Okay

so today we're going to continue and this is the recording for everyone that couldn't

make it in the snow chaos of 2026.

So last week we stopped at alloying elements

specifically alloying elements that we haven't

covered before.

They're usually relatively specific in what they do to the product groups and we'll just

go through them a little bit more in general and then we're going to look at the effects

of those a little bit more in detail when we get to the actual product groups.

Some fundamentals we've already looked at like diffusion coefficients and phase forming

tendencies like chromium, iron chromium system.

So chromium

so these are some of the most important alloying elements of chromium ferrite

form are very importantly.

So we have two main applications of chromium and the first one is to increase the hardenability

to increase the hardenability and to increase the corrosion resistance.

These are the two main applications for chromium corrosion resistance.

Usually we're talking about wet corrosion.

We'll get to that when we when we get to corrosion resistance deals in the summer semester

but

essentially any amount of chromium improves the corrosion resistance through forming a

more and more stable oxide.

Even the oxide hydroxide that's regular corrosion

the regular corrosion product is more dense

with chromium, so even lower corrosion rate.

But if we are above 10.5% chromium

we start getting a dense oxide typically in order to

also take into account the segregation and so on.

So we have 16 to 18% for fully dense oxide in practical alloying.

This gives us a corrosion resistance deal.

We also put it in to increase high temperature oxidation resistance up to about 750 degrees

Celsius above 750 degrees Celsius.

The chromium oxide is just the ion conductivity goes through the roof and then we'll have

to use more stable oxides.

Next one is manganese.

So manganese

maybe it should be solid a little bit more.

So manganese is typically

the most important point is not here

typically it's a solid

solution hardener.

And at low concentrations up to about 1.5% to 2%

it doesn't do much else.

It goes into iron carbide

so if you have Fe3C

it's Fe manganese 3C really.

And so it's a pretty convenient element because it doesn't do much about the

except for the

solid solution hardening.

Of course