Stick welder: Why DC?

[k0ua]

HF stocks it

but have you ever had any luck with their rod..?? I have has some adverse luck with some of it. Not very smooth.

James K0UA

 

[rankrank1]

....Last question: If DC is better why does my welder weld in AC too?

Well the answer to that is simple.

What is your Miller Thunderbolt? In simple terms and at root level it is a voltage and amp transformer. It takes your 230 volt and 40 amp household input power from your power company and converts it roughly 80 volts Open Circuit Voltage and then roughly down to 35 volts when actual welding is occuring and 225 amps AC output at your wide open setting. (Why: stick welding is a constant current process that needs low voltage and a constant high amp setting to work properly. If welding worked well at high voltage and low amps well then you could simply use a lamp cord and utilize your household power if you could figure out how to keep from electrocuting yourself or tripping a breaker. The reason OCV is limited to 80 volt by the UL is that it is considered reasonably safe from electrocution. For the most part any welder produced after 1960 is going to be reasonably safe from electrocution whether AC or DC, but you still do want to be careful. The 80 volt OCV helps the intial arc strike but then falls to roughly 30-35 volts when welding is happening).

So the absolute cheapest way to do the needed conversion for welding is to do AC (your household power is high voltage and low amp) to AC (welding is low voltage and high amp) hence why you see so many AC welders because it was the absolute cheapest way to get what was needed for welding. Of course then many people decided they want DC output just like the just like the professional grade engine driven generator welders produced as DC does have advantages. So again the absolute cheapest way to get that on a buzzbox transformer is to rectify that AC weld output to attain DC. Electrical physics dictate that there is loss in each conversion process even on the intial conversion of AC to AC which is why you have less DC output than you do AC output since your are dealing with the 3rd elctrical conversion and not the 2nd electrical conversion.

Sure there are welders that have absolutely equal AC and DC outputs but they are typically very expensive and way out of the price range of the home hobbyist plus besides cost they frequently have immense input power requirements or even 3-phase input power requirements which a standard household does not have 3-phase power.

The welding rod itself could care less whether it gets its needed power from AC or DC as either can work equally well to provide the necessary proper weld. For most people it is simply 17% easier to control all the personal human factors when using DC over AC. If you and I play basketball and shoot at 2 hoops side by side and one rim is 17% bigger then which rim will you aim at when you release the ball?

Lastly, TSC stocks 7014 (7014 burns really sweet on AC. It is the one rod that burns about equal on either one. Other rod types burn noticeabley smoother od DC and with less spatter)

 

[flusher]

I am guessing you never actually saw the puddle and learned how to move. It is like a light goes on when you finally figure out the puddle, settle down, and start seeing what the heck you are doing.. 7014, you can stick right in the puddle and drag it.

James K0UA

You have to concentrate on seeing the puddle clearly as possible (considering the presence of more or less flux in the vicinity of the puddle) and ignore the bright arc. It takes some experience to reach this point, but it's crucial to getting strong welds. That and learning to watch the edges of the puddle and adjusting your gap and rod motion to get good tie-in between the base metal and the weld material.

The Wall Mountain welding videos, especially the two on stick welding, are a good place to start if you don't have an experienced welder to guide you along. The instructor on these videos gives excellent information and demonstrations on puddle control.

Instructional Welding Videos

 

[IslandTractor]

but have you ever had any luck with their rod..?? I have has some adverse luck with some of it. Not very smooth.

James K0UA

Works OK. I certainly cannot blame the rod for welds that look like bird poop when that does happen. I take full credit for that.

 

[terraformer]

I got a chance to practice with my DC settings. Have some 7014 coming but it isn't here. I used 1/8" 6013.

I had some 3/32" mild steel and some one inch square. My Miller Thunderbolt wanted to be at full throttle 150 AMP to make a decent weld on the one inch and would do the thin material ok at about 110 but 150 looked as good.

As per suggestion I ordered 3/32" 7014, imagine that the amps can be tuned back down. At any rate the welds look to be better than I have done with the stick welder on AC.

When I first tried it I know I didn't have the welder all the way up.

Thanks to those who offered help.

 

[k0ua]

The 7014 will make a pretty flat bead without a lot of ripple.. you will have to get used to moving at the right speed with it. It lays down fast, watch your arc length, not much at all, or even drag the rod. When you get good with that get some 7018.. it is cantankerous to restrike, but sure makes good strong welds.

James K0UA

 

[terraformer]

I got some 3/32" 7014 and made my first weld with it. Stuck on some 1/4 steel rod onto .042" thick tubing using about 75 amps of DC. Worked very well. Smooth weld with some distortion on the back of the tubing but no burn through. It was easy.
Thanks much.

 

[rcowan]

Practice more with DC

RC

 

[undercut]

Looks like you are making good progress. Practice more and watch pros weld so that you can see what the puddle should look like and get hints on positioning and material prep. I love the following link:

Down and Dirty Welding Tips | welding-tv.com

 

[terraformer]

Over the holiday I got a chance to work on my DC technique. We had salvaged a bunch of wrought iron railing from a house that was being torn down. I rebuilt the railing and used it to put around my salvaged 12x20 foot deck. There was a fair amount of cutting and rewelding required.

I had a pound of 7014 and a box of 6013 rod. I think I was at about 90 amps. I liked the welds better when I had the polarity reversed.

 

[IslandTractor]

Over the holiday I got a chance to work on my DC technique. We had salvaged a bunch of wrought iron railing from a house that was being torn down. I rebuilt the railing and used it to put around my salvaged 12x20 foot deck. There was a fair amount of cutting and rewelding required.

I had a pound of 7014 and a box of 6013 rod. I think I was at about 90 amps. I liked the welds better when I had the polarity reversed.

Reverse polarity (DCEN) produces a higher electrode melting rate which makes for prettier welds but less penetration. It can be useful especially if welding on thinner metal to control burn through too. The downside, and reason that straight (DCSP) polarity is generally preferred is because of the lower penetration issue. I would imagine reverse polarity is rarely if ever used for a pipe root or filler weld but maybe could be used for the final cover pass. Maybe one of the pro welders will chime in to clarify.

 

[terraformer]

Most of the metal was .09-.12" thick.
Maybe I had the amperage turned up a bit too much and by turning it around it balanced things out.
Thanks for the tip.

 

[R W]

Reverse polarity (DCEN) produces a higher electrode melting rate which makes for prettier welds but less penetration. It can be useful especially if welding on thinner metal to control burn through too. The downside, and reason that straight (DCSP) polarity is generally preferred is because of the lower penetration issue. I would imagine reverse polarity is rarely if ever used for a pipe root or filler weld but maybe could be used for the final cover pass. Maybe one of the pro welders will chime in to clarify.

DCEP (electrode positive)= Reverse Polarity.
DCEN (electrode negative)= Straight Polarity.

 

[IslandTractor]

DCEP (electrode positive)= Reverse Polarity.
DCEN (electrode negative)= Straight Polarity.

I screwed up the abbreviations in my post. DCEP=DCRP=straight polarity and DCEN=DCSP=reverse polarity as RW states. DCEN when the electrode (stick) is negative and the work is positive is when you get higher electrode melting and therefore higher fill deposition rates. DCEP or reverse polarity with positive electrode and negative work is what gives better penetration and is usually considered to have the best weld characteristics.

 

[mikehaugen]

I screwed up the abbreviations in my post. DCEP=DCRP=straight polarity and DCEN=DCSP=reverse polarity as RW states. DCEN when the electrode (stick) is negative and the work is positive is when you get higher electrode melting and therefore higher fill deposition rates. DCEP or reverse polarity with positive electrode and negative work is what gives better penetration and is usually considered to have the best weld characteristics.

you are still reversed, you are going to confuse people (your first line anyway)

 

[IslandTractor]

you are still reversed, you are going to confuse people (your first line anyway)

I should just quit! You are correct, I edited the post at the last minute to include reverse and straight but mixed them up again. Mea culpa x2.

 

[Shield Arc]

I should just quit! You are correct, I edited the post at the last minute to include reverse and straight but mixed them up again. Mea culpa x2.

That's OK! I use to have a neighbor who was a school teacher who taught welding in a Jr high school live across the road from me. When I moved here he came over and introduced him self. In time we got on the subject of welding, he told me he was a teacher, I told him I use to be a weldor. I'll bet he must have came over 15-times to ask me which way you plug the leads in for what polarity he wanted to weld with.:laughing:

 

[k0ua]

I always though the whole "reverse" and "straight" was EXTREMELY stupid. as they tell you nothing. They assume you already know what straight and reverse are.
Now DCEP =DC Electrode Positive or DCEN=DC Electrode Negative are self explanatory. They tell a complete novice which way to hook up the leads. If it is electrode positive, then hook the lead that will hold the electrode to the jack marked + if it is electrode negative then hook the lead that will hold the electrode to the jack marked -.

No one needs to know any more than that. Reverse and Straight are just stupid.. rant off.. thank you..have a nice day
James K0UA

 

[mikehaugen]

my welder actually has a selector switch the says "reverse polarity- electrode positive" or "straight polarity- electrode negative". No thinking or switching leads required.