The density of steel is in the range of 7.75 and 8.05 g/cm3 (7750 and 8050 kg/m3 or 0.280 and 0.291 lb/in3). The density of carbon steels, alloy steels, tool steels and stainless steels are given below in g/cm3, kg/m3 and lb/in3.
The American Iron and Steel Institute, or the AISI, categorizes steel in 4 groups based on chemical composition. These are Carbon Steel, Alloy Steel, Stainless Steel and Tool Steel. Within each category, there are many different grades of steel that have varying physical, chemical and environmental properties. It is the amount of carbon and the additional alloys that determine the properties of each grade.
To identify the properties of steel, the steel industry uses two major numbering systems. The first was developed by the AISI and the second by the SAE (Society of Automotive Engineers). Both systems use four-digit number codes which identify the base carbon and alloy steels.
If the first digit is 1, that indicates the carbon steel (e.g., 1018). The next digit indicates the subcategory based on particular underlying properties. For example, 10xx series indicates plain carbon steel containing 1% Manganese maximum. The 11xx series contains re-sulfurized carbon steel. The 12xx series is re-sulfurized and re-phosphorized carbon steel. Remaining alloy steels under the SAE or AISI systems are classified as below.
2 = Nickel Steel
3 = Nickel-Chromium Steel
4 = Molybdenum Steel
5 = Chromium Steel
6 = Chromium – Vanadium Steel
7 = Tungsten – Chromium Steel
8 = Nickel – Chromium – Molybdenum Steel
9 = Silicon – Manganese Steel
Generally, but not always the second digit in the series indicates the concentration of the major element in percentiles.
The last two digits indicate the carbon concentration to 0.01%.
So 4140 indicates a molybdenum alloy steel containing 1% of molybdenum and 0.40% carbon.
As the name indicates, the main alloying ingredient in this type of steel is carbon. Carbon steel is highly versatile, and its uses and properties vary depending on its carbon content. As the carbon content rises, the steel becomes harder and stronger. However, it does become less ductile, more brittle and harder to weld. Also, the higher the carbon, the lower the melting point of the steel. Carbon steel is further broken down into four groups based on its carbon content: low/mild, medium, high and ultra-high.
Also known as Mild Steel, low carbon steel contains approximately 0.04-0.3% carbon. Because of this, it is malleable, ductile, tough, very easy to weld, and one of the cheaper forms of the steel (e.g. AISI 1018). The theoretical density of mild steel is about 7.87 g/cm3 (0.284 lb/in3).
For Medium Carbon Steel, carbon content ranges from 0.31-0.6%, is stronger and harder than Mild Steel, but it is more difficult to weld and form. It is common in large parts, forged parts and automotive components. Common example is AISI 1045.
High or Carbon Tool Steel generally has a range of 0.61-1.5% carbon. This material is extremely hard and brittle. Because of this, it is very difficult to bend, weld, or cut.
Ultra-High Carbon Steel has a carbon content ranging from 1.5-2% and can be heat treated to exceptional hardness.
Technically every steel is an alloy, but not all steels are called “alloy steels”. This term refers to steels that have been alloyed with elements in addition to carbon. The most common elements include manganese, chromium, nickel, silicon, boron, molybdenum and vanadium. Adding other elements to iron and carbon can improve a range of properties including strength, hardness, toughness, wear resistance, corrosion resistance and hardenability. Alloy steels are broken down into two groups: low-alloy and high-alloy. Low Alloy Steels – 1-5% alloy content, easily weldable with appropriate precautions.
Stainless steel is steel that has a minimum of 10 % chromium. The high chromium and carbon content give stainless steel its corrosion resistance, strength and hardness. There are 6 main types of stainless steel. Austenitic, Super-Austenitic, Ferritic, Duplex Steel, Martensitic and Precipitation hardening martensitic. At present, there are over 150 specific alloys of stainless steel.
Tool steel is particularly well-suited for making tools because of its distinctive hardness, resistance to abrasion and ability to hold a cutting edge at elevated temperatures. The 4 major alloying elements in tool steel are tungsten, chromium, vanadium and molybdenum. According to AISI and SAE specifications, there are six major type of tool steels based on how they are hardened or what they are used for. Six main types are Water Hardening, Cold Working, Shock Resistant, High Speed, Hot Working and Special Purpose.
The density of a material is the mass contained in a unit volume. The unit of density is kg/m3 or lb/in3.
The formula for density is p = m/V, where p is the density, m is the mass and V is the volume. For solid materials, density decreases with increasing temperature.