FCAW- Essential Variable as per AWS D1.1

By Lawrence (*****)

Date 07-01-2016 11:57 Edited 07-01-2016 12:05

Welcome to the forum Athul

Interesting question.

AWS A5.36 2012 Specification for Carbon and Low-Alloy Steel Flux Cored Electrodes and Metal Cored Electrodes places E71T-1C and E71T-1M as separate classifications (Table 1)

E71T-1C and E71T-1M share similar Weld Deposit Requirements in Table 1 of A5.36... But only when an M21 shield gas combination of mixed gasses is used. Your WPS does not fit there by virtue of your 3 part shield gas.

Your 3 part gas selection would make your gas designator per A.36 table 5 to be M24 or possibly M25

What I don't understand really is:

1.   Why did you qualify a procedure using an E71T-1C (an electrode designed for use with 100% Co2) with mixed gas in the first place?

2. What benefit are you getting from a 3 part shield gas in your project?

Now-a-days good impacts and spatter free welds in all positions can be achieved by E71T1-C using 100% Carbon dioxide or a simple 2 part gas of 15-25% Co2, Argon balance, and an E71T-1M electrode (M21)

So back to your question. D1.1 2015 Table 4.5 Essential variables requiring WPS Requalification lists 3) Change from one electrode or flux-electrode classification to any other electrode or flux-electrode classification to be reason to trigger a new WPS to be qualified.

One last question.... Is there any reason you can't simply generate a prequalified WPS with the electrodes and shield gas that makes the most sense?   What drove your need for a PQR in the first place??

By 803056

Date 07-01-2016 12:03

I agree with Lawrence, why not write a prequalified WPS?

Al

By athulpcucek (*)

Date 07-01-2016 16:04

Mr. Lawrence, thank you for your response .

I'll answer your doubts
1. There was a replacement of shielding gas used in my company, many years back(long before when I joined). Maybe at that time they had only E71 T1-C electrode in stock and they retested it with the mixed gas , since gas composition is an essential variable. Tests were satisfactory & WPS was established.I guess, even some clients also accepted it , at that time. Later somebody questioned using C electrode with mixed gas.Then all the WPSs were changed with M electrode. One 6G WPS was not changed, since there was not tubular jobs at that time. Now we got some orders of tubular joints & only available WPS is the above mentioned one with C electrode , mixed gas & the electrode presently in stock is M type. While reviewing this old WPS, this doubt came into mind & I raised the question in this forum. Anyway my doubt is cleared.

2. I dont know exactly the benefits of this composition(it was established long before I joined). But from literatures I've read, Ar will give a smooth arc , Co2 will enhance productivity & O2 will give visually appealing welds. When using 100 % CO2, productivity will be high, but spatter problem arises & weld profile also looks a little odd. Mixture of Ar & Co2 is fine, but a little bit O2 gives good looking welds.

While talking about prequalification, yes it it is possible to write a prequalified WPS. But most of our client specifications, stresses on the WPS produced by testing as per clause 4.

I hope I've made myself clear. Expecting support in future also.

Thank you.

By Dreizehn (*)

Date 07-01-2016 16:17

a pretty weld isn't always good, and a good weld isn't always pretty.

By welderbrent (*****)

Date 07-01-2016 16:19

AAHH, but a pretty weld stands a better chance of being good than an ugly weld does.

Brent

By Dreizehn (*)

Date 07-01-2016 16:23

Very true, sir. An old hand told me that one day and it stuck.

By welderbrent (*****)

Date 07-01-2016 16:25

'Old' is relative, and now it has become one of my closest ones.

BB

By jwright650 (*****)

Date 07-01-2016 22:10

re: FCAW with 100% CO²

Get the voltage to amperage(WFS) dialed in and there will be no spatter problems, it will have a nice arc, it will be visually appealing, and the slag will slide right off(most of the time it falls off before you have a chance of getting a chipping hammer near it).

By Lawrence (*****)

Date 07-01-2016 23:08

Completely agree... A good E71T-1C will run in all positions with deposition rates and spatter free welds equal to Mixed Gas electrodes.... The mechanical values can be slightly different, but that may or may not be an issue, depending what is actually required for your project, you might even find it more favorable.

There is a lot of information out there that is either old, or driven by gas suppliers who prefer to sell you the more expensive mixed gasses... I hear it all the time.. Spatter, low deposition, slag removal, mechanicals, operator ease... It's pretty much all bull... It takes no extra training to transition from Mixed gas to Co2 and the quality and productivity is excellent. In my opinion the sweet spots in the parameter range for each position is wide enough to be considered easy to use.