Prestudy on the susceptibility of P460QL steel to hydrogen-assisted cracking

The susceptibility of P460QL micro-alloyed steel to hydrogen-assisted cracking (HAC) was studied under constant gas charging conditions. Specimens for microstructure analysis and 13 mm-thick compact tension (CT) specimens for fracture mechanics tests were wire-cut from a hot-rolled and tempered steel plate. The microstructure was analyzed using light optical microscopy (LOM) and scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). The CT specimens were pre-cracked by cyclic tensile loading, and each specimen was loaded according to the constant displacement method by using a wedge. The actual stress intensity factor at the crack tip was calculated based on experiments and finite element analysis (FEA). The wedge-loaded CT specimens were stored for 1000 hours inside an autoclave filled with pure hydrogen gas at the pressure of 200 bar at room temperature. As HAC did not occur at the stress intensity factor of 67 MPam 0.5 , the P460QL micro-alloyed steel with the thickness of < ½ inch (< 13 mm) can be considered as suitable for applications under the conditions investigated.