IMPROVEMENTS RELATING TO METHODS OF MAGNETIC FLAW DETECTION

摘要

1293798 Testing for flaws K HONJO 24 Oct 1969 52245/69 Heading G1S [Also in Division H1] Flaws are detected in ferromagnetic metallic materials by use of a flaw-detecting material composed of a polymeric binder, particulate iron or iron oxide, a non-magnetic colouring agent and a surface-active agent. The composition can be applied to an object as a paste or as particles dispersed in water. When an electric current is applied to the object, the particles adhere along the line of any flow. The ferromagnetic particles may be carbonyl iron, reduced iron or electrolytic iron dust, black iron oxide or red iron oxide. Spherical particles of carbonyl iron (3-6Á dia.) are preferred. Specified colouring agents are chrome yellow, chrome red, titanium white, rhodamine B, and fluorescent pigments such as 9, 10-dianilino-anthracene and 2- hydroxy-1-napthaldazine. The binder may be a cellulose derivative, a thermoplastic e.g. PVC, or a thermohardening resin such as epoxides, polyurethanes, butyrated melamine or butyrated urea. Relative proportions may be: magnetic particles 15-75%; colouring agent 5-50%; binder 10-40%. Specified surface-active agents are alkyl sulphonates, alkyl sulphates, alkylbenzene sulphonates or sulphosuccinate, aminoacid salts, polyalkylene glycols, ethylene oxide adducts, and alkyl phenol ethylene oxide adducts. The flawdetecting compositions may be made by kneading the active ingredients together with a solvent e.g. a ketone. Further solvent may be added after evaporation of a first portion of solvent. The surface-active agent may be added as an aqueous solution.