low temparature steel welding

By trantrung77 Date 07-22-2014 09:33

Gentlemen,

I am trying to weld FH36 with flux core K81-T (Kiswel with 1% Ni) and test it at -60 degree C, 34J but it is always fail (20 J).
The setting is:
Setting 1: current 240 (A), Voltage 24 (V), interpass temperature: max 60 degree C.
Setting 2: current 220 (A), Voltage 24 (V), interpass temperature: max 60 degree C.

The result for both setting are same (20J).
Could anyone tell me how to improve this impact value?

Thanks very much,

Trung

By js55

Date 07-22-2014 13:44

That temperature can be problematic with fluxed processes and that Ni content. You either need to go no flux (GTAW) or bump the nickel.
You also need to control your travel speed. Small beads, low heat input.
If its a small job you might just go with an austenitic.

By trantrung77 Date 07-23-2014 07:19

Thanks for your advice. I want to qualify our WPS with this material (FH36). I tried to increase the speed to have the small beads, the test plate thickness is 13mm with V joint and I did 11 runs but the result are not stable, some sample reach 50J but some sample was 18-20J.
My product is heavy structure so I need to consider the cost and the productivity, GTAW is too slow. Is GMAW more stable than FCAW shield gas?

By js55

Date 07-23-2014 11:46

My advice would be to go safe and bump the alloy content as opposed to playing with processes. The process change can do it but seldom do we have time to establish a firm empirical basis for qualification success. The problem with GMAW is that spray will lend itself to higher heat inputs and short circuit is out of the question for heavier walls.