Mr. Gandhi,
Please see the attachment, with the red arrow in page 2.
If the austenitizing temperature is around 1020 Deg C , the misconstrue would be predominantly austenite as it is in the austenite phase region. This after quenching the austenite would be more in the microstructure.
If you're going past 1100 Deg C or more(1150 Deg C preferably) , the microstructure would be in 2 phase region, ferrite+austenite. A soaking at this temperature (1 hr/inch ratio) would be useful to stabilize the ferrite /austenite phases through diffusion. Quenching from this temperature would be helpful to balance the austenite and ferrite ratio.
Hope it would help.Feel free the share the results/outcome as good gesture.
Regards.
Pradip Goswami, P.Eng,IWE
Welding & Metallurgical Specialist
Ontario, Canada
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of CHINTUKUMAR GANDHI
Sent: Sunday, February 16, 2014 5:37 AM
To: materials-welding@googlegroups.com
Subject: [MW:20111] Reduction in % ferrite of UNS S31803 weld after Post forming HT
Dear Experts,
In one of our project, one coil pipe to pipe butt weld was undergone PWHT @ 1080º C. for 12 minutes soaking period and rapid water quenching after forming a pipe in coil form. Pipe size is 21.3 mm. O.D. X 2.77 mm. W.T. SA 790 UNS S31803. We have used ER 2209 filler wire with GTAW process.
After solution annealing, % ferrite was measured 8-10 using fisher make calibrated ferritescope instead of required 30-60%. PQR was established in the same pipe size and material Grade. In PQR, after PWHT @ 1020º C. for 10 minutes and rapid water quenching, % ferrite was coming average 38 in point counting method as per ASTM E 562.
What shall be the reason of reduction in % ferrite in production weld? What shall be the corrective action to achieve % ferrite between 30-65%. In this forum, some where I have read that heating to temperatures approaching 1100º C will dissolve some or all of the ferrite, depending on the hold time at temperature, composition of the weld metals, and the as-welded ferrite content. I need some reference book on this issue.
Thanks & regards,
C. R. Gandhi
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