Sulfide stress cracking (SSC) of a commercial Q345 pressure vessel steel in a wet H₂S environment

Abstract

The steel Q345 is extensively used in pressure vessels with low and medium pressure because of good mechanical properties and low cost. Good resistance to sulfide stress cracking (SSC) is required for the pressure vessel steel, but the SSC behavior of the Q345 has received little attention. This work investigated the SSC behavior of the Q345 in a wet H2S environment. The microstructure contained the irregular various-sized polygonal-like ferrite grains plus a carbon-rich degenerate pearlite banded structure. The Q345 had high ductility but failed to pass the SSC tests. The SSC cracking involved hydrogen embrittlement. The SSC preferentially occurred at the carbon-rich degenerate pearlite banded structure. The elimination of the carbon-rich degenerate pearlite banded structure is necessary to improve the SSC resistance of the Q345 pressure vessel steel.

Simultaneous Enhancement of Strength and Sulfide Stress Cracking Resistance of Hot-Rolled Pressure Vessel Steel Q345 via a Quenching and Tempering Treatment

“…Steel is one of the most commonly used materials for the production of pressure vessels [5][6][7]. Among those steels used for pressure vessels, Q345 steel, available in China, is a typical low carbon and low alloy hot-rolled steel with moderate yield and tensile strength that is extensively used in lowand medium-pressure vessels owing to its low cost (free of the precious alloy elements) and decent tensile strength (ultimate tensile strength (UTS) of ~470 MPa, yield strength (YS) of ~345 MPa) [8][9][10][11]. In the commercial use of the pressure vessel steel Q345 in harsh sour oil and gas environments containing hydrogen sulfide (H 2 S), the sulfide stress cracking (SSC) failure that is caused by the combined action of both the H 2 S and tension stress has gained considerable attention due to the possible resulting disastrous consequences.…”