FED Material

Is the anyway to tell what a rail is constructed with (cromoly or mild steel) without cutting it up ?

 

Even cutting it up will not really tell you what it is made from unless you send some of the tubing to a lab for analysis.
Sonic testing is probably the best way to get an indication. If the tubing is in the .049 to .065 range it is probably moly. A mild steel car will usually be around .118 to .134 wall. These numbers are contingent to the car being built to sanctioning body specs and there are probably some "muffler moly" frames out there that are made from O too thin mild steel.

Roo

 

The only way I know of requires a small sacrificial piece. Cut a small piece of tubing heat it to cherry red, quench it, then smack it with a hammer. If it just flattens out, it's mild steel, if it breaks into several pieces it's c/m.

 

The old guys used to be able to "spark"(hit it on a snag grinder and look at the color and shape of the sparks) steel to tell what kind it was.
If you spark a known piece of chromoly and compare it to the frame spark.

 

I was at an NHRA chassis tech event once years ago. I watched the tech guy sonic test some frames/cages. He told me that if the sonic test reveals a certain range of wall thickness, then it was chromoly ... if the sonic test revealed a different range (thicker) is was mild steel. At this point I asked the obvious (and the question you are asking now) ... "Your test only determines the wall thickness NOT the type of material used ... how can you be sure the builder didn't 'cheap out' and use thin wall mild steel?". The reason I asked this was because I had met a couple of guys (years prior) at my metal/tubing supply place that admitted they were buying "thinner than legal" tubing for a roundy-round car in order to save weight.

Now, keep in mind, this happened a long time ago ... but as far as I can remember, the anwer given to me was that there is some kind of acid test that will determine (based on the acids reaction) whether the tubing is chromoly or mild. So, although my answer is quite vague, there actually IS a test that can be preformed. I would suggest contacting the NHRA for further/better info.

 

Last time I had a car NHRA certified they did a small acid test on two of the tubes, a certified tech may do this for you.

 

I asked the question because I looked at a chassis and the owner did not know what it was constructed of. The chassis has changed hands a few times and the information has been lost.

 

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <wunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> I found this short article about acid testing for chrome moly from the “Off-Road.com” site.

http://forums.off-road.com/jeep-short-wheelbase/188353-how-do-you-tell-if-its-crome-moly.html

“There is an acid test to determine the percent chromium in steels. You need a drop of concentrated nitric acid, 47% nitric acid and 35% nitric acid. When placing one drop of each of these, the reaction of each indicates the chromium content.

0.1% chrome has a vigorous reaction from all three.
5% chrome has no reaction with the concentrated, turns dark brown then becomes clear with the 47%, and the 35% turns the spot dark brown.
12% chrome has no reaction from any of the solutions.

The intermediate chrome contents have varying reactions.

To determine the molybdenum content, a drop of 10% nitric acid is placed on a piece of filter paper and placed in contact with the metal. A 6-volt battery is then connected across the metal and filter paper. The color of the paper after several more steps and solutions indicates that the metal contains 'Moly'.”

Also, this site has some interesting info on acid testing for other metals too, from an old Popular Science magazine.

http://books.google.ca/books?id=vSY...&resnum=2&ved=0CCAQ6AEwAQ#v=onepage&q&f=false
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