Inquirer:-

Tubes: SB-111 UNSC44300 (Nominal Composition: 71Cu–28Zn–1Sn–0.06As) TO Tube Sheet: SB-171 UNSC46400 (Nominal Composition: 60Cu–39Zn–Sn) Tube to tube sheet Welding possible ?

Reply:-

Thank you for submitting your query.

I have studied your query and found the following findings :-

The SB-111 UNS C44300 tube material is an admiralty Brass alloy, while the SB-171 UNS C46400 tube sheet material is a naval brass alloy.

From the a metallurgical point of view, the presence of Zn in your  Tube material composition SB-111 UNSC44300 (Nominal Composition: 71Cu–28Zn–1Sn–0.06As) & Tube Sheet material composition SB-171 UNSC46400 (Nominal Composition: 60Cu–39Zn–Sn) reduces the weldability of the material. As with respect to copper, to add in that , the low boiling point of zinc means that zinc fume is produced  during welding so you must have to have ventilation precautions to deal with both zinc fume and copper fume as well. Zinc can cause porosity problem in your weld metal so need to have proper shielding gas flow to protect the weld pool. 

A common choice for welding brass is a silicon bronze filler metal. Silicon bronze, such as AWS A5.7 ERCuSi-A, is often used for Gas Tungsten Arc Welding (GTAW), or TIG welding, of brass. This filler metal offers good color match and mechanical properties.

I am rather thankful to an expert Mr. Savio Dias from ASVOTECH , Mote Mor , Brazil for bringing to my notice some typo correction made with the previous draft & suggesting me with a choice of filler metal mentioned above.

I suggest to run a procedure qualification test for the conformation.

I hope this suggestion might help.

Source:- 

http://surl.li/ijwkt

https://www.twi-global.com/technical-knowledge/faqs/faq-how-can-i-weld-naval-brass
AWS Welding Handbook Vol. 5 

(https://weldingmaterialsales.com/catalog/ercusi-a-silicon-bronze/)