Entry Level Welding Help

[PineRidge]

<font color="blue"> Yes, a cutting torch uses a preheat flame to heat the steel above its kindling temp. Then the torch's O2 lever is activated which 'squirts' a stream of high pressure O2 onto the hot steel. By delivering a higher than normal level of O2 to the hot steel it burns. Theres not enough O2 in the atmosphere to cause this w/o a boost (which comes from your torch). While the steel is burning you're not consuming anymore fuel gas but ALOT more O2. Hence the stmt 'you need alot of O2'. I think the ratio is something like 8 (or more) to 1 O2 to fuel gas. Ive had my gas rig now for 3 yrs and have used nearly no acetylene but most of full large cylinder (80cf...I think) of O2.
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Jimg the fact is once the cutting process has been started you could actually completely turn off the Acetylene and continue the cut with a steady hand using only the Oxygen cylinder. The Acetylene is only needed in the preheat process.

 

[jimg]

Yup, thats right...once started it will go on its own. Thanx for making that clear! /forums/images/graemlins/smile.gif

 

[BuckHunter69]

<font color="blue"> </font> once started it will go on its own

<font color="black"> </font> To a point only! On steel that is 7 ga to 1/4" you may be able to cut another 1/2" to 3/4" without preheat, but you would really lucky to get that far. On lighter guage metal, you wouldn't have enough baseline heat to continue cutting much, if any. On heavier metal...well, since we're talking entry level, it doesn't deserve much comment.

The point that I'm trying to make is that it can be done to a point, but it's not worth the frustration in attempting to do it just to save acetylene.

Before becoming a desk jockey, I welded production for 10 years (mostly 3/8" to 1/2" mild and stainless, manual, mig, and sub-arc). My dad owned a welding shop, so I also did my share of mainenance welding.

 

[BuckHunter69]

My 2 cents...

If you do decide that you need to learn to weld and own a welder, I would recommend a 240V Input 225A-250A AC welder that has high and low ranges. (It's been years since I bought mine, but I would guess ~$250)

I would suggest getting lots of practice on 11 ga (1/8") or 7 ga (3/16"). You won't have burn-through and you'll be able to see how well your penetration is. Practice on heavier metal requires lots of heat and a garage welder isn't made for that.

Low range (low frequency) is better for the beginner because it will be easier to hold the arc.

For all of you do-it-yourselfers, make note of the duty cycle of your welder and use you better judgement.

DC welders are MUCH better, but you get what you pay for.

 

[PineRidge]

<font color="blue"> To a point only! On steel that is 7 ga to 1/4" you may be able to cut another 1/2" to 3/4" without preheat, but you would really lucky to get that far. On lighter guage metal, you wouldn't have enough baseline heat to continue cutting much, if any. On heavier metal...well, since we're talking entry level, it doesn't deserve much comment.
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Cutting steel with Oxygen only, no fuel. You can indeed take 1/4 inch plate steel, preheat it, start your cut, shut off the acetylene and with steady movement cut steel any length indefinitely. Don't take my word for it, look in the Welders Handbook that I mentioned in an earlier post on page 74. Lots of good useful info there.

 

[Lazy]

Hi
What other magic tricks are in that book.. /forums/images/graemlins/cool.gif

Charlie.

 

[PineRidge]

Charlie I have always considered something magical myself about permanently fastening two or more chunks of metal together using welding techniques. So if you like magic too, you'll have to get a copy for yourself to see. /forums/images/graemlins/wink.gif

 

[jimg]

I dont think anyone was advocating that the torch be turned off after the burn starts. The point was that cutting consumes much more O2 than fuel and the reasons for that were stated. In that vein it was also mentioned that once the burn starts only O2 is needed to keep the burn going....all of which was correct. So, whats your point?

 

[jimg]

"I would suggest getting lots of practice on 11 ga (1/8") or 7 ga (3/16"). You won't have burn-through and you'll be able to see "
Hows that? Thinner stock is much easier to burn thru.

"Low range (low frequency) is better for the beginner because it will be easier to hold the arc."
Could you explain this more? What would 'low range' be and why would it make it easier for a beginner to hold an arc?

"For all of you do-it-yourselfers, make note of the duty cycle of your welder and use you better judgement."
What does this mean? Is it advice to get a machine w/ high duty cycle or not to exceed the spec'd duty cycle?

"DC welders are MUCH better, but you get what you pay for."
Really???? How so?

 

[BuckHunter69]

First off, I won't get into a p-match about O-A cutting without preheat...practice and theory are two different things...'nuf said.

"Hows that? Thinner stock is much easier to burn thru."
Selecting the proper heat (amperage and arc length both play a part) is something that is learned. To first begin welding on 12 ga and lighter steels will often result in burn through. Selecting the 11 ga and 7 ga as practice plates will give a lower likelihood of burn through while allowing you to see well your penetration is. By immediately selecting 1/4" and thicker steel as your first welding attempts will surely result in what we refer to as pigeon-s**t (the weld material sits on top of and not bonded to the base material).

"Could you explain this more? What would 'low range' be..."
The simple explanation for low range (frequency) being better is that the arc behaves more like DC.

"Is it advice to get a machine w/ high duty cycle..."
Concerning duty cycle...Garage welders are typically 30-50% duty cycle (at n amps). If you exceed the duty cycle for too long, you can damage you welder or worse. Fan cooled welders typically fare better than free air.

About DC welders...There are many more options (in rod selection and welding positions) available for DC. I don't know ANY professional (production or maintenance) welders who prefer AC over DC for mild steel (stick welding). DC is easier to use and produced better results (but the units aren't cheap. About the only practical AC welding rods are 6011 and 6013 (probably the most popular AC rod). You can weld 7024 with AC, but there are caveats (I won't go into details at this time).

With DC, you can use all of the 3 AC rods, plus you can use the n018, n027 type rods. n018 is probably the most versatile rods made, primarily because it is all position. I can weld with 7018 (3/32") with my low-frequency AC welder, but I've had more practice than most.