Wavelength-dispersed X-ray fluorescence analysis of low alloy steel

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Alloy steels containing up to 4-8% alloying elements are known as low alloy steels, which are made by adding different elements in order to improve a specific property of the steel such than hardenability. Electric furnaces are generally used for the production of alloy steel. During the steelmaking process, the concentrations of added elements in molten steel are changed. Therefore, it is necessary to quickly analyze the elemental composition in order to effectively control the steel making process.

Quality control of the steelmaking process also requires analyzes of raw materials and slag. For this purpose, X-ray fluorescence spectrometers are commonly used due to their ability to make precise and fast measurements of both bulk metal and powders. This paper demonstrates the ability of Rigaku’s ZSX PrimusIII + Wave Dispersion X-ray Fluorescence Spectrometer (WDXRF) ZSX PrimusIII + to analyze low alloy steel for optimized process control.

ZSX PrimusIII + WDXRF spectrometer

The ZSX PrimusIII + features a tube above the optics so that the x-ray tube can be placed over the sample, reducing the risk of instrument damage or contamination caused by breaking the pressed pellet samples inside the spectrometer during measurement or transport to the measurement position. The ZSX PrimusIII + is suitable for the steel industry where analyzes of bulk metal and powder samples are performed as part of the process control procedure during alloy steel production.

ZSX PrimusIII + WDXRF spectrometer

The system software is built on Rigaku’s Flowbar interface, which allows operators to improve and perform measurements through a sequence of step-by-step procedures. Another software innovation from Rigaku is “EZ Analysisâ€, which greatly facilitates analysis setup and sample measurement. In addition, the software offers different types of statistical process control functions suitable for the steel industry.

Preparation of standards and samples

Calibration was established using NIST and Japan Steel Standard certified low alloy steel standard reference materials. The 80 grit corundum sandpaper was used to polish the samples and the aluminum analysis was performed using the 80 grit SiC sandpaper to avoid contamination by the corundum paper.

Measurement and calibration procedure

The ZSX Primuslll + with a 3 kW Rh target x-ray tube was used to perform the measurements. For all the elements, the measurement of Kα_line was taken at the counting time of 20 seconds. A LiF analysis crystal (200) and the scintillation counter were used for all heavy elements, ranging from V to Mo. A PET crystal was used for Al and Si, while an optional Ge was used. in order to obtain a high resolution measurement of S and P. For all light elements, a proportional gas flow meter was used.

Results

From the data, representative calibration curves are plotted as shown in Figures 1-9. An overlap correction was made in the S and P calibration in order to correct for the Mo overlap, as shown in the figures. 3 and 4.

Si calibration curve

Figure 1. Si calibration curve

Mn calibration curve

Figure 2. Mn calibration curve

S calibration curve

Figure 3. S calibration curve

P calibration curve

Figure 4. P calibration curve

Ni calibration curve

Figure 5. Ni calibration curve

Calibration curve of Cr

Figure 6. Calibration curve of Cr

Mo calibration curve

Figure 7. Mo calibration curve

Cu calibration curve

Figure 8. Cu calibration curve

Al calibration curve

Graph 9. Al calibration curve

Table 1 lists the precisions of the calibration curves, while Table 2 shows the repeatability of the test results (10 times).

Table 1. Accuracy of calibration curves

Making up Concentration range Precision
Yes 0.008 – 0.732 0.0077
Mn 0.0057-1.59 0.0097
P 0.0025 – 0.044 0.0009
S 0.0045 – 0.041 0.0009
Or 0.041 – 4.1 0.0060
Cr 0.0072 – 3.08 0.016
Mo 0.005 – 1.25 0.0067
Cu 0.0058 – 0.51 0.007
V 0.0006 – 0.4 0.0031
Al 0.0007 – 0.24 0.0097

Table 2. NIST1261 repeatability result

Making up Mean Dev. RSD%
Yes 0.22 0.00077 0.35
Mn 0.67 0.00075 0.11
P 0.0144 0.00026 1.81
S 0.0173 0.00016 1.00
Or 2.01 0.0022 0.11
Cr 0.70 0.00094 0.13
Mo 0.194 0.00038 0.19
Cu 0.045 0.00041 0.90
V 0.0111 0.00015 1.39
Al 0.0118 0.00054 4.54

Conclusion

The results demonstrate the ability of the ZSX PrimusIII + to accurately and quickly analyze low alloy steel elements. The spectrometer can also be used for the precise and reliable analysis of high alloys such as nickel alloy and stainless steel. It is optimized for the control of steel production processes, including analyzes of ferroalloys and slag.

This information was obtained, reviewed and adapted from documents provided by Rigaku.

For more information on this source, please visit Rigaku.

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