Analyzing Stainless Steel – A Guide to Choosing the Correct Equipment

Since Hitachi High-Tech is a leading provider of handheld laser-induced breakdown spectroscopy (LIBS) technology, it has recently received queries whether optical emission spectroscopy (OES) will be replaced by LIBS in the near future. Despite the fact that LIBS is a relatively new analytical technology with a great deal of potential, it cannot be readily used as an alternative to OES for accurate material identification needs. Hitachi High-Tech Product Manager Mikko Jarvikivi explains the reason for both the technologies to have their own place.

The advent of portable instruments with the ability to accurately analyze the chemical composition of materials has been an absolute advantage for companies over a wide array of industries. The correct type of portable analyzer ensures that positive material identification (PMI), material sorting, and quality assurance or control tasks can be performed in a rapid and efficient manner.

LIBS-based handheld analyzers such as the Hitachi High-Tech Vulcan offer a rapid and cost-effective solution. In terms of performing PMI testing or sorting alloys, LIBS instruments provide excellent performance with aluminum-based metals and stainless steels, and offer better performance while using low alloy steels and titanium. Apart from being robust, the Vulcan is less expensive, needs very less user training, and leaves an insignificant mark on the sample.

In the recent past, although LIBS technology has been used to achieve excellent advancements, OES analyzers still have considerably lower detection limits for 100% accuracy, which is highly significant for reliable separation of L-grade stainless steels. Although both technologies have a chance, the choice will depend on the job.

Analyzing Steels

In certain alloys, elements that have an impact on the workability, strength, melting point, and hardness of the metal exist at well below 100 ppm, and at present, laser-based analyzers cannot provide correct readings at such lower levels. In majority of the instances, including carbon steel, an OES-based analyzer such as Hitachi High-Tech’s PMI-MASTER is the reliable and superior choice.

Carbon

In the process of separating L-grade from high grades of stainless steel, carbon is not only vital but also the most significant element for steel and iron grades, allowing the separation of unalloyed and low steels. For many decades, stationary and mobile OES has been a recognized and standard method for such applications.

Despite the focus on measuring the amount of carbon in steels, it should be noted that carbon is not the only element of interest in steels. In cases where carbon equivalency has to be accurately calculated, measurements for manganese, nickel, titanium, chromium, and silicon content can all be obtained using an OES analyzer. However, LIBS devices do not have the ability to simply measure phosphorous and sulfur. In the presence of refractory elements with high melting points and high hardness, such as tungsten, niobium, molybdenum, hafnium, and tantalum, majority of the prevalent LIBS analyzers will find it difficult to accurately measure them.

Duplex Steels

In the rapidly developing field of duplex steels, simple identification and separation of duplex grades through nitrogen content is a significant application.

Other Important Trace Elements

At the same time, there has been increasing interest in low concentrations of boron — down to less than 5 ppm. When used as an alloying element, boron enhances the hardenability and hardness of steel alloys by heat treatment. It is specifically useful in tools, construction, and for objects such as screws.

However, boron is not so desirable in unalloyed steels due to its adverse impacts on welding properties. The limit for boron to be categorized as alloyed steel is only 0.0008 ppm. Various customs offices across the globe have to verify incoming imported steel for such lower limits.

Similar to an array of all technically relevant elements such as carbon, OES analyzers offer more reliable results and higher accuracy for boron, nitrogen, and all other relevant trace and main elements.

A Trusted Method

Although handheld LIBS devices are less expensive, smaller, and faster to use, the inherent technology is still under development. OES has been in use for several decades and is a reliable method for obtaining accurate readings even for very low levels of detection. The most important factor is: is it affordable to get small shifts in the amount of carbon and other elements wrong?

Even negligibly small shifts in the amount of carbon, and other elements, in a sample could have an impact on the brittleness and strength of the material, as well as the way it is worked with respect to tools, methods, and temperatures. Moreover, if an inaccurately graded alloy is used in a machine, tool, or part that eventually fails, it could lead to disastrous accidents, expensive product recalls, lawsuits, and reputation loss. OES guarantees repeatability and precision.

Hitachi High-Tech has been supporting various industries with analysis technology for more than four decades and has recognized that several distinctive technologies have to coexist to provide an optimal solution for the application and analysis requirements of the users. To achieve this, experts Hitachi High-Tech strive to learn the requirements of the users before suggesting the best product for the task at hand.

Hitachi High-Tech’s LIBS-based Vulcan handheld analyzer is outstanding for sorting aluminum and stainless steel, and for performing certain PMI quality control tasks. The X-MET8000 range of handheld XRF analyzers is the market leader for rapid and non-destructive analysis. The OES range of stationary and mobile analyzers ensure on par performance in accurately determining the chemical make-up of a complete range of alloys.

This information has been sourced, reviewed and adapted from materials provided by Hitachi High-Tech Analytical Science.

For more information on this source, please visit Hitachi High-Tech Analytical Science.

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