Keeping the heat in when brazing

[marinaman]

Having difficulty keeping the heat in and even when
welding small modeling bits together
I could do with an asbestos blanket if anyone has one

 

[Spark plug]

Fire bricks are my go to

 

[123hotchef]

tell us more

 

[mike os]

fire bricks and or a bigger heat source

 

[Seadog]

I used Hardibacker when silver soldering this chunk of steel and gas barrel, and a MAPP torch.

 

[graffian]

I use some old very light breeze blocks.

 

[optima21]

I use lightweight refractory bricks, but if I didn't have them I'd be using light firebricks....... if someone offers you bricks out of storage heater, I wouldn't use then as they are dense bricks so absorb heat rather than reflecting it.

 

[Kram]

I use fibreglass exhaust bandage to wrap long round bars if only one end is being brazed. Works very well but melts if you get the flame directly on it.

Garden centre perlite is good. Mix with sodium sillicate to make solid bricks, and is the insulation for my furnace. Avoid breathing the dust! (of any refractory!)

Two inches of perlite can be 1000c on one side and under 50c on the other, after prolonged heating, it lets very little heat through.

Last is to use better quality silver flo 55 instead of brass braze. It costs more but uses a lot less heat and gas.

 

[gaz1]

heat blanket absorbs heat

hardibaker is more for protection

firebricks only work better in heat reflection once they become warm or heated then they reflect heat rather well

the important part is to create a non draft area where you can braze so you need to construct a shelter of some sort around your working area the smaller the piece the smaller the work area

 

[James1979]

Having difficulty keeping the heat in and even when
welding small modeling bits together
I could do with an asbestos blanket if anyone has one

What are you making out of interest?

Also. What’s your heat source? Usually the problem is too much heat on small parts, not lack of it.

 

[brightspark]

I use some old very light breeze blocks.

yep pack broken soft grey thermolite bits of blocks round the job works a treat

 

[BarrieJ]

Use bricks from a night storage heater, construct an 'enclosure' to reflect heat back onto the workpiece.
Better than firebricks.

 

[marinaman]

Ta.
Lots of ideas I had not thought of.
I was using acelylene to braze a steel washer round the end of a small bass tube about 15mm dia.
The washer got plenty hot, but the brass tube did'nt and cooled down fast.
True, thermalite blocks are easily cut and sculpted.
I had not thought of hardibacker.

For small amounts the silver 55 is probably the best bet.
I do fancy making an electric steel tempering kiln, so will try making pearlite and silica bricks
I had heard of glass fibre for exhaust repair but didn't find any suitable.

Thanks for your reply,

 

[James1979]

Brazing brass is hard because of the similar melting points of the parent metsl and the filler.

Silver solder is the way to go for sure

 

[marinaman]

I know no one is reading this anymore but just for completion
I bought some silverflow 55 smothered it in brasing flux,
got it too hot and stuck it together