Chrome Moly or 1020 grade tubing?

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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
Reply: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....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.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.
Reply: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.Buy American, or don't whine when you end up on the bread line.
Reply: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
Reply: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.Have we all gone mad?
Reply: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......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.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.
Reply:One more thing..What kind of car and what does it WEIGH?That can tell alot....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.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.
Reply: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.AWS certified welding inspectorAWS certified welder
Reply: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..Some parts are missing Professional Driver on a closed course....Do not attempt.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.
Reply: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
Reply: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..Some parts are missing Professional Driver on a closed course....Do not attempt.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.
Reply: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. PeterEquipment:2  old paws2  eyes (that don't look so good)1  bad back
Reply: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.kidtigger24  They think I’m crazy, but I know better. It is not I who am crazy. It is I who am MAD!
Reply: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%20analysisThe 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.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply: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.
Reply: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
Reply: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 PropertiesUltimate Tensile Strength, psi 97,200 Yield Strength, psi 63,100 Elongation 25.5% Rockwell Hardness B92   4130 (Chrome moly) Annealed Alloy Steel Minimum PropertiesTensile Strength, psi 81,200 Yield Strength, psi 52,200 Elongation 28.2% Rockwell Hardness B82 1020Mechanical Data  Form  Round Bar Condition  Cold Drawn  Rockwell  B79 Brinnell  126Co-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply: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)  The best laid schemes ... Gang oft agley ...
Reply: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. Attached ImagesCo-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply: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
Reply:Originally Posted by jimcoltThere 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.
Reply:Originally Posted by MoonRiseHardness 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'.