How Do I Deepen Weld Fusion?

[Franko]

Once the problem with the MIG was solved, I started tests on the welds I need to make.

I beveled the pieces and spaced them about a 10th inch apart. I ran the MIG at the recommended settings for 1/4" steel. There is one 3/8" piece and one 1/4" piece. I welded with .30 wire and used a oval weave push pass with about 1/2" of stick out. The weld looks very good to me.

But, when I cut and polished a section and put some nitric acid on it, it is obvious that I got good fusion on the top half of the weld, but no fusion on the bottom half.

What can I do to increase the penetration and fusion?
Widen the gap?
Grind the bevel at a wider angle?
Increase the amperage to recommended 3/8" settings?
Maybe do a non-weaving drag pass and then a weaving pass over it?

 

[FOMOGO]

You might be better off doing multiple passes, and use smaller circular motion to keep the puddle temperature up. I try not to have any gap at the bottom of the V, and leave just under 1/8th" of material at the bottom of the V on heavier material butted together, and run as hot as can with out blowing through. Mike

 

[Karl_T]

This is the classic problem with MIG on thick material.

The welder makes a difference. I've got the beautiful blue box - Miller 252. For 1/2" steel, I Vee down 1/4" use flux core and CO2 voltage to the high side of spec, wire speed to the slow side. Then move along slow with a wide weld bead. It will fuse all the way to the bottom.

I used to have a Century. Had to pull the stick out for anything over 1/8". A pass with stick welder using 6011, then a second with the MIG makes for a purdy and strong weld.

Karl

 

[Alittlerusty]

Mig is notorious for making pretty but shallow beads multiple passes more heat is the ticket.

 

[Franko]

Thanks for the suggestions, Fomoco, Karl, Alittlerusty.

I think I'm stuck with the 10th inch gap, as I already cut the material for that.

So, I leave the bevel about like it is (it leaves about a 10th at the bottom of the 1/4" piece.
Make a straight pass at about one more click on amps and the same wire feed, trying to keep the cup close and the weld at the bottom of the bevel.
Then make another pass with a weave to finish off the top.

Should I grind a little off the top of the hump of the first pass before making the second?

I could be wrong, but I've found that I get better fusion further in the corner of a T-joint if I drag pass. (the bottom of the bevel is much like a T-joint) It seems that the shape of the puddle is more pointed on drag passes and flatter on the leading edge of push passes. Does that hold water?

 

[chuck]

Franko,
030 wire is not recommended on metal thickness greater than .105. Your hobart manual may say it will,,,,I have tons of literature that says it won't.
`.035 can weld up to .250 thick material .
Can you get .035 70s3 wire, a liner rated for that size of wire and .035 drive rolls? My hobarts all came set up this way but I bought them from welder supply houses.

The stick out from the contact tip to the weld puddle should be about 1/8 inch using .035 wire.
The voltage, use a voltmeter, should be about 22 volts, running.
The wire speed will need to be about 370 inches a minute using .035 wire. Measure the wire coming out for 6 seconds, multiply that number by ten to get your wire speed. We have amp meters on professional welders and set the welder at 200 amps for 1/4 steel.

The contact tip needs to protrude from the nozzle at least 1/8 inch, you will probably have to cut about 3/8ths of an inch from the end of your nozzle. 70s6 wire is not a multipass wire,

YES, it says it can multipass, that means 2 passes only, it is only to be used as a multipass in some situations using low carbon steel where each pass contacts primarily base metal such as a fillet weld. Lincoln electric , the James Lincoln foundation has several good books, for very little monetary value, that explains this very well.

Consumer welders are very optimistic in their sales literature,,,,,,,,,,,.030 wire vaporizes at 22 volts and 200 amps, it will not be able to heat the metal enough to get good dilution with the base metal. This is called lack of fusion, not lack of penetration..you will get dilution with the wire you are using, the problem is not enough dilution and the metal cools to quickly, which means the granular structure has not had time to properly grow, the grain size will be very fine, and the grain boundary will show up as a line under higher magnification,,,,the carbon dioxide, monoxide cycle is shortened which leads to porosity.

Penetration is joint design, 100 percent penetration means there is an open root weld prepared or one is grinding the back out and welding from both sides.

How many passes? One root, two fills, no cover,
I would not use that joint design, Use an outside corner joint, just as strong and no preperation as in grinding bevels, .....inside corners just about touching is the only prep needed.
Your bevels are to large, try to keep that included angle between 45 and 60 degrees.
When stick welding we use large bevels, to get the 6010 in tight. Not necessary with mig.

The root at a tenth of an inch is good, I set them at an eigtht on quarter steel.

All bare wire mig is push. If perpendicular is 90 degrees, the perfect push angle is 5 degrees from perpendicular to the weld joint. The root fill and cover passes are all done with push passes. Dragging bare wire mig causes lack of dilution with the base metal, porosity and smut in the weld, again, the welding books from the James lincoln foundation explain all of this fully.

Well, I don't mean to sound harsh, ,,,I've been doing this for 40 years, know to much I guess
Chuck

 

[Franko]

Not harsh, Chuck. I need to hear that. I'm trying to learn.

My contact tip is about a tenth of an inch inside the cup. I'll move that out as you recommend. I may be able to push the cup on a little further.

By "outside corner joint" do you mean just butt the two pieces with a gap?

I was looking at the puddle when I was pushing the weld and noticed that the puddle was pointed, so I was wrong about that.

I was looking at the Lincoln web site regarding penetration and found a section that advised that smaller diameter wire penetrates more. I first saw the notion on a welding forum site and they all said it was wrong, but there it was, right in the Lincoln site.

From Lincoln: Things that effect penetration

• Electrode Diameter: when welding with two different diameters of the same electrode and at the same current level, generally more penetration is achieved with the smaller diameter electrode than with the larger diameter electrode (see Figure 5). If you look at an end slice of each size wire, the smaller diameter has less cross sectional area than the larger diameter. As the same amount of current flows through each electrode, the concentration or density of current is greater in the smaller diameter electrode than in the larger diameter electrode. As a result of this higher current density, the smaller diameter electrode will have greater weld penetration than the larger diameter electrode. Note however that every electrode diameter has a maximum current density before the welding arc becomes very unstable and erratic. So as current reaches a certain level, it will become necessary to increase the electrode diameter.

I did a second test weld and it looks to be ok. The Hobart Handler 190 MIG welder was set at 70 amps and wire feed was at 6. I drug the first pass as close as as I could, dragging the cup on the bevel. The bead did not quite come up to the level of the top of the bevel. The acid test shows a couple of small gaps at the edges of the second pass. I probably circled the weave a bit too wide. All other parameters, such as bevel and gap were the same as the first test.

I think I picked up some contamination from the edge of the bevel where it wasn't ground.

 

[T Bredehoft]

On behalf of Franko and the rest of us non-welders, many, many thanks for the instruction and the information behind it. I've never tried to weld more than .090 material with MIG, made a lot of bubble gum before I got it to flow at all. I'll need a bigger welder to weld anything bigger, so I don't plan on it, but if the need arises, I've got more background than I ever had before.

 

[Franko]

My sentiments exactly, Tom. This place is rich with knowledge and kind people who are generous with it.

 

[Franko]

This is the classic problem with MIG on thick material.

The welder makes a difference. I've got the beautiful blue box - Miller 252. For 1/2" steel, I Vee down 1/4" use flux core and CO2 voltage to the high side of spec, wire speed to the slow side. Then move along slow with a wide weld bead. It will fuse all the way to the bottom.

I used to have a Century. Had to pull the stick out for anything over 1/8". A pass with stick welder using 6011, then a second with the MIG makes for a purdy and strong weld.

Karl

My TIG will do stick, but I haven't tried it since I was in college. That's all I was able to do — Stick it. I got some e6011 1/8" rod to practice with but haven't gotten around to it yet. I can TIG without sticking it, so I think I'll have a little better success with it now.

One thing I like about MIG is that you can use two hands to steady it. Same with stick, I imagine.

I can TIG weld ok, but I never even came close to success gas welding.