When looking at metal the easy way to test it is a spark test. after doing that. I try oil first as a quench, then if it dose not get hard enough. I use a salt bath like the gunther quench, and last of all water. When you make hammers 1045 is Ok at best. 4140 through 4340 are great choices. 3" of steel is a lot to hammer for a first try. I would start out with a 1 3/4" to 2" piece first. But if you just want to go through the steps there is nothing wrong with mild steel a lot better choice then clay.