Stainless Steel

[nightfighter]

Many times on forums like this someone will use the words "stainless steel" as if it were a single alloy. Just for those who may not know, there are more than thirty types of "stainless steel" listed in the book: Metals and how to weld them.

Sometimes I hear incorrect things about "stainless steel". For instance, "Stainless steel is non-magnetic." The problem with this statement is that it does not take into account that there are three categories of stainless steel: Austinetic, Martinsetic, and Ferretic stainless steel. Austinetic stainless steels are non-magnetic, but Martinsetic (includes 440A, 440B, and the common knife steel 440C) and Ferretic are attracted to a magnet...touch your 440C pocket knife to a magnet and you will see.

Austinetic stanlesses are usually not used for knife steel because they can only be hardened with advanced methods of quenching. Martinsetic stanless (440C) is hardenable with normal quenching methods (oil, water).

There are two general classifications for non-stanless steels used in knives: Plain carbon (plain carbon steel means there is only iron and carbon in the steel; no significant other alloying agents; it is not used much any more) and high alloy steel. High alloy steels contain additional alloying elements other than just carbon, to add properties like abrasion resistance, hardness, toughness, etc. D2 (a die steel) and 154CM (a jet turbine steel) are such alloy steels.

Also, the names of the properties of steels are often used incorrectly. Hardness, toughness, temper, drawing, etc., all have a specific meaning and should not be used interchangeable. For instance, hardness and toughness are two differant properties. With plain carbon steel, it is hardened then some of the hardness is given up for toughness. If it were left hard, it could not be sharpened with a file and it would be to brittle...it could snap in two if it were be subjected to side-pressure.

Just a little info FYI.
Thanks.