Steel testing to ID comp

[Cat Whisperer]

SO, looking to a different approach, what are the chemical tests that would indicate aloying metals or the absence of them?

(that is, a test that would not require taking a slice off the old block)

[GGaskill]

1018 has insufficient carbon to harden from heat treating.  Usually you need at least "40 points" of carbon (.40%) although 30 points will harden some.  The extra elements cause the hardening to take place deeper in a section; because you can only get rid of the heat at the surface, it is difficult to get plain carbon steels harder (stronger) in the interior portions of thick sections.  Elements like molybdenum allow deeper hardening through some process that I am not familiar with.

Low carbon alloys can be case hardened by diffusing additional carbon into the surface regions through various methods, followed by a quench.  Only the surface is hard but for certain applications (primarily to resist wear), that is all that is needed.

[GGaskill]

... (that is, a test that would not require taking a slice off the old block)

All chemical tests I am familiar with would require dissolving a small sample in solvents (probably acids) and doing various precipitations.  The sample could be done with a file but some metal would have to be collected.

[Cat Whisperer]

OK, duh, you're right it's the carbon content (hardenability) - how could I forget the obvious?

How hard is it now?  Rough gauging would simply involve a file.  I have a hand-held rockwell hardness tester that could be used on a 1/4" thick sample.

[dan610324]

its the carbon content that decide if you can harden it or not
you can even harden extreme low carbon steel
just cower it in carbon and heat it for a few days and the carbon will penetrate the low carbon steel 0,5 - 1 mm deep
then you can give it a surface hardening with a soft center

[Double D]

Weldability is a bigger concern for me than hardenablility

[seacoastartillery]

     Sometimes when we try to solve multi-faceted problems such as this one, we need to know certain bits of information that have we have not been privy to thus far.

     For instance,  would you be open, as we are, on occasion, to some scrap yard, mystery metal, if the piece is to be, #1 for your own use and, #2 for a low pressure mortar configuration like a golfball or pop can mortar?

    If this material is truly from a scrap yard, you must use a little logic to reduce your risk and also to indicate important characteristics such as weldability. 

     You must ask yourself, what types of metal go to a scrap yard, brand new surplus or used metal as in the case of the machined shafting, such as you described.  If the scrap yard you are familiar with buys, as most do, better than 90% used steel, then it is logical to deduce that whatever hardening via heat treatment the piece has will be evident in the piece which drew your attention.  Conversely, if by simple field testing described next, you find that the metal is unhardened or 'soft', then it is almost certainly a piece of low carbon steel with good welding characteristics.  A simple file test will tell you if the piece is soft, indicating a low carbon, non-hardened metal like 1010, 1018 or 1020 or 1026 steel.  The same test will indicate a hardened shaft of alloy steel.  Reduced to the basics, does the file 'bite' with moderate pressure or does it 'skate' off the round?

     Low carbon steel and good weldability is indicated by the file 'biting'.  High carbon as in spring steel or, more likely, a hardened alloy steel shafting is indicated by the file 'skating' off the round's surface. 

     We build almost all our fixtures out of 'used' steel and some have to take lots of punishment.  None have failed yet and we really relish our frequent forays into two favorite scrap yards which we have prowled for the last 35 years.  We are graduates of the school of Scrap Yard Metallurgy taught by crusty owners who only reveal their practical metal identification methods after they know and trust you.   

Good luck, Double D.  The truth is this:  You don't need no stinkin, expensive lab tests to determine if that steel is suitable or not.   A simple file will do.

Tracy and Mike