Besides knives and engineering, I have interests in guns and cars. I've read many times that S&W forged frames are stronger than Ruger cast frames. I've also read that certain forged car engine parts are superior to cast parts. But I've also read that a forged knife is no better than a cast steel knife. So I don't know how to correlate what appears to be a discrepancy.
Oh yes, that would definitely be true. A forged knife would almost always be better than a
cast knife. Probably by a lot. But we are not working with cast steel. It is not remotely "as cast".
The reduction done by the steel mill, with precisely controlled temperatures and carefully calibrated cross rolling process is vastly superior to taking that bar of steel and whacking it with a hammer. It would take a very skilled smith to not reduce the quality of the steel by forging it unless they were starting with poor steel to start with. There are some highly skilled smiths making outstanding knives. But, as a rule, even a monkey such as myself can take modern high quality commercially produced steel and, using a stock removal method, usually make a better knife than even the best smith could hope to achieve with just a hammer and a forge. I'm sure that's bound to ruffle some feathers but I've been around the block a few times, I've done my homework, it's the truth.
That's not to say there can't be some benefit to the forging process. But it's not the squashing with the hammer that is of benefit. The thermocycles actually can be. But that is not an issue with forging technique, as much as a side effect of the forging process and the descending heats that a competent smith will employ that can, under ideal conditions, create a finer grain and, more importantly, an even grain that gives a consistent and uniform heat treat response
But that has nothing to do with a hammer. That's actually just heat and temperature control. Which, again, is not well done in a forge compared to a commercial oven.
One weakness of any steel is having a homogeneous microstructure going into heat treat. Areas that have been subjected to higher heats will tend to have coarser grain. And areas of fine grain will actually process differently than areas with coarse grain. Not just grain size either, but the extent of the spheroidization can be affected by what part of the sheet you're working from or where it came from the stack and this can affect heat treat response.
A big problem with forged knives is a forge heat treat frequently overheats the tip. A tip that has been burned repeatedly during the forging process.
A big problem with stock removal knives is the highly spheroidized microstructure and the inconsistent microstructure creates a different heat treat response in different areas of the knife that were cut from different areas of the sheet. This can be significant with some steels.
High-end steels usually have very tight temperature controls, but not always. And you can have very expensive steel come from a steel mill where the edge of the sheet was rolled under temperature and have intra granular interstitial cracking (all the king's horses and all the kings men are not putting that Humpty Dumpty back together again) and not even realize it. Like anything, it is not always black and white. But, as a rule, the notion that forging a blade makes a superior knife is nonsense.
I honestly am not on this thread to promote myself. But, this is a sword that we made for a cutting competition TV show that demonstrates the insane durability capable with modern high-end metallurgy and heat treat. Forged historical swords would have been destroyed many times over attempting these things
