Alloying Elements and Properties of Steel

Here are a few major alloying elements for steel and some informatioen about what they can do.
This list is based on the "Materials in Action Series; Structural Materials"
 
Element Influence on Ferrite Influence on Hardenability Tendency to form hard Carbides Major Functions
Manganese
Mn		 Powerful solution strengthener Moderate increase Middle 1. Takes care of Sulphur (S).
2. Cheap increase of hardenability.
Silicon
Si		 Hardens, but reduces ductility Moderate increase - 1. Deoxidation of liquid steel.
2. Improves oxidation resistance.
3. Strengthens low alloy steel.
4. Increases electrical resistivity (important for transformer cores).
Chromium
Cr		 Strengthens a little
Provides corrosion resistance		 Moderate increase Strong 1. Corrosion resistance.
2. Hardenability.
3. Abrasion resistance (needs high C, too).
4. Strength + oxidation resistance at high T.
Titanium
Ti		 Age hardening possible Very strong increase Extremely strong 1. Forms hard carbides.
2. Prevents local depletion of C carbon in stainless steels due to Cr-carbide formation
Vanadium
V		 Moderate solid solution hardening Very strong increase Very strong 1. Restricts grain coarsening of austenite.
2. Increases hardenability.
3. Delays softening during tempering.
Nickel
Ni		 Strengthens Mild improvement
stabilizes austenite		 - 1. Improves strength and toughness at subzero T.
2. Together with Cr provides austenitic steel.
Molybdenum
Mo		 Age hardening possible Strong increase Very strong 1. Increase hardenability.
2. Prevent embrittlement of certain Ni/Cr steels.
3. Keeps strength at higher T.
4. Restricts austenite grain growth.
5. Improves corrosion resistance of stainless steels.
6. Provides carbides with high abrasion resistance.
Cobalt
Co		 Strengthens in solid solution Decreases slightly Like Fe 1. Contributes hardness at moderately high T.
 
The list could go on for a while, of course. It includes some properties not much discussed before, for example:
Behavior at low and/or high temperatures.
Properties like wear (or abrasion) resistance or corrosion resistance (note that stainless steel, while oxidation resistant, might nevertheless corrode in some other chemical environment.
Making steel in the first place (look for "liquid").
Counteracting the effects of other elements.
Keeping the structure from unwanted changes ("grain growth")
     
 

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