A BULLET POINTS MEMO TO HELP ANYONE JUST STARTING OUT IN BLACKSMITH WORK:
STEEL AND ITS USES FOR KNIFE MAKING:
Modern wrought Iron/1018/Low carbon steel: Only use for primitive blades, blades you hang up on the wall or for props/ritual knives. Not for modern knife making. Max Hardness 42RC. However 42RC hardened steel will hold an edge for a period of time because it surface hardens a bit more than 42RC if heated in a carbon rich environment at high temperature. This is called carberizing or surface hardening. Smiths would put iron in a high temperature fire with bones and coal for a period of time to increase carbon content and is still done today in metal working. The thing I love most about 1018/Modern wrought is the ability to try these ancient techniques and see how you can use and perfect or even just understand what advantage it may have given the weapons of old . In the end a modern knife has long edge retension and iron knives had higher durability in battle but less edge rentension. Without a doubt the best material to start out with and practice technique.
Rebar: Can be worth experimenting with. For best results try Grade 60 and 75. Ultra strong material that does quench harden.
Files: Great for knives of all kinds, good high carbon steel. Forge at yellow/Bright orange to avoid cracking. Quench in oil only. Hardness roughly 58RC could go higher or lower depending. Temper 1hour 300/400 degrees.
Leaf and Coil spring steel: Great high carbon steel but has a tendency to crack in forged bellow bright orange. Oil quench only. Max hardness 58RC. Temper 1hour at 300/400.
440C Stainless steel. Forges nicely at high temperature and it quenches in oil or water. In my experience I have had no trouble heat treating this steel despite horror stories. Always temper for 1hour at 300/400 degrees.
Tool Steel: I do not recommend forging this steel as much as I recommend softening and grinding from bar stock. Heat to orange and allow to cool fully to soften. Heat treat by heating to bright red and quenching in oil. Then temper for 1hour at 300/400 degrees.
1040 Railroad spike: A fine medium carbon steel containing both the durability of iron and the hardness of high carbon steel. Quench in water, no need to temper. Max hardness is 52/56RC
KNIFE MAKING TERMS YOU NEED TO REMEMBER:
Anneal: To heat an already hardened metal back to its soft composition.
Temper: To heat a quenched blade and reduce its brittleness to a more durable state.
Quenching: To dip a blade into liquid causing the rapid removal of oxygen and close the crystal structure. (Hardening)
Hammer hardening: A technique used on bronze/Copper and low-carbon steel to increase hardness by hammering while cold.
Clinker: A waste material that gathers in your forge during the forging process.
TIPS AND TECHNIQUES:
When holding your hammer during forging it is important that you loosely grip the hammer and allow the weight to do the work. Always use a thumb over fist grip to prevent pain and damage to your arm.
When quenching your blade always insert it vertically and do not stir the liquid. This can bend the steel during the process.
Use water when quenching lower carbon steel to gain max hardness but it is best to use oil on high carbon to prevent cracking.
Always be aware of your steels color and if at yellow be extra careful not to burn or melt your steel. If your blade is sparkling its ruined.
When grinding if your blade turns black in a spot you have burned the carbon and possibly ruined the steel. Grind and cool-Grind and cool. Be patient.
Preheat all high carbon steels to red/orange and allow to cool fully before reheating and forging. This removes stress.
I hope This helps you in choosing steel and just giving you an idea of the process involved in forging not just knives but all kinds pieces.
Check out my shop for some very unique Jewelry and wrought iron pieces.