Effect of Cooling Rate on Sulfide Stress Cracking Resistance of a Q345 Pressure Vessel Steel Subject to Hydrogen Sulfide

Abstract

As an important equipment for the separation, store, and transport of the oil and natural gas in energy industry, the pressure vessels are subjected to harsh service environments of sulfide stress cracking (SSC). In this work, the effect of the cooling rate on the SSC susceptibility of a Q345 pressure vessel steel is studied. A pronounced distinction in microstructure is presented as the cooling rate is increased from ≈1 to ≈15 °C s−1. At ≈1 °C s−1, the microstructure is consisted of polygonal‐like ferrite and distinct banded pearlite. At ≈5 °C s−1, the microstructure is consisted of polygonal‐like ferrite and faintly banded pseudo‐pearlite. At ≈15 °C s−1, the microstructure is acicular ferrite with a complete elimination of banded structure. The cooling rate decides the level of the banded structure. As the cooling rate increases, the banded structure becomes relatively slight and even disappears. Strength in sort ascending is ≈1, ≈ 5, and ≈15 °C s−1. The SSC failure happens at ≈1 and ≈5 °C s−1, while does not happen at ≈15 °C s−1. The strength is not the only dominant factor responsible for the SSC failure. The SSC is preferentially generated at the banded structure. The elimination of the banded structure is necessary to improve the SSC resistance of the Q345 pressure vessel steel.

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

“…Generally, cooling rate route in rolling schedule is targeted to produce the desired microstructure, which is much preferred because of its effectiveness in controlling the microstructure and its economical nature. As aforementioned, 21 different cooling rate after the final rolling caused different phase transition, resulting in different microstructure. The cooling rate decided the level of the banded structure.…”

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.…”