My books University reference Thomas Nizolek said about using 1/4 inch thick sectrions
When we forge weld steels together, the carbon content in any layer of steel will equalize with that of the surrounding layers of steel very quickly. In Pennsylvanian, February 2009, Laboratory testing was made on a forge welded billet made from 4 alternating bars of W2 and 203E. This examination was done with an electron microscope. In the four layer sample it is evident, based on the pearlite gradient between the layers, that extensive carbon diffusion occurred after the first weld course. Drawn out and folded, the eight-layer sample showed that the pearlite concentration has almost equalized, however ferrite still decorates the prior-austenitic grain boundaries in the 203E layer. By the time the material has reached 16 layers, the carbon content of the sample appears to be uniform.