Steel with 4% Boron 4

[Bob167]

Can anyone tell me if low-carbon steel with 4% boron (as used for nuclear control-rods) would still be magnetic ?

 

[NickE]

I believe so since the x-tal structure will still be BCC.
nick

 

[Bob167]

Dear NickE,

Thanks for such a rapid response.

Do you definitely KNOW that the iron structure will be unchanged ?

I appreciate that Boron is a small atom, but so is Carbon.

4% sounds a helluvalot to me
- but then, I'm not a metallurgist !!!

Regards,

Bob

 

[NickE]

That is alot of boron, typically boron is added to the low carbon steels to aid in quenching response, IE: hardenability. Normal ranges for boron are: 0.0005-0.003%wt.

I'm really not sure (i'd give the star back if I could....)looking at the B-Fe phase diagram you should,at temps below 912C still be in the alpha-Fe region.

Go here for the phase diagram....

http://cyberbuzz.gatech.edu/asm_tms/phase_diagrams/pd/b_fe.jpg

Thats about all I've been able to locate....

nick

 

[hacksaw]

Boron has only limited solubility in either gamma or alpha phases of iron, so the curie temp and magnetization are only slightly affected up to 8.9%.

 

[NickE]

Thanks hacksaw.

Bob167, the 8.9% that hacksaw states is the line where Fe2B intermetallics form....

the Fe-4%wtB you speak of should be magnetic.

 

[Bob167]

Thanks again Nick,

I appreciate that this is an area of fairly limited interest. The steel in question was made in the sixties for nuclear use; much has been forgotten and many records are lost. So every bit of information is useful.

Regards,

Bob

 

[Bob167]

Dear Hacksaw,

Thanks for your contribution.
I've had great difficulty getting information on this one - the actual owners of the items cannot even be certain what the composition really is !!! So there is a lot of guessing going on. Every piece of information is useful and I appreciate your help.

Regards,
Bob

 

[hacksaw]

you should be able to determine the boron content easily enough with access to a testing lab. I suspect that the main effect is going to be embrittlement, though you will see a lot of changes in the magnetic loss and coercivity but not the other properties, once you start getting more than a few tenths of a percent.

the solubility of B in iron is limited.

there is quite a bit of data on FeB, it is just not on the internet.

 

[Bob167]

Thanks Hacksaw,

Sorry to be so long replying; I had other work for the past fortnight but the Boron problem will be back on the agenda when our sample comes back from cutting trials.

The magnetic properties of the material could be an important feature of the work, so thanks for highlighting it.

Regards,

Bob

 

[sreid]

Just one pratical thought. See how well it sticks to a permanent magnet Compare the pull off strength to mild steel.

 

[Bob167]

Dear sreid,

Thanks for the tip.

The only snag is that there are two types of components; one is plain mild steel, the other (allegedly)contains boron in some (unspecified) form or other. We only have a sample of one of them and no-one is certain which !!!

(sounds like a question in the Mensa entrance test !!)

But every piece of advice is very welcome,

Thanks again,

Bob

 

[hacksaw]

the primary effect of boron is to increase hardness.
that can be quantified with a simple test.

the best bet is to drop a piece off at the local testing lab. a surface scan is pretty cheap(comparitively).

 

[Bob167]

Thanks again Hacksaw, I'm certainly getting value on this one.

The item is inside a stainless steel sheath. We managed to reach it with a swiss file and it seemed considerably harder than normal mild steel - but there could be several other explanations for that.

At the moment the sample is away for other tests.

The saga continues .....

Regards,

Bob

 

[nbucska]

the 4% doesn't define the distribution of the B but the
magnetic properties may change significantly while
the neutron adsorption won't change.

<nbucska@pcperipherals.com>

 

[Bob167]

Thanks nbucska,

Not quite the answer we were hoping for!! sigh! but even the bad news helps us to determine the strategy that is most likely to succeed.

To be honest, at this point no-one is 100% certain of composition.

Thanks again,

Bob