E71T-1 toughness

[GRoberts]

We have had fairly good luck with the particular brand of E71T-1 FCAW wire we use when testing CVNs at -50F after 1125F PWHT. Recently one of our customers specified an 1175F minimum PWHT temperature. After 1175F, the CVNs did rather poorly at -50F. (We also tested E7018-1 in parallel, and of course it did wonderfully) Anybody have any luck with low temp CVNs using a carbon steel FCAW electrode after 1175F or higher PWHT? We are just welding carbon steel, so most of the non-carbon steel electrodes we have used that would perform well at -50F severly overmatch the base metal with regards to strength, or have more than 1% Ni, and we have to meet NACE.

 

[weldtek]

I have data after 1200 F for 3.5 hours, but only at -40F. They weren't great but met Code.

 

[GRoberts]

Thanks weldtek,
Any word on what your results were, and what brand/trade name you used?

 

[weldtek]

The base metal was SA 516-70, 2" thick. Consumable was Hobart Trimark Triple 8, .o45" diameter with CO2 shield.
1/16" from Cap we had 16,20,& 14, 16.6 avg, and at 1/4 T from root we had 29,27,& 34, avg 30.
I'd be interested in knowing which brand you were having success with.

thanks,

John

 

[GRoberts]

Kind of ironic. We are also using Tri-Mark Triple 8- all 1/16" diameter and CO2 sheilding.

We have taken CVNs from the cap on a 3G test(3/4" weld on 1 1/2" plate) with SR at 1125F for 18 hours, and got 24, 31, 39 ft-lb at -50F. Also did 1125F for 8 hours on a 1G conformance test and at -50F we got 85, 68, 154, 60, 15 ft-lb (Per AWS- throw out high and low). We have had Tri-Mark also test several lots for us at the factory with 1125F PWHT and haven't had problems with -50F CVNS.

Our results with 1175F PWHT for 12 hours were 6, 10, & 4 ft-lb and 1175F for 1 hour were 5, 7, & 5 ft-lb(3G 3/4" weld on 1 1/2" plate).

Based on the difference between the 1G (heat input of 37kJ/in) and 3G (60kJ/in test at 1125F PWHT temp, we are going to try 3G with lower heat input to see if that will have any affect.

 

[GRoberts]

Weldtek,
In case you are interested in what happened, I was surprised by our results from the lower heat input test. Based on the dysmal result from the 3G test with about 60Kj/in, I did not think lowering heat input would make enough of a difference to get acceptable results. We did run 2 new plates at about 30kJ/in, and after 12 hr at 1175 and 1 hr at 1175, got results from 30-60 ft-lb (approx) at -50F. I was surprised, but it was a good surpise for a change.

 

[weldtek]

GRoberts,
Thanks for the followup. Very interesting. Based on your earlier post I assume you're talking about values in the weld metal and that's a pretty dramatic difference. Just to confirm, did the values improve in the weld metal or just the HAZ?
Thanks,

 

[GRoberts]

HAZ values were still good, but actually decreased from the previous test with the lower heat input. Now that I have the data in front of me (doing it from memory last night)- the long heat treat weld metal averaged 85, and the short heat treat weld metal averaged 40.

Actual heat input (averages) were 35 and 57 kJ/in.