Chromoly v mild steel

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Hi,I have a rollcage that I neet to add some bars to. Question is - is there a simple way to determine if the existing metal is chromoly or mild steel?Thank you,L
Reply:Find someone with a handheld spectrometer or whatever those gizmos are....a guy I work for sometimes has one.  What is the rollcage in??  Unless it is in a high dollar race vehicle I`d be more willing to bet it is 1018/1020.   Even if it is 4130 you will most likely be fine welding in 1018/1020 tubes as long as you have decent welding skills. The main thing is to TIG it if possible and put some heat into the tube so it will cool slowly. You can even wrap it with a welding blanket afterward to hold the heat in.
Reply:The only way i can think of to determine that otherwise would be to test it by cutting a piece out in a section you don`t care about(IF possible) and take it to someone with a hardness tester. That would narrow it down.
Reply:Originally Posted by L5wolvesfHi,I have a rollcage that I neet to add some bars to. Question is - is there a simple way to determine if the existing metal is chromoly or mild steel?Thank you,L
Reply:Originally Posted by paulrichyes use the spark test method with a hand held grinder. if the sparks that are coming of are real fine and havethree branches.this means it is hardend chrome
Reply:Thanks guys - BTW it is in an off road race car.L
Reply:Ummm, chrome and chromoly are not the same thing...Mechanical Engineer
Reply:Originally Posted by BLUE2KSSUmmm, chrome and chromoly are not the same thing...
Reply:Quick guidehttp://en.wikipedia.org/wiki/Spark_testingIt is pretty cool to actually see the different Sparks generated- Low light in the Shop will help with defining the Sparks.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Chromemoly is lighter in weight than mild steel.JasonLincoln Idealarc 250 stick/tigThermal Dynamics Cutmaster 52Miller Bobcat 250Torchmate CNC tableThermal Arc Hefty 2Ironworkers Local 720
Reply:Originally Posted by snoeproeChromemoly is lighter in weight than mild steel.
Reply:That spark chart on Wikipedia kind of reminds me of when I tried to decide if something was cast iron or mild steel with the spark test. All my sparks looked like all of them to my newbie eyes! I also remember taking Geology in college. The instructor gave us a bunch of samples of various minerals. All were quite distinct and labeled. Then, when he brought out the test tray nothing was quite as distinct as the text book samples.Lincoln 175HD Miller AC/DC ThunderboltSmith AW1, Dillion (Henrob) Mark III, & Smith LittleTorch
Reply:>>Chromemoly is lighter in weight than mild steel>Chromemoly is lighter in weight than mild steel<<Chromoly (CM) has a much higher strength than Mild Steel (MS), therefore thinner wall CM tubing (for example) can be used to provide a similar strength that would require a much thicker MS tubing thickness.Now, if you created a one inch cube of each metal (CM, and MS), that were exactly the same size/volume, I'm not sure if one would be slightly heavier than the other; if there was a difference I assume it would be marginal.However, I could be wrong, I'm not sure.Regards to all.
Reply:Originally Posted by smyrna5That spark chart on Wikipedia kind of reminds me of when I tried to decide if something was cast iron or mild steel with the spark test. All my sparks looked like all of them to my newbie eyes! I also remember taking Geology in college. The instructor gave us a bunch of samples of various minerals. All were quite distinct and labeled. Then, when he brought out the test tray nothing was quite as distinct as the text book samples.
Reply:So I'm thinking about doing some projects, bikes, trikes or other human powered vehicles.  If i was originally was planing on using 16 ga. mild steel tubing, but wanted to save some weight by going with Chromolly,  What thickness gauge of chromolly can I get away with?  18?  20?
Reply:Originally Posted by Broccoli1Most common steel to try it with is some Leaf Springs and then compare it to Mild Steel.
Reply:Originally Posted by KelvinSo, is chrome-moly considered a "high-carbon" steel?Reason I ask is, I don't see a chrome-moly steel on that Wikipedia spark test chart. Do you use the one shown for high-carbon tool steel?
Reply:Originally Posted by DavidSimTake NHRA approved/certified full tube chassis cars, normally shops use either .083 wall CM or .134 wall MS for the main cage hoop, I assume that someone figured that these were good comparison numbers "for certain types of cars/classes, but not all of course".That is to say, I wouldn't build a T/F or F/C or P/S chassis out of .134 MS and expect it to pass tech (although there are some whom believe that MS is safer than CM for race car chassis it appears from what I have been reading lately).Regards to all.
Reply:I built a 'kit' 'experimental' sailplane (started, anyway), 35 years ago, which involved welding a chrome-moly cage together. FAA inspectors would NOT allow home 'amateurs' to weld any way but ox/acet with mild rod, they claimed we could lay down 'perfect' welds which would peel off the tubing. The mild rod would form alloy with the chromoly when molten. (<-their claim) I didnt have anything but ox/acet & a miller ac thunderbolt. anyway.