The main purpose of the national standard low temperature seamless steel pipe
: used in the pharmaceutical industry to produce ethylene, propylene, urea, synthetic ammonia, compound fertilizer and other equipment and processing equipment such as washing, purification, desulfurization, and degreasing. It can also be used to manufacture cryogenic equipment and ultra-low temperature. Refrigerators, pipelines and fittings for transporting ultra-low temperature liquefied gas, such as petroleum gas cryogenic separation equipment, air separation equipment, etc. There are two main types of refrigerated pipe materials, austenite and ferrite. Due to the different crystal structure of austenitic cryogenic pipes, there is no brittle transition temperature in the low temperature section, and there is generally no need to verify its low temperature impact toughness. , But it is stipulated that when the use temperature is not lower than -196℃ (low temperature section), the impact test can be exempted, and when the use temperature is-(ultra-low temperature section), it must be carried out in accordance with the requirements of the design documents. The ferrite tube has an obvious low-temperature brittle transition temperature, and has its suitable low-temperature section. Although the low temperature limits of steel are slightly different in countries around the world, the actual industrial environment (liquid hydrogen) can be as low as -253°C or higher.
So far, only steel pipes represented by ferrite-type low-temperature seamless pipes with a service temperature of -196℃ have been successfully commercialized. For safety reasons, countries have formulated special regulations for the production and use of ferrite-type cryogenic pipes. Standards. From the point of view of use, cryogenic pipes mainly include cryogenic pipes and cryogenic heat exchange tubes. Compared with the situation where only a single standard is established for the national and European standards, cryogenic tubes with different uses have different standards. Internationally, low temperature heat exchangers have been developed. The production and acceptance of low-temperature seamless pipes of pipes mostly adopt domestic design, and also adopt reference production of low-temperature pipes. This is not only conducive to adapting to domestic design requirements and realizing domestic substitution, but also conducive to direct export of products to the international market.
In fact, with the continuous improvement of the level of localization of large-scale petrochemical equipment, especially the successive export of complete equipment, it is necessary to introduce domestic cryogenic pipes or national standard cryogenic pipes as support, and it is particularly necessary to expand the international cryogenic seamless pipe system. With the continuous improvement of my country's steel equipment and technology, it also has the basis for the localization of low-temperature pipes. The evaluation of over-limit limits and non-standard applicability will not only help to prove the excellent quality of the localization of low-temperature seamless pipes, but also It is possible to explore its limit use temperature and expand the use range.