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I've been meaning to ask this for a while. What is the best technique for welding thin steel to thick steel?

I have a 120V Hobart Handler 140 MIG (flux core) machine and a 250A DC stick welder but I tend to use the stick machine more often. I am completely self taught and do "ok" but needless to say I am a much better grinder than I am a welder. :)

I always struggle when I have to join a thin piece of steel to a thicker piece of steel. If I set the amperage to get good penetration on the thick material then it wants to burn through the thin material. If I use lower amperage so I don't burn through the thin material then I don't get good penetration on the thicker material.

Any words on wisdom?
 

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Your weld is only as strong at the weakest piece of steel. So you weld for the thickness of the thinner material and that’s the best that joint can be. :good2:

You can always add a doubler or even a gusset to add strength if needed.
 

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Your weld is only as strong at the weakest piece of steel. So you weld for the thickness of the thinner material and that’s the best that joint can be. :good2:
I agree

Worked in a welding shop in my previous life . . . that is what we did. :good2:
 

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If you have the space, overlap the two pieces of metal . . . that way you get room for two good welds, one on each side . . . also a very much stronger weld
 

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If you have the space, overlap the two pieces of metal . . . that way you get room for two good welds, one on each side . . . also a very much stronger weld
I would say that most of the time I'm joining thin to thick the two pieces are overlapped. One of my recent projects was welding some 1/8" brackets onto a hand dolly. 1/8" was what I had on hand. The tubing on the hand dolly was very thin and was quite difficult to get any penetration on the 1/8" flats without burning through the steel tubing.

I was also recently making a steel lid for a septic tank. I needed to weld little sections of 1/8" angle to the 1/2" steel lid to act as guides for the riser. In order to get any penetration on the 1/2" plate it was tough not to completely melt sections of those 1/8" pieces of angle. Fortunately it didn't have to look pretty or be super strong and the melted metal stuck just as good as rod filler. :) But still... it would be nice to get a good technique down.
 

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Everyone has said it already, but you should be at the settings for the thinner steel.
Preheating the thicker steel may also help with penetration.

One thing I found is that I can, with practice, weld with settings for thicker steel and sort of run the weld puddle into the thinner metal. Overlapping joints wouldnt work to well doing that, unless you had a bead already laid before trying to join, but I used to do this often on my tiller brackets.
3/16" square tube, with an 1/8" or thinner end cap. When I was making a bunch of them, I could get them looking awesome. Without practice, it takes a bit of time to get it to work for me again.
If you arent careful doing this, the end result is the same, burn through.

One more thing I was told long ago when I first started welding:
Its metal. If you goof it up, you can always add more.
 

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Heavily concentrating on the thicker material, then quickly taking the puddle to the thinner metal is the best bet, as others have said. MIG is also going to be the easier of the methods available to you. I wouldn't necessarily lower my settings all the way to the thinner materials settings, but I would try to preheat the thicker and also stitch weld it. Stitching to me means two things in this application, spacing welds out (like a three inch weld every six inches) and also taking breaks between welds to let the thinner material cool back down. If you need a continuous bead, you can always stitch until you have one. Most times, you don't need a full length weld in a situation where you're not holding fluid.
 

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I would say that most of the time I'm joining thin to thick the two pieces are overlapped. One of my recent projects was welding some 1/8" brackets onto a hand dolly. 1/8" was what I had on hand. The tubing on the hand dolly was very thin and was quite difficult to get any penetration on the 1/8" flats without burning through the steel tubing.
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Try using smaller welding rods and less heat and slower . . . can better control your weld and get sufficient penetration on both.
 

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Heavily concentrating on the thicker material, then quickly taking the puddle to the thinner metal is the best bet, as others have said. MIG is also going to be the easier of the methods available to you. I wouldn't necessarily lower my settings all the way to the thinner materials settings, but I would try to preheat the thicker and also stitch weld it. Stitching to me means two things in this application, spacing welds out (like a three inch weld every six inches) and also taking breaks between welds to let the thinner material cool back down. If you need a continuous bead, you can always stitch until you have one. Most times, you don't need a full length weld in a situation where you're not holding fluid.
I will try that next time. I really couldn't do much stitching as the joint was only 1 1/2" long. Guess I could have done a series of tacks.
 

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Try using smaller welding rods and less heat and slower . . . can better control your weld and get sufficient penetration on both.
I can try that. Most of my rods are 1/8".
 

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I can try that. Most of my rods are 1/8".
I mostly stick weld.

I have some 3/32" welding rods for the more delicate work . . . good luck with your fix.
 

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I cheat,,,
Clamp a piece of copper behind the weld joint,
you can weld 1/16" to 1/4" like they are both the same 1/4" thick.

Heck, I can weld 3/16" to 0",,, and get a good weld,,,





Most "real" welders think this is cheating,,
I welded those tines with 1/8" stick welding rod,,, :thumbup1gif:
 

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I cheat,,,
Clamp a piece of copper behind the weld joint,
you can weld 1/16" to 1/4" like they are both the same 1/4" thick.

Heck, I can weld 3/16" to 0",,, and get a good weld,,,

Most "real" welders think this is cheating,,
I welded those tines with 1/8" stick welding rod,,, :thumbup1gif:
I don't quite follow you. Where is the thick and where is the thin and what is the copper piece supposed to do?
 

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I don't quite follow you. Where is the thick and where is the thin and what is the copper piece supposed to do?
The copper piece acts as a heat sink and draws the heat out of the thin piece.

As was said earlier, try to focus your heat on the thick piece and "roll" your weld onto the thinner piece.

Sent from my SM-G920V using Tapatalk
 

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A lot of good advice here. The mig would be much easier because you can just keep giving it burst’s perhaps 3-5 then a short 5-10 delay then more bursts right beside the thin as has been said.. It is harder with the stick welder to do this.
 

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I don't quite follow you. Where is the thick and where is the thin and what is the copper piece supposed to do?
The only problem with welding thin steel is that the weld puddle makes everything molten, and the puddle drops away, leaving a hole.

Copper conducts heat so well, the heat of the weld puddle is not enough to soften the copper.
The weld will just set on the copper, in effect, the weld puddle gets chilled by the copper.

I could weld a Toyota car door skin to a 1/4" steel bar, the car door could not melt away.

That pic shows a thin tiller tine after 1/8" hard surface welding rod was electrically welded on the edge.
I probably used 110 amps,

Without the copper, the tine would just melt, and drop away.

The copper acts as a shelf for the hard surface to set on,,,

Try to weld copper some time,, it takes crazy amounts of heat to weld copper.
The 1/8" steel welding rod does not produce enough heat to make the weld stick to the copper,,unless the copper is paper thin,,,
 

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I can try that. Most of my rods are 1/8".
For thin stuff I use Lincoln Electric 1/16" 6013.
Shallow penetrating and you can cut you machine way back (25 - 30 amps) and still maintain an arc.

Far from as good as a Eutectic 1/16 NE 2000 rod, however that rod is no longer available. :banghead:
It was like putting down silver solder, easy to maintain an arc at low current, beautiful bead.
 

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Your weld is only as strong at the weakest piece of steel. So you weld for the thickness of the thinner material and that’s the best that joint can be. :good2:
That's pretty much what I've done in the past.

I think Jody of YouBoob's 'Welding Tricks & Tips' uses aluminum stock as chill bars for thin steel.
 
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