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: materials-welding@googlegroups.com [mailto:materials-welding@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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