What is differential hardening?

Differential hardening is a method used in heat treating swords and knives to increase the hardness of the edge without making the whole blade brittle. To achieve this, the edge is cooled faster than the spine by adding a heat insulator to the spine before quenching.

What is hardening in heat treatment?

Hardening heat treatments invariably involve heating to a sufficiently high temperature to dissolve solute-rich precipitates. The metal is then rapidly cooled to avoid reprecipitation; often this is done by quenching in water or oil.

Does tempering a sword make it stronger?

As one of the last processes in fabricating a sword is quenching and tempering it. Quenching hardens the metal so it holds an edge longer but this also makes it very brittle. To restore some ductility and durability the sword is tempered.

How do you harden a blade?

Hardening is a way of making the knife steel harder. By first heating the knife steel to between 1050 and 1090°C (1922 and 1994°F) and then quickly cooling (quenching) it, the knife steel will become much harder, but also more brittle.

What is flame hardening?

Flame hardening is a heat treatment process where oxyfuel gas flames are directly impinged onto the gear-tooth surface area to be hardened which is then subjected to quenching. It results in a hard surface layer of martensite over a softer interior core.

What is induction hardening?

Induction hardening is a process used for the surface hardening of steel and other alloy components. The parts to be heat treated are placed inside a copper coil and then heated above their transformation temperature by applying an alternating current to the coil.

Why are swords dipped in oil?

The oil in the quench tank causes the steel to cool rapidly and evenly. If the steel does not cool evenly for some reason, then the blade can warp or even fracture.

Why do blacksmiths quench in oil?

Oil is frequently used for quenching because it transfers heat very quickly and without causing significant distortions. While water-based caustic quenchants are even faster, but the severity at which they do it can distort or even crack some materials.

What do blacksmiths quench their blades in?

Blacksmiths generally use water, oil, or compressed air to quench. These substances vary in environmental impact, cost, and effects on the metal, but the best quenching medium is usually water or quenching oil.

How do you harden steel at home?

Set your steel directly on the oven rack or on a baking sheet. Let your oven heat the piece of steel. During the tempering process, the steel heats up enough to soften the alloys inside to make it less brittle. If you need to use a blow torch, focus the flame tip on the area you want hardened.