In the world of high technologies and extreme conditions ordinary materials often prove powerless. One such most complex environments is cryogenic — the world of ultra-low temperatures dropping below −150°C. Here, on the edge of space cold, ordinary steel becomes brittle as glass. But not all metals surrender before this test. Specially for work under such conditions cryogenic alloys have been created — materials that not only survive but also work effectively in the “realm of ice.”
To understand the value of cryogenic alloys, let us figure out the nature of cold brittleness. When temperature decreases, behavior of the crystal lattice changes. In carbon and low-alloy steels the ability for plastic deformation sharply decreases: energy of impact or local stress is no longer dissipated but leads to instantaneous brittle destruction.
From a practical point of view this means that even a microscopic defect, impurity, or non-metallic inclusion may become a cause of structure destruction. Exactly therefore when designing materials for low-temperature service conditions the key task of metallurgists consists in forming such a microstructure that retains toughness and fracture resistance even under extreme cooling.
Cryogenic properties of steel are the result of precise engineering calculation and strict technological control. For the material to work confidently at ultra-low temperatures, it must possess a number of principally important characteristics.
The combination of these factors makes it possible to create steels and alloys able to work reliably under conditions where a mistake may cost too much.
Depending on the working temperature range and service conditions, cryogenic materials are conventionally divided into several groups. Such division helps engineers choose an optimal alloy for a specific task.
Such an assortment makes it possible to select an optimal material — from serial industrial facilities to unique scientific and space installations.
One of the most widespread materials for low-temperature service is austenitic corrosion-resistant steel 12Kh18N10T.
Chromium (~18%) ensures high corrosion resistance, nickel (~10%) stabilizes the austenitic FCC lattice, and titanium binds carbon, preventing formation of chromium carbides and development of intergranular corrosion.
Steel 12Kh18N10T retains high impact toughness and strength characteristics at temperatures down to −196°C (liquid nitrogen temperature). Thanks to this it is widely applied for manufacturing cryogenic vessels, pipelines, fittings, and elements of systems for storing and transporting liquefied gases — nitrogen, oxygen, argon.
A special place among cryogenic materials is occupied by alloy 36N, belonging to the class of precision high-nickel materials.
A key feature of 36N is high nickel content — about 36%, which ensures exceptional stability of the austenitic structure over the entire working temperature range.
Besides high cryogenic resistance, alloy 36N possesses special physical properties including a strictly specified temperature coefficient of linear expansion. Thanks to this it is indispensable in:
36N is used where requirements for accuracy and reliability go far beyond standard engineering solutions.
Manufacturing materials for work at ultra-low temperatures requires impeccable control at all production stages — from charge selection to observance of melting, rolling, and heat treatment regimes. Any deviation in technology may lead to loss of cryogenic toughness and, as a consequence, to emergency situations.
Petersburg Plant of Precision Alloys possesses all the necessary technological arsenal for producing cryogenic steels and alloys including grades 12Kh18N10T and 36N. Modern equipment, strict quality control, and deep expertise in precision metallurgy make it possible to guarantee reliability and durability of equipment working on the edge of the possible — in the world of ultra-low temperatures.
