Method of detecting inhomogeneities by the use of mixtures of fluorescent and visible dye-colored magnetic particles

Abstract

Abstract A method using a mixture containing both fluorescent and visible dyed magnetic particles for detecting inhomogeneities in metal workpieces. The formation of adherent accumulations of the magnetic particles at localized areas where a magnetic leakage field occurs provides indications of the existence of surface or subsurface discontinuities or the like in magnetizable workpieces. The fluorescent indications are initially detected under ultraviolet, or black light, and are rendered visible under white light by the application thereto of a solvent for the visible dye to cause bleeding thereof. Preferably, the solvent contains a light-colored pigment suspended therein to afford a contrasting background for the visible color indication, and also contains a thickening agent, resin or the like to increase the viscosity of the solvent and thereby limit the extent of bleeding of the visible dye. Compositions comprising mixtures of the respective fluorescent and visible dyed particles are applied to the surface undergoing test either in dry powdered form or in the form of suspensions of such particles in a common liquid vehicle that is a nonsolvent for the particles and also for the visible dye associated with the visible dyed particles. The visible color indications formed by the subsequent application of a solvent for the visible dye, and consequent bleeding of the visible dye enable operators to carry out under ordinary, or white light, whatever scarfing or other treatment is required to remove the surface discontinuity from the workpiece or to compensate for it.

Inventors

• 👤 Keith M Van Kirk
• 👤 Kenneth P Borrows

Bibliographic Details