Properties of stainless steels for fusion conductor jackets and their manufacturing techniques

A superconducting cable for a fusion magnet has to be reinforced by a stainless steel jacket which envelops the cable. The jackets are fabricated by extruded and butt welded steel sections or by composing the jacket from drawn sections with longitudinal welds. Fatigue life and fatigue crack growth rates (FCGRs) were investigated at 10 K for embedded and surface cracks for the candidate material 316LN. Embedded cracks are more severe than surface cracks. The FCGR of weldments is low compared to their base metals, and the residual stresses are responsible for these results. In the range 20 K-7 K, the FCGR of surface cracks is lower than that of cracks propagating from a buried penny-shaped crack.<
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