Water-Quenching vs. Oil-Quenching

[John A Stuart]

To show why sea water is a better quenchant. Brine, which offers faster cooling than plain water, can also be used as a quenchant. Brine solutions are typically made by adding a small concentration (usually five to seven percent) of sodium chloride or calcium chloride to distilled water. Like water, it is the preferred medium for alloys with low hardenability.When steel is quenched in brine, a layer of salt is precipitated onto the metal. The salt layer disrupts the vapor jacket that forms around the metal, which helps to reduce and eliminate non-uniform heat transfer in the solution. In addition, brine permits a reduced level of agitation compared to water. Temperature is less critical for a brine system, thus reducing its importance as a variable. Brines are most commonly used with high carbon steels or parts requiring high hardness.

There are other additives that will produce similar effects, ie. caustic soda (sodium hydroxide). John

[bluboxer]

Good day everyone,

I just wanted to bring up a couple of points regarding steel composition and hardening.

I would prefer to describe tamahagane as a "simple" steel rather than "pure" in that the two significant elements are iron and carbon with some other elements as impurities existing in insignificant amounts (hopefully).Modern steels have a higher degree of purity in a sense.

As we add alloying elements like manganese,molybdenum and chromium (just to name a few) the nose of the TTT moves further away in time so we can cool at a slower and safer rate while still obtaining sufficient martensite.

 

With respect to the "hard spots" observed in gunto; I feel this is an artifact of the steel composition rather than the method of quenching.

 

I also think that nie is not an indicator of the quenching medium but of how the steel was smelted,forged and heat treated.

 

The reason that smiths chose fresh water as a quenchant was because it perfectly matched the time constraints with simple steels. If they used saltwater or seawater, as I'm sure many tried, the blade did not survive the thermal shock and if they used animal fat or vegetable oils the blades did not get hard.

 

Now on top of all that you can through some clay on the blade to make the ridge and spine cool even slower so there is little chance of martensite forming elsewhere (differential hardening).I have heard it postulated that the thin layer of clay on the ha reduces the effect of the vapor barrier that is formed and increases the local cooling rate even further.

Cheers

[Jacques D.]

Hi,

 

The yakiba is considered nioi, that is why it is often said that all swords are nioi-deki

 

 

What ?

 

Please open Nakayama's book page 91 or the craft of the Japanese sword (Y.Y.) page 92. Nioi deki or nie deki are related with habuchi not yakiba (which is mainly made of martensite and nie or

[cabowen]

Nioi-deki and nie-deki do indeed refer to the habuchi, the edge of the yakiba. The yakiba proper is in nioi (martensite too small to be seen as distinct particles) thus in a nioi-deki sword, there is no discernable difference in the martensite size between the yakiba proper and the habuchi- it is continuous nioi. Swords with nie in the habuchi are still said to have a nioi-guchi with nie. As I said, there is always nioi in every sword because the yakiba proper is made of nioi. Some have differing amounts of nie in and along the habuchi. Swords that have abundant nie are said to be done in nie-deki, but how much nie constitutes a "nie-deki" blade is not rigidly defined. All swords made of tamahagane and water quenched have some nie whereas it is nearly nonexistent in WWII Western steel, oil quenched blades. This is a key feature.

 

So, by definition, all swords are nioi based. Some have more nie in the habuchi then others. When the amount of nie becomes great (whatever that means), the sword is then said to be in nie-deki. It still has what is called a nioi-guchi. All swords have a nioi-guchi. To paraphrase Nakahara, sometimes a sword will be described as done in ko-nie-deki by one person, then another will say nioi-deki with abundant ko-nie. That is how it is....

[Jacques D.]

Hi,

 

thus in a nioi-deki sword, there is no discernable difference in the martensite size between the yakiba proper and the habuchi- it is continuous nioi

 

 

Ok Ok, i will waste my time