Re: [MW:27446] Impact test failure ( pipe to Flange )

Heat input will affect notch toughness considerably .The change in toughness is not just tied to the heat input, but is also significantly influenced by the weld bead size and travel speed as one welds. As the bead size increases, which corresponds to a higher heat input, the notch toughness tends to decrease. In multiple-pass welds,  a portion of the previous weld pass is refined, and the toughness improved, as the heat from each pass tempers the weld metal below it. If the beads are smaller, more grain refinement occurs, resulting in better notch toughness. Also consider better,  more uniform preheating by utilizing heating pads and thermocouples. My suggestion is to weld with smaller weld bead sizes and increase travel speeds. Allow adequate time between passes for cooling. Use resistance heating pads and thermocouples for better heat control. I hope this helps.

小金

On ‎Saturday‎, ‎March‎ ‎3‎, ‎2018‎ ‎10‎:‎13‎:‎26‎ ‎PM‎ ‎CST, TDK YOKESH <tdky167@gmail.com> wrote:

Dear Gents , 

We carried out PQR for a pipe line job between pipes to flange. Details are as below

Pipe Material: ISO 3183 X65

Flange material: A694 F65

Service: Sour

Size: 20" x 44.45mm

Welding Process: GTAW + SMAW

Preheat: 125°C (using propane heating torch)

Welding Consumable :  ESAB ER80S Ni-1 ( GTAW ) for root pass , Hot pass and Fill-1 pass , ESAB E8018C3H4 R ( 3.2mm and 4mm ) for fill passes and capping .

PWHT Temp: 600°C for 2hrs 10mins

Ceq : 0.40

The coupon failed in Charpy Impact Test at -40°C at weld Root center line with low values (16, 26, 18 Joules).

The PQR was carried out going ensuring a two propane Heating torch to ensure an equal preheating is done on the OD and through thickness. Interpass temperature was not below the Preheat temp. The coupon failed again in Charpy Impact test at -40°C at weld Root Centre line (18, 18, 28 Joules) and at Root Fusion Line+2mm (19 joules) at pipe side. The Max hardness was 234HV10 (root HAZ) which is below 247HV10 .

How do I overcome this and what should be the root cause.

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Best regards,

TDK YOKESH

PH : +917092847368

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