Springback

We are a manufacturer of enamelled wire. in our production we have problem with spring-back test of wire. sometimes it is good but sometimes not good. could you please help me how i can get the best spring-back?

Hello Mr Mohsen Ajalloueian;

I have contacted a magnet wire specialist for you and hopefully, he will post an up to date answer for you. In the meantime, here are two threads and one paper to read:

www.wirenet.org/wai-forums/5-electrical/...enameled-copper-wire
www.wirenet.org/wai-forums/8-nonferrous/1610-grain-size#1615
www.copper.org/publications/newsletters/.../wiremetallurgy.html

Thank You very much

I read the threads but I did not get the exact answer . we have hard wire, our elongation is from 30-38%. for sizes from 0.300mm up to 1.300mm. but we have poor ductility. our parameters are:
-horizontal line with inline drawing
- annealer oven length is 10m. 2 zones . temperature of annealer is 400 c.
- enameling chamber is 500 c. and for example for 0.75mm production speed is 50.

Hello Again Mr Ajalloueian;

Our magnet wire expert was not able to log in so this had to be corrected by WAI before he could even get to the web site. This is now corrected but he is obviously very busy and has not yet logged in.

Your "hit and miss" springback problem however should be fairly straightforward to sleuth out provided that you have the exact drawing and annealing history of the conductor including that just prior to, during and after enameling. When the springback problem surfaces, something has changed and that is what you must determine.

I suspect the problem lies in the orientation of the conductor grain structure . I believe that is where you will find your answer.. This of course assumes that your copper rod properties are constant and the you are following the exact same drawing and annealing procedures each time.

Please let us know what you learned. Thank you.

Dear Mr. Peter J

Thank you so much for your reply.

About the grain size i should inform that we produce our wire At approximately nominal size.
For example when we produce 0.800 mm - micrometer shows 0.798. and it is for all sizes and every time.

about cooper rod properties it may change but our customer say that just our wire is hard and other wire is soft.

Our wire also have the minimum enamel. so maybe i must change some parameters in enameling process or annealing?

Thank you

The following quotations at the Forums from other threads and penned by Dr. Horace Pops are very important"

“orientation”, which is a term usually associated with annealing textures that form within conductors.

Both grain size and orientation affect the mechanical properties of annealed specimens. In the case of copper, which is very anisotropic, lower tensile elongation and LSE, coupled with higher springback occur when the final reduction in area exceeds about 90%. This practice is harmful to the performance and windability of finish magnet wire. The aforementioned properties are directly dependent upon the specific annealing texture, which is affected by the amount of cold work prior to annealing. Poorest properties also occur for aluminum at similar high reductions. In contrast to copper, however, the decrease in elongation, windability and LSE with increasing prior reduction is attributed to the resulting finer grain size.

There was a paper written about 1967-69 by a BICC engineer discussing inline wire drawing as it relates to magnet wire. If I remember right you supposedly used a supply wire which you could reduce between 35% and 85%. If you reduced less or more then you should have a different size supply. the nice part about inline wire drawing was that you could have an enameling system that could coat 18 to 28 AWG and would only need perhaps 3 different sizes of input wire. Without inline you would have needed an input size for each finished size. You also have bigger payoff packages and slower payoff speeds.

Also when done right, the finished enameled wire had a higher tensile strength and better ductility or a lower spring back value."

Thus you see it is not just grain size.This may be the reason for your higher tensile strength. You may wish to discuss this subject face to face with a Metallurgist in Mechanical or Metallurgical Engineering or Science at a nearby University.