At extremely low temperatures, such as -140°C, carbon steel can become very brittle and prone to fracture. This phenomenon is known as low-temperature embrittlement. The risk of fracture at such temperatures is indeed a concern for carbon steel.
When a material is cooled to very low temperatures, the energy within its atomic structure decreases, causing a reduction in the mobility of atoms and dislocations. This reduced mobility leads to an increase in the material's brittleness. Carbon steel, which contains iron and varying amounts of carbon, is susceptible to this embrittlement.
At low temperatures, the steel's ductility decreases significantly, and its resistance to crack propagation diminishes. The steel becomes more rigid and less able to absorb impact or deformation without fracturing. Stress concentrations, such as notches or sharp edges, can further exacerbate the likelihood of fracture.
Fracture under these conditions can occur with little warning or plastic deformation, making it a concern for applications that experience extremely low temperatures. It is crucial to consider the temperature limitations and brittleness characteristics of carbon steel when designing structures or equipment for such environments.
To mitigate the risk of fracture at low temperatures, alternative materials with better low-temperature properties, such as low-temperature steels or alloys specifically designed for cryogenic applications, are often preferred. These materials are engineered to withstand and maintain their mechanical properties at extremely low temperatures, reducing the risk of brittle fracture.