INTRODUCTION
In continuation of previous work environmental and materials related parameters were studied influencing the SOHIC succeptability of line pipe steel. Steels according to API classification Grade 42 mainly differing in sulfur content and microstructure were tested with respect to the type and geometry of specimens (unmatched and notched 4-pointbentanddoublebeamspecimens; compact and hollow tensile probes), type of media (NACE TMO177-96/Solution A, water-rich TEG pipeline fluid; low chloride water), hydrogen sulfide partial pressure(0.1and 1.6MPa), and exposure mode (submerged inland filmed with the corrosive liquid). The results are used to recommend predictive experimental procedures to test and investigate the SOHIC susceptibility of steels. Experiments with hollow tensile probes allow hydrogen permeation measurements under mechanical loading and corrosive conditions. They proved to be a used tool to investigate environmental parameters detecting hydrogen embrittlement of steel, to quantity& the hydrogen uptake, and to define critical conditions for SOHIC.
SOHIC is a type of hydrogen induced stress corrosion cracking of low strength steel with the typical pattern of staggered small cracks formed approximately perpendicular to the principal stress (applied or residual) resulting in a ladder-like crack array. SOHIC has been observed in parent material of longitudinal welded pipes and in softened heat affected zones of welds in rolled plate steels as used for pressure vessels, e.g. inrei5neries3?4.
In recent years efforts have been made to find appropriate test procedures to identify the SOHIC susceptibility of steels *56.The aim was to find a test that is simpleton perform within a short exposure time and gives meaning~ predictive and service relevant results. In a previous paper the authors reported on their investigations to find experimental conditions suitable to study medium and materials related paremeters influencing the SOHIC susceptibility of steel. This work has been continued and extended with respect to the type and geometry of the loading mode, exposure mode, HJJ partial pressure and type of media. The results will be presented in this publication, and the service relevance of the information gained from different tests will be discussed.
