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--Normally cracking in Austenitic stainless steels may be Solidification cracking. Solidification cracking occurs because of below reasons.1. Presence of Impurities like Sulphur, Lead, Arsenic etc..2. Weld Bead i.e Width to Depth Ratio3. Time duration between Liquidus and Solidus curve during cooling.But I do not think the cracking being discussed is Solidification cracking as this type of cracks occurs in crater with Branches.I feel this cracking at start and End is due to Welder or Technique. Sudden removal of Filler creates shrinkage stresses which results in cracking and I suppose it is due to shrinkage stresses and restraint.Nowadays GTAW welding machines have Facility with PreFlow and Post flow of Shielding Gas which could be of one option and second option is to use correct Bead size while starting and finishing not necessarily a Key Hole Technique to be followed.Thanks & Regards
J.Gerald Jayakumar
0091-9344954677
On Wednesday, November 1, 2017, 12:29:43 AM GMT+4, PGoswami <pgoswami@quickclic.net> wrote:--
These cracks are Centreline or Hot Cracks .I've attached a picture of the same from the book. The contributing factors could be :-
1. Technique wise—
· Too fast or Jerky removal of the filler metal from the weld puddle, gradual or slow removal of the filler from the weld puddle may help sometimes.
2. Filler metallurgy wise:
· check what's the ferrite no for the weld deposit. Typically for 347 H one would require 6 TO 8FN or more in the deposit to avoid cracks.
· Check what's the Nb:C ratio. It should be 8 Max. Higher values(i.e. more Nb in the weld) could contribute to cracking.
3. Filler Batch/ Box Specific:
· Try welding with filler from another box or batch no, see if it helps
I'll look forward to your response.
Thanks.
P.Goswami.P.Eng, IWE.
Welding & Metallurgical Specialist
Linkedin: https://www.linkedin.com/in/
pradip-goswami-2999855/ Email:pgoswami@quickclic.net,p
radip.goswami@gmail.com
Fig.3. Buried centreline crackiFig.3. Buried centreline cracking Fig.3. Buried centreline cracking ngFig.3. Buried centreline crackingFig.3. Buried centreline cracking
Fig.3. Buried centreline cracking
From: Amul Raj [mailto:win.amul@gmail.com]
Sent: October 31, 2017 8:35 AM
To: Pgoswami@quickclic.net; pradip.goswami@gmail.com
Subject: Heater coil welding getting Crack - Reg
Dear Sir, Good evening.....!
In our project hydro cracker unit, Heater radial coil welding base material 347H and filler material ER347H(Metrode), size 4" X 13.49 Thick
When we do the welding, getting Crack in the weld start and stop point
Please advise me sir
Thanks and Warm Regards
Amul Raj T
PSCJV
+965-66310230
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
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