1986 Volume 4 Issue 1 Pages 95-101
The stress relief phenomena in pre-loading on butt welded plates and the changes of material properties owing to the pre-loading were investigated theoretically and experimentally. A over-matching welded joint composed of a 50kgf/mm2 class weld metal by automatic CO2 welding and a mild steel of 16 mm thickness was tested.
The strain distributions measured by strain gages showed the same tendency to those calculated by FEM, under pre-loadings in directions perpendicular and parallel to the weld line. The perpendicular loading was superior to the parallel loading in terms of reducing the plastic strains caused of the stress releaving.
Strain aging embrittlement of weld metal, HAZ and base metal obtained by 2 mm V notched Charpy test was quite proportional to prestrain, and significant difference among them could not be found. The equations for estimation of the brittle fracture initiation temperature were checked. The rise in the temperature caused by the pre-loading was less than that due to the weld residual stress. It was concluded that the effective pre-loading method recommended in the present paper was sufficiently safe.