What Are the Differences Between 440 Stainless Steel & Normal Stainless Steel?

Five Types

Austentic stainless is non-magnetic and contains nickel in the alloy, improving the heat resistance and ability to be rolled into flat sheets. Ferritic stainless is the least expensive to produce and may be considered "normal" stainless with a simple iron-chromium alloy. Martensitic stainless can be heat-treated to make it very hard, and it has a higher carbon content than regular stainless. The chromium percentage is also higher than normal stainless which further improves corrosion resistance. Duplex stainless is magnetic with a very high portion of chromium compared to ferritic stainless at 21 to 26 percent. They are specially formulated for their ability to resist crushing or pulling stresses. Precipitation hardening steels are designed to be easy to manipulate at lower temperatures compared to other types of stainless. This alloy contains chromium, nickel and molybdenum.

440-designated stainless is available in types 440A, 440B ad 440C. All three are martensitic stainless which has been heat-treated. The alloy contains iron, chromium and carbon. 440-type is often called knife stainless since it is widely used to make cutlery.

440-stainless contains carbon which provides hardness, making it a good metal for knives. The A variety has the least carbon at about .75 percent, while 440C has about 1.2 percent carbon and the B version is in between at 0.9 percent. 440A's lower carbon count makes it the softest of the three 440 types. This means it won't hold an edge as well. All three versions of 440-stainless is tempered at 600 degrees Fahrenheit. The tempering allows the metal to remain hard while flexing instead of breaking during use. 440C is the highest quality of the three versions and it used in higher-quality knives as well as valves that are subject to wear. Regular stainless steel contains almost no carbon and is easily scratched. It is not used in applications where hardness is essential.

Normal stainless steel is ferritic type and is designated 409-stainless. It is the least expensive stainless steel to produce. It contains a basic alloy of iron and chromium with perhaps a little nickel. 409-stainless is commonly seen as appliance trim, on automobiles and for decorative purposes where corrosion resistance and a shiny appearance are desired.

Regular stainless steel is known as 409 or 430 stainless. It is a basic iron-chromium alloy which is rust resistant but quite soft. It cannot be hardened and is normally used for decorative or low-impact functions. 440-type stainless is more expensive to make. It has carbon added to make it very hard and it is tempered so it will flex without breaking. It is widely used for knives along with items like valves which need wear-resistant properties.