[ThomasPowers]

One of the big problems is having such a difference in forge welding temps between mild steel and high carbon, (in general a lot of the high alloy tool steels are not a good choice for this).

Another problem is that tool steels are much harder under the hammer so it's easy to shear the softer mild steel as it want to deform more.

If you are using a high alloy tool steel you may need a more aggressive flux as well.

I'm currently working on a pattern welded core with applied edge (Anglo-Saxon spearpoint); but it's all made from Wrought iron and wrought iron blister steel that I blistered. So I have it easy!