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I Forge Iron

Railroad steels and what they mean?

Sam Salvati

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  • 4 years later...

I know this is a late post to this but...
Rail steels are primarily bainitic which is a structure of the steel, which is similar to hardened martensite. Bainitic steel is formed as a process of cooling and heating and has a fine non-lamellar structure, bainite commonly consists of cementite and ferric iron. The high concentration of dislocations in the ferrite present in bainite makes this ferrite harder than it normally would be, it also has a greater wear resistance. When forge welding higher carbon steels to lower carbon steels a carbon migration occures, which affects how the material inbetween the welding area will both cool and harden. You can compare this material with L-6, which is bainitic. I hope this helps at least with being able to h/t-ing.

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This is the first I've heard of bainite as a major microstructure in rail steels, so I Googled it. Apparently bainite rails are seeing use in this country now (see here and here). Interesting tidbit. But being that just about anyone here will be using old to very old scrap rail, most of what we're likely to find ourselves dealing with for quite some time will still be the typical ~0.8% C pearlitic steels that rails have been used for a long time. (The bainitic steels they're using for rails apparently are much lower in carbon than the older, pearlitic rails.)

Of course if you heat your rail to forging temps (which most of us probably don't do, fortunately), the fact that it was originally bainitic ceases to mean anything.

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  • 5 months later...

It is important to learn the difference between "specifications" such as "A36" or "A66" and "grades" such as "O1" or "L6."

A "specification" is a list of performance standards, possibly including a microstructural requirement or loose limits on composition.

A "grade" is a fairly tight limit on composition with no regard whatsoever to microstructure or performance.

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