Why Metal Won't Stick When Welding?

Pmedic828

Pmedic828

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Hope everyone ate too much for Thanksgiving - now I'm back in my shop attempting to make a table support for my drill press. I am using 3/8' CRS plate for a bottom support for my drill press as the cast table that I had fractured and I discarded the original table. Here is my problem.... When I attempt to weld a piece of 3/4 sq thick walled tubing to the plate, I seem to get a good flow puddle between the side of the tubing and the base of plate. After letting it cool, I picked the piece up by the tubing and it fell off and separated from the plate - the 3 other pieces of tubing separated after a slight hammer blow sideways to the tubing.
I used a wire wheel to clean both the plate and the tubing. Then I clamped the pieces together. The ground clamp was attached close to the welds on the plate. I am using a Lincoln 180A wire welder with the settings of "C" and "3" and it seemed to be hot enough. When I attempted to re-weld these, I increased the amperage and wire speed and it burned thru the tubing really quick. I had to plate metal back on the tubing and then attempted to grind. I am using flux core 0.035 wire which is a quality Hobart wire.
I profess that I am not a professional welder - not even a novice - basically I can get 2 pieces to stick together usually but am now asking for help to remedy this problem. Your thoughts gentlemen......
 
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Dissimilar metals? I've always brazed cast, not sure if the two can be joined welding.
 
Cast iron. Too much carbon.
An alloy of carbon and iron containing 2% or less carbon is known a "steel".
Above 2% it is considered "cast iron" which is not easily welded if at all. I have successfully welded very low carbon cast irons in the past using nickel filler material made for this purpose, preheating and slow cooling is necessary. At best it is not ideal.
 
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Might be worth posting a pic of the weld, as you say crs to crs is normaly nice and easy (i only play wit a little stick welding)

If you give them a rub with the grinder do they spark the same?.

Iv'e had issues wih the mill scale on crs causing some bad weld issues.

Hope somone can help,

Stuart
 
Are both the CRS plate and square tubing ground down to bare metal?
Is there any milscale or other junk coating either piece?
Any porosity in the weld?
If you are burning holes in it then you are more than hot enough, which leaves me to believe it is poor wire (the hobart stuff is pretty standard, better than the lincoln junk thats for sure), or dirty materials.
 
I've seen all kinds of crazy stuff welding. One time welding I watched the puddles rolling away from the other piece I was trying to join. Craziest thing I've ran into yet. All the other pieces of the same metals joined easily. It was like a magnetic force pushing it away.

If I'm having trouble joining two pieces I'll weld a pass on each piece then weld them together.
 
When welding thick to thin, I concentrate the arc on the thick and briefly bridge to the thin. I weld sheet metal to much heavier steel that way. You should see a good puddle on the plate before you attempt to bridge to the thinner tubing. Weave back and forth with the bulk of time on the heavier plate.

Bob
 
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