Cast irons contain 2 to 4 wt% carbon and 1 to 3 wt% silicon, with a wide range of elements used to control specific properties that make them suitable for use in engineering components. The widespread use of cast iron is a result of its low cost and versatile properties.
Integration of the ED core into the Zetium X-ray fluorescence (XRF) spectrometer sees two technologies, namely WD- and EDXRF, converging to make a unique and powerful analytical heart called SumXcore technology. It delivers unique benefits for metals applications, such as:
- Reduced measurement times
- Identification and flagging of unexpected elements in production
- Fast sample screening
- Spectrum archiving
This datasheet demonstrates the time savings achieved with SumXcore technology for the analysis of cast irons by XRF.
Instrumentation and software
Measurements were performed using a Zetium XRF spectrometer configured with 4 kW Rh-anode, SST R-mAX X-ray tube, the WD core, which is made up of the appropriate collimators, crystals and detectors for WDXRF analysis, and the ED core, which is a fixed EDXRF detector capable of capturing a complete EDXRF spectrum simultaneously with WDXRF measurements. All measurements were conducted using the state-of-the-art SuperQ software package.
Eight standards (CKD 232 – CKD 239) were used to set up the calibration for 24 elements. The elemental and compositional range is reported in Table 1. The standards were freshly surfaced prior to measurement with a Herzog grinding machine using 150 grit Al2O3 sandpaper.
Table 1. Elemental ranges and calibration results
One application was set up using the optimum combination of both technologies where certain elements were measured on the WD core while others on the ED core. This was done without compromising the analytical requirement for accuracy and precision. The measurement times for this combination are compared to a classical WD core-only setup in Table 2.
Table 1 contains the calibration details for the application. Calibration RMS and K factors are shown depending on the technology used to determine results
To determine the optimum combination of analytical conditions, such that the analytical performance remains uncompromised, a comparison between the WD core and ED core setups was made for all elements of interest. An example of this comparison is shown for Cr in Figure 1 which shows measured versus certified concentrations for both the WD core and ED core optical paths, for all standards used to set up the application.
This process resulted in an application where 14 compounds were measured using the WD core and 10 compounds were measured using the ED core.
Figure 1. WD core vs. ED core calculated Cr concentrations
Increased sample throughput
The ability to measure multiple elements with the ED core, while individual elements are measured on the WD core results in a 20 % time saving for every measurement, as shown in Table 2. In this case, the majority of saved time comes from the reduction in measurement time, however, there is a small contribution from the reduction in overhead time (i.e. the time required to change crystals, collimators filters, etc. in the WD core optical path). This overhead time can become a significant contributor, especially when large numbers of elements are being measured with widely varying conditions.
Accuracy and precision
Table 3 demonstrates the achievable accuracy and precision (repeatability) of the combined application when measuring a certified cast iron standard CKD 235. The results presented confirm the accuracy of the combined application, delivering concentration values close to the certified values. It can also be seen that the application delivers consistent results, with excellent repeatability values.
Table 2. Measurement times for the WD core and SumXcore applications
Table 3. Accuracy and precision of the SumXcore application (CKD 235)
The results clearly demonstrate that the combination of WD- and ED XRF incorporated in the Zetium spectrometer delivers faster measurement times for the analysis of cast iron. This increase in speed is achieved without a loss in analytical performance and the stability of the Zetium spectrometer ensures repeatability close to the theoretical limit. These two factors allow improved sample throughput, which is highly desirable in high-volume industries like cast iron. The ED core also has other advantages, such as fast sample screening, with or without Omnian, and identification and flagging of unexpected elements in process control.