TEACHING/SHARING/SUGGESTION MOMENT:
IF you can do it this way.....weld your mild steel body together first. Then, get a localized heat in the eye area and drift it to shape. Anneal the entire piece, the carefully cut what will be the cutting edge on a band saw to about 1/2"-34" depth. Create a "bit" of 1080 or 1084 steel of 3/16'-1/4" thickness. (this is where it's best to create a straight edge on the body....and AFTER the bit is forge welded in, forge the edge to a radius.) If you've made a radius edge on the body...... forge the bit to the shape of the edge, and scarf down the back edge....and maybe even "sharpen" it on the grinder.
NOTE: I would discourage using 1095 or higher carbon content for the edge/bit..... since the higher the carbon content, the lower the forge welding temp..... it's very possible that you will "burn" the high carbon bit before the A36 gets to it's welding temp.
Heat the body to near welding heat, and using a hot chisel, GENTLY open of the band saw cut, until it will accept the high carbon bit you make. Flux it, and insert the bit....tap in down until the back edge "cuts" into the back of the split.......this is normally where cold shuts occur if don't "jam" the bit into the back of the cut) Quickly tap down the sides or the cut, and into the forge.....once you get to welding heat, your FIRST hit should be straight down on the edge.....setting the back of the bit into the body.....then working from the back of the bit, LIGHT hammer blows until you have the weld completed.....which will likely take a few heats. Since you've forge welded a bit in there.....it's in your best interest to do any/all additional forge work at welding heat....it will keep things together and prevent cold shuts.
A tip on heat treating: Since the body is mild steel (I'm assuming A36 hot roll) there could be any number of alloys present, and if you heat treat the entire item....it's very likely you will get at the very least hard and soft spots all over, which also means significant warping. May advice on this type of construction it to heat treat only that portion where you've welding the high carbon bit in place...... no soaking....just get that area to the austinizing temp of the high carbon steel, and get it quenched.....the more you allow it to soak, the more like you are to "pop" the forge weld.