Ray,
The head is 1018 (mild steel, low carbon if you will), but I split evenly along the edge creating two flaps that are opened to hold the high carbon "bit" that will eventually take the hardening and draw back. The high carbon bit is inserted and the blade is heated to low red, tapped to close it together, brushed, fluxed and brought to welding heat. Then it is hammered together and forged to the refined shape and treated as if the whole head is high carbon, but the only part that hardens is the edge.
I am happy with the weld, you cant even see it, unless you have the right light. Lin