Steel Alloys and Alloying Agents

Carbon

Allows steels to be heat treated to obtain hardness, strength and toughness. The greater its content of this, the better heat treatment ability.

Sulphur

Undesirable constituent of steel and must be removed. Causes brightness in steel and using manganese may counteract the effect of it.

Manganese

Produces a clean, tough and uniform metal. Also improves forging characteristic by reducing brittleness

Silicon

Acts as a hardener and in small quantities improves ductility

Phosphorous

Raises the yield strength and corrosion resistance

Nickel

Adds strength and hardness. Also increases yield strength. Major ingredient for corrosion resistant steel

Chromium

Increases the strength, wear and corrosion resistance

Molybdenum

It increases impact strength and elastic limit

Vanadium

It increases the tensile strength and toughness

Titanium

It reduces the brittleness of the steel

1XXX Carbon Steel

Can be low carbon steel, medium carbon steel, or high carbon steel

Low carbon steel

(0.10% - 0.30%)
Used for making safety wires and secondary structural parts where strength is not critical

Medium Carbon steel

(0.30% - 0.50%)
Used for machined and forged parts especially where surface hardening is needed.

High Carbon Steel

(0.50% - 1.05%)
Used where extreme strength is needed. Ex. Springs, file, drill bit.

2XXX Nickel Steel

Used to increase hardness, tensile strength, and elastic limit, without decreasing ductility. An alloy from this series is used for aircraft bolts, cable terminals, pins, clevises.

3XXX Nickel-Chromium Steel

This gives both additional toughness and hardness. It is used for forged and machined parts where high strength, ductility, toughness and shock resistance is needed.

4XXX Chromium-Molybdenum Steel

Most of the aircraft structure is made of this alloy which combines toughness and high strength. It is easy to machine and weld.

5XXX Chromium Steel

It increases strength and hardness as well as improve its wear and corrosion resistance. Used in balls and rollers of antifriction bearings.

6XXX Chromium-Vanadium

It is used extensively for wrenches and other hand tools where strength and toughness is essential

Stainless Steel

It is steel that is corrosion resistant, high in strength and toughness, and is resistant to high temperatures.

200 series Austenitic

It is a stainless steel which has Chromium & Manganese & Little Nickel

300 series Austenitic

It is a stainless steel which has Chromium & Nickel and it is the most widely used stainless steel

400 Series

It is a stainless steel series which can be categorized into martensitic and ferritic

Martensitic

It is a stainless steel in the 400 series that has iron-chromium

Ferritic

It is a stainless steel in the 400 series that has chromium with no nickel

18-8

This specifically is the most widely used stainless steel in the 300 series which contains approximately 18% chromium and 8% nickel