Phosphorus can be either a steel parasite or an alloying element. The harmful effect is predominant, as it can lead to embrittlement and increases the cold brittleness and tendency to brittle fracture. For this reason, phosphorus is largely removed from steel alloys in most cases.

Wavellite | Phosphorus-containing mineral

As an alloying element, phosphorus only develops its effect in low-alloy steel with a carbon content of about 0.1%. Phosphorus then increases strength and also improves corrosion resistance. In austenitic chrome-nickel steels, phosphorus can increase the yield strength.

The effect of phosphorus upon mechanical steel properties:

Property Influence Degree
Rust resistance no bearing 0
Hardness Improvement + 1
Strength Improvement + 1
Yield strength Improvement + 1
Elasticity no bearing 0
Heat resistance no bearing 0
Carbide formation no bearing 0
Wear resistance no bearing 0
Nitratability no bearing 0
Strain Decrease - 1
Reduction of area Decrease - 1
Notched Impact Strength Decrease - 3
Forgeability Decrease - 1
Scaling no bearing 0
Machinability Improvement + 2


The German pharmacist Henning Brand discovered phosphorus by chance in 1675. He was convinced that human urine was suitable for gold production because of its yellow colour. He boiled about 50 buckets of urine until he obtained a wax-like mass.

He did not make gold with it, but after a while the mass began to glow. Parts that were brought into the refining air caught fire. Since the production was too expensive, no benefit could be derived from it. In 1774 the German-Swedish pharmacist Scheele was the first to produce phosphorus from bones.

See also

Accompanying Elements

Steel does not only consist of iron and carbon. Other elements can influence the properties of steel.

Read more
Alloying Elements

There is a large number of different alloying elements. Each one influences the material properties.

Read more

Here you can find out why aluminium was discovered so late and how aluminium can be produced.

Read more

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