This Spring my colleagues and I attended the International Wrought Copper Council (IWCC) meeting in Osaka, Japan. The IWCC works for and with member companies across the world to support the copper and copper alloy fabricating industry. The organization recently reported that copper now meets the USGS benchmark Supply Risk score of 0.40 for automatic inclusion on the U.S. Critical Minerals List, so it’s important to make sure that the copper alloy one is buying, and selling, meets specifications.
I presented on “Real Time Analysis of Copper Alloys using Handheld X-Ray Fluorescence Spectrometry,” and discussed why metal analysis is important, the available methods for metal and alloys testing, and the capabilities of handheld X-ray fluorescence spectrometry technology when it comes to copper alloy grade identification.
Here’s a summary of the first half of the presentation addressing why analysis of copper materials is important and a brief explanation of the technologies used for analysis. The next article will report on the second half where my colleague addressed case studies of actual copper analyses utilizing XRF spectroscopy and copper standards.
Why and When to Analyze Metals
First, analyzing metals and ensuring the correct alloy is used is important — whether you’re working with copper or other metals — to avoid dangerous equipment failure and downtime related to incorrect material used. Offshore oil and gas or chemical facilities are good examples where positive material verification is critical to ensure safety as pipes or welds made of the wrong metal could be the cause of fires and explosions. Welds can fail, and metal fasteners can break if they are made of the wrong alloy.
Besides safety concerns, the wrong alloy elements can cause lost revenue for the industry. Metal fabricators and manufacturers may have to rework products because of incorrect material not meeting customer specifications. Scrap metal recyclers may have to downgrade incorrectly identified material. Customer dissatisfaction, brand reputation and lost revenue are at stake.
How can the wrong material get into your copper (or any metal) supply? One reason is the use of recycled metals. According to the USGS, “Old (post-consumer) scrap, converted to refined metal, alloys, and other forms, provided an estimated 160,000 tons of copper in 2022, and an estimated 670,000 tons of copper was recovered from new (manufacturing) scrap derived from fabricating operations. Of the total copper recovered from scrap, brass and wire-rod mills accounted for approximately 85%; smelters, refiners, and ingot makers, 10%; and chemical plants, foundries, and miscellaneous manufacturers, 5%. Copper recovered from scrap contributed 32% of the U.S. copper supply.”
Scrapyards receive many items that have a combination of metals and non-metal items that must be sorted and separated. Since manufacturers are increasingly using recycled materials in their fabrication processes, accurate sorting of scrap is essential to prevent from mixing alloys which can cause financial losses for both scrapyard and foundries. Even more concerning is if medical equipment that utilized radioactive sources were part of the scrap pile. Radioactively contaminated scrap threatens both the workers who handle it and the consumers of those finished products.
Because copper may be alloyed with metals that may be dangerous, or not meet customer specifications, the scrap needs to be analyzed, identified, and sorted when it arrives at the metal recycling facility and then quality checked before it is shipped to a customer. Then it should be analyzed by the customer before putting it into production.
Mix-ups can also happen during production. Insufficient material quality control can cause metal mixups which leads to failures and recalls.
These are just some of the reasons it is necessary for many industries using recycled metals to deploy a “trust but verify” method to ensure proper material verification before producing the product, and before it is shipped out the door.
Technologies used to test and identify metals and alloys
There are multiple possibilities for testing metals to identify the different elements that make up an alloy.
The basic methods are purely qualitative, and include visual inspection, magnet tests, spark tests or chemical acid tests. Those methods have important limitations, are not applicable to every type of metal base and are not very selective and specific. Because of these shortcomings, these methods are mostly obsolete.
Elemental analysis using spectroscopic methods are generally preferred over purely qualitative testing methods because they provide more accurate results.
Lab-based stationary spectrometers such as Optical Emissions Spectrometry (OES) and X-ray Fluorescence (XRF) spectrometry deliver excellent analytical performance, but are not always convenient to use. Material inspection in the field is not an option since they require the sample to be brought to the analyzer.
With mobile OES, the analyzer can be brought to the sample, but in many circumstances can be difficult to maneuver. While the measurement probe is lightweight, the main unit (including an argon gas bottle) must be carried with a trolley or a large carrying case so that mobility is still limited, which also affects efficiency.
Handheld analyzers that utilize XRF or Laser Induced Breakdown Spectroscopy (LIBS) are much lighter, and easy to maneuver and bring to the samples. They use a point-and-shoot approach and provide real time analysis, so a very high sample throughput can be achieved. Both XRF and LIBS technologies generate spectra that are processed using proprietary algorithms which calculate the chemical composition and the identified alloy grade, which can be displayed on the screen in real time.
Although handheld XRF and LIBS analyzers are more complementary than competitive: handheld LIBS is more suitable for steel and stainless steel (especially when measurement of carbon is needed), while handheld XRF that is more suitable for analysis of non-ferrous alloys such as copper alloys.
Handheld XRF analyzers usually contain libraries of tabulated values for common alloy grades found in the industries. Those tables include the composition limits for these alloy grades. The standard library includes about 500 alloys grades of all metal bases including 60 common copper alloys using the composition defined by the Copper Development Association. The alloy libraries can be augmented and customized by the user.
Best practices for manufacturers, including those utilizing copper, should include positively identifying alloys and analyzing their chemical composition at incoming, outgoing and material transfer points. To ensure they are shipping quality products, portable XRF analyzers can be utilized throughout the facilities to inspect all incoming metals against paperwork, for quality checks upon receipt of the raw material scrap, and for final analysis of the finished product before the material leaves the facility.
Download the full slide presentation
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