Ag content in brazing alloys

[TeeAr]

Hi there, I am facing to the input of lowering the Ag content in brazing alloys for big diameter copper tubes in order to save money.

I decided to realize some burst tests on two different tubes (diameter of 3ft, three of them brazed with low Ag content and three brazed with standard alloy).
Surprisingly, according to first results there seems not to be particular differences.
Results are comparable for the tubes brazed with the two alloys (higher and lower Ag content).

To my knowledge, Ag content should increase mechanical properties of the joint, therefore increase burst resistance.

One possible reasons of what observed could be the dimension of the tube.
Since diameter is quite big, it is hard to realize a uniform brazing over the whole diameter, therefore there is a better penetration of the less viscous alloy, the low Ag content one.

Do you agree with my considerations ?
Would you suggest me to realize different tests ? Which ones ?

Many thanks in advance

 

[boo1]

Consider listing what braze alloy you are using, wnat you are switching to, what is the service fluid and what tube alloy.

 

[TeeAr]

Hello, many thanks for your answer.
the topics are:
current brazing Ag25
new brazing Ag15
material Copper C12200

many thanks for your help

 

[TeeAr]

Apologizes, I almost forgot.
Operating fluid would be water or fluids with glycol.
Temperature won't exceed 300F.

 

[gtaw]

It is difficult to provide advice without knowing the particulars.

If the brazed joints are socket type fittings, the braze filler metal isn't going to affect the burst strength of the tube.



Best regards - Al

 

[Duwe6]

And with brazing, the annular gap of the fit-up assembly to be brazed is an essential variable. So is the 'wetting' ability of the filler material combined with the flux you are using.

Too many interrelated variables to give a reasonable answer. Sorry.

 

[TeeAr]

Hello,

first of all I'd like to thank you for all the kind answers to present mail.
Concerning your questions:

to Mr gtaw
- we are speaking about a butt brazing
to Mr Duwe6
I agree with what you write.
An hypothetical argumentation can be: may the less content of Ag help the wetting ability of the filler metal ?
In shorts: could it be better to reduce the Ag content ?
What is your opinion about ? Have I understood correctly your point of view ?

many thanks