Cui Dongyue Zhang Zuo
Abstract: This article describes the R&D process, technical difficulties, and the technical route to replace imported graphite rotors used to replace imported graphite rotors, as well as several technical innovations that have been completed around this alternative goal. The product has been approved by more than 30 domestic companies, with an annual sales of about 500. The main aluminum processing enterprises in the country believe that the product meets the requirements for the use of liquid aluminum purification technology and the product lifespan has exceeded or exceeded the import level. This product was declared a national patent in 1998 and a patent certificate was obtained in February 2000.
The graphite rotor serves as the key component of the on-line degassing device of the aluminum melt, and its stable operation enables the purification of the aluminum melt outside the furnace to be achieved, which ensures the continuity of the aluminum melt purification and the stability of the product quality. Since the introduction of this technology, its advanced purification process and good purification effect have been widely used in the production of aluminum processing enterprises at home and abroad. Beijing Huatai Changyun Electronics Co., Ltd.'s main project is this graphite rotor.
1 The starting point of technological innovation
In the 1980s, China introduced the Jumbo 3C caster from France and randomly imported graphite rotors. The average service life of imported rotors is 30 to 40 days, and the price of each of the rotors is more than 8,000 yuan. Although the domestic graphite rotor 3000 ~ 4000 yuan / root, but the longest life of only 10 days.
Our goal of technological innovation is to replace imports and produce graphite rotors that domestic companies are happy to accept. The research includes the structure, mechanical properties, thermal properties, chemical properties, and conductive properties.
In our opinion, imported graphite and domestic graphite are different in terms of equipment, process and parameters, resulting in a certain difference in their properties, mainly the four kinds of flexural strength, gas permeability, oxidation resistance and anti-wear properties. At the same time, the impact The service life of the entire rotor is also partial damage, that is, local damage caused by the above-mentioned four kinds of weak performance. For example, the flexural strength of the inlet rotor is about 25mpa, and the flexural strength of the domestic electrode graphite rotor is about 10mpa. However, in our research, we found that the easily-folded parts of domestic rotors are often stress-concentrated. As long as the stress-concentrated parts are strengthened, the entire rotor may not be easily broken. Preliminary tests in our laboratory have shown that imported graphite is approximately 5 times more resistant to oxidation than ordinary electrode graphite (domestic). However, in use, the oxidation occurs only above the liquid surface, and when the furnace seal is not very poor, even if the oxidation above the liquid surface is not too severe, this problem can be solved by simple treatment. When the imported graphite rotor is used in the purification furnace, its wear resistance is about 2-3 times stronger than that of the domestic electrode graphite rotor, but the wear occurs mainly at the liquid surface position, as long as measures can be taken to solve the problem by taking measures at the surface 15cm above the liquid surface. Gas permeability is also a similar situation.
In short, from a practical point of view, as long as the above-mentioned four properties of domestic graphite rotors are treated locally by technical means, they can exceed the imported graphite rotors in terms of service life. What's more, the production lines of many companies have their specific characteristics, which not only affect the main reasons for the life of their graphite rotors, but are often just one of the four properties of flexural strength, wear resistance, oxidation resistance, and gas permeability. Technical improvements can significantly increase their useful life. This kind of adaptive technological innovation is actually the formation of several patented technologies that are proprietary to our company during the process of replacing imported materials.
2 related technical issues
We do not completely convert homemade graphite into imported graphite from the microstructure of graphite, but only improve the weaknesses of the domestic electrode graphite rotor. This obviously reduces processing costs and increases technical feasibility. However, there are still many technical difficulties in the specific practice. First of all, the cost must be accounted for, and performance must not be increased. The cost will also be increased by a large margin, making the enterprise unacceptable. Second, the technology to be used and the materials selected cannot contaminate the aluminum liquid. Furthermore, one performance cannot be improved but other performance indicators are reduced. Finally, the installation of the graphite rotor is limited, the size of the graphite rotor shaft cannot be changed at will, and thermal expansion can not be ignored.
After many years of groping and summarizing, we believe that, at least until now, the use of the following special technologies can make the life of domestically produced electrode graphite rotors catch up even more than that of imported rotors. Below we briefly describe four proprietary technologies.
2.1 Produce locally reinforced products that have many times higher mechanical strength than graphite materials. To improve the strength and quality of the graphite rotor's frangible parts, the key to this technology is to strengthen the thermal expansion effect of the products and the graphite materials are similar. The force of the two can be transferred well and the cost is not too high. And do not pollute the liquid aluminum.
2.2 The parts with good air tightness, oxidation resistance and high temperature resistance should be used in the easily oxidized parts. The component should be well integrated with the graphite matrix and it should be intact throughout the entire operation of the graphite rotor.
2.3 Inorganic non-metallic materials that meet the performance requirements are selected to produce higher-strength, higher-hardness, gas-tight components that are used in places with poor operating conditions. For example, the surface of the liquid surface that is oxidized and has a large amount of wear.
2.4 According to functional requirements, a few special features are formed. It can meet the high gas permeability requirements of some companies. We can even make basic gas-impermeable products in locations where the oxidizing environment is particularly bad.
The rational use of the above four proprietary technologies will enable them to complement each other and form an integral whole with the graphite matrix. This is very particular about the process. Because the technological parameters of the four proprietary technologies are not the same, sometimes they also restrict each other and cause troubles. We have worked out some laws to form a set of processing methods to ensure that the overall performance of graphite rotors meets the target of imported products.
For different companies, we must study the process conditions and rotors should meet the requirements and design a different approach. In order to ensure the quality, the company implements tracking management for each batch of products, numbering each rotor shaft and placing the number on the product. At the same time, the processing methods, production personnel, and production date are registered. Therefore, our products have individualized characteristics that permeate the efforts of technical personnel, management personnel, and production personnel. Some people call it the “heartbeat axisâ€.
A certain type of "Huatai Changyun" brand graphite rotor is shown in Figure 1.
The company website is: The website has more text and pictures.
After being used by a number of domestic companies, the products worked well. At the end of 1998, they applied for patents. In February 2000, they received a patent certificate from the National Patent Office. The patent number is 98249271-5. The project name is "Graphite Rotor Shaft for Purifiers."
This article only elaborates the technical problems of the project from the perspective of development ideas and technical routes. It does not specify the specific technical issues such as production methods, process parameters, materials used, and equipment. This is because proprietary technologies and patented technologies involve the company’s intellectual property rights, and readers are also forgiven for understanding.
3 Product use effect
The “Huatai Changyun†brand graphite rotor was trialed in North China Aluminum Co., Ltd. in 1997. In 2001, it was recognized by North China Aluminum Industry Co., Ltd. as the Class A supplier of the graphite rotor of the plant. The average service life is more than 45 days and the maximum service life is up to 116 days. Both of these indicators exceed the level of imported graphite rotors.
At the end of 2001, Bohai Aluminum Co., Ltd. began to use our supplied graphite rotor. Wang Xuhua, the technical director of the company's melting and casting branch, wrote an article “Development and Application of High-life Graphite Rotors†in 2004 and was published in the 32nd issue of “Light Alloy Processing Technology†magazine. The article said: “At the beginning of 2001, a graphite rotor with a special material protection cover and coating was successfully developed by Beijing Huatai Changyun Electronics Co., Ltd. This rotor has attracted the attention of many aluminum smelting casting manufacturers once the market has been asked. From December 21, 2001 to March 1, 2002, the company's casting plant first tested the graphite rotor produced by Beijing Huatai Changyun Electronics Co., Ltd. on the 1# casting and rolling line, and its service life was 69 days. Over the years, it has been proved by practice that the continuous service life of this new rotor is an average of 72 days, which is more than twice the life of imported rotors."
Southwest Alcoa (Group) Co., Ltd. Foundry Co., Ltd. Ding Daqiang, Ma Guojun, Tang Jian and Li Chengli co-authored an article entitled “Evaluation of the Use of Graphite Rotors for Online Degassing Devicesâ€, published in the 13th National Light Alloy Processing Academy. Conference Proceedings. The article said: "After analyzing and comparing the service life and price of the same graphite rotor produced by four manufacturers, the life and price gaps of graphite rotors produced by different manufacturers are relatively large. Among them, the life of graphite rotors of Beijing Huatai Changyun Electronics Co., Ltd. It has an average of 150 melting cycles and the longest lifespan, which is far more than the other two domestic and imported rotors. Its unique production process is an important guarantee for a long life, and the price is the lowest. It should have a wide market prospect."
At present, apart from the major aluminum processing companies in China, such as North China Aluminum Co., Ltd., Bohai Aluminum Co., Ltd., Southwest Aluminum (Group) Co., Ltd., and Harbin Dongshan Casting & Rolling Co., Ltd. It has been approved by more than 40 domestic companies. The annual sales volume is about 900, and the market share is the best in domestic similar products. Its service life basically catches up with even the level of imported graphite rotors, and the price is only one third of the imported products.
The “Huatai Changyun†brand graphite rotor is cost-effective and helps customers reduce the ton cost of aluminum processing.
Although the service life of our products is more than three times that of domestic similar products, there are still some gaps between individual performance and imported products. This situation mainly occurs in new customers of our company. The reason is that the communication between us and new customers has not been fully completed. The use environment of the company has not yet been in touch with the main factors affecting the service life, or our design solutions, process parameters and equipment improvements have not yet been adjusted. This means that the product is in the process of running-in and improvement.
Our goal is to fully surpass the imported graphite rotor in its service life.
By the way, using four proprietary technologies of Beijing Huatai Changyun Electronics Co., Ltd., we are sure to improve the quality of the consumables used in any metal solution and extend its service life. If the furnace temperature does not exceed 1000 degrees, the effect is better.
4 Conclusion
Beijing Huatai Changyun Electronics Co., Ltd. must adhere to the road of technological innovation, further improve the technological level of the graphite rotor, help customers reduce the tons of aluminum processing costs, provide customers with better products and services.
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