Making a knife out of an old diamond saw blade can be an exciting hobby or a lucrative business. It doesn't take long and it's fun, but saw blades are kind of thin to make a strong and durable knife. To make a homemade knife from a diamond saw blade, you need to perform a spark test and a hardening test. Circular saw blades are made of high-carbon steel, so technically, yes, circular saw blades are made of steel.
Steel blades are heated to between 860 and 1100 degrees Celsius, depending on the type of steel used to create the circular blade. The huge carbide-free welded ones shine like the big blades of the 15N20 wood band saw. They are hardenable and are good for knives. If the blade is difficult to maintain its sharpness, there is no need to modify the steel to turn it into a usable knife.
Instead of condemning your equipment to the junkyard, you can quickly deploy it to use for other vital tasks, such as cutting a knife into its blades. I drew the shape of the knife on thin cardboard (you can also use paper), then traced it on the saw blade with a permanent marker. In subsequent attempts, I discovered that if I first annealed the blade, I could cut it, albeit slowly, with a jig saw equipped with a metal cutting blade. The procedure is completed by cooling the blade a second time, resulting in a durable and reliable steel sheet. Therefore, you need to pay as much attention to the finish of your knife as you have put into making the blade itself. If you can visit a knife smith in your area, that would help.
Making a knife out of your old diamond saw blade can become an exciting hobby for you or a lucrative business, it all depends on your approach.