Temperature control workbench and application thereof in friction stir additive manufacturing

Abstract

The invention discloses a temperature control workbench and application thereof in friction stir additive manufacturing, the temperature control workbench comprises a bottom plate and a cover plate, the bottom plate and the cover plate are arranged in parallel, the bottom plate is located below the cover plate and fixedly installed with the cover plate, at least one sealed flow channel is formed between the bottom plate and the cover plate, and the flow channel is communicated with the bottom plate. Each flow channel is provided with a liquid inlet and a liquid outlet in the side face of the temperature control workbench, and a cooling medium is introduced into each flow channel. According to the temperature control workbench, the heat dissipation efficiency in the friction stir additive manufacturing process is improved, and the phenomenon that the additive quality is affected due to overheating is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of additive manufacturing, and in particular relates to a temperature-controlled workbench and an application thereof in friction stir additive manufacturing. Background Art

[0002] Friction stir additive manufacturing technology is a solid-phase metal material additive manufacturing method. During the additive manufacturing process, the friction between the material and the workpiece surface generates heat to achieve plastic flow of the material, and the additive manufacturing deposition layer is formed as the spindle moves. The friction stir additive manufacturing process is a typical force-heat interaction process. Changes in the process parameters of friction stir additive manufacturing change the force and temperature of the material, thereby affecting the quality and performance of friction stir additive manufacturing.

[0003] The essence of the friction stir additive manufacturing process is the plastic deformation process of the material caused by friction heat generated under the action of force, and heat generation accompanies the entire process. The friction stir additive manufacturing process involves single-pass multi-layer and multi-pass multi-layer deposition. Excess heat continues to diffuse to the fixture and workbench, and in the long-term friction stir additive manufacturing, this temperature conduction and accumulation phenomenon is more obvious, and the temperature of the workbench can even reach two or three hundred degrees Celsius. Excessive temperature not only easily causes large internal stress and deformation in the workpiece, but also because the workbench temperature is too high, the heat dissipation efficiency of the plasticized material is low, and the additive temperature gradually increases, affecting its fluidity, which is not conducive to the continuity of the friction stir additive manufacturing process and the additive quality. Summary of the invention

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a temperature-controlled workbench.

[0005] Another object of the present invention is to provide an application of the above-mentioned temperature-controlled workbench in friction stir additive manufacturing, which solves the problem of temperature control in the process of friction stir additive manufacturing.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A temperature-controlled workbench comprises: a base plate and a cover plate, wherein the base plate and the cover plate are arranged in parallel, the base plate is located below the cover plate and is fixed to the cover plate, at least one sealed flow channel is formed between the base plate and the cover plate, each flow channel is formed with a liquid inlet and a liquid outlet on the side of the temperature-controlled workbench, and each of the flow channels is used for passing a cooling medium.

[0008] In the above technical solution, the liquid inlet is located on the side of the cover plate.

[0009] In the above technical solution, the liquid outlet is located on the side of the cover plate.

[0010] In the above technical solution, the flow channel is surrounded by a recessed groove formed on the lower surface of the cover plate and the upper surface of the bottom plate.

[0011] In the above technical solution, the number of the flow channels is two.

[0012] In the above technical solution, each of the flow channels includes: a first section and a second section, the first section is a straight line, the second section is a winding curve, one end of the first section is a liquid inlet, the other end of the first section is connected to one end of the second section, and the other end of the second section is a liquid outlet.

[0013] In the above technical solution, the two flow channels are symmetrically arranged.

[0014] In the above technical solution, a first sealing ring is installed between the bottom plate and the cover plate around the flow channel to seal between the bottom plate and the cover plate.

[0015] In the above technical solution, a first mounting groove is formed on the lower surface of the cover plate for mounting the first sealing ring.

[0016] In the above technical solution, the bottom plate and the cover plate are fixed by a plurality of bolts, and a second sealing ring is installed around each bolt between the bottom plate and the cover plate.

[0017] In the above technical solution, a second mounting groove is formed on the lower surface of the cover plate for mounting the second sealing ring.

[0018] In the above technical solution, a plurality of blind holes are formed on the upper surface of the cover plate, and each blind hole is formed with an internal thread for fixing a workpiece manufactured by friction stir additive manufacturing.

[0019] The application of the above-mentioned temperature-controlled workbench in friction stir additive manufacturing.

[0020] In the above technical solution, the temperature-controlled workbench reduces the defects of the deposited layer obtained by stir friction additive manufacturing.

[0021] In the above technical solution, the temperature-controlled workbench improves the mechanical properties of the deposited layer obtained by stir friction additive manufacturing.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. The temperature-controlled workbench of the present invention improves the heat dissipation efficiency during the friction stir additive manufacturing process, avoiding overheating that affects the additive quality. The temperature-controlled workbench achieves the purpose of reducing deposition defects by increasing the cooling rate of the workpiece and improving the deposition stability. The temperature-controlled workbench reduces the heat accumulation during the deposition process, avoids overheating of the deposited layer, and is conducive to improving mechanical properties.

[0024] 2. The change of force signal can directly reflect the characteristics of the stir friction additive manufacturing process. The working temperature of the general force signal sensor is -20°C to 80°C. The temperature control workbench of the present invention can be used to install the force signal sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the temperature control workbench of the present invention (with a three-axis force sensor and a bottom pad installed);

[0026] Figure 2 It is a structural schematic diagram of the cover plate in the temperature control workbench of the present invention;

[0027] Figure 3 is a schematic diagram of the structure of the base plate;

[0028] Figure 4 is a structural schematic diagram of the bottom pad;

[0029] Figure 5 It is the top view of the workpiece (thermocouple distribution position diagram);

[0030] Figure 6 The three-axis force curves obtained by the three-axis force sensor during the friction stir additive manufacturing process;

[0031] Figure 7 is the workpiece temperature variation curve of the second thermocouple;

[0032] Figure 8 This is a photo of the deposited layer (using a temperature-controlled workbench);

[0033] Fig. 9 This is a photo of the deposited layer (without using a temperature-controlled workbench);

[0034] Fig.10 For tensile performance comparison;

[0035] Fig.11 This is the metallographic image of the sedimentary layer;

[0036] Fig.12 This is the metallographic image of the sedimentary layer;

[0037] Fig.13 The three-axis force curves obtained by the three-axis force sensor during the friction stir additive manufacturing process.

[0038] Among them, 1: cover plate, 2: bottom plate, 3: blind hole, 4: first countersunk hole, 5: first bolt countersunk hole, 6: lower pad, 7: three-way force sensor, 8: first thermocouple mounting hole, 9: liquid outlet, 10: liquid inlet, 11: second bolt countersunk hole, 12: second thermocouple mounting hole, 13: first mounting groove, 14: second mounting groove, 15: flow channel. DETAILED DESCRIPTION

[0039] The temperature-controlled workbench of the present invention and its application in friction stir additive manufacturing are described in detail below with reference to the accompanying drawings.

[0040] Example 1

[0041] As attached Figures 1 to 4 As shown, a temperature control workbench comprises: a bottom plate 2 and a cover plate 1, the bottom plate 2 and the cover plate 1 are arranged in parallel, the bottom plate 2 is located below the cover plate 1 and fixed to the cover plate 1, two sealed flow channels 15 are formed between the bottom plate 2 and the cover plate 1, and the two flow channels 15 are symmetrically arranged. Each flow channel 15 is formed with a liquid inlet 10 and a liquid outlet 9 on the side of the temperature control workbench, and the liquid inlet 10 is connected to the water cooler for passing the cooling medium into each flow channel 15.

[0042] In this embodiment, the liquid inlet 10 and the liquid outlet 9 are both located on the side of the cover plate 1. The flow channel 15 is surrounded by a concave groove formed on the lower surface of the cover plate 1 and the upper surface of the bottom plate 2.

[0043] Each flow channel 15 includes: a first section and a second section, the first section is a straight line, the second section is a winding curve, one end of the first section is a liquid inlet 10, the other end of the first section is connected to one end of the second section, and the other end of the second section is a liquid outlet 9.

[0044] A first sealing ring is installed between the bottom plate 2 and the cover plate 1 around the two flow channels 15 for sealing between the bottom plate 2 and the cover plate 1. A first mounting groove 13 is formed on the lower surface of the cover plate 1 for mounting the first sealing ring.

[0045] The bottom plate 2 and the cover plate 1 are fixed by a plurality of bolts, and a second bolt countersunk hole 11 for installing the bolts is formed on the cover plate 1, and a second sealing ring is installed around each bolt between the bottom plate 2 and the cover plate 1. A second mounting groove 14 is formed on the lower surface of the cover plate 1 for installing the second sealing ring.

[0046] A plurality of blind holes 3 are formed on the upper surface of the cover plate 1 , and each blind hole 3 is formed with an internal thread for fixing a workpiece manufactured by friction stir additive manufacturing.

[0047] During the friction stir additive manufacturing process, a water cooler is started to circulate a constant temperature cooling medium into the flow channel to control the temperature.

[0048] Example 2

[0049] In Example 1, a lower pad 6 is arranged below the bottom plate 2 of the temperature control workbench. A first bolt countersunk hole 5 for fixing the lower pad 6 is formed on the lower pad 6. The lower pad 6 and the bottom plate 2 are arranged in parallel. Four three-axis force sensors 7 are arranged between the lower pad 6 and the bottom plate 2. The four three-axis force sensors 7 are arranged in a rectangular array. Each three-axis force sensor 7 is fixed to the lower pad 6, the cover plate 1 and the bottom plate 2 respectively. Figure 2 As shown, a first countersunk hole 4 for installing a three-axis force sensor 7 is formed on the cover plate 1. The four three-axis force sensors 7 are electrically connected to the computer. During the friction stir additive manufacturing process, the three-axis force changes of the temperature-controlled workbench are collected in real time through the four three-axis force sensors 7.

[0050] A first thermocouple mounting hole 8 is provided on the side of the cover plate 1 on one side of each liquid outlet 9 for mounting the first thermocouple. A plurality of second thermocouple mounting holes 12 are provided on the lower surface of the cover plate 1 on one side of the flow channel 15 for mounting the second thermocouple. The first thermocouple is used to monitor the temperature near the liquid outlet 9, and the second thermocouple is used to obtain the temperature near the flow channel 15. The first thermocouple and the second thermocouple are K-type armored thermocouples. The first thermocouple and the second thermocouple monitor temperature changes to prevent long-term friction stir additive manufacturing from causing continuous accumulation and increase of temperature. If the temperature continues to accumulate and increase, on the one hand, it will cause great thermal stress on the workpiece, causing deformation of the workpiece, and on the other hand, excessive temperature will affect the three-axis force sensor.

[0051] Example 3

[0052] A temperature-controlled workbench was used for friction stir additive manufacturing. A 10mm thick 6061-T6 aluminum alloy substrate was fixed on the temperature-controlled workbench as a workpiece. The friction stir additive manufacturing used 6061-T6 consumable rods (cross-section 15*15mm) with the following process parameters: rotation speed 450rpm, travel speed 400mm / min, feed speed 2mm / s, deposition thickness 1.5mm. Single-pass multi-layer friction stir additive manufacturing was performed, and the final deposited layer height was not less than 40mm.

[0053] The second thermocouple includes: thermocouple 1 and thermocouple 2, such as Figure 5 As shown, thermocouple 1 is located at the center of the deposition path, and thermocouple 2 is 5 mm away from the edge of the deposition layer. The temperature change is monitored by a second thermocouple at different positions on the workpiece away from the FAM processing area, and the force signal is collected by the three-axis force sensor 7. The three-axis force curve (force signal) during the FAM process is shown in Figure 6 The corresponding temperature change curve during the friction stir additive manufacturing process is shown in Figure 7 The obtained deposition layer is shown as Figure 8 shown.

[0054] Sedimentary layer along Figure 8 The tensile properties in the vertical direction are as follows Fig.10 The metallographic image of the deposited layer is shown in Fig.12 As shown, there are no defects at the interface of the deposited layers.

[0055] Comparative Example 1

[0056] The friction stir additive manufacturing was carried out under the same conditions as in Example 3, except that a temperature control workbench was not used. The temperature change curve during the friction stir additive manufacturing process is shown in FIG. Figure 7 The resulting deposited layer is shown as Fig. 9 shown.

[0057] Sedimentary layer along Fig. 9 The tensile properties in the vertical direction are as follows Fig.10 The metallographic image of the deposited layer is shown in Fig.11 As shown in the figure, due to the thermal deformation of the plate, the deposition thickness changes, affecting the interface bonding, and defects are observed in many locations. The three-axis force curve (force signal) during the friction stir additive manufacturing process is shown in the figure. Fig.13 As shown in the figure, it can be seen that the curve fluctuates significantly and is unstable.

[0058] Depend on Figure 7 It can be seen that the cooling rate at which the peak temperature drops to 200°C is used to evaluate the heat dissipation conditions. When there is no temperature control workbench, the cooling rate at thermocouple 1 is about 8.7°C / s, and the cooling rate at thermocouple 2 is 6.8°C / s; when there is a temperature control workbench, the cooling rate at thermocouple 1 is about 19.6°C / s, and the cooling rate at thermocouple 2 is 21.8°C / s. The temperature control workbench can improve the heat dissipation efficiency of the workpiece, especially in the long-term stir friction additive manufacturing process, which can significantly reduce the heat accumulation of the workpiece and reduce the thermal stress and deformation of the workpiece.

[0059] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A temperature-controlled workbench, characterized in that: include: The bottom plate and the cover plate are arranged in parallel, the bottom plate is located below the cover plate and fixed to the cover plate, at least one sealed flow channel is formed between the bottom plate and the cover plate, each flow channel is formed with a liquid inlet and a liquid outlet on the side of the temperature control workbench, and each of the flow channels is used to pass a cooling medium.

2. The temperature-controlled workbench according to claim 1, characterized in that: The liquid inlet is located on the side of the cover plate; the liquid outlet is located on the side of the cover plate.

3. The temperature-controlled workbench according to claim 1, characterized in that: The flow channel is surrounded by a concave groove formed on the lower surface of the cover plate and the upper surface of the bottom plate.

4. The temperature-controlled workbench according to claim 1, characterized in that: Each of the flow channels includes: a first section and a second section, the first section is a straight line, the second section is a winding curve, one end of the first section is a liquid inlet, the other end of the first section is connected to one end of the second section, and the other end of the second section is a liquid outlet.

5. The temperature-controlled workbench according to claim 1, characterized in that: A first sealing ring is installed between the bottom plate and the cover plate around the flow channel to seal between the bottom plate and the cover plate.

6. The temperature-controlled workbench according to claim 1, characterized in that: The bottom plate and the cover plate are fixed by a plurality of bolts, and a second sealing ring is installed around each bolt between the bottom plate and the cover plate.

7. The temperature-controlled workbench according to claim 1, characterized in that: A plurality of blind holes are formed on the upper surface of the cover plate, each of which is formed with an internal thread for fixing a workpiece manufactured by friction stir additive manufacturing.

8. Use of the temperature-controlled workbench as claimed in any one of claims 1 to 7 in friction stir additive manufacturing.

9. The use according to claim 8, characterized in that: The temperature-controlled workbench reduces defects in the deposited layer obtained by friction stir additive manufacturing.

10. The use according to claim 8, characterized in that: The temperature-controlled workbench improves the mechanical properties of the deposited layer obtained by friction stir additive manufacturing.

Images