Compact multi-atmosphere heat treatment tube furnace

Abstract

A compact type multi-atmosphere heat treatment tube furnace comprises a sample heating area, a gas cylinder and a diaphragm pump, the gas cylinder and the diaphragm pump are arranged at the inlet end and the outlet end of the sample heating area respectively, a gas flowmeter and a first flange are sequentially arranged between the sample heating area and the gas cylinder, and a second flange and a third valve are sequentially arranged between the sample heating area and the diaphragm pump. On the basis of the small-size heating furnace, the diaphragm pump serves as the vacuum system, the sample heat treatment environment is controlled through the gas flow meter or the vacuum system, the size of the device can be reduced under the condition that the high vacuum degree is guaranteed, and multi-advantage heat treatment with the high vacuum degree and multiple atmospheres is achieved.

Description

Technical Field

[0001] The present invention relates to a technology in the field of heating devices, and specifically to a compact multi-atmosphere heat treatment tube furnace. Background Art

[0002] Tube furnaces have been widely used in many industries such as heat treatment, chemistry, and new energy. Due to their advantages of stable temperature, simple operation, and controllable heating and cooling, they are widely used in scientific research institutions and production factories. However, traditional tube furnaces have disadvantages such as large volume, which will lead to a large floor space, and the relatively large diameter of the quartz tube results in a high gas flow rate when the gas passes through the sample, causing gas waste and volume ratio deviation. Reducing the volume of the tube furnace and the length of the quartz tube can shorten the length of the heating uniform zone, that is, the effective utilization of the space for sample heat treatment can be achieved. Summary of the Invention

[0003] Aiming at the deficiencies that the prior art cannot accurately represent the true difference between the actual temperature and the controlled temperature of heat treatment and fails to reasonably control the volume of the sample placement area of the tube furnace according to the sample size, the present invention provides a compact multi-atmosphere heat treatment tube furnace, which is based on a small-volume heating furnace and uses a diaphragm pump as the vacuum system. The heat treatment environment of the sample is controlled by a gas flow meter or the vacuum system, and the volume of the device can be reduced while ensuring a high vacuum degree to achieve multi-advantage heat treatment with high vacuum and multi-atmospheres.

[0004] The present invention is realized through the following technical solutions:

[0005] The present invention relates to a compact multi-atmosphere heat treatment tube furnace, including: a sample heating zone, and a gas cylinder and a diaphragm pump respectively arranged at its inlet end and outlet end. Among them: a gas flow meter and a first flange are successively arranged between the sample heating zone and the gas cylinder, and a second flange and a third valve are successively arranged between the sample heating zone and the diaphragm pump.

[0006] A pressure gauge and a first valve are further arranged between the gas flow meter and the first flange.

[0007] A cold cathode Pirani vacuum gauge and a second valve with a pressure relief valve are further arranged between the second flange and the third valve.

[0008] A thermocouple connected to the temperature control system is further arranged in the sample heating zone of the compact multi-atmosphere heat treatment tube furnace, and this thermocouple is specifically located at the center of the quartz tube of the tube furnace. Technical Effects

[0009] In the present invention, a thermocouple is installed inside a quartz tube to display the real-time temperature in the central area of the tube. By comparing the temperature shown on the thermocouple temperature display instrument with the preset temperature, the temperature difference can be understood, so as to adjust and control the real temperature inside the tube to the preset temperature value for sample heat treatment. The size of the furnace body of the tube furnace in the present invention is 500×400×600 mm (length×width×height). At the same time, the normal heating module and the heating furnace chamber are retained, which greatly reduces the volume of the tube furnace while ensuring the heating power. 3. By using furnace tubes and flange connection ports of multiple sizes and replaceable ones, as well as supporting encapsulation sheets, heat treatment processes for samples of different sizes can be realized. At the same time, a small-volume diaphragm pump is configured to achieve a vacuum atmosphere. Thus, while maintaining the compact characteristics, the function of adjustable heating zone space can be realized by changing the volume of the furnace tube area where the sample is placed. Compared with the prior art, the present invention aims at a thermal aging treatment device for samples under different atmospheres. With the sample heating zone, vacuum system and each pipeline path as the main structure, multiple functional valves such as an intake valve and a pressure relief valve are installed, and together they form the high-vacuum heat treatment tube furnace. This system comprehensively considers key issues such as the volume and vacuum degree of the heat treatment furnace. By reducing the volume of the tube furnace and the diameter of the furnace tube, the vacuum extraction time can be shortened. When the diaphragm pump runs at full speed, the vacuum degree can reach up to 10 -3 Pa, fully meeting the requirements for heat treatment of materials in a high-vacuum state. The design of the compact tube furnace follows the concept of small volume, multiple atmospheres, and fast vacuum. The improved compact tube furnace can reasonably combine the reduction of the overall size of the tube furnace and the functions of fast and low vacuum. When facing a relatively large heating sample, the supporting furnace tube and connecting flange can be replaced according to the sample size. The positions where both ends of the furnace chamber are in contact with the external environment are encapsulated with replaceable alumina encapsulation sheets of different sizes to prevent heat from escaping. When facing a multi-atmosphere environment, it will be connected to a gas cylinder with the help of a differential pressure flowmeter, and the flowmeter is adjusted to control the flow rate of each gas to meet the requirements of different heat treatment atmospheres. During the actual operation process, the appropriate heating rate and cooling rate are selected according to the characteristics of the sample. The temperature control accuracy of the tube furnace is within ±1°C, and a thermocouple is installed inside the quartz tube to detect the real temperature around the sample, so as to accurately simulate the actual application conditions of the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic structural diagram of the present invention;

[0011] In the figure: gas cylinder 1, gas flowmeter 2, pressure gauge 3, first valve 4, clamp 5, first flange 6, sample heating zone 7, second flange 8, cold cathode Pirani vacuum gauge 9, second valve 10, pressure relief valve 11, third valve 12, diaphragm pump 13;

[0012] Figure 2 is a schematic diagram of an embodiment;

[0013] In the figure: gas inlet and outlet 14, thermocouple 15, temperature control system 16, temperature display 17;

[0014] Figure 3 Bright-field image of the intermediate layer of the three samples in Example 3;

[0015] Figure 4 Schematic diagram of the element distribution of the Cr / Zr intermediate layer under three heat treatment conditions;

[0016] Figure 5 Schematic diagram of the effect of the example. Detailed implementation manners

[0017] As Figure 1 shown, this embodiment relates to a compact multi-atmosphere heat treatment tube furnace, including: a sample heating zone 7, and a gas cylinder 1 and a diaphragm pump 13 respectively arranged at its inlet end and outlet end, wherein: a gas flow meter 2 and a first flange 6 are successively arranged between the sample heating zone 7 and the gas cylinder 1, and a second flange 8 and a third valve 12 are successively arranged between the sample heating zone 7 and the diaphragm pump 13.

[0018] A pressure gauge 3 and a first valve 4 are further arranged between the gas flow meter 2 and the first flange 6.

[0019] A cold cathode Pirani vacuum gauge 9 and a second valve 10 with a pressure relief valve 11 are further arranged between the second flange 8 and the third valve 12.

[0020] As Figure 2 shown, the compact multi-atmosphere heat treatment tube furnace further includes: a thermocouple 15 located in the sample heating zone 7 and connected to a temperature control system 16, and the thermocouple 15 is specifically located at the center of the quartz tube of the tube furnace.

[0021] By adding a thermocouple, the relationship between the set temperature of the tube furnace and the actual temperature inside the tube is established to ensure that the heat treatment temperature of the sample meets the expectation.

[0022] The compact multi-atmosphere heat treatment tube furnace involved in this embodiment has a length of 500 mm, a height of 600 mm, and a width of 400 mm.

[0023] A clamp 5 is provided at the inlet end of the first flange 6 and tightened after the sample is introduced.

[0024] The furnace lining of the tube furnace is made of high-purity alumina polycrystalline fiber material, and it can be heated at a maximum rate of 10 °C / min, and the maximum heating temperature is 1200 °C. After loading the sample, it can be heated to a lower temperature for short-term air extraction to discharge water vapor or other impurity gases in the tube.

[0025] As Figure 2 shown, the heat treatment method based on the above-mentioned compact multi-atmosphere heat treatment tube furnace in this embodiment includes:

[0026] Step 1: When placing the sample, close the first valve, open the clamp, use an iron hook to push the porcelain boat containing the sample into the center position of the furnace tube, keep the terminal of the thermocouple at the same position as the porcelain boat to ensure that the temperature shown by the thermocouple is the temperature around the sample, and tighten the clamp.

[0027] Step 2: The left inlet / outlet of the tube furnace is used to connect the gas cylinder to input single / mixed atmosphere, or after vacuum heat treatment test, open the first valve to restore normal pressure in the furnace tube. Specifically, it includes: when atmosphere heat treatment is required, connect the gas cylinder to the flow meter, combine the set mixing gas ratio and the flow meter index, connect to the inlet / outlet, open the first valve, and close the second valve. Select the closed atmosphere thermal effect or the flowing atmosphere thermal effect according to the heat treatment requirements. For closed atmosphere heat treatment, close the second valve, and the pressure relief valve prevents the pressure in the tube from being too high. For flowing atmosphere heat treatment, open the second valve, and the atmosphere passes through the sample in the tube and is discharged into the air. After the experiment ends, close the second valve, disconnect the connection between the gas cylinder and the inlet / outlet, and open the first valve to discharge the residual gas in the tube. In the vacuum heat treatment experiment, after opening the first valve to restore normal pressure in the tube, close it, turn on the first-stage pump and the second-stage pump of the diaphragm pump in sequence to evacuate the tube, and start the heating program after the vacuum degree value is stable.

[0028] After specific actual experiments, in the specific actual experiment of Cr-coated zirconium alloy, after placing the sample, in the specific environment setting requiring vacuum, close the first valve and the second valve, open the diaphragm pump and wait for the vacuum value to be stable, and start the tube furnace at a uniform heating rate (7 °C / min), and the diffusion thickness of the intermediate layer of Cr-coated zirconium alloy at different temperatures and times can be obtained. Detect the growth of the interface intermediate layer of Cr-coated zirconium alloy at a certain temperature (taking the vacuum environment as the experimental condition). The Cr-coated zirconium alloy prepared by the multi-arc ion plating method is used as the heat treatment sample, and the thickness of the Cr coating is about 20 ± 1 μm. Different temperature vacuum heat treatment experiments are carried out with the help of this device. The test conditions are 650 °C (3d), 650 °C (7d), and 650 °C (14d), and the vacuum degree can reach 3×10 - 3 Pa. Before each heating to the predetermined temperature for heat treatment, it is necessary to keep warm at about 200 °C - 300 °C for more than 6 h in a vacuum environment to prevent the influence of residual water vapor or impurity gas in the tube on the heat treatment effect.

[0029] As Figure 3 shown, multiple sets of quartz furnace tubes and connecting end flanges designed for heat treatment samples of different sizes can flexibly select the appropriate furnace tube size according to the sample size. Each furnace tube size is matched with the corresponding size alumina encapsulation sheet for encapsulating the contact positions of both ends of the heating furnace tube with the external environment, which can ensure the stability of the heat in the heating area.

[0030] As Figure 4As shown, the growth of the Cr-coated zirconium alloy intermediate layer and the elemental line scan results at three durations under the same heat treatment temperature are presented. The growth of the interface intermediate layer under vacuum can be obtained. In this embodiment, a scanning electron microscope will be used, and the interface thickness results will be characterized based on the elemental distribution in the cross-sectional direction as the device performance verification data. As Figure 4 can be seen, the time effect is obvious. At the same temperature, as the time increases, the thickness of the intermediate layer increases significantly. During the heat treatment stage, the vacuum degree inside the tube is always maintained at 10 -3 Pa. According to the temperature difference between the resistance wire temperature and the thermocouple temperature inside the tube, the temperature control system is set to keep the thermocouple temperature at 650 °C to ensure the accuracy of the heat treatment temperature.

[0031] The growth law of the Cr-coated zirconium alloy intermediate layer is essentially the interdiffusion between Cr atoms and Zr atoms. Since the Zr-4 alloy contains a small amount of Fe element, the Fe atoms are smaller and have a faster diffusion rate, which ultimately leads to the Cr / Zr intermediate layer being the Zr(Fe,Cr)2 compound. Based on the diffusion kinetics model following δ n = K×τ, where: δ is the thickness of the intermediate layer, K is the reaction constant, and τ is the time (unit: second). After logarithmic transformation, nlogδ = logK + logτ is obtained, and then logτ and logδ have a linear relationship. Taking logδ as the x-axis and logδ as the y-axis.

[0032] The thickness of the Cr / Zr intermediate layer under three heat treatment conditions obtained from the scanning electron microscope energy spectrum results is shown in Table 1.

[0033] Table 1 Line scan thickness of the Cr / Zr intermediate layer under three heat treatment conditions Sample Name Experimental Conditions Line Scan Thickness of Cr / Zr Intermediate Layer Sample 1 Hold at 650°C for 3 days 0.7μm Sample 2 Hold at 650°C for 7 days 1.2μm Sample 3 Hold at 650°C for 14 days 2.0μm

[0034] According to the growth thickness of the intermediate layer at different durations at 650 °C and combined with the relationship formula, Figure 5 is obtained. The square points in the figure represent the intermediate layer thickness data at three durations, and the red line is the fitting curve of the three data points. As Figure 5 shown, through the heat treatment data measured by the compact heat treatment tube furnace proposed in the embodiment of the present application, the duration effect is obvious, and there is a relatively good linear relationship between the test data points, indicating that the growth kinetics of the intermediate layer is consistent, the device has strong reliability, and the experimental results are highly persuasive.

[0035] Due to the differences in the temperature control of the tube furnace at high and low temperatures, the present invention obtains the true temperature value around the sample by means of a thermocouple, establishes the relationship between the preset temperature value and the difference in the true temperature value, and can effectively achieve precise temperature control. At the same time, multiple sets of furnace tubes and connecting flanges with different diameters are configured, and the heating tube can be flexibly selected according to the sample size. The alumina encapsulation sheet is used to seal the positions where the two ends of the heating end are in contact with the air to maintain temperature stability. By reducing the size of the heating furnace chamber and the sample area, the power requirement for the vacuum system is reduced, and a diaphragm pump is introduced as a vacuum extraction device, thereby realizing a compact heat treatment device with multiple advantages such as small volume, accurate temperature control, and rapid vacuum extraction.

[0036] With the formation of a conservation-minded society and the breakthrough development of new energy technologies, the market share of new energy vehicles has gradually increased, thus putting forward higher requirements for new energy application materials, that is, they need to meet standards such as high safety, high performance, and high usability. In order to enhance the performance of the application materials in new energy vehicles, the heat treatment process is indispensable. Body structures such as high-strength steel and aluminum-magnesium alloy need to be pre-heat-treated to improve their strength while maintaining good plasticity and toughness. Appropriate heat treatment conditions can enhance the conductivity of the battery system and extend the cycle life of the battery. This device can be used for the research of the heat treatment process in the application materials of new energy vehicles and plays an important role in improving material properties and reducing energy consumption.

[0037] The above specific embodiments can be locally adjusted in different ways by those skilled in the art without departing from the principles and purposes of the present invention. The protection scope of the present invention is subject to the claims and is not limited by the above specific embodiments, and all implementation solutions within its scope are subject to the constraints of the present invention.

Claims

1. A compact multi-atmosphere heat treatment tube furnace, characterized in that, Comprising: A sample heating zone, a gas cylinder and a diaphragm pump respectively arranged at its inlet end and outlet end, wherein: a gas flow meter and a first flange are successively arranged between the sample heating zone and the gas cylinder, and a second flange and a third valve are successively arranged between the sample heating zone and the diaphragm pump.

2. The compact multi-atmosphere heat treatment tube furnace according to claim 1, wherein A pressure gauge and a first valve are further arranged between the gas flow meter and the first flange.

3. The compact multi-atmosphere heat treatment tube furnace according to claim 1, wherein A cold cathode Pirani vacuum gauge and a second valve with a pressure relief valve are further arranged between the second flange and the third valve.

4. The compact multi-atmosphere heat treatment tube furnace according to claim 1, characterized in that, further There is provided: a thermocouple located in the sample heating zone and connected to the temperature control system, and this thermocouple is specifically located at the center of the quartz tube of the tubular furnace.

5. A heat treatment method for the compact multi-atmosphere heat treatment tube furnace according to any one of claims 1-4, characterized in that, Comprising: Step 1: When placing the specimen, close the first valve, open the clamp, use an iron hook to push the porcelain boat containing the sample into the center position of the furnace tube, make the terminal of the thermocouple keep the same position as the porcelain boat, ensure that the temperature displayed by the thermocouple is the temperature around the sample, and tighten the clamp; Step 2: The left inlet / outlet of the tubular furnace is used to connect the gas cylinder to input single / mixed atmosphere, or after the vacuum heat treatment test, open the first valve to restore normal pressure in the furnace tube. Specifically including: when atmosphere heat treatment is required, connect the gas cylinder to the flow meter, combine the set mixing gas ratio and the flow meter index, connect to the inlet / outlet, open the first valve, close the second valve, select the closed atmosphere thermal effect or the flowing atmosphere thermal effect according to the heat treatment requirements. For closed atmosphere heat treatment, close the second valve, and the pressure relief valve prevents the pressure in the tube from being too high. For flowing atmosphere heat treatment, open the second valve, and the atmosphere is discharged to the air after passing through the sample in the tube. After the experiment is over, close the second valve, disconnect the connection between the gas cylinder and the inlet / outlet, open the first valve to discharge the residual gas in the tube. In the vacuum heat treatment experiment, after opening the first valve to restore normal pressure in the tube, close it, successively turn on the first-stage pump and the second-stage pump of the diaphragm pump to evacuate the tube, and start the heating program after waiting for the vacuum degree value to be stable.

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