Archive for September, 2015

Aluminum Testing Needs and Options

Maximize Your Aluminum Sorting Throughput
While Protecting your Aluminum Furnaces

by using Oxford Instruments handheld LIBS analyzer

to monitor Lithium concentrations of recycled aluminum

ALUMINUM OVERVIEW

Aluminum is a very versatile metal with low density, relatively high strength, and an ability to resist corrosion.  Common applications for Aluminum include automobile and aircraft components, packaging, and power lines to name a few.

Recycling Aluminum saves 90-95% of the energy required to make Aluminum from Bauxite ore so over 50% of the Aluminum produced today is from recycled material, making it one of the most recycled materials after paper and steel (Source: Bureau of International Recycling).  It is critical that foundries know quickly and accurately what is being put into their melts.  This must be done before the material is melted down to ensure accurate melt chemistry and to avoid elements that can poison a batch or ruin production equipment.  For example, low levels of lithium in a melt can destroy the refractory walls in a furnace which can cost between $500,000 and $1,000,000.  High levels of Li in Al can also result in an explosive reaction.  These potential risks require that all aluminum-lithium based melts be manufactured in special furnaces which are designed for this purpose in order to avoid these situations and save substantial amounts of money and possibly lives.

In general, there are eight different families of aluminum alloys with different alloying elements.  The International Alloy Designation System is the most widely accepted naming scheme for alloys. Each alloy is given a four-digit number, where the first digit indicates the major alloying elements.

Aluminums are typically categorized as either Wrought Aluminum or Cast Aluminum. Wrought aluminums are the stronger of the two and are pressed, forged, or hammered while cast aluminums are poured into a mold in its molten form to give it a certain shape.

Cast aluminums are alloyed with the same elements as wrought aluminums, but have lower strength.  Cast aluminums are used when the large quantities required, quickly offset the costs to develop the mold with common uses being automobile parts, furniture, and cookware.

METAL IDENTIFICATION FOR THE ALUMINUM INDUSTRY

Oxford Instruments is currently the only analytical equipment manufacturer to offer three different technologies for Aluminum identification, XRF, LIBS, and OES.  Each technique offers different benefits that make it better suited depending on the end users testing goals.

HANDHELD X-RAY FLUORESCENCE _ HH-XRF

A common technique for alloy identification, including sorting recycled materials, is x-ray fluorescence (XRF).  This technique is usually in a hand-held (HH) design which is perfect for metal sorting in the field, warehouse, or even a laboratory.  Oxford Instruments has been manufacturing Handheld XRF analyzers for years and recently released the innovative X-Met8000 series.  In spite of the superior performance of the X-MET 8000, it is still not able to identify lithium in an alloy.  In fact, no XRF analyzer can measure lithium, even large laboratory type units.  For Handheld XRF, elements from Magnesium to Uranium are typically quantifiable, which makes it a very good technique for alloy sorting, including aluminums, but it is not able to determine if lithium is in the sample.

LASER INDUCED BREAKDOWN SPECTROSCOPY _ LIBS

Laser Induced Breakdown Spectroscopy uses a laser to ablate a very small area on the surface of a sample.  The ablated area forms a plasma which excites the sample.  The elements excited in the sample emit light which give off a characteristic wavelength that is measured by a detector. That information is processed and the elemental composition and concentration of the sample is calculated.

The Oxford Instruments LIBS Analyzer, the mPulse, is empirically calibrated with known alloys in certain bases to develop a calibration curve.  Aluminum-Lithium alloys are calibrated with standards that have concentrations from 0.5% to 2.5%.  Lower levels are possible with suitable calibration standards. This capability makes the Oxford mPulse Analyzer the preferred choice for the fastest aluminum alloys sorting available today (offering one second measurement times), but also for protecting the assets of your foundry.

The following table shows the results from two certified reference samples analyzed using an Oxford Instruments mPulse LIBS Analyzer.  The results show excellent accuracy and precision.

SAMPLE #1

 

 

 

 

SAMPLE #2

Al

Cu

Mg

Li

Al

Cu

Mg

Li

1

95.6

0.23

2.03

1.2

1

95

1.11

0.82

2.5

2

95.8

0.37

1.86

1.1

2

95.5

0.96

0.7

2.4

3

95.1

0.21

2.13

1.2

3

95.2

1.03

0.72

2.4

4

95.5

0.29

1.97

1.1

4

95.1

1.12

0.86

2.4

5

95.8

0.33

1.83

1.2

5

94.8

1.09

0.9

2.6

6

95.9

0.29

1.78

1.2

6

95.2

1.03

0.83

2.5

7

95.9

0.32

1.82

1.1

7

94.9

1.14

0.9

2.6

8

95.9

0.36

1.85

1.1

8

95.3

0.93

0.76

2.6

9

95.7

0.43

1.85

1.1

9

95.6

0.8

0.66

2.5

10

95.6

0.3

2

1.1

10

95.1

1.1

0.79

2.5

Average

95.68

0.313

1.912

1.14

Average

95.17

1.03

0.79

2.50

REFERENCE

95.698

0.42

2.18

1.03

REFERENCE

95.49

0.82

0.68

2.52

OPTICAL EMISSION SPECTROSCOPY _ OES

In the Optical Emission Spectroscopy technique, atoms in a sample are excited by energy that comes from a spark formed between sample and electrode.  The energy of the spark causes the electrons in the sample to emit light which is converted into a spectral pattern. By measuring the intensity of the peaks in this spectrum, Oxford Instruments’ OES analyzers can produce qualitative and quantitative metal analysis of the material composition with uncompromising accuracy.  LIBS is also considered a version of OES technology.

OES is capable of analyzing for Carbon.  Neither XRF nor any commercially available hand-held LIBS can measure carbon. OES can also quantify very low levels of Lithium in Aluminum (down to 0.0005%!) in addition to phosphorus and sulfur.  While XRF can analyze for phosphorus and sulfur, that technology cannot achieve the low limits of detection and precision that can be achieved with OES.

CONCLUSION

Oxford Instruments provides industry-leading solutions for the analysis of aluminum and other metals using a range of technologies.  For the fastest aluminum processing and most cost effective sorting technology on the market today, the Oxford mPulse is the right analyzer for the job.   In addition to speed and cost benefits, the mPulse can also provide you with the required elemental data to prevent lithium from damaging aluminum furnaces which could result in $1MM+ in avoidable costs.

Prepared by associates of Oxford Instruments.