RESEARCHINTO THE RESISTANCE TO HYDROGEN EMBRITTLEMENT OF STRUCTURAL STEEL WEELDS USING THE NACE-TEST AND CORROSION ELONGATION CURVES

摘要

Welds on two types of structural steel were tested according to the NACE standard TMO177-90 in order to determine their resistance to hydrogen embrittlement. Under the test conditions prescribed by standard a sulphide stress cracking process is reproduced, in which hydrogen induced cracking (HIC) occurs. The results of the tests showed that the thermally affected zone (HAZ), with its typical microstructural constotuents, reacted very strongly to the action of the absorbed hydrogen. In the continuation of the research work it was found, by means of measurements of so-called "corrosion elongation curves", that brittle zones occur in the HAZ. Due to the constant penetration of hydrogen to these location, as well as the stresses in the material, microcracks occur, which coalesce into larger cracks, and a fast chain reaction is initiated. The cracking process, i.e the chain reaction, is an exceptionally rapid one, lasting less than 1 minute. As a result, no tertiary region is visible on tje corrosion elongation curves.