It’s claimed that the Collins class submarines are constructed of a lighter, yet stronger steel than the HY100 steel used in the Virginia class. It’s also easier to weld and has better blast properties. The following article was written when the French designed Attack class submarine was being developed for the RAN. It shows that considerable effort was being made to design the best steel possible for the generally warmer waters that the new submarines would be operating in.
https://www.australiandefence.com.au...erial-advances
It will be interesting if this steel technology can be used on the SSN that is chosen for the RAN. It may introduce extra design costs which is not desirable when the intention is to build a mature “off the shelf design”.
Also, the Collins class has X configuration of the aft control surfaces which give improved manoeuvrability and less drag as they are smaller in size. This setup works very well in shallow water operations. It also has more effective control when turning the submarine whilst at high speed - it’s easier to compensate the tendency for the bow to drop. The surfaces are less affected by disturbed water from the sail, etc. Neither the Astute or Virginia class have this configuration but the new Columbia class SSBN will have X configured control surfaces.