Posted by Dan Shockley on Friday, April 23, 2004 at 8:31AM :
In Reply to: Maybe.... posted by Gordon on Friday, April 23, 2004 at 5:24AM :
The defining characteristic of cast iron v. steel is the amount of Carbon. Cast irons (ductile, grey, white, compacted graphite) have more carbon than steels. Though there are high carbon steels that have carbon upto the deffining line, most steels have drastically less carbon. Because of the carbon, cast iron has a much lower melting temperature. This makes it easier to cast, and therfore makes iron castings much cheaper than steel ones. The difference in Carbon content is why the spark test works. With a little practice a spark test is a terrific method of determining material weldability, etc. Anyone who spends a lot of time in the shop should find a good refernce on spark testing and practice on some known materials, so that when it is time to identify an unknown, you will be ready.
Have a great day,
Dan