Effect of the hydrobulging process on mechanical properties of spherical pressure vessels

This paper deals with the effect of large plastic deformation and angular deformation occurring during the hydrobulging process of polyhedral shells on mechanical properties. The results of the experiments show that strain ageing resulting from the plastic deformation causes increase of strength and decrease of plasticity and toughness of steel and its welded joints. The increasing or decreasing degree mainly depends on magnitude of the plastic deformation. The larger the plastic deformation, the more serious the unfavorable effect of the strain ageing. Appropriate heat treatment can eliminate the unfavorable effect and recover the mechanical properties to the original values.