Nickel Steel Alloys and the LNG Industry
The specialist materials used to transport LNG have to be carefully sourced to ensure that they can safely contain it. During transportation, it is vital that the benefits of natural gas being non-corrosive and non-toxic when it is in its liquid form are maintained. If LNG is vaporised, then it potentially could become explosive or emit thermal radiation hazards. To prevent this, the materials used to transport and store the liquid gas must be reliable and have the ability to maintain the extremely low temperatures required.
Most steel is disposed to crack at low temperatures. This is because of the brittle-ductile transition; an occurrence that causes materials to shatter, rather than deform in extremely low temperatures. However, it has been found that steel produced with 9% Nickel is different: it has a low brittle-ductile transition temperature, resulting in it being able to remain ductile even when extremely cold.
Nickel steel alloys are therefore the most effective metals for the production, containment and storage of liquefied natural gas (LNG) and other cryogenic substances.
These same nickel alloy levels also present strong weldable properties. Where welds are used, they have to be able to be extra tough and resilient to fracture; again, research has found that nickel alloys can withstand temperatures of -196°C without losing toughness.
Nickel is not the only critical material in a nickel steel alloy – the use of stainless steel is also very important as it has a number of advantages of its own. It is highly weldable, has a high resistance to corrosion and does not undergo phase transformations during welding processes. The ability to withstand the impact of very low temperatures comes from a higher ferrite level that is found in high quality stainless steel.
