Drawing-out forging method for improving structure uniformity of titanium alloy bar

Abstract

The invention belongs to the field of titanium alloy machining, and discloses a drawing-out forging method for improving the structure uniformity of a titanium alloy bar. According to the method, the titanium alloy bar with the diameter being 200-350 mm is prepared through a multi-heating-number diagonal drawing-out process route, alternate deformation of edges and faces of the blank is achieved in a diagonal drawing-out mode, parameters such as the deformation temperature, the deformation amount, the pressing speed and the rolling reduction in the forging process are reasonably designed, the performance consistency of all parts of the bar is remarkably improved, and the yield of the titanium alloy bar is improved. And the titanium alloy bar with excellent structure uniformity can be obtained.

Description

Technical Field

[0001] The invention belongs to the field of titanium alloy processing, and in particular relates to a drawing forging method for improving the uniformity of the titanium alloy bar structure. Background Art

[0002] Titanium alloy has many advantages such as high strength, low density, corrosion resistance, and excellent welding performance, making it an ideal material for aviation structural parts and engine parts. However, titanium alloy bars are prone to uneven organization during the drawing and forging process. Due to the uneven flow of metal during the drawing process, there may be differences in the degree of deformation between the core and edge of the bar, resulting in uneven organization. This uneven organization will affect the comprehensive properties of the bar, such as uneven distribution of strength and toughness. In addition, cracks are prone to occur on the surface of the bar during drawing and forging. This is because titanium alloy is sensitive to deformation speed and deformation temperature during the forging process, and its organizational state depends on thermal deformation behavior and heat treatment process. The deformation mode and heat treatment play a decisive role in organizational uniformity. These cracks will reduce the fatigue strength and corrosion resistance of the bar, posing a safety hazard to its application in key fields such as aerospace.

[0003] At present, for titanium alloy bars with a diameter of Φ200mm to Φ350mm, the four-way drawing method is usually used for drawing and forging. However, during the forging process, due to the thin edges and corners, the contact area with the air is large, and the temperature loss is fast, which can easily lead to uneven deformation, resulting in insufficient uniformity of the structure of the finished titanium alloy bars. Summary of the invention

[0004] In view of this, the purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art in preparing Φ200mm~Φ350mm titanium alloy bars, and to provide a stretch forging method for improving the uniformity of the titanium alloy bar structure. The method stretches the bar by diagonal stretching, thereby achieving alternating deformation of the edges and faces of the blank, and reasonably designs various parameters in the forging process, such as deformation temperature, deformation amount, pressing speed, pressing amount, etc., to significantly improve the performance consistency of various parts of the bar, so that a titanium alloy bar with excellent uniformity of structure can be obtained.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for improving the uniformity of titanium alloy rod structure, comprising the following steps:

[0007] S1: heating a titanium alloy billet of □400mm to □600mm in size to 30 to 80°C below the phase transition point and keeping the temperature constant;

[0008] S2: The blank obtained in step S1 is forged into a rod of Φ210 mm to Φ360 mm by diagonal drawing and forging for multiple times, the deformation amount of each time is 20% to 50%, the reduction amount in the drawing process is 15% to 25%, the pressing speed is 10 mm / s to 50 mm / s, and the feed amount is 140 mm to 350 mm;

[0009] S3: machining the bar obtained in step S2 into a finished titanium alloy bar of Φ200 mm to Φ350 mm.

[0010] Furthermore, in step S1, the insulation time is 3 hours to 6 hours.

[0011] Furthermore, in step S2, the number of firings is 2 to 6.

[0012] Further, for a titanium alloy billet with a size of □500 mm, step S2 specifically includes:

[0013] S2.1: The blank obtained in step S1 is diagonally stretched to a blank of □400mm, with a deformation amount of 36%, a pressing speed of 40mm / s, a pressing amount of 15% to 25%, and a feed amount of 250mm to 350mm;

[0014] S2.2: The □400mm billet obtained in step S2.1 is returned to the furnace and kept at 30-80°C for 1.5-3h below the phase transition point, and then diagonally stretched to □330mm billet, with a deformation of 32%, a pressing speed of 40mm / s, a reduction of 15%-25%, and a feed amount of 200mm-320mm;

[0015] S2.3: The □330mm billet obtained in step S2.2 is returned to the furnace and kept at 30-80℃ below the phase transformation point for 1.5h-3h, then diagonally stretched to Φ310mm billet, with a deformation of 30%, a pressing speed of 40mm / s, a reduction of 15%-25%, a feed amount of 150mm-250mm, and air-cooled after forging.

[0016] Furthermore, in step S3, the rod obtained in step S2 is subjected to sawing, surface turning and polishing treatments to obtain a finished titanium alloy rod with a diameter of Φ200 mm to Φ350 mm.

[0017] Furthermore, the titanium alloy billet with a specification of □400mm to □600mm is a square-section billet with a size of □400mm to □600mm or other polygonal or circular billets with equal cross-sectional areas.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. Significant improvement in tissue uniformity:

[0020] The present invention stretches the rod by diagonally stretching the rod, thereby achieving alternating deformation of the edges and surfaces of the blank, improving the uniformity of the structure, and the extreme difference of the macrostructure and microstructure rating of the rod is ≤1 level.

[0021] 2. Performance consistency is significantly improved:

[0022] The present invention significantly improves the performance consistency of various parts of the bar by reasonably designing various parameters in the forging process, such as deformation temperature, deformation amount, pressing speed, pressing amount, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a low-magnification microstructure photograph of the head, middle and tail samples of the Φ300 mm TA15 titanium alloy bar provided in Example 1 of the present invention;

[0024] Figure 2 (a)-(c) are respectively high-magnification microstructure photographs of the center, R / 2 and edge of the head of the Φ300 mm TA15 titanium alloy rod provided in Example 1 of the present invention.

[0025] Figure 3 (a)-(c) are respectively high-magnification microstructure photographs of the center, R / 2 and edge of the middle part of the Φ300 mm TA15 titanium alloy rod provided in Example 1 of the present invention.

[0026] Figure 4 (a)-(c) are respectively high-magnification microstructure photographs of the center, R / 2 and edge of the tail of the Φ300 mm TA15 titanium alloy rod provided in Example 1 of the present invention.

[0027] Figure 5 It is a low-magnification microstructure photograph of the head, middle and tail samples of the Φ300mmTC11 titanium alloy bar provided in Example 2 of the present invention;

[0028] Figure 6 (a)-(c) are respectively high-magnification microstructure photographs of the center, R / 2 and edge of the head of the Φ300 mm TC11 titanium alloy rod provided in Example 2 of the present invention.

[0029] Figure 7 (a)-(c) are respectively high-magnification microstructure photographs of the center, R / 2 and edge of the middle part of the Φ300 mm TC11 titanium alloy rod provided in Example 2 of the present invention.

[0030] Figure 8 (a)-(c) are respectively high-magnification microstructure photographs of the center, R / 2 and edge of the tail of the Φ300 mm TC11 titanium alloy rod provided in Example 2 of the present invention.

[0031] Fig. 9It is a low-magnification microstructure photograph of the head, middle and tail samples of the Φ250mm TC4 titanium alloy bar provided in Example 3 of the present invention;

[0032] Fig.10 (a)-(c) are respectively high-magnification microstructure photographs of the center, R / 2 and edge of the head of the Φ250 mm TC4 titanium alloy rod provided in Example 3 of the present invention.

[0033] Fig.11 (a)-(c) are respectively high-magnification microstructure photographs of the center, R / 2 and edge of the middle part of the Φ250 mm TC4 titanium alloy rod provided in Example 3 of the present invention.

[0034] Fig.12 (a)-(c) are respectively high-magnification microstructure photographs of the center, R / 2 and edge of the tail of the Φ250 mm TC4 titanium alloy rod provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only used for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0036] In the present invention, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1-10, indicating that t is any integer selected from the integer group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0037] The temperature parameters in the present invention, if not specifically limited, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0038] The present invention provides a drawing forging method for improving the uniformity of the structure of a large-size titanium alloy bar, comprising the following steps:

[0039] S1: heating a titanium alloy billet of □400mm to □600mm in size to 30 to 80°C below the phase transition point and keeping the temperature constant;

[0040] S2: The blank obtained in step S1 is forged into a rod of Φ210 mm to Φ360 mm by diagonal drawing and forging for multiple times, the deformation amount of each time is 20% to 50%, the reduction amount in the drawing process is 15% to 25%, the pressing speed is 10 mm / s to 50 mm / s, and the feed amount is 140 mm to 350 mm;

[0041] S3: machining the bar obtained in step S2 into a finished titanium alloy bar of Φ200 mm to Φ350 mm.

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with specific embodiments and drawings of the specification. The specific embodiments described here are only used to explain the present invention, and the present invention is not limited thereto.

[0043] Example 1

[0044] This embodiment uses a TA15 titanium alloy billet with a size of □500mm after blanking for drawing and forging. The specific forging process is as follows:

[0045] (1) After the □500mm billet is kept at 940℃ for 6h, it is diagonally stretched to □400mm billet, with a deformation of 36%, a pressing speed of 40mm / s, a reduction of 15% to 25%, and a feed amount of 250mm to 350mm;

[0046] (2) The □400mm billet is returned to the furnace and kept at 940℃ for 2.5h, then diagonally stretched to □330mm billet, with a deformation of 32%, a pressing speed of 40mm / s, a reduction of 15% to 25%, and a feed amount of 200mm to 320mm;

[0047] (3) The □330mm billet is returned to the furnace and kept at 940℃ for 2h, then diagonally stretched to Φ310mm bar, with a deformation of 30%, a pressing speed of 40mm / s, a reduction of 15% to 25%, a feed of 150mm to 250mm, and air cooling after forging;

[0048] (4) The Φ310 mm TA15 titanium alloy bar is machined into a Φ300 mm finished bar through sawing, surface turning and polishing.

[0049] Samples were cut from the head, middle and tail of the prepared TA15 titanium alloy bar and annealed. They were heated to 840°C and kept at this temperature for 2 hours, then taken out of the furnace and air-cooled.

[0050] The macrostructure was examined on the head, middle and tail specimens after annealing, see Figure 1And it is graded according to GJB 2218A-2018TA15 Class B. The macrostructure of the rods meets the level 2 of the standard drawing, and the extreme value of the macrostructure of the rods is ≤ level 1.

[0051] The microstructures of the edge, R / 2 and core of the head, middle and tail samples after annealing were tested respectively. Figures 2 to 4 And it is rated according to GJB 2218A-2018TA15 Class B. The microstructure of the bars meets the standards of level 2-3 of the standard drawing, and the extreme microstructure of the bars is ≤ level 1.

[0052] Table 1 shows the test results of mechanical properties of the TA15 titanium alloy rod prepared in this example.

[0053] Table 1

[0054]

[0055] As can be seen from Table 1, the R / 2 performance data obtained by testing the head, middle and tail samples after annealing respectively indicate that the prepared TA15 titanium alloy rod has excellent comprehensive mechanical properties and good performance consistency.

[0056] Example 2: A TC11 titanium alloy billet with a size of □500 mm after blanking was used, and the specific forging process was as follows.

[0057] After keeping the □500mm billet at 970℃ for 6h, it is diagonally stretched to □400mm billet, with a deformation of 37%, a pressing speed of 30mm / s, a reduction of 15% to 25%, and a feed amount of 250mm to 350mm.

[0058] The □400mm billet is returned to the furnace and kept at 970℃ for 2.5h, then diagonally stretched to □330mm billet, with a deformation of 32%, a pressing speed of 30mm / s, a reduction of 15% to 25%, and a feed amount of 200mm to 320mm.

[0059] □330mm billet is returned to the furnace and kept at 970℃ for 2h, then diagonally stretched to Φ310mm bar, with deformation of 30%, pressing speed of 30mm / s, reduction of 15%~25%, feed amount of 150mm~250mm, and air cooling after forging.

[0060] Φ310mm specification bar machine is added to Φ300mm finished bar.

[0061] Samples were cut from the head, middle and tail of the bar and double annealed. They were heated to 950℃ and kept for 2 hours, then air-cooled after being taken out of the furnace. They were then heated to 530℃ and kept for 6 hours, then air-cooled after being taken out of the furnace.

[0062] The low-magnification structures were detected on the head, middle and tail samples after double annealing. Figure 5It can be seen that the low magnification shows a uniform fuzzy crystal structure.

[0063] The microstructures of the edge, R / 2, and core of the double annealed samples were tested respectively. Figures 6 to 8 It can be seen that the microstructure is a uniform two-phase processed structure.

[0064] The performance of R / 2 was tested on the head, middle and tail samples after double annealing treatment. Table 2 shows the mechanical property test results.

[0065] Table 2

[0066]

[0067] As can be seen from Table 2, the R / 2 performance data obtained by testing the head, middle and tail samples after annealing respectively indicate that the prepared TC11 titanium alloy rod has excellent comprehensive mechanical properties and good performance consistency.

[0068] Embodiment 3: Using the TC4 titanium alloy billet with a specification of □450mm after blanking, the specific forging process is as follows.

[0069] After being kept at 950℃ for 6h, the □450mm billet is diagonally stretched to □350mm billet, with a deformation of 40%, a pressing speed of 40mm / s, a reduction of 15% to 25%, and a feed amount of 220mm to 360mm.

[0070] The □350mm billet is returned to the furnace and kept at 950℃ for 2.5h, then diagonally stretched to □280mm billet, with a deformation of 36%, a pressing speed of 40mm / s, a reduction of 15% to 25%, and a feed amount of 170mm to 280mm.

[0071] □The 280mm billet is returned to the furnace and kept at 950℃ for 2h before being diagonally drawn to Φ260mm bar, with a deformation of 33%, a pressing speed of 40mm / s, a reduction of 15%~25%, a feed amount of 150mm~250mm, and air cooling after forging.

[0072] Φ260mm specification bar machine is added to Φ250mm finished bar.

[0073] Samples were cut from the head, middle and tail of the bar and annealed. They were heated to 780℃ and kept at this temperature for 2 hours, then air-cooled after being taken out of the furnace.

[0074] The low-magnification structures were detected on the head, middle and tail samples after annealing. Fig. 9 It can be seen that the low magnification shows a uniform fuzzy crystal structure.

[0075] The microstructures of the edge, R / 2, and core of the head, middle, and tail samples after annealing were tested respectively. Figure 10-12It can be seen that the microstructure is a uniform two-phase processed structure.

[0076] The performance of R / 2 was tested on the head, middle and tail samples after annealing treatment. Table 3 shows the mechanical property test results.

[0077] Table 3

[0078]

[0079] As can be seen from Table 3, the R / 2 performance data obtained by testing the head, middle and tail samples after annealing respectively indicate that the prepared TC4 titanium alloy rod has excellent comprehensive mechanical properties and good performance consistency.

[0080] It should be noted that the above-described embodiments are only preferred embodiments of the present invention. For those skilled in the art, without departing from the principles of the present invention, the present invention may be modified, improved and replaced with equivalents, and these modifications, improvements and equivalent replacements are also considered to fall within the scope of protection of the claims of the present invention.

Claims

1. A drawing forging method for improving the uniformity of the titanium alloy bar structure, characterized in that: The steps include: S1: heating a titanium alloy billet of □400mm to □600mm in size to 30 to 80°C below the phase transition point and keeping the temperature constant; S2: The blank obtained in step S1 is forged into a rod of Φ210 mm to Φ360 mm by diagonal drawing and forging for multiple times, the deformation amount of each time is 20% to 50%, the reduction amount in the drawing process is 15% to 25%, the pressing speed is 10 mm / s to 50 mm / s, and the feed amount is 140 mm to 350 mm; S3: machining the bar obtained in step S2 into a finished titanium alloy bar of Φ200 mm to Φ350 mm.

2. The drawing forging method for improving the uniformity of the titanium alloy bar structure according to claim 1, characterized in that: In the step S1, the insulation time is 3h to 6h.

3. The drawing forging method for improving the uniformity of the titanium alloy bar structure according to claim 1, characterized in that: In step S2, the number of firings is 2 to 6.

4. The drawing forging method for improving the uniformity of the titanium alloy bar structure according to claim 1, characterized in that: For a titanium alloy billet with a size of □500 mm, step S2 specifically includes: S2.1: The blank obtained in step S1 is diagonally stretched to a blank of □400mm, with a deformation amount of 36%, a pressing speed of 40mm / s, a pressing amount of 15% to 25%, and a feed amount of 250mm to 350mm; S2.2: The □400mm billet obtained in step S2.1 is returned to the furnace and kept at 30-80°C for 1.5-3h below the phase transition point, and then diagonally stretched to □330mm billet, with a deformation of 32%, a pressing speed of 40mm / s, a reduction of 15%-25%, and a feed amount of 200mm-320mm; S2.3: The □330mm billet obtained in step S2.2 is returned to the furnace and kept at 30-80℃ below the phase transformation point for 1.5h-3h, then diagonally stretched to Φ310mm billet, with a deformation of 30%, a pressing speed of 40mm / s, a reduction of 15%-25%, a feed amount of 150mm-250mm, and air-cooled after forging.

5. The drawing forging method for improving the uniformity of the titanium alloy bar structure according to claim 1, characterized in that: In step S3, the rod obtained in step S2 is sawed, surface turned and polished to obtain a finished titanium alloy rod with a diameter of Φ200 mm to Φ350 mm.

6. The drawing forging method for improving the uniformity of the titanium alloy bar structure according to claim 1, characterized in that: The titanium alloy blank with a specification of □400mm to □600mm is a square-section blank with a size of □400mm to □600mm or other polygonal or circular blanks with equal cross-sectional areas.

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