LIBS vs. X-Ray – The Whole Story

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LIBS vs. X-Ray - The Whole Story

Our Answer: Use X-ray whenever possible, LIBS only if X-ray can’t do the job.

Why is the world’s leading manufacturer of handheld LIBS recommending X-ray as a superior tool for scrap processing?

SciAps is the only company that makes high performance LIBS and X-ray. So we know each technology like no one else. And we’ve been working in the scrap markets for decades. We see X-ray as the workhorse for nearly all scrap processing, and LIBS as the niche product for lucrative, but specialty applications.

LIBS vs. X-ray for Aluminum

Historically X-ray has performed poorly on aluminum alloys, but we’ve addressed that. The new X-250, debuting at ISRI 2018, is a major advance for Al analysis. The SciAps X-250 features a far more powerful X-ray tube technology and a totally re-thought aluminum analysis algorithm. We can separate 90% of your aluminum alloys in 2 seconds by instant analysis of Mg, Si, Al, Ti, V, Cr, Mn, Fe, Ni, Cu and Zn. The X-250 measures Mg content (nominally) as low as 0.2% in 2 seconds, or those aluminums that differ only by Mg contents in the ranges of 0%, 0.3% and 0.5%. For example alloys like 6063 and 1100, 356 and 357, 3003/3004/3005. We’ve put the focus where it needs to be — fast Mg and Si analysis. And for those aluminums that require Zr, Sn, Ag, Pb and/or Bi the X-250 is smart enough to automatically test the material at a different tube setting for 2 additional seconds. The result: Sort 90% of your materials in 2 seconds, the rest in 4 seconds. The built-in smarts means an operator doesn’t have to be an aluminum alloy expert to sort material quickly and accurately.

SciAps X-250 screenshots - aluminum alloys

No other X-ray gun can sort these low Mg aluminum alloys this fast and this accurately.

For example, a common mix-up that we see everywhere is 6063 from 1100. Older X-ray guns take 20-60 seconds to measure the must-see 0.5% Mg in 6063, and most operators don’t want to wait that long. Instead, many X-ray operators key on the copper as an 1100 indicator. However, tramp Cu is now prevalent in 6063 up to 0.1%, so not measuring the Mg will cause a mix. Our new X-250 model eliminates 6063/1100 mixes by only requiring 3 seconds to see the key distinguishing element of 0.5% Mg in 6063.

Precise analysis of transition and heavy metals in Al alloys is important, and here X-ray wins hands down. Elements like Cr, Mn, Cu, Zn, Zr, Ni and other metals. This is why X-ray has always been the technique of choice for high temps and stainless. For example consider 3105 and 6061. The measurement of low concentrations of Cr, Cu and Mn is very important to this separation. Yes LIBS is seductively fast on aluminum alloys because it’s so good measuring Mg and Si. And LIBS can measure Li, Be and B, whereas X-ray cannot. However, modern aluminum alloy sorting requires excellent precision on the transition metals such as Cr, Mn, Fe, Cu and Zr. X-ray excels at these elements and is superior to LIBS even at low concentrations.

What about lithium (Li)? We hear this a lot and we have quite a few LIBS users measuring Li in aluminum alloys. And it’s true that LIBS measures Li, but X-ray does not. Nearly every aluminum alloy with lithium also contains silver (Ag). Silver is added with lithium to better homogenize the lithium in the metal matrix. X-ray measures Ag well, thus making Ag a useful indicator for lithium-containing aluminum alloys. If you see Ag in aluminum with your X-ray gun, then you can bet Li is there as well. So if you want X-ray for aluminum alloys, your first line of defense to sort out those alloys containing lithium is to look for Ag detected. Ag in an aluminum alloy means lithium is along for the ride.

So where do we recommend using LIBS for aluminum alloys? Three areas: (1) If you want to measure Li, beryllium (Be) and/or boron (B) directly LIBS is the only choice. Reason (2): X-ray can mix up aluminums if the material is dirty or anodized or the X-ray gun’s window is dirty. These cause false high Si results leading to mix-ups, or in the case of anodized material incorrect results. Our LIBS burns through anodizing and surface dirt, and there’s no window to contaminate. If you don’t want to grind or deal with sample prep, use LIBS. Finally, (3) if you just don’t want to deal with the regulatory headache of an X-ray device, our Class 1M rated Z-200 is the way to go.

LIBS vs. X-ray for Red Metals

LIBS is perceived as a good option for red metals for two reasons. First, LIBS quickly measures Al and Si content, plus the other metals in aluminum and silicon bronzes in a single fast test. Older generation X-ray guns required two X-ray tube settings (i.e. beams), were slower, and required operator knowledge when to use a single beam (Al, Si not needed) versus slower two beams. The second reason is beryllium (Be) in copper alloys. X-ray can’t measure Be, LIBS excels at it.

However the X-ray side of the story has changed. The SciAps X-250 with its updated tube technology can measure typical levels (1-10%) of Si and Al in bronzes in 1-2 seconds instead of the 20-30 sec of older generation X-ray guns. Total testing time is therefore 3-4 seconds if you need Si and Al, 1-2 seconds if you don’t. And the precision from X-ray on typical transition and heavy metals that alloy red metals – Cu, Zn, Ni, Mn, Pb, Se, Bi, Sn and Fe – is superior with X-ray. Moreover the latest X-250 software automatically determines if the material could be an aluminum or silicon bronze, and extends the test at the 2nd beam setting. Now your operators need not be red metal experts. The gun will perform the most time efficient test, whether or not the material contains Al and Si.

What about beryllium? Our LIBS will measure Be down to 10-20 ppm in a red metal. X-ray cannot measure Be (nor Li, B or C). So beryllium in copper is certainly a good role for LIBS. However if you don’t work with beryllium copper alloys, and you’d prefer the speed and ease of X-ray, there’s an option. As with silver in aluminum alloys, cobalt (Co) is an “indicator element” for Be in copper alloys. Beryllium is added to copper as a Be-Co complex. If you measure Co in a copper alloy, you’ve got Be as well. Cobalt is at the 0.1-0.2% level in Be-Cu alloys, easily measured by X-ray.

Practically then, if you’re comfortable using Co as an indicator for beryllium coppers, then the X-250 is the better choice for general red metal sorting and analysis. Alternatively, if you want to directly measure Be in copper alloys, or other examples like direct measurement of Li in aluminums, boron in nickels, stainless or ferrous, or carbon in anything (see below), then LIBS is your only choice.

LIBS vs. X-ray for Ferrous and Stainless

Ferrous and stainless is a rapidly growing niche area for LIBS, driven by our ability to measure carbon.

Larger processors dealing with stainless use our LIBS to upgrade their stainless into low carbon grade (L-grades, < 0.03% C) and straight grades. These users also sort carbon steels by carbon content, along with residual elements Mn, Cr, Si, Cu, Ni, Mo, V – a great application for argon-purged LIBS. SciAps makes the only handheld carbon analyzer on the planet (the Z-200 C+), and it’s become a handheld replacement for the spark OES systems traditionally used for carbon analysis. Finally, there’s an occasional need to segregate certain cast and ductile irons by Mg content. Some have 0.04% Mg, others have none. Our LIBS does this, but X-ray cannot measure these low levels of Mg in ferrous.

Be forewarned that measuring carbon with LIBS is a more difficult endeavor than point-and-shoot X-ray. You must grind the material, properly warm-up the analyzer, and check the calibration every few hours. None of this is hard, it just requires discipline. If you handle a lot of stainless and ferrous and you only care about sorting out 18-8 from 316 or higher grade stainless, or you are only focused on VLR (very low residuals) then stick with X-ray. However if you need to measure carbon either to sort carbon steels or get that nice upgrade to an L-grade, then LIBS is your only handheld solution.

The Upshot

If you can use X-ray for your scrap processing applications, then you should. It’s easier to use, more precise on stainless and high temps, better on turnings, and our latest creation the X-250 plus the Al App delivers exceptional performance on aluminum alloys.

For the specialty applications mentioned herein, however, X-ray isn’t an option and for these, LIBS is an excellent alternative handheld technology.

LIBS also has many applications with aluminum alloys. We have LIBS clients that must measure low Mg precisely, down to the 0.05% level. X-ray cannot do this. Some also want to directly measure B, Li and Be down to 10-20 ppm levels, again outside the capability of X-ray. So for some advanced aluminum alloy sorting applications, typically driven by low Mg, Si, Li, Be and/or B requirements, LIBS is the superior technique. If you’re sorting anodized aluminum scrap, our LIBS powerful laser burns right through anodized components, eliminating the sample prep needed by XRF.

We would be remiss in omitting a final reason to choose LIBS over X-ray: ionizing radiation. Depending on where you operate, regulatory restrictions on X-ray are either burdensome or rapidly becoming so. So, if you really don’t want to deal with X-ray regulations, then LIBS is a great alternative. The SciAps Z has recently been re-classified as a Class 1M rating, making it very safe and subject to minimal regulatory demands.

Our view on the interplay between LIBS and X-ray is therefore easily stated: Use LIBS if you need one of the specialty applications described here. In all other cases, X-ray is the best option.

SciAps Scrapper X-250

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