Nearly all good knives are made of harden steel be they carbon or stainless. Knives made of unharden steel will not stay sharp for any length of time and will not be very good at creating sparks with a fire steel.
Knives are made of steel that can be harden like O1 tool steel also known as ground flat stock that is widely available from most engineering suppliers like
www.cromwell.co.uk. The same steel is used in the Woodlore knives.
The steel is supplied in the annealed or soft state and can be drilled, sawn and filed. When the steel has been shaped into a knife blade, it needs to be heated to 780C-820C and quenched in oil, I use ordinary cooking oil. After it has been quenched, it is very hard, harder than a file but very brittle and will chip or break very easily. It needs to be soften slightly to make it tougher but still hard. This is the process called tempering, it can be done in a domestic oven. Blades for bushcraft use should be tempered at around 230C-250C for 2 hours, taken out and cooled and then tempered again for 2 hours at the same temperature.