What is the difference between carbon steel and low-temperature carbon steel?
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Experts in materials, our process packages include carbon steel and low-temperature carbon steel. Only information on low-temperature carbon steel can be found online; it is suitable for operating conditions below 0°C. Does anyone among you know the difference in composition between these two types of steel? Or what are the detailed differences? Please explain.
According to American standards, carbon steel is referenced to ASTM A106, while low-temperature carbon steel is referenced to ASTM A333.
The difference in chemical composition is minimal; it mainly lies in the heat treatment methods used for the steel. You can refer to this document: https://www.docin.com/p-33636992.html?docfrom=rrela
For ASME materials, some steel plates require normalizing and low-temperature impact testing in order to cope with low temperatures. For carbon steel forgings, SA-105 and SA-350 Gr.LF2 CL1 have the same composition; their heat treatment processes differ, with additional requirements regarding low-temperature impact resistance
Low-temperature carbon steel can be used in low-temperature conditions; the definition of low temperature can be found in relevant standards or specifications. Such as: low-temperature steel plates, low-temperature pipes, etc. At low temperatures, carbon steel materials lose their toughness and become more brittle.
A typical example of normal carbon steel is 20 steel; its operating temperature range is generally around -20°C to 425°C. If the application requires operating temperatures as low as -30°C or even lower, then a suitable low-temperature steel must be used, such as Q345C, D, and E, which can handle low-temperature environments
The main difference is that S and P have stricter controls
Understanding the usage requirements for low-temperature steel makes it clear what the difference between them is; SH3059 provides a rather detailed description.
From your description, it’s clear that this refers to carbon steel; by default, this means carbon steel at normal temperatures, while low-temperature carbon steel is used in conditions with low temperatures. In my opinion, when it comes to valves, the temperature threshold for commonly used carbon steel materials is -29°C; carbon steel used at temperatures below this value can be referred to as low-temperature carbon steel valves ； However, for GB materials, the lower limit temperature is -20°C, so it is also possible to classify them based on -20°C. Of course, there are also ultra-low temperatures, -100°C and below – that’s considered ultra-low temperature.