Carbon is present in all steels and provides hardenability. Strength and hardness increase with increased carbon content. Ductility and weldability decrease as carbon increases.
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Get the facts on steel types with your go-to reference for carbon and alloy steel grades.
Carbon and alloy steels are two of the most common types of steel used in manufacturing and machining. Both contain small amounts of carbon and alloying elements, but their properties differ. Carbon steel is often used as-is without heat treatment, though it can be case-hardened. Adding lead or sulfur improves machinability but reduces weldability, heat treatability, and formability. This type of steel is ideal for parts that do not require special properties or heat treatment. Alloy steel contains additional alloying elements and carbon to enhance mechanical properties and hardenability. These elements allow the steel to form carbon or alloy carbides, improving wear resistance and toughness when heat-treated.
Alloying Elements in Different Types of Steel
Material Type and Description
Carbon Steels
Types of Steel | Descriptions & Common Uses |
|---|---|
1018 | Low-carbon cold-finished bar used as a general-purpose steel. Can be carburized for a hard surface. Good weldability and bendability. Used for machine parts, structural parts, gears, cams, worms, and pinions. |
1045 | Medium-carbon cold-drawn steel for applications requiring more strength than 1018. Used for shafts, bolts, gears, and pinions. Responds well to heat treatment. Welding requires special procedures. |
12L14 | Leaded carbon steel (.15–.35% lead with sulfur) with excellent machinability. Common for shafts, bushings, couplings, and hydraulic fittings. Not weldable or hardenable. |
1215 | Free-machining, resulfurized, and rephosphorized non-leaded steel. Produces a smooth, bright finish. Used for bushings, shafts, and machine parts. Poor weldability due to sulfur; not typically heat-treated. |
Alloy Steels
Types of Steel | Descriptions & Common Uses |
|---|---|
4140 | General-purpose alloy steel with better wear resistance than carbon steels. Suitable for gears, cams, dies, spindles, bolts, and low-cost molds. |
8620 | Nickel-chromium-molybdenum alloy steel, usually carburized for a tough core and wear-resistant surface. Used for gears, crankshafts, shafts, and gear rings. Good machinability before carburizing. |
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