Alloy Steels: Properties and Applications

Nickel Steels

Nickel steels are known for their stainless and electrical properties. Nickel increases the tensile strength, yield stress, elongation, and impact strength or resilience of steel, while simultaneously reducing the influence of heat expansion. Steels containing 10 to 15% nickel can be hardened even with slow cooling.

Chromium Steels

Chromium imparts hardness and deeper penetration of the temper, allowing for oil hardening. Steels with 1.15 to 1.30% carbon and 0.80 to 1% chromium are used for film production due to their hardness. Smaller-scale applications use steels with 0.3-0.4% carbon and 1% chromium.

Chrome-Nickel Steels

More commonly used than chromium steels alone, chrome-nickel steels are employed in various ratios. Examples include:

• 0.10% carbon, 0.70% chromium, and 3% nickel
• Up to 15% carbon, 1% chromium, and 4% nickel (used as hardened steel)

Oil-hardening steels are used in various proportions. A common example is a steel with 0.30% carbon, 0.7% chromium, and 3% nickel.

Chrome-Moly Steels

These steels are easier to work with using machine tools. Molybdenum significantly increases the hardenability of steel. Chrome-moly steels are increasingly used in construction, often replacing nickel steels. Common types include:

• 0.10% carbon, 1% chromium, and 0.2% molybdenum
• 0.3% carbon, 1% chromium, and 0.2% molybdenum

Many other compositions exist, varying according to their intended use.

Chrome-Nickel-Molybdenum Steels

These steels exhibit excellent mechanical properties. A prime example is a steel with 0.15% to 0.2% carbon, 1 to 1.25% chromium, 4% nickel, and 0.5% molybdenum.

Stainless Steels

Stainless steels are resistant to atmospheric and chemical agents. The first stainless steels were developed for cutlery, containing 13 to 14% chromium. Other stainless steels, used in surgical equipment, contain 18 to 20% chromium and 8 to 10% nickel, and are also resistant to seawater. A steel with high resistance to hot oxidation contains 20 to 30% chromium and 5% aluminum.

Manganese (Mn)

Manganese is a fundamental and indispensable element present in most steel alloys. It is an austenite former and, when combined with sulfur, prevents the formation of iron sulfide at grain boundaries, which is highly detrimental to the lamination process. Manganese is used to remove rust and increase hardenability.