Hydrogen Embrittlement Testing of Ultra High Strength Steels and Stampings by Acid Immersion
This standard describes a test method for evaluating the susceptibility of cold rolled and hot rolled Ultra High Strength Steels (UHSS) to hydrogen embrittlement. The thickness range of materials that can be evaluated is limited by the ability to bend and strain the material to the specified stress level in the specification.
Hydrogen embrittlement can occur with any steel with a tensile strength greater than about 1000 MPa, although some steel microstructures, especially those with retained austenite, may be susceptible at lower tensile strengths under the right conditions. The presence of available hydrogen, high stress levels and materials of high strength are considered the most at risk for hydrogen embrittlement.
Due to the specific conditions that need to be present for hydrogen embrittlement to occur, cracking in this test does not indicate that parts made from that material would crack in an automotive environment. Results from this test should be considered in conjunction with the strain state of the material and the operating environment of the part when selecting any UHSS. Since this test method is comparative, the most information can be gained if a control sample of known performance is evaluated along with the material being studied.
Rationale: Aggressive mass reduction targets for ground vehicles have lead to development of new generation of high strength steels. Very high tensile strength as well as presence of retained austenite as major micro-structural constituent can make these steels susceptible to hydrogen.