RESIDUAL STRESSES AND FRACTURE PROPERTIES OF STRENGTH UNDER-MATCHED BUTT WELD JOINT MADE ON HSLA STEEL

摘要

The under-matched weld joints were adopted for producing a penstock made on 47 mm wall thickness and of 4200 mm diameter to improve the weldability. The isothermal Robertson wide plate test on the under-matched weld joints where the allowable stress level was 0.6 of the yield stress proved that the longitudinal stresses caused the crack propagation along the weld joint to deviate into tough base material where it is arrested. The arrest temperature was between -10 and -20°C. The behaviour of the crack propagation was the reason to omit the thermal stress relieving of the pipe sections and on circumferential weld joints executed at the site. One can always take into consideration the role of axial residual stresses when assessing whether to use or not under-matched weld joints in severe loaded structures.