Effect of elements in Alloy steels

Vanadium:

• It gives steel a fine-grained structure and increase its toughness.
• It is often used in tool steels because of its increased resistance to impact.
• Increases hardenability
• Imparts strength and toughness to heat-treated steel
• Causes marked secondary hardening

It is used with chromium to make chrome-vanadium steel from which transmission parts and gears are manufactured. This type of steel is very strong and has excellent shock resistance. Less than 0.2% is used normally with 0.5 to 1.5% of chromium.

Chromium

• It provides corrosion resistance.
• Increase hardenability or the depth to which steel can be hardened
• Adds hardness, toughness and resistance to wear.

Gears and axles are often made of chrome-nickel steel because of its strength. Chromium less than 0.2% can be effective in increasing hardenability.

Niobium

• Greatly increases tensile strength of steel. Only 40 lb of niobium per ton of steel will increase the tensile strength by 10,000 to 15000 lb/in².

Tungsten in the form of tungsten carbide

• Gives steel high hardness even at red heats.
• Promotes fine grains
• Resists heat
• Promote strength at elevated temperatures

 It is used with chromium, vanadium, molybdenum, or manganese to produce high speed steel used in cutting tools. Tungsten steel is said to be "red-hard" or hard enough to cut after it becomes red-hot.

Titanium is a very strong, very lightweight metal that can be used alone or alloyed with steels. It is added to steel to give them high strength at high temperatures. Modern jet engines used titanium steels.

• It prevents localized depletion of chromium in stainless steels during long heating
• Prevents formation of austenite in high chromium steels
• Reduces martensitic hardness and hardenability in medium chromium steels.

Phosphorus and Lead are added to steel to increase its machinability.

Phosphorus is considered detrimental in steel but small quantities up to 0.2% in low carbon steels increases hardness, strength and corrosion resistance. Phosphorus increases strength and hardness to approximately to the same extent as carbon in steels which are normally used in hot-rolled conditions. In some steels, high phosphorus content is undesirable because it decreases ductility and impact toughness. It is undesirable in high carbon steels on account of excessive loss of ductility. It improves machinability in lower carbon steels and improves resistance to atmospheric corrosion.