Questions About Metal Thickness

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SteveHGraham
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Questions About Metal Thickness

Post by SteveHGraham »

It has become even more obvious to me that I don't know anything about welding.

This week, I watched an Abom79 video playlist, and he was welding some big parts with TIG and stick. In one video, he had one roughly rectangular part maybe three inches thick, and he welded it to a tube with walls that were something like 3/4" thick.

Here's the question that was going through my mind: "How?"

When I got my MIG, I went as big as I could with my power supply, and with gas, I'm limited to metal 3/16" thick. I know you can cheat by beveling and making repeat passes, and I know Abom has a bigger welder than I do, but I can't believe the owner's manual says, "Go ahead and weld stuff 4" thick."

What am I missing here? How is he getting penetration?

I really want an Off-Road Swag finger brake kit for my hydraulic press, but it requires welding, and some of the parts are half an inch thick. I figured it was a lost cause. Am I wrong?

I'll post one of Abom's videos.
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SteveHGraham
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Re: Questions About Metal Thickness

Post by SteveHGraham »

Also, the Youtube thing on the new board doesn't work.
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SteveHGraham
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Re: Questions About Metal Thickness

Post by SteveHGraham »

So the only system it doesn't work with is Windows 10, the most popular OS on earth. Could be worse.
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Marty_Escarcega
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Re: Questions About Metal Thickness

Post by Marty_Escarcega »

It has nothing to do with versions of Windows as I am on 10. We need the correct YouTube video address
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STRR
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Re: Questions About Metal Thickness

Post by STRR »

Hello Steve,

In order to get this thread back on the original track; Even with high amperage stick welders, you can't get penetration 3/4" deep. Just because the steel is 4" thick, doesn't mean he's welding 4" deep. It also doesn't mean it has to be 4" thick at the weld, only 4" thick in the center where the force is being applied. I haven't watched his video so I don't know what he is building.

The key is getting an excellent bond between the two pieces. Welds can be used to hold a piece in position without having much stress placed on the weld, such as in a compression situation. Welds can be used in a "shear" strength position. These have to be stronger to give the shear strength needed. And, welds can be used in tension applications. I believe these welds need to be the best in all aspects as their strength will be pulled upon most or all of the time, without support from the steel pieces.

Thus, the key is getting the best weld you can, and not 3/4" penetration.

As an example, I was tasked with welding 2" thick pad eyes on the front of a crane to allow tying the hook back during travel. We beveled the pad eyes but were not able to do any more than remove the paint on the crane frame. As I am not a good welder, and I know you're supposed to weld "up hill", I had to weld down hill due to my extremely poor up hill welding abilities. After completion, the pad eyes were tested by pulling on them with the crane hook block. We put 80,000 lbs of pull on the welds and there was no evidence of any pull at all. Boosted the heck out of my self esteem.

I recommend watching Welding tips and tricks . com on you tube. Jody is an outstanding welder and an excellent teacher. I have never seen a better technical welder. You know his welds are going to be tested to their limits.

I believe you have the equipment and the ability to get your welds done well. You just need the confidence to do them.

Good Luck,
Terry
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SteveHGraham
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Re: Questions About Metal Thickness

Post by SteveHGraham »

Thanks, Terry. It sounds like the thickness limits in the welder manuals are deceptive.

Here is the full URL of the video: https://www.youtube.com/watch?v=tbuUx2V0M5g&t
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10KPete
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Re: Questions About Metal Thickness

Post by 10KPete »

The thing to keep in mind here is that the only melting of metal is within the puddle created by the electric arc. It is exactly a small electric arc melting furnace. A small one. So arc welding is a process of creating, and manipulating, a small puddle of molten metal. That includes, of course, what ever machanism the process requires to exclude the atmosphere from that puddle.

Welding together thick sections is nothing more than putting down many 'beads' of weld, each done very well.

Pete
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choprboy
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Re: Questions About Metal Thickness

Post by choprboy »

In addition to what STRR noted, I would add that there are several things you can do to increase penetration and weldability of large pieces. These include preheating the base metal, using different welding fillers (i.e. deep penetrating 6010 vs. 7018), using different shielding (i.e. helium/hydrogen in TIG), and using different arc force settings (if your welding supports it). Past a certain point, the large the welder you have, the more material you can lay down in a single pass, not that you are getting deeper penetration into the base metal. A smaller machine just means more passes.

Welding uphill vs. downhill really depends on the filler. 7018 is very unforgiving, and not recommended, downhill due to the runniness of the flux (it blobs up and will run right into the arc). 6010/6011 are commonly run downhill and the flux that forms tends not to run away, solidify just behind the weld puddle. I find 6010 very easy to run up or down, but puddle formation is hard to control with early inverter machines. Some rods, like 7024, are so runny that can;t be run up or downhill.
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SteveHGraham
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Re: Questions About Metal Thickness

Post by SteveHGraham »

I have a 180-amp MIG. That's it. No torch, no stick, no TIG. Think I should be able to get acceptable weld quality if I tried to put this kit together?

http://swagoffroad.com/20-TON-Finger-Br ... _p_86.html

It's an extremely cool product. If I get a Grizzly pan brake, it will bend what? Maybe 20-gauge steel? This thing does 5/8".
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warmstrong1955
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Re: Questions About Metal Thickness

Post by warmstrong1955 »

Depends on the welder.

Horror Freight, and flux core only.....maybe.
A Miller, Lincoln, or Hobart, or something real, with gas shielded wire.....yes.
I have a Miller 135, runs off 120V, that I use for thin materials, generally stainless. I have used it for 1/4" mild, which is about the max for the little thing. Thicker than that, a some preheat is required, and multipass.
Most of the time, I use my ol' PowCon for anything 1/4" & up.

Bill
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Steggy
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Re: Questions About Metal Thickness

Post by Steggy »

I have a 250 amp MIG unit. Using 75/25 gas and .045 wire I am able to make sound butt welds on 3/4 inch steel in a single pass with about 60-70 percent penetration per side. Deeper penetration can be achieved with CO2 instead of 75/25. although smoke and spatter will increase and weld appearance will be rougher. As I do little structural welding I mostly use 75/25. I can get about 50 percent penetration in 3/4 inch steel with 75/25.

Claims of being able to weld four inch sections with the typical Chinese-made welders sold by Harbor Freight and the like are nonsense. Doing so with those lightweight units requires multiple passes. There is no substitute for machine output when it comes to welding heavy sections.

MIG welding should generally be done with a weaving technique, as the area in which the arc's energy is concentrated is quite small, which means the area of penetration is quite small. On lightweight sections, a weave of one to two wire diameters is usually sufficient. On heavier joints I use a weave that is three to five wire diameters. Weaving is especially important in vertical and overhead positions in order to get adequate penetration and to avoid sagging, as well as undercutting at the weld's edges.
Last edited by Steggy on Sun Nov 06, 2016 1:24 pm, edited 1 time in total.
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SteveHGraham
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Re: Questions About Metal Thickness

Post by SteveHGraham »

The welder is a Lincoln 180c. I'm really tempted to try an AlphaTIG TIG/stick machine one of these days. The reviews are surprisingly good.
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