D1.2 material thickness (WPS)

Date 12-23-2014 14:30

Hi All,

It's bee awhile since I posted, but I have a question I am unsure of.

We are fabricating an aluminum weldment, 6061-T6.
Outer shell is Ø16.25" O.D., 1/4" thick rolled and welded tube.
On both ends is a flange that is .88 thick, that slips into the tube .38" deep.
Please see attached sketch.

[img]

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Our WPS is qualified to 1/2" thickness for groove welds, I'm thinking even though we are only welding a 1/4" thick joint, the WPS doesn't cover the thickness of the thicker member. However, I cannot find in D1.2 (2003) where is says anything about welding different thickness materials, which leads me to believe our WPS will not work for this application. Am I correct?

Thanks

By jwright650 (*****)

Date 12-23-2014 14:48

I don't have D1.2 handy, but looking at your sketch, it seems to me that the 1/4" thickness is governing your material thickness for the WPS. That is the point where your CJP (through thickness) is taking place. The cap plate thickness of 7/8" is irrelevant in my opinion.

By flamin

Date 12-23-2014 15:05

Sounds logical. So regardless of the material thickness, only the joint thickness is relevant?

Thanks.

By jwright650 (*****)

Date 12-23-2014 15:52

Well... in my mind, you are not actually welding a full 7/8", only the 1/4" CJP wall thickness....so the 7/8" thickness is irrelevant, it could be 2" thick, and you would still be welding 1/4" CJP.

By SCOTTN

Date 12-23-2014 16:42

Wouldn't the 7/8" thickness still be relevant with regard to preheat?

By welderbrent (*****)

Date 12-23-2014 17:43

Scott,

Is preheat a consideration for D1.2, especially only 7/8"?

By SCOTTN

Date 12-23-2014 18:12

I don't have a D1.2, so I can't answer that. I've heard that preheat can help, but I've also heard that with the right equipment, it's not necessary. I was just asking the question. I would think that preheat could increase the heat affected zone and reduce the mechanical properties of welded joints in certain aluminum alloys.

By flamin

Date 12-23-2014 18:44

Just to clarify,
Our WPS only gives a min/max preheat/interpass temp. range. So as long as we're within that range we should be good.

As far as I can tell in D1.2 (2003), it only discusses maximum heat exposure time at temperature (Table 4.5) and nothing about min preheat.

By fschweighardt (***)

Date 12-24-2014 00:53

Fwiw, that probably should be a symbol that shows backing, with wps, pqr, etc. To match

By 803056

Date 12-24-2014 03:45

A WPS qualified to 1/2 inch thick should be fine since the weld is only 1/4 inch.

The bottom is nothing more than backing. That being the case, the welding symbol could include a backing symbol. It would reinforce the idea that the weld completely penetrates the thickness of the 1/4 inch shell. Just don't include the letter "R" in the backing symbol or the purpose of the 7/8 inch thick bottom might be compromised!

Merry Christmas!

Best regards - Al