镍铁型焊条焊接高强球铁接头云纹实验解析研究

RESEEARCH ON NODULAR IRON JOINT WELDED WITH NICKEL-IRON ELECTRODE BY MOIRE FRINGE METHOD

镍铁型铸铁焊条已经相当广泛地用来焊接QT60—2球墨铸铁。然而,研究工作表明,这些焊接接头的强度较低。本文首次利用密栅云纹法研究了单向拉伸焊接接头的受力状况,获得了接头区域的全场位移、应变和应力分布。从焊接接头应变和应力分布的不均匀性,分析了裂纹产生及扩展的原因,用扫描电子显微镜观察了断口形貌,发现有大量的球状物分布在断口上,这可能是导致焊接接头低应力破断的原因。这一次现有助于改进镍铁型铸铁焊条的性能,提高接头的强度。

Nickel-iron type cast iron electrodes are widely used in welding QT60-2nodular iron.Nevertheless,the research work has demonstrated that the strengthof these welded joints is low.In this paper,the state of stress of weldedjoints under uniaxial tensile have been studid by the Moire fringe method.The total displacement,strain and stress of the welded joint were obtained.Based on the uneven distribution of the strain and stress,the mechanism ofcrack initiation and propagation was discussed.The fracture surfaces wereexamined by scanning electron microscope.A lot of spherical substances onthe fracture surfaces were found,which may be another reason leading tocracking of the welded joint under low tensile stress.These new clues willhelp impreving the properties of nickel-iron type cast iron electrodes and thestrength of this welded joint.