Today we want to talk about piping for transporting liquid hydrogen at -253°. Some time ago, one of our readers asked us which type of stainless steel was suitable for this use. What did our expert answer about liquid hydrogen piping?
Cryogenic temperatures: which material can withstand them?
Austenitic steels, such as AISI 316 and AISI 304, are immune to the ductile-brittle transition. As a result, they retain their toughness down to cryogenic temperatures. But what issues can arise? One limitation could be that, at low temperature, the corrosion resistance of this type of stainless steel decreases drastically. Acids, in fact, attack the protective oxide film. This causes general corrosion.
AISI 304 or AISI 316? This is the question.
For the reasons mentioned above, it is not advisable to use AISI 304 stainless steel. This is because the molybdenum carbides generated by AISI 316 are better than the chromium carbides generated by AISI 304.
liquid hydrogen piping: welded elements.
And for the various “stiffeners” that are welded to the pipe, what material to use? To make this choice it is necessary to take into account several factors (in addition to the composition of the material). Let’s see together what they are:
- duration of exposure at low temperature
- impact on the clamped (or welded) parts and the corrosive environment in which they operate.
If these “stiffeners” are welded, the advice is to use alloys with low carbon content (e.g. AISI 316L) and, given the operating temperature, carry out a detailed environmental analysis. Finally, the last piece of advice is always to consult a metallurgist expert.
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