Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: welding weird stainless steel

[Subject Prev][Subject Next][Thread Prev][Thread Next]
In the case of (some) austenitic stainless steels, chromium carbides may
precipitate at grain boundaries when cooling, e.g., from welding
temperatures. This leads to chromium-starved areas adjacent to the
chromium-rich carbides (i.e., at and around the grain boundaries) - the
phenomenon called "Sensitization". These depleted areas are highly subject
to corrosion attack, especially in acid service. The chromium carbides that
are formed tie-up the chromium preventing it from forming a passive chromium
oxide layer on the material.  The chromium oxide layer, though only a few
atoms thick, prevent corrosion from occurring.

To restore the corrosion protection the material must be SOLUTION ANNEALED
(same as CARBIDE SOLUTION ANNEALED).  Summarizing the process; heating a
finished fitting to over 1,850 degrees F. and cooling it quickly, usually in
water, so carbon content goes back into the stainless solution.


Richard M. Beldyk, PE, CPEng, NSPE, MIEAust, AIT, CWEng, CPE

Professional Engineer - Delaware, Maine, Maryland, Michigan,  New Hampshire,
Ohio, Pennsylvania, Virginia, West Virginia
Chartered Professional Engineer - MIEAust, NPER
Registered Member - International Registry of Professional Engineers
NASP Certified Accident Investigation Technician
AWS Certified Welding Engineer
AFE Certified Plant Engineer

This message is intended for the use of the individual to which it is
addressed and may contain information that is privileged and confidential.
If the reader of this message is not the intended recipient, you are hereby
notified that any dissemination, distribution, or copying of this
communication is strictly prohibited.  If you received this communication in
error, please notify the sender immediately.  Thank you.

Outgoing mail is certified Virus Free by the use of AVG  Virus Protection
Checked by AVG anti-virus system (
Version: 6.0.719 / Virus Database: 475 - Release Date: 7/12/04

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*   Questions to seaint-ad(--nospam--at) Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: 
******* ****** ****** ****** ******* ****** ****** ********