BeCu extension spring

[JohnPP]

I am working a project : To use BeCu wire to make an extension spring ( gasket ) for EMI shielding . I have asked the spring coil vendor to make the coil for me ( wire diameter is 0.19mm and to form coil diameter 1.0 mm with spring about 140 mm length ) I use BRUSHWELLMAN Alloy 25 with 3/4H , after coil forming , the springs were heat up 600 degree F for 20 minutes . The outcome is unexpected : The pitch of the coil extended to total length about 200 mm and discoloured .One of BRUSHWELLMAN engineer told me that it is the effect of stree relief .Please advise what were wrong ? The material spec ? The treatment temp and timing ? What will make the finished part with the original colour , with spring effect and not extended the total length ?
I have asked this question in the material engineering group , but it may involve the mechnical setting as well !
Is it problems spring making setting ?- negative pitch/zero pitch setting ? Thanks ,

 

[zekeman]

Why would you want to reheat the spring in the first place?
But if you need to,why don't you let the spring manufacture do the reheating, which will possibly anneal the spring and will surely deform the initial geometry ( as you were told) due to stress relief of the spring.
You must know that in the process of coiling a spring, the cold working of the spring causes internal stresses in the spring material which are not generally relieved before delivery of the spring to the customer for the same reasons that you experienced.

 

[JohnPP]

Thanks zekeman ,
The agent of Brushwellman told me to reheat it after the cold work of spring forming ( actually I told our vendor to do the heat treatment process ), although she has no experience of forming BeCu extension spring . The reason she said is that it will release the main advantages and features of using BeCu.
I also have some samples without doing the heat treatment , it really not very flexible as some competitor's samples .
So , what is the more proper procedure to make a BeCu extension spring ?
Thanks

 

[CorBlimeyLimey]

You may also want to try the Spring Engineering forum693


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