Methods for preventing oxidation of metals or alloys under non-vacuum conditions

Abstract

This invention relates to the field of metal or alloy heat treatment technology, specifically to a method for preventing oxidation during heating of metals or alloys under non-vacuum conditions. The method involves placing a cylindrical metal or alloy sample into a quartz tube, evacuating and sealing the quartz tube, then horizontally placing the quartz tube into a furnace for heating while simultaneously rotating it. This achieves uniform heating to prevent oxidation of the sample within a conventional non-vacuum furnace. This heating method is highly suitable for low-cost laboratory research on heating metal or alloy samples, offering a cost-effective anti-oxidation solution.

Description

Technical Field

[0001] This invention belongs to the field of metal or alloy heat treatment technology, specifically a method for preventing oxidation of metals or alloys under non-vacuum conditions. Background Technology

[0002] In the process of heat treatment of metals or alloys in the laboratory, the purchase of a vacuum furnace would significantly increase costs due to the small size of the samples. However, heating metals and alloys under non-vacuum furnace atmosphere protection or air conditions will result in varying degrees of oxidation. Therefore, how to perform anti-oxidation heat treatment on metal or alloy samples in the laboratory under non-vacuum conditions has become a technical problem that urgently needs to be solved in laboratory research.

[0003] Quartz has a low coefficient of linear expansion, good heat resistance and thermal shock resistance, and is currently widely used in laboratory equipment and the refining of special high-purity products. Since the softening temperature of this type of quartz is generally higher than 1700℃, it can be used for a long time in the temperature range of 1100~1200℃.

[0004] Chinese utility model patent publication CN210974796U discloses a heat treatment device and system that prevents metal samples from oxidizing by releasing a protective gas after heating using an anti-oxidation material. However, this device relies on a specific anti-oxidation material, limiting its application scenarios. Chinese invention patent publication CN106596620A discloses a small heating device for high-temperature experiments on micro-sized metal samples, which heats the metal sample by wrapping it with a heating element; however, its structure is complex and also limited by application scenarios. Summary of the Invention

[0005] Based on the aforementioned existing problems, this invention proposes a non-vacuum oxidation prevention heating method for cylindrical solid samples used in research processes in universities and research institutes. This method reduces the cost of laboratory equipment procurement, minimizes the impact of oxidation on experimental results, and improves the scientific validity of research findings. It has excellent application prospects and promotional value.

[0006] To address the aforementioned problems, the present invention adopts the following technical solution:

[0007] A method for preventing oxidation of metals or alloys under non-vacuum conditions using a heating device for preventing oxidation of metals or alloys under non-vacuum conditions. The heating device includes a furnace chamber, a quartz tube, and a rotating component. The furnace chamber includes a horizontally placed cylindrical furnace wall and end caps at both ends. Support bearings are provided at the same positions on both end caps. The two ends of the quartz tube are supported and rotatably connected by the support bearings. The output shaft of the rotating component is connected to one or both ends of the quartz tube. The rotating component is used to drive the quartz tube to rotate. The difference between the diameter of the inner wall of the quartz tube and the outer wall diameter of the metal or alloy being processed is 1~3mm.

[0008] Includes the following steps:

[0009] (1) Setting up materials and quartz tube: The metal or alloy sample to be processed is processed into a cylindrical structure, and a quartz tube is set up so that the difference between the diameter of the inner wall of the quartz tube and the diameter of the outer wall of the metal or alloy being processed is 1~3mm.

[0010] (2) Quartz tube encapsulation: One end of the quartz tube is sealed, the metal or alloy obtained in step (1) is placed into the quartz tube, and then the quartz tube is evacuated. After the vacuum degree inside the quartz tube is ≤0.1mbar, the other end of the quartz tube is sealed.

[0011] (3) Assembly device: The quartz tube is placed horizontally in the furnace, and the two ends of the quartz tube are supported and rotatably connected by the support bearings respectively. The output shaft of the rotating component is connected to one or both ends of the quartz tube.

[0012] (4) Sample heating: After step (3) is completed, start the rotating part to rotate the quartz tube and heat the furnace at the same time. After the temperature inside the furnace is 750-1150℃, keep it warm for 30-180 minutes. When the temperature inside the furnace has not reached 750-1150℃, the rotation speed of the quartz tube is 55-120 rpm. When the temperature inside the furnace reaches 750-1150℃ and keeps it warm, the rotation speed of the quartz tube is 32-50 rpm.

[0013] (5) End heating: After the holding time in step (4) is up, cool down (using air cooling, oil cooling, water cooling, furnace cooling or other cooling media). After cooling down to room temperature, break the quartz tube and take out the metal or alloy sample to complete the heating treatment.

[0014] Preferably, both the furnace wall and the end cap are made of refractory material.

[0015] Preferably, the sealing process in step (2) is performed by melting and sealing with an oxygen-hydrogen flame, and the vacuuming process is performed by using a vacuum pump.

[0016] Preferably, the rotating component is a motor.

[0017] Preferably, in step (1), the metal or alloy sample to be processed is processed into a cylindrical structure, and the diameter of the cylindrical structure is 20~150mm.

[0018] Preferably, the quartz tube is made of quartz material with a softening temperature higher than 1200°C.

[0019] Preferably, when the temperature inside the furnace is below 420~480℃, the rotation speed of the quartz tube is 80~120 rpm; when the temperature inside the furnace is above 420~480℃ but below 750~1150℃, the rotation speed of the quartz tube is 55~80 rpm.

[0020] Preferably, a heating element is provided inside the furnace.

[0021] Preferably, the rotational speed of the quartz tube is set to have a linear relationship with the temperature inside the furnace. As the temperature inside the furnace increases, the rotational speed of the quartz tube increases linearly. The ratio of the temperature inside the furnace to the rotational speed of the quartz tube is (5~33):1. The unit of the temperature inside the furnace is °C, and the unit of the rotational speed of the quartz tube is revolutions per minute. The maximum rotational speed is set to 100 revolutions per minute, and the minimum rotational speed is set to 32 revolutions per minute.

[0022] Preferably, the output shaft of the rotating component is engaged with one or both ends of the quartz tube by a snap-fit ​​fastener; one of the two end caps has a through hole at the support bearing, and the other has a blind hole at the other support bearing.

[0023] The technical advantages of this invention are as follows:

[0024] (1) The present invention first places the sample into a quartz tube, and then heats the quartz tube in a conventional heating furnace by evacuating the quartz tube. The quartz tube then transfers heat to the sample to achieve the effect of anti-oxidation heating of the sample under non-vacuum heating furnace conditions. Since the vacuum tube also needs to be sealed, evacuating the quartz tube is simpler and easier than filling it with inert gas. The present invention achieves the effect of anti-oxidation of the sample by vacuum heating in a non-vacuum furnace by heating the sample in a vacuum quartz tube, thereby greatly reducing the cost of efficient heating of metal or alloy samples in the laboratory (no need to purchase a vacuum furnace) and improving the experimental efficiency of the laboratory.

[0025] (2) Since the quartz tube is in a near-vacuum state and lacks air for heat transfer, if it is placed directly into the furnace, only one contact line will transfer heat to the sample, resulting in uneven heat transfer. Although this achieves the purpose of preventing oxidation, it also causes uneven heating. This invention rotates the quartz tube so that the outer surface of the sample is in contact with the quartz tube for heat transfer, thereby transferring heat from the entire outer circumference of the sample and achieving the effect of uniform heating of the sample.

[0026] (3) The setting of the rotation speed of the quartz tube is also a key point of this invention. The rotation speed is coordinated with the gap between the quartz tube and the sample. If the rotation speed is too fast, the sample will rotate along with the quartz tube due to the centrifugal force. If it is too slow, the heating uniformity will be insufficient. However, if the rotation speed continues to be fast at high temperature, it will cause pressure on the outer circumference of the sample and cause a slight deformation of the sample. Therefore, the setting of the rotation speed is a specific processing method based on the specific setting method of this invention. This invention uses a relatively high rotation speed (not too high) at low temperature to ensure efficient and uniform heat transfer. As the temperature rises, the rotation speed is gradually reduced. On the basis of ensuring uniform heat transfer, the sample will not be deformed. This allows the sample to be protected from oxidation and maintain its stability while achieving the effect of uniform heating of the sample. Attached Figure Description

[0027] Figure 1 This is a cross-sectional structural schematic diagram of the heating device of the present invention.

[0028] Figure 2 This is a morphological image of the metal or alloy sample after treatment in Example 1.

[0029] Figure 3 The image shows the morphology of the metal or alloy sample after treatment in Comparative Example 1.

[0030] Figure 4 This is a morphological image of the metal or alloy sample after treatment in Example 2.

[0031] Figure 5 The image shows the morphology of the metal or alloy sample after treatment in Comparative Example 2.

[0032] Figure 6 This is a morphological image of the metal or alloy sample after treatment in Example 3.

[0033] Figure 7 The image shows the morphology of the metal or alloy sample after treatment in Comparative Example 3.

[0034] Figure 8 The image shows the morphology of the metal or alloy sample after treatment in Comparative Example 4.

[0035] Figure 9The image shows the morphology of the metal or alloy sample after treatment in Comparative Example 5.

[0036] Explanation of reference numerals in the attached drawings: 1-metal or alloy sample, 2-quartz tube, 3-end cap of the furnace chamber, 4-support bearing, 5-output shaft of rotating component, d-diameter of metal or alloy sample, D-diameter of quartz tube. Detailed Implementation

[0037] Any feature disclosed in this specification, unless specifically stated otherwise, may be replaced by other equivalent or similar features. Unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features. The description is merely to aid in understanding the invention and should not be construed as a specific limitation thereof.

[0038] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The descriptions of positional relationships in the drawings are for illustrative purposes only and should not be construed as limiting the invention. The invention will now be further described in detail with reference to specific embodiments.

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0040] The specific implementation mainly involves the following steps: measuring the outer diameter of the cylindrical solid sample → selecting the quartz tube → sealing one end of the quartz tube → placing the sample in → vacuuming → sealing the other end of the quartz tube → rotating the quartz tube to heat the sample → surface observation.

[0041] like Figure 1 The heating device shown includes a furnace chamber, a quartz tube 2, and a motor. The furnace chamber includes a horizontally placed cylindrical furnace wall and end caps 3 at both ends. Support bearings 4 are located at corresponding positions on both end caps. The two ends of the quartz tube are supported and rotatably connected by these support bearings. The output shaft 5 of a rotating component is connected to one end of the quartz tube. The motor drives the rotation of the quartz tube. The difference between the inner diameter of the quartz tube and the outer diameter of the metal or alloy being processed is 1-3 mm. A metal or alloy sample 1 with a diameter of d is placed inside the quartz tube, and the diameter of the quartz tube is D. In other embodiments, the end of the quartz tube not connected to the motor can rotate inside the furnace chamber through a blind hole on the end cap and the support bearings. Specific heating methods and comparative data are as follows.

[0042] Example 1:

[0043] (1) Select TC4, 45 steel and Q235 steel samples with a diameter d of φ9mm. All of them are cylindrical samples. Select a quartz tube with a diameter D of φ11mm and then encapsulate the quartz tube.

[0044] (2) Seal one end of the quartz tube with an acetylene-oxygen flame, place the metal sample in, and vacuum the quartz tube with a vacuum pump. When the vacuum level is lower than 0.1 mbar, seal the other end of the quartz tube with a flame.

[0045] (3) Heat treatment of metal samples: The packaged metal sample is placed in a heating furnace, and the motor is started to rotate the quartz tube while heating the furnace. Once the furnace temperature reaches 1150℃, it is held for 90 minutes. The rotation speed of the quartz tube is 100 rpm when the furnace temperature is below 480℃, and 60 rpm when the furnace temperature is above 480℃ but below 1150℃. After holding at 1150℃, the rotation speed of the quartz tube is 35 rpm. After holding for 90 minutes, the sample is removed, and the heated sample is obtained as shown below. Figure 2 As shown, where Figure 2 (a) is the Q235 sample. Figure 2 (b) is a 45 steel sample. Figure 2 (c) is a TC4 titanium alloy sample.

[0046] Comparative Example 1:

[0047] This comparative example did not use the heating device described in Example 1 for encapsulation. Instead, the sample was directly placed into the furnace for heating. The heating temperature and holding time were the same as in Example 1. The morphology of the heated sample is as follows. Figure 3 As shown, where Figure 3 (a) is the Q235 sample. Figure 3 (b) is a 45 steel sample. Figure 3 (c) is a TC4 titanium alloy sample. By comparing Example 1 and Comparative Example 1, it can be concluded that when the metal or alloy sample encapsulated in the quartz tube is heated using the method of the present invention as in Example 1, the test process is stable, the metal sample does not react with the quartz during the heating process, the sample surface is good and no oxidation occurs, while the sample obtained in Comparative Example 1 has a thick oxide layer on the surface and is unusable.

[0048] Example 2:

[0049] (1) Make a φ10mm 45 steel cylindrical sample, select a φ11mm quartz tube, and then encapsulate the quartz tube.

[0050] (2) Seal one end of the quartz tube with an acetylene-oxygen flame, place the 45 steel sample in, and vacuum the quartz tube with a vacuum pump. When the vacuum level is lower than 0.1 mbar, seal the other end of the quartz tube with a flame.

[0051] (3) Heat treatment of 45 steel samples: The packaged metal sample is placed in a heating furnace, and the motor is started to rotate the quartz tube while heating the furnace. After the temperature inside the furnace reaches 850℃, 950℃, 1050℃ or 1150℃ respectively, it is held for 90 minutes. When the temperature inside the furnace does not reach 450℃, the rotation speed of the quartz tube is 90 rpm. When the temperature inside the furnace is higher than 450℃ but does not reach 850℃, 950℃, 1050℃ or 1150℃, the rotation speed of the quartz tube is 65 rpm. After holding the temperature inside the furnace at 850℃, 950℃, 1050℃ or 1150℃, the rotation speed of the quartz tube is 45 rpm.

[0052] The encapsulated 45 steel sample was placed in a heating furnace and heated to 850℃, 950℃, 1050℃, and 1150℃ respectively under non-vacuum conditions for 90 minutes. The resulting metallographic morphology of the sample surface is shown below. Figure 4 As shown, where Figure 4 (a) The sample treated at 850℃, Figure 4 (b) The sample treated at 950℃, Figure 4 (c) is a sample treated at 1050℃. Figure 4 (d) is the sample treated at 1150℃.

[0053] The above method was used to conduct heating tests on 45 steel samples encapsulated in quartz tubes. The test process was stable, and the samples did not react with quartz during heating at different temperatures. The surface and interior of the samples were in good condition and no oxidation occurred.

[0054] Comparative Example 2:

[0055] This comparative example did not use the heating device described in Example 2 for encapsulation. Instead, the sample was directly placed into the furnace for heating. The sample used was also a 45 steel sample, and the heating time was the same as in Example 2: 850℃, 950℃, 1050℃, and 1150℃, with a heating time of 90 minutes. The resulting metallographic morphology of the sample surface was as follows: Figure 5 As shown, where Figure 5 (a) The sample treated at 850℃, Figure 5 (b) The sample treated at 950℃, Figure 5 (c) is a sample treated at 1050℃. Figure 5(d) Samples treated at 1150℃. By comparing Example 2 with Comparative Example 2, it can be concluded that when metal or alloy samples encapsulated in quartz tubes are heated using the method of the present invention as in Example 2, the test process is stable, the metal samples do not react with quartz during heating, the sample surfaces are all in good condition and no oxidation occurs, while the samples obtained in Comparative Example 2 all have obvious thick oxide layers on their surfaces, and some samples have changed shape and are unusable.

[0056] Example 3:

[0057] (1) Select a 15mm TC4 sample and a 17mm quartz tube, and then encapsulate the quartz tube.

[0058] (2) Seal one end of the quartz tube with an acetylene-oxygen flame, place the TC4 sample in, and vacuum the quartz tube with a vacuum pump. When the vacuum level is lower than 0.1 mbar, seal the other end of the quartz tube with a flame.

[0059] (3) Heat treatment of 45 steel samples: The packaged TC4 samples were placed in a heating furnace, and the motor was started to rotate the quartz tube while heating the furnace. After the furnace temperature reached 1080℃, the samples were held for 65 minutes. The rotation speed of the quartz tube was 85 rpm when the furnace temperature was below 450℃, and 65 rpm when the furnace temperature was above 450℃ but below 1080℃. After holding at 1080℃, the rotation speed of the quartz tube was 38 rpm. After 65 minutes of holding, the metallographic morphology of the sample surface was obtained as follows: Figure 6 As shown.

[0060] The heating test of the TC4 sample packaged in the quartz tube was carried out using the above method. The test process was stable. The sample did not react with the quartz during the heating process. The surface and interior of the sample were in good condition and no oxidation occurred.

[0061] Comparative Example 3:

[0062] This comparative example did not use the heating device described in Example 3 for encapsulation. Instead, the sample was directly placed into the furnace for heating. The sample used was also a TC4 sample, and the heating temperature and holding time were the same as in Example 3, at 65 minutes. The resulting metallographic morphology of the sample surface was as follows. Figure 7 As shown. By comparing Example 3 with Comparative Example 3, it can be concluded that when the metal or alloy samples encapsulated in quartz tubes are heated using the method of the present invention as in Example 3, the test process is stable, the metal samples do not react with quartz during heating, the sample surfaces are all in good condition and no oxidation occurs, while the samples obtained in Comparative Example 3 all have obvious thick oxide layers on their surfaces, and some samples have changed shape and are unusable.

[0063] Comparative Example 4:

[0064] The other settings of this comparative example are the same as in Example 3, except that the quartz tube is not rotated; it is directly placed horizontally into the furnace for heating. The heating and holding temperatures and times are the same as in Example 3. After treatment, the metallographic morphology of the sample surface is as follows: Figure 8 As shown. From Figure 8 It can be seen that although TC4 was not oxidized during the experiment, it was not heated evenly during the heating process. Figure 8 The agglomerates shown at the cross-section of the medium sample were significantly larger than those at the cross-section of Example 3. Figure 6 The sample cross-section is finer because, in this comparative example, there is no rotation, and the quartz tube only has one line surface in contact with and heats the sample, resulting in uneven heating of the sample.

[0065] Comparative Example 5:

[0066] The other settings in this comparative example are the same as in Example 3, except that the rotation speed of the quartz tube is maintained at 38 rpm regardless of the temperature range. The heating and holding temperatures and holding times are the same as in Example 3. After other treatments are the same as in Example 3, the morphology of the obtained sample is as follows. Figure 9 As shown, the topographic diagram and Figure 6 There is not much difference, but because the rotation speed is kept at 38 rpm, the heating uniformity is reduced at low temperature compared to Example 3. As a result, the particle size of the agglomerates shown in the cross section is slightly larger, and its strength and other properties are reduced compared to Example 3. This proves that the different rotation speeds set in Example 3 at each stage are the optimal settings.

Claims

1. A method for preventing alloy oxidation during heating under non-vacuum conditions, characterized in that, An alloy anti-oxidation heating device under non-vacuum conditions is used, including a furnace chamber, a quartz tube with a softening temperature higher than 1200℃, and a rotating component. The furnace chamber includes a horizontally placed cylindrical furnace wall and end caps at both ends. Support bearings are provided at the same position on both end caps. The two ends of the quartz tube are supported and rotatably connected by the support bearings. The output shaft of the rotating component is connected to one or both ends of the quartz tube. The rotating component is used to drive the rotation of the quartz tube. Includes the following steps: (1) Setting up materials and quartz tube: The solid alloy sample to be processed is made into a cylindrical structure with a diameter of 20~150mm. The quartz tube is set up so that the difference between the inner diameter of the quartz tube and the outer diameter of the sample to be processed is 1~3mm. (2) Quartz tube encapsulation: One end of the quartz tube is sealed. After the sample obtained in step (1) is placed into the quartz tube, the quartz tube is evacuated. After the vacuum degree inside the quartz tube is ≤0.1mbar, the other end of the quartz tube is sealed. (3) Assembly device: The quartz tube is placed horizontally in the furnace, and both ends of the quartz tube are supported and rotatably connected by support bearings. The output shaft of the rotating part is connected to one end of the quartz tube. (4) Sample heating: After step (3) is completed, start the rotating part to rotate the quartz tube and heat the furnace at the same time. After the temperature inside the furnace is 750-1150℃, keep it warm for 30-180 minutes. When the temperature inside the furnace is not 480℃, the rotation speed of the quartz tube is 80-120 rpm. When the temperature inside the furnace is higher than 480℃ but not 750℃, the rotation speed of the quartz tube is 55-80 rpm. When the temperature inside the furnace reaches 750-1150℃ and is kept warm, the rotation speed of the quartz tube is 32-50 rpm. (5) End heating: After the heat preservation time is up, cool down. After cooling to room temperature, break the quartz tube and take out the sample to complete the heat treatment.

2. The alloy anti-oxidation heating method under non-vacuum conditions according to claim 1, characterized in that, Both the furnace wall and the end cap are made of refractory material.

3. The alloy anti-oxidation heating method under non-vacuum conditions according to claim 1, characterized in that, The sealing process in step (2) is to use an oxygen-hydrogen flame for melting and sealing, and the vacuuming process is to use a vacuum pump for vacuuming.

4. The alloy anti-oxidation heating method under non-vacuum conditions according to claim 1, characterized in that, The rotating component is a motor.

5. The alloy anti-oxidation heating method under non-vacuum conditions according to claim 1, characterized in that, Heating components are installed inside the furnace.

6. The alloy anti-oxidation heating method under non-vacuum conditions according to claim 1, characterized in that, The output shaft of the rotating component is engaged with one or both ends of the quartz tube by a snap-fit ​​fastener; one of the two end caps has a through hole at the support bearing, and the other has a blind hole at the other support bearing.

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