For discussion much of the time flat and horizontal are synonymous. There are technical differences so if anyone insists then you have to switch gears.

Yes flat is technically just what it indicates, but for you and me, flat is anything I can get above.

 

Horizontal = Plate laying vertical, weld bead extending right to left or left to right.
Vertical = Plate laying vertical, weld bead extending up to down or down to up
Flat = Plate laying horizontally directing below the welder
Overhead = Plate laying horizontal directly above welder
With pipe it is basically similar, but welds are usually much more difficult as in real life scenarios you usually are limited to pipe vertical, weld horizontal...pipe horizontal, weld vertical...pipe on a 45 degree, weld on a 45 degree. In some cases you might find where you can rotate the pipe, but ive never worked anywhere you could hope this helps y'all
CHRIS

 

In NZ the horizontal that your talking about is called the horizontal-vertical
the horizontal-flat is called downhand.

Cheers Stephen

 

Your example is a horizontal weld. If you were to take that lap joint and set in down on a flat work table you still would be welding horizontal. If you tilted that lap joint up so that the plates were at 45 degrees you would then be welding down into a vee which would be a flat weld position.
Most weld faults occur doing the horizonal fillet weld. It looks so easy and seems to lull welders into relaxing. Next thing you know they have undercut or cold lap.

 

Yes lotechman, and that is exactly the situation I'm trying to avoid: Undercutting the thicker, overlapping plate in an attempt to prevent from blowing through the thinner underlying plate, and in so doing, cold lapping the underplate as the weld pool cools and droops.

The weldment surface cannot be rotated flat. It is fixed vertical. Thanks, everyone, for confirming the definition of this weldment as "horizontal."

For me, this is a critical weld, two 8" weld beads in total. I've already practiced laying down over 12 feet of bead attempts using 3 foot long coupons of the same two material thicknesses (3/16" overlapping 1/8"). It's only mild steel, but I am of mild experience.

I'm using short circuit transfer, C25 gas, .035 ER70S-6 wire, and have usually toggled settings between 200 wire feed speed at 17 volts, to 240 wfs at 17.4-6 volts. I've tried it as low as 175 wfs at 16 volts, and as high as 275 wfs at 18 volts. I've tried 220 at 18 volts too, but I keep coming back to 200 wfs at 17 volts. That's where I seem to have the most control, or at least where the sizzle is the most consistent.

I clamp my coupons vertically, 18 inches from the ground, outside, exactly where the weld has to take place. I'm running the gas at about 35 CFH. I turn it down to 30 when there is no breeze. I set up a sheet metal wind barracade, which helps a lot, but you know how the wind can get around anything.

I believe I can very quickly identify when shielding gas is compromised (the arc character, the resulting porosity etc) That much at least I can tell, and I stop and make adjustments accordingly... once running the gas at 40 cfh. Beyond 40 doesn't seem right though. Anyway, the outside has nothing to do with why I am undercutting the overlapping plate, and cold lapping the bottom plate.

I've tried straight passes with no weave (like I've watched many a good fabricator do) but the result is a bead that is not enough to fill the essentially upside down fillet. So I end up weaving, and my tendency is to let the torch linger on the upper side, to heat more of the thicker overlapping plate.

However, what I am starting to realize is that the brief visits to the bottom plate are not enough to heat that plate up for fusion. Yet if I stay too long in the puddle, here comes the blob. The BLOB The BLOB...

That's who wrote that 1950's movie... a frustrated, untalented, weldor. My ancestor, no doubt.

Any advice ya'll can give me would be greatly appreciated.

I'm going to set up another 12 feet of practice coupons, but there is no point in continuing to practice what I've been doing so far, otherwise I'll be just reinforcing failure. I need to change something... my whip, my stick out (between 3/8" and 1/2"), my travel speed... maybe, a distant maybe, the settings on the machine, but really more my technique than anything else.

What can you guys advise?

 

If I read you right your lower front plate is 3/16 thick while your upper rear plate is 1/8th With both in the vertical position. I hope you understand that a fillet weld of 1/8th is more than adequate for strength so all you have to do is run one in the corner in a single pass. I'd be running C 20 and .045 but of course I have access to machines that will run in spray. I am guessing that you don't have a bigger machine? With that C25 gas I would try for a higher voltage with globular transfer. 19 to 22 volts and for feed rate I am guessing over 225. Set your gun leading and pointing right in the corner and get moving quite rapidly. You don't need a very large weld. The higher voltage should flatten out your weld. You have a nice 3/16 ledge so I would keep my puddle on that ledge and just angle/tip the gun to push the weld arc up against the 1/8th. As long as your bead sits on the edge of the 3/16 plate all you need is 1/8 bead to lean against the other plate making a 1/8th by 1/8th fillet.
Also you could cheat and use a guide bar so that you could ride the edge of the gun nozzle on it as you travel along. I have used giude Bars when I have had to weld thing material in spray mode and travelling around sixty inches per minute.

 

No, unfortunately, the plate arrangement is just the opposite, and there is no shelf or ledge to hold the bead. The fillet hangs upside down.

The thicker 3/16" plate overlaps the thinner 1/8" plate. Two (retired naval nuclear submarine) engineers who looked at this stated that the vertical leg of the fillet that adheres the 1/8" thinner plate along the loaded vector axis must be 2*T, where T is thickness of the 3/16" overlapping plate.

So I'm shooting for a weld bead that is 3/16" x 2*(3/16"), where the 3/16" leg of the fillet is the width (even with the overlapping plate), and the 3/8" leg is the vertical depth that adjoins the thinner 1/8" plate.

Also, the 3/8" leg must taper evenly, from essentially zero at the bottom (without gouging) to 3/16" at the top (without humping too high over the overlapping plate causing stress risers).

I guess a picture would be worth a thousand words here, but picture the fillet as an upside down right triangle of 30-60-90 degree angles, where the 30 degree angle is on the bottom, the 60 degree angle is towards the weldor, at the outside edge of the thicker overlapping plate, and of course the 90 degree angle is where the plates overlap, creating what you thought would be a nice shelf, but what is instead an upside down ledge to have to fill in.

Here is a text drawing of the fillet in cross-section:
__
|/
/


Here is a text drawing of the plate orientation in cross-section:

||
||
|
|

-- Where "||" is the cross-section of the 3/16" plate that overlaps "|", and where "|" is the cross-section of the 1/8" plate that continues up behind the 3/16" plate.

By the way, the 1/8 plate is actually the outside wall of 2" x 6" rectangular steel tube, so no additional weld can be added on the backside.

I thought about spray, but I only have four bottles, and they are all too full to trade out for a mix appropriate for spray. Two bottles are C25, one is straight AR, and one is trimix 90 He, 7.5, 2.5. Besides, I was under the impression that 1/8" is a little too thin for spray. On the other hand, it seems like I've seen what had to be spray on material of the same thickness, so again, I don't really know. I'd rather not have to buy another bottle just to get this 16" weld done right.

I've got the gas cup about even with the tip right now. If I recessed the tip about 1/4" back into the cup, (which will increase the stickout if I don't want to dip the cup) increase the voltage as you say, will the wire pinch out faster, giving me globular. I worry that globular will lay too much wire down (beyond MY ability to control).

Anyway, now that ya'll know more about the plate orientation and weld geometry, I could really use any and all advice on getting this done right.

 

Oh, and I don't believe I'm at all limited by the welding machine, which is rated at over 300 amps, 72 open circuit voltage.

My limitations are just not having anyone around to show me how it's done.

 

sounds like overhead.. your fighting gravity. give you more input lil later holding baby
chris

 

Ok Chuck heres what you gotta do for your overhead. When running the overhead you usually run tad colder than you do for flat. Kinda like when your going up hill. Its very important to keep a keen eye on your puddle. I usually do a circular motion. Keep your speed right. Go too fast and you wont get fusion and it will be caca. Also, try to keep your puddle as small as possible for the thickness and joint type. Your working against gravity so the molten puddle will want to fall out if you let it get too hot or too large. Other than this not much more to say except get in there and give it a try. Try not to stand directly under the weld either or youll get burned.
Good luck
CHRIS

 

I didn't realize you were doing overhead. You have no choice you have to be in short circuit transfer. Why would someone would want such a massive weld and such along leg on the 1/8th ??? My only guess is that it is to form a smooth transition becasue they are concerned about fatigue. it certainly will have no effect on strength.

 

I have another thought.... dangerous... me thinking. Normally when you do a fillet weld it is common practice to limit the size of a single pass weld to 3/8 inch. That is not to say people can make bigger single pass welds but it is not wise. Fillet welds larger than 3/8 in a single pass suffer from excessive shrinkage stress across the face. The large single pass weld is more difficult to do and the welder is more likely to be inconsistent in quality.
Why don't you try a two pass weld. My inclination would to lay one pass on the 1/8 th material so that the bottom edge of the weld bead is that 3/8th away from the corner and just barely connecting to the corner. The second pass would be another horizontal weld where you would concentrate fusing to the corner of the 3/16 material and fusing to the weld bead below.
If that doesn't work try the reverse doing the upper bead first.

 

I like Lotech's two pass suggestion also. It will allow you to keep a smaller weld, yet final weld will be sized to what you are apparently looking for. well good luck
CHRIS

 

Thanks for the ideas on the two passes, the higher voltage, the colder pass, (are the foregoing incongruent?), the faster travel speed, and the circle motion. I'll try them all on additional coupons over the next week.

If I increase the voltage, and lower the wire speed, will that be "colder"? I can "crispen" the arc with a setting on this welder, which essentially puts less energy into the weld without me changing the main settings much. It probably does this by some sort of pulsing control, I don't know.

Main thing required here is puddle control with my hand...

Keep the ideas and the techniques coming. I really appreciate all your help.