Stick welder: Why DC?

[terraformer]

I have a Miller Thunderbolt 225. It is AC and DC. My question is, when should I consider using DC? I use my welder about once every two weeks usually fabricating or repairing things. I usually buy a 5 pound pack of Lincoln 6013 1/8" rod. I think I am on my 3rd box of the rod.

I keep the power level to about 80-90 amps. It starts pretty easy and makes welds that don't burn through too often. If I crank it down much from there it is hard starting and the weds don't penetrate well If I turn it up a lot I get a lot of undercutting and burn throughs.

When I first got it I tried it on DC and had trouble getting the welds to come out so have just stayed with AC.

Should I make some effort to use the DC settings? What would be the advantage?

 

[Gary Fowler]

DC rods are available in more types than straight AC so you can use a variety. Many rods are compatable with AC or DC but some are strictly one or the other. Perhaps your first attempt at DC welding was using AC only rods. DC currrent will give you a more stable arc than AC, better penetration at lower amps and generally just a smoother weld.
I really dont know what you were doing when you said you got better results with AC than DC as this is not the normal results.
Get the right rods, ie, 6010 and or 7018 in AC/DC or just straight DC version and practice. Depending on you metal thicknesses to work on, 1/8" 6010 and 3/32 7018 are good for general welding on materials 1/8 and thicker. The 3/32 E6010 rods are fine for really thin material, but I dont like to use them much due to hard starting, sticking etc when using low amperages and when you crank it up to burn easy they overheat and most of the metal goes off as sparks and buckshot. FOR really thin metal, you really cant beat a MIG wire feeder, but since I dont have one of those, if I cant weld it with 1/8" 6010 or 3/32 7018, I get out the Oxy/Acetylene rig.

 

[k0ua]

FOR really thin metal, you really cant beat a MIG wire feeder, but since I dont have one of those, if I cant weld it with 1/8" 6010 or 3/32 7018, I get out the Oxy/Acetylene rig.

Gary I used to do that, but I TIG little/thin stuff now. You can get set up with scratch start TIG pretty easy and low cost on your DC stick welder. It really adds to the versatility, and has a much smaller Heat Affected Zone, than gas. All I know about AC versus DC welding is after getting my DC machine I never wanted to go back to AC ever again, for all the reasons you mentioned.:thumbsup:

 

[IslandTractor]

Depending on you metal thicknesses to work on, 1/8" 6010 and 3/32 7018 are good for general welding on materials 1/8 and thicker. The 3/32 E6010 rods are fine for really thin material, but I dont like to use them much due to hard starting, sticking etc when using low amperages and when you crank it up to burn easy they overheat and most of the metal goes off as sparks and buckshot. FOR really thin metal, you really cant beat a MIG wire feeder, but since I dont have one of those, if I cant weld it with 1/8" 6010 or 3/32 7018, I get out the Oxy/Acetylene rig.

I agree with your general points but 6010 rods sometimes are tricky especially with lower power or inverter welders. 6011 or 6013 don't penetrate quite as much but are easier to use with lower power DC welders as I recall. I have a Miller Maxstar 150 and haven't used the 6010 just because I was warned away from it.

 

[terraformer]

Gary: You probably hit the nail on the head. Wrong sticks. I think I meant that the welds looked splattery and dry. Probably too low of heat or wrong rods.
Koua> So I can get a Tig attachment for my DC welder?

Thanks will try some other welding rods and move the cables over to DC. Or maybe just try the DC with the 6013 sticks.

 

[rankrank1]

Since you do have DC then yes do try it. DC makes it slightly easier to weld over AC (maybe 15% or so easier). Why: The power is always on with a DC power wave and it never crosses 0. An AC wave oscillates over 0 in a sine wave pattern at 60 hertz just like the lights in your house are actually turning on and then off at 60 hertz although you can not see it with the naked eye. (Generally any rod you have been running at say 100 amps on AC will burn at around 85 amps on DC due to the DC being more efficient hence easier arc strikes and less stuck rods).

Also with DC you can change polarities of stinger and ground clamp to tune your desired arc charecteristics further. You will use stinger + and ground - most of the time for best penetration. Think of this arrangement kinda like 67% power put into rod and 33% power put into your workpiece. Stinger - and ground + is useful though for really thin metal for less penetration if no mig available. Think of this arrangement as 33% power into rod and 67% power into workpiece.

NOTE: AC has no polarity as pointed out the polarity is actually alternating back and forth at 60 hertz. Think of this arrangement as 50% power into rod and 50% power into workpiece to better grasp it as compared to your 2 DC options.

Generally speaking any rod that will burn on AC will burn on DC even better - roughly 17% better. Also there are a few rods that are DC only burning rods. Nothing wrong with AC, DC just gives you more options from rod choices to polarity.

 

[k0ua]

.
Koua> So I can get a Tig attachment for my DC welder?

Absolutely. You will need a 17V torch (note V for Valve) about $100 or a little less on ebay. a regulator with flow rate.. about $26 on ebay. and a cylinder of pure argon. you can rent or buy there.. I bought a full 125 CuFt for $210. Flow rates are from 12 to 20 CuFt hour. so guage your anticipated weld times from that on how big a cylinder to get. Now this is Scratch start TIG, no fancy HF start, and no pedal to control current.. so you cant taper off with the pedal towards the end, you have to snap out to stop the arc. I am not saying this is wonderful or the cats meow, but it works, and you can get used to it. Millions of welds in the "old days" were done this exact way. I would reccomend if the torch does not come with any consumables. some do some don't, you set up for starters with 1/16 inch Lanthanated tungsten (blue or gold). Do not use pure tungsten (green) . The red Thoriated works well, but it is radioactive.This will do most of the range you will want to work in. (20 amps to 120) amps. This will NOT do aluminum at all. (although some can do it with Helium) But this will do mild steel and stainless. with the proper fill rod of course. This is a lot like gas welding only with a small "flame" instead of a big one.
If you are serious about it I will hunt you up some links to buy the stuff you will need. It took me a while to figure it out. It all seems so simple now, but I didn't have anyone to help me, You do

James K0UA

 

[rankrank1]

Koua> So I can get a Tig attachment for my DC welder?

Yep. It will be an old school set-up in that it will be scratch start and will NOT have foot peddle control but it is useable.
Matter of fact I just ran mine some for the first time this weekend on my Miller Thunderbolt and it was pretty neat. I plan to use it to do some improvised tig cutting too.

a) #17 air cooled torch with manual gas valve at handle (I paid $50 brand new off ebay including shipping - lucked into this one)
b) power lug adapter $11.45 at LWS
c) one 3/32" collect $1.15 at LWS
d) one nozzle $2 at LWS
e) three ceramic cups $3 at LWS
f) two 3/32" tungsten (red thoriated would have prefered lanthanated but they did not stock lanthanated) $8.00 at LWS
g) I used my regualtor from my mig welder so saved this expense (I burn flux core in my mig so regulator unused and available)
h) converted my unused and empty 75/25 mig bottle to 100% argon so saved this expense (again use flux core in mig so had bottle already and saved this expense).
i) 1 plastic pop bottle with end cut out to insulate the power lug adaptor as I simply clamped my stinger to it (free)

Here are a couple video that cover basics

Homemade Tig Welder - Tig Welding Old School with Scratch Start - YouTube

Scratch Start Tig Setup Explained - YouTube


Improvised cutting

http://www.youtube.com/watch?v=2OjEhGHit84

 

[rankrank1]

I originally had a Lincoln AC-225 buzzbox. I did fair with it the few times I used it. Then I got a Miller Thunderbolt 225 AC/DC stick welder, and the same thing happened with my results. I used 7014 1/8" rods most of the time. My results were so bad, I eventually gave up and sold my welder. I don't have much practice material or a need for welding, so I don't really miss it.




Although DC never crosses the 0 volt point, it goes down to 0 volts. DC welders usually have an inductor in them to help smooth the DC voltage and maintain an arc. The thumbnail is a graph of an AC waveshape and a full wave rectified DC waveshape.
View attachment 271005

Good catch on the DC wavefrom graphs. I probably should have covered that in more detail but tried to keep my novel short. Yes the voltage appraoching zero is why DC is only roughly 15% to 17% better than AC. If it stayed truly constant then the efficiency would be more than the 15% to 17% that it is.

I am surprised you had so much trouble with either of your stick welders burning 7014 rod. 7014 is really about the easist rod to use - many call it "idiot rod" since it almost welds itself on even the worst of welding power supplies. I am thinking you had a house supply voltage problem like maybe both Hot lines going to the same leg of of the house feed and thus not getting a true 230 volt input from the house, but no way to check that now. (Had a friend who suffered this phenomon recently as his cook stove quit working properly. All house wiring was correct and power at the power pole was correct, but power company had dug underground and cut one of the lines to his house. The cut line made enough contact with the adjacent line to remain hot but this meant he was only getting one phase inside the house - he did not have the second phase so none of his 230 volt stuff worked correctly).

If I ever have to start selling tools: My buzzbox stickwelder will be the last welder that I would sell as nothing gives me as much bang for my buck as it does- it will do so much more than weld alone and is very cheap to operate. My mig would be the first welder that I sold (if desperate for money that is) as it is only a "1 trick" pony although I do admit it does that 1 trick very well but I paid dearly to have that capability in comparison to the stick machine.

 

[cdaigle430]

Thats funny, I hear the 7018 is called the idiot rod, or maybe it was called the monkey rod?