Fig. 6. (a) B2 side of fracture surface from crack at B piece, (b) and (c) oxygen and Fe Auger signals at different positions on B2 fracture surface, and (d) oxide thickness evaluations: ‘‘cross’’ corresponding to O and Fe peak to peak line cross, and ‘‘half’’ corresponding to halfway of O peak to peak.

4. Service crack in segment A2
4.1. Section
    A segment of the pipe, known to contain SCC, was sectioned. The segment of steel pipe was about 30 mm in length. There were about 23 cracks in this cross section. The longest crack was about 0.8 mm, and the shortest was about 0.1 mm, so all the cracks were shallow. The cracks were intergranular and branched.
    Most of the cracks propagated almost vertically, and some cracks branched when they grew longer. The cracks were not very open.
4.2. Fracture surface
    Because the cracks were shallow, it was hard to break the section to open the cracks for SEM examination. A sliver 3 mm in depth was cut parallel to the pipe surface, and bent. Although there were many cracks in this piece, only two cracks opened allowing examination.
    Most of the crack surface was covered by an oxide film as for the crack surface of the SCC in segment A1. The exception was the crack tip region. The details of this crack tip region of the longer crack is shown in Fig. 7, and of the smaller crack is shown in Fig. 8. There was a narrow region of the crack tip front that was not covered by an obvious oxide film. It showed intergranular stress corrosion cracking. The crack tip front was next to a tearing surface as for the crack in segment A1.