Hi,

I have done PQR with A560 (50Cr-50Ni-Nb) # A387 Gr. 91 combinations 2 times and landed in crack developing at A560 side HAZ locations.

1st coupon:

Single V with Back chip, thick 35 mm, SMAW process, ENiCrFe-3 electrode. After completion of front side welding crack developed at back side A560 side HAZ location in welding direction.

2nd coupon:

Double V, thick 35 mm, SMAW process, make buttering of 5 mm on A387 Gr.91 side, post heat done followed by PWHT and proceed welding with ENiCrFe-3 electrode.After completion of 3 passes in front side, we chip back and did DPT and observed crack developed at A560 side HAZ location tranverse in direction.

In both coupons preheat done on A387 Gr .91 side with 200 deg C and interpass maintained during welding with <300 deg C.

Need help in this regards that how to proceed welding without crack.?

Thanks in advance.

Regards,

Navaneeth.