Development and Technology of Steel Pipes for Ultra-low Temperature Below -100℃

ultra-low temperature steel pipes are crucial components designed to exhibit excellent low-temperature toughness and retain high strength even in extremely cold environments, typically below -100°c. these pipes find extensive applications in low-temperature pressure vessel pipelines ranging from -100°c to -195°c and in low-temperature heat exchanger pipelines. industries such as liquefied natural gas (lng) storage and transportation, which operate at ultra-low temperatures of around -162°c, as well as the production, storage, and transportation of various liquefied petroleum gases, liquid oxygen, liquid nitrogen, and equipment used in frigid regions, demand a significant quantity of low-temperature pipelines.

the essential characteristics of these low-temperature pipelines include good low-temperature toughness, corrosion resistance, and weldability. given that these pipelines are installed at room temperature but operate at low temperatures, the material's coefficient of linear expansion should be minimized, while maintaining good economic and safety performance.

common materials used for lng low-temperature pipelines include aluminum alloy, stainless steel, and nickel-containing steel. these materials possess the required low and ultra-low-temperature toughness needed for lng applications. aluminum alloy, however, has seen reduced usage due to its higher coefficient of linear expansion. stainless steel, with mature production technology and excellent corrosion resistance, is widely adopted. nickel-containing steel, with its excellent comprehensive performance and noticeable economic advantages, is witnessing a growing trend in its application in the foreign lng industry.

in recent years, major chinese steel enterprises,hunan valin steel co ltd,have achieved mass production of 9ni steel plates. however, the produced steel plates exhibit significant compositional segregation, low yield rates, and high production costs. the production of corresponding steel pipes is still in its infancy domestically, while foreign applications of 9ni steel pipes in lng peak-shaving facilities and oil tanker loading and unloading facilities have been successful. according to foreign research, considering the brittleness and shrinkage issues of low-temperature pipelines, 3ni and 9ni steel pipes are expected to become the mainstream materials for ultra-low temperature pipelines.

the american standard "astm a333 standard specification for seamless and welded steel pipe for low-temperature service" includes grades like gr3 (3.5% ni) and gr8 (commonly known as 9% ni), both of which are nickel-containing steels. gr3 low-temperature steel is suitable for a minimum working temperature of -100°c, while gr8 low-temperature steel is suitable for a minimum working temperature of -196°c, with a design temperature of -158°c to -162°c and operating pressure of 0.5 to 29 n/mm² for lng storage tanks.

ensuring the safe operation of steel pipes in ultra-low-temperature environments, the development of a333gr3 and a333gr8 low-temperature pipes is of paramount practical and strategic significance. the project encompasses various aspects, including the chemical composition design of ultra-low-temperature seamless steel pipes, the development of continuous casting round tube blanks, research on the hot-rolling process of pipes, and optimization of the heat treatment process. the project incorporates advanced nickel alloy design, smelting processes for high-purity and homogeneous continuous casting billets, rolling processes for high-toughness steel, and heat treatment technology.

the newly developed specifications of ultra-low-temperature seamless steel pipes are being applied in lng storage and transportation pipelines globally, as well as in other low-temperature environment pipelines. additionally, square pipes developed through the project can substitute stainless steel plates for the support of low-temperature gas storage tanks. the project has resulted in two invention patents, the formulation of production processes and inspection points for low-temperature steel pipes, and the establishment of the industry standard gb/t 18984-2016 for seamless steel pipes for low-temperature pipelines.

the project has successfully broken through various key production technologies for low-temperature pipes, expediting the domestication of products. the produced products are primarily used in fpso oil extraction ships used by petrobras in brazil and other projects worldwide. over the past three years, the cumulative supply has exceeded 21,000 tons. the project has played a pivotal role in driving technological advancements within the company, propelling hengyang hualing steel tube to become a leading domestic seamless steel pipe enterprise, and contributing to the overall improvement of hunan's steel industry.

centerway steel co., ltd. has established a good cooperative relationship with the famous domestic professional seamless pipe manufacturer--"hengyang valin steel tube" enterprise. it is the first-level agent of hengyang valin steel tube co.,ltd and provides you with one-stop total pipe solutions.

centerwayis committed to providing one-stop service for steel pipe products to customers around the world.