http://www.springerlink.com/content/5401q70l63544286/

They want to be able to track the product back to its metallurgy data, so the label is required to refer to the foundry that cast it and to the furnace that produced the metal.

I am not too sure about "foundry", though; in English, it normally means the place where metal castings are made. The reinforced steel, however, requires forging (and perhaps rolling) which is done in factories we call "steel mills", wich include their own foundries.

Spanish term (edited): fundición u horneado

The text appears to say "fundicion u horneado", which conflicts with the question that says "fundición y horneado". I am assuming the text is correct and that "fundición" and "horneado" are used here as synonims or alternative names for the same concept. In spanish, "número de fundición" or "número de horneado" in this context refers to a number that identifies a unique batch of steel that was produced in a ladle metallurgy furnace. The term used in english is "heat number" or, alternatively "melt number" (which refers only to the specific melt, while the heat number identifies also the furnace and the date of production)

http://wiki.answers.com/Q/What_is_the_heat_number_in_materia...
http://en.wikipedia.org/wiki/Heat_number
http://www.bart.gov/docs/STD_SPEC/BFS/BFS_2_0_Spec/STDSPEC/0...
http://www.hillsboroughcounty.org/water/resources/publicatio...
(search for heat number in these documents)