If your blade is hardened a sawzall or bandsaw won't touch it, the steel would have to be annealed (basically heating to critical and slow cooling)first.In the hardened state, the best way I have found to cut is using an abrasive disc either on a Dremel or angle grinder.Even with that you will blue the edge somewhat( meaning you lose some hardness) so cool often and cut a little outside the line and then grind back to your line when getting ready to start your bevels.
That is why I suggested buying good steel and why it's cheaper in the long run.My blade steel comes annealed and cuts easily on my metal bandsaw then after grinding I HT it and I have control over how it's HTed.Dave