Welding advice, please

[Perplexed]

Recently, I bought a Hot Max 135 amp MIG welder kit, and it came with a spool of 0.030 flux core wire, so I decided to start practicing with that wire. I got two pieces of 3/16" mild steel - one was a sheet about a foot square, the other was a rectangular piece about four inches wide and eight inches long. I wire-brushed the two pieces until they were relatively clean, then I used a 90-degree clamp to set the smaller piece perpendicular to the bigger piece. I set the welder's amperage and feed rates according to the diagram on the lid, and started welding. After several attempts where I consulted a welding guide (too much stick out, and too fast a feed, at first), knocking the smaller piece off and cleaning it up before setting it back in place, I am now at a point where I can produce somewhat smooth welds with a convex surface. However, I noticed there's not much penetration being made into the two pieces of steel; according to the guide, the amperage setting on the welder is too low. I bumped it up one notch (from "C" to "D" on a range from "A" to "J"), but still got minimal penetration into the steel. The welder is rated for up to 5/16 steel; I was wondering if I should keep bumping the amperage knob until I get satisfactory penetration? Right now, there's at most about 1 mm of penetration in some parts of the weld, while in other parts there's just surface discoloration. No discoloration at all on the other side of each piece of metal. Parts of the weld also seem to be sitting on the surface of the metal pieces. What can happen if I go too high with the amperage - will the welder shut down, or will there be burn-through in the steel or something worse? Any suggestions or advice would be welcome!

 

[Transit]

I think you need more amps. What you call the amperage setting is really the heat control. Amps are controlled by wire speed. You may be moving the gun too fast along the seam, too much stick out. The worst that could happen is you burn through the stock. You may also want to try 0.035 wire that will carry more current without such a high wire speed. There are lots of online sites to go to.

For 100 amps with 0.030 wire you need 250 inches/min or 25 inches in 10 seconds.
With 0.035 wire for the same 100 amps you need 200 inches/min or 20 inches in 10 seconds.

Of course the ground clamp is on a clean spot and close to the weld line?

 

[Perplexed]

Transit, the owner's manual describes the one knob as the "output voltage control" that "adjusts to any setting from 25 to 135 amps." The speed control knob "controls the wire feed speed" but the manual does not say anything anywhere about the WFS controlling the amperage - it seems the first knob does that. At the initial setting, I had the wire kicking back at the gun, so I figured my feed speed was too fast, and I dialed back on the WFS. That cured the kickback, but the penetration was still minimal. I tried upping the output voltage control two settings, and that seemed to help a bit with penetration, but I was concerned about going too high with that setting. Visions of a fire were dancing through my head, while I ran around screaming and retrieving the fire extinguisher

Oh, and the ground was on clean metal no more than 8-10" from the weld, and sometimes as close as 3-4".

About how much of each piece of metal should be penetrated at the weld? 10%, 25%, 50%? My last attempt was to weld the smaller piece on both sides while it was perpendicular to the larger piece, and it took several good solid whacks with a hammer to break the smaller piece loose. Should the weld be so strong it takes a grinder to break the weld?

 

[Shield Arc]

A good way to check penetration of a weld. Make a fillet weld on two plates, then beat on the upper plate, and force it over the weld.

 

[Perplexed]

A good way to check penetration of a weld. Make a fillet weld on two plates, then beat on the upper plate, and force it over the weld.

That's how I was checking for penetration - in fact, your diagram is exactly how I was welding the two pieces of steel. Hammering on the vertical piece usually didn't do anything (no gradual bending over) until the piece broke loose. The welds weren't quite that neat, though

 

[Shield Arc]

Here's the only picture I could find of penetration. I made this weld with Tig.
Remember joint prep plays a big part in the amount of penetration you'll get.

 

[Transit]

I think you need to read the basics of how mig works. Mig is a constant voltage process which is set by the heat control [voltage], amps are related to the wire speed. The process that your unit uses is called Short Circuit. First the wire comes into contact with the work and a large current flows in the wire heating it to the melting point, the part that sticks out from the tip. Next that wire deposits a small drop on the work and be cause a gap forms between the droplet and wire in the gun a arc is formed that heats the droplet and work to form a puddle. Next the wire over takes the cooling puddle and everything starts over again. Once the heat is selected, there is a range of wire speed to match that condition that will not burn back the wire to fuse with the tip or push back the gun. The faster the on-off cycling the more amps, the deeper the penetration.

Just another thought, is this a mig or a wire feed welder? A mig will have a large capacitor in the gun circuit about the size of s beer can. If not you have stick welder that happens to use flux core wire in place of a welding rod and what you say about the step current control would be correct.

Hot Max 135WFG 135 Amp Gas Ready MIG Welder, Gas Welders, Welding Supplies

 

[Perplexed]

Transit, I'm a bit confused with your last response. The welder I have is exactly what's featured at the link you provided; it's a MIG welder using flux core wire fed through the gun, so no shielding gas is needed. It can use CO2 though with regular wire, if I want. The setup I'm using now is the flux core and no gas.

But I wondered if vigorous wire brushing of the metal surfaces to be welded was enough; so I borrowed my neighbor's angle grinder to clean the surface of the larger piece of steel. I also cut off a bit of the smaller piece to provide a freshly cut surface for the weld. Then I clamped the pieces together as before, fired up the welder, and went to work.

This time - with only about 1/3 of the seam welded on both sides - I can't budge the vertical piece, even with healthy whacks with a hammer. Looks like surface prep is indeed the key, and an angle grinder is on my shopping list this weekend

 

[lostcause]

i've had an older century 120v wire feed welder and my experience is that when you get into the upper 1/2 of its capability range you're going to have to run up close to the high end in the heat setting. i'd try setting f or higher, and then tune your wire speed until it isn't "popping" (too slow) or trying to push the gun away from the metal (too fast). i'm sure your welder is more advanced that mine, seeing that it's 15 years newer and about 25a higher in the rating, but i found that trying to handle 1/4" and thicker i had to run at the max heat setting.

another thing to try is leaving a gap. what i will often do is use a couple left over stubs from stick welding to position the pieces with an 1/8" gap between them. it will give you a chance to learn a good technique for weaving the bead to fill the gap. it also will allow you more penetration for the same heat setting.

 

[Scooby074]

Your machine is at its limits. Dont care what the manual says. China welders and their ratings are wishfull at best.

Proper beveling is essential, especially when your near the limits of your machine. Sure you could blow through that weld with a 300 amper without beveling, but you dont have that.

What transit said about Mig process is correct. Id suggest reading up on the process and which "knob" adjusts "what". Its essential to get the correct weld profile.