Abstract: An ultra high head pumpturbine power generating plant with a turbine having a runner rotating with water flow supplied through a high head conducting tube. A rotary electric machine rotates with rotation of the runner. The head is in the range of 400-600 m, and the runner is at least 5 meters in diameter. The said runner has characteristics of toughness at room temperature: at least 500 N/mm.sup.2, or tensile strength at room temperature: at least 650 N/mm.sup.2, elongation at least 16%, reduction of area at least 45%, 2 mm U-notch impact value at 0.degree. C. at least 100 J, and fracture toughness at least 6000 N/mm.sup.3/2.

Abstract: High toughness stainless steel type 13Cr5Ni containing C: 0.008-0.03% (by weight, all of the following elements), Si: max. 1%, Mn: max. 2%, Cr: 10.0-14.0%, Ni: 4.0-7.0%, and Mo: 0.2-2.0%, in which (Cr/Ni) ratio is in a range of 2.0-3.0 or (C/Mo) ratio is in a range of 0.015-0.1, as a structural material for fluid machinery, austenitic stainless steel containing C: 0.10-0.30% (by weight, all of the following elements), Si: max. 1%, Mn: max. 2%, Cr: 16.00-23.00%, Ni: 1.00-8.00%, and Co: 2.00-9.00%, and Ni+Co: 6.00-12.00% as a weld padding layer forming material, and fluid machinery using the same.