Burnt car... metal condition?

venomous

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I recently purchased a 5 seater sandcar that had been in a pretty serious fire (fuel tank caught on fire) can anyone chime in on the condition of the chassis. It was a tig welded 4130 chassis and it burnt pretty bad. It burnt off the powder coating and then sat outside for 6 months and rusted too. any input would be greatly appreciated.
 

partybarge_pilot

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You now have a stress relived chassis.......

The heat probably didn't do any harm. How they put the fire out on the other hand might have. Was it put out with extinguishers or water?
 

Brian Mapes

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My opinion is that there can be two results to this. The first being take the car and check for it straigtness. Get it back straight in line like new. Then check for cracks, repair or replace all places with cracks or problem areas. Add any and all gussets and tube, or mods you want to do now. Then take it to a heat treat shop and have them stress relieve/heat treat it back to 4130 N properties. The other result is that if the fire got too hot it is possible that some of the alloying elements have been burnt out. No amount of heat treat will put those back in. If everything goes as planned like I first mentioned your car will be good as new. If it was put out with water, yes it will make it brittle, but a proper reheat treat should take care of that.
 

DUMP!

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My opinion is that there can be two results to this. The first being take the car and check for it straigtness. Get it back straight in line like new. Then check for cracks, repair or replace all places with cracks or problem areas. Add any and all gussets and tube, or mods you want to do now. Then take it to a heat treat shop and have them stress relieve/heat treat it back to 4130 N properties. The other result is that if the fire got too hot it is possible that some of the alloying elements have been burnt out. No amount of heat treat will put those back in. If everything goes as planned like I first mentioned your car will be good as new. If it was put out with water, yes it will make it brittle, but a proper reheat treat should take care of that.
Those are nice suggestions BUT,,,,,,,,,,,,, I don't know of any heat treater in the western United States that is going to have a quench tank big enough to heat treat a complete chassis. Stress relieve, on the other hand, does not require the quench process and the fire has already done that to a certain extent.

The only thing you will need to worry about is how they put out the fire. If they used water as stated above that could be bad, but if this is only a play car and you plan to act responsably then it should be fine. If your going to get stupid with the car, maybe take out some life insurance on you and your passengers.:D:D

Dump
 

venomous

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thanks for the help guys, but I'm still not sure how to handle this. maybe some more info on my part will help..... I do not believe that the fire was put out at all (other than throwing sand at it.) the chassis is all still perfectly straight but you can tell upon examination that the metal was cooked to the point that the alloys were cooked out and left it very rough and rusty. sand blasting knocks it all off and it looks good but I'm scared to death to take my family out in it. It is just a play car but will be driven pretty hard (it is a v8 long travel car made to go fast) any input or experience would be greatly appreciated.
 

odtodd1az

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If it's making you nervous, the only real solution is pick the worst parts of the heat affected zone and rebuild these areas with new tube. reinspect the chassis for cracking and square. drill some small holes in inconspicuous places and look inside the tubes to see if they still look right or are they an interesting shade of blue.
Just my .02
 

scottm

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I dont think it will be a problem. The upper transformation temp of 4130 is over 1400° F, which is bright red hot. And to fully austenize the steel to achieve annealing, hardening or normalizing, it has to be held at 1500 for 15 minutes or more before cooling. There is very little chance you have lost alloy elements, so the rust you see is probably due to completely burning off all traces of paint and oil. As said before, make any repairs or mods now, and have it normalized. There are lots of shops that can normalize a chassis. Normalizing is a heat treating process where it is heated to 1500, then allowed to air cool. It generates a yield of about 80,000 psi, which is twice as high as a full anneal. Water quenching is required to reach max hardness of 130,000 - 200,000 psi or more, and Dump is right that there are no quench tanks that big. Water quenching can result in distortion and cracks, plus it still needs to be tempered after to reduce brittleness. That is exactly why 4130 was designed to develop decent properties with normalizing. Being in the fire is not the same as proper normalizing.
 

venomous

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Thanks everyone for your advice!!!! with things like this I feel a lot better when I can get several people's opinions before moving forward. After taking everything into consideration I feel that the chassis if more than fine. I removed a few sections that I thought were the most questionable and they were fine. I put the tube into a vice and beat the *&^*&^ out of it to see how it would react and it seemed no different than any other 4130 tube I've dealt with. Most of the "excretions" I was refering to seems to have been exactly as Scott said "burnt off powdercoat" Armed with this information and feeling comfortable about it, I'm am proceeding forward with some minor redesigns and gusseting then it will be off to the powdercoater. Thanks to everyone. Gary
 

Brian Mapes

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My last little bit I want to put is it to maybe first before doing anything depending on your budget, the way I would do it is. 1. First I would get the chassis sandblasted 2. Have it professionally Crack checked or do it yourself with one of the few NDT processes 3. Then get all your cracks replaced and replace and bent, distorted or just and changes. Gusset the hell out of it as well. 4. The proceed with all your heat treating and stress relieveing process. I believe I said this stuff earlier but it sounds like what you got could turn out to be a nice car for possibly considerably less money. Just giving you my 2 cents in hopes that you get the chassis done properly to ensure yours and everyone elses safety and fun. You definatly need to post up some pictures or it now all burned up and also progress pics all the way through so we can see what the car looks like. I would def. like to see pics if thats alright. Good Luck
 
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