If you’ve ever wondered what keeps aluminium strong, satellites powered and foundries running, the answer is a little grey metal called silicon metal.
Silicon metal, also known as Si, cool nickname, right? Might just go by that from now onwards. Si is a refined metallurgical-grade product containing approximately 98–99% silicon. Here’s the catch: silicon metal is never 100% pure. Even after smelting, it still contains small amounts of Fe (iron), Al (aluminium) and Ca (calcium), and these three impurities play a major role in determining how the silicon behaves in an alloy or chemical process. It’s also important not to confuse silicon metal with silicone (the polymer) or silica (quartz). I know, I know, they sound the same, but I don’t make the rules.
Si plays a major role in aluminium alloys, which account for 40–55% of global silicon metal demand. It improves aluminium’s strength and castability and is used in automotive parts, wheels and aerospace components. Silicon plays a crucial role in semiconductor manufacturing, the basis of chips, diodes and transistors used in modern technology. Si also features strongly in foundry applications, particularly in alloying and inoculation for cast iron. If I catch you confusing Si with silicone or silica after THIS explanation, oh we’re going to have a problem!
Here’s a fun fact to impress someone with later: the microchips inside phones, laptops, satellites and even AI hardware all originate from ultra-refined silicon metal. In other words, modern technology — from iPhones to rockets — begins its journey in the same type of silicon metal that moves through Mineral-Loy.
Fun fact aside, South Africa is also one of the notable producers of silicon metal globally. Silicon metal comes in different grade categories, created by the impurities mentioned earlier. Among these grades, the most consumed is grade 553, the industry workhorse. If you’re wondering why 553 looks different, here’s the quick cheat sheet: silicon metal grades normally follow a four-digit shorthand where the first two digits specify Fe and the last two specify Al. But 553 is one of the grades where Ca is explicitly included. In this case, Fe ? 0.5%, Al ? 0.5%, and Ca is typically ? 0.3%, depending on the supplier.
Grade 553 is the most commonly traded metallurgical-grade silicon worldwide, and also the grade Mineral-Loy handles most frequently. It is ideal for aluminium alloys because it is reliable, widely available and cost-effective (we love to hear that, don’t we?). Another advantage is that 553 is forgiving in furnace behaviour: it responds predictably during alloying, reducing the risk of melt instability. Still surprised why Si anchors the global silicon metal market?
If grade 553 is so great, why does Mineral-Loy handle multiple grades? The answer is simple: each customer’s process has different tolerance behaviours for Fe, Al and Ca. These impurities influence casting behaviour, alloy strength and grain refinement, chemical reaction stability and furnace dross formation. By supplying a range of grades, Mineral-Loy ensures compatibility across diverse sectors, from foundries to chemical producers.
So yes, grade 553 carries the industry on its back, but the diversity of silicon grades is what keeps our customers’ furnaces stable and their ability to produce quality products. At Mineral-Loy, we don’t just move metal — we move the right metal. Consider yourself Si-educated.