Acceptable Range of Impact Test Values
SA
Alan Denney
If you were asking why there is a difference that is much more complicated, but it is a question of the selection of the consumables, the welding heat input and number of passes and the grain structure and degree of refinement of the weld metal. Look at the macros and if the grain structure looks much coarser that is the indication.
By the way the decimal is of no significance in Charpy testing – just work to the whole numbers.
Alan Denney
AKD Materials Consulting Ltd
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John Henning
The why is simple. You are trying to establish that your weld metal and base material heat affected zone, for a given set of welding parameters, are not below the ductile to brittle transition temperature (DBTT) at the required test temperature. The test temperature typically the MDMT (for ASME VIII) or other temperature specified in the contract documents.
As long as you above the acceptance value, this should provide some assurance that the welds and HAZ’s are precluded from brittle fracture in the final product.
From: material...@googlegroups.com [mailto:material...@googlegroups.com]
On Behalf Of SA
Sent: Tuesday, October 06, 2015 7:55 AM
To: Materials & Welding
Subject: [MW:23671] Acceptable Range of Impact Test Values
Dear All,
There are two PQR's and both are qualified with a coupon of 16 mm thickness. The one is qualified with Submerged Arc Welding (SAW) and other is qualified with Shielded metal arc welding SMAW. When impact testing was done on weld and HAZ of samples taken from both coupons, it showed a lot of difference between impact test values keeping same test conditions. The lowest impact value of sample from SMAW coupon is 143 joules whereas sample from SAW coupon has lowest impact value of 35.1 joules. Is this difference accptable and why?
Waiting from your valuable feedback.
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Saravanan Sornam
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Rems Okonkwo
Well the answer to your question is dependent on so many variables which you did not state here. The type of Materials, the consumables used for both SMAW & SAW. For the SAW, the wire fluxes combination. The welding parameter with respect to heat input. Generally, SAW weld generally have low impact property when compared with SMAW weld for plain carbon steel. E.g, E7018-1 will have a better impact property compared to F7A8-EM12K at weld metal. But in all, the most important is that you met the requirement as specified in the Code or Design.
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