Effect of alloying elements

Aluminium

This acts as a deoxidizer to increase resistance to oxidation and scaling. It aids nitriding, restricts grain growth, and may reduce strength unless in small quantities. The range used is 0-2%.

Chromium

A range of O M % , improves wear, oxidation, scaling resistance, strength and hardenability. It also increases high-temperature strength, but with some loss of ductility. Chromium combines with carbon to form a wear-resistant microstructure. Above 12% the steel is stainless, up to 30% it is used in martensitic and ferritic stainless steel with nickel.

Cobalt

Cobalt provides air hardening and resistance to scaling. It improves the cutting properties of tool steel with 8-10%. With chromium, cobalt gives certain high alloy steels high-temperature scaling resistance.

Copper

The typical range is 0.24.5%. It has limited application for improving corrosion resistance and yield strength of low alloy steels and promotes a tenacious oxide film.

Lead

Up to 0.25% is used. It increases machineability in plain carbon steels rather than in alloy steels.

Manganese

The range used is 0.3-2%. It reduces sulphur brittleness, is pearlitic up to 2%, and a hardening agent up to 1 Yo. From 1-2% it improves strength and toughness and is non-magnetic above 5%.

Molybdenum

The range used is 0.3-5%. It is a carbide forming element which promotes grain refinement and increases high-temperature strength, creep resistance, and hardenability. Molybdenum reduces temper brittleness in nickel-chromium steels.

Nickel

The range used is 0.3-5%. It improves strength, toughness and hardenability, without affecting ductility. A high proportion of it improves corrosion resistance. For parts subject to fatigue 5% is used, and above 27% the steel is non-magnetic. Nickel romotes an austenitic structure.

Silicon

The usual range is 0.2-3%. It has little effect below 3%. At 3% it improves strength and hardenability but reduces ductility. Silicon acts as a deoxidizer.

Sulphur

Up to 0.5% sulphur forms sulphides which improve machineability but reduces ductility and weldability.

Titanium

This is a strong carbide forming element. In proportions of O.2-O.75% it is used in maraging steels to make them age-hardening and to give high strength. It stabilizes austenitic stainless steel.

Tungsten

This forms hard stable carbides and promotes grain refining with great hardness and toughness at high temperatures. It is a main alloying element in high speed tool steels. It is also used for permanent-magnet steels

This is a carbide forming element and deoxidizer used with nickel and/or chromium to increase strength. It improves hardenability and grain refinement and combines with carbon to form wear-resistant microconstituents. As a deoxidizer it is useful for casting
steels, improving strength and hardness and eliminating blowholes, etc. Vanadium is used in high-speed and pearlitic chromium steels.

Vanadium

This is a carbide forming element and deoxidizer used with nickel and/or chromium to increase strength. It improves hardenability and grain refinement and combines with carbon to form wear-resistant microconstituents. As a deoxidizer it is useful for casting
steels, improving strength and hardness and eliminating blowholes, etc. Vanadium is used in high-speed and pearlitic chromium steels.

 

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