|
|
HTML clipboard Steel Element Information Carbon (C) - Increases edge retention and raises tensile strength.
- Increases hardness and improves resistance to wear and abrasion.
Chromium (CR) - Increases hardness, tensile strength, and toughness.
- Provides resistance to wear and corrosion.
Cobalt (CO) - Increases strength and hardness, and permits quenching in higher temperatures.
- Intensifies the individual effects of other elements in more complex steels.
Copper (CU) - Increases corrosion resistance.
Manganese (MN) - Increases hardenability, wear resistance, and tensile strength.
- Deoxidizes and degasifies to remove oxygen from molten metal.
- In larger quantities, increases hardness and brittleness.
Molybdenum (MO) - Increases strength, hardness, hardenability, and toughness.
- Improves machinability and resistance to corrosion.
Nickel (NI) - Adds strength and toughness
.
Nitrogen (N) - Used in place of carbon for the steel matrix. The Nitrogen atom will function in a similar manner to the carbon atom but offers unusual advantages in corrosion resistance.
Phosphorus (P) - Improves strength, machinability, and hardness.
- Creates brittleness in high concentrations.
Silicon (SI) - Increases strength.
- Deoxidizes and degasifies to remove oxygen from molten metal.
Sulfur (S) - Improves machinability when added in minute quantities.
Tungsten (W) - Adds strength, toughness, and improves hardenability.
Vanadium (V) - Increases strength, wear resistance, and increases toughness.
Steel Production And Properties The following provides a very brief overview of steel treatment and properties:
By definition, steel is a combination of iron and no more that 2% carbon. Steel is alloyed with various other elements that combine to produce special properties. Once a particular alloy1 combination (or steel type) is selected, specific procedures are used to maximize the unique qualities required for that steel to perform. Generally speaking, the process for converting a steel alloy into a premium knife steel is heat treating2.
Heat treatment is the most important stage in the evolution of an alloy into a performance knife steel. The first step in the heat treatment process is to reach a critical temperature.3 This temperature is held for a specific amount of time (depending on the steel being hardened) and causes the steel to become austenetized.4 Heat treatment is one of the many factors that determines the grain size5 of the steel (a fine grain structure is more desireable for knife blades because it improves edge retention and enhances blade finish).
Next, the steel is quenched6 to achieve its maximum level of hardness.7 At this point, the steel is too hard and brittle for practical use and thus tempering8 is of key importance in bringing the steel to its ideal hardness level (different knife steels perform best at different levels of hardness). Tempering also increases wear resistance and toughness9 properties. When tempering, it is important to understand the interaction between hardness and toughness. An increase in yield strength10 and tensile strength11 and a decrease in impact strength12 and ductility.13 An increase in toughness is usually accompanied by the opposite effect (i.e. an increase in toughness and ductility and a decrease in yield strength and tensile strength). Therefore, high-impact knifes such as swords and machetes would benefit from a softer blade (to avoid blade breakage), while low-impact knifes such as pocket knifes may benefit from a harder blade (to improve wear resistance). Once tempering is complete, the final hardness of the steel can be determined using a Rockwell Test.14
For more detailed information of the above processes and properties, we recommend the following references that were used to compile this information: Metallurgy Fundamentals by D.A. Brandt (published by Goodheart-Wilcox) and Heat Treaters Guide by P.M. Unterweiser (published by ASM).
- Alloy
- A material that is dissolved in another metal in a solid solution; a material that results when two or more elements combine in a solid solution.
- Austenetized
- The basic steel structure state in which an alloying is uniformly dissolved into iron.
- Critical Temperature
- The temperature at which steel changes its structure to austenite in preparation for hardening.
- Ductility
- The tendency of a material to stretch or plastically deform appreciably before fracturing.
- Grain Size
- The physical size of the austenite grains during austenizing. The actual size can vary due to thermal, time and forging considerations.
- Hardness
- The resistance of a steel to deformation or penetration analogous to strength.
- Heat Treating
- Heating and cooling metal to prescribed temperature and the limits for the purpose of changing the properties and behavior of the metal.
- Impact Strength
- The ability of a material to resist cracking due to a sudden force.
- Quenched Rapidly cooled from the critical temperature using water, oil, air or other means.
- Rockwell Test
- A measurement of steel hardness based on the depth of penetration of a small diamond cone pressed into the steel under a constant load.
- Tempering
- Reheating to a lower temperature after quenching for the purpose of slightly softening the steel, precipitating carbides, stress relieving.
- Tensile Strength
- Indicated by the force at which a material breaks due to stretching.
- Toughness
- The ability of a material to resist shock or impact.
- Yield Strength
- The point at which a steel becomes permanently deformed; the point at which the linear relationship of stress to strain changes on a Stress/Strain curve.
|
 |
| This article was published on Tuesday 07 September, 2010. |
