Metal that I never had in my project. P90s series.................................P92 ASTM A335 P92 is the part of ASTM A335, The pipe shall be suitable for bending, flanging, and similar forming operations, and for fusion welding. UNS Designation K92460 Welding processes The most common welding processes for P92 fabrication are GTAW (TIG) and its narrow gap and hot wire variations, SMAW (MMA), FCAW and SAW. AWS D10.21, ‘Guideline for Welding Advanced Chromium-Molybdenum Steel Piping and Tubing’) Consumables: SMAW AWS A5.5: E 9018-G EN 3580-A: E Z CrMoWVNb 9 0.5 2 B 4 2 H5 GTAW AWS A5.28 ER90S-B9 (mod.); ER90S-G EN 21952-A WZ CrMoWVNb 9 0.5 1.5 GMAW AWS A5.28 ER90S-B9 (mod.); ER90S-G EN 21952-A GZCrMoWVNb 9 0.5 1.5 SAW+Flux AWS A5.23 Class EB9 (mod.) EN 24598A S ZCrMoWVNb9 0.5 1.5/SA FB 2 EN 10270 S ZCrMoWVNb 9 0.5 1.5 In general Preheat/interpass The available literature and the WPS’s analysed for this review generally agree on a minimum preheat temperature of 200˚C and a maximum interpass temperature of 300˚C (some sources recommend 250°C and others 350°, for preheat and interpass, respectively). In general PWHT performance and parameters An average temperature of 760°C (750-770˚C range) represents a good compromise between improving toughness and creep strength and ensures a limited holding time (for lower temperature ranges, the holding time necessary to achieve the required toughness would be too long). However, it is paramount that the actual composition of the weld metal and parent metal is known, to ensure that the lower critical transformation temperature is not exceeded. The holding time depends on the selected temperature range, however, it may also be subject to commercial pressure, requiring the shortest possible holding time (hence a higher temperature would be required). In general Localised PWHT Local PWHT is performed when it is not practical to heat treat a complete welded structure (eg final closure weld on a piping system) or when weld repairs are carried out (particularly in service, during outages etc). When performing local PWHT it is very important to determine an adequate soak band (SB), heated band (HB) and gradient control band (GCB). These will typically encompass a 360° area around cylindrical components. This band should also include any attachments, nozzles, trunnions etc. Heating methods The use of inappropriate heating methods, hence the incorrect application of the heating cycle, particularly of the PWHT, is the major source of problems with welds between creep-resistant grades. In addition, potential inconsistencies between the heating methods used in qualifications and those applied in production, in the field more often than in workshops, must be taken into account. Flame heating: Furnace heating: Resistance heating: Induction heating:
Posted on: Mon, 03 Nov 2014 21:50:36 +0000
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