decisive parameter for the selection of API 5L steel pipeline for service in a hydrogen environment.

Steel welds representing 3 generations of pipeline carbon steel have been studied towards hydrogen result, making use of the fracture toughness parameter J integral that is a measure in the plastic do the job. The influence of hydrogen on the growth of a partial wall defect is studied and comparisons using the growth in the exact same defect in air are presented. The tests carried out had been three-point bending fracture toughness exams, in air and in a hydrogen natural environment simulated by electrolysis. Reduction in J0 was observed in all pipeline steel grades since the present density increases, which was much more pronounced in the base metal rather then within the heat affected zone. The various microstructures from the welded steels are observed and correlated for the reduction in plasticity. It is actually concluded that microstructure appears to be the decisive parameter for that collection of a pipeline steel for service in a hydrogen environment.



toughness remains large, the place most values are close to a hundred MPa?m1/2. Hydrogen has a much more
pronounced result on crack propagation resistance; dJ/da values measured in hydrogen gasoline can
be 90% lower than values measured in air or inert gasoline.
The fracture toughness measured in hydrogen gasoline is delicate to each the loading charge and gas
strain. Figure three.two.1.one exhibits the fracture toughness for X42 steel in 4 MPa hydrogen gas is
consistent at displacement charges from 3x10-5 to 3x10-4 mm/s but then increases by 30% as the
displacement charge increases to 3x10-3 mm/s [11]. Figure 3.two.one.2 displays the fracture toughness vs
hydrogen gasoline stress data for X42 and A516 steel from Table 3.2.1.1 [8, 9, 11]. For both sets of
data, fracture toughness decreases as gasoline pressure increases but seems to be approaching a
reduced limiting value. Fracture toughness values are greater for A516 in comparison to X42, but this
difference may well be due in portion on the higher loading charge for exams on A516.
Fracture toughness can rely sensitively on gasoline composition, as illustrated in Figure three.two.1.3
[6]. In this figure, fracture toughness measurements are shown for X42 and X70 steels in
nitrogen, methane, and hydrogen, too as mixtures of hydrogen, methane, carbon monoxide,
and carbon dioxide. The results for hydrogen and nitrogen are the similar data from Table three.two.one.1.
The data in Figure 3.2.one.3 display that methane does not adversely have an effect on fracture toughness,
having said that a mixture of methane and hydrogen leads to a reduction in fracture toughness.
Moreover, fracture toughness will not be degraded in gas mixtures containing hydrogen and carbon
monoxide. In these circumstances, carbon monoxide hinders hydrogen uptake in to the steel and precludes
hydrogen-assisted fracture [6], no less than about the time scale of your fracture toughness test.