A method for forming an asymmetric "Y"-shaped titanium alloy forging blank for aerospace applications

Abstract

This invention belongs to the field of hot forming of metal materials, specifically relating to a forming method for an asymmetric "Y"-shaped titanium alloy forging blank for aerospace applications. By designing a dedicated forming die and utilizing eccentric pressing, two arms of different lengths in an asymmetric "Y" shape are forged. The main deformation process is achieved through the die, resulting in high controllability of the production process, easy assurance of dimensional accuracy, and high-quality completion. It effectively guarantees the final forging temperature of the blank, improves the uniformity of the material structure, and ensures that the streamlines of the produced forging blank are distributed along the forging contour, guaranteeing the mechanical properties of the final forging in all directions, reducing the scrap rate, and improving material utilization and production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of hot forming of metal materials, specifically relating to a forming method for an asymmetric "Y"-shaped titanium alloy forging blank for aerospace applications. Background Technology

[0002] Titanium alloys are characterized by low density and high specific strength, and are widely used in aviation, aerospace, and weaponry. The strength of titanium alloys is comparable to that of general high-strength structural steel and high-temperature alloys, but their density is only about 57% of steel and about 55% of high-temperature alloys, resulting in higher specific strength. Aluminum and magnesium alloys have lower densities, only about 60% and 40% of titanium alloys respectively, but their tensile strength is less than one-third that of titanium alloys. This is the main reason why the use of aluminum alloys and steel in advanced fighter jets and engines is gradually decreasing, while the use of titanium alloys is continuously increasing.

[0003] In recent years, with the rapid development of the global aviation industry, higher requirements have been placed on the applications and performance of aircraft. High-strength titanium alloys have been widely used, especially in aircraft structural components. For some large, long rod-like structural components with complex shapes, production typically requires first forging a blank, and then die forging to obtain the final forging shape. Currently, for forging blanks of complex-shaped structural components, especially asymmetrical products, the method of free forging with N-stage upsetting, drawing, and shaping is used, where N represents the number of forging stages. This method, for complex-shaped parts, requires significant allowance in areas where shaping is impossible during blank design, resulting in irregular dimensions, poor consistency, high forging stages, low material utilization, and impacting factory production efficiency. The designed forging production process is not ideal.

[0004] Therefore, there is an urgent need for a new technical solution to produce such complex-shaped asymmetrical titanium alloy structural blanks in order to achieve efficient production of this type of product. Summary of the Invention

[0005] Purpose of the invention: To provide a forming method for asymmetric "Y"-shaped titanium alloy forging blanks for aerospace applications, solving the problem of difficult forming of asymmetric "Y"-shaped titanium alloy forging blanks, and improving material utilization and factory production efficiency.

[0006] Technical solution:

[0007] A method for forming an asymmetric "Y"-shaped titanium alloy forging blank for aerospace applications, the asymmetric "Y"-shaped titanium alloy forging blank comprising a head and a rod, wherein the root of the two asymmetric arms of the head is rounded off, including:

[0008] Step 1: Material cutting: Determine the weight of the bar stock based on the weight of the forging. The weight of the bar stock can be: weight of forging + weight of forging × 15% to 25%;

[0009] Step 2: Heating the bar stock:

[0010] The heating equipment should be an electric furnace with an accuracy of ±10℃. The heating temperature can be 30℃~50℃ below the phase change point. When heating cold materials, the holding time coefficient should be 0.6~1.0min / mm.

[0011] Step 3: The heated bar stock is pre-forged to obtain a preform, wherein the preform is a stepped slab of equal thickness;

[0012] Using a free forging press or a fast forging machine, the bar stock is first flattened as a whole, then divided and drawn out, and forged into a stepped slab of equal thickness. The stepped slab of equal thickness has a wide cross section at one end and a narrow cross section at the other end.

[0013] Step 4: Use a die and pressure plate to forge the precast billet to obtain an intermediate billet:

[0014] The stepped slab of equal thickness forged in step three is pressed in the thickness direction of the head, with a pressing amount of 1 / 2 to 1 / 3 of the thickness dimension.

[0015] Then, the stepped slab is placed vertically into the mold, with the length of the stepped slab corresponding to the longitudinal direction of the mold. The length of the head is pressed using a free forging hammer anvil.

[0016] The head is divided into sections and eccentrically pressed so that the width of the stepped slab head is the same as the size of the head of the "Y" shaped cavity of the mold. The amount of pressing is the difference in length between the two arms of the forging blank.

[0017] The intermediate blank is obtained by pressing out the arc shape at the connection of the two arms of the asymmetrical "Y" shaped forging blank using a pressure plate.

[0018] Step 5: Lengthen and shape the intermediate billet rod to obtain the forging blank.

[0019] Preferably, in step four, the billet can be removed from the mold multiple times during the forging process to flatten the thickness dimension and make the billet regular.

[0020] Preferably, step five specifically includes:

[0021] The rod portion of the "Y"-shaped intermediate billet is drawn out to the required size of the billet, resulting in an asymmetric "Y"-shaped titanium alloy forging billet with the same streamline as the raw material.

[0022] Preferably, in step four, the overall shape of the mold is a cube, the longitudinal dimension is smaller than the size of the forging blank, the thickness is the sum of the thickness of the step blank and the thickness of the mold wall on both sides, and the mold wall thickness is 150-200mm; the transverse dimension is 50-100mm larger than the maximum width of the cavity "Y" shape on one side.

[0023] Preferably, in step four, the longitudinal section of the mold cavity is "Y"-shaped, the "Y"-shaped rod of the cavity is square or rectangular, and the rod is designed with a draft angle of 0.5° to 2°. When the ratio of the rod length to the rod thickness is greater than 3, the draft angle is smaller; when the ratio of the rod length to the rod thickness is less than 3, the draft angle is larger. The two inclined angles of the "Y"-shaped head are the same as the angles of the forging blank, and the chamfer of the transition area between the cavity rod and the head is R100 to R150.

[0024] Preferably, in step four, the pressure plate is designed with a semi-circular cross-section or an arc-shaped cross-section. The radius of the pressure plate cross-section is greater than the radius of the arc at the root of the two arms of the forging blank, and the length of the pressure plate is 100mm larger than the thickness dimension of the blank.

[0025] Preferably, in step three, the ratio of the width section to the narrow section of the stepped slab should be greater than or equal to 1.5; the ratio of the length to the thickness of the width section should be less than or equal to 2.

[0026] Preferably, in step four, the heating parameters before forging satisfy:

[0027] The heating equipment should be an electric furnace with an accuracy of ±10℃. The heating temperature can be 30℃~50℃ below the phase change point. When heating cold materials, the holding time coefficient should be 0.6~1.0min / mm. When returning hot materials to the furnace, the holding time coefficient should be 0.3~0.5min / mm.

[0028] Beneficial effects:

[0029] This invention provides a forming method for asymmetric "Y"-shaped titanium alloy forging blanks for aerospace applications. Its advantages include: during forging, a dedicated forming die is designed, and an eccentric pressing method is used to forge two arms of different lengths in an asymmetric "Y" shape. The main deformation process relies on the die, resulting in high controllability of the production process, easy assurance of dimensional accuracy, and high-quality completion. It effectively ensures the final forging temperature of the blank, improves the uniformity of the material structure, and ensures that the streamlines of the produced forging blank are distributed along the forging contour, guaranteeing the mechanical properties of the final forging in all directions, reducing the scrap rate of forgings, and improving material utilization and production efficiency. Attached Figure Description

[0030] Figure 1 Schematic diagram of the outer contour of an asymmetric "Y"-shaped forging blank;

[0031] Figure 2 Stepped slabs of uniform thickness;

[0032] Figure 3 Schematic diagram of the blank material distribution and eccentric pressing of an asymmetric "Y" shaped forging;

[0033] Figure 4 Schematic diagram of the forming mold for an asymmetric "Y"-shaped forging blank. Detailed Implementation

[0034] A method for forming an asymmetric "Y"-shaped titanium alloy forging blank for aerospace applications, the shape of which is... Figure 1 As shown, the method includes the following steps:

[0035] Step 1: Material preparation process

[0036] The blanking weight is determined based on the weight of the forging. The blanking weight can be taken as: forging weight + forging weight × 15% to 25%. The material allowance coefficient can be selected within the range of 15% to 25%, depending on the complexity of the forging shape and the number of production passes.

[0037] Step Two: Heating Process

[0038] The heating equipment should be an electric furnace with an accuracy of ±10℃ or higher. The heating temperature can be 30℃ to 50℃ below the phase transformation point. This temperature should be determined according to the different types of titanium alloys. When heating cold materials, the holding time coefficient should be 0.6 to 1.0 min / mm. When returning hot materials to the furnace, the holding time coefficient should be 0.3 to 0.5 min / mm.

[0039] Step 3: Precast Billet Forging Process

[0040] Using a free forging press or a high-speed forging mill, the bar stock is first flattened as a whole, then divided and drawn into elongated sections, and forged into stepped slabs of equal thickness, such as... Figure 2 For stepped slabs of equal thickness, one end has a wide cross section and the other end has a narrow cross section. The ratio of the wide cross section to the narrow cross section should be greater than or equal to 1.5; the ratio of the length to the thickness of the wide cross section should be less than or equal to 2.

[0041] Step 4: Intermediate billet forging process

[0042] like Figure 3 and Figure 4Molding mold design: The overall shape of the mold is a cube. The longitudinal dimension is determined according to the required blank size. The thickness is the sum of the thickness of the stepped blank and the thickness of the mold wall on both sides. To ensure the strength of use, the mold wall thickness is generally 150-200mm. The transverse direction requires eccentric pressing. In order to prevent instability, the transverse dimension of the mold design should be 50-100mm larger than the maximum width of the "Y" shape of the cavity on one side. The longitudinal section of the cavity is "Y" shaped. When designing a narrow "Y" shaped section, the section can be square or rectangular, depending on the actual section of the product rod. It is important to note that the rod needs to be designed with a draft angle of 0.5° to 2°. When the ratio of the rod length to the rod thickness is greater than 3, the draft angle should be smaller; when the ratio is less than 3, the draft angle should be larger. When designing a wide "Y" shaped section, the angle of the inclined surfaces of the two arms should be determined according to the design angle of the blank. During pressing, ensure that the blank fits snugly against the inclined surface of the mold. At the same time, chamfer R100 to R150 should be applied to the transition area between the rod and the head to prevent the blank from folding in this area.

[0043] Pressure plate design: The pressure plate is designed with a semi-circular or curved cross-section. The size is determined according to the size of the forging blank. The length of the pressure plate should be about 100mm longer than the thickness dimension of the blank.

[0044] The stepped slab of uniform thickness forged in step three is first pressed down in the thickness direction of the wide section, with a reduction of about 1 / 3. Then, the slab is placed vertically into the mold, with the length of the stepped slab corresponding to the longitudinal direction of the mold. Using a free forging hammer anvil, the length of the wide section is pressed down. According to the product rough shape design, the material is divided using the pressure plate mentioned in step four, and eccentric pressing is performed to make the width of the slab close to the size of the upper end of the "Y"-shaped cavity of the mold. The reduction is determined based on the difference in length between the two arms of the "Y"-shaped slab. After pressing, a pressure plate with a semi-circular or curved cross-section is used to press out the arc-shaped bottom at the connection between the two walls of the "Y"-shaped slab. At this point, the head of the "Y"-shaped slab is formed. During the forging process, the slab can be removed from the mold multiple times to flatten the thickness direction and make the slab regular.

[0045] Step 5: Final blank drawing and shaping process

[0046] The intermediate billet obtained in step four, which has a similar shape to the forging blank, is free-forged to elongate the narrow cross-section of the "Y"-shaped billet to the required size of the blank, thereby obtaining a blank of an asymmetric "Y"-shaped titanium alloy forging with the same streamline as the raw material.

[0047] In step four, the pre-forging heating parameters are:

[0048] The heating equipment should be an electric furnace with an accuracy of ±10℃ or higher. The heating temperature can be 30℃ to 50℃ below the phase transformation point. This temperature should be determined according to the different types of titanium alloys. When heating cold materials, the holding time coefficient should be 0.6 to 1.0 min / mm. When returning hot materials to the furnace, the holding time coefficient should be 0.3 to 0.5 min / mm.

[0049] Example:

[0050] This is a forging for an outer cylinder of a certain type of aircraft, made of TC32 alloy and produced from Φ300 round bars. This forging is a typical asymmetrical "Y"-shaped forging, with a total length of nearly 1150mm and a length difference of approximately 200mm between the two "Y" arms. The difficulty in blank production lies in the need for precise material division and strict dimensional control during the forging of the asymmetrical "Y" arms to ensure full filling of the forging during die forging. Traditional blank production methods involve first forging the bar stock into a plate shape, then dividing it step by step and forging it to the required size using pinching and pulling methods. This method has poor dimensional control accuracy, requires many forging passes, and therefore has low efficiency. After multiple verifications, this invention adopts the following process for production.

[0051] Process method:

[0052] 1. Material cutting process

[0053] The forging weighs 147.5 kg. Since the forging blank needs to be divided and forged in multiple stages, the allowance coefficient is taken as 25% when cutting the blank. The calculated blank weight is 184.5 kg, and the converted blank size is Φ300mm×580mm.

[0054] 2. Heating process

[0055] During the forging of the blanks, heating is performed below the phase transformation point. An electric furnace with an accuracy of ±10℃ is sufficient to meet the requirements. The material of this product is TC32 alloy, so the heating temperature is selected as 40℃ below the phase transformation point. The holding coefficient for cold material heating is 0.8min / mm, and the holding time coefficient for hot material returning to the furnace is 0.5min / mm. If there are no folds or cracks on the surface, continuous hot material returning to the furnace can be carried out.

[0056] 3. Precast billet forging process

[0057] a. Tooling preheating: All parts of the hammer, anvil, and fixtures that come into contact with the billet should be preheated to a temperature of 200-300℃.

[0058] b. Forging dimensions:

[0059] The Φ300mm×580mm bar stock is first flattened and shaped into a slab with a length of 785mm, a width of 350mm, and a thickness of 190mm. The slab is then divided at approximately 250mm along its length and drawn to a length of 535mm from one end, resulting in a final length of 555mm × 200mm × 190mm. Note that the drawn length does not include the approximately 100mm transition section between the 350mm and 200mm width dimensions. The resulting forged slab is a stepped slab of uniform thickness. Figure 2 The shape shown.

[0060] 4. Intermediate billet forging

[0061] Molding mold design:

[0062] The mold design has a longitudinal dimension of 650mm, a maximum blank width of 580mm, a transverse dimension of 780mm, and a height dimension of 600mm. The rod of the "Y"-shaped cavity is designed as a square with a dimension of 200mm according to the blank requirements, and the draft angle of the rod is 1.5°. The angle of the two arms at the head of the "Y"-shaped cavity is determined to be 43° according to the blank, to ensure that the blank and the mold fit completely during pressing. At the same time, the transition area between the rod and the head is chamfered with R100.

[0063] Pressure plate design: The pressure plate is designed as a semi-circular pressure plate, using a round bar material with dimensions of Φ150mm×210mm, which is divided into two along the axial direction for use.

[0064] a. Tooling preheating: All parts of the hammer, anvil, and fixtures that come into contact with the billet should be preheated; preheating temperature 200-300℃;

[0065] b. Forging dimensions:

[0066] First, press the thickness of the stepped slab blank of equal thickness to 130mm at one end of the wide section. After shaping, place the blank vertically into the forming mold and press it down as a whole to fill the cavity. At the same time, press the length of the blank to 220mm from the top surface of the mold. Then, divide the blank at 110mm from one end and press down the 440mm part along the length direction by about 130mm. At this point, the asymmetrical "Y" shaped basic structure has been formed. Then, use a pressure plate to forge the arc-shaped bottom at the connection of the two walls of the "Y" shaped blank. During the forging process, the blank is taken out of the mold multiple times to flatten the thickness dimension and make the blank regular.

[0067] 5. Final blank drawing and shaping process

[0068] a. Tooling preheating: All parts of the hammer, anvil, and fixtures that come into contact with the billet should be preheated; preheating temperature 200-300℃;

[0069] b. Forging dimensions:

[0070] The intermediate billet produced in the previous step is used to extend the rod of the "Y"-shaped billet to 740mm (length) × 110mm (width) × 190mm (thickness) by free forging. At the same time, during pressing, process steps need to be forged out of the billet rod. Finally, the billet is straightened and shaped to obtain a forging billet with the same flow lines as the raw material.

[0071] The asymmetric "Y"-shaped titanium alloy forging blanks produced by this process are dimensionally accurate and regularly shaped. The production process only requires 3 to 4 heat treatments, which simplifies the production process of this type of forging blank and shortens the production cycle. At the same time, the forgings produced have uniform microstructure and consistent flow lines, which meet product requirements and are suitable for widespread use.

Claims

1. A method for forming an asymmetric "Y"-shaped titanium alloy forging blank for aerospace applications, the asymmetric "Y"-shaped titanium alloy forging blank comprising a head and a rod, wherein, The head has two asymmetrical arms with rounded transitions at the base, characterized by including: Step 1: Material cutting: Determine the weight of the bar stock based on the weight of the forging. The weight of the bar stock is: weight of forging + weight of forging × 15% to 25%; Step 2: Heating the bar stock: Select an electric furnace with an accuracy of ±10℃ for heating. The heating temperature should be 30℃~50℃ below the phase change point. When heating cold material, the holding time coefficient should be 0.6~1.0min / mm. Step 3: Pre-forge the heated bar stock to obtain a preform, wherein the preform is a stepped slab of equal thickness; using a free forging press or a high-speed forging machine, first flatten the bar stock as a whole, then divide and elongate it, and forge it into a stepped slab of equal thickness. The stepped slab of equal thickness has a wide cross-section at one end and a narrow cross-section at the other end. The cross-sectional ratio of the wide cross-section to the narrow cross-section of the stepped slab should be greater than or equal to 1.5; the length-to-thickness ratio of the wide cross-section should be less than or equal to 2. Step 4: Using a die and pressure plate, the preform is forged to obtain an intermediate billet. The longitudinal section of the die cavity is "Y"-shaped, and the "Y"-shaped rod is square or rectangular. The rod is designed with a draft angle of 0.5° to 2°. The angles of the two inclined surfaces of the "Y"-shaped head are the same as the angles of the forging blank. The transition area between the rod and the head of the cavity is chamfered with R100 to R150. The pressure plate is designed with a semi-circular or curved cross-section. The radius of the pressure plate cross-section is larger than the radius of the arc at the root of the two arms of the forging blank. The length of the pressure plate is 100mm larger than the thickness dimension of the billet. The stepped slab of uniform thickness forged in step three is pressed in the thickness direction of the head, with a pressing amount of 1 / 2 to 1 / 3 of the thickness. Then, the stepped slab is placed vertically into the mold, with the length of the stepped slab corresponding to the longitudinal direction of the mold. The length of the head is pressed using a free forging hammer anvil. The head is then divided and eccentrically pressed so that the width of the stepped slab head is the same as the size of the head of the "Y"-shaped cavity of the mold. The pressing amount is the difference in length between the two arms of the forging blank. The intermediate blank is obtained by pressing the arc at the connection of the two arms of the asymmetrical "Y"-shaped forging blank using a pressure plate. Step 5: Lengthen and shape the intermediate billet rod to obtain the forging blank.

2. The method according to claim 1, characterized in that, In step four, the billet is removed from the mold multiple times during the forging process to flatten the thickness and make the billet regular.

3. The method according to claim 2, characterized in that, Step five, specifically: elongate the rod portion of the "Y"-shaped intermediate billet to the required size of the billet, to obtain a billet of an asymmetric "Y"-shaped titanium alloy forging with the same streamline as the raw material.

4. The method according to claim 3, characterized in that, In step four, the overall shape of the mold is a cube, with the longitudinal dimension smaller than the size of the forging blank, and the thickness being the sum of the thickness of the stepped slab blank and the thickness of the mold wall on both sides, with the mold wall thickness being 150-200mm; the transverse dimension is 50-100mm larger than the maximum width of the cavity "Y" shape on one side.

5. The method according to claim 1, characterized in that, In step four, the heating parameters before forging are as follows: the heating equipment is an electric furnace with an accuracy of ±10℃, the heating temperature is 30℃~50℃ below the phase transformation point, the holding time coefficient for heating cold material is 0.6~1.0min / mm, and the holding time coefficient for hot material returning to the furnace is 0.3~0.5min / mm.

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