4F Bead Sequence

Date 06-17-2010 15:12

That's what I've told the guys when we've had to do topside welds. The other thing is to tell them to be very mindful of the rod angle, work and lead angle. Don't know how many times I've told guys to grind it down and re-cap before they call it good. The other thing that I've been trying to get people to understand is that when you call a weld good, don't turn right around and say, well I could use a little touch up here and there. Especially in front of the inspector that you just told it was good.

By 357max

Date 06-17-2010 17:21

Lincoln's "New Lessons in Arc Welding" 2nd printing March 1982 page 1-88 show this technique. Root pass in corner and 2nd pass overhead plate and 3rd pass on vertical plate. I would presume that subsequent layers with increasing number of passes would follow suit to the illustration. Hobart's curriculum w/dvds shows the opposite. 3rd pass on overhead and 2nd pass on vertical plate.
This should produce an interesting discussion; especially beyond "...we always do it that way". Why? What is advantages/disadvantage one versus the other. Does electrode choice, process, polarity etc produce a preference....

By ssbn727 (*****)

Date 06-18-2010 08:32 Edited 06-18-2010 08:38

Hi Superflux,

Are we talking about a low hydrogen multiple pass multi-layer weldment completed with the use of E-7018 electrodes, or of greater tensile strength???

Because if the answer to my question is yes, then I always have taught my students as I have also been taught that the first bead to be deposited on a 4F position joint after the root pass is always to be located where the center of the next electrode pass is maintained at the location of the bottom toe of the root pass @ a 40-45 degree work angle...

The tie in bead or pass to the over head plate with the vertical one should always be deposited in this manner... Locate the center of the electrode towards the top toe of the root pass which should still be visible if the second pass was deposited consistently and as I explained previously, and the work angle of the electrode for the tie in third pass should be at the very least 70 degrees in order to result in having equal legs on the cross sectional view of the fillet weld deposits as a whole.

The key to this method is the fact that when the lower pass is deposited first, it acts as a shelf for the tie in bead to the over head plate and all that needs to be remembered is the importance of changing the electrode angle once the tie in bead is to be deposited as well as using the proper work & travel angles and current which would enable the proper travel speed also... Finally, never use a push travel angle while depositing beads in the 4F position unless it is absolutely unavoidable - PERIOD!!!

So as one progresses to eventually reaches the point where all they need to do is to lay in the tie in bead/pass, the electrode work angle will always increase after the bottom or first pass is deposited for each layer and culminate with a much higher electrode work angle for the tie-in/top bead pass which completes each layer. ;)

This has always worked quite well for me and many others as I personally have deposited many, many pounds of low hydrogen electrodes (E-7018, 8018, 9018, 11018, 12018) in the exact type of positions while welding many different types of structures during my 35+ years as a welder and the same progression can be repeated over and over again if required to weld thicker sections also.

Respectfully,
Henry

By Flash Date 06-18-2010 23:00

Hi Guys
regardless of process and position
the general approach is start at the bottom and work up
why? so you have a solid shelf for the liquid metal to sit on (like when you are welding in a groove)
it always works for me
R
Flash

By Superflux (****)

Date 06-19-2010 02:30 Edited 06-19-2010 04:01

Hi Henry,

I was taught to use both sequences regardless of whether it be SMAW (any flux chemistry) or any of the semi-automatic wirefeed processes. A skilled welder in the 4F position is capable of either method. The problem is, that many operators seem to have difficulty grasping the concept of 4F or 4G simply being an inverted 2F/1G weld. Following this train of thought on fillet welds, the final bead is deposited on the vertical member.

Now to address the "shelf" concept I mentioned in my original post. Improper (excessive) lead angle of the electrode results in undesireable convexity or as we say in the Structural Steel Shops, "Ropeyness". This creates an undesireable cross section profile at the lower toe of the bead and nearly impossible to correct regardless of future bead placement. Too low of amperage will also result in excess convexity.
It really should not matter which direction the sequence is followed if the beads have the proper contour. Bead planning and placement are always being fine tuned, and the skilled welder will always be making adjustments before and during the welding.

Due to "fear of falling" ie. molten metal and slag finding their way into undesireable locations on the body (as if there is a desireable place to get burnt!), many welders lower the amps when welding overhead. I've got scars on every imaginable piece of my epidermis. Yes, even "little john" has a scar! Try explaining THAT fresh burn mark to the wife when you just came home from a 6 week shutdown 2 states away!!!. When it comes to out of position welding, Pain is a most efficient teacher.
I typically (with SMAW Exx1x electrodes) do not adjust amperage from one positon to the other. There are exceptions of course.
In closing, it has been my experience that most students, beginners tend to make their leg lengths more equal and weld faces flatter when they switch to the top to bottom sequence. I posted this to help those who are having difficulty and present an alternative approach that may or may not improve their weld appearance. Many whom I've shown or suggested this to have replied.."I'd never of thought to do it that way".

Flash,
When I went to trade school, my instructor never really mentioned to us the sequence of multiple pass 4F. We all just seemed to automatically start at the bottom and progressed up. The following day during lecture, the Lincoln "New Lessons in Arc Welding" book came out and we were given the option as to which way we chose. Our grade would be the descision maker.