Brass Wire Annealing

Hi everyone,

I am a new member to this forum and a newbie for Brass wires. Would sincerely appreciate if you all experts out there could help me with some technicalities for bright annealing Brass wires.

We have vacuum Pit Furnaces as well as Bell Furnaces which can handle Protective Atmosphere of 95% Nitrogen and 5% Hydrogen.

The problem we face is that we have to manufacture Bright Annealed Brass Wires the Brass is 80:20 as well as 63:37. Pickling after annealing is not acceptable to the customer.

The problem is that brass wires when drawn has a very bright luster on it and when it is annealed at 425 Degree C for a a soaking of 10 hours and then pulled out at 40-50 Degree Celsius the color of the Brass wires becomes black.

When we pickle it in sulphuric acid and rinse it with deionized water the original brass color pops up, but the drawn luster is lost as the surface is etched.

Our customers requires a bright annealed surface.

Can anyone suggest what I should follow on the Pit Type Vacuum furnace with respect to the vacuum to be kept. We are holding a vacuum of -25 inches of Hg or about -635 mm of Hg. Once the vacuum is achieved, we fill the retort with mixture of nitrogen and hydrogen 95%+5%) and flush out the retort twice with this mixture to eliminate any oxygen content. Then we start heating, then soaking and finally cooling.

In case anyone needs more details I would be too pleased to provide them.

The wire diameter are 4mm and 5mm.

Any suggestions would be highly appreciated.

With Best Regards / Vidu

Hello Vidugoyal,

As an experiment, cool the just annealed brass wire down to room temperature before removing it from the furnace.

This will tell you if your problem is actually in your annealing process.

We also were not sure what you meant by the statement "luster is lost as the surface is etched. What did you mean by "etched" because we understand that as a controlled chemical process?

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641- 3212

Hi Peter,

Thanks for your reply, the Term Etched was used by me to state that the acid eating away the Oxide Layer on the brass wire and also some Metal from the Pickled Surface. It was not my intention to inform you a controlled chemical action. I apologize for this.

Yes in the next Cycle we are going to pull out the material at room temperature.

Can you suggest what annealing temperature should I use and for how many hours do I soak the wires to get a tensile of around 27-30 Kg per sq. mm

With Best Regards

Vidu GOyal

Hello again Vidu,

Thank you for that clarification. Hopefully we can get the brass wire bright right out of the annealer from now on. It will however oxidize as time goes by just like bright copper. Pease see the following thread for a discussion on oxidized copper www.wirenet.org/forum/viewmessages.cfm?Forum=12&Topic=387

As far as the annealer settings go, I do not know but you may be able to get annealing curves from your annealer manufacturer or perhaps a recommendation from the Mechanical or Metallurgical Engineering Departments at a good local University.

Regards,
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641- 3212