This general category of cast materials includes many applications suitable for ultrasonic thickness gaging. Cast metal parts come in a wide range of geometries and compositions.
Because most castings scatter ultrasound rapidly, the maximum thickness that can be measured is often limited. In general 4 in. (100 mm) is about the upper limit, although in some cases it is possible to measure up to 10 in. (250 mm). Poor surface conditions, large grain size, and sound velocity variations usually account for calibrated accuracies of ±0.002 to ±0.005 in. (±0.05 to ±0.125 mm). Thin aluminum castings may be measured with an calibrated accuracy of ±0.001 in. (±0.02 mm), but thick cast stainless steel usually is limited to not better than ±0.010 in. (±0.25 mm) accuracy.
Equipment: Two Olympus precision gage models are commonly recommended for cast metal applications: model 38DL PLUS with the High Penetration software option, and 45MG with the Single Element High Penetration option. Transducer selection and gage setup will depend on the material and thickness range being tested. Common choices include M1036 (2.25 MHz) and M109/M110 (5 MHz), with lower frequency transducers such as the 0.5 MHz M101 being used on very thick or coarse grained castings.
For the detection of subsurface porosity, cracks or inclusions, we also offer a complete line of fully digital ultrasonic flaw detectors.
For further discussion of this subject, see also our application note on Ultrasonic Testing in the Foundry Industry.