NDT characterization of decarburization of steel after long-time annealing

Decarburization is a common adverse effect at manufacturing and processing of steel semi--products.A series of samples of various shapes, produced from spring steel 54SiCr6 (CSN 14260), was prepared and annealed at 800 • C at air atmosphere for 1, 4, 8, and 20 h.The decarburized layers that appeared on the surfaces were examined metallographically and magnetically by Magnetic Adaptive Testing (MAT).The magnetic tests proved an appreciable sensitivity, which depended on the samples shapes, on the way of measurement and on the surface treatment of the samples before the measurement.Careful weighing of the samples before and after the annealing and/or after the surface treatment proved to be a simple and reliable way for determination the thickness of the decarburized layer as well. K e y w