STP1245: Mitigation of Harmful Effects of Welds in Zirconium Alloy Components

    Coleman, CE
    Research scientists, Atomic Energy of Canada Ltd., AECL Research, Chalk River Laboratories, Chalk River, Ontario

    Doubt, GL
    Research scientists, Atomic Energy of Canada Ltd., AECL Research, Chalk River Laboratories, Chalk River, Ontario

    Fong, RWL
    Research scientists, Atomic Energy of Canada Ltd., AECL Research, Chalk River Laboratories, Chalk River, Ontario

    Root, JH
    Research scientists, Atomic Energy of Canada Ltd., AECL Research, Chalk River Laboratories, Chalk River, Ontario

    Bowden, JW
    Research scientists, Atomic Energy of Canada Ltd., AECL Research, Chalk River Laboratories, Chalk River, Ontario

    Sagat, S
    Research scientists, Atomic Energy of Canada Ltd., AECL Research, Chalk River Laboratories, Chalk River, Ontario

    Webster, RT
    Metallurgical consultant, Scio, Oregon

    Pages: 21    Published: Jan 1994


    Abstract

    Welding produces local residual tensile stresses and changes in texture in components made from zirconium alloys. In the heat-affected zone in tubes or plates, the basal plane normals are rotated into the plane of the component and perpendicular to the direction of the weld. Thin-walled Zircaloy-2 tubes containing an axial weld do not reach their full strength because they always fail prematurely in the weld when pressurized to failure in a fixed-end burst test. Reinforcing the weld by increasing its thickness by 25% moves the failure to the parent metal and improves the biaxial strength of the tube by 20 to 25% and increases the total elongation by 200 to 450%. In components made from Zr-2.5Nb, the texture in the heat-affected zone promotes delayed hydride cracking (DHC) driven by tensile residual stress. Although the texture is not much affected by heat-treatments below 630°C and large grain interaction stresses remain as a result of mixed textures, macro-residual tensile stresses can be relieved by heat treatment to the point where the probability of cracking is very low.

    Keywords:

    welds, heat-affected zone, burst strength, delayed hydride cracking, residual stress, post-weld heat treatment, zirconium, zirconium alloys, nuclear materials, nuclear applications, radiation effects


    Paper ID: STP15194S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP15194S


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