锆/镍电子束环形接头应力分布分析

Analysis of stress distribution characteristics of Zr/Ni circumferential electron beam welded joints

纯锆力学性能、与铀燃料相容性、抗辐照性能良好,广泛应用于核工业中,纯镍具有良好的力学性能与抗腐蚀性能,常用作结构材料.锆/镍异种材料间热物理性能差异大,冶金相容性差,目前没有熔化焊接的研究.采用电子束对锆/镍环焊缝进行焊接,对中焊接时接头由(γ-Ni+Ni_(5)Zr)共晶+Ni_(5)Zr树枝晶复合结构组成,在残余应力的共同作用下导致焊接裂纹,接头强度仅有36.4 MPa.通过偏束焊接得到了无裂纹接头,偏镍0.5 mm焊接时接头强度提高到189 MPa.对不同焊接参数下接头应力场、温度场进行了有限元模拟研究,结合理论计算,揭示了由于环焊缝的结构特点,在焊接的起始阶段有再热现象,接头中具有较高的残余环向应力,偏锆焊接过程中热应力高,偏镍焊接有效降低了接头的残余应力与热应力,是裂纹消失的主要原因.

Zirconium has good mechanical properties,compatibility with nuclear fuel and radiation resistance,is widely used in the nuclear industry.Nickel has good mechanical properties and corrosion resistance,and is often used as a structural material.There are large differences in thermophysical properties and poor metallurgical compatibility between zirconium/nickel.There is currently no research on fusion welding of zirconium/nickel.In direct welding,the electron beam welded joint is composed of(γ-Ni+Ni_(5)Zr)eutectic+Ni_(5)Zr dendrite composite structure,which leads to welding cracks under residual stress.The tensile strength is only 36.4 MPa.In beam offset welding,the tensile strength of the joint increased to 189 MPa.The finite element simulation research on the stress field and temperature field of the joints under different welding parameters,combined with theoretical calculations,revealed that due to the structure of the weld,there is reheating phenomenon in the initial stage of welding,resulting in high residual stress.Electron beam deflects to Ni side effectively reduces the residual stress and thermal stress of the joint,which is the main reason for the disappearance of cracks.