The term cryogenic steel is used in two main contexts. Firstly, it describes the process of hardening steel alloys using liquid nitrogen (LN2). At temperatures as low as -185°C (-301°F), certain steels undergo partial phase transformations from austenitic to martensitic crystal structures. Some may even form fine precipitate carbides within the crystal matrix. These phenomena improve the strength and hardness of the material to impart enhanced wear-resistant capabilities. Secondly, cryogenic steel is used to describe any grade that is suitable for cryogenic applications. Interestingly, the former is unlikely to exist without the latter.
Cryogenic Treatment: Innovation Built on Cryogenic Steel
Liquid nitrogen is simply nitrogen in a liquid state at a temperature of -195°C (-320°F). The gas is liquefied under high pressures and can expand rapidly to a very large volume, with a liquid-to-gas expansion ratio of 1:694 at room temperature. Consequently, LN2 must be stored in hermetically-sealed containers made of sturdy materials that will not embrittle at low temperatures. Cryogenic steels are subsequently used for LN2 storage and delivery applications.
Industrially-produced liquid nitrogen services a wide range of industries beyond metal production, including the food and beverage, and medical sectors. Production and delivery of LN2 are facilitated by cryogenic steel containers and tankers that contain the material under optimal conditions during storage and transit.
Properties of Cryogenic Steel
Cryogenic steels must routinely contend with extremely low temperatures without succumbing to brittle-ductile transitioning. This describes the process whereby steels crack at low temperatures, and shatter on impact rather than deforming. In the context of cryogenic storage, this could have catastrophic implications. Containers must retain high toughness qualities down to temperatures of -195°C to meet the necessarily high-quality standards of gas-liquefaction plants and storage containers.
Chemistry of Low-Temperature Performance
Normal carbon-steel has characteristically poor brittle-ductile transition characteristics, but the high strength properties of low carbon alloys are attractive for multiple liquid gas storage applications. Research and development (R&D) into novel alloy compositions in the mid-20th Century demonstrated the ability for nickel (Ni) to moderate the embrittlement of carbon-steels with a reduced carbon (C) content. The onset of so-called 9% nickel steel revolutionized the early liquefied natural gas (LNG) industry by making storage and production of liquefied methane (CH4) and ethane (C2H6) both more affordable and safer.
Cryogenic Steel Grades from Masteel
Masteel is the UK’s leading supplier of cryogenic steels for liquid gas storage and other cryogenic applications. These products are fundamental to a broad range of end-use markets, each with extremely high standards of quality and safety. Our cryogenic steels are produced with reliability and safety in mind, supplying the infrastructure for a safe and sustainable supply of raw materials.
We offer a comprehensive range of cryogenic steel grades for storage and transit applications, including:
- ASTM A553
- ASTM SA553
- ASTM A353
- ASTM SA353