Welding Tips and Tricks

Hi,
I have an old wps which I am trying to correct as per D1.1 It's for TIG welding of 1/2" inch thick plates with V-butt joint in flat position. It states 6 passes with 3 layers(1-root, 2&3-2nd layer and 4,5,&6-3rd layer). It specifies following parameters for all passes with 3/32" filler diameter.

Voltage : 20-21 V
Current : 100-160 A
Welding speed : 2.5 in/min

Is it advisable to use TIG only for the root pass or all the passes or the rest of passes with MIG. The amperage range for TIG should be higher than above and also for higher passes. Please let me know if I am right on this one and what should be these values. Also, what should be the interpass temperature requirements?


Thanks
Pranav

What exactly does that WPS say? Because you're not going to convince me that you can tig weld 1/2" plate with only 3 layers of 3/32" filler rod.

Tig welding all the way will be cleaner, but slower. If the WPS doesn't specify GMAW then I wouldn't worry about it.

As far as interpass temperature; don't let it freeze and you'll be fine. Seriously. D1.1 Table 3.2 Prequalified Minimum Preheat and Interpass Temperature doesn't specify a temperature for the GTAW process, but for the processes it does list the highest preheat/interpass is 50F for 1/2" thick material.

The WPS does mention GTAW for all passes for 1/2" thick plate with 3/32" filler rod.
It also specifies same amperage, volt and speed range for all passes which I like to question since I guess these values should be different from those used for the root pass. Also, if I add GMAW for higher passes, what would be the difference in these parameters and would it need any process qualification?



Thanks for the reply
Pranav

Under D1.1 GMAW-S has to be qualified. The "S" is for short circuit/arc. Spray transfer and globular do not need to be qualified.

The parameters are going to differ because of how different the processes are. GMAW will (typically) be DCEP, you'll have a range on the wire feed rate, the gas will most likely be different, and the wire will probably be of different composition and definitely a different size.

I'm not sure if you need a separate WPS for a separate process on the same weld. And I'm not a CWI so I don't want to give any misleading information.

You also have to qualify GTAW under D1.1. GTAW and GMAW-S are not pre-qualified processes under the D1.1 welding code.

lazerbeam wrote:You also have to qualify GTAW under D1.1. GTAW and GMAW-S are not pre-qualified processes under the D1.1 welding code.

Good catch. That one slipped past me.

Thanks for the reply, Mongol and lazerbeam.
I can add GMAW-Globular mode for higher passes within the same wps. I don't think a new wps is needed for that. Since with gtaw, this will be pretty slow for a thickness of 1/2".