥6 tons.

[0006] Step 2: After heating and holding the TC18 titanium alloy ingot at a certain temperature, forge it above the phase transformation point to obtain a TC18 titanium alloy forging billet.

[0007] Step 3: After heating the TC18 titanium alloy forging billet, a multi-heat large plastic deformation process is adopted, and at the same time, a forging method with small feed and wide transverse expansion is used to prepare a TC18 titanium alloy intermediate square billet with a thickness of 200-260mm and a width of ≥2380mm.

[0008] Step 4: Apply a heat-insulating coating to the surface of the TC18 titanium alloy intermediate square billet, then heat the TC18 titanium alloy intermediate square billet and roll it using a plate rolling mill to obtain an ultra-thin and ultra-wide TC18 titanium alloy structural component semi-finished product with a thickness of 130mm, a width of 2315mm, and a length of 2400mm; wherein, the heating temperature is β+(10~40)℃, the total deformation is 10~40%, the final rolling temperature is not lower than 720℃, and the entire deformation process is completed within 4 minutes;

[0009] Step 5: The ultra-thin and ultra-wide TC18 titanium alloy structural component semi-finished product is heat-treated and then surface-treated to obtain the finished product. The finished product has a thickness of 120mm, a width of 2300mm, and a length of 2300mm.

[0010] Furthermore, in step 1, the melting current of the vacuum induction melting is 22-28kA, the melting voltage is 30-40V, and the vacuum degree of the melting chamber is ≤5Pa.

[0011] Furthermore, the heating temperature for the initial forging is 1100–1180℃, the holding time is 240–480 min, the deformation amount is 50–75%, the deformation speed is less than 20 mm / s, and the final forging temperature is not lower than 900℃.

[0012] Further, in step 3, the titanium alloy forging billet is heated to (β-60)~1080℃ and held for 240~700min, and then subjected to multiple intermediate free forging to obtain the TC18 titanium alloy intermediate square billet; wherein, during the multiple intermediate free forging process, the deformation amount is 30~65%, the deformation speed is less than 15mm / s, and the final forging temperature is not lower than 700℃; during the last forging, the deformation amount is 20~50%, the deformation speed is less than 15mm / s, and the final forging temperature is not lower than 700℃.

[0013] Furthermore, before step 4, the upper and lower large surfaces of the TC18 titanium alloy intermediate square billet are milled. After milling, the titanium alloy intermediate square billet is subjected to ultrasonic testing, and the β phase transformation point temperature, mechanical properties and high and low magnification microstructure are detected. After all the test results meet the process requirements, step 4 is then performed.

[0014] Furthermore, the rolling process in step 4 is completed in four passes. The deformation amount in the first pass is 10-20%, the deformation amount in the second pass is 10-15%, the deformation amount in the third pass is 5-10%, and the deformation amount in the fourth pass is a shaping and leveling pass with a rolling reduction of less than 10 mm. The rolling process of the first three passes is completed within 2 minutes.

[0015] Further, the heat treatment in step 5 refers to: heating the ultra-thin and ultra-wide TC18 titanium alloy structural component semi-finished product to 820-850℃ and holding it at that temperature for 1-3 hours, then furnace cooling it to 740-760℃ and holding it at that temperature for 1-3 hours, then air cooling it to room temperature, then heating it to 500-650℃ and holding it at that temperature for 2-6 hours, and then air cooling it to room temperature.

[0016] The beneficial effects of this invention are:

[0017] The preparation method adopted in this invention, by controlling the process route of each step in the preparation of TC18 titanium alloy structural parts, ultimately breaks through the key technology for the preparation of ultra-thin and ultra-wide TC18 titanium alloy mesh basket structural parts, so that the external dimensions, high and low magnification microstructure, mechanical properties and flaw detection level of the developed TC18 titanium alloy structural parts can meet the titanium requirements of my country's aerospace industry.

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figures 1-2 This is a photograph of a semi-finished TC18 titanium alloy structural component obtained after rolling.

[0020] Figures 3-4 A photo of a finished TC18 titanium alloy structural component after heat treatment and surface treatment;

[0021] Figures 5-6 Metallographic image of the finished TC18 titanium alloy structural component;

[0022] Figures 7-10 The mechanical properties test results of the prepared ultra-wide and ultra-thin TC18 titanium alloy structural parts are shown. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0024] This invention provides a method for manufacturing ultra-thin and ultra-wide TC18 titanium alloy structural components, the method comprising the following steps:

[0025] Step 1: Using a dedicated intermediate alloy package, select high-grade sponge titanium with a particle size matching the intermediate alloy. Prepare TC18 alloy electrodes with uniform composition using a mixing and fabrication production line and a hydraulic press. Then, perform three vacuum induction melting processes using a vacuum self-consuming arc furnace to obtain TC18 titanium alloy black-skinned ingots. The diameter of the TC18 titanium alloy black-skinned ingots is 820 mm and the weight is 6.7 tons. The melting current of the vacuum induction melting is 22-28 kA, the melting voltage is 30-40 V, and the melting vacuum degree is ≤5 Pa.

[0026] Then, the oxide scale on the surface of the TC18 titanium alloy black-skinned ingot is removed by machining to obtain a TC18 titanium alloy ingot with a diameter of 796 mm and a weight of 6.4 tons. The TC18 titanium alloy ingot is then coated with an anti-oxidation coating TB1200-16 with a thickness of 0.3 to 0.5 mm.

[0027] Step 2: After heating and holding the above-mentioned TC18 titanium alloy ingot in a natural gas furnace, perform forging above the phase transformation point to obtain TC18 titanium alloy forging billet; specifically, the heating temperature of the forging is 1100~1180℃, the holding time is 240~480min, the deformation is 50~75%, the deformation speed is less than 20mm / s, and the final forging temperature is not lower than 900℃.

[0028] Step 3: Then, the TC18 titanium alloy forging billet is heated in a resistance furnace and subjected to a multi-heating, high-low-high, large plastic deformation process, while being combined with a small feed and transverse wide forging method to prepare a TC18 titanium alloy intermediate square billet with a thickness of 200-260mm and a width of ≥2380mm.

[0029] Specifically, the TC18 titanium alloy forging billet is heated to 809–1080℃ and held for 240–700 min. Then, a multi-stage intermediate free forging process is performed through upsetting, reversing upsetting, square opening and widening, and transverse widening to refine the billet grains and improve the uniformity of the forging structure, ultimately producing a TC18 titanium alloy intermediate square billet with a thickness of 200–260 mm and a width ≥2380 mm. During the multi-stage intermediate free forging process, the deformation is 30–65%, the deformation rate is less than 15 mm / s, and the final forging temperature is not lower than 700℃. During the final forging, the deformation is 20–50%, the deformation rate is less than 15 mm / s, and the final forging temperature is not lower than 700℃. The entire free forging process adopts a forging method with small feed and wide transverse extension. The feed is controlled at 1 / 5 to 1 / 3 of the hammer width, and the reduction is controlled at 20 to 60 mm. The width of the forging is increased by transverse forging. Utilizing the pressure advantage of the 10,000-ton forging press and the forging mode, the TC18 titanium alloy forging billet is forged to a width of more than 2380 mm and a thickness of more than 200 to 260 mm through multiple forging processes, providing raw materials for the subsequent rolling of finished structural parts.

[0030] Due to the high deformation resistance and narrow processing range of TC18 titanium alloy, free forging billet forming is extremely difficult. In particular, in order to ensure the width and length of the final finished structural parts, the intermediate billet specifications need to be produced to (200~260mm)×(≥2380mm)×L. Throughout the billet forging process, the billet heating time, holding time, deformation amount and final forging temperature are strictly controlled to ensure that the intermediate billet obtains a two-phase processing structure, achieving an excellent match of strength-plasticity-toughness. At the same time, it can prevent grain growth, ensure the uniformity of billet structure, and ensure that the subsequent ultrasonic flaw detection level and performance test results meet the technical requirements.

[0031] Step 4: Mill the upper and lower large surfaces (i.e., the largest surface area) of the TC18 titanium alloy intermediate square billet using a milling machine. The milling amount on each side should be no less than 5mm to ensure that the upper and lower large surfaces are smooth and free of oxide scale residue, with a surface roughness of less than 3.2μm, in order to ensure the accuracy of ultrasonic testing. After milling, perform ultrasonic testing on the titanium alloy intermediate square billet. Then, cut a sample with a length of no less than 50mm from the end of the billet to test the β phase transformation temperature. Perform mechanical property, high-magnification microstructure, low-magnification microstructure, and low-magnification microstructure after air burning on the sample. After all test results meet the relevant process requirements and the β phase transformation temperature is obtained as 880℃, design the subsequent quasi-β firing process route based on the measured phase transformation temperature of the TC18 titanium alloy intermediate square billet.

[0032] Step 5: Coat the surface of the TC18 titanium alloy intermediate square billet with a lubricating and heat-insulating glass coating of grade BJD-2 produced by Beijing Tianlichuang Glass Technology Development Co., Ltd. Then, determine the heating temperature for the rolling passes based on the β phase transformation point of the TC18 titanium alloy intermediate square billet, and perform multi-pass rolling using a plate rolling mill to obtain an ultra-thin and ultra-wide TC18 titanium alloy structural component semi-finished product with a thickness of 130mm, a width of 2315mm, and a length of 2400mm. The entire deformation process is completed within 4 minutes, the heating temperature is 890~920℃, the total deformation is 10~40%, and the final rolling temperature is not lower than 720℃.

[0033] Specifically, the rolling process of this ultra-thin and ultra-wide TC18 titanium alloy structural component semi-finished product is completed in four passes. The deformation in the first pass is controlled between 10% and 20%, i.e., a rolling reduction of 20-30 mm; the deformation in the second pass is controlled between 10% and 15%, i.e., a rolling reduction of 15-25 mm; the deformation in the third pass is controlled between 5% and 10%, i.e., a rolling reduction of 10-20 mm; the final pass is a shaping and leveling pass, with a rolling reduction controlled below 10 mm. The first three passes are completed within 2 minutes, and the entire rolling process is completed within 4 minutes. Before heating, a heat-insulating coating is applied to the surface of the TC18 titanium alloy intermediate billet, which also serves as a lubricant during forming. A photograph of the TC18 titanium alloy structural component semi-finished product after hot rolling is shown below. Figures 1-2 As shown.

[0034] Step 6: The semi-finished ultra-thin and ultra-wide TC18 titanium alloy structural component is heat-treated and then subjected to conventional surface treatment to obtain the finished TC18 titanium alloy structural component. The finished product has dimensions of 120mm × 2300mm × 2300mm and a single weight of 2900Kg. Specifically, the semi-finished ultra-thin and ultra-wide TC18 titanium alloy structural component is heated to 820-850℃ and held for 1-3 hours, then furnace-cooled to 740-760℃ and held for 1-3 hours, then air-cooled to room temperature; then heated to 500-650℃ and held for 2-6 hours, then air-cooled to room temperature, and finally subjected to conventional surface treatment to obtain the finished TC18 titanium alloy structural component with a thickness of 120mm, a width of 2300mm, and a length of 2300mm. A photograph of the finished structural component is shown below. Figures 3-4 As shown.

[0035] The microstructure of the finished TC18 titanium alloy structural component is as follows: Figures 5-6 As shown in the figure, the microstructure of this structural component is a basket weave structure, which meets the relevant technical requirements.

[0036] The mechanical property test results and high / low magnification microstructure test results of the finished structural component are shown in [reference]. Figures 7-10 The test results show that the room temperature tensile, impact, hardness, fracture toughness and microstructure of the ultra-wide and ultra-thin TC18 titanium alloy structural parts prepared by the method of this embodiment all meet the technical standard requirements. The TC18 ultra-wide and ultra-thin structural parts prepared by this invention can meet the titanium needs of my country's aviation and aerospace industries.

[0037] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for manufacturing an ultra-thin, ultra-wide TC18 titanium alloy structural member, characterized in that, include: Step 1: Vacuum induction melting is performed using a vacuum self-consuming electric arc furnace to obtain TC18 titanium alloy ingots, wherein the diameter of the titanium alloy ingots is ≥800mm and the weight is ≥6 tons; the melting current of the vacuum induction melting is 22~28kA, the melting voltage is 30~40V, and the vacuum degree of the melting chamber is ≤5Pa; the heating temperature of the billet forging is 1100~1180℃, the holding time is 240~480min, the deformation is 50~75%, the deformation speed is less than 20mm / s, and the final forging temperature is not lower than 900℃; Step 2: After heating and holding the TC18 titanium alloy ingot at a certain temperature, forge it above the phase transformation point to obtain a TC18 titanium alloy forging billet. Step 3: After heating the TC18 titanium alloy forging billet, a multi-stage large plastic deformation process is adopted, combined with a small feed and transverse wide forging method, to prepare a TC18 titanium alloy intermediate square billet with a thickness of 200-260mm and a width ≥2380mm; the titanium alloy forging billet is heated to (β-60)-1080℃ and held for 240-700min, and then subjected to multi-stage intermediate free forging to obtain the TC18 titanium alloy intermediate square billet; wherein, during the multi-stage intermediate free forging process, the deformation amount is 30-65%, the deformation speed is less than 15mm / s, and the final forging temperature is not lower than 700℃; during the final forging, the deformation amount is 20-50%, the deformation speed is less than 15mm / s, and the final forging temperature is not lower than 700℃; Step 4: Mill the top and bottom surfaces of the TC18 titanium alloy intermediate square billet. After milling, perform ultrasonic testing on the billet and check the β-phase transformation temperature, mechanical properties, and microstructure at high and low magnification. Once all test results meet the process requirements, apply a thermal insulation coating to the surface of the TC18 titanium alloy intermediate square billet. Then, heat the billet and roll it using a plate rolling mill to obtain an ultra-thin and ultra-wide TC18 titanium alloy billet with a thickness of 130mm, a width of 2315mm, and a length of 2400mm. Semi-finished titanium alloy structural components; wherein the heating temperature is β+(10~40)℃, the total deformation is 10~40%, the final rolling temperature is not lower than 720℃, and the entire deformation process is completed within 4 minutes; the rolling process is completed in four passes, the first pass has a deformation of 10~20%, the second pass has a deformation of 10~15%, the third pass has a deformation of 5~10%, and the fourth pass is a shaping and leveling pass with a rolling reduction of less than 10mm, and the first three rolling processes are completed within 2 minutes; Step 5: The ultra-thin and ultra-wide TC18 titanium alloy structural component semi-finished product is subjected to heat treatment and surface treatment to obtain the finished product. The finished product has a thickness of 120mm, a width of 2300mm, and a length of 2300mm. The heat treatment refers to heating the ultra-thin and ultra-wide TC18 titanium alloy structural component semi-finished product to 820-850℃ and holding it at that temperature for 1-3 hours, then furnace cooling it to 740-760℃ and holding it at that temperature for 1-3 hours, then air cooling it to room temperature, then heating it to 500-650℃ and holding it at that temperature for 2-6 hours, and then air cooling it to room temperature.

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