Aluminum CJP full pen weld 1

[LeonhardEuler]

Hello,

I am dealing with very week 4043 filler metal on 6061-t6 aluminum. The filler metal is not strong enough for the required loads unless I go full pen flange welds. I know that aluminum is susceptible to distortion when welded and I am worried that a CJP weld can cause excess distortion during the welding process. How big of a problem is this and can it still be specified?

We are looking at a handful of locations in an aluminum frame, not a whole building, or something of that nature.

Thanks for the advice

 

[racookpe1978]

Sketch (accurately!!) the shape of the joint(s).
There may be, or may not be, several work-arounds and alternates.

Otherwise, the answer can be stated absolutely: A confirmed, positive, definitive "Maybe."

 

[david339933]

5356 might be a better filler metal option.

 

[LeonhardEuler]

Fabricator wants to use 4043. The situation is I-beams framing into I-beams with T&B groove flange welds and web fillet welds

 

[Ron]

In 6061-T6, the weld strength will likely control. If you were using 6063-T6, the weld metal and the parent metal would be similar with 4043 wire, and the parent metal would likely be weaker if using 5356...because of the reduction in tensile strength within 1 inch of the weld with either alloy.

The weld strength will be a bit higher with 5356, but 4043 is more ductile, so if you are concerned about cracking, 4043 is probably your better option.

Not sure whether you are using GTAW process or GMAW process, but 4043 will give a smoother appearing weld. If you are anodizing after welding, the 4043 coloring might be more evident after anodizing than 5356.

 

[LeonhardEuler]

RonI'm not seeing that the parent metal will control the shear yield strength of 4043 is only 11.5 kip. Does anyone have any input if aluminum I-beam framing into Aluminum I-beam can be CJP welded. Thanks

 

[LeonhardEuler]

The I-beams have about 0.3in flange thickness

 

[racookpe1978]

No. You're misunderstannding something: A CJP DESCRIBES the preparation of the weld joint, IMPLYING (by the shape of the preparation) the final shape of the two pieces of base metal and the filler metal.

CJP = Complete Joint Preparation. CJP does NOT define the base metal material, the weld filler, its preheat or post-weld heat treatment requirements, the energy (current) or deposition rate, nor any other joint criteria.

"Normally" the weld filler material is (deliberately) chosen to be stronger than the base metal. When that happens - when the weld material is stronger than the base metal, the base metal will fail before the heat-stress zone around the weld and the weld itself will fail. The weld joint shape and size and design is then sized (length of weld, height of fillets, type of prep (J prep, double-V, single V, open root gap, simple fillet (square fit), etc.

In your case, you (your company, your predessors, the original design team, whoever) have decided to use a WEAKER filler metal than the base metal. The usual (typical) joint design "strategy" is WRONG in this specific case because your weld fillermetal is weaker than the base metal. In this particular case, the weld metal in a typical CJP joint will ALWAYS fail before the base metal will fail.

Two choices: Change the weld filler metal => "They" have told you "they" don't want to do that.

Change the joint preparation or length the weld (can't do it => You have fixed geometry of the two coped structural shapes => they can't get longer. )

Therefore, you need to increase the area of the weld across the joint. Grind the simplest CJP preparation possible. This is a double-sided V prep, with a thin center piece left to allow fitup. Tack weld the joint up. Then weld out all of the joint to the thickness of the base metal (0.3 inch, from your comment above). Then add TWO MORE fillet welds outside of the CJP once that that weld is filled out on both sides of the base metal. The fillet weld leg height should be 5/15 inch (0.3 inch), and should not be excessively convex nor concave.

Your CJP rebuilds the original beam web and flange to their original thicknesses. The added fillet welds outside of the CJP weld doubles the strength of the joint because they increase the cross-section of the weaker metal in the joint..

True. "Normally" the two added fillet welds do NOT do anything but waste time, material and welder effort. But this is not the "normal" situation.