Materials for the Arctic: strength and reliability at low temperatures

Construction and work in the Arctic is a technically complex task requiring special materials able to withstand the corrosive effect of sea air and extremely low temperatures. Low temperatures not only raise strength of steels and alloys but also reduce their toughness and crack resistance, which may lead to rapid crack propagation. Low-temperature embrittlement is especially critical for cast elements and products of complex shape.

Cold-resistant materials: main application areas

Cold-resistant alloys are one of the solutions for work in Arctic conditions. These materials possess sufficient toughness at low temperatures and are widely used in various industries:

• metal structures and pipes — cold-resistant alloys are used to create strong metal structures, railway tracks, and gas and oil pipeline pipes under climatic cold conditions (down to −60°C);
• aviation and space — applied in aviation and space technology where high requirements are placed on strength and resistance to low temperatures;
• cryogenic technology — for creating systems operating at extremely low temperatures such as oxygen temperatures (−183°C) and liquid helium (−269°C).

Cold-resistant alloys: retaining toughness at low temperatures

Cold-resistant alloys are materials that are not subject to cracking during cold working (do not possess cold brittleness) and can retain sufficient toughness at low temperatures (down to −269°C).

Cold brittleness is characteristic of metals with a body-centered cubic (BCC) crystal lattice such as tungsten, molybdenum, iron, chromium, as well as magnesium, zinc, and other materials with a hexagonal close-packed (HCP) lattice. Materials with a face-centered cubic (FCC) lattice and titanium alloys with an HCP lattice usually do not have a cold-brittleness threshold: their impact toughness gradually decreases with lowering temperature.

However, when choosing materials for use in the Arctic and other extreme conditions it is important to take into account not only their cold resistance but also technological properties such as weldability and ductility. The former is especially important for cryogenic equipment where welding is widely used, and the latter — for thin sheets and thin-walled structural elements.

Cold-resistant precision alloys: ideal solutions for extreme conditions

The group of precision cold-resistant alloys intended for use at low temperatures includes a number of materials with various chemical compositions:

• invar — an iron-nickel alloy with a low thermal expansion coefficient, ideally suited for use at extremely low temperatures;
• constantan — an alloy of copper, nickel, and manganese with stable electrical properties at low temperatures, widely used in producing precision resistors and thermocouples;
• shape-memory alloys (for example nitinol, consisting of nickel and titanium) — able to restore their shape after deformation at temperatures below the Curie point, which makes it possible to use them in medical implants and devices operating under cold conditions;
• aluminum-based alloys such as Al-Li — possess high strength and stability at low temperatures, widely applied in the aerospace and automotive industries;
• titanium alloys — resistant to low temperatures, possess high strength and corrosion resistance, making them ideal for use in cryogenic technology.

Production of metrological and geodetic equipment, as well as cryogenic and radio-electronic apparatus, requires use of precision alloys with a precise value of the temperature coefficient of linear expansion (TCLE). In these cases TCLE values are dictated by service conditions. For example, measuring instruments must be highly accurate under any temperature regimes, length standards must retain their original dimensions under extreme temperature fluctuations, and pipelines must retain reliability and structural strength when transporting liquefied gases.

Alloys for joining with dielectrics (glass, ceramics) must also have a certain TCLE value. Reliable joints of materials with different properties can be created only when linear expansion coefficients match in the technological and working temperature range. Most often invar alloys are used for these purposes.

Production of cold-resistant materials at PZPS

Materials intended for work in the Arctic must combine cold resistance, strength, and resistance to low temperatures. PZPS LLC offers cold-rolled strip from invar with a regulated TCLE value of grade 36N in accordance with GOST 14080-78.

Modern technical equipment and a modernized laboratory complex of the plant make it possible to ensure high accuracy of technological processes, as well as full control throughout the entire technological cycle of producing cold-rolled strip from this alloy.

In addition, a research center operates at the enterprise that is ready to solve many problems of metallurgical production, including developing new alloys for use under low-temperature conditions.