Charpy Impact Test Temperature Reduction Below Minimum Design Metal Temperature for Combination of Welding Procedures

i am making one PQR of circumferential seam butt weld of pipe having thickness 8 mm.
it is welded with two processes.
GTAW from root side - thickness 4 mm.
SMAW from top side - thickness 4 mm.
MDMT is -18°C.
Impact test samples are prepared from both welding process deposited weld metal and having width at notch equal to 2.5mm.
now my question is that as per ASME sec-8 div.1 UG-84 how much temperture reduction I have to do during testing? is it as per base metal thickness or deposited weld metal thickness? so is it -46°C or -29°C?

IMHO See UG 84(g)(4) paraphrasing, 'test temp for welds and HAZ’s shall not be higher than required for base metals.

Hello @123

Subsize specimens: reduction temperature follows Table UG-84.2.

Temperature reduction -0 deg. C.

Determine MDMT: Figure UCS-66.2 Diagram of UCS-66 Rules for Determining Lowest Minimum Design Metal Temperature (MDMT) Without Impact Testing.

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