Forming method of asymmetric Y-shaped titanium alloy forge piece blank for aviation

Abstract

The invention belongs to the field of hot working forming of metal materials, and particularly relates to a forming method of an asymmetric Y-shaped titanium alloy forge piece blank for aviation. By designing a special forming moulding bed and utilizing an eccentric pressing method, two asymmetric Y-shaped support arms with different lengths are forged, the main deformation process is realized by virtue of the moulding bed, the controllability of the production process is high, the dimensional precision is easy to guarantee, the process completion quality is high, the blank finish forging temperature can be effectively guaranteed, the material structure uniformity is improved, and meanwhile, the production cost is reduced. The streamline of the produced forge piece blank is distributed along the profile of the forge piece, the mechanical properties of the final forge piece in all directions are guaranteed, the forge piece waste rate is reduced, and the material utilization rate and the production efficiency are improved.

Description

Technical Field

[0001] The invention belongs to the field of hot processing and forming of metal materials, and in particular relates to a forming method of an asymmetric "Y"-shaped titanium alloy forging blank for aviation. Background Art

[0002] Titanium alloys have the characteristics of low density and high specific strength, and are widely used in aviation, aerospace, weapons and other fields. The strength of titanium alloys is comparable to that of general high-strength structural steels and high-temperature alloys, but their density is only about 57% of steel and about 55% of high-temperature alloys, with higher specific strength. The density of aluminum alloys and magnesium alloys is lower, only about 60% and 40% of titanium alloys, but their tensile strength is less than 1 / 3 of that of titanium alloys. This is also the main reason why the use of aluminum alloys and steel in advanced fighters and engines is gradually shrinking, while the use of titanium alloys is constantly increasing.

[0003] In recent years, with the rapid development of the world's aviation industry, higher requirements have been put forward for the use and performance of aircraft, and some high-strength titanium alloys have been widely used, especially in aircraft structural parts. Some large-sized long rod-type structural parts, due to their complex shapes, usually need to be forged into forging blanks first, and then die forged to obtain the final shape of the forgings. At present, for the forging of complex-shaped structural blanks, especially for products with asymmetric structures, the method of free forging N-fire upsetting, drawing and shaping is adopted, where N is the number of forging fires. For complex-shaped parts, this method requires a large margin in the area where the blank cannot be shaped when designing the blank, and the size is irregular, the consistency is poor, the number of fires consumed is large, the material utilization rate is low, and the factory production efficiency is affected. 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 asymmetric titanium alloy structural blanks to achieve the purpose of efficiently producing such products. Summary of the invention

[0005] Purpose of the invention: To provide a method for forming an asymmetric "Y"-shaped titanium alloy forging blank for aviation use, to solve the problem of difficulty in forming an asymmetric "Y"-shaped titanium alloy forging blank, and to improve material utilization and factory production efficiency.

[0006] Technical solution:

[0007] A forming method of an asymmetric "Y"-shaped titanium alloy forging blank for aviation, wherein the asymmetric "Y"-shaped titanium alloy forging blank comprises a head and a rod, wherein the root of the two asymmetric arms of the head has an arc transition, comprising:

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

[0009] Step 2: Heating the bar:

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

[0011] Step 3: pre-forging the heated bar material to obtain a preform, wherein the preform is a step slab with equal thickness;

[0012] Using a free forging press or a fast forging press, the bar is first flattened as a whole, and then divided and stretched, and forged into step slabs of equal thickness. One end of the step slab of equal thickness has a wide section, and the other end has a narrow section;

[0013] Step 4: Use the die and the pressing plate to forge the preform to obtain the intermediate blank:

[0014] The step slab of equal thickness forged in step 3 is pressed in the thickness direction of the head, and the pressing amount is 1 / 2 to 1 / 3 of the thickness;

[0015] Then put the step slab into the mold vertically, the length of the step slab corresponds to the longitudinal direction of the mold, and the length of the head is pressed with a free forging hammer anvil;

[0016] The head is divided and eccentrically pressed to make the width of the step slab head the same as the head size of the "Y"-shaped cavity of the tire mold, and the pressing amount is the length difference between the two arms of the forging blank;

[0017] The arc shape of the connection between the two arms of the asymmetric "Y"-shaped forging blank is pressed by a pressing plate to obtain an intermediate blank;

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

[0019] Preferably, in step 4, the blank can be taken out of the mold several times during the forging process to level the thickness dimension and make the blank regular.

[0020] Preferably, step five is specifically:

[0021] The rod of the "Y"-shaped intermediate billet is stretched to the required size of the blank, so as to obtain an asymmetric "Y"-shaped titanium alloy forging blank whose flow line is consistent with that of 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 slab and the thickness of the mold wall on both sides, and the mold wall thickness is 150 to 200 mm; the lateral dimension is 50 to 100 mm larger than the maximum dimension of the "Y"-shaped width of the cavity on one side.

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

[0024] Preferably, in step 4, the pressing plate is designed to have a semicircular cross section or a curved cross section, the cross-sectional radius of the pressing plate is larger than the arc radius of the roots of the two arms of the forging blank, and the length of the pressing plate is 100 mm larger than the dimension of the blank in the thickness direction.

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

[0026] Preferably, in step 4, the heating parameters before forging satisfy:

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

[0028] Beneficial effects:

[0029] The present invention provides a forming method for an asymmetric "Y"-shaped titanium alloy forging blank for aviation use, which has the advantages that when the forging blank is forged, a special forming die is designed, and an eccentric pressing method is used to forge two asymmetric "Y"-shaped arms of different lengths, the main deformation process is realized by the die, the production process has high controllability, the dimensional accuracy is easy to ensure, the process completion quality is high, the final forging temperature of the blank can be effectively guaranteed, and the uniformity of material structure is improved. At the same time, the streamlines of the produced forging blank are distributed along the contour of the forging, which ensures the mechanical properties of the final forging in all directions, reduces the scrap rate of the forging, and improves the material utilization rate and production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the outline of the asymmetric "Y" shaped forging blank;

[0031] Figure 2 Step slabs of equal thickness;

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

[0033] Figure 4 Schematic diagram of the asymmetric "Y"-shaped forging blank forming die. DETAILED DESCRIPTION

[0034] A method for forming an asymmetric "Y"-shaped titanium alloy forging blank for aviation use, the shape Figure 1 As shown, the method includes the following steps:

[0035] Step 1: Cutting process

[0036] The blanking weight is determined according to the weight of the forging. The blanking weight can be: forging weight + forging weight × 15% to 25%. Among them, the material allowance coefficient can be selected within the range of 15% to 25%, which is determined according to the complexity of the forging shape and the production number.

[0037] Step 2: Heating process

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

[0039] Step 3: Preform forging process

[0040] Use a free forging press or a fast forging machine to flatten the bar as a whole, divide it into sections, stretch it, and forge it into step slabs of equal thickness. Figure 2 The step slab of equal thickness has a wide section at one end and a narrow section at the other end. The cross-sectional ratio of the wide section to the narrow section should be greater than or equal to 1.5; the length to thickness ratio of the wide section should be less than or equal to 2.

[0041] Step 4: Intermediate billet forging process

[0042] like Figure 3 and Figure 4, Molding mold design: The overall shape of the mold is a cube. The longitudinal size is determined according to the required blank size. The thickness is the sum of the step slab thickness and the mold wall thickness on both sides. To ensure the strength of use, the mold wall thickness is generally 150-200mm. Eccentric pressing is required in the transverse direction. In order to prevent instability, the transverse dimension of the mold design should be 50-100mm larger than the maximum width of the "Y"-shaped cavity on one side. The longitudinal section of the cavity is in the shape of a "Y". When the "Y"-shaped narrow section of the cavity is designed, the section can be square or rectangular, which is determined according to the actual section of the product rod. It should be noted 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 takes a smaller value. When the ratio of the rod length to the rod thickness is less than 3, the draft angle takes a larger value. When the "Y"-shaped wide section is designed, the bevel angle of the two arms is determined according to the design angle of the blank. During pressing, the blank is ensured to fit the bevel of the tire mold. At the same time, the transition area between the rod and the head is chamfered R100 to R150 to prevent the blank from folding in this area.

[0043] Press plate design: The press plate is designed to have a semicircular cross-section or a curved cross-section. The size is determined according to the size of the forging blank. The length of the press plate should be about 100mm greater than the dimension in the thickness direction of the blank.

[0044] For the step slab of equal thickness forged in step three, first press the dimension of the wide section in the thickness direction, press down by about 1 / 3, then put the slab upright into the mold, the length of the step slab corresponds to the longitudinal direction of the mold, use the free forging hammer anvil to press the length of the wide section, and according to the product rough design, use the pressing plate mentioned in step four to divide the material, press eccentrically, so that the width of the billet is close to the size of the upper port of the "Y"-shaped cavity of the mold, and the pressing amount is determined according to the length difference of the two arms of the "Y"-shaped billet. After pressing, use a pressing plate with a semicircular cross-section or a curved cross-section to press out the arc bottom of the connection between the two walls of the "Y"-shaped billet. At this point, the head of the "Y"-shaped billet has been formed. During the forging process, the billet can be taken out of the mold many times to level the dimension in the thickness direction and make the billet regular.

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

[0046] The intermediate blank obtained in step 4, which is similar in shape to the forging blank, is free forged to lengthen the narrow section of the "Y"-shaped blank to the required size of the blank, thereby obtaining an asymmetric "Y"-shaped titanium alloy forging blank whose streamline is consistent with that of the raw material.

[0047] In step 4, the pre-forging heating parameters are:

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

[0049] Example:

[0050] The outer cylinder forging for a certain type of aircraft is made of TC32 alloy and is produced using Φ300 round bar stock. The forging is a typical asymmetric "Y"-shaped forging with a total length of nearly 1150mm. The length difference between the two arms of the "Y" shape is about 200mm. The difficulty in blank production lies in the need to accurately divide the materials during the forging of the two arms of the asymmetric "Y" shape and strictly control the size to ensure that the forging is fully filled during die forging. The traditional blank production method is to first beat the bar stock into a plate shape, then divide the material step by step, and forge it to the required size by pinching and pulling the material. This method has poor dimensional control accuracy and many production times, so the efficiency is low. After multiple verifications, the present invention is produced according to the following process.

[0051] Process method:

[0052] 1. Cutting process

[0053] The forging weighs 147.5Kg. Due to the need to separate the forging blank and forge it through multiple rounds, the excess coefficient is 25% when cutting the material. The calculated cutting weight is 184.5Kg, and the converted cutting size is Φ300mm×580mm.

[0054] 2. Heating process

[0055] When forging the blank, it is heated at the phase transformation point. The electric furnace with an accuracy of ±10°C can meet the requirements. The material of this product is TC32 alloy, so the heating temperature is selected to be 40°C below the phase transformation point. The cold material heating and insulation coefficient is implemented at 0.8min / mm, and the hot material returning to the furnace insulation time coefficient is implemented at 0.5min / mm. If there are no folding and crack defects on the surface, the hot material can be continuously returned to the furnace for production.

[0056] 3. Preform forging process

[0057] a. Preheating of tooling: The parts of the hammer, anvil, and fixture that contact the blank should be preheated at a temperature of 200-300°C;

[0058] b. Forging size:

[0059] Φ300mm×580mm bar is flattened as a whole, squared and shaped into a slab with a length of 785mm, a width of 350mm and a thickness of 190mm. The material is divided at about 250mm in the length direction of the billet, and the 535mm end is stretched to 555mm (length) × 200mm (width) × 190mm (thickness). It should be noted that the length dimension after stretching does not include the transition part of about 100mm between the 350mm width dimension and the 200mm width dimension. The preform after forging is a step slab of equal thickness. Figure 2 Shape shown.

[0060] 4. Intermediate billet forging

[0061] Molding mold design:

[0062] The designed longitudinal dimension of the mold is 650mm, the maximum width of the blank is 580mm, the designed transverse dimension of the mold is 780mm, and the height dimension of the mold is 600mm. The rod of the "Y"-shaped cavity is designed to be square according to the requirements of the blank, with a size of 200mm and a draft angle of 1.5°. The bevel 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 are fully fitted during pressing. At the same time, the transition area between the rod and the head is chamfered R100.

[0063] Pressure plate design: The pressure plate is designed as a semicircular pressure plate, which is made of round bar material with a size of Φ150mm×210mm and is divided into two parts along the axial direction for use.

[0064] a. Preheating of tooling: The parts of the hammer, anvil, and fixture that contact the blank should be preheated; the preheating temperature is 200-300℃;

[0065] b. Forging size:

[0066] For the step slab of equal thickness, first press the thickness dimension of one end of the wide section to 130mm. After shaping, put the billet upright into the forming mold, first press it down as a whole to make the rod fill the cavity, and at the same time press the length dimension of the billet to 220mm from the upper end face of the mold. Then divide the material at a distance of 110mm from one end of the billet, and press the 440mm part down about 130mm along the length direction as a whole. At this point, the asymmetric "Y"-shaped basic structure has been formed, and then use a pressing plate to forge the arc bottom of the connection between the two walls of the "Y"-shaped billet. During the forging process, take the billet out of the mold many times to level the thickness dimension to make the billet regular.

[0067] 5. Final blank stretching and shaping process

[0068] a. Preheating of tooling: The parts of the hammer, anvil, and fixture that contact the blank should be preheated; the preheating temperature is 200-300℃;

[0069] b. Forging size:

[0070] The intermediate billet produced in the previous step is free forged to lengthen the rod of the "Y"-shaped billet to 740mm (length) × 110mm (width) × 190mm (thickness). At the same time, it is necessary to forge a process step on the billet rod during pressing. Finally, the billet is straightened and shaped to obtain a forging blank consistent with the flow line of the raw material.

[0071] The asymmetric "Y"-shaped titanium alloy forging blanks produced by this process method have precise dimensions and regular shapes, and only require 3 to 4 production fires, which simplifies the production process of forging blanks of this type of shape and shortens the production cycle. At the same time, the forgings produced have uniform structure and consistent streamlines, which meet product requirements and are suitable for popularization and use.

Claims

1. A method for forming an asymmetric "Y"-shaped titanium alloy forging blank for aviation, wherein the asymmetric "Y"-shaped titanium alloy forging blank comprises a head and a rod, wherein: The head has two asymmetric arms with arc transition at the root, which is characterized by: Step 1: Cutting: Determine the weight of the bar stock according to the weight of the forging. The weight of the bar stock can be: forging weight + forging weight × 15% to 25%; Step 2: Heating the bar: The heating equipment is an electric furnace with an accuracy of ±10°C. The heating temperature can be 30°C to 50°C below the phase change point. When heating cold materials, the holding time coefficient is 0.6 to 1.0 min / mm. Step 3: pre-forging the heated bar material to obtain a preform, wherein the preform is a step slab with equal thickness; Using a free forging press or a fast forging press, the bar is first flattened as a whole, and then divided and stretched, and forged into step slabs of equal thickness. One end of the step slab of equal thickness has a wide section, and the other end has a narrow section; Step 4: Use the die and the pressing plate to forge the preform to obtain the intermediate blank: The step slab of equal thickness forged in step 3 is pressed in the thickness direction of the head, and the pressing amount is 1 / 2 to 1 / 3 of the thickness; Then put the step slab into the mold vertically, the length of the step slab corresponds to the longitudinal direction of the mold, and the length of the head is pressed with a free forging hammer anvil; The head is divided and eccentrically pressed to make the width of the step slab head the same as the head size of the "Y"-shaped cavity of the tire mold, and the pressing amount is the length difference between the two arms of the forging blank; Use a pressing plate to press out the arc shape at the connection between the two arms of the asymmetric "Y"-shaped forging blank to obtain an intermediate blank; Step 5: The intermediate billet rod is stretched and shaped to obtain a forging blank.

2. The method according to claim 1, characterized in that In step 4, the blank can be taken out of the die several times during the forging process to level the thickness dimension and make the blank regular.

3. The method according to claim 2, characterized in that Step 5: The rod of the "Y"-shaped intermediate billet is stretched to the required size of the blank, so as to obtain an asymmetric "Y"-shaped titanium alloy forging blank whose flow line is consistent with that of the raw material.

4. The method according to claim 3, characterized in that: In step 4, 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 slab and the thickness of the mold wall on both sides, and the mold wall thickness is 150 to 200 mm; the lateral dimension is 50 to 100 mm larger than the maximum dimension of the "Y"-shaped width of the cavity on one side.

5. The method according to claim 4, characterized in that In step 4, the longitudinal section of the tire mold cavity is in the shape of "Y", 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 takes a smaller value, and when the ratio of the rod length to the rod thickness is less than 3, the draft angle takes a larger value. The two inclined surface angles of the "Y"-shaped head are the same as the angles of the forging blank, and the transition area between the cavity rod and the head is chamfered R100 to R150.

6. The method according to claim 5, characterized in that In step 4, the pressing plate is designed to have a semicircular cross section or a curved cross section. The cross-sectional radius of the pressing plate is larger than the arc radius of the roots of the two arms of the forging blank. The length of the pressing plate is 100 mm larger than the dimension of the blank in the thickness direction.

7. The method according to claim 6, characterized in that In step three, the cross-sectional ratio of the wide section to the narrow section of the step slab should be greater than or equal to 1.5; the length to thickness ratio of the wide section should be less than or equal to 2.

8. The method according to claim 7, characterized in that In step 4, the heating parameters before forging meet the following requirements: The heating equipment is an electric furnace with an accuracy of ±10°C. The heating temperature can be: 30°C ~ 50°C below the phase change point. When heating cold materials, the insulation time coefficient is 0.6 ~ 1.0min / mm, and when returning hot materials to the furnace, the insulation time coefficient is 0.3 ~ 0.5min / mm.

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