Steel Analysis & Testing with XRF Spectrometry and Goniometry

Ferrous base materials are essential products worldwide as they are the foundation for various applications, including construction, automotive, and manufacturing. It is important to correctly evaluate these materials to ensure compliance with their chemical standards and enable high-quality, efficient manufacturing.

Irons

Various types of irons exist, each defined by its composition and application. They fall into two primary categories:

  • Hot metal, commonly known as pig iron, is the primary raw material used in steel production
  • Cast irons are used to make semi-manufactured items

Metallographically, white cast iron with a cementite structure differs from grey cast iron, which contains free graphite in laminae or nodules.

These make gray cast iron inhomogeneous and difficult to examine. Alloy cast irons contain alloying elements such as nickel, chromium, manganese, copper, etc., which improve hardness, corrosion resistance, and engineering qualities.

ARL X900 Simultaneous/Sequential X-ray Fluorescence Spectrometer

ARL X900 Simultaneous/Sequential X-ray Fluorescence Spectrometer. Image Credit: Thermo Fisher Scientific – Production Process & Analytics

Low Alloy Steels

This category includes steels used in various applications, including:

  • Steel castings, rails, axels, boiler and ship plates, automobile bodies
  • Girders, all kinds of bridge and structural sections
  • Wires, nuts, bolts, and forgings of any description
  • Springs, cutting steel

From a compositional standpoint, these steels are differentiated because the alloying elements often amount to <5–7%. The major alloying elements are typically present at less than the following concentrations:

Mn 2%; Cr 3%; Ni 5%; Cu 1.5%; Mo 1.5%; and V 1%

High Alloy Steels

Aside from iron and carbon, high alloy steels contain significant amounts of nickel, chromium, manganese, silicon, cobalt, tungsten, molybdenum, and vanadium.

This category includes stainless steels such as 18/8, austenitic, maraging, and martensitic, and forms of special stainless steels, tool steels, high-speed steels, and high-manganese steels.

Instrumental Parameters and Conditions

The Thermo Scientific™ ARL™ X900 XRF Spectrometer features a patented Moiré fringe goniometer. The unique friction-free positioning system ensures analytical speed, versatility, and reliability.

Up to nine crystals and four collimators can be installed. The two detectors (flow proportional and scintillation counters) allow for exact elemental analysis ranging from boron to californium.

The spectrometer can also handle up to 24 fixed monochromator channels in addition to the goniometer or up to 32 channels without a goniometer.

The ARL X900 XRF Spectrometer can be calibrated with commercially supplied certified reference material (CRM) standards or user-provided, well-analyzed samples.

While an XRF spectrometer is an accurate comparator, the accuracy of the final analysis depends on the quality of the calibration standards used and the care and reproducibility of sample preparation, which must be the same for CRMs and routine samples.

Typical Performance in Low Alloy Steel Samples Using the Goniometer

Table 1 summarizes the normal limits of detection (LoD). Calibration was performed using a set of international steel standards, approved goniometer settings for crystal, detector, and collimator, and a maximum power of 4200W.

Phosphorus was measured using two distinct crystals to compare their performance. If necessary, all elements from B to Cf can be studied. However, Table 1 only covers a subset of the most common elements tested in steels.

LoD is computed using the calibration curve for 10 and 100 seconds of counting time per element, respectively. As the goniometer measures one element after the other, it is generally advantageous to employ shorter counting durations to achieve a final result in a few minutes.

Table 1. Typical limits of detection in ferrous matrix for the goniometer at 10s and 100s counting time. Source: Thermo Fisher Scientific – Production Process & Analytics

        4200W LoDs 4200W LoDs
  Crystal Detector Collimator 10 s 100 s
Si PET FPC 0.6° 17.2 5.9
P PET FPC 0.6° 10.1 3.5
P Ge111 FPC 0.6° 5.6 1.9
V LiF200 FPC 0.15° 4.8 1.7
Cr LiF200 FPC 0.15° 8.1 2.8
Mn LiF200 FPC 0.15° 10.9 3.8
Cu LiF200 Scint 0.15° 9.7 3.4
Ni LiF200 Scint 0.15° 9.2 3.2
Mo LiF200 Scint 0.15° 4.7 1.6

 

Typical Precision Tests

The stability of an instrument represents the precision that may be achieved. Over one hour, two low alloy steel samples were subjected to a short-term repeatability test consisting of 11 runs.

At each run, all items were counted throughout a 10-second period. This test employed a power level of 2500W.

A long-term repeatability test of 18 measurements of a carbon steel sample over 60 hours was undertaken (Table 3). All elements were counted using a 10-second interval. The power level was set to 2500 W for this test.

The standard deviation over 60 hours is less than double that of a single hour. This is attributed to the ARL X900 WDXRF Spectrometer’s exceptional stability.

Table 2a. Sample 1—short term precision test over one hour using the goniometer at 2500 W—low alloy steel. Source: Thermo Fisher Scientific – Production Process & Analytics

Counting
time
10s 10s 10s 10s 10s 10s 10s 10s
Run # Cr Kα Cu Kα Mn Kα Mo Kα Ni Kα P Kα Si Kα V Kα
Crystal LiF200 LiF200 LiF200 LiF200 LiF200 Ge111 PET LiF200
Detector FPC Scint FPC Scint Scint FPC FPC FPC
1 1.902 0.259 0.577 0.871 0.907 1.402 0.0181 0.0209
2 1.902 0.256 0.573 0.874 0.902 1.401 0.0183 0.0209
3 1.907 0.258 0.574 0.873 0.903 1.413 0.0186 0.0222
4 1.909 0.258 0.575 0.873 0.904 1.412 0.0185 0.0232
5 1.905 0.258 0.575 0.874 0.902 1.406 0.0189 0.0222
6 1.901 0.256 0.576 0.873 0.904 1.398 0.0180 0.0226
7 1.903 0.256 0.576 0.877 0.900 1.406 0.0184 0.0228
8 1.909 0.257 0.580 0.870 0.904 1.407 0.0192 0.0224
9 1.909 0.259 0.580 0.873 0.903 1.406 0.0180 0.0223
10 1.907 0.256 0.572 0.875 0.902 1.408 0.0190 0.0233
11 1.901 0.256 0.575 0.870 0.901 1.400 0.0186 0.0222
Average % 1.905 0.257 0.576 0.873 0.903 1.405 0.0185 0.0223
% std
deviation
0.0034 0.0014 0.0024 0.0021 0.0018 0.0048 0.0004 0.0008

 

Table 2b. Sample 2—short term precision test over one hour using the goniometer at 2500 W—low alloy steel. Source: Thermo Fisher Scientific – Production Process & Analytics

Counting
time
10s 10s 10s 10s 10s 10s 10s 10s
Run # Cr Kα Cu Kα Mn Kα Mo Kα Ni Kα P Kα Si Kα V Kα
Crystal LiF200 LiF200 LiF200 LiF200 LiF200 Ge111 PET LiF200
Detector FPC Scint FPC Scint Scint FPC FPC FPC
1 2.695 0.365 0.1885 0.754 0.496 0.0413 0.667 0.1562
2 2.696 0.365 0.1875 0.753 0.498 0.0408 0.668 0.1564
3 2.699 0.361 0.1854 0.752 0.496 0.0401 0.666 0.1562
4 2.698 0.371 0.1874 0.752 0.500 0.0406 0.666 0.1552
5 2.697 0.368 0.1867 0.753 0.500 0.0412 0.669 0.1568
6 2.694 0.369 0.1873 0.750 0.493 0.0407 0.671 0.1576
7 2.700 0.371 0.1863 0.752 0.497 0.0406 0.670 0.1572
8 2.708 0.364 0.1865 0.752 0.493 0.0407 0.660 0.1566
9 2.699 0.370 0.1848 0.753 0.497 0.0409 0.665 0.1570
10 2.699 0.365 0.1861 0.750 0.497 0.0416 0.667 0.1564
11 2.706 0.363 0.1877 0.754 0.499 0.0414 0.671 0.1556
Average % 2.699 0.366 0.187 0.752 0.497 0.041 0.667 0.156
% std
deviation
0.0044 0.0033 0.0011 0.0014 0.0024 0.0004 0.0030 0.0007

 

Table 3. Long term repeatability over 60 hours using the goniometer at 2500 W—carbon steel. Source: Thermo Fisher Scientific – Production Process & Analytics

Counting time 10s 10s 10s 10s 10s 10s 10s 10s
Element—line Cr Kα Cu Kα Mn Kα Mo Kα Ni Kα P Kα Si Kα V Kα
Crystal LiF200 LiF200 LiF200 LiF200 LiF200 Ge111 PET LiF200
Detector FPC Scint FPC Scint Scint FPC FPC FPC
Run #1—July 19 2.706 0.363 0.1877 0.754 0.499 0.0414 0.671 0.1556
2—July 19 2.695 0.365 0.1885 0.754 0.496 0.0413 0.667 0.1562
3—July 20 2.705 0.364 0.1878 0.752 0.503 0.041 0.667 0.1582
4—July 20 2.695 0.368 0.1871 0.751 0.498 0.0407 0.667 0.1566
5—July 20 2.704 0.368 0.1879 0.752 0.499 0.0405 0.669 0.1555
6—July 20 2.701 0.365 0.1888 0.754 0.496 0.0407 0.669 0.1582
7—July 20 2.700 0.364 0.1871 0.749 0.498 0.0417 0.672 0.157
8—July 20 2.695 0.369 0.1872 0.750 0.496 0.0412 0.677 0.1576
9—July 21 2.703 0.368 0.1882 0.751 0.499 0.0416 0.674 0.1575
10—July 21 2.701 0.366 0.1889 0.749 0.499 0.0411 0.673 0.155
11—July 21 2.695 0.364 0.1877 0.747 0.499 0.0412 0.680 0.1566
12—July 21 2.695 0.364 0.1884 0.749 0.502 0.0407 0.682 0.1556
13—July 21 2.694 0.364 0.1878 0.752 0.496 0.0415 0.673 0.1561
14—July 21 2.697 0.367 0.1864 0.747 0.497 0.0414 0.678 0.1569
15—July 21 2.702 0.368 0.1878 0.748 0.498 0.0413 0.681 0.1551
16—July 22 2.700 0.367 0.1864 0.752 0.500 0.0415 0.675 0.1564
17—July 22 2.689 0.370 0.1871 0.752 0.495 0.0416 0.680 0.1561
18—July 22 2.693 0.367 0.1872 0.753 0.499 0.0410 0.677 0.1549
Average % 2.698 0.366 0.18767 0.751 0.498 0.0412 0.674 0.1564
% std
deviation
0.0047 0.0021 0.0007 0.0022 0.0021 0.0004 0.0050 0.0010

 

Conclusion

The ARL X900 Simultaneous-Sequential XRF Spectrometer allows for easy steel analysis. The Moiré fringe goniometer can analyze any element not fitted as fixed channels.

The goniometer analysis is performed concurrently with the measurement of the fixed channels. It can also serve as a backup if any of the fixed channels fail. Thermo Fisher Scientific offers complete calibrations for steel alloys, keeping the spectrometer’s commissioning time to a minimum.

These matrix types provide great precision for regular or R&D analysis, particularly when an innovative, high-counting fixed channel monochromator is utilized for elements such as Ni, Co, or Mo.

Thermo Fisher Scientific OXSAS Software, which runs on the latest Microsoft Windows®, simplifies operation.

For research use only. Not for use in diagnostic procedures. For current certifications, visit thermofisher.com/certifications. © 2024 Thermo Fisher Scientific Inc. All rights reserved. Windows is a register trademark of Microsoft Corporation. All other trademarks are the property of Thermo Fisher Scientific and its subsidiaries unless otherwise specified. PPA AN41425 09/24

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This information has been sourced, reviewed, and adapted from materials provided by Thermo Fisher Scientific – Production Process & Analytics.

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