A method and apparatus for monitoring the temperature of a friction stir weld nugget

Abstract

The application discloses a temperature monitoring device and method for a friction stir welding seam core area, wherein a stepped hole is formed on a welding head, a thermocouple metal wire is placed in the hole, and the thermocouple metal wire is filled with a high-temperature-resistant insulating material outside; a temperature measuring point is located on a contact surface of the welding head and a workpiece, the thermocouple metal wire, the welding head and the workpiece are in contact with each other at the temperature measuring point; the welding head can be driven to rotate by a main shaft of a welding machine to realize welding on the workpiece; the thermocouple metal wire and the welding head are made of different materials, a thermoelectric potential signal of the thermocouple metal wire and the welding head is measured during welding, the signal is amplified by a signal processing circuit board on a taper sleeve, and is wirelessly transmitted to an external device, the signal processing circuit board is powered by a battery module in the taper sleeve, and core area temperature monitoring during welding is realized. The application can locate the temperature measuring point on the contact surface of the welding head and the workpiece, and directly contact with welding materials, so that rapid and accurate measurement of the core area temperature of the welding seam during welding can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding equipment manufacturing, and particularly relates to a temperature monitoring method and device for a friction stir welding weld core area. BACKGROUND

[0002] Friction stir welding is a solid-state welding technology, which has the characteristics of high efficiency, good weld performance and environmental protection, and is widely used in the welding fields of aluminum, copper and titanium alloys. Friction stir welding generates heat through the friction between the stirring head and the workpiece. The temperature of the contact surface between the stirring head and the workpiece is the temperature of the weld core area, which is an important factor affecting the quality of the weld.

[0003] The traditional method for measuring the temperature of the weld core area is to embed a thermocouple in the workpiece or the stirring head. The method of embedding a temperature sensor in the workpiece needs to damage the workpiece and cannot be widely applied in engineering practice.

[0004] Therefore, some scholars have carried out related research. The real-time temperature monitoring in the engineering welding process is realized by implanting a thermocouple in the stirring head. The method adopted is to embed a commonly used industrial packaged thermocouple (such as a K-type armored thermocouple) in the stirring head. The internal structure of the K-type armored thermocouple is shown in Figure 1 As can be seen, it includes two thermocouple wires made of different materials. The actual temperature measuring point is located at the junction of the two thermocouple wires, and the thermocouple wires are coated with a temperature-resistant insulation layer and a stainless steel protective layer. Therefore, in the existing scheme, the temperature measuring point of the thermocouple does not actually contact the workpiece material. In the friction stir welding process, the stirring head is in a high-speed rotating state. For the current temperature measurement scheme, the temperature of the weld core area needs to be transmitted through the stainless steel protective layer and the temperature-resistant insulation layer before reaching the actual temperature measuring point. The heat transfer equation in homogeneous materials is a first-order time-delay differential equation. Therefore, the measurement result of the existing temperature measurement scheme will have a lag effect, resulting in poor dynamic performance of the temperature measurement system. When the temperature of the temperature measuring point changes sharply during welding, the temperature measurement accuracy decreases significantly. SUMMARY

[0005] To solve the above problems, the application discloses a temperature monitoring method for a friction stir welding weld core area, which can be realized by

[0006] To achieve the above-mentioned application purposes, the application adopts the following technical scheme:

[0007] The application provides a temperature monitoring device for a friction stir welding weld core area, which comprises:

[0008] a thermocouple wire, a temperature-resistant insulation layer, a stirring head, a workpiece, a welding machine spindle and a signal processing circuit board.

[0009] The material of the thermocouple wire is different from the material of the stirring head;

[0010] The stirring head is driven to rotate by the welding machine spindle to realize internal processing of the workpiece; the thermocouple wire with a temperature-resistant insulating layer is arranged in the stepped hole, and both ends of the thermocouple wire are exposed, wherein the bottom exposed end is flush with the contact surface of the stirring head and the workpiece and is in contact with the workpiece to be welded to form a temperature measuring point; the upper exposed end is connected with the stirring head through a wire to form a conductive loop.

[0011] A signal processing circuit board for collecting the thermoelectric potential E signal of the thermocouple wire and the stirring head away from the temperature measuring point is connected in the conductive loop; and the collected thermoelectric potential E signal is transmitted to an upper computer for storing and presenting data through the signal processing circuit board.

[0012] More preferably, the temperature monitoring device further comprises a welding machine spindle, a cone sleeve, a clamp sleeve, and the stirring head is fixed in the clamp sleeve, the clamp sleeve is connected with the cone sleeve, and the cone sleeve is installed on the welding machine spindle and rotates synchronously with the welding machine spindle.

[0013] More preferably, the signal processing circuit board is fixed on the cone sleeve and is powered by a battery module fixed in the cone sleeve.

[0014] More preferably, the signal processing circuit board comprises:

[0015] The amplifiers, the signal processing module, the control module, and the wireless sending module are connected in series, and power is provided through the power supply module.

[0016] The thermoelectric potential E signal is first amplified by the amplifier, then the thermoelectric potential E signal is converted into a corresponding digital signal by the signal processing module, the digital signal is filtered and processed by the control module, and the signal is transmitted out by the wireless sending module.

[0017] More preferably, the material of the thermocouple wire is nickel-silicon alloy, the material of the stirring head is H13 die steel, and alumina insulating ceramic is used.

[0018] The application also provides a temperature monitoring method for a friction stir welding weld core area, which is realized by using the temperature monitoring device for a friction stir welding weld core area according to any one of claims 1-5, and the temperature monitoring method comprises the following steps:

[0019] Step S101: According to the temperature measuring point position of the workpiece friction surface to be measured, a stepped hole is processed on the stirring head; the small hole section of the stepped hole is close to the temperature detection point position.

[0020] Step S102, select the thermocouple wire into the stepped hole of the stirring head, the bottom of the thermocouple wire exposed end is in contact with the stirring head at the temperature measurement point position, the upper part of the thermocouple wire exposed end is connected with the columnar part of the stirring head through the wire to form a conductive loop, and the signal processing circuit board is connected in the conductive loop; The rest of the thermocouple wire is filled with temperature-resistant insulating material between the stirring head; The thermocouple wire and the stirring head are different in material;

[0021] Step S103, the stirring head is fixed in the jacket, the jacket is connected with the cone sleeve, and the cone sleeve is installed on the welding machine spindle; During the welding process of the workpiece by the stirring head, the bottom of the thermocouple wire is flush with the stirring head and contacts the workpiece at the same time;

[0022] Step S104, during the welding process, the thermoelectric potential difference E between the thermocouple wire and the stirring head is collected by the signal processing circuit board as a temperature monitoring signal; The signal processing circuit board is fixed on the cone sleeve, and the battery module in the cone sleeve supplies power to the circuit; The temperature signal line and the power line are connected with the circuit board through the internal hole of the jacket and the cone sleeve;

[0023] Step S105, the detected thermoelectric potential difference E is transmitted to the external host computer for data storage and presentation by the signal processing circuit board through the amplification circuit and the wireless transmission module.

[0024] Compared with the prior art, the beneficial effects of the present application are:

[0025] 1. The present application utilizes the stirring head and the inserted thermocouple wire to form the positive and negative electrodes of thermoelectric effect, the temperature measurement point is located on the friction surface of the stirring head and the workpiece, and the thermocouple wire is in direct contact with the workpiece material, which can quickly and accurately dynamically monitor the rapid change of the temperature on the friction surface of the stirring head and the workpiece, the monitoring result has better dynamic performance and the test result is more accurate, so that the rapid and accurate measurement of the core area temperature of the welding seam during the welding process can be realized.

[0026] 2. Multiple temperature detection points are arranged at different positions on the stirring head to realize simultaneous measurement of multiple points.

[0027] 3. The signal processing and wireless transmission circuit is designed on the welding machine spindle to realize real-time monitoring of the temperature during the welding process. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is an internal structure schematic diagram of the prior art industrial K type armored thermocouple;

[0029] Figure 2 It is a working principle diagram of a temperature monitoring device for the core area of the welding seam of the friction stir welding of the present application;

[0030] Figure 3The working principle diagram of the signal processing circuit board of the application;

[0031] Figure 4 The working principle diagram of the temperature monitoring device for multi-point temperature measurement of the application;

[0032] Figure 5 The structural principle diagram of the temperature monitoring device for the core area of the friction stir welding seam of the application.

[0033] In the drawings:

[0034] Thermocouple wire 1; temperature-resistant insulation layer 2; stirring head 3; workpiece 4; welding machine spindle 5; cone sleeve 6; battery module 7; signal processing circuit board 8; clamping sleeve 9. DETAILED DESCRIPTION

[0035] In order to better understand the application, the content of the application will be further illustrated below in combination with examples, but the content of the application is not limited to the examples below.

[0036] The application provides a temperature monitoring device for the core area of a friction stir welding seam, as shown in the drawings, which comprises a thermocouple wire 1, a temperature-resistant insulation layer 2, a stirring head 3, a workpiece 4, a welding machine spindle 5, a cone sleeve 6, a battery module 7, a signal processing circuit board 8, and a clamping sleeve 9. Figures 2-5

[0037] The material of the thermocouple wire 1 is different from that of the stirring head 3. The material of the thermocouple wire 1 is nickel-silicon alloy; the material of the stirring head 3 is H13 die steel; the workpiece 4 is a 6061 aluminum alloy workpiece; and the temperature-resistant insulation layer 2 is an alumina insulation ceramic.

[0038] The stirring head 3 is fixed in the clamping sleeve 9, the clamping sleeve 9 is connected with the cone sleeve 6, the cone sleeve 6 is installed on the welding machine spindle 5 and rotates synchronously with the welding machine spindle 5, thereby being able to drive the stirring head 3 to rotate.

[0039] The stirring head 3 comprises a column body and a stirring needle below the column body; the stirring needle is in the shape of a circular truncated cone and can be embedded in a welding groove of the workpiece 4; the maximum outer diameter of the stirring needle is smaller than the diameter of the column body, so that a shoulder is formed at the position where the column body is not connected with the stirring needle; the inside of the stirring head 3 is processed with a stepped hole (i.e., a stepped hole) by electric spark machining;

[0040] ​The thermocouple wire 1 wrapped with the temperature-resistant insulation layer 2 can be inserted into the stepped hole, and the two ends of the thermocouple wire 1 are exposed, wherein the bottom exposed end is flush with and in contact with the shoulder of the stirring head 3 and is in contact with the workpiece 4 to be welded, forming a temperature measuring point; the upper exposed end is connected to the stirring head 3 through a wire, forming an electric conduction loop; the diameter d1 of the thermocouple wire 1 is, for example, 1 mm; the small-diameter hole of the stepped hole can accommodate the bottom exposed end of the temperature-resistant insulation layer 2, and the height of the small-diameter hole is 0.8d1; the large-diameter hole of the stepped hole has a diameter d2 and can accommodate the thermocouple wire 1 wrapped with the temperature-resistant insulation layer 2.

[0041] A signal processing circuit board 8 is connected in the electric conduction loop for measuring the thermoelectric potential E of the thermocouple wire 1 away from the temperature measuring point.

[0042] The signal processing circuit board 8 is fixed on the cone sleeve 6 and is powered by the battery module 7 fixed inside the cone sleeve 6. The working principle of the signal processing circuit board 8 is as shown in Figure 3 , which includes an amplifier, a signal processing module, a control module, a wireless sending module and a power supply module connected in series; the power supply module provides power for the signal processing circuit board 8.

[0043] The thermoelectric potential E signal is first amplified by the amplifier, then converted into a corresponding digital signal by the signal processing module, and then filtered by the control module before the control signal is transmitted out by the wireless sending module.

[0044] After the signal is received by the upper computer through the wireless receiving module, corresponding signal storage is performed, and the user is presented.

[0045] Since the thermocouple wire 1 at the temperature measuring point is in contact with the contact surface of the stirring head 3 and the workpiece 4, the rest of the thermocouple wire 1 is insulated from the stirring head 3 by the peripheral temperature-resistant insulation layer 2. In this way, during the welding process of the workpiece 4 by the stirring head 3, high temperature is generated on the contact surface of the stirring head 3 and the workpiece 4 by friction, and a thermoelectric effect is formed between the thermocouple wire 1 and the stirring head 3. Therefore, the welding temperature at the temperature measuring point can be obtained by measuring the thermoelectric potential E of the thermocouple wire 1 away from the temperature measuring point.

[0046] The working principle of the temperature monitoring device for the core area of the friction stir welding joint is as shown in Figure 4 , three temperature measuring points are respectively arranged on the shoulder of the stirring head 3, the stirring pin of the stirring head 3 and the transition area between the two, and stepped holes are respectively arranged in the stirring head 3 for the three temperature measuring points, and a thermocouple wire 1 is respectively inserted into each stepped hole, forming a structure as shown in Figure 4 .

[0047] In the process of welding the workpiece 4 by the stirring head 3, the stirring head 3 is taken as a common end, and three wires are connected to the upper bare ends of the three thermocouple wires 1 respectively; the bottom bare ends of the three thermocouple wires 1 are in contact with the workpiece 4. Since the periphery of each thermocouple wire 1 is covered by the temperature-resistant insulation layer 2, three conductive loops are formed between the three thermocouple wires 1 and the stirring head 3. Based on the structure, the signal processing circuit board 8 is connected in the conductive loop, used for collecting the thermoelectric potentials E1, E2 and E3 between the three thermocouple wires 1 and the stirring head 3, and taking them as the temperature signals of the three temperature measuring points.

[0048] The application also provides a temperature monitoring method for a friction stir welding joint core area, which is realized based on the temperature monitoring device.

[0049] In step S101, a stepped hole is machined on the stirring head 3 according to the temperature measuring point position of the friction surface of the workpiece to be measured; the small hole section of the stepped hole is close to the temperature measuring point position;

[0050] In step S102, the thermocouple wire 1 is selected and put into the stepped hole of the stirring head 3, the bottom bare end of the thermocouple wire 1 is in close contact with the stirring head 3 at the temperature measuring point position, the upper bare end of the thermocouple wire 1 is connected to the columnar part of the stirring head through a wire to form a conductive loop, and the signal processing circuit board 8 is connected in the conductive loop; the remaining part of the thermocouple wire 1 is filled with a temperature-resistant insulation material to form the temperature-resistant insulation layer 2 between the thermocouple wire 1 and the stirring head 3.

[0051] In step S102, preferably, the height of the contact surface between the thermocouple wire 1 and the stirring head 3 at the temperature measuring point (i.e. the height of the bottom bare end of the thermocouple wire 1) is 0.1-20 mm.

[0052] In step S102, the thermocouple wire 1 selected is different in material from the stirring head 3, so that a thermoelectric effect can be formed between the thermocouple wire 1 and the stirring head 3 far from the temperature measuring point.

[0053] In step S103, the stirring head 3 is fixed in a clamping sleeve, the clamping sleeve is connected to a taper sleeve, and the taper sleeve is installed on the main shaft of the welding machine. In the process of welding the workpiece 4 by the stirring head 3, the bottom bare end of the thermocouple wire 1 is flush with the stirring head 3 and is in contact with the workpiece 4 at the same time;

[0054] In step S104, in the process of welding, the thermoelectric potential difference E between the thermocouple wire 1 and the stirring head 3 is collected by the signal processing circuit board 8 in the conductive loop as a temperature monitoring signal; the signal processing circuit board 8 is fixed on the taper sleeve, a battery module in the taper sleeve supplies power to the circuit, and the temperature signal line and the power line are connected to the signal processing circuit board 8 through the holes in the clamping sleeve and the taper sleeve.

[0055] In step S105, the detected thermoelectric potential difference E is transmitted to an external host computer via an amplification circuit and a wireless transmission module by using the signal processing circuit board 8, and data is stored and presented to the user.

[0056] In step S105, the processing and wireless transmission scheme of the thermoelectric potential signal E is as follows: the thermoelectric potential signal collected during the welding process of the stirring head 3 is amplified by using an AD595 chip, the signal is A / D converted by using an ADS1115 chip, the signal is wirelessly transmitted by using an NRF24l01 wireless transmission module, an STM32 single-chip microcomputer is selected as the control chip of the signal processing circuit board 8, and the entire signal processing circuit board 8 is powered by a single lithium battery. In the receiving end, the temperature measurement data is received by using an NRF24l01 wireless receiving module, and is transmitted to the host computer, and the signal is stored and displayed in real time.

[0057] The above description is only an application embodiment of the present application, but the protection scope of the present application is not limited thereto, and the protection scope of the present application should not be limited by the above description, and any equivalent changes made according to the technical solutions of the present application should be covered in the protection scope of the present application.

Claims

1. A device for monitoring the temperature of a friction stir welding weld nugget, characterized by, The temperature monitoring device comprises: A thermocouple wire (1); a temperature-resistant insulation layer (2); a stirring head (3); a workpiece (4); a welding machine spindle (5); a signal processing circuit board (8); The material of the thermocouple wire (1) is different from that of the stirring head (3); The stirring head (3) is driven to rotate by the welding machine spindle (5) of the welding machine to realize welding on the workpiece (4); the stirring head (3) is internally processed with a stepped hole; the thermocouple wire (1) coated with the temperature-resistant insulation layer (2) is placed in the stepped hole, and both ends of the thermocouple wire (1) are exposed, wherein the bottom exposed end is flush with the contact surface of the stirring head (3) and the workpiece (4) and contacts the workpiece (4) to be welded to form a temperature measuring point; the upper exposed end is connected to the signal processing circuit board (8) through a wire to form a conductive loop; The signal processing circuit board (8) collects the thermoelectric potential E signal of the thermocouple wire (1) and the stirring head (3) away from the temperature measuring point; the collected thermoelectric potential E signal is transmitted to an upper computer for storing and presenting data through the signal processing circuit board (8).

2. A device for monitoring the temperature of a friction stir welding joint core according to claim 1, characterized in that, The temperature monitoring device further comprises: A welding machine spindle (5); a cone sleeve (6); a clamping sleeve (9); The stirring head (3) is fixed in the clamping sleeve (9), the clamping sleeve (9) is connected with the cone sleeve (6), and the cone sleeve (6) is installed on the welding machine spindle (5) and rotates synchronously with the welding machine spindle (5) of the welding machine.

3. A device for monitoring the temperature of a friction stir welding joint core according to claim 1, wherein The signal processing circuit board (8) is fixed on the cone sleeve (6) and is powered by a battery module (7) fixed in the cone sleeve (6).

4. A device for monitoring the temperature of a friction stir welding joint core according to claim 1, wherein The signal processing circuit board (8) comprises: An amplifier, a signal processing module, a control module and a wireless sending module are connected in series and are powered by a power supply module; The thermoelectric potential E signal is first amplified by the amplifier, then converted into a corresponding digital signal by the signal processing module, and then transmitted out after the digital signal is denoised and filtered by the control module and the signal is transmitted out by the wireless sending module.

5. A device for monitoring the temperature of a friction stir welding joint core according to claim 1, wherein: The material of the thermocouple wire (1) is nickel-silicon alloy; the material of the stirring head (3) is H13 die steel; and alumina insulation ceramic is used.

6. A method of temperature monitoring of a friction stir weld joint core, characterized by, The temperature monitoring method is realized by using the temperature monitoring device for the core area of the friction stir welding seam according to any one of claims 1-5, and the temperature monitoring method comprises: Step S101, processing a stepped hole on the stirring head (3) according to the temperature measuring point position of the workpiece friction surface; the small hole section of the stepped hole is close to the temperature measuring point position; Step S102, selecting a thermocouple wire (1) to be placed in the stepped hole of the stirring head (3), the bottom exposed end of the thermocouple wire (1) is in close contact with the stirring head (3) at the temperature measuring point position, the upper exposed end of the thermocouple wire (1) is connected to the columnar part of the stirring head through a wire to form a conductive loop, and the signal processing circuit board (8) is connected in the conductive loop; the remaining part of the thermocouple wire (1) is filled with a temperature-resistant insulation material between the stirring head (3); the material of the thermocouple wire (1) is different from that of the stirring head (3). Step S103, the stirring head (3) is fixed in the jacket, the jacket is connected with the taper sleeve, the taper sleeve is installed on the welding machine spindle; in the process of welding the workpiece (4) by using the stirring head (3), the bottom bare end of the thermocouple wire (1) is flush with the stirring head (3) and is in contact with the workpiece (4) at the same time; Step S104, in the process of welding, the thermoelectric potential difference E between the thermocouple wire (1) and the stirring head (3) is collected by the signal processing circuit board (8) as a temperature monitoring signal; the signal processing circuit board (8) is fixed on the taper sleeve, the taper sleeve has a battery module to supply power to the circuit, and the temperature signal line and the power line are connected with the circuit board through the hole in the jacket and the taper sleeve; Step S105, using the signal processing circuit board (8), the detected thermoelectric potential difference E is transmitted to the external host computer for data storage and presentation through the amplification circuit and the wireless transmission module.

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