Cast iron is a family of ferrous metals with a wide range of properties that are produced by being cast into shape instead of being machined. Cast iron contains 2 to 4 wt% carbon and 1 to 3wt % silicon, but a wide range of elements are used to control specific properties. Cast iron has a wide range of mechanical properties, which makes it suitable for use in engineering components. The wide spread use of cast iron is a result of its low cost and versatile properties. This data sheet demonstrates that the Epsilon 4 – a benchtop energy dispersive X-ray fluorescence (EDXRF) spectrometer – is capable of quantifying 11 elements in cast iron, including carbon.
Measurements were performed using an Epsilon 4 EDXRF spectrometer, equipped with a 15W, 50 kV rhodium (Rh) anode X-ray tube, 6 software selectable filters, a helium purge facility to improve the light-element performance, a high-resolution SDDUltra silicon drift detector, a sample spinner to obtain more homogeneous results, and a 10-position removable sample tray for automated analysis.
Standards and sample preparation
Eight certified reference materials (CRMs) from MBH (CKD 232 – CKD 239) were used to set up the calibrations for C, Si, P, S, Ti, V, Cr, Mn, Ni, Nb and Mo in cast iron. The standards were freshly surfaced with a Herzog grinding machine using 150 grit Al2O3 sandpaper prior to measurement.
Four different measurement conditions were used, each one optimizing the excitation of a group of elements (see Table 1). Carbon, phosphorus and sulfur were analyzed using a region of interest (ROI). The total measurement time per standard/sample was 13 minutes.
Table 1. Measurement conditions
Figures 1, 2 and 3 show calibration graphs for carbon, phosphorus and molybdenum, respectively. The graphs show very good correlation between the certified concentrations and the measured intensities. The SDDUltra detector contributes largely to the improved light-element analysis capabilities, making it possible to quantify carbon, something not normally considered possible with bench-top EDXRF spectrometers. Detailed calibration results for all analyzed elements in the cast iron standards are listed in Table 2. The RMS (root mean square) value equals 1 sigma standard deviation. The lower limit of detection (LLD) for carbon in cast iron is estimated at 0.15 wt % in 10 minutes measuring time.
Table 2. Calibration details
Accuracy and precision
To test the instrument accuracy and precision, one cast iron standard (CKD 235) was measured 20 times consecutively and the average concentration was compared to the certified concentration (see Table 3). All elements show very accurate results. Except for titanium and nickel, all elements show a relative RMS of better than 3 %.
Table 3. Repeatability results
The results clearly demonstrate the excellent capability of Epsilon 4 for the analysis of C, Si, P, S, Ti, V, Cr, Mn, Ni, Nb and Mo in cast iron. Excellent results have been obtained for the calibrations and accuracy test. Furthermore, the repeatability of the measurements demonstrate that the Epsilon 4 is an ideal instrument for quality control of cast iron. The high resolution and outstanding sensitivity of the SDDUltra silicon drift detector combined with powerful software deconvolution algorithms make it possible to quantify even carbon in cast iron.