A stopper for continuous casting and its preparation method

Abstract

This application relates to the technical field of refractories, and specifically discloses a stopper rod for continuous casting and its preparation method. A stopper rod for continuous casting includes a rod body, a rod head, and a slag line. The material of the rod body is aluminum-magnesium-carbon, the material of the rod head is magnesium-carbon, and the material of the slag line is aluminum-magnesium-carbon. The thermal deformation rates of each part are relatively close, avoiding the fracture or chipping of the stopper rod due to excessive differences in thermal deformation rates during use. In addition, a composite graphite composed of ultra-fine flake graphite, expanded graphite, and isostatic graphite is added to the raw materials for preparing the rod head, which can improve the erosion resistance of the rod head while ensuring thermal shock resistance; zircon mullite and calcium oxide are added to the raw materials for preparing the slag line, improving the erosion resistance and thermal shock resistance of the slag line, thereby further reducing the occurrence of cracking and chipping of the rod head and slag line.

Description

Technical Field

[0001] The present application relates to the field of refractories, and particularly to a stopper rod for continuous casting and a preparation method thereof. Background Art

[0002] The stopper rod is a very important functional refractory material in continuous casting steel pouring. It is installed in the ladle and controls the opening and closing of the nozzle and the molten steel flow by lifting displacement. It plays roles such as controlling the flow and plugging the flow after pouring during continuous casting. The stopper rod needs to be immersed in high-temperature molten steel for a long time, and is extremely easy to age and damage. Once problems occur during use, it will affect the continuous casting production rhythm, and even cause serious safety accidents or huge economic losses.

[0003] The currently used stopper rods are roughly divided into two types: integral stopper rods and composite stopper rods. Among them, the integral stopper rod is usually integrally formed and made of materials such as aluminocarbon, magnesite-carbon or spinel-carbon. The installation and manufacturing processes are relatively simple and the cost is relatively low. However, due to the fixity of its material and structure, it is difficult to meet the requirements of different steel grades and continuous casting process conditions, which limits the application of the integral stopper rod in different production environments. The composite stopper rod consists of a rod body, a rod head and a slag line. Since the positions of each part in the ladle are different, different materials are selected for production, and then each part is compositely assembled to adapt to different production environments.

[0004] In the existing composite stopper rods, the thermal shock resistance or erosion resistance of the rod head or slag line part is relatively poor, so that the stopper rod will crack and chip after being used for a period of time, resulting in the inability to stably control the molten steel flow during continuous casting and affecting production. Summary of the Invention

[0005] In order to solve the deficiencies in the prior art, the present application provides a stopper rod for continuous casting and a preparation method thereof. In the preparation raw materials of the rod head, a composite graphite composed of ultrafine flake graphite, expanded graphite and isostatic graphite is added, which can improve the erosion resistance of the rod head while ensuring the thermal shock resistance; in the preparation raw materials of the slag line, zircon mullite and calcium oxide are added to improve the erosion resistance and thermal shock resistance of the slag line, thereby reducing the occurrence of cracking and chipping of the rod head and slag line.

[0006] In the first aspect, the present application provides a stopper rod for continuous casting, adopting the following technical solution:

[0007] A stopper rod for continuous casting, comprising a rod body, a rod head and a slag line. The rod head is located at one end of the rod body, the slag line is composited on the rod body. The material of the rod body is aluminomagnesia-carbon, the material of the rod head is magnesite-carbon, and the material of the slag line is aluminomagnesia-carbon;

[0008] By weight, the raw materials for preparing the rod body include the following components: 60-65 parts of magnesium aluminate spinel, 3-5 parts of activated α-aluminum oxide powder, 1-2 parts of activated β-aluminum oxide powder, 18-22 parts of flake graphite, 0.2-0.5 parts of nitride, 3-5 parts of antioxidant, and 8-10 parts of binder;

[0009] By weight, the raw materials for preparing the rod head include the following components: 80-85 parts of fused magnesia, 5-10 parts of composite graphite, 0.5-1.2 parts of nitride, and 7-9 parts of binder; The composite graphite includes ultrafine flake graphite, expanded graphite, and isostatic graphite;

[0010] By weight, the raw materials for preparing the slag line include the following components: 55-60 parts of magnesium aluminate spinel, 20-30 parts of corundum, 18-25 parts of ultrafine flake graphite, 5-10 parts of zircon mullite, 1-3 parts of calcium oxide, and 8-10 parts of binder.

[0011] By adopting the above technical solution, the rod body and the slag line are made of aluminum-magnesium-carbon material, and the rod head is made of magnesia-carbon material. The thermal deformation rates of each part are relatively close, avoiding the fracture or chipping of the stopper rod due to excessive differences in thermal deformation rates during use. Composite graphite is added to the raw materials for preparing the rod head. Among them, ultrafine flake graphite has good high-temperature resistance and a layered structure, which helps to improve the structural stability of the rod head; expanded graphite has excellent high-temperature resistance and corrosion resistance, and expanded graphite will expand under high-temperature conditions, filling the tiny gaps between materials and improving the material density of the rod head; isostatic graphite has excellent high-temperature resistance and corrosion resistance, and a low coefficient of thermal expansion, which can improve the thermal stability and corrosion resistance of the rod head. Compared with single-type graphite, the composite graphite compounded by the three can improve the erosion resistance of the rod head while ensuring thermal shock resistance, reducing the occurrence of cracking and chipping of the rod head.

[0012] Since the slag line will be in direct contact with the molten slag and will be affected by the rapid temperature change during continuous casting, it needs to have good corrosion resistance and thermal shock resistance. Adding zircon mullite can improve the overall performance of the slag line. First, zircon mullite has strong erosion resistance, which can improve the erosion resistance of the slag line and extend its service life; second, zircon mullite has a good phase transformation toughening mechanism, improving the high-temperature stability of the slag line and significantly reducing the cracking or fracture problems caused by thermal shock; in addition, zircon mullite can also reduce the thermal expansion coefficient of the slag line, preventing the slag line from deforming severely under high-temperature conditions and causing cracking and chipping. Calcium oxide can enhance the high-temperature stability of zircon mullite, improve the sintering performance of the slag line, enhance the density and uniformity of the material, and help to further improve the corrosion resistance and thermal shock resistance of the slag line.

[0013] Preferably: The addition amount of the composite graphite is 5%-10% of the total amount of the raw materials for preparing the rod head.

[0014] By adopting the above technical solution, since the rod head will directly contact high-temperature molten steel and slag, it is necessary to have good erosion resistance. During the continuous casting process, the rod head will also experience rapid temperature changes, so it is also necessary to have excellent thermal shock resistance. If the addition amount of the composite graphite is too much, although the thermal shock resistance of the rod head will be improved, its erosion resistance will be weakened, resulting in the rod head being eroded and worn by the molten steel, reducing the flow control ability of the stopper rod; while if the addition amount of the composite graphite is too little, although the erosion resistance of the rod head is improved, the thermal shock resistance of the rod head will be weakened, resulting in cracking and chipping during the continuous casting process.

[0015] Furthermore, the addition amount of the composite graphite is 8% of the total amount of the raw materials for preparing the rod head.

[0016] Preferably: the mass ratio of the ultrafine flake graphite, expanded graphite and isostatic graphite is (3 - 6):1:(1 - 4).

[0017] By adopting the above technical solution, further adjusting the mass ratio of the ultrafine flake graphite, expanded graphite and isostatic graphite helps to improve the thermal shock resistance and erosion resistance of the rod head, while controlling the thermal deformation rate of the rod head and reducing the occurrence of cracking and chipping of the rod head.

[0018] In some preferred embodiments, the mass ratio of the ultrafine flake graphite, expanded graphite and isostatic graphite can be 3:1:4, 5:1:2 or 6:1:1, etc.

[0019] Preferably: the antioxidant includes silicon carbide, boron carbide and cobalt oxide.

[0020] By adopting the above technical solution, silicon carbide can form a dense SiO2 protective layer at high temperature, which can effectively block the further penetration of oxygen, and boron carbide will form a B2O3 film on its surface under high temperature conditions to prevent its further oxidation. The two are used together as antioxidants for preparing the rod body. During the high-temperature continuous casting process, a dense, continuous and stable composite protective film can be formed on the surface of the rod body, improving the antioxidant performance of the rod body. The addition of cobalt oxide can promote silicon carbide and boron carbide to form a protective layer on the surface of the rod body more quickly and improve the stability of the protective layer, thereby further improving the antioxidant performance of the rod body and enhancing the erosion resistance of the rod body.

[0021] Preferably: the mass ratio of the silicon carbide, boron carbide and cobalt oxide is (3 - 5):(2 - 4):1.

[0022] By adopting the above technical solution, further adjusting the mass ratio of the silicon carbide, boron carbide and cobalt oxide helps to promote the formation of a more dense, continuous and stable composite protective film on the surface of the rod body, thereby enhancing the erosion resistance of the rod body under high temperature conditions.

[0023] In some preferred embodiments, the mass ratio of silicon carbide, boron carbide and cobalt oxide can be 4:3:1, 3:4:1 or 5:2:1, etc.

[0024] Preferably, the mass ratio of zircon mullite to calcium oxide is (2 - 5):1.

[0025] By adopting the above technical solution, controlling the mass ratio of zircon mullite to calcium oxide within the above range helps to further improve the stability of zircon mullite under high-temperature conditions, thereby improving the erosion resistance and thermal shock resistance of the slag line.

[0026] In some preferred embodiments, the mass ratio of zircon mullite to calcium oxide can be 2:1, 3:1, 4:1 or 5:1, etc.

[0027] Preferably, the nitride is one or more of silicon nitride, boron nitride, titanium nitride, chromium nitride and aluminum nitride.

[0028] By adopting the above technical solution, the above nitrides all have good high-temperature resistance, wear resistance and erosion resistance. Adding nitrides to the raw materials for preparing the stopper rod can significantly improve its erosion resistance and thermal shock resistance.

[0029] In a second aspect, the present application provides a method for preparing a stopper rod for continuous casting, adopting the following technical solution:

[0030] A method for preparing a stopper rod for continuous casting, which comprises the following steps:

[0031] S1. Respectively put the raw materials of the rod body, rod head and slag line into a granulator for granulation, with the particle size ≤ 3 mm, then let it stand and perform drying treatment until the volatile content is within 2%, to obtain rod body mud particles, rod head mud particles and slag line mud particles;

[0032] S2. Load the rod body mud particles, rod head mud particles and slag line mud particles into a mold, and perform isostatic pressing at 80 - 100 MPa for 6 - 10 min to obtain a stopper rod blank;

[0033] S3. Place the stopper rod blank under the condition of 200 - 230 °C and dry for 12 - 16 h to obtain a rough stopper rod;

[0034] S4. Sinter the rough stopper rod under the condition of 920 - 960 °C to obtain a semi-finished stopper rod;

[0035] S5. Perform shape processing and coating with high-temperature resistant coating on the semi-finished stopper rod to obtain a finished stopper rod.

[0036] By adopting the above technical solution, the preparation of the stopper rod can be completed using existing production equipment without customizing special instruments. Moreover, the stopper rod prepared by the above method has good erosion resistance, thermal shock resistance, and scouring resistance, with reduced cracking and chipping phenomena, and a longer service life compared to the stopper rods on the market.

[0037] In summary, this application includes at least one of the following beneficial technical effects:

[0038] 1. In this application, the rod body and the slag line are made of alumina-magnesia-carbon, and the rod head is made of magnesia-carbon. The main materials of each part are relatively similar, and the thermal deformation rates are relatively close, avoiding the fracture or chipping of the stopper rod due to excessive differences in thermal deformation rates during use.

[0039] 2. In this application, a composite graphite composed of ultrafine flake graphite, expanded graphite, and isostatic graphite is added to the raw materials for preparing the rod head, which can improve the scouring resistance of the rod head while ensuring thermal shock resistance and extend the service life of the rod head.

[0040] 3. In this application, zircon mullite is added to the raw materials for preparing the slag line, which not only improves the erosion resistance and thermal shock resistance of the slag line but also has a low thermal expansion coefficient and has little influence on the thermal deformation rate of the slag line. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic structural diagram of the stopper rod in Embodiment 1 of this application;

[0042] In the figure, 1. Rod body; 2. Rod head; 3. Slag line. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] To make this application easier to understand, the following will further elaborate on this application in combination with embodiments. These embodiments are only illustrative and not limited to the application scope of this application. The raw materials or components used in this application can be obtained through commercial channels or conventional methods without special instructions.

[0044] Source of raw materials:

[0045] Magnesium aluminate spinel, with CAS number 12068-51-8 and product number JR135c, purchased from Henan Jinrun New Materials Co., Ltd.;

[0046] Active α-aluminum oxide powder, with an effective ingredient content of 90% and a particle size of 3 - 5 μm;

[0047] Active β-aluminum oxide powder, with an effective ingredient content of 99.8%;

[0048] Flake graphite, with a carbon content of 98%, a specification of 200 mesh, a moisture content ≤ 0.5%, and a grade of first-class;

[0049] Fused magnesia, product number KB-PN-98.5, purchased from Weifang Kaibo Magnesium Salt Co., Ltd.;

[0050] Ultra-fine flake graphite, with a moisture content of ≤0.1%, a purity of 98%, and a specification of 2000 mesh;

[0051] Expanded graphite, with a moisture content of 0.2 - 1.5%, product number P-X, purchased from Shanghai Youmo Composite Materials Co., Ltd.;

[0052] Isostatic graphite, with a fixed carbon content of 99.99%, a specification of 1000 mesh, and a model of LG-0202, purchased from Henan Wanying Refractory Materials Technology Co., Ltd.;

[0053] Corundum, product number DYGQ-80, purchased from Zhengzhou Dongyang Refractory Materials Co., Ltd.;

[0054] Zircon mullite, grade M75, purchased from Henan Fengkai Refractory Materials Co., Ltd.;

[0055] The binder is phenolic resin, with an effective ingredient content of 80 - 90%, purchased from Yangzhou Taiwo Energy Technology Co., Ltd.

[0056] Examples 1 - 3:

[0057] Refer to Figure 1 , in Examples 1 - 3, the stopper rod includes a rod body 1, a rod head 2, and a slag line 3. The rod head 2 is located at one end of the rod body 1, and the slag line 3 is compounded on the side wall of the rod body 1. Among them, the materials of the rod body 1 and the slag line 3 are aluminum-magnesium-carbon, and the material of the rod head 2 is magnesium-carbon. The raw materials and their dosages for preparing the rod body 1, the rod head 2, and the slag line 3 are shown in Tables 1 - 3 respectively.

[0058] The preparation method of the stopper rod is as follows: S1. Put the raw materials of the rod body, the rod head, and the slag line into a mixing and granulating machine respectively for granulation to make particles with a particle size of ≤3 mm, and then let them stand and be dried until the volatile content is within 2% to obtain rod body mud particles, rod head mud particles, and slag line mud particles; S2. Load the rod body mud particles, rod head mud particles, and slag line mud particles into a mold and isostatically press them at 80 MPa for 8 minutes to obtain a stopper rod blank; S3. Place the stopper rod blank at 220°C for 16 hours of drying to obtain a rough stopper rod; S4. Sinter the rough stopper rod at 960°C under high temperature to obtain a semi-finished stopper rod; S5. Perform shape processing and coating with high-temperature resistant paint on the semi-finished stopper rod to obtain a finished stopper rod.

[0059]

[0060]

[0061] Example 4:

[0062] The difference between Example 4 and Example 1 lies in the different doping amounts of silicon carbide, boron carbide, and cobalt oxide in the antioxidant. In Example 4, the doping amount of silicon carbide is 1.5 kg, the doping amount of boron carbide is 2 kg, and the doping amount of cobalt oxide is 0.5 kg. That is to say, the mass ratio of silicon carbide, boron carbide, and cobalt oxide is 3:4:1, and the rest is the same as in Example 1. Example 5:

[0063] The difference between Example 5 and Example 1 lies in the different doping amounts of silicon carbide, boron carbide, and cobalt oxide in the antioxidant. In Example 5, the doping amount of silicon carbide is 2.5 kg, the doping amount of boron carbide is 1 kg, and the doping amount of cobalt oxide is 0.5 kg. That is to say, the mass ratio of silicon carbide, boron carbide, and cobalt oxide is 5:2:1, and the rest is the same as in Example 1. Example 6:

[0064] The difference between Example 6 and Example 1 lies in the different doping amounts of ultrafine flake graphite, expanded graphite, and isostatic graphite in the composite graphite. In Example 6, the doping amount of ultrafine flake graphite is 3 kg, the doping amount of expanded graphite is 1 kg, and the doping amount of isostatic graphite is 4 kg, and the rest is the same as in Example 1. Example 7:

[0065] The difference between Example 7 and Example 1 lies in the different doping amounts of ultrafine flake graphite, expanded graphite, and isostatic graphite in the composite graphite. In Example 7, the doping amount of ultrafine flake graphite is 6 kg, the doping amount of expanded graphite is 1 kg, and the doping amount of isostatic graphite is 1 kg, and the rest is the same as in Example 1. Example 8:

[0066] The difference between Example 8 and Example 1 lies in the different doping amounts of zirconium mordenite and calcium oxide. In Example 8, the doping amount of zirconium mordenite is 6.7 kg, and the doping amount of calcium oxide is 3.3 kg, and the rest is the same as in Example 1. Example 9:

[0067] The difference between Example 9 and Example 1 lies in the different doping amounts of zirconium mordenite and calcium oxide. In Example 9, the doping amount of zirconium mordenite is 7.5 kg, and the doping amount of calcium oxide is 2.5 kg, and the rest is the same as in Example 1.

[0068] Example 10:

[0069] The difference between Example 10 and Example 1 lies in the different doping amounts of zirconium mordenite and calcium oxide. In Example 10, the doping amount of zirconium mordenite is 8.3 kg, and the doping amount of calcium oxide is 1.7 kg, and the rest is the same as in Example 1.

[0070] Comparative Example 1:

[0071] The difference between Comparative Example 1 and Example 1 lies in the different total doping amounts of composite graphite. The total doping amount of composite graphite in Comparative Example 1 is 4 kg, among which the doping amount of ultrafine flake graphite is 2.5 kg, the doping amount of expanded graphite is 0.5 kg, and the doping amount of isostatic pressing graphite is 1 kg. The rest is the same as in Example 1.

[0072] Comparative Example 2:

[0073] The difference between Comparative Example 2 and Example 1 lies in the different total doping amounts of composite graphite. The total doping amount of composite graphite in Comparative Example 2 is 16 kg, among which the doping amount of ultrafine flake graphite is 10 kg, the doping amount of expanded graphite is 2 kg, and the doping amount of isostatic pressing graphite is 4 kg. The rest is the same as in Example 1.

[0074] Comparative Example 3:

[0075] The difference between Comparative Example 3 and Example 1 lies in that ultrafine flake graphite is used to replace composite graphite in equal amount. The rest is the same as in Example 1.

[0076] Comparative Example 4:

[0077] The difference between Comparative Example 4 and Example 1 lies in that zircon mullite is not added to the preparation raw materials of the slag line. The rest is the same as in Example 1.

[0078] Test Example:

[0079] The performance of the stopper rods prepared in Examples 1 - 10 and Comparative Examples 1 - 4 was detected, specifically including thermal shock resistance, apparent porosity, erosion depth, and service life. Among them, the detection of thermal shock resistance was carried out according to Method 1 (water quenching method) in GB / T 30873 - 2014 "Refractory materials - Test method for thermal shock resistance", the detection of apparent porosity was carried out according to GB / T 2997 - 2015 "Test methods for bulk density, apparent porosity and true porosity of dense shaped refractory products", the erosion depth was measured as the maximum depth of corrosion on the surface of the stopper rod after continuously immersing the stopper rod in molten steel for 48 h, and the service life was calculated based on the continuous use until leakage of molten steel occurred after the stopper rod blocked the nozzle. The specific detection results are shown in Table 4.

[0080]

[0081] It can be seen from the detection results in Table 4 that the overall performance of the stopper rods prepared in Examples 1 - 10 is better than that of the stopper rods prepared in Comparative Examples 1 - 4. The stopper rods prepared in Examples 1 - 10 have good thermal shock resistance, smaller erosion depth after continuously soaking in molten steel for 48 h, and longer service life.

[0082] From the test results of Examples 1-5, it can be seen that the overall performance of the stopper rod prepared by referring to the raw materials and their dosages of the rod body, rod head and slag line in Example 1 is better, with excellent thermal shock resistance and erosion resistance. Among the antioxidants, when the mass ratio of silicon carbide, boron carbide and cobalt oxide is 4:3:1, the overall performance of the stopper rod is improved.

[0083] From the test results of Examples 1, 6-7 and Comparative Examples 1-3, it can be seen that during the preparation of the rod head, when the addition amount of graphite is controlled within 5%-10%, the overall performance of the stopper rod is better and the service life is longer. Moreover, after the inventor adjusted the type of graphite, it was found that compared with single-type graphite, the composite graphite composed of ultrafine flake graphite, expanded graphite and isostatic pressing graphite added to the stopper rod can significantly improve the overall performance of the stopper rod. Especially when the mass ratio of ultrafine flake graphite, expanded graphite and isostatic pressing graphite is 5:1:2, the performance improvement of the stopper rod is more obvious.

[0084] From the test results of Examples 1, 8-10 and Comparative Example 4, it can be seen that adding zircon mullite to the preparation of the slag line can improve the erosion resistance and thermal shock resistance of the slag line, extend the service life of the stopper rod, and the addition of calcium oxide can assist zircon mullite in improving the performance of the stopper rod. When the mass ratio of zircon mullite and calcium oxide is (2-5):1, the overall performance of the stopper rod is improved.

[0085] It should be noted that the above-described embodiments are only used to explain the present application and do not constitute any limitation to the present application. The present application has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. Modifications can be made to the present application within the scope of the claims of the present application as stipulated, and the present invention can be revised without departing from the scope and spirit of the present application. Although the present application described therein relates to specific methods, materials and embodiments, it does not mean that the present application is limited to the specific examples disclosed therein. On the contrary, the present application can be extended to all other methods and applications with the same functions.

Claims

1. A stopper for continuous casting, comprising a rod body (1), a rod head (2) and a slag line (3), wherein the rod head (2) is located at one end of the rod body (1), and the slag line (3) is compounded on the rod body (1), and is characterized in that: The material of the rod body is aluminum-magnesium-carbon, the material of the rod head is magnesia-carbon, and the material of the slag line is aluminum-magnesium-carbon; By weight, the preparation raw materials of the rod body include the following components: 60-65 parts of magnesia-aluminum spinel, 3-5 parts of active α-aluminum oxide powder, 1-2 parts of active β-aluminum oxide powder, 18-22 parts of flake graphite, 0.2-0.5 parts of nitride, 3-5 parts of antioxidant, and 8-10 parts of binder; By weight, the preparation raw materials of the rod head include the following components: 80-85 parts of fused magnesia, 5-10 parts of composite graphite, 0.5-1.2 parts of nitride, and 7-9 parts of binder; The composite graphite includes ultrafine flake graphite, expanded graphite, and isostatic graphite; By weight, the preparation raw materials of the slag line include the following components: 55-60 parts of magnesia-aluminum spinel, 20-30 parts of corundum, 18-25 parts of ultrafine flake graphite, 5-10 parts of zircon mullite, 1-3 parts of calcium oxide, and 8-10 parts of binder; The antioxidant includes silicon carbide, boron carbide, and cobalt oxide, and the mass ratio of silicon carbide, boron carbide, and cobalt oxide is (3-5):(2-4):1; The addition amount of the composite graphite is 5%-10% of the total amount of the preparation raw materials of the rod head; The mass ratio of the ultrafine flake graphite, expanded graphite, and isostatic graphite is (3-6):1:(1-4); The mass ratio of the zircon mullite and calcium oxide is (2-5):

1.

2. The stopper for continuous casting according to claim 1, characterized in that: The nitride is one or more of silicon nitride, boron nitride, titanium nitride, chromium nitride, and aluminum nitride.

3. A method for preparing a stopper rod as claimed in claim 1 or 2, characterized in that: The preparation method includes the following steps: S1. Respectively put the raw materials of the rod body, rod head, and slag line into a granulator for granulation, the particle size ≤ 3mm, then let it stand and dry until the volatile content is within 2% to obtain rod body mud particles, rod head mud particles, and slag line mud particles; S2. Load the rod body mud particles, rod head mud particles, and slag line mud particles into a mold and isostatically press them at 80-100 MPa for 6-10 min to obtain a stopper blank; S3. Place the stopper blank at 200-230 °C and dry it for 12-16 h to obtain a rough stopper; S4. Sinter the rough stopper at 920-960 °C to obtain a semi-finished stopper; S5. Perform shape processing and coating with a high-temperature resistant coating on the semi-finished stopper to obtain a finished stopper.

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