Nickel - is added to steels to increase hardenability. It often improves the toughness and ductility of the steel, even with the increased strength and hardness it brings. It is frequently used to improve toughness at low temperature.
Aluminum - is added to steel in very small amounts as a deoxidizer. It also is a grain refiner for improved toughness; steels with moderate aluminum additions have been made to a "fine grain practice".
Vanadium - The addition of vanadium will result in an increase in the hardenability of a steel. It is very effective, so it is added in minute amounts. At greater than 0.05%, there may be a tendency for the steel to become embrittled during thermal stress relief treatments.
General Steel Definitions:
Ingot iron - 0.03% maximum carbon, used for enameling, galvanizing, deep drawing sheet and strip, excellent weldability.
Low- Carbon - 0.15%maximum carbon, used for electrodes, plate and shapes, sheet, strip, excellent weldability.
Mild steel - 0.15-0.30% maximum carbon, used for structural shapes, plates and bars, good weldability.
Medium carbon - 0.30-0.50% maximum carbon, used for machinery parts, fair weldability - preheat and postheat may be needed.
High carbon - 0.50-1.00% maximum carbon, used for springs, dies, rails, poor weldability - difficult to weld without preheat and postheat.
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