Materials of construction for low-temperature and cryogenic processes

One key engineering consideration in the choice of materials for construction of storage and transportation equipment of liquefied gases and those used in chemical processes operating at low and cryogenic temperatures is its toughness or impact strength. Toughness can be more important than the tensile strength, yield strength and elongation that play a major role in specification of materials for more conventional temperatures. The impact strength of a material varies with the temperature, indeed it is customary to specify the temperature when citing a given impact strength. A key determinant of the impact strength of a steel or other alloy is the percentage of nickel it contains, an increase in the nickel content improves the notch toughness. Fabrication and welding of materials destined for low or cryogenic temperature operations involves special considerations. It is general practice to have a weld compatible to the parent material in all the respects, including the impact strength.