November AMP_Digital

FEATURE A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 1 9 6 2 (continued from page 10) be different at other positions. After appropriate calibration using a representative sample, it is possible to assess correct SHD by correlation. This illustrates the influence of impedance contrast and grain shape on backscattering intensity. Core grain size is nearly the same average size as the grain size of the mar- tensitic case. However, while the case does not scatter, the core does. APPLICATIONS Manual, semiautomatic, and automated multichan- nel systems are available. The manual device consists of a four-channel ultrasonic board controlled by a software pack- age for program settings, signal processing, reporting, and general quality assurance (QA) requirements. The compo- nents are assembled into an industrial notebook designed for use in rough industrial environments. For example, Q Net Engineering’s probe systems enable testing of complex shaped components. The wedge of the probe system is adapted to the geometry of the required test position. For SHD values larger than 1.5 mm, rough technical surfaces are available that enable control before machining. ~HTPro Note: The authors acknowledge the cooperation of Fraun- hofer Institute for Nondestructive Testing, Saarbruecken, Germany. For more information: Mike Bogaerts, CNH Industrial, Wil- mardonksteenweg 32, 2030 Antwerp, Belgium, mike.bo- gaerts@cnhind.com , www.cnhindustrial.com. References 1. Steel—Determination of the Thickness of Surface- Hardened Layers, ISO 18203:2016, International Organi- zation for Standardization. 2. C. Zhang, Assessment of Depth of Case-Hardening in Steel Rods by Electromagnetic Methods, Graduate Theses and Dissertations, Iowa State University, 2009. 3. K. Goebbels, Structure Analysis by ScatteredUltrasonic Radiation, Research Techniques in Nondestructive Testing, Vol 4, 1980. 4. V.A. Shutilov, Fundamental Physics of Ultrasound, Gordon and Breach, Amsterdam, ISBN 2-88124-684-2, 1988. 5. A. Fiedler, Einfluss des Werkstoffzustandes auf das Wärmebehandlungsergebnis beim Induktiven Rands- chichthärten, Dissertation, TU Darmstadt, 2013. 6. M.J. Schneider and M.S. Chatterjee, Introduction to Surface Hardening of Steels, Steel Heat Treating Fundamentals and Processes, Vol 4A, ASM Handbook, J. Dossett and G.E. Totten (editors), 2013. 12 INVESTIGATING AN ANOMALY IN AN INDUCTION HARDENED WHEEL SHAFT Situation Duringinductionhardening,anunexpectedreddiscolorationwas observed in the face area next to the R8 radius of a flangedwheel shaft usedinatractorrearaxle(Fig.A).Typically,thiscolorationoccursfurther away fromthis radius (toward the flange). Thematerials labwas asked to check the case depth in this critical area using a P3123 NDT tester (Fig. B) to determine whether the case depth was in spec. Results and Remedy Testing showed that the case depth was too low (4.2 to 4.3 mm) versus the minimum specified case depth of 6 mm. This required that all induction hardened parts processed prior to the discovery (140 parts) be put on hold while conducting a complete check of the case depth. All shafts hardened since the discovery were checked, starting with the last parts hardened. For all incorrect shafts, the case depth in the radius was only 4.2 to 4.3 mm, and all were induction hardened on the left-hand spindle in a two-spindle IH machine. Case depth was alsomeasured by generating amicroindentation hardness profile in the hardened flange area, showing a case depth of 4.55mm. This corresponds with the expected difference (between 0 and 10%) between ultrasound measurements with the P3123 and hardness measurements. Corrective action was taken including additional op- erator training. Fig. A— Unusual red discoloration in the radius/ face area of flanged wheel shaft, indicating a possible problemwith the induction hardening process. Fig. B— NDT measurement of the case depth in the radius area.