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304L Tubing Not Austenitic

304L Tubing Not Austenitic

304L Tubing Not Austenitic


 The 304L tubing is quite 'responsive' to a small
magnet, especially on the seams.
 Can this be removed by annealing? If so, at what temp.?
How quenched? ie let cool slowly, or quickly in water?
 This tubing has 'high-polish' finish. Will be used in
a water purification project.
 Alternatively, does anyone know a source for truly
austenitic tubing, 304/L or 316/L? (1" thru 4" dia).
 Thanx much for any/all guidance.  

RE: 304L Tubing Not Austenitic

The fact that your specific tubing is slightly magnetic is due to its having been cold drawn, or strain hardened. It is still fully austenitic.
That should not impair its resistance to corrosion.
If you subject the tube to annealing it will lose its finish, will build up an oxide layer and even scale, unless you do so in a vacuum furnace.
Annealing temperature is about 1050 deg C.
Small items are usually quenched in water, to avoid long permanence at sensitizing temperatures (about 600 to 900 deg. C)
While welding or brazing the tube will be annealed locally.


RE: 304L Tubing Not Austenitic

Was the 304L tubing ordered to a specific ASTM Specification? If so, what was the specification?

RE: 304L Tubing Not Austenitic

To: metengr;
 No spec specified. Supplier said it met ASTM 269
&/or 270. I would have to go look it up.
 RE: goahead's reply; I could live with doing a re-polish.
However, I'd hate to think about it scaling.
 Since I have over $100 invested in the material, it may
be better to return it, as they said I could. They also
said they couldnt supply any tubing that was 'austenitic'. (?)
 I'm a retired IBM mainframe programmer, thus I've no related
experience dealing in my new 'experiemental field.
Regards, jcell39

RE: 304L Tubing Not Austenitic

I feel I should qualify my answer above.
In terms of metallographic studies it may in fact occur that not 100% of the structure is indeed austenitic in the cold drawn tubing. Testing to determine that, is based on the control of the crystallographic structure my means of X-Ray diffraction.
As I see it, this should not have any bearing on material  usability.
In any given environment a certain material is or is not corrosion resistant for the design life.
If it can be determined or if it is known that the material is adequate for the application, the question of fully austenitic structure is probably insignificant.
One should remember that even fully martensitic stainless steel can resist corrosion if appropriate to the application.


RE: 304L Tubing Not Austenitic

The material is slightly magnetic becuase the welds are under annealed and have a significant amount of retained delta ferrite.
Unless you specify that you don't want it, this is what you will get.  None of the tubing specs require that the material be non-magnetic.
There are two ways to do this.  One is to order to A249 with Suplemental requirement 7 (A249 S.7).  In order to pass this test the tubing will have to be annealed better.
The other option is to place a magnetic permiability limit on the tubing.  A common limit is 1.05.  You can measure this with a number of simple devices.  If this matters to you then you should own one.

If magentism matters in you use then you have problems.  If you intend on using the tubing in an acidic environment then you will see accelerated corrosion of the welds.  Other wise this is not an issue.

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