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What is Silicon Steel? (Why it’s the Alien Steel)

Large rolls of silicon steel at a warehouse.

Discover everything you need to know about silicon steel, its components, how it's made, where it's used, its two kinds and a few frequently asked questions.

I don’t know about you, but I didn’t know there were silicone and silicon. Silicone is what we inject into our faces and butts, but silicon is a different thing entirely. Silicon is a semi-conductive blue-/grey solid material and the eighth-most common element in the universe, but it rarely occurs in its purest form on earth.

90% of the earth’s crust is composed of silicate minerals, making it the second most abundant element next to oxygen. Crazy stuff! Pure silicon is found in space, amongst the planetoids and cosmic dust storms. Personally, I’d rather be injected with cosmic dust, but that’s just me.

Silicon steel (or commonly known as electrical steel) is an iron alloy mixed with silicon to create a soft magnetic material. We’re going to explore how it’s made and why we use it!

Related: Carbon Steel | Tungsten vs. Manganese | Types of Steel

What It Is

Rolls of CRGO steels in storage at a warehouse.

Silicon steel is a mixture of iron with a silicon content of up to 3.2%. The silicon addition improves the magnetization of the steel and its electrical resistivity (the opposite would be electrical conductivity). Adding silicon increases irons’ electrical resistivity up to 5 times. This change results in a decrease in the alloy’s eddy current losses, which directly affects the magnetic core.

An eddy current is a loop of electrical currents equipped with conductors designed for altering a magnetic field, and the magnetic core is basically a highly magnetic guiding material (the conductor). If the eddy current remains constant, there will be no magnetic core loss, making for smooth function.

Something that shows a material’s magnetic flux density is portrayed in a hysteresis loop. Silicon steel shows a very tight hysteresis loop, indicating a more constant magnetic flux.

This is a graph illustration of the characteristics of a magnetic field.

When the percentage of added silicon exceeds 2%, there is a subsequent decrease in the Curie temperature. This is a rather complicated term so bear with me. The Curie temperature is the maximum temperature above which the given material loses behaviors of ferroelectricity and piezoelectricity.

Ferroelectricity: spontaneous electric polarization

Piezoelectricity: accumulative electric charge in solid materials caused by mechanical stress (usually pressure and heat)

A man inspects the large steel equipment in the factory.

So more simply put, there’s a sweet spot of silicon that enables the perfect harmony of electric charge a magnetic-ability. Certain iron-silicon alloys also incorporate up to 0.5% manganese for durability and aluminum for workability. Less than 0.005% carbon is added to this alloy, as carbon causes unnecessary magnetic aging. There has to be a very particular blend of all of these elements to create a perfectly functioning electrical steel device.

When alloying these elements it’s very important that there is no risk of contamination. Something as small as one micrometer of accidentally incorporated carbides or oxides are detrimental to the materials’ magnetic permeability. The uses for electrical steel are rather specific, and their standard of workability is incredibly high.

Where It’s Utilized

The place you’ll most likely see silicon steel in use it at the top of a power line, in those cylindrical cases called transformers. These big boys simply transfer electrical energy from one circuit to another. They’re also used when manufacturing stators and rotors of electric motors.

A look at a high voltage power station with transformers.

Two Kinds of Silicon Steels

CRNGO: cold-rolled-non-grain-oriented steel.  This silicon steel is made without any special pressing to control crystal orientation (this is the overall texture of the material). With this mish-mash of un-oriented grain, it results in an isotropic material (where magnetic properties are omnidirectional). This is the less expensive option and is used when cost takes priority over efficiency, where the magnetic flux does not have to be constant. CRNGO is found in generators with moving parts and electric motors.

CRGO: cold-rolled-grain-oriented steel. This silicon steel is processed so that the magnetic flux is constant and directional. It possesses a tight crystal orientation achieved during the rolling process. CRGO is supplied in coil form and is then rolled out into  “cold-rolled” strips of less than 2mm. In both cases of non-grain oriented and grain-oriented laminated sheets, the coil is rolled out and then cut to shape. This is the reason for its need for workability.

CRGO or silicon steel coils in storage at a warehouse.

FAQ

Is silicon steel magnetic?

Absolutely, that is the entire point of this alloy.

Where can I get silicon steel?

Since it’s a product intended for such a specific use, it won’t be available at the common home and hardware store. There are private companies that sell silicon steel.

How do you cut silicon steel?

This kind of thing should only be done by experts, and they speak about it here.

Why use silicon steel?

It’s wonderfully energy efficient due to its electrical and magnetic properties. It’s a great conductor, requiring less energy for maintaining constant flows.

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