[en] Experimental data characterising physicochemical properties of different areas of niuobium welded joint are processed, interpolation polynomials being derived on this basis. Main regularities of physical and chemical heterogeneity along the welded joint cross section are established. It is shown that local increase of dislocation density, micro- and macro-stresses values, interstitial impurity concentration into the heat affected zone promotes the embrittlement of this metal zone in consequence impact strength and resistance to crack propagation of welded joints decrease