Brazing Question

[Teacher]

Today I was trying to braze two pieces of mild steel together and could not get the rod to melt. I was using MAPP and UNI-1500FC rod. Even when I directed the flame directly on the rod, it took 2 or 3 minutes for even a drop to come off. Any ideas? I've never brazed with MAPP before, always used OA but wanted to try it.

Thanks for any help.

Teacher

[GWIZ]

What size rod ?
Is the torch jetted for Mapp gas ?
Did you do this outside in the cold air ?

I prefer silver solder.

[CEC]

I will not be able to help on this one but I'm interested in the answer.
I've always used OA myself also to gas weld and braze.

CEC

[Teacher]

This is the description given by a seller for the rod I'm using.

Uniweld Copper Alloys 3/32” X 18” Rd

uni-1500fc (flux coated) universal low fuming
bronze brazing alloy Low fuming brazing alloy
Excellent for brazing both steel and cast iron
as well as yellow brass and bronze casting
Flux coated (FC) or bare as required



Thanks

Teacher

[cutter]

Originally Posted by Teacher

Today I was trying to braze two pieces of mild steel together and could not get the rod to melt. I was using MAPP and UNI-1500FC rod. Even when I directed the flame directly on the rod, it took 2 or 3 minutes for even a drop to come off. Any ideas? I've never brazed with MAPP before, always used OA but wanted to try it.

Thanks for any help.

Teacher

Okay Teacher, I'm feeling bad about this 'cause you're not getting any answers so here's a bump.

Now to be clear, are you saying that you're using MAPP only - no oxygen?
I've use MAPP only to solder copper pipe, don't seem to me you'd get enough heat to successfully braze without the o2.

[Teacher]

Thanks cutter.

Yep, just MAPP no oxygen. It looked lke I wasn't getting enough heat but the melting point of the rods is ~1600F while the MAPP is supposed to burn at over 5000F.

Teacher

[rickairmedic]

Teacher heres the bad news you are not gonna Braze with straight MAPP I have tried and its just not gonna happen at least not with a hand torch now with a B-tank set up it is possible but the torch head itself is desighned for it and burns hotter . Even then I have only brazed with stick silver with a Btank setup. This was also on Copper pipe I dont think you are going to get steel hot enough with MAPP to braze and the base metal has to be cherry red at least every time I have brazed it did .

Rick

[cutter]

Well, even if you were able to melt the rod that don't mean you can braze.
You have to heat the base metal hot enough (dark cherry red) for it cause the rod to flow.

[rickairmedic]

Yep what Cutter said I was editing my post when Cutter posted the golden rule if the base metal isnt hot enough the rod wont flow.


Rick

[GWIZ]

Its been a while since I used Propane for brazing.
If it gets windy or cold outside it will be difficult.

The rod
BernzOmatic, NS-3, Nickel Silver.
Working temp 1250 - 1750.

I didn't have a brass rod. as I recall they need more heat then the silver rods. long time ago I had to braze some brass and the brass part was melting before the brass rod, so I switched too the silver and that's all I use.
I think brass rod is the choice for steel but, I don't braze steel I weld it.

(1) Propane.
BernzOmatic, JTH-7 torch. the torch is a big difference then the old ones 30 years ago.

(2) Two pieces of steel about 1"x 2"x 1/16"
I did not clean the steel.
The flux in the picture did not work vary well, maybe I did not use enough. the flux on the rod took care of it.

I did notice, the rod would not melt directly off the rod vary well, once on the steel it flowed with additional heat.