Element

&

Symbol

Solid solubility

Influence

upon ferrite

Influence upon austenite (hardenenability)

Influence exerted through carbide.

Principal function of the element.

In

gamma Fe

In

alpha Fe

Carbide-forming

tendency

Action during temperature

Aluminum(Al)

1.1% (increase by carbon)

36%±

Hardens

considerably by solid solution

If dissolved in austenite increases hardenability mildly

Graphitizes

—

a.        Used as deoxidizer.

b.        Restricts grain growth.

c.        Alloying element in nitriding steels.

Chromium(Cr)

12.8% (in 0.5%C steels 20%)

Unlimited

Hardens slightly;

increased

corrosion resistance

Increases hardenability moderately, similar

 to manganese

Greater than

Mn less than

W

Mildly resists softening

a.        Increases corrosion and oxidation resistance.

b.        Increases hardenabability.

c.        Increases strength at high temperature.

d.        With high C resists wear and abrasion.

Cobalt(Co)

Unlimited

75%

Hardens

considerably by solid solution

Decreases hardenability as

dissolved

Similar to Fe

Sustains hardness by solid solutions

a.        Contributes to red hardness by hardening ferrite.

b.        Alloying element is certain high-speed steels.

Manganese

(Mn)

Unlimited

3%

Hardens, ductility somewhat reduced

Similar to Ni

Greater than Fe, less than Cr

Very little

in usual percentage

a.        Counteracts effect of brittleness from sulphur.

b.        Increases hardenability inexpensively.

c.        High Mn. high C produces steels resistant to wear and abrasion.

Molybdenum

(Mo)

3% (with 0.5% C steels 8%)

37.5% (less

with

lowered temp)

 Age-hardening system in high
Mo-Fe alloys.

Increases hardenability

strongly

Strong, greater than Cr

Opposes softening by secondary hardening

a.        Raises grain coarsening temperature of austenite.

b.        Increases depth of hardening.

c.        Raises hot and creep strength promotes red hardness.

d.        Enhances corrosion resistance in stainless steels.

e.        Forms abrasion resistant particles.

Nickel (N)

Unlimited

10% independent of C content

Strengthens and toughens by solid solution

Increases hardenability slightly, austenite retention with higher carbon

Graphitizes less than Fe

Very little in small percentages

a.        Strengthens unquenched or annealed steels.

b.        Toughens pearlitic-ferritic steels (especially low temperatures).

c.        Renders high Cr/Fe alloys austenitic.

Phosphorous (P)

0.5%

2.8% independent of C content

Hardens strongly by solid solution. Lowers ductility inducing Brittleness.

Increases hardenability similar to Mn

Nil

—

a.        Strengthens low C steels.

b.        Increases resistance to atmospheric corrosion.

c.        Improves machinability in free cutting steel

Element

&

Symbol

Solid solubility

Influence

upon ferrite

Influence upon austenite (hardenenability).

Influence exerted through carbide.

Principal function of the element.

In

gamma Fe

In

alpha Fe

Carbide-forming

tendency

Action during temperature

Silicon (Si)

Approx. 2% (with 0.35% C approx 9%)

18.5% (carbon has little effect)

Hardens with loss in ductility.

Increases hardenability more than Ni

Negative graphitizes

Sustains hardness by solid solution

a.        Used as deoxidizer.

b.        Alloy for electrical and magnetic sheet metals.

c.        Improves oxidation resistance.

d.        Strengthens low alloy steels.

Titanium (Ti)

0.75% (with 0.2% C steels approx 1%)

Approx. 0.6% (less with lowered temperatures)

Gives age-hardening in high Fe-Ti alloy.

Probably increases hardenability very strongly dissolved; its carbide effects reduce hardenability

Greatest known (2% Ti renders, 0.5% C steel unhardenable)

Some secondary hardening

a     Fixes carbon in inert particles.

b     Reduces martensitic hardness and ardenability  
       in medium Cr steels.

c.     Prevents formation of austenite in high Cr    
       steels.

d.        Prevents localized depletion of Cr in stainless steels during long heating periods.

Tungsten (W)

6% (with 0.25% C 11%)

33% (less with lowered

temperature)

Age-hardening system in W-Fe alloys.

Increases hardenability strongly in small quantities

Strong

Opposes softening by secondary hardening

a.        Forms hard, abrasion resistant particles in tool steels, high-speed steels.

b.        Promotes red hardness and hot strength

Vanadium (V)

Approx. 1% (with 0.2% C steels 4%)

Unlimited

Hardens moderately in solid solutions.

Increases hardenability very strongly as dissolved

Very strong

Maximum for secondary hardening

a.        Promotes fine grain-elevates coarsening temperature of austenite.

b.        Increases hardenability when dissolved.

c.        Resists tempering and causes marked secondary hardening.