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XRF Analysis of Carbon Steel (9 replies)

11 months ago
JohnnyD 11 months ago

If I was looking to buy an XRF to read and analyze and measure carbon percentage %C in steel?  What machine should I look at buying?

Tony Verdeschi
11 months ago
Tony Verdeschi 11 months ago

Do you currently have an XRF instrument ? In general you can measure C in steel by WDXRF if you have a very flat surface, either milled or polished, on the sample. Your instrument would need to have a multilayer analyzing crystal specifically for measuring C. Most vendors offer these types of crystals. If you currently do not have a WDXRF, The cost of acquiring an instrument specifically to do this would be well outside your stated budget. If you just need to add an analyzing crystal to an exquisite instrument it might be within your budget. Sample preparation is really the key for this type of analysis as your escape depth for CK alpha radiation is only a few microns.

WDXRF prices range in pricing a lot depending on models and options but in general I would guess you would be looking at something in the 150-300K range

Bill Fraser
11 months ago
Bill Fraser 11 months ago

Combustion with infrared detection is a tried and true method, and the cost of the instrument would be much less than an XRF. Additionally, detection limits are much better given the low fluorescent yield of the light elements. You will want to check out instrument manufacturers such as Leco.

David Kano
11 months ago
David Kano 11 months ago

The XRF and the combustion with infrared detection as as well as a few other instruments such as Optical Emission and LIBS are capable of doing the carbon in steel but all of these are well above your budget. I agree that the combustion / infrared will be much lower but still more than you have allocated.

If the required test frequency is relatively low and you can afford the waiting time perhaps there is a commercial testing laboratory in your area that can do the analysis for you.

Tony Verdeschi
11 months ago
Tony Verdeschi 11 months ago

Yes if carbon analysis is your only goal. If you are looking at using XRF for quality control of the chemical composition of all of the elements present in the steel, which is a common XRF application, and C is an additional need then the XRF might make sense.

Alan Carter
11 months ago
Alan Carter 11 months ago

I don't know of an instrument for carbon analysis that is within your budget. A Leco C/S analyzer with an induction furnace would be the way to go, at a cost of ~$80 K USD - with autoloader. Otherwise, using an outside lab, as suggested is another option.

Bob Mathias
11 months ago
Bob Mathias 11 months ago

Two types of XRF. EDX is not reliable to detect low concentration of carbon and WDXRF is way over your budget. Combustion is still the way to go at steel mill where they need to measure very low carbon concentration. On the other hand if your carbon range is more than 0.005, you can go for an entry level Optical Emission Spectrometer also known as Spark Spectrometer. Should be around US25k.

  1. WDXRF around US$200k
  2. EDX around US40k
  3. Carbon Sulfur Analyzer about US50k

John Koenig
11 months ago
John Koenig 11 months ago

Best way to analyze accurately is not XRF but Spark OES Spectrometer as mentioned above. XRF WDXRF needs special crystal and even then only analyzes to depth of several microns which may not be representative. When doing a weld you should know the % C for what is known as carbon equivalents: if that is required somewhere in the supply chain. XRF is not recommended. Spectro is a market leader for these products; contact at http://www.spectro.com

Victor Bergman
11 months ago
Victor Bergman 11 months ago

I fully agree that spark spectrometer is cheaper and more sensitive for carbon than WDXRF. However, I am quite surprised that your are only looking for carbon in your steel. Most of steel analysts want also measure traces of P, Ni, Cr, Si... and they select spark or XRF according to all analytes.

If you do not care about any other element except carbon, may be you think about surface cementation and then a Vickers hardness machine would be the most direct way to get this hardness (which is linked to the carbon amount). In such a case you are lucky because a hardness machine is cheaper than any of these spectrometers.

Helena Russell
11 months ago
Helena Russell 11 months ago

You are probably better off paying an analysis lab to to spark OES. If you're committed to doing it yourself, you should consider some old chemical techniques, such as http://nvlpubs.nist.gov/nistpubs/nbstechnologic/nbstechnologicpaperT33.pdf

My understanding of this method is that you combust the steel in pure oxygen and pass the effluent through a solution of Ba(OH)2, precipitating BaCO3. When done, you weigh the collected carbonate to figure out the carbon combusted. Another idea that occurs to me is tha during electro polishing or etching steel, a carbon deposit is often seen, since it is insoluble in most acids. Completely dissolving a sample and centrifuging the solution might allow you capture the carbon, which you could analyze by the method described above or through TGA. I haven't tried any of these, but ts safe to assume that there were good methods available before he invention of OES.