Low-temperature seamless steel pipes are mainly used in the production of ethylene, propylene, urea, synthetic ammonia, compound fertilizers, and other process equipment such as washing, purification, desulfurization, and degreasing in the pharmaceutical industry, as well as cryogenic equipment manufacturing, ultra-low temperature cold storage, and ultra-low temperature liquefaction. Gas pipelines and their pipe components, such as petroleum gas cryogenic separation equipment, air separation equipment, etc. There are two main types of low-temperature seamless steel pipe materials: austenitic and ferrite. The difference in crystal structure determines that the austenitic cryogenic pipe has no brittle transition temperature in the low temperature range. Generally, it is not necessary to verify its low-temperature impact toughness. It is used, but GB150-2011 stipulates that when the operating temperature is not lower than -196℃ (low temperature range), the impact test can be exempted. When the operating temperature is between -196～-253℃ (ultra-low temperature range), it should be implemented in accordance with the design documents. The ferrite-type cryogenic tube has an obvious low-temperature brittle transition temperature, and has its applicable low-temperature range. Although the temperature limits of low temperature steel are slightly different in the world, for example, the temperature limits defined by the United Kingdom, Germany/Japan, China, and the United States/Russia are 0, -10, -20, and -30°C, but the actual industrial environment can be lower To -253 ℃ (liquid hydrogen) more than.
The continuous expansion of low-temperature realization technology and the continuous demand of industrial development have continuously promoted the research and development of ferritic low-temperature steels used in lower ambient temperatures. In addition, some researchers start to optimize the performance of existing steel grades, such as microalloying A333Gr.6 seamless steel pipes and upgrading them from carbon steel systems to low alloy steel systems; or the heat treatment process Optimization can improve low temperature performance to varying degrees. Furthermore, in general, ferritic low-temperature steel has a price advantage than austenitic low-temperature steel, which has also prompted it to become a research hotspot.
So far, only ASTMA333Gr.8 and Gr.11 steel pipes represented by ferrite-type low-temperature seamless pipes with operating temperatures as low as -196℃ have been successfully commercialized. For safety reasons, countries have The production and use of tubes have developed special standards, such as EN10216-4 and GB/T18984. From the point of view of use, cryogenic pipes mainly include cryogenic pipes and cryogenic heat exchanger tubes. Compared with the national standard and the European standard that only set a single standard, Japan and the United States have formulated different standards for their purposes, such as JIS for cryogenic pipes. G3460 and ASTM A333, and JIS G3464 and ASTM A334 for low temperature heat exchanger tubes. The production and acceptance of cryogenic seamless pipes in the world mostly adopt American standards, and domestic designs also refer to American standards. Therefore, it is a general trend to produce cryogenic pipes according to American standards. This is not only conducive to the domestic use of American standard design requirements, and realizes domestic substitution, but also Conducive to direct export of products to the international market.
In reality, with the continuous improvement of the level of localization of large-scale petrochemical equipment, especially the successive export of complete equipment, it is necessary for domestically produced American standard cryogenic pipes or national standard cryogenic pipes to be included in the support of American standards, and it is especially urgent to expand international cryogenic seamless pipes. system. The continuous improvement of my country's steel equipment and technology also has the basis for domestically produced American standard cryogenic pipes. The evaluation of exceeding standard limits and non-standard applicability evaluation is not only conducive to proving the excellent quality of domestically produced American standard cryogenic seamless pipes, but also explores Its extreme use temperature and extended use.
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