Selecting the Right Technology for Stainless Steel Analysis

Hitachi High-Tech Analytical Science is a leading supplier of handheld laser-induced breakdown spectroscopy (LIBS) technology. Recently, the company was asked whether optical emission spectroscopy (OES) will be replaced by LIBS in the near future.

While LIBS is a relatively new analytical technology that shows immense potential, it is still not ready to replace OES for accurate material identification requirements. Hitachi High-Tech’s Product Manager Mikko Jarvikivi explains why there is a place for both types of technologies.

One major benefit for companies across various industries was the advent of portable instruments — instruments that can accurately inspect the materials’ chemical composition. The right portable analyzer will allow users to perform positive material identification (PMI), material sorting, and control or quality assurance tasks in a fast and efficient way.

Hitachi High-Tech’s Vulcan is an LIBS-based handheld analyzer that provides a fast and low-cost solution. When users need to perform PMI testing or sort alloys, LIBS instruments deliver excellent performance with aluminum and stainless steel-based metals, and also provide good performance with low alloy steels and titanium. The Vulcan is robust, leaves a smaller mark on the sample, requires only minimal user training, and has a low cost of ownership.

In recent years, considerable developments have been made by using LIBS technology; but despite this fact, OES analyzers continue to have much lower limits of detection for 100% accuracy, which is indeed required to separate L-grade stainless steels in a reliable manner.

Both types of technologies have a place, and their selection will depend on the task at hand.

Analyzing Steels

In certain alloys, elements that influence the metal’s hardness, strength, melting point, and workability are present well below the 100 ppm level. At these low levels, laser-based analyzers cannot provide accurate readings. In most cases, including carbon steel, an OES-based analyzer, for example, PMI-MASTER from Hitachi High-Tech, proves to be a better and reliable option.

Carbon

Carbon plays an important role when L-grades have to be separated from high grades in stainless steel. This element is also important for steel and iron grades, allowing the separation of unalloyed and low steels. For many years, stationary and mobile OES has been a popular and well-established technique for these applications.

Although focus was given for estimating carbon content in steels, it must be remembered that carbon is not the sole element of interest in steels. Measurements for chromium, nickel, titanium, silicon, and manganese content can all be realized with an OES analyzer, in contexts where one has to accurately determine carbon equivalency. On the other hand, LIBS devices are not capable of measuring phosphorous and sulfur. Where refractory elements with high melting points and hardness, including hafnium, tungsten, tantalum, niobium, and molybdenum are present, many of the existing LIBS analyzers will find it difficult to measure them accurately.

Duplex Steels

In the rapidly growing area of duplex steels, identifying and separating duplex grades quickly and easily through nitrogen content is a significant application.

Other Important Trace Elements

Meanwhile, there is an increasing interest in low boron concentrations — down to less than 5 ppm. As an alloying element, boron enhances the hardenability and hardness of steel alloys through heat treatment. It is especially useful in tools, construction, and for objects such as screws.

However, boron is not favored in unalloyed steels as it is known to have a negative effect on welding properties. A limit of just 0.0008 ppm is enough to classify boron as alloyed steel. Many customs offices across the globe need to check the incoming imported steel for this very low limit.

As with an array of all technical related elements including carbon, OES analyzers offer more reliable results and better accuracy for boron, nitrogen, and other relevant trace and main elements.

A Trusted Method

Handheld LIBS devices are smaller, faster, and less expensive, but the development of the inbuilt technology is still ongoing. OES has been around for many years and is a reliable means for obtaining accurate readings even in the case of very low levels of detection. The bottom line is: can one afford to get small shifts in the amount of elements, including carbon, wrong?

The fact is that even extremely small shifts in the amount of elements, including carbon, in a sample will impact the strength and brittleness of the material and how it is worked with respect to tools, methods, and temperatures. If a wrongly graded alloy ends up in a machine, part, or tool that eventually fails, it could lead to expensive product recalls, catastrophic accidents, loss of reputation, and lawsuits. However, precision and repeatability can be ensured with OES.

Hitachi High-Tech has been supporting a wide range of industries with analysis technology for more than four decades. The company is well aware that a series of different technologies must coexist to give users the best solution for their analysis and application requirements. That is the reason why Hitachi’s experts get to know the customers’ needs before suggesting the most appropriate product for the job.

The LIBS-based Vulcan handheld analyzer is a perfect tool for aluminum and stainless steel sorting, and for certain PMI quality control tasks. The X-MET8000 series of handheld XRF analyzers leads the market for rapid and non-destructive analysis. In order to accurately find out the chemical composition of a complete range of alloys, the OES range of mobile and stationary analyzers delivers excellent performance.

For more details, customers can contact Hitachi High-Tech Analytical Science to book a demonstration.

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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