Internal Stresses in Thick Plates Weld-Overlaid with Austenitic Stainless Steel (Report 1) : Residual Stress Distributions As Welded

概要

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When weld overlaying is perfomed on a heavy section low alloy steel with strip electrode of austenitic stainless steel, problems such as a high residual stress due to difference of thermal expansion coefficient between the two metals and micro cracks during stress relief heat treatment occur. Hence, residual stress distribution of overlaid steel plate was determined. The obtained results are as follows : (1) Residual stress causes a high tension on the weld clad. It also causes compression at a point directly beneath the cladding. Compression is changed to tension as measuring points are distanced from the cladding point ; it is again changed to compression as measuring points approach the center of plate thickness, and it increases again at a point near the surface of parent material, showing very complicated distribution just like a damped wave. (2) An extremely high tensile stress develops at a point immediately below the weld bead junction. As it is obvious that internal stress at a point immediately below the cladding is changed from compression to a high tensile stress by locally heating the center portion of the cladding bead to approximately 700℃, it is clear that such an extremely high tensile stress occurs because the material is reheated by the subsequent welding heat. This range which reveals a peak of residual stress well corresponds to the range where under-clad cracking occurs.
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