Effect of Strain Aging on Properties of X90 Line Pipe

Tensile and impact toughness test on X90 line pipe with different aging conditions were conducted to study the effect of aging conditions on properties of X90 pipeline steel. The result shows that yield strength and yield ratio of X90 line pipe would increase significantly with the introduction of strain aging, while the impact toughness and tensile strength have little change. The impact toughness of X90 line pipe would decrease with the introduction of 200℃, 5min aging. However, the impact toughness of X90 pipeline would increase with the increase of aging temperature and aging time (250 ℃, 1h). The tensile strength of X90 pipeline steel would decrease or increase slightly after the introduction of aging. While the yield strength and yield ratio would increase significantly after the introduction of aging, and the rising range of yield strength and yield ratio would decrease with he increase of aging temperature and aging time. Comprehensive analysis shows that the aging treatment have different effects on different X90 pipeline steel, mainly due to different microstructure and chemical composition of X90 pipeline between manufacturers during the trial production. The result of aging sensitive coefficient analysis shows that the effect of microstructure type is more significant than that of chemical composition, and X90 pipeline steel with dual-phase microstructure would has high aging sensitivity coefficient.