Forging method for sheet type titanium alloy die forgings

Abstract

The invention belongs to the field of forging hot working, and particularly relates to a forging method for a sheet type titanium alloy die forging. The blank and the die of the sheet titanium alloy die forging are designed, the blank thickness is increased at the sharp corner corresponding to the blank, and meanwhile, the ear type cavity design is added at the sharp corner corresponding to the die, so that the blank flowing speed at the sharp corner of the forging is increased, and the problem that the round corner at the sharp corner of the forging is difficult to fill is solved; the forge piece is prevented from being repaired or scrapped due to the fact that the fillet is not filled with the missing meat, the yield of the forge piece is improved, meanwhile, the utilization rate of forge piece raw materials is improved, and the die forging heating number is reduced, so that the forge piece production efficiency is improved, and the forge piece production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the field of forging hot processing, and in particular relates to a forging method for a thin-plate titanium alloy die forging. Background Art

[0002] Titanium alloy die forgings for aircraft fuselages in my country typically include thin plate forgings of various shapes. These forgings are small in thickness and, due to machining allowance limitations, have small corner radiuses (r ≤ 10mm). Furthermore, titanium alloys have a narrow forging temperature range, poor thermal conductivity, high viscosity, poor fluidity, and high deformation resistance, along with strict requirements for deformation volume and rate. This makes plastic forming of thin plate forgings difficult. In the actual forging process, the difficulty in filling corner radiuses is one of the main reasons affecting the pass rate of thin titanium alloy forgings.

[0003] In practice, increasing the blank volume can solve the problem of severely underfilled fillets, but this approach reduces material utilization. Alternatively, increasing the number of forging cycles can further ensure full fillets, but multiple cycles of small deformations can lead to internal structural inhomogeneity and unstable performance data. Summary of the Invention Purpose of the invention: To provide a forging method for thin plate titanium alloy die forgings, reduce the difficulty of forming thin plate titanium alloy die forgings, reduce the number of die forging fires of thin plate titanium alloy forgings, improve the uniformity of forging structure, and further improve the stability of various performance data.

[0004] Technical solution: A method for forging a thin-plate titanium alloy die forging, comprising: Step 1: Place the heated bar on the anvil of a free forging hammer or a free forging press, upset it radially to a certain height, and then upset it several times to reshape all surfaces into a rectangle, obtaining a rectangular blank with a thickness of H1, a width of B1, and a length of L1. The pressing plate and hammer anvil are used to cooperate, leaving only the height of the four sharp corners of the rectangular blank unchanged, and the cross-shaped part in the middle of the blank in the length direction L2 and the width direction B2 is pressed down to the height H2 along the thickness direction, and the surrounding of the blank is tidied to obtain the desired final shape; Step 2: Determine the final forging die, and use the final forging die to forge the rough part to obtain a die forging. The die has an "ear-shaped" cavity at the sharp corner. The "ear-shaped" cavity includes a circular arc surface and two inclined surfaces, and the two inclined surfaces are tangent or intersecting with the circular arc surface respectively. Step 3: Heat the blank and quickly transfer it to the final forging die designed in step 2 after it comes out of the furnace, so that the center of the blank coincides with the center of the die cavity. Use a counter-hammer or press to slowly press it down, and then hammer or press it down again to obtain the final forging.

[0005] Preferably, in step 1, during the blank forging process, the deformation amount per fire does not exceed 50%, and the pressing speed is ≤5mm / s; the feed rate is determined according to the width of the hammer anvil used: the feed rate per hammer is equal to 1 / 3 of the hammer anvil width; the pressing amount per hammer is controlled to be 10-30mm; and the preheating temperature of the hammer anvil and the pressing plate used is 200-300℃.

[0006] Preferably, in step 1, the relationship between H1 and H2 is: H1=H2+(5-20)mm, B1=B2+2×(50-150)mm, L1=L2+2×(50-150)mm.

[0007] Preferably, in step 2, the final forging die is determined, specifically: On the length side and width side b dimensions of the square die corresponding to the forging, add oblique lines with an inclination of θ respectively. Then, starting from the center of the fillet r at the sharp corner of the square die, radiate outward along the 45° direction to make a line segment E. The length of line segment E is set to L2, and the dimension ΔL is the size of the margin added to ensure that the fillet is full. Subsequently, determine a circle with a radius of R, where R>ΔL+r. The circle is tangent or intersecting with the oblique lines on both sides, and the center of the circle is on the extension line of line segment E.

[0008] Preferably, in step 2, if the circle intersects the obtuse lines on both sides, the obtuse angle formed is rounded to R50-100 mm.

[0009] Preferably, in step 2, the angle θ is 5-15°, and the ΔL is 10-30 mm. For thin plate forgings, if the width dimension B ≥ 400mm, then b = 100-150mm, For thin plate forgings, if the width dimension B is less than 400mm, then b≈1 / 3B.

[0010] Preferably, in step three, for β-forged or near-β-forged titanium alloy forgings, the die forging deformation is controlled to be 30-50%, and for conventionally forged titanium alloy forgings, the die forging deformation is controlled to be 20%-60%.

[0011] Preferably, in step three, the mold preheating temperature is 250-350° C., and the mold lubricant is water-based graphite emulsion.

[0012] Preferably, in step three, when using counter-hammer forging, the initial equipment air pressure is ≥0.6MPa, and the interval between each hammer is 1-3s.

[0013] When using a press forging, the pressing speed is less than 5mm / s.

[0014] Beneficial effects: By designing the blank and die of thin-plate titanium alloy die forgings, the blank thickness is increased at the corresponding sharp corners of the blank, and at the same time, an "ear-type" cavity design is added at the corresponding sharp corners of the die to improve the flow rate of the blank at the sharp corners of the forging, solving the problem of difficult filling of the fillet at the sharp corners of the forging, avoiding the rework or scrapping of forgings due to lack of fillet at the fillet, improving the qualified rate of forgings, and at the same time improving the utilization rate of raw materials for forgings, reducing the number of die forging fires, thereby improving the production efficiency of forgings and reducing the production cost of forgings.

[0015] This invention can be used not only for rectangular thin plate forgings, but also for special-shaped thin plate forgings. For titanium alloy structural parts with sharp corners at local thin plates in the forging structure, the mold design method of the present invention can also be used to solve the problem of difficulty in filling the rounded corners at the sharp corners. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a rough sketch; Figure 2 This is a schematic diagram of the die design for thin plate forgings; Figure 3 Schematic diagram of the front beam joint forging in the embodiment. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the implementation of this application will be described in more detail below in conjunction with the drawings in the implementation of this application. In the drawings, the same or similar numbers throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and should not be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in conjunction with the drawings.

[0018] In the description of the present invention, it should be understood that the terms "center", "axial", "vertical", "up", "down", "upper end", "bottom end", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present invention.

[0019] The applicant's research found that during the forging process, according to the law of least resistance, the billet located in the middle of the length and width directions has the fastest feeding speed, forming a bulge. Due to the sharp corner effect at the sharp corner of the billet, the forging temperature at the sharp corner of the billet drops rapidly during the billet transfer process. During the forging process, the billet feed speed at the sharp corner is slow. When the bulge on all sides contacts the side wall of the mold cavity, the mold temperature is much lower than the billet temperature due to the contact between the billet and the side wall of the cavity, resulting in a decrease in the surface temperature of the billet, slowing down the feeding speed of the intermediate billet to the rounded corner. Secondly, due to the influence of the friction between the side wall of the mold cavity and the billet, the feeding speed of the intermediate billet to the rounded corner is further reduced. In particular, when burrs appear locally, the burr thickness is thin and the cooling rate is fast, which greatly increases the deformation resistance. Under multiple effects, the rounded corners at the sharp corners are seriously not filled, which cannot meet the requirements of the drawing.

[0020] Step 1: On a free forging hammer or a free forging press, the heated bar is placed on the hammer anvil and radially upset to a certain height. After multiple upsettings, all surfaces are reshaped into a rectangle to obtain a rectangular blank with a thickness of H1, a width of B1, and a length of L1. The pressing plate and hammer anvil are used to cooperate, leaving only the height of the four sharp corners of the rectangular blank unchanged, and the cross-shaped part in the middle of the blank in the length direction L2 and the width direction B2 is pressed down to the height H2 along the thickness direction, and the surrounding of the blank is tidied to obtain the desired final shape; The forging process can be completed in multiple fires. The specific fire is determined according to the diameter of the bar and the required rough thickness h1, ensuring that the deformation of each fire does not exceed 50% to prevent heartburn.

[0021] The relationship between H1 and H2 is: H1=H2+(5-20)mm B1=B2+2×(50-150)mm, L1=L2+2×(50-150)mm, During the blank forging process, the pressing speed is controlled to be ≤5mm / s. The feed rate is determined by the width of the hammer anvil used. The feed rate per hammer is ≈ 1 / 3 of the width of the hammer anvil. Control the amount of each hammer press to 10-30mm; The preheating temperature of the hammer, anvil, and tooling used is 200-300℃.

[0022] Step 2: A die designed to facilitate filling sharp corners in thin-plate titanium alloy die forgings involves adding an "ear-shaped" cavity to the sharp corner. First, a line with a slope of θ is added at a distance b from the length and width sides of the die. Then, starting from the center of the original sharp corner fillet r, a line segment E is radiated outward at a 45° angle to the length side. The length of this line segment is L2, and the dimension ΔL is the margin added to ensure the fillet is filled. Next, a circle with a radius of R, where R > ΔL + r, is determined. This circle is tangent or intersecting to the two side fillets, with its center on the extension of line segment E. Finally, all obtuse corners are rounded to a radius of 50-100mm. Among them, the rest of the mold is designed normally according to the design theory based on the forging size.

[0023] The angle θ is generally 5-15°, and the ΔL is 10-30mm. For thin plate forgings with a width dimension B ≥ 400 mm, b = 100-150 mm; for thin plate forgings with a width dimension B < 400 mm, b ≈ 1 / 3 B. Step 3: The blank is heated and quickly transferred to the mold designed in step 2 after being taken out of the furnace, so that the center of the blank coincides with the center of the mold cavity. A counter-hammer or press is used to slowly press it down, and then hammer or press it down again to obtain the final forging.

[0024] For β-forged or near-β-forged titanium alloy forgings, the die forging deformation is controlled at 30-50%. For conventionally forged titanium alloy forgings, the die forging deformation is controlled at 20%-60%.

[0025] The mold preheating temperature is 250-350℃, and the mold lubricant is water-based graphite emulsion.

[0026] When using counter-blow hammer forging, the initial equipment air pressure is ≥0.6MPa, and the interval between each hammer is 1-3s.

[0027] When using a press forging, the pressing speed is less than 5mm / s.

[0028] The mold material used above is 5CrNiMo.

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be further described below with reference to the accompanying drawings in the embodiments of the present invention.

[0030] Example: The forging of the front beam joint of a certain type of machine is made of TC21. The forging is a thin plate forging with a thickness of only 50mm, a length of L=850mm, a width of B=440mm, and a projected area of ​​0.37mm 2The forging weight is 72kg. Compared with other structural parts of the same weight, the projected area of ​​the front beam joint forging is much larger than other forgings, and it requires β forging, which is difficult to forge. See the schematic diagram of the forging for Figure 3 , Step 1: Forge the blank on a 16MN free forging press. Place the φ210×560mm bar in an electric furnace and heat it at 30°C below the phase transition point. After taking it out of the furnace, quickly transfer it to the hammer anvil. First fire: flatten the φ210×550mm bar as a whole to ~400mm×310mm×160mm.

[0031] Second fire: flatten and reshape to ~640mm×310mm×100mm The third fire: Only the height of the four sharp corners of the blank is kept unchanged, and the middle length of the blank is L2=500mm, the width is B2=150mm, and the cross-shaped part is pressed down along the thickness direction to a height of H2=85mm. The blank is trimmed around and the final blank of L1×B1×H2=800mm×300mm×85mm is obtained after shaping.

[0032] Step 2: Design a mold that is conducive to filling the sharp corners of the front beam joint forging, and add an "ear-shaped" cavity at the sharp corners of the mold. First, add a slant line with an angle of 10° at a distance of 130mm from the length side and width side of the mold. Then, starting from the center of the circle with a fillet r=5mm at the original sharp corner, radiate outward at an angle of 45° with the length side, and make a line segment E. To ensure that the fillet is filled, add a margin ΔL=18mm. Subsequently, determine a circle with a radius of R=40mm, which is intersected by the slant lines on both sides, and the center of the circle is on the extension line of line segment E. Finally, fillet all obtuse angles to R80mm to obtain the forging mold.

[0033] Step 3: Forging is performed on a 630KJ hammer. Glass lubricant is evenly sprayed on the surface of the blank before heating. The heating temperature is kept at 15°C above the phase transition point. After taking it out of the furnace, it is quickly transferred to the mold designed in step 2. The first hammer is pressed down slowly, and the subsequent 20-22 hammers are clicked. This can effectively reduce the flow resistance and promote the blank to flow into the increased "ear-shaped" cavity instead of forming a large amount of flash.

[0034] The forgings produced using the above method are formed by one die forging fire, and the rounded corners of the four sharp corners of the forgings are well filled, so there is no need to increase the die forging fire for rework. The qualified rate of forgings is 100%, and the material utilization rate is as high as 84%, which is a great improvement compared with the ordinary scheme. After the final physical and chemical testing, the forgings have uniform structure, the performance data meets the standard requirements, and have good stability.

[0035] The mold lubricant used above is water-based graphite emulsion, and the mold material is 5CrNiMo.

[0036] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for forging thin-plate titanium alloy die forgings, characterized in that: include: Step 1: Place the heated bar on the anvil of a free forging hammer or a free forging press, upset it radially to a certain height, and then upset it several times to reshape all surfaces into a rectangle, obtaining a rectangular blank with a thickness of H1, a width of B1, and a length of L1. The pressing plate and hammer anvil are used to cooperate, leaving only the height of the four sharp corners of the rectangular blank unchanged, and the cross-shaped part in the middle of the blank in the length direction L2 and the width direction B2 is pressed down to the height H2 along the thickness direction, and the surrounding of the blank is tidied to obtain the desired final shape; Step 2: Determine the final forging die, and use the final forging die to forge the rough part to obtain a die forging. The die has an "ear-shaped" cavity at the sharp corner. The "ear-shaped" cavity includes a circular arc surface and two inclined surfaces. The two inclined surfaces are tangent or intersecting with the circular arc surface respectively. Step 3: Heat the blank and quickly transfer it to the final forging die designed in step 2 after it comes out of the furnace, so that the center of the blank coincides with the center of the die cavity. Use a counter-hammer or press to slowly press it down, and then hammer or press it down again to obtain the final forging.

2. The method according to claim 1, wherein In step 1, during the forging process of the blank, the deformation of each fire does not exceed 50%, and the pressing speed is ≤5mm / s; the feed rate is determined according to the width of the hammer anvil used: the feed rate of each hammer is equal to 1 / 3 of the hammer anvil width; the pressing amount of each hammer is controlled to be 10-30mm; the preheating temperature of the hammer anvil and the pressing plate used is 200-300℃.

3. The method according to claim 2, characterized in that In step 1, the relationship between H1 and H2 is: H1=H2+(5-20)mm, B1=B2+2×(50-150)mm, L1=L2+2×(50-150)mm.

4. The method according to claim 1, wherein In step 2, determine the final forging die, specifically: On the length side and width side b dimensions of the square die corresponding to the forging, add oblique lines with an inclination of θ respectively. Then, starting from the center of the fillet r at the sharp corner of the square die, radiate outward along the 45° direction to make a line segment E. The length of line segment E is set to L2, and the dimension ΔL is the size of the margin added to ensure that the fillet is full. Subsequently, determine a circle with a radius of R, where R>ΔL+r. The circle is tangent or intersecting with the oblique lines on both sides, and the center of the circle is on the extension line of line segment E.

5. The method according to claim 4, characterized in that In step 2, if the circle intersects the obtuse lines on both sides, the obtuse angle formed is rounded to R50-100mm.

6. The method according to claim 5, characterized in that In step 2, the angle θ is 5-15°, and the ΔL is 10-30 mm. For thin plate forgings, if the width dimension B ≥ 400mm, then b = 100-150mm; For thin plate forgings, if the width dimension B is less than 400mm, then b≈1 / 3B.

7. The method according to claim 1, characterized in that In step 3, for titanium alloy forgings produced by beta forging or near beta forging, the die forging deformation is controlled to be 30-50%, and for titanium alloy forgings produced by conventional forging, the die forging deformation is controlled to be 20%-60%.

8. The method according to claim 1, characterized in that In step 3, the mold is preheated to a temperature of 250-350°C and the mold is lubricated with water-based graphite emulsion.

9. The method according to claim 1, characterized in that In step three, when using a counter-hammer forging, the initial equipment air pressure is ≥0.6MPa, and the interval between each hammer is 1-3s; when using a press forging, the pressing speed is less than 5mm / s.

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