I was a bit brusk in the response with hickman1.
I have had some PM discussion with him, and know a bit more about his intent.
The below info is for educational purposes only, and I do not recomend forging a knife from a HSS saw blade. One can be ground from a hardened blade, but the resulting knife will be mediocre at best.
Just to make myself clear, I think using a known steel, and making a good knife, is always a better choice than guessing at what the steel is and trying to make a so-so knife.
OK, here is the info hickman1 wanted.
HSS saw blades are complex-carbide forming steels with hyper-eutectiod high alloy chemistry. The steel is made to attain high hardness and be able to work in the temperature range of 900°F without being ruined. The trade-off is that steel is brittle.
HSS will not forge weld under normal welding techniques. It may be possible to do a canister weld, but the make-up of HSS will produce a really poor laminate, if it even works ( doubtful). This would be a very complex weld and drawing operation, as the steel is air hardening and extremely brittle, as well as very hot hard.
The only working technique option most knife makers have with HSS saw blades is to grind one out in the hardened condition.
One reason I try and avoid giving the this info on the forums is that years from now, someone will post that they made a knife following "Stacy's instructions" and it was a crappy knife. They fail to remember that I said it would most likely not make a good knife, and was advising against it.
Most power hacksaw blades are some type of HSS. The model number on this blade would indicate that it is HSS. You can guess that it is M42, M2, or similar steel a far as HT, but that is only a guess. This will require a HT oven with 2200°F capability.
People often make a simple bench knife from HSS saw blades by tempering them down and grinding them in the hardened state. The results may vary greatly, but this would be how to give it a try:
Bake in your kitchen oven at 500°F for two hours, quench in room temp water, bake for two more hours, then quench in water again. This should make the blade less prone to snapping, but the edge may still be a bit chippy if ground at too acute an angle. An included angle of 30° is about as low as you want to go.
Do the grinding with fresh belts, go slow, dip in water every few passes to prevent getting too hot. Sharpen on a bench stone, or DMT plate.
Trying to heat treat HSS without knowing the exact steel makeup is going to be a total crap shoot, but if you assume it will have a regimen similar to M42, use that as a starting point.
Here is the info on M42 and the HT data:
Typical Chemistry
Carbon 1.08%
Manganese 0.30%
Chromium 3.75%
Vanadium 1.15%
Silicon 0.30%
Tungsten 1.60%
Molybdenum 9.50%
Cobalt 8.00%
Sulfur 0.03% max.
Typical Applications
Broaches Gear Hobs
Drills Milling Cutters
End Mills Reamers
Form Tools Shaper Cutters
Annealed Hardness: BHN 235/255.
Machinability in the annealed condition is approximately 35% of W1 Tool Steel (1%C).
Thermal Treatments
Critical Temperature: 1560F(850C)
Forging: 2025-2075F(1105-1135C) Do not forge below 1700F(930C). Slow cool.
Annealing: 1600F(870C), hold 2 hours, slow cool 30F(15C)/hr max. to 1000F(540C), then air or furnace cool. Hardness BHN 235/255.
Stress-relieving (After machining): 1100-1300F(595-740C), hold 2 hrs., then air or furnace cool.
Straightening: Best done warm 400-800F(200-430C)
Hardening: (Salt, vacuum, or atmosphere).
Preheat: 1500-1550F(820-845C), equalize. A second preheat stage at 1850-1900F(1010-1040C) suggested for vacuum or atmosphere hardening.
High Heat: 2075-2175F(1135-1190C). Standard recommendation to achieve HRC 66/68 is to use 2150-2175F(1175-1190C).
Quench: Salt, oil or atmosphere quench to 1000-1100F(540-595C), equalize, then air cool to below 125F(50C) or hand warm. Vacuum or atmosphere quench rate through 1850-1300F(1010-705C) range is critical to achieve optimum heat treat response.
Temper: 1000F(540C) minimum recommended. Triple tempering required.
Stress-relieving (Hardened parts): Temper 30F(15C) below original tempering temperature or 1000F(540C) minimum.
Toughness
Lowering the hardening temperature (underhardening) reduces the grain size and increases toughness
. I really have too many irons in the fire with work, setting up my shop, moving all of my reloading gear and supplies into it, as well as keeping up with the homeplace, I had a forge body built at work, and have had the KAOwool for over a month and have not had the oportunity to line my forge, and still need to buy or build a burner for it as well. Then add in the fact that it is stoopid hot here right now... was 107 deg on my front porch yesterday @ 3pm.