Analysis of major and minor elements in cast iron

Introduction This application note shows that the Epsilon 4 – a high- performance energy dispersive X-ray fluorescence spectrometer - is capable of analyzing major and minor elements in cast iron samples.

Application background The term cast iron usually refers to gray cast iron, but can mean any of a group of iron-based alloys containing more than 2% carbon (alloys with less carbon are carbon steel by definition). It is made by re-melting iron, often together with substantial quantities of scrap iron and scrap steel, and by taking various steps to remove undesirable contaminations such as phosphorus and sulfur, which weaken the material. The effect of sulfur is balanced by adding manganese to the melt. The silicon content is adjusted to the desired level from 1 to 3% depending on the application.

Also other elements are added into the melt before casting produces the final form. In general, cast iron samples may be regarded as being composed of a variety of major and minor elements, such as Mn, P, S, Si, Cu, Ni, Cr, Mo, Ti and V. In this study majors and minors were measured to show the capabilities of the Epsilon 4.

Instrumentation Measurements were performed using an Epsilon 4 spectrometer, equipped with a 10W, 50 kV rhodium anode X-ray tube, 6 filters, a helium purge facility, a high-resolution silicon drift detector, a spinner and a 10-position removable sample changer.

Sample preparation The cast iron standards and samples were prepared for analysis by grinding with 60 grit aluminium oxide sand paper.

Measurement procedure Eight standards from Brammer Standard Company (TX, USA) were used to set up calibrations for the 12 major and minor elements. Three different measurement conditions were used, each one optimizing the excitation of a group of elements. These measurement conditions are given in Table 1. The total measurement time per sample was 4 minutes.

Table 1. Measurement conditions

Figure 3. Calibration plot of P in cast iron and Figure 4. Calibration plot of S in cast iron

Accurate calibration results Figures 1 to 4 show calibration plots for Si, Mn, P and S in cast iron, respectively. These plots show a good correlation between the certified concentrations and the calculated concentrations. Detailed results are listed in Table 2.

Precision To test the analytical precision of the instrument, one cast iron sample was measured 20 times consecutively, using the conditions given in Table 1. The average concentration, the absolute RMS (1 sigma standard deviation) and the relative RMS are expressed in Table 3.

Table 2. Calibration results

Table 3. Results of the repeatability test

Conclusion The results clearly demonstrate that the Epsilon 4 EDXRF spectrometer is suitable for the analysis of major and minor elements in cast iron. Accurate and repeatable results are obtained in just 4 minutes.

Analysis of major and minor elements in cast iron

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