Stainless chassis building

Hello
I am enquiring about building a bespoke stainless chassis for an EV and need some educated advice please.
Basic questions being, what grades to use in the UK, go thicker or thinner than exisiting mild steel sizes and is TIG better then MIG?
Suppliers do not seem to have complete answers !!

So many questions and so little time !

Thanks in advance. EVPete

 

[MikeHalloran]

No responsible supplier is going to tell you "thicker or thinner". They will supply data on mechanical properties, e.g. yield stress, and let you compare and make your own decision. Get local help if you don't feel comfortable with that.

TIG is much slower than MIG, but better suited to delicate work. We can't tell from here which is more appropriate for you. Go to the welding supply store and buy a book, or take a course.



Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

Also, go to, e.g., Special Metals' website and snag information about preparation, welding, and post-weld processing of stainless. A lot of what is required is un-obvious.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

I am not a metal urgist, but from what I have heard, there can be a substantial loss of tensile strength or fatigue strength just beside the weld with some common grades of stainless. something to do with the molten metal cooling and crystal structure and separation of different metals in the alloy I think.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MintJulep]

If the question asked here is typical of the questions you are asking vendors it is not surprising that you are not getting detailed answers.

If you need detailed answers, ask specific questions.

 

[GregLocock]

Those who do this for a living suggest that 1010 or 1020 is a much better choice than CroMo for a spaceframe. Then you can MIG away to your heart's content.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Tmoose]

http://www.shreekumar.in/pics/viper/crack-frame.jpg

bp3.blogger.com/.../s400/Photo_091107_001.jpg

http://sleepyrides.files.wordpress.com/2008/04/cracked-frame-2.jpg

welds with concave fillets. grind/blend smooth.
Design frame so there will be minimal bending loads in individual members.

 

[berkshire]

EVPete (Visitor)
With stainless steel you have a large increase in cost without a lot of benefit in increased strength.
In the UK you still have to deal with salt on the roads in the winter. So while stainless will give you a benefit it is not as much as you think. EN58J stands salt a little better than EN58.
A mild steel or low alloy steel chassis, painted and undercoated will serve just as well.
Stainless UK, EN58 (304)ultimate tensile 515mpa approx yield 205mpa EN58J (316)slightly less
mild steel sae 1020 ultimate 380mpa yield 165mpa
Low alloy Sae 4130 annealed 561mpa yield 361mpa
The low alloy steel would give you a lighter chassis and can be MIG or TIG welded or Oxy Acetylene gas welded.
B.E.

 

[GregLocock]

Most spaceframes are stiffness limited, not stress limited. Most high yield steels will not be high yield after you've welded them so you need to do a post weld heat treat.

1010 or 1020 will have better ductility so will be more useful in a crash.

304 varies, some is usefully 'stainless' some might be better characterised as non magnetic steel.

Typically spaceframes rust from the inside out.

Whoever is signing off your vehicle for road use may have opinions or regulations governing the choice of steel.

That's everything I can remember.


Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.