Statistical Treatment of Slow Strain Rate Data for Assessment of HydrogenEmbrittlement in Low Alloy High Strength Steel

摘要

Slow strain rate testing has been used to quantify the degree of hydrogenembrittlement produced in high strength 4340 steel by plating processes and aircraft maintenance chemicals. The results of slow strain rate tests, conducted at a crosshead displacement rate of 2 x 0.0001 mm/s using samples of three notched tension specimens in various paint strippers, show that a mean fracture stress of 1850 MPa can be correlated with the pass/fail criterion for acceptability of paint strippers in an existing Standard Notched C-ring Test. Statistical analysis of the slow strain rate data allows criteria to be established which will ensure a 99% probability of identifying all paint strippers that fail the Notched C-ring Test. This analysis is also used to grade a series of products and processes in terms of their tendency to cause hydrogen embrittlement, and to identify environmental parameters that cause excessive scatter in hydrogen embrittlement tests. Criteria are also specified for acceptability of each heat treatment batch of 4340 steel specimens to ensure reproducibility of results obtained from slow strain rate tests. Keywords: Australia. (kr)