Assuming it is ASTM A353. Can be used for very low temperature service.
AWS specification is A5.11-76 or A5.4-78.
Electrodes can be ENiCrFe-2 (95% joint efficiency) or ENiCrMo-3 or E310. These are suggested electrodes for shielded metal arc welding of high strength low-alloy steels for pressure vessels.
Weldments are seldom post weld heat treated unless weldment must maintain dimensions during machining OR is exposed to an environment that can cause stress corrosion cracking OR requires softening to improve ductility. Temperature for postweld heating is 1025 - 1085 Deg F for A353.
Thermal cutting - can use oxy fuel, air carbon arc, plasma arc. Oxide and any residue should be removed and cracks removed mechanically.
Preheat may be necessary dependant on section.
Taken from Welding Handbook, Seven Edition, Volume 4 by AWS.