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Rare earth has broad prospects in the application of steel coatings

Posted by: steel world 2021-10-15 Comments Off on Rare earth has broad prospects in the application of steel coatings

        “The application prospect of rare earth in steel and metal product coatings is very broad, and the potential market is extremely huge. We should speed up research and development, promote the application, and apply rare earth alloy coating technology to steel pipes, steel plates and special-shaped steel.” In an interview with Thai Rare Earth New Materials Co., Ltd., the chairman Liu Jilu and the chief engineer and professor-level senior engineer Shi Zhimin expressed their views.
        Ma’anshan Dingtai Rare Earth New Materials Co., Ltd. is a high-tech enterprise specializing in the research and development and production of rare earth alloy coating technology and products. It has successively developed and manufactured rare earth multi-element alloy coatings with independent intellectual property rights and rare earth zinc-aluminum alloy coating steel strands. Process and technology are widely used in electric power, telecommunications, electrified railway and other construction projects.
        According to experts here, rare earth elements have a unique 4f electronic layer structure, large atomic magnetic distance, strong spin-orbit coupling and other characteristics. When forming rare earth complexes with other elements, the coordination number can be 3-12 The crystal structure of rare earth compounds is also diversified. The unique physical and chemical properties of rare earth elements show excellent mechanical properties when forming intermetallic compounds and alloy materials with non-ferrous metals, which determines their extremely wide range of uses. Rare earths are widely used in traditional industries such as steel, iron, non-ferrous metals, machinery manufacturing, petrochemicals, and other traditional industries. Rare earth non-ferrous alloy materials are a new generation of materials that are focused on development in the contemporary aviation, aerospace, military and automotive industries.
        Judging from the development history of hot-dip galvanizing technology worldwide, the hot-dip coating is developing towards alloy coating and special coating technology. In order to improve the service life of traditional steel materials and products, the International Lead and Zinc Research Organization and Bethlehem Steel Corporation of the United States have successively developed Galfan, Galvalume and other new zinc and aluminum alloy anticorrosive coatings since the mid to late 1980s. Product standards are produced and widely used. In China, the level of anti-corrosion coating technology for steel materials and products is relatively backward, accounting for more than 90% of the national total is still traditional galvanized coatings. The output of zinc-aluminum alloy coated steel products is very small, and the product quality is also unstable. There is still a gap in capability compared with similar international products.
        Before the industrialization of rare earth multi-element alloy coating products, the development and application of the above-mentioned coatings in the relevant technical fields of our country are basically in a state of tracking research. Because Galvalume and Galfan coatings have better atmospheric corrosion resistance than ordinary galvanized coatings, their performance in soil and marine environments is not satisfactory. Therefore, the development of low-cost, cost-effective hot-dip alloy coating is not only a development direction of hot-dip coating technology, but also has very important practical significance.
        For this reason, Maanshan Dingtai Rare Earth New Material Co., Ltd. developed a new type of anti-corrosion coating material-rare earth multi-element alloy coating material and process technology for the first time in China, which overcomes the production equipment of similar foreign products by gas reduction method (ie Sendzimir). A series of defects such as complexity, expensive manufacturing cost, and very demanding raw material requirements, and can be achieved by the domestic common “solvent method” process method. The products produced have high corrosion resistance, and have a series of good comprehensive properties such as excellent formability and weldability. They make full use of China’s rich rare earth resources and are easy to promote.
        After that, they started to develop the coating technology and coating technology of rare earth multi-element alloy I (rare earth-zinc-aluminum-magnesium RE+Zn+Al+Mg), rare earth multi-element alloy II (rare earth-zinc-aluminum-magnesium-boron-chromium-titanium REZnAlMgBCrTi) and product. Rare earth multi-element alloy I has excellent corrosion resistance and good electrochemical protection ability. The improvement of the comprehensive corrosion resistance of the coating enables the rare earth alloy coated steel products to maintain good corrosion resistance stability under various harsh environments, thereby effectively inhibiting the corrosion and destruction speed of the steel products.
        The rare earth multi-element II (rare earth-zinc-aluminum-magnesium-boron-chromium-titanium) coating technology and products included in the National 863 Program are based on the use of rare earth, zinc, aluminum and other metals to improve the fluidity of the plating solution, and make the coating brighter in color. , Good smoothness, strong bonding force, stable quality; at the same time, it uses trace elements such as RE, Mg, Ti, B, Cr to inhibit the characteristics of grain boundary or intergranular corrosion to improve the ability of the coating to resist local corrosion. The surface of the coating is enriched The composite film formed by the anti-corrosion phase structure of rare earth oxides, aluminum-magnesium oxides, etc. can effectively isolate the matrix and the corrosive medium, thereby slowing down the progress of the electrochemical reaction and greatly improving the corrosion resistance of the coating.
        In various environments and corrosive media, the corrosion rate of the coating is reduced by more than 25% than the current corrosion-resistant zinc-aluminum alloy coating materials in the world, the manufacturing cost of the product is reduced by more than 20%, and the corrosion resistance and service life of the product It is more than 3 times that of ordinary galvanized anti-corrosion layer. This technology is easy to popularize, and is especially suitable for the actual equipment technology level of the steel material anti-corrosion processing industry in China at this stage.
        According to experts, domestic rare-earth zinc-aluminum alloy coatings, rare-earth multi-element alloy-coated steel wire and steel strand products, and rare-earth zinc-aluminum alloy coating functional materials have good corrosion resistance and comprehensive technical performance. Industrial tests and inspections by the national technical authority have proved that the technical performance indicators of related products are significantly higher than the technical requirements of current national standards for galvanized products. The important performance indicators of the product have exceeded the relevant product standards of the International Electrotechnical Commission IEC, ASTM and other related products. The application of national key projects in the past few years can prove that as a new type of rare earth functional material, the rare earth multi-element alloy coating can completely exceed the internationally used Galfan alloy coating for the anti-corrosion processing and manufacturing of various steel products.
        The surface quality of the plated parts made of this material is excellent, which can meet the requirements of various steel structure products and overhead conductors and ground wires for high-voltage and ultra-high-voltage transmission lines, power towers, lightning protection grounding wires, and grounding grid products that are resistant to salt spray and soil corrosion. As required, the industrialized production of the REZnAlMgBCrTi alloy coating functional material has been realized. Researched and developed a rare earth multi-element (REZnAlMgBCrTi) alloy coating functional material with an international advanced level. The corrosion resistance and service life of the products are 2-3 times that of ordinary galvanized anti-corrosion coatings.
        Compared with ordinary galvanized steel wire, the rare earth zinc-aluminum alloy coated steel wire and rare earth multi-alloy coated steel wire steel wire products have the following remarkable features:
1. Product appearance: the surface of the rare earth alloy coated steel wire steel wire is smooth and bright, and has certain characteristics. Decorative appearance.
2. Coating weight: This product overcomes the weakness of ordinary zinc-aluminum alloy coating thickness, and its alloy coating weight is higher than the technical requirements of the national standard for galvanized steel wire products, and fully guarantees the service life of the product.
3. Coating adhesion: the rare earth alloy coating has good adhesion to the diamond core, and the coating adhesion self-winding test will not crack.
4. Corrosion resistance: strong corrosion resistance. According to user requirements, the product can be subjected to neutral salt spray (NSS) test and sulfur dioxide (SO2) test. The corrosion resistance is 1-2 times higher than that of hot-dip galvanized steel wire.
5. Copper sulphate test: The number of copper sulphate resistance tests of steel wire is higher than the technical requirements of the national standard for galvanized steel wire.
6. Resistivity of steel wire: meets the electrical resistivity requirements of the International Electrotechnical Commission (IEC) standard for steel core steel wire, which is better than the current national standard.
7. Compatibility with aluminum conductor: good material matching. Because the steel wire substrate is coated with continuous and dense rare earth alloy coating material, it can reduce the galvanic corrosion between the steel core steel wire and the rare earth aluminum wire and the aluminum wire, and extend The service life of steel core aluminum wire.
8. Product cost-effectiveness: This product has a higher quality-performance-price ratio, which can be compared (that is, slightly higher) to the price of hot-dip galvanized products to provide users with high-quality products.
        Experts pointed out that although China has developed a new generation of rare earth alloy coating technology and materials, which are used in a number of key domestic power construction projects, due to limited output, it is far from being able to meet the needs of the domestic market. It is reported that the patent right of Zn-5%Al-Mischmetal alloy coating (GALFAN®) successfully developed abroad in the 1980s belongs to the International Lead and Zinc Organization (ILZRO). Since 1983, Zn-5%Al-Mischmetal Alloy-coated steel products (including plates, wires, and pipes) began to be officially commercialized. So far, the Zn-5%Al-mixed rare earth alloy coating has been patented in more than 30 countries in the world, and 60 production lines around the world have purchased the Zn-5%Al-mixed rare earth alloy coating (GALFAN®) production patent from (ILZRO) License, the right to produce Zn-5%Al-mixed rare earth alloy coating (GALFAN®) plates, wires, and pipes.
        In 1996, a domestic factory imported a full set of galvanized steel wire equipment with an annual output of 20,000 tons from abroad for a huge amount of foreign exchange, and purchased the Galfan patent. However, due to various reasons of cost and technology, the production line has not been able to reach the standard for a long time. Production is put into operation. A few years ago, a company also purchased a full set of imported GALFAN® steel wire equipment, and some companies made equipment for GALFAN® steel wire production. A smelter purchased patents for the production of GALFAN® alloy ingots in the 1990s, but due to various For complicated reasons, GALFAN® steel wire has not been widely promoted in China.
        The reason is that in addition to many factors such as the technical level of galvanized steel wire, the manufacturing cost of equipment and products, the product quality, and the recognition and recognition of the Chinese market, one of the important reasons is the foreign galvanized galvanized steel wire. Steel wires and steel strands are not compatible with the actual productivity level and technological equipment capabilities of China’s metal products industry, so GALFAN®-plated steel wires and steel strands in China have not yet become mainstream products in the market.
        Industry experts believe that the new generation of rare earth alloy coating materials and technologies have a very broad application prospects on steel. The current application fields only involve the power industry, mainly rare earth alloy coated steel wire and steel stranded wire, overhead conductors and ground wires used in high-voltage and ultra-high-voltage transmission lines, power tower steel structures, lightning protection grounding wires and grounding nets, cable trays In this field alone, China’s annual demand for steel wire and steel stranded wire reaches 1 million tons. However, the annual output of rare earth alloy coatings is only tens of thousands of tons, which obviously cannot meet the demand of the domestic market. And if this high-tech is applied to pipes, profiles and plates, and the development of rare earth alloy coated steel pipes, rare earth alloy coated section steels, and rare earth alloy coated plates, the huge market can be imagined.
        At present, most of our country’s products are still on galvanized steel pipes, galvanized sheets and galvanized profiles. Rare earth alloy coating technology is basically not used. Therefore, galvanized steel and metal products have poor corrosion resistance, high pollution and short service life. , Inconsistent with the national policy of energy saving and emission reduction.
        Industry insiders proposed that the application of rare-earth alloy coating technology on steel pipes, steel plates and special-shaped steels in China is fully qualified. Because our country has abundant rare earth resources. Back then, it was said, “There is oil in the Middle East, and China has rare earths.” “We must do a good job in rare earth matters and give full play to the advantages of China’s rare earths.” China’s rare earth resources rank first in the world. The world has discovered 154 million tons of exploitable rare earth mineral reserves (REO), of which 89 million tons (REO) are in China, accounting for nearly 58% of the global reserves. A relatively complete production system has been formed from mining, selection, smelting, separation to analysis and testing. It has been able to produce more than 100 varieties and more than 200 specifications of rare earth products. In the past 20 years, China’s rare earth smelting and separation industry has developed rapidly. Its variety, output, export volume and consumption have all ranked first in the world, and it has a pivotal position in the world. It can be seen that China’s rich rare earth resources have laid the foundation for the development of rare earth alloy coating products on steel.
        If the rare earth alloy coating technology is applied to steel pipes, steel plates, steel strips and profiles, its market potential is huge. It is reported that Ma’anshan Dingtai Rare Earth New Materials Co., Ltd. has extended the focus of its next R&D work to this broader field, and developed new types of rare earth alloys by developing rare earth alloy-coated tubes, plates, strips and profiles. Special-shaped steel such as coated steel, steel pipe and groove angle.

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