HE requires mono-atomic hydrogen, not hydrogen gas. So if because of electrolysis, chemical reaction, or active corrosion there is a source you then need to think about HE.
In austenitic SS you only need to to worry if you have welds that have not been annealed and have high residual ferrite content they could suffer HE.
Definitely no, irrespective of the condition of your welds. At those temperatures, for such a duration, even carbon steel would be OK, even at very high hydrogen partial pressures.
