Steel is one of the most versatile materials on the planet. It is made up of iron and carbon with added alloying elements to make it more effective for specific applications.
Understanding the different grades of steel can help you choose the best metal for your project. There are over 3,500 different types of steel based on the amount of carbon, level of impurities and other alloying elements.
Grade A
Steel is the most versatile and useful metal in existence, used to make everything from the tallest skyscrapers to the smallest kitchen cutlery. It is a very strong and resilient material, which can be formed into almost any shape and capable of withstanding high temperatures and winds. However, many people don’t realize that even within this remarkably durable metal there are several different grades of steel to meet specific applications.
The difference between these grades has to do with the concentration of iron and carbon as well as the addition of other alloying elements and how they are processed. Authorities such as the ASTM (American Society for Testing and Materials) and AISI (American Iron and Steel Institute) have set up standards that classify these metals by their properties. The basic classification system consists of a letter designation followed by a number that identifies the type and amount of carbon as well as the other alloying elements in the steel.
Grade A, also referred to as normal steel or mild steel, has low amounts of carbon and is easy to work with. It is a great choice for most construction projects because it provides excellent tensile strength without breaking under stress. The yield strength, which is the maximum load a piece of steel can take before it starts to deform permanently, is usually around 235 MPa.
Grade B
Grade B steel is used in construction applications that require high strength. It has a high yield and tensile strength that makes it suitable for use in piling and bridge construction. It also has a good resistance to corrosion.
The physical properties of grade B steel can vary widely depending on the production process and heat treatment. For instance, the rate at which manufacturers cool the steel has a significant impact on how strong it is on a molecular level. This is because it can change the shape of the austenite metal into ferrite form.
It is also important to consider the machinability and weldability of steel when selecting grades for certain applications. These properties are determined by hardness, which is influenced by the amount of carbon in the material. The lower the carbon content, the easier it will be to machine and weld.
In addition, the physical properties of grade B steel can be altered by manipulating the microstructure and chemical composition. For example, adding chromium or nickel to a steel mix can improve its corrosion resistance or ductility. Similarly, hot and cold forming can affect a steel’s yield and tensile strength, while tempering will increase the hardness of the material. By altering these factors, producers can create a steel with specific mechanical properties. This allows fabricators to select the grade of steel that is best suited for their application.
Grade C
Steel is one of the most useful materials on Earth, and while many people assume it’s a simple combination of iron and carbon, the reality is more complex. The concentration of carbon and other alloying elements determines the specific properties and strength of each grade of steel, allowing it to be used in an infinite number of scenarios.
For example, Grade C is often used to make automotive components and other metals that need to withstand high levels of pressure and abrasion. The high tensile strength of this type of steel allows it to bear such conditions, but it also has excellent ductility and fatigue resistance.
The basic grading system for steels is determined by several different standards organizations, including ASTM International and the Society of Automotive Engineers. The system uses a four-digit number to classify the material; the first two digits denote the steel type and alloying element concentration, and the last two digits indicate the carbon concentration.
A suffix can also be added to the grade name, denoting the forming process or other characteristics. For example, the grade designation 1214 is actually 12L14, as it has lead added for machinability. Similarly, grades with an “S” after the number specify that the material is suitable for use in saltwater applications. Other letter suffixes can indicate additional alloying elements such as chromium (Cr), nickel (Ni), molybdenum (Mo), and vanadium (V). These elements enhance the performance of the steel and give it its unique properties.
Grade D
Steel grading standards provide a common language for engineers, fabricators and consumers to discuss the properties of metals with great specificity. They specify everything from chemical compositions to physical properties and fabrication processes. They also dictate a material’s ultimate tensile strength. For example, bridge plate girders need to be able to handle the weight of heavy trucks and other vehicles that pass over them. Consequently, they need to be made from grade D carbon steel that has an intermediate tensile strength rating.
Steel’s hardness is another property that can be used to determine its grading. The harder a steel is, the more resistance it has to abrasion and impact. Higher carbon levels and heat treatments like quenching can increase a steel’s hardness and strength.
For example, O grade tool steel is a type of oil hardening steel that has exceptional toughness and abrasion resistance. This material is often used to make hand tools and machine dies due to its ability to retain its shape when enduring heavy usage.
Steel grading systems typically use four-digit numbers for classification, with the first two digits indicating the steel type and alloying element concentration, and the last two digits indicating the carbon concentration. However, other naming systems exist, including the EN 10027-2 system which uses unique numerical codes instead of descriptive names.