30KhGSA steel high-pressure vessels electron-beam welding technology

UDK: 621.791.8:622.276

Key words: electron beam welding, 30KhGSA, ultrasonic testing, metallographic research, heat treatment, non-destructive testing, hardness

Authors: V.K. Dragunov, A.P. Sliva, I.E. Zhmurko, A.L.Goncharov, E.V. Terentyev, A.Yu. Marchenkov, D.A. Kovalenko, E.Yu. Bolokhov (National Research University Moscow Power Engineering Institute, RF, Moscow)

A new 30KhGSA steel weld constructions designing technology applicable for high-pressure vessel production is developed. The proposed technology provides high quality of welded joints and includes electron beam welding (EBW), heat treatment, phased array and TOFD ultrasonic control. EBW modes parameters for model welded joints, which includes electron beam circle-type scanning for weld root defects elimination are proposed. Static tension tests of welded joints in accordance with state standard GOST 6996-66 as well as metallographic research of weld seam, heat affected zone and parent metal are made. Weld seam, heat affected zone and parent metal strength and ductility characteristics are also evaluated by ball indentation. Yield stress and ultimate stress are estimated by hardness on yield stress HB0.2 and hardness on ultimate stress HBU. Ductility characteristics - ultimate uniform elongation and final elongation of local welded zones are calculated using the correlations proposed in Moscow Power Engineering Institute. Fine agreement of yield stress, ultimate uniform elongation and final elongation values, obtained by tension test and indentation test is shown. The difference between ultimate stress values, estimated by these methods, is shown to be 3-6%. Welded joints heat treatment is shown to cause much smooth mechanical properties distribution over the weld joint cross section. Microstructure and properties of metal in remelting zone are shown to be the similar to the weld seam metal. Tandem control method using the phased array and TOFD techniques is suggested. The proposed technique provides increased accuracy of defect dimensions measuring as well as the possibility of defect detection regardless of its spatial position, defects zones rejection either amplitude criteria or defect dimension criteria, high efficiency of control operation and the possibility of recording and storage of control results.

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