A forging method for TC4 titanium alloy three-way pipe joint forging

Abstract

The present invention belongs to the field of forging hot working, and specifically relates to a forging method for TC4 titanium alloy three-way pipe joint forgings. By designing the rough shape, reasonably allocating the deformation amount, and designing a one-die, multi-cavity forging die, a single-fire, multi-step forging of titanium alloy small-die forging is achieved. By removing the α layer on the forging surface through chemical milling, and providing appropriate key process parameters such as forging heating temperature, deformation amount, insulation coefficient, cooling method, and heat treatment, TC4 three-way pipe joint forgings with uniform structure and excellent performance can be stably produced. This method realizes the application and promotion of technologies such as the design, die design, and manufacturing process of aviation forgings with similar structures, improves process stability, increases production efficiency, and reduces manufacturing costs.

Description

Technical Field

[0001] The invention belongs to the field of forging hot processing, and in particular relates to a forging method for a TC4 titanium alloy three-way pipe joint forging. Background Art

[0002] TC4 is a medium-strength α-β two-phase titanium alloy with excellent heating process performance. It is widely used in the aviation and aerospace industries. It is mainly used to manufacture engine fans, compressor discs and blades, as well as important load-bearing structural parts such as beams, joints and bulkheads in aircraft structures. At present, my country's fifth-generation aircraft have generally used TC4 titanium alloy to replace structural steels such as 30CrMnSiA, which can achieve a weight reduction of about 30%. TC4 titanium alloy three-way pipe joints are important precision structural parts for aircraft pipelines. The forging surface quality requirements are high, the dimensional accuracy is high, and there are non-machined surfaces. The surface requirements do not allow the existence of α layer. However, due to the sensitivity of titanium alloy forging temperature, high deformation resistance, and poor metal fluidity, it is difficult to fill the forging and the surface quality of the forging after die forging is poor. At the same time, due to the structural characteristics of the three-way pipe joint, it is easy to have uneven deformation during the forging process, resulting in uneven local structure. The conventional forging process in the factory is: α+β die forging, heating temperature: T β -(20~40)℃, mold temperature: 200℃~250℃, deformation per fire controlled at 20%~50%, general die forging is formed by at least 2 fires, and the production process requires multiple grinding, repairing, corrosion spraying, etc. At present, the factory has a wide variety of TC4 titanium alloy tee pipe joint forgings, the production process is cumbersome, the cycle is long, the cost is high, and it is difficult to meet market demand. Summary of the Invention

[0003] Purpose of the invention: To provide a forging method for TC4 titanium alloy three-way pipe joint forgings, thereby improving process stability, increasing production efficiency and reducing manufacturing costs.

[0004] Technical solution:

[0005] A forging method for a TC4 titanium alloy tee pipe joint forging includes a body and three joints of different diameters extending outward from the body, the axes of the three joints being in the same plane. A wrench platform is provided on the body, and the length and width of the wrench platform are □F. The tee pipe joint forging is symmetrical along the plane containing the axes of the three joints. The three joints have conical transitions at their connections with the body. The coaxial diameters of the first joint and the second joint are ΦA and ΦB, respectively. The axis of the third joint is perpendicular to the axes of the first and second joints. The diameter of the third joint is ΦC. The distance between the end face of the third joint and the axes of the first and second joints is Lb. The distance between the end faces of the first and second joints is La.

[0006] The method comprises:

[0007] Step 1: Determine the shape and size of the pre-forged blank 1 according to the shape and size of the forging;

[0008] Step 2: Determine the shape and size of the pre-forged blank 2 according to the shape and size of the forging;

[0009] Step 3: Forging the bar material with a forging die to obtain a forging, wherein the forging die cavity includes: pre-forging cavity 1, pre-forging cavity 2, and final forging cavity 3. The dimensions of the pre-forging cavity 1 and the pre-forging cavity 2 are the same as those of the pre-forging rough shape 1 and the pre-forging rough shape 2. The dimension of the final forging cavity 3 is the overall forging dimension multiplied by the thermal coefficient of 1.008 to 1.01 plus the milling amount. The three cavities are evenly distributed in the center of the die, consisting of an upper die and a lower die, and the parting surface is located at the center line of the cross section of the three cavities.

[0010] Preferably, in step 1, the pre-forged rough shape 1 includes three joints, the end diameters of the three joints are the same and are the maximum diameters of the three joints of the forging, the first joint and the second joint are transitioned to the third joint on one side by two upper and lower inclined planes Y, and the other side of the first joint and the second joint are transitioned by two upper and lower inclined planes X, and X and Y are tangent to ΦA.

[0011] Preferably, in step 1, the distance between the end face of the third joint of the pre-forged rough shape 1 and the axis of the first joint and the second joint is Lb1, which satisfies: Lb1 = Lb-(1-2),

[0012] The distance Lc1 between the axis of the first joint or the second joint of the pre-forged rough form 1 and the intersection of the upper and lower tangents satisfies: Lc1 = (ΦC1 / 2) + (2~3).

[0013] Preferably, in step 1, the concave fillet where ΦC1 intersects the Y curved surface is R10-R15, and the remaining convex fillets are R3-R5, and ΦD is the diameter of the bar material used.

[0014] Preferably, in step 2, the pre-forged shape 2 includes three joints of different diameters, the axes of the three joints are in the same plane, circular wrench blocks are provided at the connections of the three joints, the radius of the circular wrench block is SRF, the tee pipe joint forging is symmetrical along the plane where the axes of the three joints are located, the first joint, the second joint and the third joint are connected with rounded corners, the coaxial diameters of the first joint and the second joint are ΦA2 and ΦB2 respectively, the axis of the third joint is perpendicular to the axes of the first joint and the second joint, the diameter of the third joint is ΦC2, and the distance between the end face of the third joint and the axes of the first joint and the second joint is Lb2.

[0015] Preferably, in step 2, the diameter of the third joint is ΦC2, which satisfies: ΦC2=ΦA2=ΦA+(2-3), assuming that ΦA is the maximum of the three diameters of ΦA, ΦB, and ΦC.

[0016] The distance La2 between the first joint and the second joint end face of the pre-forged rough shape 2 satisfies: La2 = La-(1-2),

[0017] The distance between the end face of the third joint and the axis of the first joint and the second joint is Lb2, which satisfies: Lb2 = Lb-(1-2),

[0018] The radius of the circular wrench table is SRF, which satisfies: SRF = F / 2.

[0019] Preferably, in step 2, the concave rounded corners where ΦC2 and ΦA2 intersect are R5 to R8, and the remaining convex rounded corners are R3 to R5.

[0020] Preferably, in step 3, the milling amount is calculated as 0.1 to 0.2 mm per side.

[0021] Preferably, in step 3, the forging heating temperature is: T β -(35~40)℃, holding time: 0.8~1.5mm / min, mold temperature: 300~350℃, forging process: 1 fire divided into 3 strikes, overall deformation: 60%~85%, transfer time ≤15s, cooling method: air cooling.

[0022] Beneficial effects:

[0023] The TC4 titanium alloy tee pipe joint forging method uses a single-fire, multi-step die forging process. Chemical milling is used to remove the α layer on the forging surface, followed by vacuum furnace annealing. This shortens production cycles, reduces production costs, and improves material utilization. The result is a tee pipe joint forging with uniform structure and excellent overall performance. This also promotes the application and promotion of technologies for similar aviation forgings, die design, and manufacturing processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The top view and left view of the forging;

[0025] Figure 2 It is the main view and left view of the wild shape 1;

[0026] Figure 3 It is the top view and left view of the wild shape 2;

[0027] Figure 4 This is a top view of the mold. DETAILED DESCRIPTION

[0028] The present invention designs a forging method for TC4 titanium alloy three-way pipe joint forgings. By designing the rough shape, reasonably allocating the deformation amount, and designing a one-die multi-cavity forging die, the single-fire multi-step forging of titanium alloy small-die forging is realized. The α layer on the surface of the forging is removed by chemical milling. The key process parameters such as appropriate forging heating temperature, deformation amount, thermal insulation coefficient, cooling method, and heat treatment are provided. TC4 three-way pipe joint forgings with uniform structure and excellent performance can be stably prepared, and the application and promotion of technologies such as aviation forging design, die design, and manufacturing process of similar structures are realized, thereby improving process stability, increasing production efficiency, and reducing manufacturing costs.

[0029] A forging method for a TC4 titanium alloy three-way pipe joint forging comprises: 1) forging rough shape design; 2) die design; 3) forging; 4) chemical milling; and 5) vacuum furnace annealing (hydrogen removal) treatment, ultimately producing a forging with structure and performance meeting standard requirements.

[0030] The forging rough shape design:

[0031] Based on the structural characteristics of the tee pipe joint forging, a pre-forged rough shape is designed. The tee pipe joint forging includes a body and three joints of different diameters (ΦA, ΦB, ΦC) extending outward from the body. The axes of the three joints are in the same plane. A wrench platform with a length and width of □F is provided on the body. The tee pipe joint forging is symmetrical along the plane where the axes of the three joints are located, and the three joints have a conical transition at the connection with the body. The coaxial diameters of the first joint and the second joint are ΦA and ΦB respectively. The axis of the third joint is perpendicular to the axes of the first and second joints. The diameter of the third joint is ΦC. The distance between the end face of the third joint and the axes of the first and second joints is Lb; the distance between the end faces of the first and second joints is La.

[0032] The pre-forged rough shape is divided into pre-forged rough shape 1 and pre-forged rough shape 2. Figure 1 As shown, the wild shape 1 is as Figure 2 As shown, the wild shape 2 is as Figure 3 As shown, the pre-forged rough shape 1 includes three joints, the end diameters of the three joints are the same and are the maximum diameters of the three joints of the forging, the first joint and the second joint are transitioned to the third joint on one side by two upper and lower inclined planes Y, and the other sides of the first joint and the second joint are transitioned by two upper and lower inclined planes X: that is, the joint diameter ΦC1 of the pre-forged rough shape 1 satisfies: ΦC1 = ΦA (assuming ΦA is the maximum of the three diameters ΦA, ΦB, and ΦC),

[0033] The distance between the end face of the third joint of the pre-forged rough shape 1 and the axis of the first joint and the second joint is Lb1, which satisfies: Lb1 = Lb-(1-2);

[0034] The distance Lc1 between the axis of the first joint or the second joint of the pre-forged rough shape 1 and the intersection of the upper and lower tangents satisfies:

[0035] Lc1=(ΦC1 / 2)+(2~3), X, Y are tangent to ΦA, the concave fillet where ΦC1 intersects with the Y surface is R10~R15, and the other convex fillets are R3~R5, ΦD is the diameter of the bar used;

[0036] Pre-forged wild form 2:

[0037] Pre-forged rough form 2 includes three joints of different diameters (ΦA2, ΦB2, ΦC2). The axes of the three joints are in the same plane. A circular wrench block with a radius of SRF is provided at the joint connection. The tee pipe joint forging is symmetrical along the plane containing the axes of the three joints. The joints of the first, second, and third joints have rounded corners. The coaxial diameters of the first and second joints are ΦA2 and ΦB2, respectively. The axis of the third joint is perpendicular to the axes of the first and second joints. The diameter of the third joint is ΦC2, and the distance between the end face of the third joint and the axes of the first and second joints is Lb2.

[0038] The diameter of the third joint is ΦC2, which satisfies:

[0039] ΦC2=ΦA2=ΦA+(2~3) (assuming ΦA is the maximum value of the three diameters of ΦA, ΦB, and ΦC),

[0040] The distance La2 between the end faces of the first joint and the second joint of the pre-forged rough shape 2 satisfies:

[0041] La2=La-(1~2),

[0042] Lb2 = Lb-(1-2), SRF = F / 2, the concave fillet of the intersection of ΦC2 and ΦA2 is R5-R8, and the other convex fillets are R3-R5;

[0043] The forging die design:

[0044] To realize the one-fire multi-step forging process of titanium alloy small die forging, extremely high requirements are placed on the forging die design. During the design, it is necessary to consider that the pre-forging and final forging should not have defects such as folding, pinching, and insufficient filling. At the same time, the distribution problem of deformation amount must be met to prevent uneven organization caused by uneven deformation. At the same time, due to the small size of small die forgings, the surface temperature of the forgings loses quickly during the forging process. It is easy for the forging temperature to be too low during multi-step forging, resulting in problems such as cracks, die sticking, and unqualified organization in the forgings.

[0045] Prepare forging die, the forging die adopts 1 die 3 cavities as Figure 4As shown, the mold cavities are pre-forging cavity 1, pre-forging cavity 2, and final forging cavity 3. The sizes of pre-forging cavity 1 and pre-forging cavity 2 are consistent with the sizes of rough shape 1 and rough shape 2 mentioned above. The size of final forging cavity 3 is the overall size of the forging multiplied by the thermal coefficient (1.008~1.01), and then compensated for the milling amount. The milling amount is calculated as 0.1~0.2mm per side. The three cavities are evenly distributed in the center of the mold and consist of an upper mold and a lower mold. The parting surface is located at the center line of the cross section of the three cavities. This type of parting is a plane parting. The mold size is based on the size of the equipment mold base cavity and the maximum outline size of the forging.

[0046] The forging process:

[0047] Forging heating temperature: T β -(35~40)℃, holding time: 0.8~1.5mm / min, die temperature: 300~350℃. Forging process: 1 fire divided into 3 strikes, deformation: 60%~85%, transfer time ≤15s, cooling method: air cooling.

[0048] Fast forging transfer times combined with high die temperatures effectively guarantee final forging temperatures, reduce temperature loss and deformation resistance during forging, and enhance metal fluidity. Simultaneously, single-fire die forging shortens the forging cycle, reduces human factors, improves process stability, ensures forging consistency, and reduces costs while increasing efficiency.

[0049] The chemical milling process:

[0050] TC4 tee pipe joint forgings have non-machined surfaces, and the surface requirements do not allow the presence of an α layer. The present invention removes the surface α layer through a chemical milling process. The milling depth is controlled to 0.10-0.15 mm per side. The milling solution is: HF: 52-70 g / L, HNO3: 106-136 g / L, and the temperature is: 25-35°C. The milling time t = e / 2V, where V is the milling rate, mm / min; e is the milling depth, mm.

[0051] Deashing: This removes residual reactants from the forging surface, reduces surface roughness, and improves surface quality. Solution concentration: HNO3: 288-356g / L, HF: 15.5-29g / L, temperature: 25-35°C, time: 20-30s.

[0052] The heat treatment process:

[0053] TC4 tee pipe joint forgings are at risk of hydrogen absorption after chemical milling, and therefore require dehydrogenation annealing according to standards. Conventional annealing for TC4 forgings involves heating to 700-850°C and holding for 60-120 minutes. Using a vacuum furnace for annealing combines conventional and dehydrogenation annealing processes, effectively removing hydrogen and reducing the risk of hydrogen absorption. Vacuum furnace annealing also prevents secondary contamination (alpha layer) of the forgings, reducing production costs.

[0054] The forging equipment is an electric screw press, the heating furnace is a high-temperature electric converter, and the forging die is made of a hot-working die steel H13 with good overall plasticity, toughness, wear resistance, hardenability and machinability.

[0055] The chemical milling process equipment is a titanium alloy chemical surface treatment line, and the process flow includes: alkali washing (temperature: 71-75°C, time: 5-10 min) → 2 water washings (room temperature, time: 2-3 min) → chemical milling (temperature: 25-35°C, time: t=e / 2V) → dust removal (temperature: 25-35°C, time: 20-30s) → 2 water washings (room temperature, time: 2-3 min) → hot deionized water washing (temperature: 60-80°C, time: 2-4 min).

[0056] Example:

[0057] The present invention is further described in detail below through specific implementation examples:

[0058] TC4 titanium alloy three-way pipe joint, the forging adopts a one-fire multi-step die forging method.

[0059] Step 1: According to the structural characteristics of the tee pipe joint forging, rough shape 1: ΦC1 = ΦA (assuming ΦA is the maximum of the three diameters of ΦA, ΦB, and ΦC), Lb1 = Lb-1, Lc1 = (ΦC1 / 2) + 2, La1 = Lb1 + Lc1 = La + (2 + 3), X and Y are tangent to ΦD, the concave fillet where ΦC1 intersects with the Y surface is R15, and the other convex fillets are R4;

[0060] Shape 2: ΦC2 = ΦA2 = ΦA+2 (assuming ΦA is the maximum of the three diameters of ΦA, ΦB, and ΦC), La2 = La-1, Lb1 = Lb-1, SRF = F / 2, the concave fillet at the intersection of ΦC2 and ΦA2 is R5, and the remaining convex fillets are R3;

[0061] Step 2: Prepare a forging die. The forging die adopts 1 die and 3 cavities. The die cavities are pre-forging cavity 1, pre-forging cavity 2, and final forging cavity 3. The sizes of pre-forging cavity 1 and pre-forging cavity 2 are consistent with the sizes of rough shape 1 and rough shape 2 mentioned above. The size of final forging cavity 3 is the overall size of the forging multiplied by the thermal coefficient (1.008), and then compensated for the milling amount. The milling amount is calculated as 0.15mm per side. The three cavities are evenly distributed in the center of the die. It consists of an upper die and a lower die. The parting surface is located at the center line of the cross section of the three cavities. This type of parting is a plane parting. The die size is selected as 240×150×120 according to the size of the equipment die base cavity and the maximum outline size of the forging.

[0062] Step 3: Cutting process

[0063] Rod specifications: Φ30×38±1mm, both ends of the rod are chamfered R2 and the end surface is flat, steel sand shot blasting, corrosion, and spraying high-temperature glass lubricant protective agent.

[0064] Step 4: Forging

[0065] a. Heat the blank to (T β -40)℃, keep warm for 35-40 minutes, die temperature: 300-350℃, strike energy: pre-forging strike energy 20%, pre-forging strike energy 20%, final forging strike energy 40%, deformation: ~75%;

[0066] b. The entire forging transfer time is ≤15 seconds, completed in 1 fire;

[0067] c. Shot blasting, corrosion and repair of steel sand.

[0068] Step 5: Milling

[0069] The chemical milling solution is: HF: 52-70 g / L, HNO3: 106-136 g / L, temperature: 25-35°C. The chemical milling time t = e / 2V, where V is the chemical milling rate, mm / min; e is the chemical milling amount, which is controlled at 0.13 mm per side. For dust removal, the solution concentration is: HNO3: 288-356 g / L, HF: 15.5-29 g / L, temperature: 30-35°C, and time: 20-30 seconds.

[0070] Step 6: Heat Treatment

[0071] Annealing in vacuum furnace. Temperature: 800±10℃, holding time: 90±9 minutes, working vacuum degree ≤6.7×10 - 4 mbar, cool to below 50℃ with argon blower and then take out of the furnace for air cooling.

[0072] The forging equipment is an electric screw press, the heating furnace is a high-temperature electric converter, and the final forging die is H13.

[0073] The chemical milling process equipment is a titanium alloy chemical surface treatment line, and the process flow includes: alkali washing (temperature: 71-75°C, time: 5-10 min) → 2 water washings (room temperature, time: 2-3 min) → chemical milling (temperature: 25-35°C, time: t=e / 2V) → dust removal (temperature: 25-35°C, time: 20-30s) → 2 water washings (room temperature, time: 2-3 min) → hot deionized water washing (temperature: 60-80°C, time: 2-4 min).

[0074] The present invention adopts a die forging one-fire multi-step forging process, removes the α layer on the surface of the forging by chemical milling, and performs vacuum furnace annealing and other processes, thereby shortening the production cycle, reducing production costs, and improving material utilization, and can produce three-way pipe joint forgings with uniform structure and excellent comprehensive performance.

Claims

1. A forging method for a TC4 titanium alloy tee pipe joint forging, characterized in that: The tee pipe joint forging includes a body and three joints of different diameters extending outward from the body. The axes of the three joints are in the same plane. A wrench platform is provided on the body. The length and width of the wrench platform are □F. The tee pipe joint forging is symmetrical along the plane of the axes of the three joints. The three joints have conical transitions at the connection with the body. The coaxial diameters of the first joint and the second joint are ΦA and ΦB respectively. The axis of the third joint is perpendicular to the axes of the first and second joints. The diameter of the third joint is ΦC. The distance between the end face of the third joint and the axes of the first and second joints is Lb. The distance between the end faces of the first and second joints is La. The method comprises: Step 1: Determine the shape and size of the pre-forged blank 1 based on the shape and size of the forging. The pre-forged blank 1 includes three joints. The end diameters of the three joints are the same and are the maximum diameters of the three joints of the forging. The first joint and the second joint are transitioned to the third joint on one side through two upper and lower inclined planes Y. The other sides of the first joint and the second joint are transitioned through two upper and lower inclined planes X. X and Y are tangent to ΦA. Step 2: Determine the shape and size of the pre-forged blank 2 based on the shape and size of the forging. The pre-forged blank 2 includes three joints of different diameters. The axes of the three joints are in the same plane. A circular wrench block is provided at the connection of the three joints. The radius of the circular wrench block is SRF. The tee pipe joint forging is symmetrical along the plane where the axes of the three joints are located. The connection between the first joint, the second joint and the third joint has a rounded transition. Step 3: Forging the bar material with a forging die to obtain a forging, wherein the forging die cavity includes: pre-forging cavity 1, pre-forging cavity 2, and final forging cavity 3. The dimensions of the pre-forging cavity 1 and pre-forging cavity 2 are the same as those of the pre-forging rough shape 1 and pre-forging rough shape 2. The dimension of the final forging cavity 3 is the overall forging dimension multiplied by the thermal coefficient 1.008 to 1.01 plus the milling amount. The three cavities are evenly distributed in the center of the die, consisting of an upper die and a lower die. The parting surface is located at the center line of the cross section of the three cavities. The forging heating temperature is: T β -(35~40)℃, holding time: 0.8~1.5mm / min, mold temperature: 300~350℃, forging process: 1 fire divided into 3 strikes, overall deformation: 60%~85%, transfer time ≤15s, cooling method: air cooling.

2. The method according to claim 1, characterized in that In step 1, the distance between the end face of the third joint of the pre-forged rough shape 1 and the axis of the first joint and the second joint is Lb1, which satisfies: Lb1 = Lb-(1-2). The distance Lc1 between the axis of the first joint or the second joint of the pre-forged rough form 1 and the intersection of the upper and lower tangents satisfies: Lc1 = (ΦC1 / 2) + (2~3).

3. The method according to claim 2, characterized in that In step 1, the concave fillet where ΦC1 intersects the Y surface is R10 to R15, and the remaining convex fillets are R3 to R5. ΦD is the diameter of the bar used.

4. The method according to claim 1, wherein In step 2, the coaxial diameters of the first joint and the second joint of the pre-forged rough shape 2 are ΦA2 and ΦB2 respectively, the axis of the third joint is perpendicular to the axes of the first joint and the second joint, the diameter of the third joint is ΦC2, and the distance between the end face of the third joint and the axes of the first joint and the second joint is Lb2.

5. The method according to claim 4, characterized in that In step 2, the diameter of the third joint is ΦC2, which satisfies the following: ΦC2 = ΦA2 = ΦA + (2-3). Assuming that ΦA is the maximum of the three diameters of ΦA, ΦB, and ΦC, The distance La2 between the first joint and the second joint end face of the pre-forged rough shape 2 satisfies: La2 = La-(1-2), The distance between the end face of the third joint and the axis of the first joint and the second joint is Lb2, which satisfies: Lb2 = Lb-(1-2), The radius of the circular wrench table is SRF, which satisfies: SRF = F / 2.

6. The method according to claim 1, characterized in that In step 2, the concave fillets where ΦC2 and ΦA2 intersect are R5 to R8, and the remaining convex fillets are R3 to R5.

7. The method according to claim 1, characterized in that In step 3, the milling amount is calculated as 0.1 to 0.2 mm per side.

Images