Dear Mahendran,
Since the material (A335 P22) is highly hardanable after welding, you can try with the following precautions/ restrictions to reduce the hardness level.
- Use increased preheat i.e. 250ºC
- Follow temper bead technique as suggested in QW-290 of ASME Sec. IX.
- Post heat immediately after welding – 250 to 300º C for 1 hour and cover the weld area with thermocool in order to reduce the cooling rate.
- Qualify welding procedure with E8018-B3L / ER80S-B3L (low carbon grade) instead of E9018-B3/ ER90S-B3 to reduce chromium/molybdenum carbides, which will increase the hardness of the weld.
Note: Though B31.3 & Sec. VIII Div. 1 allows upto 13mm or 16mm without PWHT, most of the client specification calls for PWHT for all thicknesses for this material due to more prone to hydrogen induced cracking and highly hardanable (air hardening) after welding. Check once again for the requirement of PWHT.
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: Tuesday, June 08, 2010 10:01 AM
To:
Subject: [MW:5437] How to control the hardness in P22
| Hi all, May any one tell me, how to control the hardness of the P22 materials welding without PWHT. Even, we do pre-heating as per the ASME 31.3 & also we use 2.6mm dia electrode(E9016/8). Still we get the hardness around 290 HB. Any suggestions to control the hardness within 241 HB(ASME 31.3). Please help. Thank you. Best regards, P.Mahendran |
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