Welding -- is current over 200A ever needed?

----- Original Message ----- From: Ignoramus1473 Newsgroups: rec.crafts.metalworking,sci.engr.joining.welding Sent: Thursday, May 18, 2006 8:31 AM Subject: Welding -- is current over 200A ever needed?

I am redoing my welder a little bit. I am considering whether I should have it configured to be able to produce above 200 amps. (note that my garage circuit breaker, at 60A, does not really let me use more than 200 amps welding current anyway, but I could possibly redo the circuit one day if needed).

The real question is, are welding currents above 200A useful to a person messing around with stuff at home. Here are some things that I am NOT planning on doing:

- welding big oceangoing ships - welding beams for scryscrapers - welding bridges and railroad tracks

All I want to do is to be able to weld whatever I might practically need, such as a trailer or a hydraulic log splitter or whatever (just some examples).

My welder is likely capable of doing 300 amps at some lowered duty cycle, it is rated for 100% duty cycle at 200 amps.

So... Would I need to even bother with going above 200 amps, or would this be a complete waste of time to try to have this capability?

i

Hello,

My take on this is no................. If you can burn a 1/8"

7018 welding rod, you should be able to build darn near whatever you want.....especially for home usage. I have a utility trailer that I made from scratch using a small buzz box about that size. It'll just take a little longer for the larger stuff is all. Rather than burning a 3/16" in one pass, you may need to lay 3 stringer passes to match the fill of a rod that size. Jim

I have a buzzbox powered by only a 30A/220V breaker to my garage. I run only 1/8" rods at 100 to 120A and have never had a problem with the breaker tripping (as an experiment I ran it for a while full out at around an indicated 200A and even then did not trip the breaker). So, I expect for your kind of work, 60A would be more than enough. I weld mainly 3/16 and

1/4" stock but have also done 3/8" with no difficulties.

Laurie Forbes

Jim, thanks. I kind of agree. Would it not be possible to use a 3/16" rod with 200 amps of welding current, though? I thought that the rule of thumb was 1 amp fo eevery 0.001 inch of rod, or 187.5 amps for a

3/16" rod? Is that wrong? i

As I recall this project was intended to give you the ability to weld with AC. About the only thing you really need AC for is TIG welding aluminum. And TIG welding aluminum is about the only time really high currents are necessary. 200 amps will be fine for 1/8" and barely adequate for 3/16" aluminum.

Ned Simmons

Thanks Ned... Got it... I will go for 300A capability (bearing in mind that my garage circuit is not capable of supplying enough power for

300A, but that could change later). i

Aluminum AC TIG takes lots of power. 1 per .001" plus 30% more says max aluminum TIG on 200 amps is well less than 3/16"

Stick welding amperages are a square of the diameter. 3/16" 6013 wants

200 to 250 amps. "Jet" rods with iron coating want even more. Your 200 amp max will give you a practical limit of 5/32" That should be good for 1/4" to 3/8" (depends > I am redoing my welder a little bit. I am considering whether I should

Thanks Roy, I will definitely go the 300A route. It is better to have it and not need it, than need it and not have it.

i

I wonder what the differences would be for production-oriented verses home-shop or prototype work? Obviously, you'd want single-pass speed in a production environment, but at home or for a prototype, could you take multiple passes at a lower current? What would be the practical limit with 200 amperes if time were not an issue?

Ernie L. claims to have welded 1" plate with a 120 volt wire feed with flux core wire. Something like 15 passes IIRC! In theory, you can just do as many passes as required.

In the real world, you want to keep the number of passes down to a reasonable number for effiency sake. Using the 'Jet' rods with iron powder in the flux, big rods, submerged arc, etc etc. One pass is better than 2 etc.

For the hobbist, the limit> RoyJ wrote:

One problem with aluminum and low amps is that the parent metal just doesn't get hot enough for adequate penetration because it sucks away the heat so fast. My neighbor bought a 120 volt wirefeed several years ago and was having no luck welding a trailer hitch. He knew enough about welding that it wasn't a good weld. I was taking welding classes at the time so he called me up to help. I didn't then, and don't now, have much time on a wire feed. But it was obvious that the 2 inch square bar that he was using for the hitch instead of 2 inch square tubing was sucking away the heat too fast. After heating the bar with a rosebud I tried a practice weld. Used a hammer to whack on the 3/8 plate I welded to the 2 inch bar till it broke off and it was obvious that penetration was now OK. So he ground smooth the place where I had run the practice bead and then welded up his assembly making multiple passes. With stick it's easier to get good penetration when all you have is a low amperage welder. ERS

So what I'm hearing is that there is a hard limit on what you can do with TIG and 200 amperes unless you preheat or the work is small enough in total volume that it doesn't wick away all the heat.

But quoting ... "My neighbor bought a 120 volt wirefeed several years ago and was having no luck welding a trailer hitch."

The wire feed tells me MIG not TIG. Not to say it would be much different in penetration, but maybe cleaner for multiple passes.

No expert here, but hoping if I ever need to, I can get the bigger things stuck together.

Aluminum has such a high rate of heat transfer that you really need to have enough heat in the welder to heat the metal all the way through (although preheating can help). Steel can be welded multipass, the limit is mainly in the quality of your technique.

Correct. There are some tricks you can do if your machine supports balance, squarewave, pulse/backround etc etc that may allow you to fudge some.

But yes..you buy a machine for the maximum type of work you are going to do..and like any machine..you may need to go to the next biggest size machine if your work increases.

Gunner, who welds 3/16" aluminum at 90 amps with no preheat..but with ALL the bells and whistles turned on, with the material laying on firebrick

"If thy pride is sorely vexed when others disparage your offering, be as lamb's wool is to cold rain and the Gore-tex of Odin's raiment is to gullshit in the gale, for thy angst shall vex them not at all. Yea, they shall scorn thee all the more. Rejoice in sharing what you have to share without expectation of adoration, knowing that sharing your treasure does not diminish your treasure but enriches it."

- Onni 1:33