Can MAPP Gas Braze Weld Cast Iron?

[Tinkerer2]

Against my better judgment I just spent or wasted some reasonable dollars on a MAPP gas cylinder, burner and rods to weld a grey metal cast iron piece which is just fitting a bit knocked out back into the rest.<br /><br />Surprise, surprise! It can't heat the two edges red in any form. We're only talking about 1/8" thick material. <br /><br />Is this what I should expect? <br /><br />Unfortunately it is what I did expect, but I hoped for better in light of the assurance on the packet that it brazed.

 

[Paul Moir]

Re: Can MAPP Gas Braze Weld Cast Iron?

Yes, sorry. They really shouldn't call it a brazing kit. It can just melt brass with patience. <br />I use it where others use propane though. Gets the job done much faster. Plus you get looks for running a howling torch. <br />Try to heat from the tip of the flame, about a half-inch in, it seems hottest there. If your using a torch where the flame begins outside the torchhead, your lost. You need the type that has a flameholder in it and gets orange hot at the tip and forms a nice cone. Then you just might be able to braze those peices together, if you're lucky.<br /><br />PS - That's my second favorite outboard tool, after the impact screwdriver.

 

[JB]

Re: Can MAPP Gas Braze Weld Cast Iron?

Hi, Tinkerer.<br /><br />I use a BernzoMatic Oxy-Propane rig for that kind of work. Small, inexpensive rig. Works about as well as a small OxyAcetelene torch, and with the same techniques. Most Ace Hardware stores carry the O2 cylinders.<br /><br />I think they can be used with MAPP, but I haven't found the need.<br /><br />Good luck.

 

[Tinkerer2]

Re: Can MAPP Gas Braze Weld Cast Iron?

Thanks Paul and JB.<br /><br />I should have stuck with my instincts.<br /><br />Paul, you're right about "just" melting brass. I was using the flame the way you said and it took ages for the rod to melt, and then it just comes off in lumps long after the flux has burnt off.<br /><br />JB, those kits were around here until a few years ago. Don't know why they've disappeared. For the quantity I'd use they'd work out cheaper than the annual rent on oxy-acetylene gas bottles. We can only rent bottles rather than own them here. <br /><br />Still, it's not a total loss as I've been meaning to buy a MAPP kit for a while for heating stuck bolts etc. Nowhere was open on Saturday afternoon that sold arc rods for cast iron (I have arc but not gas) so rather than wait till Monday I took a chance on the MAPP kit. I'm really only down a few bucks for the brazing rods. Only about an hour's worth of decent beer.<br /><br />Always costs money in the end when you get impatient and try to use something other than what you know is the right thing.

 

[Paul Moir]

Re: Can MAPP Gas Braze Weld Cast Iron?

Mabey your brazing rods can get together with the 'all but one' pack I have hanging on the wall. The one missing rod is still attached to what I can only call 'Artwork'.<br />I think I'm going to look into one of those rigs JB has. It's too bad you can't get those little tiny 1lb oxy bottles down under - I understand they don't go far, but they're awfully convinient.<br />Lately I've been seeing bottles of pure propadiene on shelves. Anyone know what that's good for?

 

[Bobby D.]

Re: Can MAPP Gas Braze Weld Cast Iron?

Hey Tinker,<br />Are you sure you are trying braze cast iron? The reason why I ask is because cast iron is not normally cast in 1/8" thicknesses. The reason is, that it has no strength being so thin and porous.<br />MAPP gas is hotter than oxy-acetylene.<br />There are different grades of cast iron and some are more easily brazed than others. Let us know how you make out. If you decide to arc weld cast iron you should consider preheating the cast iron before you weld too approximately 700 degrees.

 

[Tinkerer2]

Re: Can MAPP Gas Braze Weld Cast Iron?

Dude<br /><br />It's cast. It's the end cap off an electric motor about 7" in diameter. The centre section that holds the bearing cup and shaft has broken out very neatly where it's been dropped (not by me) on the shaft at the other end.<br /><br />The motor runs my compressor, but I'd forgotten I salvaged a motor of the same rating years back and it fits exactly.<br /><br />I ain't gonna be welding it with arc, either. Went to the main welding supplies factory outlet in my state on Monday. Smallest pack of cast rods is $120, and I'd use about $3 worth on my job. <br /><br />I'll just take it to a professional and get it done for probably $20, and done right.<br /><br />Thanks all for the advice.

 

[KCLOST]

Re: Can MAPP Gas Braze Weld Cast Iron?

In my limited experience welding cast iron, I've found that stick welding with nickle is the best. But heat the entire part evenly or you will see cracks form perpendicular to the weld. Heat it up to 1000F before welding, is what I have heard.<br /><br />Good luck

 

[StillFishin']

Re: Can MAPP Gas Braze Weld Cast Iron?

Why not try epoxy like JB Weld. I would think that that would work OK. Cast Iron is a tough to weld.<br /><br />StillFishin'