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Thread: Chrome Moly or 1020 grade tubing?

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    Chrome Moly or 1020 grade tubing?

    I have a friend that is thinking of buying a drag car.....wants to know if there is a way to determine if the roll cage is fabricated from a chrome moly (4130 grade) or a standard mild steel tubing such as 1020 grade. I have heard that there are methods that vary from grinding and identifying spark colors, to drilling with a dull drill in a piece of each material...to xray surveys and hardness tests.....any good ideas for determining this?

    Jim Colt Hypertherm

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    Re: Chrome Moly or 1020 grade tubing?

    Why can't he just ask the owner?

    Either and or moly just makes it lighter..
    You can use thinner wall tubing with moly as long as the OD is what is required..
    Most tube chassis cars now are moly.
    If you need to add tubing to keep up with rule changes you can weld moly to mild steel..
    No biggie.

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    Re: Chrome Moly or 1020 grade tubing?

    You could do a file test. give each 10 swipes. The Cromo will be a little harder than mild steel. Test it compared to a piece of mild steel pipe. Also, most 4130 is seamless. strip the paint from a section to check it out, if you don't want to cut into it.
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    Re: Chrome Moly or 1020 grade tubing?

    Zap,

    I guess the owner is not 100% sure if it is chrome moly, which is usually 4130, as opposed to 1010 mild steel. Probably is haggling on price over this subject...knowing my friend! Also....both can be seamless.....so that does not help much. I thought I had heard about a spark test....where the color of the sparks from grinding were pretty definitive....but everything I have reseached on this seems to give mixed messages on the spark test! I was thinking to use a dull 1/8" drill bit....drill a known piece of mild steel DOM tube, then drill a hole in the cage....see if it is harder to drill? Still not positive, but likely!

    Jim

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    Re: Chrome Moly or 1020 grade tubing?

    Other than the file or spark tests what about taking a piece to somewhere that has a rockwell tester? I would imagine you can unbolt at least one piece to take for testing.
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    Re: Chrome Moly or 1020 grade tubing?

    DO NOT drill or grind anywhere on this chassis..

    That will just open a can of worms once the inspectors get around to cert. the chassis..
    sn0border has the best solution so far..

    But why does all this info be needed?
    Who BUILT the car in the first place?

    There has to be a history with it..
    Is it from around here?You are in NH..I am in Mass..
    If it is a car from this area I could probably track it down...


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    Re: Chrome Moly or 1020 grade tubing?

    One more thing..
    What kind of car and what does it WEIGH?

    That can tell alot.

    ...zap!


    I am not completely insane..
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    Professional Driver on a closed course....
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    Just because I'm a dumbass don't mean that you can be too.
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    Re: Chrome Moly or 1020 grade tubing?

    I agree. Do not weld file or grind on the frame unless it is necessary and you are qualified to do so.

    Usually if you take a combination wrench and tap on a piece of 1020 steel (known for sure),
    And the tap on the chromoloy there will be a distinct ringing sound from the chromoly that is brighter that when you tap the 1020. The tubes need to be the same thickness also.

    But it is not a conclusive test.

    Better to get the history of the car. Someone knows. There has got to be more than one person involved with that car.

    BTW....Some rules have changed and chromoly is not required, and wire feed welding is approved for some classes of racing cars.
    Last edited by Donald Branscom; 01-27-2011 at 06:01 PM.
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    Re: Chrome Moly or 1020 grade tubing?

    I agree Donald but the tubing for moly can be a thinner wall thickness than mild steel..
    Same OD however..

    I was going to mention the "Tap It Test" but like you stated..
    It's inconclusive..

    ...zap!


    I am not completely insane..
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    Professional Driver on a closed course....
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    Just because I'm a dumbass don't mean that you can be too.
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    Re: Chrome Moly or 1020 grade tubing?

    The car is in Texas. I used to race stock cars on asphalt ovals in NH and Vt...we had to have an inspection hole in the main upright hoop...as they did not have the ultrasonic thickness testers back then, and we had some fools building their cages with exhaust tubing! I am quite aware of why 4130 is used...some sanctionaing bodies allow thinner walls (lighter) on the cage with this as opposed to the mild steel. Just wondering if there was an easy test....so far there does not appear to be.

    He is buying the car from the original owner, who does not seem sure about its original construction....I think it is a fox body (mustang) that runs under the time required for a full cage....so falls under some sort of rules from NHRA or IHRA.

    Jim

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    Re: Chrome Moly or 1020 grade tubing?

    Well if he buys it and wants to race at New England they went back to NHRA this year..
    There will be a divisional race there this summer..
    There is not much difference in the rules but better safe than sorry..

    ...zap!


    I am not completely insane..
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    Professional Driver on a closed course....
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    Just because I'm a dumbass don't mean that you can be too.
    So DON'T try any of this **** l do at home.

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    Re: Chrome Moly or 1020 grade tubing?

    Possibly look up rule for tube thickness requirement in that class. Get someone to ultrasound check thickness. The main reason for using moly is reduced thickness requirement (lighter weight, same or stronger than mild). I don't know anyone that would use thicker tube than required. I am guessing the tube is painted? If not look for mil spec numbers, some people pickle moly instead of paint.
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    Re: Chrome Moly or 1020 grade tubing?

    Here's a silly question, were the welds done with MIG or TIG? If it was mild steel, I would think they would most likely use MIG. I know all the NASCAR stuff is mild steel MIG welded. If it was TIG, it would most likely be chrome moly cause I thought NHRA rules state chrome moly can only be TIG welded. You could also TIG mild steel, but I think most likely use MIG. I'm sure Zap would know since he has done NHRA chassis stuff before.

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    Re: Chrome Moly or 1020 grade tubing?

    Jim,

    If the car is a big investment, have your friend find an independent lab that can do onsite, non-destructive testing. There are hand held x-ray analyzers that can give you a crude chemical analysis of the steel with just a bare patch the size of a quarter.

    This is an example of the type of equipment I'm talking about.

    http://www.bruker-axs.com/handheldpr...XRF%20analysis


    The 4130 tubing will have a significant amount of Chromium present, while mild steel tubing will contain none.

    I don't know what a lab might charge, but I'd guess no more than a couple hundred dollars and about 15-30 minutes of access to the vehicle. Results are realtime.

    If the car's expensive or the consequences of using mild steel tubing are severe, then the cost may be justified.

    Hope this helps.
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    Re: Chrome Moly or 1020 grade tubing?

    The rockwell test is really the only non destructive way to find out, shouldn't be to hard to find a place that has one of those.

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    Re: Chrome Moly or 1020 grade tubing?

    It is TIG welded, but still not definitive. There are major chassis builders doing MIG and TIG on mild steel as well as chrome moly. Both can be done properly, although TIG (once again, properly done) will provide for a stronger weld. Thanks for all the suggestions and help! Jim

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    Re: Chrome Moly or 1020 grade tubing?

    Jim if you can get a piece of the metal in question to a cnc shop that has a Rockwell Hardness tester they should be able to easily perform the test for you.

    The metals 4130 vs 1020 should approximate the following data But much will depend upon the composition of the metal. If you can locate someone with a portable Rockwell Hardness tester in the area of where the car is located they can perform the test on the car.

    4130 (Chrome moly) Normalized Alloy Steel

    Minimum Properties
    Ultimate Tensile Strength, psi 97,200
    Yield Strength, psi 63,100
    Elongation 25.5%
    Rockwell Hardness B92


    4130 (Chrome moly) Annealed Alloy Steel

    Minimum Properties
    Tensile Strength, psi 81,200
    Yield Strength, psi 52,200
    Elongation 28.2%
    Rockwell Hardness B82


    1020

    Mechanical Data


    Form
    Round Bar

    Condition
    Cold Drawn


    Rockwell
    B79

    Brinnell
    126
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    Re: Chrome Moly or 1020 grade tubing?

    To determine -what- metal is there non-destructively, you do (or have done) an X-ray spectrometry test. Just like A_DAB posted.

    Everything else is just 'could be'.

    Hardness test? You have to fit it in a machine (hardness tester) and then you end up with a 'dimple' in the metal. Not quite 'non-destructive'.

    Grind (spark test) or file? Definitely NOT non-destructive.

    Tapping on it? Non-conclusive.

    Ultrasonic thickness tester? Tells you the thickness, not the material. You might try to -infer- the material type based on the thickness, but you would be making an ASSumption. (capitalization done that way on purpose )

    Easy, definitive, and non-destructive is the X-ray spectrometry method.

    (or the build history/paperwork)
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    Re: Chrome Moly or 1020 grade tubing?

    In our cnc shop when use a ultrasonic hardness bench tester and we have a Portable Ultrasonic Hardness Tester works great for measurements out in the field where the item cannot come to the shop. Such as FAA testing on aircraft frames, tanks and sheetmetal.
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    Re: Chrome Moly or 1020 grade tubing?

    Morning Jim,

    A tool & Die shop close by or a jeweler may have some 2 or 5% nitric you can etch with. Any nickel or chrome in the material will leave a little blue or green tint behind on the surface.

    If it's a complete tubular chassis you could also just drill a hole in the tubing near the front or back where the body is mounted and check the thickness. If the wall is 3/32" or less it's prolly Cr-Mo.

    Matt

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    Re: Chrome Moly or 1020 grade tubing?

    Quote Originally Posted by jimcolt View Post
    There are major chassis builders doing MIG and TIG on mild steel as well as chrome moly. Both can be done properly, although TIG (once again, properly done) will provide for a stronger weld.
    Not to go off-topic, but is this true, and if so, why?

    I'm just a newby but it seems to me that a properly-done full-penetration weld is a properly-done full-penetration weld (assuming the same fillers are used) ... regardless of how the filler and parent metals get melted.

    What am I missing? Is a weld stronger simply because the shielding gas is straight argon (TIG) as opposed to some mix used in MIG?

    Is it an issue of having a back purge inside the tubing, as you might have with TIG?

    I just never heard that GTAW welds were inherently stronger than GMAW...and if they are, I'm curious to know why.

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    Re: Chrome Moly or 1020 grade tubing?

    Quote Originally Posted by MoonRise View Post
    Hardness test? You have to fit it in a machine (hardness tester) and then you end up with a 'dimple' in the metal. Not quite 'non-destructive'.
    Not destructive like a brinell test, a rockwell leaves an indent maybe 1/16" big. Plus, fitting something in a rockwell tester isnt exactly hard. You set the piece on the anvil and pull the handle. X-ray spectrometry would be nice but its also much harder to find those machines.
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