There are many kinds and alloys of steel, but they all have one thing in common. To bring out the best in any of them requires the proper heat treatment, otherwise they do not live up to their potential, and in fact can be inferior to lesser or cheaper steels that have been properly treated.

But what exactly does it mean to heat treat any steel? First of all when the steel is first created in the molten baths of iron, alloy materials, and processing elements, it must be heated to just the right ”critical” temperature for the right amount of time, and then cooled properly depending on its content. These critical heating temperatures, rate of cooling, and method of cooling vary with the type of steel. Most of this data and methodology was arrived at by much experimentation over the years, and I think it is safe to say that today’s steels are superior to those of years past.

There are many quenching (rapid cooling) techniques to achieve hardness after the melt is complete. Some require slow air cooling, some faster cooling in oil, and some even salt water immersion I have heard.

The sinking of the Titanic is an example of improper steel being used for the intended application. Evidently the collision with an iceberg resulted in the hull plates shattering, causing far more damge than would have been caused by a similar collision today. The hull steel was probably quite hard, but far too brittle, and did not have the properly toughening elements (like Molybdenum or Nickel) which would have caused yielding, but not total failure. This also goes for the rivets used for attachment purposes. I am guessing even those plates might have done the job if they had been heat treated after manufacture.

This brings up the topic of final heat treat and tempering. When steel is first made it is often too hard to be of use. It’s hardness makes working it difficult, and it is usually too brittle. Tempering is the process of reheating below the critical temperature, and then cooling at a slower rate or in a different medium (air, water, oil,etc.).  This is very often  repeated several times with possibly different reheat temperatures and cooling rates. Cryogenic treatment is also now used for some blade steels, with further enhanced properties being claimed using this super cooling technique.

If you look at catalogs of some knife supply companies, you will find they provide specific heat treatment information for the raw blanks of blade steel they sell to makers. They also sell semi finished and polished blades that have already been properly heat treated and just need handles and final finishing and polishing.

The steels we have today are a product of a vast amount of effort and experimentation on the part of mills and users. To me, old knives are great collector items, but for using knives, we have never had a better choice of steels than today.

 One last thought.  You can purchase a knife with top quality blade steel, but you are only half there unless you know it has been properly heat treated. I think that is why many custom makers thrive today. They advertise their own heat treatment, and the users of their products have attested to their superior strength and edge holding because of their custom heat treatments, and come back to buy more.

Dr. K