Letter 15043

Annealing of copper wire

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Dear Sir,

We are manufacturing copper uninsulated wire used for electric cable and also super enamel insulated wire. The size of the wire varies from SWG 1 to 32. We are facing a problem of having the wire oxidized/blackened soon after bringing it out from annealing Chamber. The annealing Chamber is of vacuum type having Induction coil to heat the copper wire. The Vacuum that can be applied to the Chamber is 500mmHg while the temperature approx.800+ centigrade. Please note the Chamber does not have any temp.meter. This is the process we are following to anneal the Copper wire. So, may I request to let me know how we can get rid of the problem of getting the wire oxidized/blackened in course of annealing.

Hope to hear soon.

Thanking you,

M.SADEK
- Dhaka, Bangladesh.

Try letting the copper cool in an inert atmosphere before exposing it to air.

Trevor Crichton R&D practical scientist - UK

Alternatively let it cool in the vacuum environment used for the annealing.

Bill Reynolds    consultant metallurgist Ballarat, Victoria, Australia

We are facing the same exact problem and I thought it has something to do with annealing current / voltage ...we uses stainless steel cylinders for annealing.
(not nickel coated as usual ..)

any idea ?

Amir Sharon
- Israel

You have not mentioned the quantity of your batch for annealing and also the kilowatt rating of induction heating. You have to also mention the cycle time of heating, soaking and quenching. What is the sealing mechanism used during annealing to prevent outside air entering. Without temperature indicator, how did you measure the temperature of your batch during annealing continuously?

Balasubramanian Venkatraman
- Navi-Mumbai, Maharashtra, India

WE ARE MANUFACTURING COPPER TUBE, TO BE USED FOR ELECTRICAL TERMINATIONS
WE CONTINOUSLY CAST THE TUBE , THEN DRAW THEM DOWN ON LONG HYDRUALIC BENCHES, AFTER SEVERAL DRAWS, THE TUBES BECOME TO HARD AND SNAP. WE LOAD THE TUBES (ON AVERAGE 2 TO 3 MTR LENGTHS) ON TO A RACK.
ROLL THE RACK INTO A ELECTRIC ELEMENT FURNACE (3.4 MTRS LONG)
WHEN THE TEMPRETURE REACHES 550DEG C THEN THE RACK IS REMOVED,
THE TUBES ARE LIFTED OUT OF THE RACK USEING CHAINS AND A HOIST AND THEN LOWERED INTO A WATER BATH TO QUENCH

WE ARE LOOKING FOR A MORE ACCURATE WAY OF ANNEALING TO IMPROVE OUR QUALITY AND PREVENT CRYSTAL REGROWTH.

ARNE HERZ
ENGINEERING - JOHANNESBURG SOUTH AFRICA

December 30, 2008 We manufacture Hot dipped tin plated copper wire. After drawing the wire the elongation is about 12 to 15%. We use vacumme annealing furnace. The heating is carried out using diesel burner & it is controlled by electrical circutry to control the temperature. The temperature raised & is maintained @ 250 C & the duration is about 2 Hrs. Burners are switched off automatically at this time. The furnace is kept under vacumme containing copper wire, untill the temp. drops down to ambient. The elongation of copper wire after the process is about 25% to 28 %. Can any one guide us to achieve more elongation Say about 35 % max. ????????? Sudheer Shedbalkar mfg. hot dip tin plating - Pune, Maharashtra, India January 8, 2009 Try faster cooling . Cair Shishani aircraft maintenance - Abu Dhabi, UAE March 29, 2009 we r a cable manufacturing company n want to know how copper can be annealed and to what temperature ? is there any cooling curves to follow or is there any need for a vacuum furnace to put in so to avoid oxygen contamination ?? please give us useful sites for this respect ..thanks a lot Eng.Amjad Qade employee - Kuwait