Effect of H_2/CO_2 partial pressure ratio on the tensile properties of X80 pipeline steel in the absence and presence of water

摘要

The exploitation of gaseous coal gas (CO, H_2, CO_2, H_2O, etc.) has been an important field in the current state of world economic development. The transportation of coal gas is one of the important respects in coal gasification industry. To ensure the safety transportation, the effect of H_2/CO_2 partial pressure ratio on the tensile properties of X80 pipeline steel in the absence and presence of water were investigated by slow strain rate test (SSRT) and scanning electron microscope (SEM) measurements in this paper. The results show that the tensile strength and elongation to failure of X80 pipeline steel in H_2/CO_2 atmosphere were deteriorated significantly. The relative tensile strength and plasticity loss of X80 pipeline steel increased with the increasing H_2/CO_2 partial pressure ratio in the absence of water. The increasing volume fraction of hydrogen gas is the key influencing factor in this condition. For the H_2/CO_2 environments in the presence of water, the relative tensile property loss decreased first and then increased with H_2/CO_2 partial pressure ratio. The probable reason is that the corrosion process changed gradually from CO_2-dominant to H_2-dominant. Water played a significant role in the tensile property damage of X80 pipeline steel in the H_2/CO_2 environments.