All right

which brings us back to where we stopped last time

which was going through

the individual element.

I'll just go quickly back into starting over again with the contaminants.

The one we started with was silicon.

So silicon is obviously alloying element and contaminant.

And silicon is soluble in the relevant range in alpha iron.

It's a ferrite stabilizer, which you can pretty easily see if you look here.

So ferrite stabilized

but usually we don't put in so much silicon that this really comes

into play to the extent that it would with chromium, for example.

We then have a fully ferritic steel.

It's present from deoxidation

desoxidation

and obviously also blast furnace and so on.

And usually forms non-metallic inclusions

which in most steels we will not have any

or not much free silicon in the steel.

The reason for that is it's a very

very strong solid solution hardener.

And with its strength in twice solution hardening

but also in pretty less steel pretty significantly.

This is why we usually want to get rid of the silicon as much as we can.

But about half a percent is typical as a residual.

And exceptions are steels for magnetic properties

but this is a completely different topic where

we use the silicon to produce a specific texture

so crystal orientation

preferential crystal

orientations

and in heat resistant steels to form a more stable oxide.

But this is a very special topic

and these are very low production volume steels.

Of course, maybe not the steel for magnetic properties.

So this is steel for magnetic properties that I'm talking about, it's so-called transformer

sheet steels, soft magnetic steels.

And I guess these days they're becoming more and more important, especially with electric

cars.

One I forgot in this list was spring steels

also very typical spring steel alloys

silicon chromium 7.

So in this case

the silicon is used as a solid solution hardener because in the spring

steel we don't care about plasticity because the part's never going to see plasticity just

simply because of its shape

the spring.

And importantly

it's in equilibrium with the slag