In comments below http://gentleseas.blogspot.com.au/2015/08/australias-naval-shipbuilding-blueprint.html “S” (and comment at August 8, 2015 at 7:47 PM for answeres to 2.1 and 2.2) has provided very interesting views on Japanese-Australia submarine issues. This is concerning the Soryu and Collins.
S answered "I think that the continuous building system is an implicit requirement to achieve and maintain a higher performance [capability] of the Japanese submarine force [and individual subs]. One of the most important technologies is hull welding. Welders must be continuously engaged in welding to maintain their welding skill and qualifications, especially for gas tungsten arc welding (GATW). Other technicians, including inspectors, must maintain skills and qualifications. Inspectors are required to have the highest skill."
S answered: "[The relationship] between operational life and hull strength is not clear, because operational life of Uzushio class submarine [see SS-566] with NS63 hull was 18 years."
"I think Australia should not persist [with] NS110 technology [use Japanese NS110 grade steel for the] following reasons:
1) this technology including GTAW technology is one of most important technology which Japan cannot share with other countries (eg. Germany does not share its non-magnetic hull steel, except with Italy [the joint builder of the 212]),
2) maintenance of this technology is very difficult [particularly cutting and welding],
3) new steel which Japan will propose may be more suitable for Australia than NS110."
"I think that Collins class with single hull made of BIS 812 EMA [see Submarine Pressure Hull Table] is out of date in terms of magnetism. As the Ni content (1.28wt%) of BIS 812 EMA is very low , this steel is magnetic. So a weak point of the Collins class is a more detectable hull than more modern submarines (which have a low magnetic single hull or low magnetic double hull (low/non-magnetic outer hull and magnetic inner pressure hull)). [On BIS 812 EMA's Ni content see page 11 and much detail on BIS 812 EMA's magnetic properties in that document - including pages 24-25. Many references to magnetism and submarines here. So development of welding user friendly steel with higher Ni and Cr contents improving magnetism and low-temperature properties is a better option."
S made the observation "I think there are four options for Australia's of next submarine: 1) modified SS29 [or 29SS see see Table at bottom of] type of Japan, 2) modified SS29 type with new steel hull, 3) Type 216, 4) Conventional "Shortfin" Barracuda."