1969 Volume 38 Issue 10 Pages 1116-1123
For purposes in evaluating the elastic and plastic behaviors of weld zones, tensile tests and alternating plane bending tests beyond the elastic range were carried out on the transverse-weld specimens of a 80 kg/mm2 class heat-treated high-strength steel, and the individual stress-strain curves for the weld metal, heat-affected zone and base metal were observed in detail. The strain was measured with electric-resistance strain gauge of 1 mm gauge-length sticked on each zone. Also, these curves were compared with those examined on the quenched or and tempered specimens of the base metal. The tests revealed the following:
The over-heated zone, which exhibited high hardness and low ductility, began to yield gradually at considerably small stress as against the abrupt yielding of the base metal, the 0.02% offset elastic limit of the zone being about half of the yield point of the base metal. This low elastic limit again resulted in oilquenched specimens, whose microstructures were similar to that of the over-heated zone in the weld.
In the cyclic bending each stress-strain hysteresis loop for the weld metal, softened zone and base metal widened with decrease in elastic limit as cycling continued, while the loop for the over-heated zone became rather narrow due to strain hardening in similar way for the quench-hardened base metal.