brazing question

[tonymjr]

When brazing copper tubing to a steel fitting using 45% silver with flux, I find it necessary to heat the copper first and allow the steel to absorb the heat and allow the silver to flow into the fitting. Does anyone else find this to be true.

[bjefferson]

years ago I worked for Dunham Bush.I had to take a class in brazing before I could get the job.The way the instructor told us to braze steel to copper joints is to heat the steel first.Because it takes longer to heat up,but once it is hot it stays hotter longer.By the time the steel was hot the copper was ussually hot enough to braze.

[mrhvacmechanic]

I heat the seam of the joint first and then draw in the solder into the socket side by moving the tourch to the bottom of sockey once seam is hot enough to melt silver. Harris solder recommends this procedure and so far it has worked for me.

[bribone]

Thats how they taught in a class I took also. always heat the female joint, when hot enough it sucks the solder right in the joint.

[amickracing]

Well, both flavors of answers are right.

welding 101, all metals heat up differently. You want (need) to make sure the metal is the right temp for brazing, and with 2 different materials that gets kinda tricky to not over heat or under heat one of them.

Once they are in the ballpark though, definitely work the female side and pull it in.

[gbfromsd]

The important thing to realize about steel is it does not conduct heat very well at all. The spot right under your torch tip will turn cherry red and take a bead, but half an inch away nothing. Copper on the other hand is an excellent conductor of heat. Preheat the copper, then you pretty much just need to keep the steel heated properly. As soon as you move back to the copper to pull the filler in it'll come right up to temp.

[DPSwitch]

Copper first, get it about rite, socket for just a few seconds and do it.