Steels and treating

[kostas tamb/is]

Hi everybody. Well I need help understanding what steels take what treatment, please help. If I understand correctly the high carbon, non stainless steels take differential treatment and cryo treatment to improve hardness while the stainless just take normal heat treating? Or is it that some stainless can also be differentially treated? And which ones? And when all is said and done, what IS the normal heat treatment? Help me sort the confusion!

 

[Cliff Stamp]

Very basically, common cutlery steel heat treating consists of three basic steps :

1) heat to a critical high temperature (SOAK)

2) cool very quickly to a low temperature (QUENCH)

3) reheat to an intermediate temperature (TEMPERING)

The times and temperature for each depends on the steels used.

Deep cryo is used simply as part of the quench to extend the temperature lower than room temperature.

Differential heat treating can be done in two basic ways :

1) do the above to just the edge

2) do the above to the whole blade and then draw the back (heat it up) while keeping the edge cool

This is for martensite hardening, there is also bainite hardening which is rare but is basically :

1) heat to some high temperature

2) cool to an intermediate temperature and hold

-Cliff

 

[nhamilto40]

Cliff basicly covered it but here is some more detail on differential hardening.

Case #1 in Cliff's list:

As a practical matter only steels that require a fast quench (say a water or oil quench vs. air cooling) can be differntially quenched. The technical term for this is "low hardenability" (meaning the steel requires rapid cooling to form martensite). Hardenablity is independent from the potential hardness of the heat treated steel. Some common examples of steel with low hardenability are the 10xx and 52xxx series, O1, W1, traditional jap steels, etc.

Case #2:

Any of the common steels can be differntially tempered by heating the spine while keeping the edge cool. In practice you typically only see examples in carbon steels since these are prefered by the same "heat and beat" crowd that typically use this technique.