Hi weldguy,

If you have access, check out Volume 4 , Metals and Their Weldability, of The Welding Handbook. Chapter 3 is Tool and Die Steels. The twenty page chapter covers a general description, metallurgy, heat treatment, arc welding, flash and friction welding, brazing, and safe practices. Another good source of information is welding guru Ed Craig's site. The link below is to the tool steel section.

http://www.weldreality.com/ToolstlsD.htm