Thermal expansion forming die and forming method for titanium alloy thin-walled cylindrical parts with an angled rotation centerline

Abstract

The present invention discloses a hot expansion forming die and forming method for a titanium alloy thin-walled cylindrical part with an angled centerline of rotation. The hot expansion forming die includes a first lower template, a guide block, a limiting ring, a guide block, a limiting pin, an expansion block, a cone, and a limiting ring. A titanium alloy sheet is used as a blank, and multiple identical hot-stretched parts are processed by hot stretching. The same cut parts are cut from each hot-stretched part, and the multiple cut parts are welded to form a hot expansion blank with a single rotation axis. The hot expansion blank is sleeved on the outside of the expansion block of the hot expansion forming die, and hot expansion is performed on a hot press. Finally, the end face is trimmed to obtain the outer wall section. The titanium alloy thin-walled cylindrical part with an angled centerline of rotation obtained by the present invention has good formability, high precision, no springback, and no residual stress.

Description

Technical Field

[0001] The invention belongs to the field of mechanical processing, and in particular relates to a thermal expansion forming die and a forming method for a titanium alloy thin-walled cylinder part of an aero-engine whose rotation center line is at an angle. Background Art

[0002] like Figure 1 The figure shows an aircraft engine outer wall section made of titanium alloy with a wall thickness of t (t ≤ 5mm). The outer wall section 1 is a thin-walled cylindrical component (D2 = 2R) formed by a spherical transition between a cylindrical section with a lower diameter of D2 and a conical section with an upper diameter of D1. The distance from the lowest point of the outer wall section 1 end face to the bottom of the cylindrical section at the lower end of D2 is Hmin, and the distance from the highest point of the outer wall section 1 end face to the bottom of the cylindrical section at the lower end of D2 is Hmax. The angle between the centerlines of rotation of the cylindrical and conical sections is α. The technical specifications for the part require no more than six longitudinal welds.

[0003] Titanium alloys are tough and viscous at room temperature, exhibit poor moisture and heat conductivity, have a low elastic modulus, and exhibit strong chemical affinity. Therefore, forming titanium alloy parts at room temperature is difficult. Due to the angle between the centerline of rotation of the part, each cross-section along the part's axis varies, making it difficult to control the part's profile using traditional bulge forming methods. Parts also have a tapered shape, making them prone to upward movement during bulging. Horizontal friction during the bulging process often results in the lower end of the part being sized correctly, but the upper end being oversized or even exceeding tolerances, creating a "head-down" phenomenon. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention aims to provide a hot expansion forming die and forming method for titanium alloy thin-walled cylindrical parts with an angled rotation center line, so as to improve the forming quality and precision of such titanium alloy parts.

[0005] The basic forming idea of ​​the present invention is: by designing and manufacturing a special hot expansion forming mold, adding a guide block between the expansion block and the first lower template, adding a limit pin at the lower end of the expansion block surface to prevent upward movement, changing the force point of the expansion block, etc., the defects existing in the expansion of the traditional expansion mold are eliminated, and titanium alloy parts with the advantages of good formability, high precision, no rebound, and no residual stress are obtained.

[0006] The present invention adopts the following technical solutions:

[0007] The hot expansion forming die for titanium alloy thin-walled cylindrical parts with an angled rotation centerline includes:

[0008] A first lower template, wherein the upper end surface of the first lower template is provided with a circular hole and a T-shaped slot, and the T-shaped slots are distributed on a radial line of a circle with the center of the circular hole as the center, and the center angles between adjacent T-shaped slots are equal;

[0009] a first guide block and a second guide block, wherein the first guide block and the second guide block are both slidably connected in the T-shaped slot, and one end of the first guide block is marked with a scale line;

[0010] An expansion block, wherein the outer surface of the expansion block is consistent with the inner surface of the titanium alloy thin-walled cylindrical part at an angle to the rotation center line, the inner surface of the expansion block is a conical surface, the number of expansion blocks is greater than or equal to two, wherein the upper end surfaces of the two expansion blocks are respectively marked with engraved lines corresponding to the low points and the high points of the titanium alloy thin-walled cylindrical part at an angle to the rotation center line, the upper end surface of the expansion block is also provided with a circular boss, the lower end of the expansion block is respectively connected to the first guide block and the second guide block through a connecting piece, and a positioning hole is also provided on the outer surface of the expansion block;

[0011] A limit pin, the limit pin being plugged into the positioning hole of the expansion block;

[0012] A cone, the cone being inserted into the cone formed by the inner surfaces of the plurality of expansion blocks;

[0013] A first limiting ring, which is a circular ring-shaped part and is placed in the circular hole of the first lower template;

[0014] The second limiting ring, the second limiting ring, the second limiting ring is a circular ring with a boss on the outer ring. When the cone is plugged into the cone formed by the inner surfaces of multiple expansion blocks, the second limiting ring is sleeved on the cone, and the end face of the boss on the second limiting ring does not contact the upper end face of the expansion block. The inner ring diameter of the circular ring of the second limiting ring satisfies that when the side surface of the circular boss on the expansion block contacts the inner surface of the outer ring boss on the second limiting ring, the inner ring diameter of the circular ring on the second limiting ring is larger than the inner diameter of the circular boss of the expansion block.

[0015] Furthermore, when the plurality of expansion blocks converge toward the circular hole on the first lower template along with the first guide block and the second guide block and the first guide block and the second guide block touch the first limiting ring in the circular hole, a separation gap is formed between the outer surfaces of adjacent expansion blocks. The separation gap can ensure that the expansion blocks are retracted into place.

[0016] Furthermore, a weight-reducing groove is provided on the lower end surface of the expansion block, and a reinforcing rib is provided in the weight-reducing groove.

[0017] Furthermore, the expanded surface of the multiple expansion blocks is the surface after the inner surface of the titanium alloy thin-walled cylindrical part with the rotation center line is divided by the equal center angle, that is, with the rotation center line of the part as the center, the inner surface of the outer wall section is divided into multiple parts by the equal center angle.

[0018] A method for forming a titanium alloy thin-walled cylindrical part with an angled rotation centerline using the aforementioned thermal expansion forming die comprises the following steps:

[0019] Step 1: Using a titanium alloy sheet as a blank, a plurality of identical curved hot-drawn parts with convex surfaces are processed by hot-drawing forming, wherein the convex surface of the hot-drawn parts includes at least a first spherical surface having a radius equal to that of the spherical surface SR on the outer wall segment;

[0020] Step 2: Cut each hot-stretched part along the same cutting path to obtain multiple identical cut parts containing the first spherical surface;

[0021] Step 3: Splice the multiple cut parts and weld them along the splicing line to form a single rotary axis hot-expanded blank. It should be noted that, under the premise of ensuring that the hot-expanded blank can be normally inserted into the hot-expanding forming die, the circumferential size of the hot-expanded blank after welding should not be too large, and sufficient expansion deformation must be retained to ensure that the size of the hot-expanded surface is the same as that of the outer wall segment.

[0022] Step 4, the hot-bulging blank is sleeved on the outer side of the expansion block of the aforementioned hot-bulging forming die and then hot-bulged;

[0023] In step 5, the hot-expanded part is marked using the engraved lines corresponding to the low and high points on the expansion block after hot expansion in step 4, as well as the engraved line marked on one end of the first guide block. The end face of the hot-expanded part is then cut using the heights Hmin and Hmax. This ultimately results in a titanium alloy thin-walled cylindrical part with an angled rotational centerline. For example, using the engraved lines corresponding to the low and high points on the expansion block, as well as the engraved line marked on one end of the first guide block, the characteristic cross-section of the outer wall section, containing the low and high points and passing through the axis of the cylindrical section in the outer wall section, is obtained using the "three points determine a plane" principle. Using this cross-section as a reference, the angle α is determined using the heights Hmin and Hmax, and end face cutting is performed. Using three engraved lines (the low and high point engraved lines on the two expansion blocks, and the engraved line on the end face of the first guide block) to mark and identify the characteristic points of the hot-expanded part facilitates alignment during subsequent end face cutting.

[0024] Furthermore, in step 1, the hot stretching die includes a second lower die plate, a punch, a blank holder, and a die, wherein:

[0025] The second lower template is provided with a push rod hole;

[0026] The top and side surfaces of the punch are in the same shape as the inner surface of the hot-stretched part. The punch is connected to the second lower template via a fastener, and an avoidance groove is provided at the lower end of the side surface of the punch.

[0027] There is a gap between the inner ring of the blank holder and the punch, and the height of the blank holder after being lifted is higher than the top surface of the punch;

[0028] The inner cavity and lower end surface of the die are consistent with the outer surface of the hot-stretched part.

[0029] As an option, in step 1, the hot stretching die is installed on the workbench of the hot press, the position of the push rod hole of the second lower template is consistent with the position of the push rod hole of the hot press, and it is ensured that the push rod can lift the pressure ring to move up and down, the hot press and the hot stretching die are heated to 600℃~800℃, the hot stretching die is opened, the pressure ring is moved upward to be flush with the top surface of the punch, the blank is placed on the pressure ring, the outer end face of the blank is aligned with the support plate, and the part is pressed after preheating, and the temperature is lowered after maintaining the pressure. When the temperature drops to 200℃~400℃, the part is taken out and placed on a cooling pad for natural cooling.

[0030] As an option,

[0031] In step 2, a limiting hole corresponding to the positioning hole on the expansion block is machined on the cut part, or in step 3, a limiting hole corresponding to the positioning hole on the expansion block is machined on the hot-expanded blank;

[0032] In step 4, the limiting pin is inserted into the positioning hole on the expansion block and the limiting hole on the hot expansion blank at the same time.

[0033] As an option, in step 4, the cone in the hot expansion forming mold is taken out, the expansion block is folded and inserted into the hot expansion blank, the limit pin is inserted into the positioning hole on the expansion block and the limit hole on the hot expansion blank at the same time, and then the cone is installed.

[0034] Furthermore, in step 4, thermal expansion is performed on a hot press, the hot expansion forming mold is installed on the hot press workbench, the hot press and the hot expansion forming mold are heated to 600°C to 800°C, the hot expansion is started, and the pressure is maintained for a period of time before cooling; when the temperature drops to 200°C to 400°C, the part is taken out and placed on a cooling pad to cool naturally.

[0035] As an option,

[0036] In the step 1, before hot stretching, a Ti protective coating and a lubricating coating are sequentially applied to the surface of the blank and the hot stretching die;

[0037] In step 4, before the hot expansion, the Ti protective coating and the lubricating coating are sequentially applied on the hot expansion blank and the surface of the hot expansion forming die.

[0038] The forming method and mold of the present invention have the following characteristics:

[0039] (1) The force point of the expansion block in the traditional bulging die is changed, and a second limiting ring is designed. The second limiting ring is a circular ring with a boss on the outer ring. When the expansion block expands to the limit position, the inner diameter of the circular ring on the second limiting ring maintains a gap (about 0.1 to 1 mm) with the diameter of the circular boss of the expansion block. At this time, the expansion block is in the final state. The aforementioned gap ensures that the second limiting ring and the cone do not act radially. Only the second limiting ring contacts the side surface of the circular boss of the expansion block (the side surface of the outer ring) through the inner surface of the boss in the radial direction, generating a radial force, which makes the upper end of the expansion block shrink, and the center of gravity is closer to the axis than the traditional bulging die, which can effectively prevent the "upside-down" phenomenon of the product cylindrical parts with "the upper end size is too large and the lower end size is too small";

[0040] (2) A limit pin is added to prevent the expansion block from moving upward during the thermal expansion process;

[0041] (3) Split the entire forming process into two parts: thermal stretching and thermal expansion, reasonably distribute the deformation amount of forming, and eliminate the deformation stress generated during forming;

[0042] (4) Processing a part with a single rotation axis into a part with two rotation axes by cutting the end face, accurately ensuring the angle between the rotation center lines;

[0043] (5) The cutting reference is determined by the three engraved lines on the hot expansion forming die (corresponding to the highest point, lowest point and bottom surface respectively), which is simple and easy to operate;

[0044] (6) By hot stretching to form multiple identical parts, and then cutting and welding them into hot-expanded blanks with a single rotary axis, the force during the expansion process is uniform and the quality of the hot-expanding forming is guaranteed.

[0045] Compared with the prior art, the present invention proposes a hot expansion forming die and forming method for titanium alloy thin-walled cylindrical parts with an angled centerline, which improves the forming quality and precision of such titanium alloy parts and meets the needs of aircraft engine development. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is the main view of the outer wall segment;

[0047] Figure 2 It is an axonometric view of the hot-stretched part after hot-stretching treatment;

[0048] Figure 3 It is the main view of the cut part obtained by cutting along the dotted line on the basis of the hot-stretched part;

[0049] Figure 4 It is the AA section view of the part after cutting;

[0050] Figure 5 It is the main view of the hot-expanded blank part;

[0051] Figure 6 Schematic diagram of the hot stretching die structure;

[0052] Figure 7 2. It is a schematic diagram of the structure of the thermal expansion forming die;

[0053] Figure 8 This is the axonometric drawing of the first lower template;

[0054] Figure 9 is an axonometric view of the first guide block;

[0055] Figure 10 It is an axonometric view of the second guide block;

[0056] Figure 11 It is an axonometric drawing of the expansion block;

[0057] In the figure, 1-outer wall section; 2-hot-stretched part; 3-part after cutting; 4-hot-expanded blank; 5-second lower template; 6-punch; 7-blank holder; 8-die; 9-first lower template; 10-first guide block; 11-first limiting ring; 12-second guide block; 13-limiting pin; 14-expansion block; 15-cone; 16-second limiting ring. DETAILED DESCRIPTION

[0058] The present invention is further described below with reference to the accompanying drawings and specific embodiments. However, it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various modifications, substitutions and changes made according to common technical knowledge and customary means in the field are included in the scope of the present invention.

[0059] like Figure 1 As shown, it is a titanium alloy thin-walled cylindrical part with an angled rotation centerline that needs to be formed. Figure 1 The figure shows the shape characteristics of the outer wall section 1 of this part. The part is made of titanium alloy with a thickness of t (t≤5mm). It is a thin-walled cylindrical component formed by a cylindrical section with a lower diameter of D2 and a conical section with an upper diameter of D1, transitioning through a spherical surface SR. The distance from the lowest point of the outer wall section 1 end face to the bottom of the lower cylindrical section D2 is Hmin, and the distance from the highest point of the outer wall section 1 end face to the bottom of the lower cylindrical section D2 is Hmax. The angle between the centerlines of rotation of the cylindrical and conical sections is α. The technical specifications for the part require no more than six longitudinal welds.

[0060] against Figure 1The rotation center line of the titanium alloy thin-walled cylindrical parts is angled. The processing idea of ​​the present invention is: using hot forming + cutting, specifically, first hot stretching out multiple identical curved surfaces (the curved surfaces include a spherical surface with the same radius as the SR spherical surface in the outer wall segment 1), and then welding them after cutting to form a blank with a single rotation center (the rotation center of the cylindrical segment), and then hot expansion forming is formed to form the surface of the outer wall segment 1 (including cylindrical surface, spherical surface and conical surface), and finally cutting the end face to obtain another rotation center (the rotation center of the conical segment).

[0061] The hot-stretched blank is a square flat plate, and the hot-stretched part 2 formed by stretching has the following structure: Figure 2 The shape of the outer convex surface of the hot-stretched part 2 is the same as the spherical surface SR on the outer wall segment 1, or at least a part of the outer convex surface is the same as the spherical surface SR (for example, the outer convex surface includes the same curved surface as the cylindrical surface, SR spherical surface and conical surface on the outer wall segment 1, or the outer convex surface only includes the same curved surface as the SR spherical surface on the outer wall segment 1. If the former is adopted, the deformation amount of subsequent hot expansion is relatively reduced, and if the latter is adopted, the deformation amount of subsequent hot expansion is relatively large). Then, the hot-stretched part 2 is pressed Figure 2 The middle dotted line position (cutting path) is cut into the cut part 3, Figure 2 The dotted line path is obtained by reverse calculation, that is, Figure 5 The hot-expanded blank 4 is evenly divided into multiple pieces along the circumferential surface, and the evenly divided single piece is used as a template to draw a sample, and the cut part 3 is cut out according to the sample, or the hot-stretched part 2 is marked according to the sample, and then the cut part 3 is cut out.

[0062] Hot stretching die Figure 6 It is mainly composed of a second lower template 5, a punch 6, a pressure ring 7, and a die 8. The material of the mold is medium silicon-molybdenum ductile iron.

[0063] According to the position of the ejector hole of the thermoforming equipment, a ejector hole is opened on the second lower template 5;

[0064] The top and side surfaces of the punch 6 are consistent with the inner surface of the hot-stretched part 2. The dimensions are scaled according to the linear expansion coefficient of the mold material and TA15, and the calculated scaling coefficient is 0.8 to 1. The punch 6 is connected to the second lower mold plate 5 by fasteners. A step is provided at the lower end of the side of the punch 6 to prevent the ejector from lifting.

[0065] The upper side wall of the inner ring of the blank holder 7 maintains a uniform gap of 1 to 2 mm with the punch 6; the lower side wall of the inner ring of the blank holder 7 maintains a uniform gap of 1 to 4 mm with the punch 6; the height of the blank holder 7 after lifting is higher than the top surface of the punch 6;

[0066] The inner cavity and lower end surface of the die 8 are consistent with the outer surface shape of the hot-stretched part 2, and the inner cavity and the punch 6 surface maintain a uniform gap t1, t1 = (1 ~ 1.5) t; a lifting device is installed on the outer side of the die 8 and the second lower template 5.

[0067] Press the hot stretched part 2 Figure 2 The dotted line position is cut into the cut part 3 (its main view is as follows Figure 3 , AA view as Figure 4 ), and then weld the six cut parts 3 to obtain a single rotary axis heat-expanded blank 4 (such as Figure 5 ).

[0068] Hot bulging forming die for hot bulging Figure 7 , consisting of a first lower template 9, a first guide block 10, a first limiting ring 11, a second guide block 12, a limiting pin 13, a swelling block 14, a cone 15, and a second limiting ring 16. The mold material is medium silicon-molybdenum ductile iron;

[0069] The first lower template 9 (see Figure 8 ) is a circular plate with a weight-reducing hole in the center of the circular plate; a stepped hole is formed in the center of the circular plate to accommodate the first limiting ring 11; the circular plate is provided with "T"-shaped grooves along the diameter direction and evenly distributed along the circumference direction; a lifting shaft is cast into the outer side of the circular plate;

[0070] The first guide block 10 (see Figure 9 ) is a "T"-shaped block, connected to the expansion block 14 by fasteners, and can slide radially in the "T"-shaped slot of the first lower template 9; the first guide block 10 maintains a gap of 1 to 4 mm with the first lower template 9; a small step is provided at one end, and a scoreline is provided on the step. During assembly, the scoreline corresponds to the high or low point of the part (or expansion block 14);

[0071] The first limiting ring 11 is a circular ring placed in the stepped hole of the first lower template 9, and its function is to limit the radial inward retraction distance of the expansion block 14;

[0072] The second guide block 12 (see Figure 10 ) is a "T"-shaped block, connected to the expansion block 14 by fasteners, and can slide radially in the "T"-shaped groove of the first lower template 9; the second guide block 12 maintains a gap of 1 to 4 mm with the first lower template 9;

[0073] The limit pin 13 is a waist-shaped pin. A corresponding waist-shaped hole is opened on the hot-bulging blank 4. The limit pin 13 is inserted into the waist-shaped hole of the hot-bulging blank 4 and the waist-shaped hole of the expansion block 14 to prevent the hot-bulging blank 4 from moving upward during the bulging process.

[0074] Expansion block 14 (see Figure 11) is consistent with the inner surface of the outer wall segment 1 (after extension), and the size is calculated based on the linear expansion coefficient of the mold material and TA15, with the calculated scaling coefficient being 0.8 to 1. The top surface of the expansion block 14 is engraved with lines corresponding to the high and low points of the outer wall segment 1; bolt holes are provided on the top for lifting; a circular boss is provided on the top; the internal material of the expansion block 14 is removed from the bottom surface, and reinforcing ribs are added; the expansion blocks 14 are evenly divided along the circumferential direction, with the dividing gaps sufficient to allow the expansion blocks 14 to shrink inward without hindering the insertion and installation of the thermal expansion blank 4; the inner side of the expansion block 14 is a conical surface with a taper of 2° to 10°. In the final state of mold closing, the conical surface is in contact with the cone 15.

[0075] The cone 15 is a cone with the same taper as the expansion block 14. In the final state of mold closing, the cone surface fits the expansion block 14. The top of the cone is a frustum. A weight-reducing hole is provided in the middle of the cone 15. When the cone 15 is pressed down, the contracted expansion block 14 is pushed outward. The bottom surface of the boss of the cone 15 contacts the second limiting ring 16 and stops moving.

[0076] The second limiting ring 16 is a circular ring with a boss on the outer ring. When the expansion block 14 expands outward to the limit position, the side surface of the circular boss on the expansion block 14 contacts the inner surface of the outer boss on the second limiting ring 16. At this time, the inner diameter of the circular ring on the second limiting ring 16 and the inner diameter of the circular boss on the expansion block 14 maintain a gap of 0.1 to 1 mm ( Figure 7 The gap is shown in the figure), so a radial force is applied to the side surface of the circular boss on the expansion block 14 at the inner surface of the outer ring boss on the second limiting ring 16, so that the upper end of the expansion block 14 remains tightened to avoid the "inverted head" phenomenon in which the lower end size of the outer wall section 1 after expansion is qualified but the upper end size is too large or even out of tolerance. The bottom surface of the boss does not contact the surface of the expansion block 14. This is to ensure the accuracy of the mold in the final state. Only one surface of the second limiting ring 16 and the expansion block 14 can be in contact, and the contact surface is the end surface of the circular boss on the expansion block 14;

[0077] The method for forming the outer wall segment 1 using the hot stretching and hot expansion forming mold as described above, the forming steps are as follows:

[0078] 1. Blanking: Use titanium alloy parts to cut the blank. The blank is a square sheet. The sheet size is calculated by adding the expanded size of the part to the processing allowance.

[0079] 2. Apply anti-oxidation layer and graphite layer: Use a brush to apply Ti1# protective layer (anti-oxidation coating to prevent titanium alloy parts from oxidizing at high temperatures) on the upper and lower surfaces of the blank and the working surface of the hot stretching die. After the blank surface and the working surface of the hot stretching die are dry at room temperature, apply graphite solution lubricant on the blank and die surface and dry naturally at room temperature.

[0080] 3. Hot forming: Forming is carried out on a hot press. The hot stretching die is installed on the workbench of the hot press. The position of the ejector hole of the second lower template 5 is consistent with the position of the ejector hole of the hot press. Ensure that the ejector can lift the blank holder 7 up and down. Heat the hot press and the hot stretching die to 600℃~800℃, open the hot stretching die, move the blank holder 7 upward until it is flush with the upper end surface of the punch 6, place the blank on the blank holder 7, align the outer end surface of the blank with the support plate, preheat for 10 minutes, press the part, and press it with a pressure of 20Mpa. After holding the pressure for 10 minutes, cool it down. When the temperature drops to 200℃~400℃, take out the hot stretched part 2 and place it on a cooling pad to cool naturally.

[0081] 4. Remove graphite and clean hot-drawn parts 2;

[0082] 5. Cutting: cutting the hot-stretched part 2 into the cut part 3;

[0083] 6. Weld the six cut parts 3 to obtain a thermal expansion blank 4;

[0084] 7. Apply anti-oxidation layer and graphite layer: Use a brush to apply Ti1# protective layer (anti-oxidation coating to prevent titanium alloy parts from oxidizing at high temperatures) on the upper and lower surfaces of the hot expansion blank 4 and the working surface of the hot expansion forming mold. After the surfaces of the hot expansion blank 4 and the working surface of the hot expansion forming mold are dried at room temperature, apply graphite solution lubricant on the surfaces of the hot expansion blank 4 and the working surface of the hot expansion forming mold and dry naturally at room temperature.

[0085] 8. Load the bulge blank 4: Remove the cone 15, retract the expansion block 14, and insert the bulge blank 4. Insert the limit pin 13 and load the cone 15. Under the action of gravity, the cone 15 expands the expansion block 14 outward until it can no longer be pushed.

[0086] 9. Hot bulging: bulging is performed on a hot press. The hot bulging die is installed on the hot press workbench. The hot press and the hot bulging die are heated to 600°C to 800°C. The die is pressed with a pressure of 2Mpa to 20Mpa. The pressure is maintained for 5min to 20min and then the temperature is lowered. When the temperature drops to 200°C to 400°C, the bulging block 14 is folded in and the part is taken out. The part is placed on a cooling pad and cooled naturally. Before taking out the part, marks corresponding to the high and low point marks on the bulging block 14 and the marks on the end face of the first guide block 10 are made on the upper side of the part surface to identify the high and low point positions of the part, which is convenient for alignment when cutting the upper and lower ends of the part.

[0087] 10. Remove graphite and clean parts;

[0088] 11. Cutting edge: Combined Figure 1Use the height Hmin, height Hmax, and the high point, low point, and lower end position marks marked on the part in step 9 to cut the upper and lower end faces of the part to obtain the outer wall segment 1 with an angled center of rotation.

[0089] Any matters not described in detail in the present specification are prior art known to those skilled in the art. Although the above description of the present invention is based on illustrative embodiments to facilitate understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the specific embodiments. As long as various modifications are within the spirit and scope of the present invention as defined and determined by the appended claims, such modifications will be obvious to those skilled in the art, and all inventions and creations utilizing the concepts of the present invention are protected.

Claims

1. The hot expansion forming die for titanium alloy thin-walled cylindrical parts with an angled centerline is characterized by: include, A first lower template (9), wherein the upper end surface of the first lower template (9) is provided with a circular hole and a T-shaped slot, and the T-shaped slots are distributed on a radial line of a circle with the center of the circular hole as the center, and the center angles between adjacent T-shaped slots are equal; A first guide block (10) and a second guide block (12), wherein the first guide block (10) and the second guide block (12) are both slidably connected in the T-shaped slot, and one end of the first guide block (10) is marked with a scale line; An expansion block (14), wherein the outer surface of the expansion block (14) is consistent with the inner surface of the titanium alloy thin-walled cylindrical part at an angle to the rotation center line, the inner surface of the expansion block (14) is a conical surface, the number of the expansion blocks (14) is greater than or equal to two, wherein the upper end surfaces of the two expansion blocks (14) are respectively marked with a scale line corresponding to the low point of the titanium alloy thin-walled cylindrical part at an angle to the rotation center line and a scale line corresponding to the high point, the upper end surface of the expansion block (14) is also provided with a circular boss, the lower end of the expansion block (14) is respectively connected to the first guide block (10) and the second guide block (12) through a connecting piece, and a positioning hole is also provided on the outer surface of the expansion block (14); A limit pin (13), wherein the limit pin (13) is plugged into a positioning hole of the expansion block (14); A cone (15), wherein the cone (15) is inserted into the cone formed by the inner surfaces of the plurality of expansion blocks (14); A first limiting ring (11), which is a circular ring-shaped part and is placed in the circular hole of the first lower template (9); The second limiting ring (16) is a circular ring with a boss on the outer ring. When the cone (15) is plugged into the cone formed by the inner profiles of the plurality of expansion blocks (14), the second limiting ring (16) is sleeved on the cone (15), and the boss end face on the second limiting ring (16) does not contact the upper end face of the expansion block (14). The inner diameter of the circular ring of the second limiting ring (16) satisfies that when the side surface of the circular boss on the expansion block (14) contacts the inner surface of the outer boss on the second limiting ring (16), the inner diameter of the circular ring on the second limiting ring (16) is larger than the inner diameter of the circular boss on the expansion block (14). When the expansion block (14) expands to the limit position, the inner diameter of the circular ring on the second limiting ring (16) maintains a gap with the diameter of the circular boss on the expansion block (14). The gap ensures that the second limiting ring (16) and the cone (15) do not act radially.

2. The hot expansion forming die for titanium alloy thin-walled cylindrical parts with an angled centerline according to claim 1, characterized in that: When the plurality of expansion blocks (14) gather toward the circular hole on the first lower template (9) along with the first guide block (10) and the second guide block (12), and the first guide block (10) and the second guide block (12) touch the first limiting ring (11) in the circular hole, there is a dividing gap between the outer surfaces of adjacent expansion blocks (14).

3. The hot expansion forming die for titanium alloy thin-walled cylindrical parts with an angled rotation centerline according to claim 1, characterized in that: The lower end surface of the expansion block (14) is provided with a weight-reducing groove, and a reinforcing rib is provided in the weight-reducing groove.

4. A method for forming a titanium alloy thin-walled cylindrical part with an angled rotation centerline using the hot expansion forming die of claim 1, characterized in that: include, Step 1, using a titanium alloy plate as a blank, and processing a plurality of identical curved hot-stretched parts (2) with convex surfaces by hot stretching, wherein the convex surface of the hot-stretched parts (2) includes at least a first spherical surface having a radius equal to that of the upper spherical surface SR of the outer wall section (1); Step 2, cutting each hot-stretched part (2) along the same cutting path to obtain a plurality of identical cut parts (3) containing the first spherical surface; Step 3, splicing the multiple cut parts (3) and welding them along the splicing line to form a heat-expanded blank (4) with a single rotation axis; Step 4, the hot expansion blank (4) is sleeved on the outside of the expansion block (14) of the hot expansion forming die of claim 1 and then hot expansion is performed; Step 5, marking the part after hot expansion by the engraved lines corresponding to the low point and the high point on the expansion block (14) after hot expansion in step 4 and the engraved lines marked on one end of the first guide block (10), and performing end face cutting on the part after hot expansion in combination with the height Hmin and the height Hmax, and finally obtaining a titanium alloy thin-walled cylindrical part with an angled centerline, wherein the height Hmin is the distance from the low point of the end face of the outer wall section (1) to the bottom face of the lower end D2 cylindrical section, and the height Hmax is the distance from the high point of the end face of the outer wall section (1) to the bottom face of the lower end D2 cylindrical section; In the step 2, a limiting hole corresponding to the positioning hole on the expansion block (14) is machined on the cut part (3), or in the step 3, a limiting hole corresponding to the positioning hole on the expansion block (14) is machined on the hot-expanded blank (4); In step 4, the limiting pin (13) is simultaneously inserted into the positioning hole on the expansion block (14) and the limiting hole on the hot-expanded blank (4); In step 4, the cone (15) in the hot expansion forming mold is taken out, the expansion block (14) is folded and then inserted into the hot expansion blank (4), the limit pin (13) is simultaneously inserted into the positioning hole on the expansion block (14) and the limit hole on the hot expansion blank (4), and then the cone (15) is installed.

5. The forming method of a titanium alloy thin-walled cylindrical part with an angled centerline according to claim 4, characterized in that: In step 1, the hot stretching die comprises a second lower die plate (5), a punch (6), a blank holder (7) and a die (8), wherein: The second lower template (5) is provided with a push rod hole; The top and side surfaces of the punch (6) are in the same shape as the inner surface of the hot-stretched part (2), the punch (6) is connected to the second lower mold plate (5) via a fastener, and a relief groove is provided at the lower end of the side surface of the punch (6); There is a gap between the inner ring of the blank holder (7) and the punch (6), and the height of the blank holder (7) after being lifted is higher than the top surface of the punch (6); The inner cavity and lower end surface of the die (8) are consistent with the outer surface of the hot-stretched part (2).

6. The forming method of a titanium alloy thin-walled cylindrical part with an angled centerline according to claim 4, characterized in that: In the step 1, the hot stretching die is mounted on the workbench of the hot press, the position of the ejector pin hole of the second lower template (5) is consistent with the position of the ejector pin hole of the hot press, and it is ensured that the ejector pin can lift the blank holder (7) to move up and down, the hot press and the hot stretching die are heated to 600°C to 800°C, the hot stretching die is opened, the blank holder (7) is moved upward to be flush with the top surface of the punch (6), the blank is placed on the blank holder (7), the outer end face of the blank is aligned with the support plate, the part is pressed after preheating, the temperature is lowered after holding the pressure, and the part is taken out when the temperature drops to 200°C to 400°C and placed on a cooling pad for natural cooling.

7. The forming method of a titanium alloy thin-walled cylindrical part with an angled centerline according to claim 4, characterized in that: In step 4, thermal expansion is performed on a hot press, the hot expansion forming mold is installed on the hot press workbench, the hot press and the hot expansion forming mold are heated to 600°C to 800°C, the hot expansion is started, and the pressure is maintained for a period of time before cooling; when the temperature drops to 200°C to 400°C, the part is taken out and placed on a cooling pad to cool naturally.

8. The forming method of a titanium alloy thin-walled cylindrical part with an angled centerline according to claim 4, characterized in that: In the step 1, before hot stretching, a Ti protective coating and a lubricating coating are sequentially applied to the surface of the blank and the hot stretching die; In the step 4, before the hot expansion forming, the Ti protective coating and the lubricating coating are sequentially applied to the hot expansion blank (4) and the surface of the hot expansion forming die.

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