Thermal forming process method for titanium alloy thin-wall cylindrical part

Abstract

The invention relates to a thermal forming process method for a titanium alloy thin-wall cylindrical part, which comprises the following steps of: calculating the unfolded boundary dimension of the titanium alloy thin-wall cylindrical part, and preparing a flat plate material according to the unfolded boundary dimension; pre-forming the flat plate material, and welding the flat plate material into a cylindrical pre-formed part; loading the cylindrical preform into a hot forming die; the mold containing the cylindrical preformed part is put into a furnace to be subjected to hot forming treatment; and demolding and taking the part to obtain the titanium alloy thin-wall cylindrical part.

Description

Technical Field

[0001] The invention belongs to the field of titanium alloy hot forming processing and relates to a hot forming process method for a titanium alloy thin-walled cylindrical part. Background Art

[0002] At present, aerospace product parts are developing towards higher precision products, higher efficiency, lower cost and larger batches. Titanium alloys are widely used due to their excellent characteristics compared with other materials such as light weight, high thermal strength and good corrosion resistance.

[0003] There are two main manufacturing methods for titanium alloy thin-walled cylindrical parts: one is to use thick-walled sheet metal machining to achieve the hood surface forming, but this process method has a long processing cycle, extremely low production efficiency, and low material utilization, resulting in very expensive production costs and cannot meet quantitative production. The second is to use mold hot spinning to process thin plates. The hot spinning mold processing cost is high, the high-strength titanium alloy has a small elastic modulus, the material has a large rebound after forming, and the size is inconsistent after forming, resulting in a low production qualification rate for annular hood parts. In addition, in order to meet the size requirements, repetitive operations are required, resulting in long processing time, high labor intensity, and low production efficiency. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a titanium alloy thin-walled cylindrical parts manufacturing process method, through the overall process, to design a hot forming mold, so as to solve the existing forming methods (such as thick-walled sheet metal machining, hot spinning processing of thin plates) of high cost, low production efficiency, low pass rate and other problems.

[0005] The solution to the technical problem of the present invention is: a hot forming process method for titanium alloy thin-walled cylindrical parts, the method comprising the following steps:

[0006] Calculate the unfolded dimensions of titanium alloy thin-walled cylindrical parts and prepare flat sheets according to the unfolded dimensions;

[0007] The flat sheet is preformed and welded into a cylindrical preform;

[0008] loading the cylindrical preform into a thermoforming mold;

[0009] The mold containing the cylindrical preform is placed in a furnace for thermoforming treatment;

[0010] The mold is removed to obtain a titanium alloy thin-walled cylindrical part.

[0011] Preferably, the thermoforming mold comprises a mold core, a base, a connecting rod, a pressing plate and N mold halves, where N is greater than or equal to 3;

[0012] The connecting rod is a columnar rod-shaped structure; the bottom plate is provided with a central through hole for inserting and fixing one end of the connecting rod, and the other end of the connecting rod is used to be fixedly connected to the pressing plate; the mold core is a hollow cylindrical structure with a positive cone on the outside, the large end is fixedly mounted on the bottom plate, and the hollow part is used to pass the connecting rod;

[0013] The mold halves are hollow cylindrical structures with inverted cones inside, which are cut into equal parts along the axial direction. There is no connection between the N mold halves. After assembly, the inner cone surface formed by the N mold halves fits with the outer cone surface of the mold core, so that the outer surface formed by the N mold halves reaches the theoretical size of the cylindrical part, and interacts and associates with the cylindrical preform, thereby realizing the hot forming of the cylindrical part.

[0014] Preferably, the molding process is:

[0015] Insert one end of the connecting rod vertically into the center through hole of the bottom plate and insert it with a stop pin;

[0016] Lift the mold core, lower it from just above the connecting rod, and insert it onto the connecting rod until the mold core contacts the chassis;

[0017] The cylindrical preform is hoisted and lowered from directly above the mold core until the cylindrical preform is at a certain height from the bottom of the mold core;

[0018] Place the small end of the mold halves downwards, insert the mold halves into the gap between the cylinder and the mold core, and adjust the gap between the mold halves to be uniform;

[0019] The pressing plate, the base and the connecting rod are fixedly connected, and the relative positions of the mold core and the mold halves are locked, so that the outer surface formed by splicing N mold halves together reaches the theoretical size of the cylindrical part.

[0020] Preferably, the certain height is greater than or equal to 30 mm.

[0021] Preferably, the taper angles of the mold halves and the mold core are in the range of 1° to 3°.

[0022] Preferably, the mold halves and the mold core are made of stainless steel or medium silicon molybdenum material.

[0023] Preferably, the length and width of the flat sheet have margins relative to the length and width of the unfolded piece.

[0024] Preferably, the holding temperature of the hot forming is 650° C. and the holding time is 2 hours.

[0025] Preferably, the demoulding process is: removing the pressing plate and the mold halves in sequence, and then removing the titanium alloy thin-walled cylindrical part.

[0026] Preferably, a cylindrical weld bead avoidance groove is provided on the outer surface of one of the mold halves.

[0027] The beneficial effects of the present invention compared with the prior art are:

[0028] (1) The present invention adopts a split-type hot forming mold for processing and forming, which eliminates the impact of the material's own springback, effectively guarantees the overall size requirements of the parts, and is easy to promote mass production.

[0029] (2) The thermoforming mold of the present invention adopts a split-petal form, and the mold making efficiency is high when the height of the cylindrical part is too high. Compared with the conventional processing method, the present invention can significantly improve the qualified rate of parts, reduce costs, shorten the processing cycle, and improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the installation of the connecting rod according to the embodiment of the present invention.

[0031] Figure 2 It is a schematic structural diagram of a base according to an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of the structure after the mold is installed in an embodiment of the present invention;

[0033] Figure 4 It is a schematic structural diagram of a mold core according to an embodiment of the present invention.

[0034] Figure 5 It is a schematic structural diagram of the mold half according to an embodiment of the present invention.

[0035] Figure 6 It is a cross-sectional schematic diagram of a mold core according to an embodiment of the present invention.

[0036] Figure 7 It is a cross-sectional schematic diagram of a mold half according to an embodiment of the present invention.

[0037] Figure 8 Schematic diagram of a sheet metal part according to an embodiment of the present invention.

[0038] Fig. 9 Schematic diagram of a cylindrical preform according to an embodiment of the present invention.

[0039] Fig.10 This is a schematic diagram of a thermoformed part according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the embodiments.

[0041] In order to meet the production quality requirements of titanium alloy thin-walled cylindrical parts, improve the production efficiency of parts, and reduce processing costs, the present invention proposes a titanium alloy thin-walled cylindrical parts manufacturing process method, which includes the following steps:

[0042] S1. Calculate the unfolded dimensions of titanium alloy thin-walled cylindrical parts and prepare flat sheet materials according to the unfolded dimensions; Figure 8 shown.

[0043] S2, preforming the flat sheet and welding it into a cylindrical preform; Fig. 9 shown.

[0044] S3, loading the cylindrical preform into a thermoforming mold;

[0045] S4, placing the mold containing the cylindrical preform into a furnace for hot forming treatment;

[0046] S5, demoulding and taking out the part, and obtaining a titanium alloy thin-walled cylindrical part. Fig.10 shown.

[0047] like Figure 1 to Figure 7 As shown, in a specific embodiment of the present invention, the thermoforming mold includes a mold core, a base, a connecting rod, a pressing plate and N mold halves, where N is greater than or equal to 3;

[0048] The connecting rod is a columnar rod-shaped structure; the bottom plate is provided with a central through hole for inserting and fixing one end of the connecting rod, and the other end of the connecting rod is used to be fixedly connected to the pressing plate; the mold core is a hollow cylindrical structure with a positive cone on the outside, the large end is fixedly mounted on the bottom plate, and the hollow part is used to pass the connecting rod;

[0049] The mold halves are hollow cylindrical structures with inverted cones inside, which are cut into equal parts along the axial direction. There is no connection between the N mold halves. After assembly, the inner cone surface formed by the N mold halves fits with the outer cone surface of the mold core, so that the outer surface formed by the N mold halves reaches the theoretical size of the cylindrical part, and interacts and associates with the cylindrical preform, thereby realizing the hot forming of the cylindrical part.

[0050] like Figure 2 As shown, the pressing plate is provided with connection holes, hoisting holes and weight-reducing holes. The connection holes are used to connect with the top of the connecting rod, and the hoisting holes are used to connect with the hoisting parts on the furnace top. The weight-reducing holes are used to reduce the weight of the pressing plate.

[0051] like Figure 4 and Figure 6 As shown, the small end of the mold core is provided with a cutout along the axial direction, and a lifting rod is provided between the cutouts; a first lifting hole is provided around the central through hole of the base plate, and a second lifting hole corresponding to the position of the first lifting hole on the base plate is provided at the bottom of the large end of the mold core, which is used to be aligned with the first lifting hole and connected through a long screw.

[0052] Based on the above mold, the mold installation process is:

[0053] Insert one end of the connecting rod vertically into the center through hole of the bottom plate and insert it with a stop pin;

[0054] Lift the mold core, lower it from just above the connecting rod, and insert it onto the connecting rod until the mold core contacts the chassis;

[0055] The cylindrical preform is hoisted and lowered from just above the mold core until the cylindrical preform is at a certain height from the bottom of the mold core; the certain height is greater than or equal to 30 mm.

[0056] Place the small end of the mold halves downwards, insert the mold halves into the gap between the cylinder and the mold core, and adjust the gap between the mold halves to be uniform;

[0057] The pressing plate, the base and the connecting rod are fixedly connected, and the relative positions of the mold core and the mold halves are locked, so that the outer surface formed by splicing N mold halves together reaches the theoretical size of the cylindrical part.

[0058] The demoulding process is: remove the pressing plate, the mold flap in sequence, and then remove the titanium alloy thin-walled cylindrical part.

[0059] The size of the mold halves and core and the range of taper angles are determined by the following method:

[0060] First, determine the friction angle of the mold based on the friction coefficient of the selected mold material, and then determine the range of the taper angle of the mold flap and the mold core to prevent the mold flap from moving from top to bottom on the mold core and being in a state of not self-locking. This taper angle is generally 1° to 3°. Then determine the thickness of the large end of the mold flap based on the mold outer diameter. The thickness of the large end and the taper angle can determine the thickness of the small end. The mold core is an inverted cone that matches the mold flap, and the size can also be determined. (For example, if the mold outer diameter is 200mm, the large end thickness is 30mm, the mold flap height is 665mm, the taper angle is 1.3°, and the small end is 20mm)

[0061] Example:

[0062] This example provides a manufacturing process for a titanium alloy thin-walled cylindrical part. The part is made of TC4 titanium alloy, with a diameter of Φ160mm*450mm and a thickness of 1.2mm. The specific steps are as follows:

[0063] like Figure 3 As shown, the outer dimensions of the unfolded part are calculated according to the outer dimensions of the pre-formed process part of the cylindrical part, and the flat plate material is cut according to the outer dimensions of the unfolded material. The length and width of the outer dimensions of the flat plate material have margins relative to the length and width of the unfolded part.

[0064] The length and width of the flat plate. The length is the expansion in the circumferential direction. The formula for calculating the length of the expanded blank size of the cylinder is as follows:

[0065] Lz=2·π·ρ+η

[0066] Where:

[0067] ρ is the radius of the neutral layer (mm);

[0068] Lz is the unfolded length (mm);

[0069] η is the actual welding shrinkage (mm).

[0070] Constrained by the gap between the inner diameter of the cylinder before hot forming and the mold, if the gap is too small, it will be difficult to assemble the mold halves. If the gap is too large, the hot forming effect will be affected.

[0071] After the flat sheet is preformed and welded into a cylindrical part, it enters the stage of assembling the hot forming mold. The mold halves are first inserted into the cylindrical part, then into the mold core. After the relative position is determined, it is fixed by the pressing plate, connecting rod, and base, waiting to be formed.

[0072] The parts are hot-formed. The furnace is heated to 650°C, and the mold is placed in the furnace to ensure that the parts are evenly heated in the furnace. The insulation temperature is set to 650°C and the time is 2 hours.

[0073] Demolding and taking out the parts. The present invention uses a pressing plate and a bottom plate to fix the relative positions of the mold core and the mold flaps. After cooling, the pressing plate and the mold flaps are removed, and the cylindrical part can be taken out.

[0074] By using the titanium alloy thin-walled cylindrical parts manufacturing process provided by the present invention, the part forming qualification rate is increased by 30%. In addition, compared with the existing mechanical processing method, the material utilization rate is increased by 50%, the manufacturing cost is reduced by 50%, and the processing efficiency is increased by 30%.

[0075] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A hot forming process for titanium alloy thin-walled cylindrical parts, characterized in that The steps include: Calculate the unfolded dimensions of titanium alloy thin-walled cylindrical parts and prepare flat sheets according to the unfolded dimensions; The flat sheet is preformed and welded into a cylindrical preform; loading the cylindrical preform into a thermoforming mold; The mold containing the cylindrical preform is placed in a furnace for thermoforming treatment; The mold is removed to obtain a titanium alloy thin-walled cylindrical part.

2. A hot forming process for titanium alloy thin-walled cylindrical parts according to claim 1, characterized in that: The thermoforming mold comprises a mold core, a base, a connecting rod, a pressing plate and N mold halves, where N is greater than or equal to 3; The connecting rod is a columnar rod-shaped structure; the bottom plate is provided with a central through hole for inserting and fixing one end of the connecting rod, and the other end of the connecting rod is used to be fixedly connected to the pressing plate; the mold core is a hollow cylindrical structure with a positive cone on the outside, the large end is fixedly mounted on the bottom plate, and the hollow part is used to pass the connecting rod; The mold halves are hollow cylindrical structures with inverted cones inside, which are cut into equal parts along the axial direction. There is no connection between the N mold halves. After assembly, the inner cone surface formed by the N mold halves fits with the outer cone surface of the mold core, so that the outer surface formed by the N mold halves reaches the theoretical size of the cylindrical part, and interacts and associates with the cylindrical preform, thereby realizing the hot forming of the cylindrical part.

3. The hot forming process of a titanium alloy thin-walled cylindrical part according to claim 1, characterized in that: The molding process is as follows: Insert one end of the connecting rod vertically into the center through hole of the bottom plate and insert it with a stop pin; Lift the mold core, lower it from just above the connecting rod, and insert it onto the connecting rod until the mold core contacts the chassis; The cylindrical preform is hoisted and lowered from directly above the mold core until the cylindrical preform is at a certain height from the bottom of the mold core; Place the small end of the mold halves downwards, insert the mold halves into the gap between the cylinder and the mold core, and adjust the gap between the mold halves to be uniform; The pressing plate, the base and the connecting rod are fixedly connected, and the relative positions of the mold core and the mold halves are locked, so that the outer surface formed by splicing N mold halves together reaches the theoretical size of the cylindrical part.

4. A hot forming process for titanium alloy thin-walled cylindrical parts according to claim 3, characterized in that: The certain height is greater than or equal to 30 mm.

5. The hot forming process of a titanium alloy thin-walled cylindrical part according to claim 3 is characterized in that: The taper angles of the mold halves and the mold core are in the range of 1° to 3°.

6. The hot forming process of a titanium alloy thin-walled cylindrical part according to claim 3 is characterized in that: The mold halves and the mold core are made of stainless steel or medium silicon molybdenum.

7. The hot forming process of a titanium alloy thin-walled cylindrical part according to claim 1, characterized in that: The length and width of the outer dimensions of the flat plate have margins relative to the length and width of the unfolded piece.

8. The hot forming process of titanium alloy thin-walled cylindrical parts according to claim 1 is characterized in that: The holding temperature of the hot forming is 650°C and the holding time is 2 hours.

9. The hot forming process of titanium alloy thin-walled cylindrical parts according to claim 1, characterized in that: The demoulding process is: remove the pressing plate, the mold flap in sequence, and then remove the titanium alloy thin-walled cylindrical part.

10. The hot forming process of titanium alloy thin-walled cylindrical parts according to claim 1, characterized in that: The outer surface of one of the mold halves is provided with a cylindrical weld bead avoidance groove.

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