BeCu extension spring
BeCu extension spring
(OP)
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 1 hour . The out come 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 ? Thanks





RE: BeCu extension spring
There is a volume change on aging this alloy, you can't avoid the changes. Do you really need the aging for strength?
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RE: BeCu extension spring
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
RE: BeCu extension spring
Is length really critical in your application? could you make them short and stretch into palce?
If the springs are clean I wouldn't expect any discoloration at 600F.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: BeCu extension spring
I can picture the discoloration but not change in geometry. Do you mean that the as-formed compressed coils extended thereby increasing the pitch during heat treat to make it look like a compression spring? Or do you mean that the 1.00 mm pitch dia changed or both?
RE: BeCu extension spring
As in the other thread link , I mentioned that I better describe it as I am making a BeCu extension type garter spring fpr EMI gasket purpose , and the pull force needed is not very important and I can use the basic trial and error method to make one with correct length .
So the questions remain are :
(1) At 600 degree F , it discoloured in 15 minutes as I was told . It should not be ?? ( But we heat treated in a tpyical furance ----- or we need to heat it in a oxigen controlled furance ?? )
(2) The total length extended significantly , so that each pitch having bigger space and it appears not good for EMI shielding purpose .
To answer metman , yes ! After heat treament , it looks like a typical compression spring !!! And its diameter didn't change noticablly .
Anyway , its looks " negative pitch idea " may be one of the answer , but I need to know more about it .
Thanks ,
RE: BeCu extension spring
You might want to try aging in a vacuum furnace but you still might get some discoloration. I don't think Hydrogen atmosphere would help much at 600F. Another option is to bright dip after aging.
RE: BeCu extension spring
What is Bright dip ?
Thanks ,
RE: BeCu extension spring
Added to my posts in the spring engineering forum I would like to ask why did you choose the BeCu alloy? If it is for electrical conductivity, then there are many other copper alloy spring wires which may do the job. Unless you have specific requirement for force/deflection from the garter spring that dictates BeCu alloy I do not see any reason to use it. More than that if the force/deflection requirements are known there is a possibility to use the BeCu wire in the 3/4 hard or full hard without the need for heat treatment.
The spring properties can be calculated, so why are you using trial and error method to make one with correct length. Even if you will succeed you will not have any idea about the stresses, relaxation, life cycle, etc.
If your spring manufacturer can not do the calculations for you why not seek a professional help?
RE: BeCu extension spring
Thanks to your advise .
BeCu alloy is the spec that customer want .
I am using BeCu 4/3H and it is less flexible before heat treatment , I mean not much spring effect .
And using this Forums , I find a lot of help and can refreash my engineering knowledge after my graduation 20 years + ago .
Thanks ,
RE: BeCu extension spring
RE: BeCu extension spring
Thanks to your advise .
After this project , if I still have time , I will review the calculation matter that may be further interest to me .
RE: BeCu extension spring
RE: BeCu extension spring
As a wise guy said: "There is always not enough time to do the design job correctly, but there is all the time in the world to (try) to fix a bad designed job".
RE: BeCu extension spring
Our vendor confirm today that they can make it next week .
Thanks to all of you provided help whole heartly .
Thanks again .
JohnPP