See How at ISRI 2016
Metals derive properties such as strength, ductility, and corrosion resistance from alloying elements. Adding alloying agents is a complicated process; the right ingredients must be added in the right percentages in order for the final product to perform as expected. But sometimes materials are present in metal that weren’t put there — these are known as tramp elements, or residual elements, generally defined as those that are not deliberately added and that cannot be totally removed by metallurgical processes. In this post we’ll look at how tramp elements can influence metal processing.
How do tramp elements affect steel?
Tramp elements are not inherently bad but the percentage of tramp elements in the overall composition of the metal must be known precisely to ensure the final product will have the desired properties. Tramp elements such as copper, tin, and phosphorus can be harmful in steel, causing surface defects and brittleness in steel finished products.
According to an article on keytometals.com, the presence of some tramp elements, in this case phosphorus, can have vastly different effects on steel depending on the amount. For example, the addition of only 0.17% phosphorus increases both the yield and tensile strength of low-carbon sheet steel and improves the bake hardening response and deep drawability. However, too much phosphorus can make steel brittle and reduces toughness and ductility.
How do tramp elements get into steel?
Steel is the world’s most recycled material. According to the ISRI fact sheet, The Iron and Steel (Ferrous) Scrap Industry, 73 million metric tons of ferrous scrap was processed by the scrap recycling industry last year, nearly 55% of the volume of all domestically-processed material. With such a high volume of recycled metal coming in to scrap yards, operators must be careful to accurately identify and sort these materials. Determining the presence of contaminants or tramp elements not only influences the amount of money a scrap yard will pay for incoming metals, but how much their customers will pay, or whether they will even continue to do business with a scrap yard found to be dealing in poor quality raw materials that will impact the value of their finished goods.
Use X-ray fluorescence to detect contaminants in recycled steel
Scrap yards use portable X-ray fluorescent analyzers to identify the various elements contained in the metals and then grade and sort them appropriately. Although XRF analyzers cannot grade mild steels, they can be useful in tramp element analysis to help prevent these materials from being introduced into a melt. Scrap yard operators can use portable XRF analyzers throughout their facilities to inspect all incoming metals against paperwork, for quality checks after the metals are sorted, and for final analysis before the metals leave the facility.
See XRF at ISRI
To see for yourself how portable XRF analyzers can help detect tramp elements in the recycled materials you ship to customers, visit us at Booth # 2247 at the ISRI Convention & Exposition. If you can’t be at the show, visit this web page to learn about the reliable scrap sorting methods available to the metal recycling industry, including light and tramp elements.
ISRI Convention & Exposition 2016
April 2-7, 2016
Las Vegas, Nevada USA