Why are forged blades dipped in oil?

Parts made of low-carbon steel and low-hardenability alloys quench better in fast oils. Hot oils are kept at much higher temperatures and are used to ensure that a part's core temperature and surface temperature do not vary too greatly during a quench. This controls distortion and reduces the risk of cracking.

Why do people quench blades 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.

Why are forged knives quenched in oil?

High hardenability steels can be quenched in slower oils to minimize the chances of warping and cracking. However, quenching high hardenability steels in a fast oil is still possible and it doesn't mean reduced toughness.

Why do blacksmiths dip in oil?

Oil is a third traditional quenching agent, suitable for high-speed steels and oil-hardened steels, and in fact for any steel for which the required degree of hardness is achievable. Oil has a slower rate of cooling compared to either water or brine, but faster than air, making it an intermediate quench.

Why do you dip hot metal in oil?

Hot Oils. Hot oils are always used at high temperatures and prevents temperature variations during the quenching process, which protects the metal against defects, cracks, and distortions.

STEEL HEAT TREATING CLOSEUP - WATER VS OIL [Trollsky Knifemaking]

What did medieval blacksmiths quench their blades in?

The smith then heats the metal so that both the iron and steel are molten and join. The blade is tempered—transformed from soft, workable metal into a hard blade—by holding the blade over a fire and then quenching the blade in a vat of oil or brine.

Why do blacksmiths quench in water?

In materials science, quenching is the rapid cooling of a workpiece in water, oil or air to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such as phase transformations, from occurring.

Is water or oil better for quenching?

Water-quenched steels will generally be harder than oil-quenched steels. This is mainly because the thermal conductivity of water is higher than the thermal conductivity of most oils (that I know); consequently, the rates of cooling will be less rapid (or lower) in oils compared with water.

What happens if you don't quench steel?

A misstep in any part of the process could lead to unsuitable steel.

Can you quench a blade in motor oil?

Motor oils are a common type of quenching oil used in both blacksmithing and bladesmithing applications. New and used motor oils can be used for quenching and are both widely available. New motor oil is typically cheaper to use than commercial quenching oils.

How long does quench oil last?

Oil Recovery

Quenching and martempering oils deteriorate during use, although most premium quenching oils can last more than 10 years when given reasonable use and care.

Can you reuse quenching oil?

Usually, the post-quench washer is used to recover the quench oil for reuse. This washer must only be used to clean parts after the quench and must not be contaminated with other coolants or other contaminants. In this process, the oil is recovered from the post-quench wash and segregated to a separate tank.

Why does a blade warp when quenched?

When these heated parts are quenched, their internal crystal structure changes again, and that volume change is not necessarily sufficient to offset the change upon heating. This change of volume can cause dimensional distortion.

Can you quench a blade in mercury?

In order to quench your sword in mercury, you need to displace more than one and a half times its own weight in mercury - and you need to put a corresponding amount of pressure on the blade. However, quenching is done while the metal is still hot and partially malleable.

Does quenching make metal brittle?

Quenching results in a metal that is very hard but also brittle. Gently heating a hardened metal and allowing it to cool slowly will produce a metal that is still hard but also less brittle.

What is the purpose of tempering after quench hardening?

After the material has been quenched to its hardest state, the process of tempering is used to achieve greater toughness and ductility by decreasing hardness. Tempering is achieved by heating the quenched material to below the critical point for a set period of time, then allowing it to cool in still air.

What temperature should you quench a knife at?

Step 2: Quench

(The block ensures that both sides of the blade are evenly cooled.) Many knifemakers recommend using canola oil heated to around 130℉, saying that water tends to cool the steel too quickly, which can lead to cracking, especially if the blade is on the thin side.

Can you over temper steel?

While you can definitely over-temper a blade, that will leave it too soft rather than too brittle; you can also over-harden (or, rather, under-temper) it, which will leave it very hard and very brittle.

Why is water quenched steel harder?

Depending on the carbon content and alloying elements of the steel, it can get left with a harder, more brittle microstructure, such as martensite or bainite, when it undergoes the quench hardening process. These microstructures result in increased strength and hardness for the steel.

Can you oil harden mild steel?

One way to do this is to make the steel red-hot, then plunge it into motor oil. The carbon in the motor oil bonds with the top layer of red-hot steel molecules and forms a tough outer covering on the steel. One last step is necessary, however, before your hardened steel is ready to work with.

Why is quenched steel harder?

If the metal is quenched, however, the alloying metals are trapped within the crystal grains which makes them harder. The precipitates also reduce the movement of dislocations which contributes to the hardness of the material.

How do you make steel harder but not brittle?

To make steel harder, it must be heated to very high temperatures. The final result of exactly how hard the steel becomes depends on the amount of carbon present in the metal. Only steel that is high in carbon can be hardened and tempered.

Can you forge rebar?

Cons of Forging with Rebar

A first major con of using rebar for blacksmithing is its unpredictable nature. Most rebar is not made of quality metals and can even contain dangerous fumes when worked. What is this? You can never be sure what the rebar is made of, so final projects can end up brittle.

What happens if you pour cold water on a hot metal?

If you add cold water to a hot pan, the temperature in the metal drops locally (where the water touches the metal) and since metal extend with heat, cooling them down contracts them.