¼” square stock in W2 is pressing the limits of full hardenability for even Parks #50, I have got there under some very ideal circumstances but it is pushing it. The 10F difference between 1460F and 1470F will be negligible to non-existent to grain size, vanadium is a very serious carbide requiring a lot of temp to break and it is why it was added to W2. The only real concern for going over 1475F for W2 is the possibility of retained austenite as you approach or exceed 1500F; that is why 1475F works so well.
The only true normalization was the 1650F heat, the rest were simple thermal cycles followed by a partial spheroidal anneal at 1200F. If you have differences in the two that had that last 1200F soak it is from the formation of those spheroidal carbides. Spheroidal carbide will take more effort to put into solution than fine pearlite and will cause a higher rate of pearlite formation in the quench so you could get a double whammy with leftover carbide and pearlite colonies mixed with the final martensite. This condition will cause more shear type fracturing due to plastic deformation, making the bar harder to break as well as a rougher fractured end grain. The bar without this condition will more easily break in a more brittle mode and have a smoother appearance.
The finer and more even distribution of phase/structures possible in the tougher piece, despite the fracture appearance, would be desirable, but not if it interferes with full hardness. Here is a classic example of how grain size is not always the whole story. If one pursues finer grain with no consideration to carbide conditions or phase homogeneity it is only part of the big picture. If I had to choose between a blade with pearlite colonies, retained austenite and large, uneven carbide networks that was very fined grained and the same blade that was bumped up a grain size to eliminate all those other issues, I would take the latter. Fortunately we don’t have to make those concessions and there are ways to have our cake and eat it too.
