i think ,this chose is best because the service condition induceed the H embrittlement or cold crack even after days or months.therefore for reducing the probability of this crack ,the total strength of weld metal must be less than base metal and strain occur in weld not base.
From: Ari <ariv2k@gmail.com>
To: Materials & Welding <materials-welding@googlegroups.com>
Cc: pssadanandan@yahoo.com
Sent: Thursday, March 19, 2009 1:45:44 PM
Subject: [MW:1784] Query on SMAW electrode selection for API 5L X65
Dear All,
Can you please advise, why E6010-G (root) & E-7010-P1 (hot/fill) are
used for Oil pipelines(Sour) containing parent material of API 5L X65..
Since these type of PQR/WPS are being approved by most of the
Company.
As, X65 has an YS of 65,000 Psi, whilst the electrodes used E6010 has
YS of 48,000 Psi, and E-7010-P1 has YS of 60,000 psi. By using both
of these electrodes the weld metal strength would not exceed YS
60,000 psi.
How its acceptable to keep the low weld metal strength(<YS 60,000 Psi)
than the parent metal (= YS 65,000Psi).
Thy suppose to use E8010 for root and E8018 for hot/fill, for API 5L
X65 materials, which only would give the equivalent WM strength.
As we all know that overmatching weld metal strength causes gross
section yielding in the pipe, whereas Undermatching weld metal
strength will cause straining of the weld.
Your advise/suggession, based on experience is appreciated.
Regards,
Ari
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