Definition of buttering from ASME Section IX, QW/QB-492 Definitions:
Buttering: the addition of material, by welding, on one or both faces of a joint, prior to the preparation of the joint for final welding, for the purpose of providing a suitable transition weld deposit for the subsequent completion of the joint.
Simply it is weld build up of (one or both) base metal(s) before beginning to weld the joint itself. This can be done in order to make up for poor joint preparation as indicated previously, but also is done to minimize the effect of PWHT on a sensitive material or eliminate subsequent PWHT. For the latter cases a couple of examples may be in order:
1. If you wanted to weld P91 pipe to a stainless steel pipe, ASME Code would require a PWHT of the P91 at nominally 1400F (760C). This temperature would, however, “sensitize” the stainless steel (cause carbide precipitation along the grain boundaries). One way to eliminate this problem is to butter (or overlay) the P91 with ERNiCr-3 (or similar weld material). The thickness of the butter must be sufficient to avoid the weld heat affected zone from extending into the 91 during completion of the weld. You would then PWHT the buttered P91. The joint would be completed by welding the stainless steel pipe to the ERNiCr-3 butter with ERNiCr-3 material and no subsequent PWHT would be required.
2. A steam turbine manufacturer I am familiar with used to butter 2 ¼ Cr – 1Mo casing materials with carbon steel at some nozzle connection sites where it was undesirable to have stubs. The casing was heat treated prior to final machining. In the field carbon steel nozzles/pipes were welded to the carbon steel butter with no subsequent PWHT.
ASME Section IX, QW-283, discusses and governs welding procedure qualification when buttering is to be performed. While not complex there are some significant details that need to be paid attention to. I would suggest that peruse this section of the Code and if enquire further if you have subsequent questions.
Hope this has helped.
John
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of faisal hanif
Sent: Saturday, June 12, 2010 4:02 PM
To: materials-welding@googlegroups.com
Subject: Re: [MW:5566] Buttering of weld joints
| Well Das,
Dear Sir Can anyone describe me what is “BUTTERING” stands for in welding joint. If it is done before depositing the weld metal on job, is it necessary to remove the same by back chipping. -- |
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