Acciaio-class submarine

Italian Acciaio-class submarine (Porfido)
Class overview
Name:	Acciaio class
Builders:	Odero Terni Orlando (OTO), Muggiano Cantieri Riuniti dell' Adriatico (CRDA), Monfalcone Tosi, Taranto
Operators:	Regia Marina
Preceded by:	Adua class
Succeeded by:	end of 600 series
In commission:	1941–1966
Completed:	13
Lost:	8
General characteristics
Type:	Submarine
Displacement:	697 long tons (708 t) surfaced 850 long tons (864 t) submerged
Length:	60.18 m (197 ft 5 in)
Beam:	6.44 m (21 ft 2 in)
Draught:	4.78 m (15 ft 8 in)
Propulsion:	2 diesel engines, 1,400 hp (1,000 kW) 2 electric motors, 800 bhp (600 kW)
Speed:	14 knots (26 km/h; 16 mph) surfaced 7.7 knots (14.3 km/h; 8.9 mph) submerged
Range:	3,180 nmi (5,890 km) at 10.5 kn (19.4 km/h) surfaced
Test depth:	80 m (260 ft)
Complement:	45
Armament:	1 × 100 mm (4 in)/47 calibre deck gun 1-2 × 20mm/70 AA 6 × 533 mm (21 in) torpedo tubes (4 forward, 2 aft) 12 × torpedoes

The Italian Acciaio-class submarine (also sometimes called Platino class) was the fifth subclass of the 600 Series of coastal submarines built by the Regia Marina. They were completed during the early 1940s and saw service in World War II.

The Acciaios were a development of the Adua and Perla designs, with some improvements, such as a lower conning tower to improve stability and reduce the silhouette. Of the 13 vessels in the class, six were built by CRDA at Monfalcone, four by OTO at Muggiano, and three by Cantieri Tosi in Taranto, the three main Italian shipyards for submarines. They were single-hulled with side tanks, and built to a Bernardis design, though the Tosi vessels had more powerful engines (at the expense of the two stern torpedo tubes, giving a surface speed of 14.7 knots (27.2 km/h; 16.9 mph).

The word Acciaio means "steel", and all vessels in this class were named for metals and minerals.

Of the 13 vessels completed 8 were lost in action, serving in the Mediterranean theatre of operations.