I found a glossary of forgings at https://www.forging.org/glossary-forging-terms

Flow lines Patterns in a forging resulting from the elongation of nonhomogeneous constituents and the grain structure of the material in the direction of working during forging; usually revealed by macroetching. See also Grain Flow.

I think today "nonhomogenous" means "dirty" metal. Modern chromoly alloys and specialty steels are often vacuum-arc-electro melt and often vacuum-arc-electro re-melt (more than one melt, often with a trimming of the ends of the ingots to remove impurities prior to remelt), which efficiently homogenizes any intended constituents and removes unintended constituents/impurites.

Some reference info.
http://en.wikipedia.org/wiki/Electric_arc_furnace

http://en.wikipedia.org/wiki/Vacuum_arc_remelting

Last edited by Chuck H; 05/21/13 03:37 PM.