Effect of Strain Aging on Mechanical Properties of High Strength Pipeline Steels with Different Compositions

The effect of strain aging on mechanical properties of high strength pipeline steels with three different compositions was investigated by using tensile test and impact test.The results show that with the increase of pre-strain and aging temperature,the tensile properties were degraded,which were characterized as the increase in strength and yield ratio decrease in elongation and the change of tensile curve from the round-house type continuous yield curve to the Luders extended curve.The addition of V and Nb could lower the content of free interstitial C and N atom in the steel,and the deterioration of tensile properties induced by the strain aging could be inhibited.The decrease in impact toughness after strain aging was caused by pre-strain,the impact toughness was improved by aging treatment and the V addition worsened the impact toughness of the steel.