What is Alloy Steel in Piping? Low vs High Alloy Steel

In this lecture, you will learn about alloy steel.

When you add various metallic and non-metallic elements in a specific amount to carbon steel, it will change the properties of carbon steel. We can manipulate these percentages of alloying elements in steel to achieve better properties than plain carbon steel.

Alloy steel can further classify as

Low alloy steels: in which the sum of total Alloying elements is < 5%
High alloy steels: in which the sum of total Alloying elements is > 5%

Alloying Elements

Commonly used alloying elements and their effects are listed in the table given below.

Alloying Elements	Effect on the Properties
Chromium	Increases Resistance to corrosion and oxidation. Increases hardenability and wear resistance. Increases high temperature strength.
Nickel	Increases hardenability. Improves toughness. Increases impact strength at low temperatures.
Molybdenum	Increases hardenability, high temperature hardness, and wear resistance. Enhances the effects of other alloying elements. Eliminate temper brittleness in steels. Increases high temperature strength.
Manganese	Increases hardenability. Combines with sulfur to reduce its adverse effects.
Vanadium	Increases hardenability, high temperature hardness, and wear resistance. Improves fatigue resistance.
Titanium	Strongest carbide former. Added to stainless steel to prevent precipitation of chromium carbide.
Silicon	Removes oxygen in steel making. Improves toughness. Increases hardness ability
Boron	Increases hardenability. Produces fine grain size.
Aluminum	Forms nitride in nitriding steels. Produces fine grain size in casting. Removes oxygen in steel melting.
Cobalt	Increases heat and wear resistance.
Tungsten	Increases hardness at elevated temperatures. Refines grain size.