Calgary Jeep Association

4x4 Related Groups => Tech Talk => Topic started by: dunl on November 05, 2006, 03:50:29 PM

Title: fire damage to bumpers
Post by: dunl on November 05, 2006, 03:50:29 PM
Structurally, how would heat affect the strength of a set of custom bumpers - specifically, ones in a burn vehicle with their powder coating toasted right off them?

I have an opportunity to get a set from a vehicle that burnt, but wondered about the strength of them.  I'm assuming seeing as steel is made with heat, they should be okay?
Title: fire damage to bumpers
Post by: JohnB on November 05, 2006, 03:59:15 PM
Assuming it is a steel bumper, it can't be hurt by heat.
Title: fire damage to bumpers
Post by: FiEND on November 05, 2006, 04:18:51 PM
it may be better off after the fire, i wouldn't hesitate at all
Title: fire damage to bumpers
Post by: gsxtacy on November 05, 2006, 06:11:34 PM
it depends how hot the fire was... if it got toasty enough, the bumper may very well shatter if the fire crew hosed it off... brittle because the grain structure froze...it was quenched, like quenching a weld...never do it...

if the fire got to above 750 degrees celsius, the recrystallization temperature for steel, don't buy them...if it didn't then go for it.
Title: fire damage to bumpers
Post by: JohnB on November 05, 2006, 07:47:04 PM
No it won't.  Low carbon mild steel is not hardenable via quenching.
Title: fire damage to bumpers
Post by: gsxtacy on November 05, 2006, 08:28:54 PM
well, you'll hafta tell that to my materials technology professor...been doing that for 30 some odd years...got a doctorate (i think)....taught me everthiing i know about steels...we even quenched hardened and tempered a specimen of 3" 1018 barstock prolly lighter than the bumper...ask him...
Title: fire damage to bumpers
Post by: JohnB on November 06, 2006, 10:54:52 AM
OK, slightly hardenable, but not to the point of being brittle......

Not Shaw, BTW, what a prick....

Anywho, I have 15 years experience with designing and building real things that live well above 750 C.
Title: fire damage to bumpers
Post by: dunl on November 06, 2006, 03:56:56 PM
Quote from: "gsxtacy"

if the fire got to above 750 degrees celsius, the recrystallization temperature for steel, don't buy them...if it didn't then go for it.


So how would I know this?
Title: fire damage to bumpers
Post by: triver525 on November 06, 2006, 04:09:47 PM
Why would you want a stock bumper that you need to repaint and could be warped from heat?  Stock TJ bumpers come up for sale for dirt cheap from time to time.

EDIT - Sorry, I didn't notice the word "custom" until after.  In that case, I don't think I'd worry about it then.  I doubt a car fire would get up to any significant temperature.  If the rear is a tire carrier you may need to worry about the bearings.
Title: fire damage to bumpers
Post by: gsxtacy on November 06, 2006, 06:02:19 PM
that's what i'm sayin...as long as it didn't reach the recryst. temp, ( most likely not) you'll be ok

good luck