Dear Mr. Mohamood,
ER310(modi) Thermanit 25/22H or ER310LMo Sanvik 25.22.2 LMn – Super austenitic stainless steel filler metal would be the better choice for welding/repair on urea grade 316L materials, since it will produce 100% austenite at all temperatures. The erosion corrosion would be more likely to occur in the welded area where there are high stress concentrations and HAZ as well due to high pressure/temperature involved in urea reactors.
For information, the best choice for urea reactor lining should be with Titanium in order to avoid erosion corrosion problems since it involves with high pressure and temperatures. (In my previous employer, we have carried out many reactors with 5mm Ti lining. Again it is depends on operating pressure/temperature and other service conditions)
In fact ER316L (modi) would meet the requirements of ferrite and better resistance to corrosive environments in urea reactors. Please check the ferrite content in the welds, it should be < 1% to avoid corrosion cracking and other related problems. The selection of filler metal from the selected manufacturers would be helpful since very limited manufactures are available to produce SS electrodes with nil ferrite such as Avesta, Sanvik etc.
In general welds in urea reactor shall have nil ferrite or less than 1 % ferrite in order to avoid stress corrosion cracking problems. One of the disadvantages of Ferrite will reduce resistance to stress corrosion cracking in service environments like urea reactors. In such cases, the weld metal is added with more than 5% Mn to take of hot cracking problems.
Regards,
L. Prabhu kumar,
Sr. Principal Engineer,
Equipments & Materials Dept.,
Saipem India Projects Limited,
Tel:+91 44 43906588, Ext.: 588, Fax:+91 44 66840345,
Mobile Ph. No.: +91 9003010978.
From:
Sent: Thursday, June 24, 2010 3:56 PM
To:
Subject: [MW:5732] Urea reactor lining repair
Dear Mr. Prabhu Kumar,
We are using ER Thermanit 19/15H for restoration of lining welds of our Snamprogetti Urea reactor. Material of lining is 316-L (mod) Urea grade. But after one year of service the repaired welds again undergo erosion/corrosion. Can we use ER Thermanit 25/22H instead, for a better life of repaired welds?
Regards,
Mahmood
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