Automotive Flexplate material
Automotive Flexplate material
(OP)
I'm looking for some input on material selection for a automotive flex plate. The material needs to have at least 40,000 psi yield strength, 60,000 tensile strength and 10% elongation.
I've been discussing it with a number of people and their is a debate going on. Some feel the higher the % elongation the better, along with the highest possible yield strenght. Any comments.
I have see some flexplates made from 4130 steel.
I've been discussing it with a number of people and their is a debate going on. Some feel the higher the % elongation the better, along with the highest possible yield strenght. Any comments.
I have see some flexplates made from 4130 steel.





RE: Automotive Flexplate material
Or, are you a student?
RE: Automotive Flexplate material
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Greg Locock
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RE: Automotive Flexplate material
You may also want something easily weldable. Most commercial flex plates have the starter ring gear welded to the OD of the flex plate, for cost reasons.
4130, even in a normalized condition, has TS and elongation characteristics that far exceed your requirements. There are also many commercial grades of high strength, low alloy steels (HSLA) that will meet your requirements, but at lower cost than 4130.
RE: Automotive Flexplate material
Using thicker material will improve stiffness, and thereby reduce fatigue on the part.
My experience tells me that stiffness is the major quality required to keep the ring gear in good mesh when starting.
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eng-tips, by professional engineers for professional engineers
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RE: Automotive Flexplate material
We currently use a low carbon steel, low alloy steel right now with propertes around 80k psi ts, 70k psi ys and about 21% elogation.
I would like to reduce the thickness of this material as we are at 3/16" thick.
RE: Automotive Flexplate material
RE: Automotive Flexplate material
RE: Automotive Flexplate material
Usually you have pearlite with low carbon steel, but you may have martensite with 4130. While tempered mart. can be great stuff, untempered mart. is a crack waiting to happen--even with no applied load.
Suggest you take a basic metallurgy course or two--the subject is fascinating!
RE: Automotive Flexplate material
Like metalguy says, producing a suitable welded structure in 4130 is not as straightforward as low carbon steel.
For a flexplate of 4130 material that is welded, you should assume the finished part material properties will be in a normalized condition. After welding 4130, it is good practice to stress relieve and normalize the weldment. While it is also possible to put the part through a quench and temper to increase the TS, the quench will likely cause unacceptable distortion of your flexplate.
RE: Automotive Flexplate material
Using thicker material will improve stiffness, and thereby reduce fatigue on the part."
If the flex is due to the un-meshed starter bendix pusing the ring gear axially (equal force) then the stress would generally be lower with the thicker plate.
But If the flex is due to engined/transmission misalignment then I think the stresses might be higher with the thicker part.
If thin-ness is sought for weight reduction then some expensive creative forming or sculpting or even big holes based on FEA and known failures could achieve it.
If the thin-ness is sought to directly whack down material cost then I'd kind of expect a careful analysis might be able to determine the balance point.
RE: Automotive Flexplate material