IIW White Paper

9.1.5 Hot topics Development and uptake of welding technologies for fabrication of high quality nuclear reactor components and specialised materials, including multi-disciplinary intelligent welding. Development of, and adherence to design, fabrication and maintenance codes and regulations on a global level. Training, qualification and certification for design, engineering, welding and inspection personnel to international standards. Utilisation of latest information technologies to record and analyse data on an ongoing basis. Development of environmentally sound procedures for decommissioning and waste disposal. 9.1.6 Power - Hydro Hydroelectric power plays an important role in the overall power generation mix. The overall installed power of hydropower plants increases steadily and covers approximately two thirds of the world wide renewable and around 3% of the total energy produced. For the application of welding in hydropower engineering the welding of penstocks and linings plays an important role. A special feature of hydropower plants is the long service period of 50+ years which is a challenge for engineers. The selection of materials and welding processes plays an important role to assure the reliability of the sustainable technique. The Hydroelectric turbine (runner) is the very core and most vital equipment in the plant, which requires a very good emphasis on materials selection and engineering criteria and very good welding practices for proper component integrity. The following highlights the various challenges associated with turbine runner fabrication. Modern hydroelectric turbine runners are made of high strength stainless steels alloys, with reduced weight and high resistance to water induced cavitations. Proper selection of welding technique and welding consumables which match or exceed the base metal properties are absolutely essential towards successful fabrication of hydroelectric turbines. Hydroelectric turbines are often designed to the original equipment manufacturers design standard and recommended codes of practice. Welding has a very important role in the design and construction of major equipment for hydroelectric generating stations especially turbine runners and other allied components. The following highlight the role of welding in the fabrication of hydroelectric turbines. Materials of construction Turbine runners are fabricated often from “Martensitic Stainless Steels” conforming to ASTM A-743. Alternatively EN-10283 is the common standard followed for these alloys if fabricated in Europe. Cast martensitic stainless steels conforming to the above specifications have the following chemical composition and mechanical properties: Heat Treatment -QT- Heat to 1850°F [1010°C] minimum, air cool to 200°F [95°C] or lower prior to any optional intermediate temper and prior to the final temper. The final temper shall be between 1050°F [565°C] and 1150°F [620°C]. Specification: ASTM-A743 Grade CA-6NM or GX4CrNi13-4(DIN-1.4317) as per EN-10283. Nominal Chemical Analyses: C≤0.05%, Si- ≤ 1.00%, Mn ≤ 1.00%, P+ S≤ 0.035%. Cr-12.00-14.00%, Ni-3.50-4.50%, Mo-0.40-0.70%. Mechanical Properties: UTS-760-960 MPa, YS-≥ 550 MPa, %EL-≥ 15, % Reduction of Area-35, Hardness-240-300 HB, Charpy-V Impact at 20 0 C ≥ 90 Joule.

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Through Optimum Use and Innovation of Welding and Joining Technologies

Improving Global Quality of Life