Isothermal forming tool for large-wall-thickness complex-structure titanium alloy shell and wall thickness control method

Abstract

The invention relates to a large-wall-thickness complex-structure titanium alloy shell isothermal forming tool and a wall thickness control method, an integrated isothermal forming tool is designed, isothermal forming of a TC4 titanium alloy shell blank from a TC4 titanium alloy plate blank is achieved, the forming efficiency of the TC4 titanium alloy shell blank is greatly improved, the raw material utilization rate is greatly increased, and the production cost is reduced. And the manufacturing period and cost of the TC4 titanium alloy shell are reduced. Through precise design of the blank and the die and matching of reasonable isothermal forming temperature, hot pressing rate and other process parameters, the wall thickness thinning and pull crack phenomena in the isothermal forming process of the TC4 titanium alloy shell are eliminated, and the forming quality of the titanium alloy shell with the large wall thickness and the complex structure is guaranteed. Through vacuum annealing heat treatment before and after rough machining and reasonable rough machining contour design, residual stress in the TC4 titanium alloy shell blank is effectively eliminated, local deformation caused by stress release in the machining process is avoided, and the wall thickness uniformity of the TC4 titanium alloy shell with the large wall thickness and the complex structure is guaranteed.

Description

Technical Field

[0001] The present invention relates to isothermal forming tooling and a wall thickness control method for a titanium alloy shell with a large wall thickness and a complex structure, and belongs to the technical field of tank shell manufacturing. Background Art

[0002] In response to the requirements of lightweight and efficient rapid manufacturing of spacecraft, the use of lighter and higher-strength structural materials and process technologies with higher forming efficiency is currently an effective way to achieve weight reduction and rapid manufacturing of spacecraft structures. In order to meet the requirements of lightweight and rapid manufacturing of spacecraft, it puts forward the demand for TC4 titanium alloy shells with large wall thickness and complex structure.

[0003] Large wall thickness refers to the difference between the maximum outer radius and the minimum inner radius of the titanium alloy shell ≥ 30mm; complex structure refers to the titanium alloy shell with fan ears (such as Fig.11 The isothermal forming refers to the control of the forming temperature of the titanium alloy shell within the range of 750±5℃; the wall thickness control refers to the wall thickness deviation of the titanium alloy shell (the difference between the maximum and minimum measured wall thickness) ≤0.10mm.

[0004] For TC4 titanium alloy shells with large wall thickness and complex structure with wall thickness ≥30mm, both at home and abroad, the scheme of machining TC4 titanium alloy die forgings into target components is generally adopted for preparation. However, the forming of TC4 titanium alloy die forgings requires equipment with large tonnage. At the same time, the forging process undergoes many auxiliary processes, and the forging dies used have a long manufacturing cycle and high manufacturing costs, resulting in a long manufacturing cycle of TC4 titanium alloy die forgings, which takes about 2 to 3 months; the manufacturing cost is high, about 1,000 yuan / kg. In addition, the shell is prepared by machining TC4 titanium alloy die forgings, and the raw material utilization rate is low, only about 10 to 15%, which leads to a great waste of raw materials, and also further increases the manufacturing cost of TC4 titanium alloy shells. In summary, in the prior art, the forming scheme for TC4 titanium alloy shells with large wall thickness and complex structure has a series of problems such as long manufacturing cycle, high manufacturing cost, and low raw material utilization rate. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, to propose an isothermal forming tooling and a wall thickness control method for a titanium alloy shell with a large wall thickness and a complex structure, thereby ensuring the wall thickness accuracy of a TC4 titanium alloy shell with a large wall thickness and a complex structure.

[0006] The technical solution of the present invention is:

[0007] The invention discloses an isothermal forming tool for a TC4 titanium alloy shell with a large wall thickness and a complex structure, which is characterized by comprising a punch, a die, two support seats, a base and two centering rods; wherein,

[0008] The punch is fixedly connected to the upper platform of the hot pressing equipment;

[0009] The support seat is an arc-shaped structure with variable wall thickness. Two support seats are fixed on the base in mirror symmetry to support and fix the die. Figure 5 As shown;

[0010] The concave die is a hollow cylinder with variable wall thickness, and the hollow cylinder cooperates with the convex die;

[0011] The base is a round solid thick plate; the edge of the thick plate is provided with a number of symmetrically distributed U-shaped through grooves B for fixed connection with the lower platform of the hot pressing equipment;

[0012] The centering rod is a straight rod, used for centering the punch, die and support seat;

[0013] The punch is a hollow structure, including a boss, an upper section, a middle section and a lower section, wherein the boss and the upper section are cylindrical structures, the middle section is a conical structure, and the lower section is an arc structure; the boss is a columnar structure, and the edge of the column is provided with a number of symmetrically distributed U-shaped through grooves A for fixed connection with the upper platform of the hot pressing equipment; a number of first through holes are evenly distributed on the end surface of the boss for centering the punch and the die; side holes are provided on the circumference of the upper section of the punch for fixing the thermocouple.

[0014] Furthermore, in the above-mentioned tooling, the die comprises an upper die section and a lower die section, the outer diameters of the upper die section and the lower die section are the same, and the inner diameter of the upper die section is larger than the inner diameter of the lower die section; a plurality of second through holes are evenly distributed on the top surface of the lower die section, which match the first through holes of the punch and are used for centering the punch and the die; and two lifting ears are symmetrically arranged on the circumference of the upper die section for lifting.

[0015] Furthermore, in the above-mentioned tooling, the support seat is an arc structure, including an upper section of the support seat and a lower section of the support seat; wherein the wall thickness of the upper section of the support seat is smaller than the wall thickness of the lower section of the support seat; the lower section of the support seat is symmetrically provided with two support seat lifting ears in the circumferential direction for lifting; the top of the lower section of the support seat is symmetrically provided with two holes, the holes match the corresponding positions of the first through hole of the punch and the second through hole of the die, and are used for centering the punch, the die and the support seat; a second side hole is provided on the circumference of the lower section of the support seat for fixing the thermocouple.

[0016] Further, in the above tooling, the arc centers of the plurality of U-shaped through grooves A are located on a concentric circle, the diameter of the concentric circle is Φ550-580 mm and is concentric with the surface of the boss;

[0017] The outer diameter of the boss is Φ600-700 mm, the inner diameter of the boss is Φ90-100 mm, and the height of the boss is 50-60 mm;

[0018] The centers of the first through holes are all on a circle with a diameter of Φ490-500 mm, and the circle is concentric with the boss;

[0019] The outer diameter of the upper section of the punch is Φ380-400mm, and the inner diameter of the upper section of the punch is consistent with the inner diameter of the boss; the height of the upper section of the punch is 200-230mm; the guide radius at the connection between the boss and the upper section of the punch is R10-20mm;

[0020] The cone angle of the conical structure of the middle section of the punch is 4-5°; the guide angle of the connection between the middle section of the punch and the upper section of the punch is R50-60mm;

[0021] The outer diameter of the middle section of the punch is Φ320-350mm, and the inner diameter of the middle section of the punch is consistent with the inner diameter of the upper section of the punch; the height of the middle section of the punch is 45-60mm;

[0022] The lower section of the punch is a solid structure, and the outer diameter of the lower section of the punch is 10 to 12 mm smaller than the minimum inner diameter of the TC4 titanium alloy shell;

[0023] A centering structure is arranged at the lower section of the punch, and the contour of the lower section of the punch is conical with a cone angle of 35 to 50 degrees; the height of the arc part of the lower section of the punch is half of the outer diameter of the arc; the guide angle at the connection between the middle section of the punch and the lower section of the punch is R20 to 30 mm.

[0024] Furthermore, in the above tooling, the maximum outer diameter of the lower section of the punch and the inner diameter of the lower section of the die are required to be:

[0025] D 10 =D0+△D0

[0026] D 11 =D1+△D1

[0027] △D0=A×D0×T

[0028] △D1=A×D1×T

[0029] Among them, D 10 D is the maximum outer diameter of the solid arc at the forming temperature of the lower section of the punch. 11 is the inner diameter of the hollow cylinder in the lower section of the die at the forming temperature; T is the isothermal forming temperature, A is the thermal expansion coefficient of the punch and die materials; D0 and D1 are the outer diameter of the solid arc in the lower section of the punch and the inner diameter of the hollow cylinder in the lower section of the die at room temperature, respectively.

[0030] The present invention discloses a method for isothermal forming and wall thickness control of a TC4 titanium alloy shell with a large wall thickness and complex structure, comprising:

[0031] Isothermal forming tooling for manufacturing TC4 titanium alloy shells with large wall thickness and complex structure;

[0032] Design and prepare TC4 titanium alloy slabs;

[0033] Assemble the isothermal forming tooling and slab of TC4 titanium alloy shell and fix them to the hot pressing equipment;

[0034] Close the side door of the hot pressing equipment to form a closed space, and heat and insulate the isothermal forming tooling and slabs in the hot pressing equipment;

[0035] Isothermal forming is started until the TC4 titanium alloy slab is formed into a TC4 titanium alloy shell blank with a large wall thickness and a complex structure;

[0036] After the isothermal forming is completed, the TC4 titanium alloy shell blank is separated from the isothermal forming tooling to obtain the TC4 titanium alloy shell blank;

[0037] The TC4 titanium alloy shell blank is subjected to vacuum annealing heat treatment at a holding temperature of 745 to 805° C. for a holding time of 90 to 120 minutes;

[0038] The TC4 titanium alloy shell blank after vacuum annealing heat treatment is roughly processed to form a tower-shaped structure;

[0039] The tower structure is subjected to vacuum annealing heat treatment, with a holding temperature of 745-805°C and a holding time of 90-120 minutes;

[0040] The tower-shaped structure is finely processed after vacuum annealing and heat treatment to obtain a TC4 titanium alloy shell with a large wall thickness and complex structure.

[0041] Further, in the above method, the maximum thickness of the TC4 titanium alloy slab during the isothermal forming process is t1=t0+Δt, Δt=B×t0×T; t0 is the thickness of the TC4 titanium alloy slab at room temperature;

[0042] When D 11 -D 10 When -2×t1=0.2~0.3mm, the wall thickness of TC4 titanium alloy slab at room temperature is designed to be t0=[1.014475(D1-D0)-(D 11 -D 10 -2×t1)] / 2.015045;

[0043] The outer diameter of the TC4 titanium alloy slab at room temperature is Φ500-600 mm. A pit structure is arranged on the upper end surface of the TC4 titanium alloy slab to match the centering structure of the lower section of the punch.

[0044] Furthermore, in the above method, the TC4 titanium alloy shell isothermal forming tooling and the slab are assembled and fixedly connected with the hot pressing equipment, specifically:

[0045] The arc surface of the support seat corresponds to the side of the base without the U-shaped through groove B, and the two support seats and the base are fixedly connected by welding to form an assembly A;

[0046] The centering rod passes through the second through hole of the die and the hole of the lower section of the support seat in sequence to realize the centering of the assembly A and the die;

[0047] The punch is fixedly mounted on the upper platform of the hot pressing equipment;

[0048] The assembly A is fixedly mounted on the lower platform of the hot pressing equipment;

[0049] The assembly A is brought into contact with the concave die to form the assembly B;

[0050] The centering rod is passed through the first through hole of the punch, the second through hole of the die, and the hole of the lower section of the support seat in sequence to realize the centering of the punch, the die, and the assembly A;

[0051] Place the TC4 titanium alloy slab on the top of the hollow cylinder in the lower section of the die;

[0052] The lower end surface of the TC4 titanium alloy slab contacts the top end surface of the hollow cylinder in the lower section of the die to form an assembly C.

[0053] Furthermore, in the above method, the isothermal forming tooling and slab in the hot pressing equipment are subjected to heating and insulation treatment, specifically: the heating rate of the hot pressing equipment is 40-50°C / h, until the inner cavity temperature of the hot pressing equipment reaches 745-755°C, and insulation treatment is performed. The temperature of the inner cavity of the hot pressing equipment is always maintained within the range of 750±5°C, and the insulation time is 50-70min.

[0054] Furthermore, in the above method, isothermal forming is started until the TC4 titanium alloy slab is formed into a TC4 titanium alloy shell blank with a large wall thickness and a complex structure, specifically:

[0055] The centering structure of the lower section of the punch is brought into contact with the pit set on the upper end surface of the TC4 titanium alloy slab; before the punch contacts the TC4 titanium alloy slab, the pressing rate is 30 to 50 mm / min; after the punch contacts the TC4 titanium alloy slab, the pressing rate of the punch is adjusted to 20 to 25 mm / min, and the punch maintains the same pressing rate during the subsequent isothermal forming process;

[0056] As the punch moves downward, the lower section of the punch and the middle section of the punch contact with the TC4 titanium alloy slab in sequence to form a TC4 titanium alloy shell blank.

[0057] Furthermore, in the above method, the tower-like structure includes a plurality of steps, the width of each step is 8 to 10 mm, and the height of each step is 10 to 12 mm.

[0058] Furthermore, in the above method, the wall thickness deviation of the TC4 titanium alloy shell with large wall thickness and complex structure is less than or equal to 0.10 mm.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) The present invention designs an integrated isothermal forming tooling based on the structural characteristics and material properties of the titanium alloy shell with large wall thickness and complex structure. The structural design of the column-cone-arc composite structure punch + variable wall thickness die + support seat + base + centering rod is adopted, so that the TC4 titanium alloy shell blank is isothermally formed from the TC4 titanium alloy sheet, which greatly reduces the manufacturing cycle and cost of the TC4 titanium alloy shell and improves the utilization rate of raw materials.

[0061] (2) The punch of the present invention adopts a column-cone-arc composite structure design, which is beneficial to the material flow during the isothermal forming process of the TC4 titanium alloy slab, avoids the locking phenomenon caused by excessive friction between the TC4 titanium alloy slab and the punch, and helps to improve the forming accuracy of the titanium alloy shell with large wall thickness and complex structure.

[0062] (3) The design of the centering holes and the centering rods on the punch, die, and support seat, and the design of the pit structure on the TC4 titanium alloy slab and the centering structure of the lower section of the punch in the present invention avoid deflection during the isothermal forming process of the TC4 titanium alloy slab, which helps to improve the forming accuracy of the titanium alloy shell with large wall thickness and complex structure.

[0063] (4) In the process of designing the integrated isothermal forming tooling and TC4 titanium alloy slab in the present invention, the difference in thermal expansion coefficients between the mold material and the TC4 titanium alloy at the forming temperature is fully considered, so that the male and female molds have good dimensional matching with the TC4 titanium alloy slab during the isothermal forming process, which helps to improve the forming accuracy of titanium alloy shells with large wall thickness and complex structure.

[0064] (5) The two vacuum annealing heat treatments before and after rough machining of the TC4 titanium alloy shell blank in the present invention combined with the tower-shaped profile formed by rough machining can effectively eliminate the residual stress inside the TC4 titanium alloy shell blank, avoid local deformation caused by stress release during mechanical machining, and ensure the wall thickness uniformity of the TC4 titanium alloy shell with large wall thickness and complex structure.

[0065] (6) The present invention relates to a method for isothermal forming and wall thickness control of a titanium alloy shell with a large wall thickness and a complex structure. In view of the structural characteristics and material properties of a TC4 titanium alloy shell with a large wall thickness and a complex structure, an integrated isothermal forming tooling is designed. The structural design of a column-cone-arc composite structure punch + a variable wall thickness die + a support seat + a base + a centering rod is adopted to realize the isothermal forming of a TC4 titanium alloy shell blank from a TC4 titanium alloy sheet blank, greatly improving the forming efficiency and raw material utilization rate of the TC4 titanium alloy shell blank, and reducing the manufacturing cycle and cost of the TC4 titanium alloy shell. By accurately designing the blank and the mold and matching reasonable isothermal forming temperature, hot pressing rate and other process parameters, the wall thickness thinning and cracking phenomena in the isothermal forming process of the TC4 titanium alloy shell are eliminated, and the forming quality of the titanium alloy shell with a large wall thickness and a complex structure is guaranteed. The vacuum annealing heat treatment before and after rough machining and the reasonable rough machining profile design effectively eliminate the residual stress inside the TC4 titanium alloy shell blank, avoid the local deformation caused by stress release during the machining process, and ensure the uniformity of the wall thickness of the TC4 titanium alloy shell with large wall thickness and complex structure. The operation process of the present invention is simple and efficient, suitable for batch processing, and has strong operability and practicality.

[0066] (7) The present invention can realize the short-cycle manufacturing of TC4 titanium alloy shells with large wall thickness and complex structure, and at the same time greatly reduce the manufacturing cost of TC4 titanium alloy shells, and significantly improve the utilization rate of raw materials. In addition, by accurately designing the blank and the mold, and matching reasonable isothermal forming temperature, hot pressing rate and other process parameters, the wall thickness thinning phenomenon in the isothermal hot pressing process of the TC4 titanium alloy shell is reduced or eliminated, and combined with reasonable mechanical processing technology, the wall thickness accuracy of the TC4 titanium alloy shell with large wall thickness and complex structure is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the structure of the rapid isothermal forming tooling of the present invention;

[0068] Figure 2 It is a structural schematic diagram of the centering rod of the present invention;

[0069] Figure 3 a is a schematic structural diagram of the male mold of the present invention (seen from the top);

[0070] Figure 3 b is a schematic structural diagram of the male mold of the present invention (seen from the bottom end);

[0071] Figure 3 c is a partial enlarged view of the male mold of the present invention;

[0072] Figure 4 Schematic diagram of the structure of the concave mold of the present invention (seen from the top);

[0073] Figure 5 It is a structural schematic diagram of the support base of the present invention (seen from the top);

[0074] Figure 6 It is a structural schematic diagram of the base of the present invention;

[0075] Figure 7 It is a schematic structural diagram of the TC4 titanium alloy slab of the present invention;

[0076] Figure 8 a is a schematic diagram of the structure of the assembly A of the present invention;

[0077] Figure 8 b is a schematic diagram of the structure of the assembly B of the present invention;

[0078] Figure 8 c is a schematic diagram of the centering structure of the isothermal forming tooling of the present invention;

[0079] Fig. 9 It is a schematic diagram of the structure of the TC4 titanium alloy housing blank of the present invention;

[0080] Fig.10 This is a schematic diagram of the tower-shaped structure of the TC4 titanium alloy housing blank after rough machining of the present invention;

[0081] Fig.11 a is a schematic diagram of the structure of a titanium alloy shell with a large wall thickness and a complex structure according to the present invention;

[0082] Fig.11 b is a cross-sectional view of the titanium alloy shell with large wall thickness and complex structure of the present invention. DETAILED DESCRIPTION

[0083] like Figure 1 As shown, the present invention discloses a isothermal forming tool for a TC4 titanium alloy shell with a large wall thickness and a complex structure, which is characterized by comprising a punch 1, a die 2, two support seats 3, a base 4 and two centering rods 5; wherein,

[0084] The punch 1 is fixedly connected to the upper platform of the hot pressing equipment;

[0085] The support seat 3 is an arc-shaped structure with variable wall thickness. Two support seats 3 are fixed on the base 4 in a mirror-symmetrical manner to support and fix the die 2.

[0086] The die 2 is a hollow cylinder with variable wall thickness, and the hollow cylinder cooperates with the punch 1;

[0087] The base 4 is a circular solid thick plate; the edge of the thick plate is provided with a plurality of symmetrically distributed U-shaped through grooves B106 for fixedly connecting with the lower platform of the hot pressing equipment; Figure 6 As shown;

[0088] The centering rod 5 is a straight rod, which is used for centering the punch 1, the die 2 and the support seat 3; Figure 2 As shown;

[0089] The punch 1 is a hollow structure, including a boss 101, a punch upper section 102, a punch middle section 103 and a punch lower section 104, wherein the boss 101 and the punch upper section 102 are cylindrical structures, the punch middle section 103 is a conical structure, and the punch lower section is an arc structure; the boss 101 is a columnar structure, and the edge of the column is provided with a number of symmetrically distributed U-shaped through grooves A105 for fixed connection with the upper platform of the hot pressing equipment; a number of first through holes 6 are evenly distributed on the end surface of the boss for centering the punch 1 and the die 2; the circumference of the punch upper section 102 is provided with side holes 8 for fixing the thermocouple. Figure 3 a and Figure 3 As shown in b.

[0090] Preferably, the die 2 comprises an upper die section 201 and a lower die section 202. The outer diameters of the upper die section 201 and the lower die section 202 are the same, and the inner diameter of the upper die section 201 is larger than that of the lower die section 202. The top surface of the lower die section 202 is evenly distributed with a plurality of second through holes 9, which match the first through holes 6 of the punch 1 and are used for centering the punch 1 and the die 2. The upper die section 201 is symmetrically provided with two lifting ears 10 on the circumference for lifting. Figure 4 shown.

[0091] Preferably, the support seat 3 is an arc structure, including a support seat upper section 301 and a support seat lower section 302; wherein, the wall thickness of the support seat upper section 301 is smaller than the wall thickness of the support seat lower section 302; the support seat lower section 302 has two support seat lifting ears 11 symmetrically distributed in the circumferential direction for lifting; the support seat lower section 302 has two holes 12 symmetrically distributed at the top, the holes 12 match the corresponding positions of the first through hole 6 of the punch 1 and the second through hole 9 of the die 2, and are used for centering the punch 1, the die 2 and the support seat 3; a second side hole 13 is provided on the circumference of the support seat lower section 302 for fixing the thermocouple.

[0092] Preferably, the arc centers of the plurality of U-shaped through grooves A105 are located on a concentric circle, the diameter of the concentric circle is Φ550-580 mm and is concentric with the surface of the boss 101;

[0093] The outer diameter of the boss 101 is Φ600-700 mm, the inner diameter of the boss 101 is Φ90-100 mm, and the height of the boss 101 is 50-60 mm;

[0094] The centers of the first through holes 6 are all on a circle with a diameter of Φ490-500 mm, and the circle is concentric with the boss 101;

[0095] The outer diameter of the punch upper section 102 is Φ380-400 mm, and the inner diameter of the punch upper section 102 is consistent with the inner diameter of the boss 101; the height of the punch upper section 102 is 200-230 mm; the guide radius at the connection between the boss 101 and the punch upper section 102 is R10-20 mm;

[0096] The cone angle of the conical structure of the middle section 103 of the punch is 4 to 5 degrees; the guide fillet angle at the connection between the middle section 103 of the punch and the upper section 102 of the punch is R50 to 60 mm;

[0097] The outer diameter of the middle section 103 of the punch is Φ320-350 mm, and the inner diameter of the middle section 103 of the punch is consistent with the inner diameter of the upper section 102 of the punch; the height of the middle section 103 of the punch is 45-60 mm;

[0098] The lower section 104 of the punch is a solid structure, and the outer diameter of the lower section 104 of the punch is 10 to 12 mm smaller than the minimum inner diameter of the TC4 titanium alloy shell 17; Fig.11 As shown;

[0099] The punch lower section 104 is provided with a centering structure 22, and the contour of the punch lower section 104 is conical with a cone angle of 35 to 50 degrees; the height of the arc portion of the punch lower section 104 is half of the arc outer diameter; the guide fillet angle at the connection between the punch middle section 103 and the punch lower section 104 is R20 to 30 mm.

[0100] Preferably, the maximum outer diameter of the lower section 104 of the male die and the inner diameter of the lower section 202 of the female die are as follows:

[0101] D 10 =D0+△D0

[0102] D 11 =D1+△D1

[0103] △D0=A×D0×T

[0104] △D1=A×D1×T

[0105] Among them, D 10 D is the maximum outer diameter of the solid arc of the lower section 104 of the punch at the forming temperature. 11 is the inner diameter of the hollow cylinder of the lower section 202 of the die at the forming temperature; T is the isothermal forming temperature, A is the thermal expansion coefficient of the materials of the punch 1 and the die 2; D0 and D1 are the outer diameter of the solid arc of the lower section of the punch 1 and the inner diameter of the hollow cylinder of the lower section of the die 2 at room temperature, respectively.

[0106] The present invention discloses a method for isothermal forming and wall thickness control of a TC4 titanium alloy shell with a large wall thickness and complex structure, comprising:

[0107] Isothermal forming tooling for manufacturing TC4 titanium alloy shells with large wall thickness and complex structure;

[0108] Design and prepare TC4 titanium alloy slab 14;

[0109] Assemble the TC4 titanium alloy shell isothermal forming tooling and the plate blank 14, and fix them to the hot pressing equipment;

[0110] Close the side door of the hot pressing equipment to form a closed space, and heat and insulate the isothermal forming tooling and the slab 14 in the hot pressing equipment;

[0111] Isothermal forming is started until the TC4 titanium alloy slab blank 14 is formed into a TC4 titanium alloy shell blank 15 with a large wall thickness and a complex structure;

[0112] After the isothermal forming is completed, the TC4 titanium alloy shell blank 15 is separated from the isothermal forming tool to obtain the TC4 titanium alloy shell blank 15; Fig. 9 As shown;

[0113] The TC4 titanium alloy shell blank 15 is subjected to vacuum annealing heat treatment at a holding temperature of 745 to 805° C. for a holding time of 90 to 120 minutes;

[0114] The TC4 titanium alloy shell blank 15 after vacuum annealing heat treatment is roughly processed to form a tower structure 16; Fig.10 As shown;

[0115] The tower structure 16 is subjected to vacuum annealing heat treatment, with a holding temperature of 745 to 805° C. and a holding time of 90 to 120 minutes;

[0116] The tower-shaped structure 16 is subjected to vacuum annealing heat treatment and fine processing to obtain a TC4 titanium alloy shell 17 with a large wall thickness and a complex structure.

[0117] Preferably, the maximum thickness of the TC4 titanium alloy slab 14 during isothermal forming is t1=t0+Δt, Δt=B×t0×T; t0 is the thickness of the TC4 titanium alloy slab 14 at room temperature;

[0118] When D 11 -D 10 When -2×t1=0.2~0.3mm, the wall thickness of TC4 titanium alloy slab 14 at room temperature is designed to be t0=[1.014475(D1-D0)-(D 11 -D 10 -2×t1)] / 2.015045;

[0119] The outer diameter of the TC4 titanium alloy slab 14 at room temperature is Φ500-600 mm. A concave structure is provided on the upper end surface of the TC4 titanium alloy slab 14 to match the centering structure 22 of the lower section of the punch 1 .

[0120] Preferably, the TC4 titanium alloy shell isothermal forming tooling and the plate blank 14 are assembled and fixedly connected to the hot pressing equipment, specifically:

[0121] The arc surface of the support seat 3 corresponds to the side of the base 4 without the U-shaped through groove B106, and the two support seats 3 and the base 4 are fixedly connected by welding to form an assembly A;

[0122] The centering rod 5 passes through the second through hole 9 of the die 2 and the hole 12 of the lower section 302 of the support seat in sequence, so as to realize the centering of the assembly A and the die 2;

[0123] The punch 1 is fixedly mounted on the upper platform of the hot pressing equipment;

[0124] The assembly A is fixedly mounted on the lower platform of the hot pressing equipment;

[0125] The assembly A is brought into contact with the concave die 2 to form the assembly B;

[0126] The centering rod 5 is passed through the first through hole 6 of the punch 1, the second through hole 9 of the die 2 and the hole 12 of the lower section 302 of the support seat in sequence to realize the centering between the punch 1, the die 2 and the assembly A;

[0127] The TC4 titanium alloy slab 14 is placed on the top of the hollow cylinder in the lower section 202 of the die;

[0128] The lower end surface of the TC4 titanium alloy slab 14 contacts the top end surface of the hollow cylinder of the lower section 202 of the die to form an assembly C.

[0129] Preferably, the isothermal forming tooling and the slab 14 in the hot pressing equipment are subjected to heating and insulation treatment, specifically: the heating rate of the hot pressing equipment is 40-50°C / h, until the inner cavity temperature of the hot pressing equipment reaches 745-755°C, and insulation treatment is performed. The temperature of the inner cavity of the hot pressing equipment is always maintained in the range of 750±5°C, and the insulation time is 50-70min.

[0130] Preferably, isothermal forming is started until the TC4 titanium alloy slab blank 14 is formed into a TC4 titanium alloy housing blank 15 with a large wall thickness and a complex structure, specifically:

[0131] The centering structure 22 of the lower section 104 of the punch is brought into contact with the pit set on the upper end surface of the TC4 titanium alloy slab 14; before the punch 1 is brought into contact with the TC4 titanium alloy slab 14, the pressing rate is 30 to 50 mm / min; after the punch 1 is brought into contact with the TC4 titanium alloy slab 14, the pressing rate of the punch 1 is adjusted to 20 to 25 mm / min, and the punch 1 maintains the same pressing rate during the subsequent isothermal forming process;

[0132] As the punch 1 moves downward, the lower punch section 104 and the middle punch section 103 sequentially contact the TC4 titanium alloy slab blank 14 to form a TC4 titanium alloy shell blank 15 .

[0133] Preferably, the tower-like structure 16 includes a plurality of steps, each step has a width of 8 to 10 mm, and each step has a height of 10 to 12 mm.

[0134] Preferably, the wall thickness deviation of the TC4 titanium alloy shell 17 with large wall thickness and complex structure is less than or equal to 0.10 mm.

[0135] The materials of the punch 1, the die 2, the support seat 3 and the base 4 are all 304 stainless steel; the material of the centering rod 5 is A3 steel.

[0136] The U-shaped through groove A105 on the boss of punch 1 is used for fixed connection with the upper platform of the hot pressing equipment, and the groove width of the U-shaped through groove A105 is 28mm; the arc center of the four U-shaped through grooves A105 is located on a concentric circle, the diameter of the concentric circle is Φ550~580mm and is concentric with the surface of the boss. The outer diameter of the hollow cylinder of the boss of punch 1 is Φ600~700mm, the inner diameter of the hollow cylinder of the boss of punch 1 is Φ90~100mm, and the height of the cylinder of the boss of punch 1 is 50~60mm; the diameter of the four first through holes 6 evenly distributed in the cylindrical structure of the boss is Φ10mm, and the center of the four first through holes 6 is on a circle with a diameter of Φ490~500mm, which is concentric with the boss cylinder;

[0137] The outer diameter of the upper hollow cylinder of the punch 1 is Φ380-400mm, the inner diameter of the upper hollow cylinder of the punch 1 is consistent with the inner diameter of the hollow cylinder of the boss of the punch 1, the height of the upper hollow cylinder of the punch 1 is 200-230mm, and the fillet angle of the contact position between the hollow cylinder of the boss of the punch 1 and the upper hollow cylinder of the punch 1 is R10-20mm. The diameter of the side hole 8 on the circumference of the cylindrical structure of the upper section of the punch 1 is Φ8mm, the depth is 30-50mm, and the distance between the axis where the center of the side hole 8 is located and the upper end of the boss is 160-200mm;

[0138] The cone angle of the hollow cone structure in the middle section of punch 1 (the angle between the cone surface of the hollow cone structure and the axis of the punch) is 4 to 5°, and the fillet angle of the contact position between the hollow cone structure in the middle section of punch 1 and the hollow cylinder in the upper section of punch 1 is R50 to 60 mm; the outer diameter of the top of the hollow cone structure in the middle section of punch 1 is Φ320 to 350 mm, the inner diameter of the top of the hollow cone structure in the middle section of punch 1 is consistent with the inner diameter of the hollow cylinder in the upper section of punch 1, the wall thickness of the hollow cone structure in the middle section of punch 1 is consistent with the wall thickness of the hollow cylinder in the upper section of punch 1, and the height of the hollow cone structure in the middle section of punch 1 is 45 to 60 mm.

[0139] It is stipulated that one end of the hollow conical structure in the middle section of the punch 1 that contacts the hollow cylinder in the upper section of the punch 1 is the top end of the hollow conical structure in the middle section of the punch 1, and the other end is the bottom end of the hollow conical structure in the middle section of the punch 1.

[0140] The arc portion of the lower section of the punch 1 is a solid structure, and its outer diameter is 10 to 12 mm smaller than the minimum inner diameter of the TC4 titanium alloy shell 17; the bottom end of the arc portion of the lower section of the punch 1 is a centering structure, such as Figure 3 As shown in Figure c, its profile is conical, the cone angle (the angle between the cone and the punch axis) is 45°, the maximum diameter is 5mm (the end in contact with the arc of the lower section of the punch 1), the minimum diameter is 3mm (the free end), and the height of the arc part of the lower section of the punch 1 is half of its outer diameter. The guide angle of the contact position between the bottom end of the hollow cone structure of the middle section of the punch 1 and the solid arc structure of the lower section of the punch 1 is R20-30mm.

[0141] It is stipulated that one end where the solid arc structure of the lower section of the punch 1 contacts the hollow conical structure of the middle section of the punch 1 is the top end of the solid arc structure of the lower section of the punch 1, and the other end is the bottom end of the solid arc structure of the lower section of the punch.

[0142] The die 2 comprises an upper hollow cylinder and a lower hollow cylinder. The outer diameter of the upper hollow cylinder of the die 2 is Φ600-700mm, the inner diameter of the upper hollow cylinder of the die 2 is Φ580-600mm, and the height of the upper hollow cylinder of the die 2 is 30-50mm. The outer diameter of the lower hollow cylinder of the die 2 is consistent with the outer diameter of the upper hollow cylinder of the die, the inner diameter of the lower hollow cylinder of the die 2 is Φ400-450mm, and the height of the lower hollow cylinder of the die 2 is 70-100mm. Four second positioning through holes 9 are evenly distributed on the top of the lower hollow cylinder of the die 2. The diameters of the four second positioning through holes 9 match the diameters of the four first through holes 6 on the boss structure of the punch 1, and the centers of the four second positioning through holes 9 match the centers of the four first through holes 6 on the boss structure of the punch 1. The lead angle of the contact position between the top of the hollow cylinder in the lower section of the die 2 and the inner diameter of the hollow cylinder in the lower section of the die 2 is R30-50mm. The first ear 10 on the circumference of the die 2 is a solid structure, with an inner cylinder diameter of Φ40-50mm and a height of 50mm, an outer cylinder diameter of Φ60-70mm and a height of 10mm. The inner cylinder and the outer cylinder are coaxial, and the distance between the axis and the top of the hollow cylinder in the lower section of the die 2 is 12-15mm.

[0143] The end where the upper hollow cylinder of the die 2 contacts the lower hollow cylinder of the die 2 is defined as the top end of the lower hollow cylinder of the die 2, and the other end is defined as the bottom end of the lower hollow cylinder of the die 2. The portion where the first lifting ear 10 contacts the circumference of the die 2 is defined as the inner cylinder, and the other side is defined as the outer cylinder of the first lifting ear 10.

[0144] The outer diameter of the upper arc structure of the support seat 3 is Φ710-750mm, the inner diameter of the upper arc structure of the support seat 3 matches the outer diameter of the lower hollow cylinder of the die 2, the height of the upper arc structure of the support seat 3 is 50-70mm, and the wall thickness of the upper arc structure of the support seat 3 is 50-60mm; the outer diameter of the lower arc structure of the support seat 3 is consistent with the outer diameter of the upper arc structure of the support seat 3, the inner diameter of the lower arc structure of the support seat 3 is Φ420-450mm, the height of the lower arc structure of the support seat 3 is 300-350mm, and the wall thickness of the lower arc structure of the support seat 3 is 130-150mm. The diameter of the second side hole 13 on the circumference of the support seat 3 is Φ8mm, the depth is 30-50mm, and the distance between the axis where the center of the second side hole 13 is located and the top of the lower arc structure of the support seat 3 is 50-70mm. The second support seat lifting ear 11 on the circumference of the support seat 3 is a solid structure, with an inner cylindrical diameter of Φ40-50mm and a height of 50mm, an outer cylindrical diameter of Φ60-70mm and a height of 10mm, the inner cylinder and the outer cylinder are coaxial, and the distance between the axis and the top of the arc-shaped structure of the lower section of the support seat 3 is 140-160mm. Two centering holes 12 are symmetrically distributed at the top of the arc-shaped structure of the lower section of the support seat 3, and the diameters of the two centering holes 12 match the corresponding first through holes 6 and 9 on the upper surface of the boss structure of the punch 1 and the upper surface of the lower section of the die 2, and the centers of the two centering holes 12 match the corresponding first through holes 6 and 9 on the upper surface of the boss structure of the punch 1 and the upper surface of the lower section of the die 2, and the depths of the two centering holes 12 are both 60-70mm.

[0145] It is stipulated that one end where the upper arc structure of the support seat 3 contacts the lower arc structure of the support seat 3 is the top end of the lower arc structure of the support seat 3, and the other end is the bottom end of the lower arc structure of the support seat 3.

[0146] The diameter of the base 4 is Φ1000~1200mm, and the thickness of the base 4 is 50~60mm; the four U-shaped through grooves A105 on the edge of the base 4 are used for fixed connection with the lower platform of the hot pressing equipment, and the groove width of the U-shaped through grooves A105 is 28mm; the arc center of the four U-shaped through grooves A105 is located on a concentric circle, the diameter of the concentric circle is Φ850~880mm and is concentric with the center of the surface of the base 4.

[0147] The diameter of the centering rod 5 matches the diameters of the corresponding holes 6, 9, 12 on the boss structure of the punch 1, on the top surface of the lower section of the die 2, and on the top of the arc structure of the lower section of the support seat 3. The length of the centering rod 5 is 800-1200 mm.

[0148] Two support seats 3 are symmetrically placed on the base, and the circumferential arc surface of the support seat 3 corresponds to the side of the base 4 without the U-shaped through groove A105. The two support seats 3 and the base 4 are fixedly connected by welding to form an assembly A, such as Figure 8As shown in a; the die 2 is placed on the assembly A, that is, the bottom end of the hollow cylinder of the lower section of the die 2 contacts the top of the arc-shaped structure of the lower section of the support seat 3 to form an assembly B, such as Figure 8 b. The centering rod 5 passes through the corresponding centering holes 9 and 12 on the top surface of the lower section of the die 2 and the top of the arc-shaped structure of the lower section of the support seat 3 in sequence to realize the centering of the assembly A and the assembly B, as shown in FIG. Figure 8 As shown in c.

[0149] This embodiment provides a method for isothermal forming and wall thickness control of a titanium alloy shell with a large wall thickness and complex structure, the method comprising the following steps:

[0150] When designing the hot-pressed sheet blank 14, the difference in thermal expansion coefficients between the TC4 titanium alloy and the materials of the punch 1 and the die 2 during the isothermal forming process should be fully considered to ensure that the TC4 titanium alloy sheet blank 14 has good dimensional matching with the punch 1 and the die 2 during the isothermal forming process, thereby ensuring the forming accuracy of the large TC4 titanium alloy shell blank 15. The isothermal forming temperature is 750±5℃, and the thermal expansion coefficient of the TC4 titanium alloy selected in this temperature range is 10.03×10 -6 / ℃, while the thermal expansion coefficient of the materials of the male die 1 and the female die 2 is 19.3×10 -6 / ℃.

[0151] In this embodiment, if the outer diameter of the solid arc at the lower section of the punch 1 and the inner diameter of the hollow cylinder at the lower section of the die 2 are D0 and D1 respectively at room temperature, the maximum thermal expansion during the isothermal forming process is △D0=19.3×10 -6 ×D0×750,△D1=19.3×10 -6 ×D1×750, so the maximum values ​​of the solid arc outer diameter of the lower section of the punch 1 and the hollow cylinder inner diameter of the lower section of the die 2 during the isothermal forming process are D 10 =D0+△D0,D 11 =D1+△D1.

[0152] In this embodiment, if the thickness of the TC4 titanium alloy slab 14 at room temperature is t0, the maximum thermal expansion amount during the isothermal forming process is Δt=10.03×10 -6 ×t0×750; therefore, the maximum thickness t1 of the TC4 titanium alloy slab 14 during the isothermal forming process is t0+△t.

[0153] In this embodiment, when D 11 -D 10 When -2×t1=0.2~0.3mm, the TC4 titanium alloy slab 14 has good dimensional matching with the punch 1 and the die 2 during the isothermal forming process. Therefore, the wall thickness of the TC4 titanium alloy slab 14 at room temperature should be designed to be t0=[1.014475(D1-D0)-(D11 -D 10 -2×t1)] / 2.015045.

[0154] In this embodiment, the outer diameter of the TC4 titanium alloy slab 14 at room temperature is Φ500-600 mm, and a concave structure exists on the upper end surface of the TC4 titanium alloy slab 14, such as Figure 7 As shown, its alignment structure with the lower section of the punch 1 is as follows Figure 3 c) to achieve the alignment of the punch 1 and the assembly C.

[0155] It is stipulated that the end of the TC4 titanium alloy slab 14 in contact with the die 2 is the lower end surface, and the other end surface is the upper end surface of the TC4 titanium alloy slab 14.

[0156] In this embodiment, the heating rate of the hot pressing equipment is 40-50°C / h. After the hot pressing equipment is heated to 750°C, it is subjected to heat preservation treatment. During this process, the temperature of the inner cavity of the hot pressing equipment is always maintained within the range of 750±5°C.

[0157] The conical structure in the middle section of the punch 1 is conducive to demoulding the punch 1 and the TC4 titanium alloy shell blank 15, and avoids the complete locking phenomenon caused by excessive friction between the punch 1 and the TC4 titanium alloy slab 14 during the pressing process.

[0158] In this embodiment, the two vacuum annealing heat treatments before and after rough machining of the TC4 titanium alloy shell blank 15 are combined with the tower-shaped profile 16 formed by rough machining, which can effectively eliminate the residual stress inside the TC4 titanium alloy shell blank 15, avoid local deformation caused by stress release during mechanical machining, and ensure the wall thickness uniformity of the TC4 titanium alloy shell 17 with large wall thickness and complex structure.

[0159] Example

[0160] In this embodiment, the difference between the maximum outer radius and the minimum inner radius of the TC4 titanium alloy shell with a large wall thickness and complex structure is 30 mm. The following is the specific process of the isothermal forming and wall thickness control method tooling and the isothermal forming and wall thickness control method:

[0161] This embodiment provides a method for isothermal forming and wall thickness control of a TC4 titanium alloy shell with a large wall thickness and a complex structure. First, an isothermal forming tool for a TC4 titanium alloy shell with a large wall thickness and a complex structure is manufactured. The isothermal forming tool includes a punch 1, a die 2, a support seat 3, a base 4, and a centering rod 5;

[0162] The U-shaped through groove A105 on the boss of the punch 1 is used for fixed connection with the upper platform of the hot pressing equipment, and the groove width of the U-shaped through groove A105 is 28mm; the arc center of the four U-shaped through grooves A105 is located on a concentric circle, the diameter of the concentric circle is Φ575mm and is concentric with the surface of the boss. The outer diameter of the hollow cylinder of the boss of the punch 1 is Φ650mm, the inner diameter of the hollow cylinder of the boss of the punch 1 is Φ90mm, and the height of the cylinder of the boss of the punch 1 is 60mm; the diameter of the four first through holes 6 evenly distributed in the cylindrical structure of the boss is Φ10mm, and the center of the four first through holes 6 is on a circle with a diameter of Φ490mm, which is concentric with the boss cylinder;

[0163] The outer diameter of the upper hollow cylinder of the punch 1 is Φ380mm, the inner diameter of the upper hollow cylinder of the punch 1 is consistent with the inner diameter of the hollow cylinder of the boss of the punch 1, the height of the upper hollow cylinder of the punch 1 is 230mm, and the lead angle of the contact position between the hollow cylinder of the boss of the punch 1 and the upper hollow cylinder of the punch 1 is R20mm. The diameter of the side hole 8 on the circumference of the cylindrical structure of the upper section of the punch 1 is Φ8mm, the depth is 50mm, and the distance between the axis where the center of the side hole 8 is located and the upper end of the boss is 160mm;

[0164] The cone angle of the hollow cone structure in the middle section of punch 1: the angle between the cone surface of the hollow cone structure and the axis of the punch is 5°, and the fillet angle of the contact position between the hollow cone structure in the middle section of punch 1 and the hollow cylinder in the upper section of punch 1 is R50 mm; the outer diameter of the top of the hollow cone structure in the middle section of punch 1 is Φ335 mm, the inner diameter of the top of the hollow cone structure in the middle section of punch 1 is consistent with the inner diameter of the hollow cylinder in the upper section of punch 1, the wall thickness of the hollow cone structure in the middle section of punch 1 is consistent with the wall thickness of the hollow cylinder in the upper section of punch 1, and the height of the hollow cone structure in the middle section of punch 1 is 50 mm.

[0165] The arc part of the lower section of the punch 1 is a solid structure, and its outer diameter is 10 mm smaller than the minimum inner diameter of the TC4 titanium alloy shell 17; the bottom end of the arc part of the lower section of the punch 1 is a centering structure, and its profile is conical, and the angle between the cone surface and the punch axis is 45°, the maximum diameter is 5 mm, the minimum diameter is 3 mm, and the height of the arc part of the lower section of the punch 1 is half of its outer diameter. The guide angle of the contact position between the bottom end of the hollow conical structure of the middle section of the punch 1 and the solid arc structure of the lower section of the punch 1 is R20 mm.

[0166] The die 2 comprises an upper hollow cylinder and a lower hollow cylinder. The outer diameter of the upper hollow cylinder of the die 2 is Φ650 mm, the inner diameter of the upper hollow cylinder of the die 2 is Φ590 mm, and the height of the upper hollow cylinder of the die 2 is 30 mm. The outer diameter of the lower hollow cylinder of the die 2 is consistent with the outer diameter of the upper hollow cylinder of the die, the inner diameter of the lower hollow cylinder of the die 2 is Φ400 mm, and the height of the lower hollow cylinder of the die 2 is 80 mm. Four second positioning through holes 9 are evenly distributed on the top of the lower hollow cylinder of the die 2. The diameters of the four second positioning through holes 9 match the diameters of the four first through holes 6 on the boss structure of the punch 1, and the centers of the four second positioning through holes 9 match the centers of the four first through holes 6 on the boss structure of the punch 1. The fillet angle at the contact position between the top of the lower hollow cylinder of the die 2 and the inner diameter of the lower hollow cylinder of the die 2 is R50 mm. The first ear 10 on the circumference of the die 2 is a solid structure, with an inner cylinder diameter of Φ40mm and a height of 50mm, an outer cylinder diameter of Φ60mm and a height of 10mm. The inner cylinder and the outer cylinder are coaxial, and the distance between the axis and the top of the hollow cylinder in the lower section of the die 2 is 12.5mm.

[0167] The support seat 3 comprises an upper arc structure and a lower arc structure, and the central angles of the upper arc structure and the lower arc structure are both 75°. The outer diameter of the upper arc structure of the support seat 3 is Φ750mm, the inner diameter of the upper arc structure of the support seat 3 matches the outer diameter of the lower hollow cylinder of the die 2, the height of the upper arc structure of the support seat 3 is 50mm, and the wall thickness of the upper arc structure of the support seat 3 is 50mm; the outer diameter of the lower arc structure of the support seat 3 is consistent with the outer diameter of the upper arc structure of the support seat 3, the inner diameter of the lower arc structure of the support seat 3 is Φ420mm, the height of the lower arc structure of the support seat 3 is 350mm, and the wall thickness of the lower arc structure of the support seat 3 is 130mm. The diameter of the second second side hole 13 on the circumference of the support seat 3 is Φ8mm, the depth is 50mm, and the distance between the axis where the center of the second side hole 13 is located and the top of the lower arc structure of the support seat 3 is 55mm. The second support seat lifting ear 11 on the circumference of the support seat 3 is a solid structure, with an inner cylinder diameter of Φ40mm and a height of 50mm, an outer cylinder diameter of Φ60mm and a height of 10mm, the inner cylinder and the outer cylinder are coaxial, and the distance between the axis and the top of the arc-shaped structure of the lower section of the support seat 3 is 145mm. Two centering holes 12 are symmetrically distributed at the top of the arc-shaped structure of the lower section of the support seat 3, and the diameters of the two centering holes 12 match the corresponding first through holes 6 and 9 on the upper surface of the boss structure of the punch 1 and the upper surface of the lower section of the die 2, and the centers of the two centering holes 12 match the corresponding first through holes 6 and 9 on the upper surface of the boss structure of the punch 1 and the upper surface of the lower section of the die 2, and the depths of the two centering holes 12 are both 60mm.

[0168] The diameter of the base 4 is Φ1000mm, and the thickness of the base 4 is 50mm; the four U-shaped through grooves A105 on the edge of the base 4 are used for fixed connection with the lower platform of the hot pressing equipment, and the groove width of the U-shaped through grooves A105 is 28mm; the arc center of the four U-shaped through grooves A105 is located on a concentric circle, the diameter of the concentric circle is Φ865mm and is concentric with the center of the surface of the base 4.

[0169] The diameter of the centering rod 5 matches the diameters of the corresponding holes 6, 9, 12 on the boss structure of the punch 1, on the top surface of the lower section of the die 2, and on the top of the arc structure of the lower section of the support seat 3. The length of the centering rod 5 is 1000 mm.

[0170] Two support seats 3 are symmetrically placed on the base, and the circumferential arc surface of the support seat 3 corresponds to the side of the base 4 without the U-shaped through groove A105. The two support seats 3 are fixedly connected with the base 4 by welding to form an assembly A; the die 2 is placed on the assembly A, that is, the bottom end of the hollow cylinder of the lower section of the die 2 is in contact with the top of the arc structure of the lower section of the support seat 3, forming an assembly B. The centering rod 5 passes through the corresponding centering holes 9 and 12 on the top surface of the lower section of the die 2 and the top of the arc structure of the lower section of the support seat 3 in turn, so as to realize the centering of the assembly A and the assembly B.

[0171] A method for isothermal forming and wall thickness control of a titanium alloy shell with a large wall thickness and complex structure, the method comprising the following steps:

[0172] Step 1: Design and prepare a TC4 titanium alloy blank 14 with an outer diameter of Φ500 mm and a thickness of 35 mm. The upper end surface of the TC4 titanium alloy blank 14 has a concave structure, which matches the centering structure of the lower section of the punch 1 to achieve centering of the punch 1 and the assembly C;

[0173] Step 2, the punch 1 is fixedly mounted on the upper platform of the hot pressing equipment, the assembly A formed by the base 4 and the support seat 3 is fixedly mounted on the lower platform of the hot pressing equipment, the assembly A is brought into contact with the die 2 to form an assembly B, and the centering rod 5 is sequentially passed through the corresponding centering holes 6, 9, and 12 on the boss structure of the punch 1, the top surface of the lower section of the die 2, and the top of the arc structure of the lower section of the support seat 3 to realize the centering between the punch 1, the die 2, and the assembly A; the TC4 titanium alloy slab 14 is placed on the top of the hollow cylinder of the lower section of the die 2, and the lower end surface of the TC4 titanium alloy slab 14 is in contact with the top surface of the hollow cylinder of the lower section of the die 2 to form an assembly C;

[0174] Step 3, close the side door of the hot pressing equipment to form a closed space, heat the punch 1 and the assembly C in the hot pressing equipment until the inner cavity temperature of the hot pressing equipment reaches 750°C, with an error of no more than ±5°C, and then perform heat preservation for 60 minutes;

[0175] The heating rate of the hot pressing equipment is 40-50°C / h. After the hot pressing equipment is heated to 750°C, it is subjected to heat preservation treatment. During this process, the temperature of the inner cavity of the hot pressing equipment is always maintained within the range of 750±5°C.

[0176] Step 4, starting isothermal forming until the TC4 titanium alloy slab blank 14 is formed into the required TC4 titanium alloy shell blank 15 with large wall thickness and complex structure;

[0177] The specific process of isothermal forming of the TC4 titanium alloy shell blank 14 is as follows: when the punch 1 moves unloaded, that is, before the punch 1 contacts the TC4 titanium alloy slab 14, its pressing rate is 30 mm / min; once the punch 1 contacts the TC4 titanium alloy slab 14, the pressing rate of the punch 1 is adjusted to 20 mm / min, and the punch 1 maintains the same pressing rate during the subsequent isothermal forming process.

[0178] The centering structure of the lower section of the punch 1 first contacts the concave pit on the upper end surface of the TC4 titanium alloy slab 14. As the punch 1 moves downward, the arc structure of the lower section of the punch 1 and the conical structure of the middle section of the punch 1 contact the TC4 titanium alloy slab 14 in turn, thereby forming a TC4 titanium alloy shell blank 15.

[0179] The conical structure in the middle section of the punch 1 is conducive to demoulding the punch 1 and the TC4 titanium alloy shell blank 15, and avoids the complete locking phenomenon caused by excessive friction between the punch 1 and the TC4 titanium alloy slab 14 during the pressing process.

[0180] Step 5, after the isothermal forming is completed, the assembly C is taken out, and the TC4 titanium alloy shell blank 15 is separated from the die 2, thereby obtaining the TC4 titanium alloy shell blank 15; the width of each step on the tower-shaped structure 16 formed by rough processing is about 8 to 10 mm, and the height of each step is about 10 to 12 mm;

[0181] Step 6, subjecting the TC4 titanium alloy shell blank 15 obtained in step 5 to vacuum annealing heat treatment, with a holding temperature of 800° C., an error of no more than ±5° C., and a holding time of 120 min;

[0182] Step 7, rough machining the TC4 titanium alloy shell blank 15 after vacuum annealing heat treatment in step 6 to form a tower structure 16, such as Fig.10 As shown;

[0183] Step 8, performing vacuum annealing heat treatment on the tower-shaped structure 16 after rough processing in step 7, with a holding temperature of 750° C., an error of no more than ±5° C., and a holding time of 90 minutes;

[0184] The combination of two vacuum annealing heat treatments before and after rough machining of the TC4 titanium alloy shell blank 15 and the tower-shaped profile 16 formed by rough machining can effectively eliminate the residual stress inside the TC4 titanium alloy shell blank 15, avoid local deformation caused by stress release during machining, and ensure the wall thickness uniformity of the TC4 titanium alloy shell 17 with large wall thickness and complex structure.

[0185] Step 9, finishing the tower-shaped structure 16 after vacuum annealing heat treatment in step 8, so as to obtain a TC4 titanium alloy shell 17 with a large wall thickness and complex structure, and the wall thickness deviation is ≤0.10mm.

[0186] In this embodiment, by adopting an integrated isothermal forming tool, the TC4 titanium alloy shell blank is isothermally formed by the TC4 titanium alloy sheet blank, which greatly improves the forming efficiency and raw material utilization rate of the TC4 titanium alloy shell blank, and reduces the manufacturing cycle and cost of the TC4 titanium alloy shell. In addition, by accurately designing the blank and the mold, and matching reasonable isothermal hot pressing forming temperature, hot pressing rate and other process parameters, the wall thickness thinning and cracking phenomenon in the isothermal hot pressing forming process of the TC4 titanium alloy shell is eliminated, and the forming quality of the TC4 titanium alloy shell with large wall thickness and complex structure is guaranteed. Combined with the vacuum annealing heat treatment before and after rough machining and the reasonable rough machining profile design, the residual stress inside the TC4 titanium alloy shell blank is effectively eliminated, the local deformation caused by stress release during the mechanical machining process is avoided, and the wall thickness uniformity of the TC4 titanium alloy shell with large wall thickness and complex structure is guaranteed, and the wall thickness deviation is ≤0.10mm. The operation process of the present invention is simple and efficient, suitable for batch processing, and has strong operability and practicality.

[0187] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. Isothermal forming tooling for TC4 titanium alloy shell with large wall thickness and complex structure, characterized by: It comprises a male die (1), a female die (2), two support seats (3), a base (4) and two centering rods (5); wherein: The male mold (1) is fixedly connected to the upper platform of the hot pressing equipment; The support seat (3) is an arc-shaped structure with variable wall thickness, and two support seats (3) are fixed on the base (4) in a mirror-symmetrical manner, and are used to support and fix the die (2); The concave die (2) is a hollow cylinder with variable wall thickness, and the hollow cylinder cooperates with the convex die (1); The base (4) is a circular solid thick plate; a plurality of symmetrically distributed U-shaped through grooves B (106) are provided on the edge of the thick plate for fixedly connecting with the lower platform of the hot pressing equipment; The centering rod (5) is a straight rod, and is used for centering the punch (1), the die (2), and the support seat (3); The punch (1) is a hollow structure, comprising a boss (101), a punch upper section (102), a punch middle section (103) and a punch lower section (104), wherein the boss (101) and the punch upper section (102) are columnar structures, the punch middle section (103) is a conical structure, and the punch lower section is an arc structure; the boss (101) is a columnar structure, and the edge of the column is provided with a plurality of symmetrically distributed U-shaped through grooves A (105) for fixed connection with the upper platform of the hot pressing equipment; a plurality of first through holes (6) are evenly distributed on the end surface of the boss for centering the punch (1) and the die (2); and a side hole (8) is provided on the circumference of the punch upper section (102) for fixing a thermocouple.

2. The isothermal forming tool for a titanium alloy shell with a large wall thickness and a complex structure according to claim 1, characterized in that: The die (2) comprises an upper die section (201) and a lower die section (202); the outer diameters of the upper die section (201) and the lower die section (202) are the same, and the inner diameter of the upper die section (201) is larger than the inner diameter of the lower die section (202); a plurality of second through holes (9) are evenly distributed on the top surface of the lower die section (202), which match the first through holes (6) of the punch (1) and are used for centering the punch (1) and the die (2); and two lifting ears (10) are symmetrically arranged on the circumference of the upper die section (201) for lifting.

3. The isothermal forming tool for a titanium alloy shell with a large wall thickness and a complex structure according to claim 2, characterized in that: The support seat (3) is an arc structure, comprising an upper support seat section (301) and a lower support seat section (302); wherein the wall thickness of the upper support seat section (301) is smaller than the wall thickness of the lower support seat section (302); two support seat lifting ears (11) are symmetrically distributed in the circumferential direction of the lower support seat section (302) for lifting; two holes (12) are symmetrically distributed at the top of the lower support seat section (302), the holes (12) match the corresponding positions of the first through hole (6) of the punch (1) and the second through hole (9) of the die (2), and are used for centering the punch (1), the die (2) and the support seat (3); a second side hole (13) is provided on the circumference of the lower support seat section (302) for fixing a thermocouple.

4. The isothermal forming tool for a titanium alloy shell with a large wall thickness and a complex structure according to claim 3 is characterized by: The arc centers of the plurality of U-shaped through grooves A (105) are located on a concentric circle, the diameter of the concentric circle is Φ550-580 mm and is concentric with the surface of the boss (101); The outer diameter of the boss (101) is Φ600-700 mm, the inner diameter of the boss (101) is Φ90-100 mm, and the height of the boss (101) is 50-60 mm; The centers of the first through holes (6) are all on a circle with a diameter of Φ490-500 mm, and the circle is concentric with the boss (101); The outer diameter of the punch upper section (102) is Φ380-400 mm, and the inner diameter of the punch upper section (102) is consistent with the inner diameter of the boss (101); the height of the punch upper section (102) is 200-230 mm; the guide fillet angle at the connection between the boss (101) and the punch upper section (102) is R10-20 mm; The cone angle of the cone structure of the middle section (103) of the punch is 4-5 degrees; the guide fillet angle of the connection between the middle section (103) of the punch and the upper section (102) of the punch is R50-60mm; The outer diameter of the middle section of the punch (103) is Φ320-350 mm, and the inner diameter of the middle section of the punch (103) is consistent with the inner diameter of the upper section of the punch (102); the height of the middle section of the punch (103) is 45-60 mm; The lower section (104) of the punch is a solid structure, and the outer diameter of the lower section (104) of the punch is 10 to 12 mm smaller than the minimum inner diameter of the TC4 titanium alloy shell (17); The lower section (104) of the punch is provided with a centering structure (22); the profile of the lower section (104) of the punch is conical, and the cone angle is 35 to 50 degrees; the height of the arc portion of the lower section (104) of the punch is half of the outer diameter of the arc; and the guide fillet angle at the connection between the middle section (103) of the punch and the lower section (104) of the punch is R20 to 30 mm.

5. The isothermal forming tool for a titanium alloy shell with a large wall thickness and a complex structure according to claim 4 is characterized in that: The maximum outer diameter of the lower section of the punch (104) and the inner diameter of the lower section of the die (202) are as follows: D 10 =D0+△D0 D 11 =D1+△D1 △D0=A×D0×T △D1=A×D1×T Among them, D 10 D is the maximum outer diameter of the solid arc at the forming temperature of the lower section of the punch (104), 11 is the inner diameter of the hollow cylinder of the lower section of the die (202) at the forming temperature; T is the isothermal forming temperature; A is the thermal expansion coefficient of the materials of the punch (1) and the die (2); D0 and D1 are respectively the outer diameter of the solid arc of the lower section of the punch (1) and the inner diameter of the hollow cylinder of the lower section of the die (2) at room temperature.

6. A method for isothermal forming and wall thickness control of a TC4 titanium alloy shell with a large wall thickness and complex structure, characterized in that: include: Isothermal forming tooling for manufacturing TC4 titanium alloy shells with large wall thickness and complex structure; Designing and preparing TC4 titanium alloy slab (14); Assembling a TC4 titanium alloy shell isothermal forming tool and a plate blank (14), and fixing them to a hot pressing device; The side door of the hot pressing equipment is closed to form a closed space, and the isothermal forming tooling and the slab (14) in the hot pressing equipment are subjected to a temperature increase and heat preservation treatment; Starting isothermal forming until the TC4 titanium alloy slab (14) is formed into a TC4 titanium alloy shell blank (15) with a large wall thickness and a complex structure; After the isothermal forming is completed, the TC4 titanium alloy shell blank (15) is separated from the isothermal forming tool to obtain the TC4 titanium alloy shell blank (15); The TC4 titanium alloy shell blank (15) is subjected to vacuum annealing heat treatment at a holding temperature of 745 to 805° C. for a holding time of 90 to 120 minutes; Rough machining is performed on the TC4 titanium alloy shell blank (15) after vacuum annealing heat treatment to form a tower-shaped structure (16); The tower-shaped structure (16) is subjected to vacuum annealing heat treatment, with the holding temperature being 745 to 805° C. and the holding time being 90 to 120 minutes; The tower-shaped structure (16) is finely processed after vacuum annealing heat treatment to obtain a TC4 titanium alloy shell (17) with a large wall thickness and complex structure.

7. The isothermal forming and wall thickness control method of a titanium alloy shell with a large wall thickness and complex structure according to claim 6 is characterized in that: The maximum thickness of the TC4 titanium alloy slab (14) during the isothermal forming process is t1=t0+Δt, Δt=B×t0×T; t0 is the thickness of the TC4 titanium alloy slab (14) at room temperature; When D 11 -D 10 When -2×t1=0.2~0.3mm, the wall thickness of the TC4 titanium alloy slab (14) at room temperature is designed to be t0=[1.014475(D1-D0)-(D 11 -D 10 -2×t1)] / 2.015045; The outer diameter of the TC4 titanium alloy slab (14) at room temperature is Φ500-600 mm. The upper end surface of the TC4 titanium alloy slab (14) is provided with a concave structure that matches the lower centering structure (22) of the punch (1).

8. The isothermal forming and wall thickness control method of a titanium alloy shell with a large wall thickness and complex structure according to claim 6, characterized in that: The TC4 titanium alloy shell isothermal forming tooling and the plate blank (14) are assembled and fixedly connected with the hot pressing equipment, specifically: The arc surface of the support seat (3) corresponds to the side of the base (4) without the U-shaped through groove B (106), and the two support seats (3) and the base (4) are fixedly connected by welding to form an assembly A; The centering rod (5) passes through the second through hole (9) of the die (2) and the hole (12) of the lower section (302) of the support seat in sequence, so as to realize the centering of the assembly A and the die (2); The male mold (1) is fixedly mounted on the upper platform of the hot pressing equipment; The assembly A is fixedly mounted on the lower platform of the hot pressing equipment; Bringing the assembly A into contact with the concave die (2) to form the assembly B; The centering rod (5) is sequentially passed through the first through hole (6) of the male mold (1), the second through hole (9) of the female mold (2) and the hole (12) of the lower section (302) of the support seat to achieve centering between the male mold (1), the female mold (2) and the assembly A; Placing a TC4 titanium alloy slab (14) on the top of the hollow cylinder of the lower section (202) of the die; The lower end surface of the TC4 titanium alloy slab (14) contacts the top end surface of the hollow cylinder of the lower section of the die (202) to form a combined part C.

9. The isothermal forming and wall thickness control method of a titanium alloy shell with a large wall thickness and complex structure according to claim 6 is characterized in that: The isothermal forming tooling and the slab (14) in the hot pressing equipment are subjected to a heating and heat preservation treatment, specifically: the heating rate of the hot pressing equipment is 40-50°C / h, until the inner cavity temperature of the hot pressing equipment reaches 745-755°C, and the heat preservation treatment is performed, and the temperature of the inner cavity of the hot pressing equipment is always maintained in the range of 750±5°C, and the heat preservation time is 50-70min.

10. The isothermal forming and wall thickness control method of a titanium alloy shell with a large wall thickness and complex structure according to claim 6, characterized in that: Isothermal forming is started until the TC4 titanium alloy slab (14) is formed into a TC4 titanium alloy housing blank (15) with a large wall thickness and a complex structure, specifically: The centering structure (22) of the lower section of the punch (104) is brought into contact with the concave pit provided on the upper end surface of the TC4 titanium alloy slab (14); before the punch (1) contacts the TC4 titanium alloy slab (14), the pressing rate is 30 to 50 mm / min; after the punch (1) contacts the TC4 titanium alloy slab (14), the pressing rate of the punch (1) is adjusted to 20 to 25 mm / min, and the punch (1) maintains the same pressing rate during the subsequent isothermal forming process; As the punch (1) moves downward, the punch lower section (104) and the punch middle section (103) sequentially contact the TC4 titanium alloy slab blank (14) to form a TC4 titanium alloy shell blank (15).

11. The isothermal forming and wall thickness control method of a titanium alloy shell with a large wall thickness and complex structure according to claim 6, characterized in that: The tower-like structure (16) comprises a plurality of steps, each step having a width of 8 to 10 mm and a height of 10 to 12 mm.

12. The isothermal forming and wall thickness control method of a titanium alloy shell with a large wall thickness and complex structure according to claim 6, characterized in that: The wall thickness deviation of the TC4 titanium alloy shell (17) with a large wall thickness and a complex structure is less than or equal to 0.10 mm.

Images