The debate on pressure hull steel with some relevance to the future Netherlands submarine (Walrus Replacement) issue continues. Below this article on February 5, 2021 an Anonymous commented:
“Concerning the use of austenitic stainless steel (non magnetic) versus the use of dedicated low carbon steel (extra high yield stress) in submarine construction - I did understand that the choice had to do more with the compromise selection relevant to the expected missions; I might be wrong however [Pete comment: Expected missions of the specific submarine class and consumer navy nationality sounds right.]
For a coastal sub (operating in the Baltic [an essential Swedish, German or Polish characteristic is minimal] magnetic signature. This is very relevant (magnetic anomaly signature decreases at the cube with depth and the sensor has to be very close, may be a fraction of a mile) while the need to operate at great depth (250 /400 meters) and endure the associated cycling fatigue /cracks is not the prerequisite [for Baltic subs].
AIP for short distance , low speed makes also sense . (Israeli Dolphins are really in the "parking lot" off Haifa or the Syrian coast for a second Nuclear strike [especially at Tehran]..)
For an oceanic sub which needs to hide below the accoustic diopter at 150m+ typically, magnetism becomes secondary versus the need to have a lighter structure allowing more batteries for a conventional sub, for instance (we are talking a hundred tons probably for equivalent depth).
Magnetic anomaly detection is probably not really pertinent for a nuclear attack sub à la US Seawolf/UK Astute/French Barracuda.
Within a few min of a datum [a SSN] can cruise at 30 knots at 350 m ..How long does it take for a helicopter or plane to be on the spot and launch an attack in the real tactical world ?
The US, UK or French subs use HY100 or equivalent [pressure hull] steel. I do not know about the Japanese choice.”
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On the same thread a different Anonymous responded (at February 6, 2021 at 12:32 AM) about the Japanese choice of pressure hull steel [for Japan's varying oceanic travel and deep seafloor sitting missions]:
“Pressure hull for Japanese submarine is made of [Japanese naval standard] NS80 (proof strength 784MPa [around HY120 see Table 2 below. ]) and NS110 (1078MPa)[around HY156 also see Table 2 below.]. Welding strength of NS80-NS110 and NS110-NS110 were experimentally proven.”
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The following was originally from the article Submarine Pressure Hull Steel (Tables) Especially Swedish of March 7, 2019:
Pete Comment
High proof or yield steel for submarines can be measure in pounds per square inch (psi), (eg. HY80 = 80,000psi) or Mega/million pascals (MPa) with this conversion
https://www.unitconverters.net/pressure/megapascal-to-psi.htm.
For a diesel-electric submarine with AIP (eg. a Swedish Gotland class ) on a typical short 12 day mission in the Baltic Sea it may dive and the operate on its Stirling AIP for 10-12 days. It then surface only once = 1 cycle. Perhaps its pressure hull is good for 200 cycles (?) - although its service life is more rapidly limited by hull rust and corrosion - all contributing to a 34 year service life.
ANONYMOUS' TABLE 1.
- Swedish (Gotlands, future A26s),
- Swedish designed Australian Collins, and
- future SAAB-Damen entry for the Walrus Replacement competition
In the [cylinder like] design of a submarine, the diameter of a pressure hull significantly effects on many other feature of a submarine [including space, propulsion choices and acoustics]. In terms of diameter (which may sometimes equal Beam) Gotland's are 6.2m, A26s 6.75m, Collins 7.8m and 8m for a SAAB-Damen Walrus replacement. Part outer hulls and sonars on hulls will effect the overall beam of a submarine.
Submarine | Pressure hull steel | Proof (or Yield) strength of steel [MPa] | Beam [m] | Diameter of pressure hull | Estimation |
Gotland | Weldox700EM [1] | 700 | 6.2 | Same | In A26, sound absorption rubbers (thickness 100mm) are presumably attached on the surface of prssue hull. In A19, no sound absorption rubbers are attached, or very thin rubbers are used. |
A26 | 700 | ||||
Collins | 700 | 7.8 | Same | Difference in beam is due to difference in position or shape of flanl arry sonar. | |
SAAB-Damen Walrus Replace-ment | 700 | 8 |
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Below is a broader comparison of Chinese, Russian & Western Submarine Pressure Hull Steel Strengths originally published on July 20, 2015. Note the Swedish measure Weldox700 and Australian BIS 812 EMA in both Tables with both at 700MPa equivalent to HY100..
TABLE 2.
YS = Yield Strength or proof stress. HY = High Yield
YS  |  US |  UK |  France |  Germany |  China |  Russiaand India |  Japan |  Australia |  Sweden |
| 550MPa | HY80 | Q1N | 1.3964 | India DMR- 292 # | * 1) NS56 | ||||
| 590MPa | 60HLES | 921A TA5-A | AK-25 48-OT3 | ||||||
| 630MPa | 1.3974 | ||||||||
| 690MPa | HY100 | Q2N | AB-2 | * 2) NS70 | |||||
| 700MPa | 80HLES | BIS812 EMA | Weldox 700 | ||||||
| 785MPa | 980 | AK-29 | NS80 | ||||||
| 890MPa | HY130 | 100HLES | *4) Ti80 | AB-3? | NS90 | Weldox 900 | |||
| 980MPa | AK-33 | ||||||||
| 1075MPa | AK- ?? | ||||||||
| 1178MPa | HY156 | * 3) NS110 |
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COMMENTS FOR TABLE 2.
The higher the yield (stronger) the steel alloy or Titanium alloy in a submarines pressure hull the deeper it can dive in operations. As well as alloy strength other factors also influence diving depth including:
- supports for the the pressure hull
- compartments or multiple pressure hulls, and
- strength of the welds used to join sections of the pressure hull.
It is not possible to verify the accuracy of most of the figures. Commenters who know more are invited to supply corrections.
FURTHER READING
Soryu Submarine Steel Details - Japan Offer to Australia, January 20, 2015
Anonymous and Pete