Measuring carbon in steel – absolute reliability matters


The incorrect analysis of the carbon content in steel can lead to a multitude of issues down the line, making accurate and reliable carbon analysis critical. Our OES expert Willy Sanders looks at why…

Carbon steel has been in use for nearly 2,000 years, but rose to prominence during the late industrial revolution when steel makers really began to exploit the properties that a little carbon can bring to iron products. Carbon steel is harder and stronger than raw iron, making it ideal in construction and in a whole range of manufacturing contexts. From buildings through to cooking pots and transportation, carbon steel makes our lives better.

However, for its correct application the exact carbon content in steel or stainless steel must be known. For all the strength carbon lends to a given grade of steel, its presence affects the brittleness, melting point and workability of the substance. Most carbon steel has a carbon content of between 0.15 and 2%. In alloys such as the L-grade group of austenitic stainless steels, the carbon content must be lower than 0.03%, and tiny amounts like this present a challenge in reliably assuring the correct proportions.

Would you risk it?

Faulty analysis of carbon and L-grade stainless steels can lead to all sorts of difficulties. The carbon content of the substance not only determines its strength and its brittleness in application, but it affects how the metal can be worked. If a piece of steel has been incorrectly graded and is subsequently worked into a part, its breakage due to being too thin or too brittle will lead to mechanical failure. This may result in costly product recalls, lawsuits and loss of reputation. Reliable quality control is therefore vital.

An incorrectly graded piece of carbon or L-grade stainless steel may also end up being worked at the wrong temperature or using a process it is not suited to. This may ultimately destroy the material, adding to waste and further costs in replacement.

Some of the most common problems resulting from incorrect analysis or falsely stamped carbon and stainless steels are discovered after they’ve been welded. The use of welding techniques and temperatures unsuited to the specific metal leads to discolouration, corrosion and even breakage. For example, decades of service life can be lost on an alloy heat exchanger if it is fitted to a flange made from incorrectly specified metal.

From foundries to factories and laboratories, getting the carbon content right is a critical concern across industries.

Positive identification

Manufacturers, and anyone along the carbon steel supply chain, need an ultra-reliable way of analysing steel samples for their carbon content before it’s put into use. Spark optical emission spectroscopy (OES) is the technology trusted by thousands of steel producers for its rapid, accurate and reliable carbon analysis results. OES facilitates the fast and trustworthy identification of all relevant elements in steel – carbon, silicon, manganese, phosphorous, sulphur, chromium, nickel, boron, nitrogen and more - without the expense or inconvenience of sending samples for wet analysis in a lab. OES is also a recommended method for assuring API 5L, as well as other global industry standards.  

Reliable solution

Both lab-based and mobile OES solutions are available, delivering fast and accurate verification of carbon and stainless steel grades. For companies looking for reliability and versatility, the PMI-MASTER Smart from Hitachi High-Tech is a popular option because it is portable, fast and highly accurate. With a UV Touch Probe, multi-CCD optics and the capability of displaying and storing data on the go, it can be used to test all kinds of metallic samples from huge pressure equipment, tubes and construction parts down to wires with a 1mm diameter. Results on even the lowest carbon values are available in under 20 seconds, with a level of detection (LOD) right down to 30ppm.

At Hitachi High-Tech we know how important accurate carbon results are, and that your business depends on them. To find out more about PMI-MASTER Smart - or the range of other analysis solutions we offer - get in touch with your query or book a demo. Our experts are ready to help.

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