Abstract
In this report, researches on hydrogen embrittlement of iron and low strength steels are reviewed. The characteristic features of the fracture due to hydrogen embrittlement of commercial steels, the influnce of hydrogen on the plastic deformation and fractographic approaches are discussed. Recent progress of the studies has made possible to get the solution for some important problems and to understand the kinetics of hydrogen embrittlement. Its mechanism is, however, still under the discussion. Further researches especially giving the direct evidence are needed. As the fracture process of hydrogen embrittlement depends on the conditions such as hydrogen charging, stress conditions, temperature of testing, etc., it may not be explained with a unique mechanism.