Carbon Steel

Carbon steel, also called plain carbon steel, is a metal alloy, a combination of two elements, iron and carbon, where other elements are present in quantities too small to affect the properties. The only other alloying elements allowed in plain-carbon steel are manganese (1.65% max), silicon (0.60% max), and copper (0.60% max). Steel with a low carbon content has the same properties as iron, soft but easily formed. As the percentage of carbon increases, there is a tendency for the metal to harden and crack.

Low Carbon Steel

Low-carbon steels contain up to 0.30% Carbon ©. The largest category of this class of steel is flat-rolled products (sheet or strip), usually in the cold-rolled and annealed condition. The carbon content for these high-formability steels is very low, less than 0.10% C, with up to 0.4% Manganese (Mn). These steels posses the best weldability of the other types of carbon steels. Of the other carbon steels, low carbon steel has the lowest cost.

Uses

Carbon Content 0.1%-0.2%: chain, stampings, rivets, nails, wire, pipe, and where very soft, plastic steel is needed.

Carbon Content 0.2-0.30%: structural steels, machine parts, soft and tough steels.

Metallurgy

The grain structure of low carbon steel is usually ferrite and pearlite, and the material is generally used as it comes from the hot forming or cold forming processes. Lacks hardenability because carbon content helps this.

Medium Carbon Steel

Medium-carbon steels are similar to low-carbon steels except that the carbon ranges from 0.30 to 0.60% and the manganese from 0.60 to 1.65%. Increasing the carbon content to approximately 0.5% with an accompanying increase in manganese allows medium carbon steels to be used in the quenched and tempered condition.

Uses

Carbon content 0.3-0.4%: lead screws, gears, worms, spindles, shafts, gears, crankshafts, couplings, forgings and machine parts.

Carbon content 0.4-0.5%: crankshafts, gears, axles, mandrels, tool shanks, and heat-treated machine parts. Rails, railway wheels and rail axles may be included in this category.

Carbon content 0.6-0.7: may be called “low carbon tool steel” and is used where a keen edge is not necessary, but where shock strength is wanted. Drop hammers dies, set screws, screwdrivers, and arbors.

Carbon content 0.7-0.8: tough and hard steel. Anvil faces, band saws,hammers, wrenches, cable wire, etc.

Metallurgy

High Carbon Steel

High-carbon steels contain from 0.60 to 1.00% C with Mn contents ranging from 0.30 to 0.90%. These steels are desirable where hardness or wear resistance is required. However, quench cracking is often a problem with severe quenching. High Carbon Steels' toughness, formability and hardenability are lower than the other steels. Welding is not recommended for these types of steels. Usually joined by brazing with low temperature silver alloy making it possible to repair or fabricate tool-steel parts without affecting their heat treated condition.

Uses

Carbon content 0.8-0.9%: punches for metal, rock drills, shear blades, cold chisels, rivet sets, and many hand tools.

Carbon content 0.9-1.0%: used for hardness and high tensile strength, springs, cutting tools, press tools, and striking dies.

Carbon content 1.0-1.1%: drills, taps, milling cutters, knives

Carbon content 1.1-1.2%: drills, taps, knives, cold cutting dies, wood working tools

Carbon content 1.2-1.3%: files, reamers, knives, tools for cutting wood and brass

Carbon content 1.3-1.4%: used where a keen cutting edge is necessary, razors, saws, and where wear resistance is important

Metallurgy

Ultra High Carbon Steel

Ultrahigh-carbon steels are experimental alloys containing 1.25 to 2.0% C. These steels are thermomechanically processed to produce microstructures that consist of ultrafine, equiaxed grains of spherical, discontinuous proeutectoid carbide particles.