Study On Standard Of Welding Procedure Qualification For Aeroengine Vacuum Brazing

At present, as there is short of the standards of welding procedure qualification inaeroengine production which results is short of the evaluation criterion in weldingprocess design, solving the problem of qualification on-the-spot and welding producttesting, etc. All of these affect the application of welding technology in aeroengine. It isnecessary to establish a standard of aeroengine welding procedure qualification.Based on collecting, sorting and analyzing the domestic and foreign relevantstandards of welding procedure qualification, combined with the vacuum brazingprocess in aeroengine production, this paper formulate the qualification standards thatsuitable for vacuum brazing process in aeroengine production, including procedurequalification rules, procedure qualification test and qualified index. These standardsprovided the basis for welding procedure qualification of vacuum brazing in aeroengineproduction.Base materials is an important factor in welding process. The classification of basematerials can reduce the number of welding procedure qualificatione effectively. Theclassification of base materials references the classification methods of ISO15608"Welding-Guidelines for a metallic materials grouping system"and JB4708"steelpressure vessel standard of Welding procedure qualification". Combined with thevacuum brazing process in aeroengine production, classified the materials that suitablefor vacuum brazing in aeroengine production according to the chemical composition,mechanical properties and brazability.In brazing, as the performance of brazing joint depends on the performance ofbrazing filler metals mainly, the brazing filler metals is an important factor in brazingprocess. So it is necessary to classified the brazing filler metals that selected by basematerials, in order to reduce the number of welding procedure qualification. Classifiedthe brazing filler metals mainly based on melting temperature, chemical composition,the wettability and the interaction with base materials.Important factor of welding procedure qualification is prerequisite for projectapproval of welding procedure qualification. The influence of each factor of vacuumbrazing process to the quality of the brazing joint is analysised in this paper. The following aspects are determined as the important factors for welding procedurequalification of vacuum brazing process, which are cladding, format of joint, vacuumbrazing clerance, vacuum degree, equilibrium temperature, holding time at equilibriumtemperature, vacuum brazing temperature, holding time at brazing temperature, coollingrate and vacuum brazing heat treatment. When the process parameters mentioned aboveare changed, welding procedure should be evaluated again.Welding procedure qualification test is an important part of welding procedurequalification, which validatethe the correctness of welding process. The following testitem are determined for vacuum brazing procedure qualification in aeroengineproduction,which are tension-shear test, peel test, cross section test, stress rupture testand high cycle fatigue test. The test methods and qualified index is formulated in thispaper.