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Up Topic Welding Industry / Metallurgy / AL 409 HP ALLEGHENY LUDLUM STAINLESS STEEL
- - By YVAN (*) Date 03-03-2008 13:24
Looking for someone who has used this stainless steel. My concern is about intergranular corrosion of weld heat affected zone.

Thanks for helping me,

Parent - - By Milton Gravitt (***) Date 03-03-2008 14:21
Have you did any research on this type of SS because there is a lot of info on google.
Parent - - By YVAN (*) Date 03-03-2008 15:31
Yes I did but found nothing about intergranular corrision in weld heat affected zone at the exception of Allegheny Ludlum Technical Data Blue Sheet.

I would like something coming from others than Allegheny.


Parent - - By G.S.Crisi (****) Date 03-05-2008 19:42 Edited 03-05-2008 19:49
I don't have the chemical composition of AL 409 HP on hand, but I suppose it shouldn't be very different from plain AISI 409.
AISI 409 is a stabilized ferrtic stainless steel that contains
Carbon: 0.08 % maximum
Chrome: 10.5 to 11.75 %
Titanium: 6 times the carbon content minimum.

The titanium content indicates that 490 is a stabilized stainless steel and intergranular corrosion shoudn't be a problem when welding it.
Giovanni S. Crisi
Sao Paulo - Brasil  
Parent - - By DaveBoyer (*****) Date 03-06-2008 04:57
Giovanni, Does the titanium combine with the carbon to keep it from forming chrome carbides in a material like this?
Parent - - By js55 (*****) Date 03-06-2008 14:33
Absolutely. The kinetics of Ti versus Cr carbides essentially works no matter what material these elements exist in together, because Ti is more 'aggressive' (certainly not the kinetically accurate term ) at combining with C than Cr.
Even in other alloy families the kinetics will hold. Its just that its not called stabilization.
Parent - - By rlitman (***) Date 03-06-2008 22:19
In general terms, it is because Ti has a lower "electronegativity" (or higher electropositivity, but you never really hear it said that way), than Cr.
To be really specific, this is the same method as galvanic corrosion, and this is because Ti has a lower "Reduction Potential" than Cr.
You can see this on an electrode potential half-reaction chart, which would list electrode materials, ordered by their voltage potentials.
To give you a general feel of "aggressiveness", here's a list of common anodic metals you probably encounter regularly in decreasing order of aggressiveness:
Sn (tin)
Fe (iron)
Any metal above iron in a chart ordered like this, could be used to protect iron from oxidation.  The higher it is, the more aggressively it protects iron, BUT there's alot more than that involved, when selecting something for anodic protection.
Parent - By js55 (*****) Date 03-07-2008 14:17
Good info Robert. You need to stop by a little more often.
Parent - - By G.S.Crisi (****) Date 03-06-2008 21:38
I havn't understood your comment (after all, English is not my mother language).
What Dave says is what actually takes place when welding a stainless steel containing titanium. Titanium has more affinity (that's the right chemical term) for carbon than chrome, so titanium combines with carbon and leaves chrome untouched (leaves chrome free, is the right chemical term). 
What I didn't understand is whether you agree or not with this statement.
Giovanni S. Crisi
Parent - By js55 (*****) Date 03-06-2008 22:13
Yes. I agree.
Affinity. thank you.
Parent - By DaveBoyer (*****) Date 03-07-2008 05:12
Thanks everybody, I was pretty sure that is how it works, but I wanted to confirm.
Up Topic Welding Industry / Metallurgy / AL 409 HP ALLEGHENY LUDLUM STAINLESS STEEL

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