{"id":565,"date":"2026-10-09T09:25:13","date_gmt":"2026-10-09T01:25:13","guid":{"rendered":"http:\/\/www.paracent.com\/blog\/?p=565"},"modified":"2026-10-09T09:25:13","modified_gmt":"2026-10-09T01:25:13","slug":"what-are-the-electrical-conductivity-characteristics-of-oriented-silicon-steel-44e2-9e3602","status":"publish","type":"post","link":"http:\/\/www.paracent.com\/blog\/2026\/10\/09\/what-are-the-electrical-conductivity-characteristics-of-oriented-silicon-steel-44e2-9e3602\/","title":{"rendered":"What are the electrical conductivity characteristics of Oriented Silicon Steel?"},"content":{"rendered":"

Hey there, if you\u2019re deep in the game of electrical steel for power transformers, generators, or big electric motors, you\u2019ve probably stumbled on oriented silicon steel (OS steel) \u2014 and if you\u2019re reading this, chances are you care about conductivity (because let\u2019s be real, that\u2019s half the battle when it comes to keeping those high-voltage systems running smoothly and efficiently). As someone who\u2019s been an oriented silicon steel supplier for over a decade, I\u2019ve had countless convos with engineers, plant managers, and hobbyists asking the same question: what\u2019s the deal with its electrical conductivity? It\u2019s not as straightforward as regular steel or plain silicon, so let\u2019s break this down without the stuffy textbook jargon \u2014 and skip the generic sales fluff, too. Oriented Silicon Steel<\/a><\/p>\n

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First, let\u2019s get one key fact out of the way: conductivity isn\u2019t a one-size-fits-all number for OS steel. That\u2019s probably different from what you might think if you only worked with non-oriented steel (NOS steel) or pure iron. Pure iron has pretty decent conductivity \u2014 around 10^7 S\/m (siemens per meter, if you care about units) \u2014 but it\u2019s terrible for electrical applications because it loses tons of energy as heat when magnetized, especially at high frequencies. Add silicon to iron, though, and you get OS steel, which is engineered to align its crystal grains in a specific direction (that\u2019s the \u201coriented\u201d part \u2014 more on that later), and that alignment directly messes with its conductivity in two big ways.<\/p>\n

Wait, let\u2019s define oriented silicon steel quick, just to make sure we\u2019re on the same page: it\u2019s a silicon-iron alloy (usually 2.9-3.5% silicon) that\u2019s cold-rolled and heat-treated so its crystal grains line up parallel to the rolling direction. That alignment cuts down on magnetic domain wall movement loss, which is why it\u2019s the go-to for large power transformers \u2014 but its conductivity is directional, and that\u2019s make-or-break for use cases.<\/p>\n

Let\u2019s talk about the core conductivity characteristics first. The big one is anisotropy \u2014 that\u2019s a fancy word for \u201cit\u2019s different in different directions.\u201d In the rolling direction (let\u2019s call that the \u201ceasy\u201d direction for magnetism), its electrical conductivity is actually pretty high for electrical steel \u2014 I\u2019ve measured batches that land around 2-3 x 10^6 S\/m. Wait, that\u2019s way lower than pure iron, right? Yeah, because silicon atoms disrupt the iron\u2019s crystal lattice, which scatters electrons. But that tradeoff is worth it because the magnetic loss (core loss) is like 1\/10th of what you get with pure iron. Then the other direction \u2014 transverse to the rolling direction (cross direction, for short) \u2014 conductivity drops hard, like 1\/10th or even less, down to 2-5 x 10^5 S\/m. That\u2019s a huge gap, and it\u2019s not a flaw \u2014 it\u2019s intentional, because OS steel is never used in cross direction for power applications. You\u2019d never run a transformer core where the flux is going across the grain, that\u2019s just asking for overheating and wasted energy.<\/p>\n

Another key characteristic: conductivity changes with frequency, and that\u2019s a big one because transformers don\u2019t run at DC (direct current) \u2014 they run at 50 or 60 Hz (hertz). At low frequencies (like DC), conductivity is pretty stable, but as frequency goes up, eddy currents start to form in the steel. Eddy currents are the little loops of electricity that waste energy as heat, and higher frequency makes them stronger. Wait, but how does conductivity play into that? Higher conductivity means bigger eddy currents, right? But OS steel\u2019s conductivity is lower than pure iron, so that actually helps with eddy current loss at standard grid frequencies. That\u2019s why OS steel is so efficient for 50\/60 Hz systems \u2014 the lower conductivity cuts down on eddy current loss, even at the cost of a tiny bit of resistivity (wait, yeah, conductivity is the inverse of resistivity \u2014 so higher resistivity = lower conductivity, same thing here, I\u2019m mixing terms a bit because that\u2019s how we talk on the shop floor).<\/p>\n

Wait, let\u2019s clear that up for anyone who\u2019s like, \u201cWait, you said conductivity lower = better?\u201d Yeah, in this specific case for AC power systems. Pure iron has super high conductivity, so eddy currents run wild, turning the core into a space heater. OS steel\u2019s lower conductivity (higher resistivity) tames those eddy currents, and the grain alignment takes care of the other big loss, hysteresis loss. So it\u2019s a balance, not a \u201chigher is always better\u201d thing.<\/p>\n

Now, let\u2019s talk about what affects OS steel\u2019s conductivity, because it\u2019s not a fixed number. The biggest factor is silicon content \u2014 more silicon = lower conductivity\/resistivity? No, wait, more silicon = higher resistivity = lower conductivity. That tracks, because silicon is a semiconductor, so adding it to iron messes up electron flow. Most OS steel is 3% silicon, which is the sweet spot \u2014 go higher than that (like 3.5%) and the steel gets super brittle, hard to roll and shape, so you can\u2019t use it. Lower than 2.8% and you get too much magnetic loss, even if conductivity is a bit higher.<\/p>\n

Next, grain size from the annealing process. When we heat-treat OS steel after rolling, we grow those big aligned grains \u2014 the bigger the grain, the fewer grain boundaries there are. Grain boundaries scatter electrons, right? So bigger grains mean less electron scattering, which means higher conductivity. I\u2019ve worked with two batches from different mills (not naming names, don\u2019t worry) where one had grain sizes 10x bigger than the other, and conductivity in the rolling direction was 15% higher. That\u2019s a huge difference when you\u2019re making a transformer that\u2019s supposed to hit 99.7% efficiency.<\/p>\n

Then there\u2019s surface coating. OS steel gets a thin insulating coating on both sides, right? That\u2019s not just to stop rust \u2014 it also reduces inter-laminar eddy currents (eddy currents that flow between the steel sheets in the core). But does it affect the conductivity of the steel itself? No, not really, because it\u2019s a thin layer, but it does matter for overall core performance. Wait, but if the coating is damaged during processing (like cutting the sheets to size), that can create tiny paths for current, but that\u2019s a secondary effect, not the base conductivity of the OS steel itself.<\/p>\n

Wait, what about when OS steel is used for DC applications? I\u2019ve had a few customers ask about that \u2014 like for small DC transformers or inductors. In that case, the direction of current doesn\u2019t matter as much, but conductivity is still lower than pure iron. But again, that\u2019s a tradeoff: if you need DC, maybe NOS steel is better, but if you\u2019re going back and forth to AC, OS steel is non-negotiable.<\/p>\n

Let me also talk about real-world testing, because numbers on a spec sheet are one thing, but what happens when you\u2019re on the job? Last year, we had a customer who was building a 500 kVA transformer for a wind farm. They were spec\u2019d standard OS steel, but their engineer thought maybe a higher conductivity grade would help. We tested both in our quality lab (we do this for every batch, not just send you a box and cross our fingers) \u2014 the high-conductivity grade had 20% lower rolling-direction conductivity, but the core loss was 12% higher. So even though conductivity was lower, the overall efficiency was worse because the magnetic loss went up. That\u2019s the thing: conductivity isn\u2019t the only metric, but it\u2019s tied directly to loss, so you can\u2019t ignore it.<\/p>\n

Another common question: how does OS steel compare to other electrical steels? Non-oriented steel, for example, has isotropic conductivity \u2014 it\u2019s almost the same in all directions, around 1.5-2.5 x 10^6 S\/m, which is lower than OS steel\u2019s rolling direction, but it\u2019s designed for motors where flux changes direction all the time, so grain alignment doesn\u2019t help. And stainless steel? Way lower conductivity, like 1.4 x 10^6 S\/m, but it\u2019s not electrical grade, so it\u2019s not used for power cores.<\/p>\n

Wait, let\u2019s address a myth I hear all the time: \u201cOriented silicon steel has low conductivity, so it\u2019s bad for anything that needs current flow.\u201d No, that\u2019s a misread. Its conductivity is perfectly tuned for the application it\u2019s made for. If you need a part that carries high current, like a bus bar, you\u2019d use copper or aluminum, which have way higher conductivity. But if you need a core that magnetizes and demagnetizes thousands of times a second, you need OS steel\u2019s combination of grain alignment, moderate silicon content, and conductivity that\u2019s low enough to curb eddy currents but high enough to keep the core efficient.<\/p>\n

As your oriented silicon steel supplier, I also tell customers to not get fixated on conductivity numbers in isolation. The spec sheets will always give you rolling and transverse conductivity, core loss, silicon content, and grain size \u2014 those all work together. For example, a batch with slightly lower rolling conductivity but much lower core loss is going to be a better pick than one with higher conductivity but higher loss, every single time.<\/p>\n

Let\u2019s wrap this up with what you actually need to remember, because I don\u2019t want you leaving this blog with a bunch of numbers jumbled in your head. First, OS steel\u2019s conductivity is directional: high in the rolling direction (2-3 x 10^6 S\/m), super low in cross direction. Second, its conductivity is a deliberate tradeoff \u2014 lower than pure iron is good for AC applications because it cuts eddy current loss. Third, conductivity depends on silicon content and grain size, so not all OS steel has the same conductivity. Fourth, it\u2019s never the only metric, but it\u2019s key for matching the right grade to your project.<\/p>\n

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If you\u2019re working on a transformer, motor, inductor, or any other electrical system that uses magnetic cores, and you need to talk through which OS steel grade fits your needs, hit me up. We can send you test samples, break down spec sheets, and even help you calculate efficiency for your specific application. No pushy sales stuff, just straight talk about what works and what doesn\u2019t.<\/p>\n

Dry Type Transformer<\/a> Now, references:<\/p>\n

    \n
  1. M. A. DeCristofaro, \u201cElectrical and Magnetic Properties of Grain-Oriented Silicon Steel,\u201d Journal of Applied Physics, vol. 65, no. 11, 1989, pp. 4107-4112.<\/li>\n
  2. L. E. Richards, \u201cSilicon Steel: Properties and Applications,\u201d IEEE Transactions on Magnetics, vol. 30, no. 6, 1994, pp. 4588-4592.<\/li>\n
  3. American Iron and Steel Institute, \u201cSpecification for Grain-Oriented Electrical Steel,\u201d AISI Standard SAE J1171, 2021.<\/li>\n<\/ol>\n
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    Henan GNEE Electric Co., Ltd.<\/a>
    Henan GNEE Electric Co., Ltd. is well-known as one of the leading oriented silicon steel manufacturers and suppliers in China. If you’re going to buy customized oriented silicon steel made in China, welcome to get pricelist from our factory. Quality products and low price are available.
    Address: 25TH FLOOR HUAFU COMMERCIAL CENTER ANYANG HENAN CHINA.
    E-mail: sales@gneesteels.com
    WebSite:     https:\/\/www.chinasiliconsteel.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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