Steel articles internal defects detection - after exposed surface treatment with citric and sulphuric acids and ammonium persulphate

摘要

This rapid, sure, simple and economical method is suitable for detecting defects present at the examined surface of a steel material, e.g. sulphur-band, crevices, alumina clusters and other defects attributable to some inclusions. A dilute solution of ammonium persulphate, sulphuric acid or citric acid, ora mixed dilute solution of citric acid with ammonium persulphate or sulphuric acid is contacted with metal subjected to surface-exposing treatment. The oxidation reaction with the defects present at the examined surface undergo is accelerated and there appear oxidation patterns (after a few seconds to few minutes). These can be observed with the naked eye, by use of oxide-splitting off print, taking a photograph, etc. When internal defects are examined by cold chisel test, ultrasonic detection of scraches and magnetic detection of scraches, the desired spots can be exactly predicted. Thus, complicated work required for making samples is markedly simplified.