Electric energy field auxiliary forming method for difficult-to-deform alloy complex thin-wall component

Abstract

The invention discloses an electric energy field auxiliary forming method for a difficult-to-deform alloy complex thin-wall component. A difficult-to-deform alloy plate and a lower die are clamped; the first-class tool head locally applies pressure to a suspended area, close to the lower die by a preset distance, of the plate, so that the plate is elastically deformed, an elastic deformation area with a concave curved surface is formed, and the elastic deformation area is partially attached to the lower die; the second type of tool head is used for conducting electric auxiliary stress relaxation on the part, attached to the lower die, of the elastic deformation area of the plate, so that the temperature of the plate is rapidly increased, and elastic deformation is converted into plastic deformation; and the first type of tool head and the second type of tool head move according to a preset machining track to progressively machine and form the plate, and the complex thin-wall component is obtained. By means of the progressive electric auxiliary stress relaxation machining method, electric auxiliary stress relaxation is carried out on the area which generates elastic deformation and is elastically attached to the lower die, elastic deformation is converted into plastic deformation, the acting pressure of a tool head in the machining process is very small, the influence on the thickness of a plate is small, and the wall thickness reduction rate can be greatly reduced.

Description

Technical Field

[0001] The invention relates to forming processing of difficult-to-deform alloys, and in particular to an electric energy field assisted forming method of complex thin-walled components of difficult-to-deform alloys. Background Art

[0002] Incremental forming has a short development cycle, low cost, flexible process and strong adaptability, and has received widespread attention. In the existing technology, such as "Incremental Forming Method for Complex Sheet Metal Parts", it is proposed that the use of incremental forming positive forming method can form sheet metal parts with complex shapes, and the production of small batches of complex parts can save time and money. Through experiments, a high-quality human face can be successfully processed.

[0003] However, in the process of incremental forming, the material in the forming area flows in the axial direction under the effect of the forming force of the tool head, resulting in serious thinning of the sheet metal thickness and uneven thickness distribution. The existing technology has studied the problem of uneven thickness distribution of the sheet metal. For example, "Numerical simulation and experimental study of multi-pass double-point incremental forming" proposed to use multiple forming passes and variable interval angles for double-point incremental forming, which can improve the uniformity of the wall thickness distribution of the incremental formed parts, and the effect becomes more obvious as the number of forming passes increases, but the problem of excessive wall thickness thinning still exists. Another example is "Multi-pass incremental forming of TB8 titanium alloy straight-walled square box" proposed to use a method of alternating up and down reciprocating forming trajectory to overcome the serious problem of thickness thinning in the traditional incremental forming path. Experimental research shows that the traditional incremental forming method will cause the maximum wall thickness thinning rate to reach 65.6%, and the improved processing method can reduce the maximum wall thickness thinning rate to 42.6%. Excessive thinning of the formed part has a great influence on the strength. Although the above methods and research have played a certain role in improving the thickness distribution of incremental forming, the problem of excessive wall thickness thinning has not been well solved. Summary of the invention

[0004] Purpose of the invention: In view of the above shortcomings, the present invention provides an electric energy field assisted forming method for complex thin-walled components of difficult-to-deform alloys, which can solve the problems of severe thinning of the wall thickness and uneven thickness distribution of the formed parts.

[0005] Technical solution: To solve the above problems, the present invention adopts an electric field assisted forming method for complex thin-walled components of difficult-to-deform alloys, comprising the following steps:

[0006] Step 1: Clamp the sheet of the hard-to-deform alloy with the lower die;

[0007] Step 2: The first type of tool head applies local pressure to the suspended area of ​​the sheet metal at a preset distance from the lower die, so that the sheet metal undergoes elastic deformation to form an elastic deformation area with a concave curved surface, and the elastic deformation area partially fits the lower die;

[0008] Step 3: The second type of tool head performs electrical assisted stress relaxation on the part of the sheet metal's elastic deformation zone that fits the lower die, so that the sheet metal is quickly heated up and the elastic deformation is converted into plastic deformation;

[0009] Step 4: The first type of tool head and the second type of tool head move according to the preset processing trajectory to complete the first pass of preliminary forming of the sheet;

[0010] Step 5: Change the feed rate of the first type of tool head and the second type of tool head, repeat steps 2 to 4 on the unformed part of the sheet metal, perform progressive processing and forming, and obtain a complex thin-walled component.

[0011] Furthermore, in step 2, a plurality of first-type tool heads simultaneously apply pressure to the sheet locally, so that the concave curved surface forming the elastic deformation zone has different shapes to adapt to the lower model surface.

[0012] Furthermore, when the sheet material is not easily deformed or the elastic deformation is too small, the first type of tool head can be powered on in step 2 to soften the sheet material, perform low-temperature heating on a part of the sheet material, and apply pressure.

[0013] Furthermore, the first type of tool head heats the sheet locally at low temperature, so that the maximum temperature reached locally is no higher than 0.25T. m , where T m is the melting point temperature of the sheet material.

[0014] Furthermore, the maximum temperature of the sheet material is in the range of 0.4 to 0.5 °C. m .

[0015] Furthermore, the first type of tool head, sheet material, mold, temperature control unit and first power supply form a first circuit loop, and the second type of tool head, sheet material, mold, temperature control unit and second power supply form a second circuit loop.

[0016] Furthermore, in step 2 and step 3, the temperature of the sheet material is obtained by an infrared thermal imager, and the output current density of the first power supply and the second power supply is controlled according to the obtained temperature, thereby controlling the temperature of the deformation area on the sheet material.

[0017] Furthermore, the pressure applied by the first type of tool head to the sheet material is calculated through the stress-strain curve at the processing temperature or obtained through finite element simulation; the position at which the first type of tool head applies pressure to the sheet material is determined through simulation calculation, and the fit between the deformation area and the mold is selected to optimize the two; the heating temperature and pressure of the sheet material by the second type of tool head are selected through the stress relaxation curve of the sheet material, so that the stress relaxation rate and the pressure of the second type of tool head are the optimal solutions.

[0018] Furthermore, the processing position of the second type of tool head is 2-3mm away from the edge of the elastic deformation zone. The second type of tool head is electrically heated in the elastic deformation zone of the sheet and at the joint with the mold, so that high-temperature stress relaxation occurs in the area, thereby accelerating the transformation of the elastic deformation in the area into plastic permanent deformation. The current density and current size of the second type of tool head are optimally determined by the temperature corresponding to the selected stress relaxation curve. By controlling the current density and current size of the second type of tool head, the processing temperature of the deformation area is controlled. The moving speed of the two types of tool heads should be slow to ensure that there is enough time for optimal plastic deformation.

[0019] Beneficial effect: Compared with the prior art, the significant advantage of the present invention is that the process of progressive electric-assisted hot forming is used to convert elastic deformation into plastic deformation by causing high-temperature stress relaxation of the material in the area where elastic deformation occurs. The radial force is small. Compared with the traditional progressive forming process, the tool head forming force directly forms the sheet into plastic forming. During the elastic deformation process, the wall thickness of the material is almost not reduced. The elastic deformation area that is almost not thinned is converted into plastic deformation through electric-assisted stress relaxation. The stress relaxation process only converts elastic deformation into plastic deformation, and generally no additional thinning occurs. Therefore, it can effectively improve excessive wall thickness thinning. When pressure is applied, only elastic deformation of the sheet is caused, and the probability of scratching the sheet is greatly reduced. Using a full-shape or partial support mold can achieve higher forming limits and forming accuracy than single-point progressive forming. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the clamping state of the sheet and the mold in the present invention.

[0021] Figure 2 This is a schematic diagram of the structure of the first type of tool head in the present invention applying pressure to the sheet material and rebounding after unloading.

[0022] Figure 3 This is an axonometric diagram of the elastic deformation of the sheet material under pressure in the present invention.

[0023] Figure 4 It is a schematic diagram of the square cone mold in the present invention.

[0024] Figure 5 This is a schematic diagram of the operation of multiple first-type tool heads in the present invention.

[0025] Figure 6 This is a schematic diagram of the system structure of the first / second type tool head for sheet metal forming processing in the present invention.

[0026] Figure 7 It is a schematic diagram of temperature distribution in the deformation area of ​​the sheet in the present invention.

[0027] Figure 8 It is a schematic diagram of the progressive processing and forming process in the present invention.

[0028] Fig. 9 It is a schematic diagram of the structure of the sheet material after shaping in the present invention.

[0029] Fig.10 It is a structural schematic diagram of the clamping state of the sheet and the mold in the second embodiment of the present invention.

[0030] Fig.11 It is a structural schematic diagram of the first type of tool head in the present invention applying pressure to the sheet material of the second embodiment and rebounding after unloading.

[0031] Fig.12 It is a schematic diagram of the system structure of the first / second type tool head in the present invention for sheet metal forming processing of the second embodiment.

[0032] Fig.13 It is a schematic diagram of the structure after a certain forming step in the progressive forming process of the second embodiment of the present invention.

[0033] Fig.14 It is a partial enlarged schematic diagram of the second embodiment of the present invention after the sheet material is shaped.

[0034] Fig.15 It is a schematic diagram of the overall structure of the sheet material after shaping in the second embodiment of the present invention.

[0035] Fig.16 It is the stress relaxation curve of TC4 titanium alloy at different temperatures in the present invention.

[0036] Fig.17 TC4 titanium alloy stress-strain curves at different temperatures. DETAILED DESCRIPTION

[0037] Example 1

[0038] In this embodiment, an electric energy field assisted forming method for a complex thin-walled component of a difficult-to-deform alloy is used. Taking TC4 titanium alloy as an example, the thickness is 1.5 mm. The sheet material 4 is processed into a formed part through multiple processes using a tool head. During the forming process, the sheet material is locally heated by electric assistance. The specific steps are:

[0039] Step 1: If Figure 1 As shown, the flat sheet material 4 is suspended and clamped in the air, and is kept pressed against the lower mold 3 by a clamping device 5 .

[0040] Step 2: If Figures 2 to 5 As shown, the first type of tool head 1 (pressure tool head) applies pressure to the sheet material 4 locally, causing the sheet material 4 to produce elastic deformation. For some high-strength alloy sheets that are difficult to deform, in order to reduce the load of the first type of tool head pressing down to produce elastic deformation, low-temperature electric heating can also be performed. Fig.17The stress-strain curves of TC4 titanium alloy at different temperatures are shown. The pressure and pressure point position of the first type tool head 1 are set. In this embodiment, the pressure is 300N. The sheet 4 elastically deforms to form an elastic deformation zone. The elastic deformation zone partially fits the mold 3. The position where the first type tool head 1 applies pressure is 22mm away from the mold 3 and the sheet 4. Figure 5 As shown, by using a plurality of first-type tool heads 1 to apply local pressure to the sheet material 4 at the same time, elastic deformation areas of different shapes will be presented to adapt to the lower model surface, thereby accelerating the forming speed and improving the forming accuracy.

[0041] Step 3: If Figure 6 and Figure 7 As shown, the second type of tool head 2 (electric tool head) discharges the part of the sheet 4 elastic deformation area that fits the mold to perform electric auxiliary heating. Fig.16 The stress relaxation curve of TC4 titanium alloy at different temperatures is shown. The moving speed and pressure of the second type tool head 2 are set. In this embodiment, the stress relaxation curve at 720°C is selected, and the X, Y and Z axial feed speeds are set to 200-3000 mm / min. The tool head 1 moves along the X and Y axis circular trajectory with a radius range of 0-20 mm. The first type tool head 1 is set 20 mm outside the second type tool head 2 and is kept 22 mm horizontally away from the edge of the mold. The temperature is controlled to rise to 720°C (about 0.43T) in a very short time. m ), forming a high temperature zone; in the high temperature zone, the sheet material 4 undergoes high temperature stress relaxation, and the elastic deformation is converted into plastic deformation, from recoverable deformation to permanent deformation.

[0042] Step 4: Figures 6 to 8 As shown, the temperature control device 6 includes a host computer, a temperature control unit, and an infrared thermal imager. The initial temperature is set in the host computer, and the first type of tool head 1 and the second type of tool head 2 move according to a preset trajectory. During the movement, in order to control the temperature of the bonding surface between the sheet material 4 and the mold 3 to maintain a high stress relaxation temperature, an infrared thermal imager is required to monitor in real time, and the temperature control unit is used to control the output current density of the power supply 7 to control the temperature of the sheet material. At the same time, the first type of tool head 1 and the second type of tool head 2 should be kept moving synchronously to complete the first preliminary forming of the sheet material.

[0043] Step 5: Change the feed rate of the first type tool head 1 and the second type tool head 2, repeat steps 2 to 4 for the unformed part of the sheet, and complete the processing and forming of the sheet through multiple passes to obtain a complex thin-walled component, such as Fig. 9 As shown, the sheet material 4 is formed, the first type tool head 1 and the second type tool head 2 stop moving, and the power is turned off. The sheet material is formed into a truncated cone with a taper of 30°, a height of 20mm, and a top diameter of 30mm.

[0044] Example 2

[0045] In this embodiment, an electric energy field assisted forming method for a complex thin-walled component of a difficult-to-deform alloy is used. Taking TC4 titanium alloy as an example, the thickness is 1.5 mm. The tool head is used to process the conical sheet 11 into a formed part through multiple processes. During the forming process, the sheet is locally heated by electric assistance. The specific steps are:

[0046] Step 1: Fig.10 As shown, the conical sheet material 11 is suspended and clamped in the air, and is kept pressed against the second mold 10 by a second clamping device 12 .

[0047] Step 2: If Fig.11 and Fig.12 As shown, the first type of tool head 1 (pressure tool head) applies pressure locally to the conical sheet material 11, causing the conical sheet material 11 to produce elastic deformation. Fig.17 The stress-strain curves of TC4 titanium alloy at different temperatures are shown, and the pressure size and pressure point position of the first type of tool head 1 are set. In this embodiment, the pressure size is 300N, and the conical sheet 11 elastically deforms to form an elastic deformation zone. The elastic deformation zone partially fits the second mold 10, and the position where the first type of tool head 1 applies pressure is 14mm away from the fitting point between the second mold 10 and the sheet 4.

[0048] Step 3: If Fig.13 As shown, the second type of tool head 2 (electric tool head) discharges the part of the elastic deformation area of ​​the conical sheet 11 that fits the mold to perform electrical auxiliary heating. Fig.16 The stress relaxation curve of TC4 titanium alloy at different temperatures is shown. The moving speed and pressure of the second type tool head 2 are set. In this embodiment, the stress relaxation curve at 720°C is selected, and the X, Y and Z axial feed speeds are set to 200-3000 mm / min, and the tool head 1 moves along the X and Y axis circular trajectory. The first type tool head 1 is set at a horizontal distance of 14 mm from the edge of the mold. The temperature is controlled to rise to 720°C (about 0.43T) in a very short time. m ), forming a high temperature zone; in the high temperature zone, high temperature stress relaxation occurs in the conical sheet 11, and elastic deformation is converted into plastic deformation, from recoverable deformation to permanent deformation.

[0049] Step 4: Figures 14 to 16As shown, the initial temperature is set in the host computer, and the first type of tool head 1 and the second type of tool head 2 move according to the preset trajectory. During the movement, in order to control the temperature of the fitting surface of the conical sheet 11 and the second mold 10 to maintain a high stress relaxation temperature, an infrared thermal imager is required to monitor in real time, and the temperature control unit is used to control the power supply output current density, thereby controlling the sheet temperature. At the same time, the first type of tool head 1 and the second type of tool head 2 should be kept moving synchronously to complete the first preliminary forming of the conical sheet 11.

[0050] Step 5: Change the feed rate of the first type tool head 1 and the second type tool head 2, repeat steps 2 to 4 for the unprocessed part of the tapered sheet 11, and complete the processing and forming of the sheet through multiple passes to obtain a complex thin-walled component, such as Fig.17 As shown, the conical sheet 11 is formed, the first type tool head 1 and the second type tool head 2 stop moving, and the power is turned off. The sheet is formed into a corrugated disk with a taper of 30°, a height of 15mm, and a top diameter of 200mm.

Claims

1. An electric energy field assisted forming method for complex thin-walled components of difficult-to-deform alloys, characterized in that: The following steps are involved: Step 1: Clamp the sheet of the hard-to-deform alloy with the lower die; Step 2: The first type of tool head applies local pressure to the suspended area of ​​the sheet metal at a preset distance from the lower die, so that the sheet metal undergoes elastic deformation to form an elastic deformation area with a concave curved surface, and the elastic deformation area partially fits the lower die; Step 3: The second type of tool head performs electrical assisted stress relaxation on the part of the sheet metal's elastic deformation zone that fits the lower die, so that the sheet metal is quickly heated up and the elastic deformation is converted into plastic deformation; Step 4: The first type of tool head and the second type of tool head move according to the preset processing trajectory to complete the first pass of preliminary forming of the sheet; Step 5: Change the feed rate of the first type of tool head and the second type of tool head, repeat steps 2 to 4 on the unformed part of the sheet metal, perform progressive processing and forming, and obtain a complex thin-walled component.

2. The electric energy field assisted forming method according to claim 1, characterized in that: In step 2, a plurality of first-type tool heads simultaneously apply pressure to the sheet material locally, so that the concave curved surface forming the elastic deformation zone has different shapes to adapt to the lower model surface.

3. The electric energy field assisted forming method according to claim 2, characterized in that: In step 2, low-temperature heating is performed on a part of the sheet material by using the first type of tool head and pressure is applied.

4. The electric energy field assisted forming method according to claim 3, characterized in that: The first type of tool head heats the plate locally at low temperature, so that the maximum temperature reached locally is no higher than 0.25T. m , where T m is the melting point temperature of the sheet material.

5. The electric energy field assisted forming method according to claim 4, characterized in that: The maximum temperature range reached by the sheet material is 0.4~0.5T m .

6. The electric energy field assisted forming method according to claim 5, characterized in that: The first type of tool head, sheet material, mold, temperature control unit and first power supply form a first circuit loop, and the second type of tool head, sheet material, mold, temperature control unit and second power supply form a second circuit loop.

7. The electric energy field assisted forming method according to claim 6, characterized in that: In step 2 and step 3, the temperature of the sheet material is obtained by an infrared thermal imager, and the output current density of the first power supply and the second power supply is controlled according to the obtained temperature, thereby controlling the temperature of the deformation area on the sheet material.

8. The electric energy field assisted forming method according to claim 7, characterized in that: The pressure applied by the first type of tool head to the sheet material is calculated by a stress-strain curve at a processing temperature or obtained by finite element simulation; the position where the first type of tool head applies pressure to the sheet material is determined by simulation calculation.

9. The electric energy field assisted forming method according to claim 7, characterized in that: The heating temperature and pressure of the second type of tool head on the sheet material are selected according to the stress relaxation curve of the sheet material.

10. The electric energy field assisted forming method according to claim 9, characterized in that: The processing position of the second type of tool head is 2-3 mm away from the edge of the elastic deformation zone.

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