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Steel grades are essential in helping determine precisely the right steel for your application. Understanding the different types of steel (carbon, alloy, stainless and tool steels) and steel grades and applications may seem daunting at first — according to the World Steel Association, there are more than 3,500 varieties on the list of steel grades. However, a solid understanding of how and why steel is graded the way it is will help you choose the proper steel composition for each project.

Steel Grades Explained

Steel grades tell us the amount of carbon in the steel, the potential presence and amounts of other alloying elements, and the way the steel was heated and processed. Steel grades are important because they standardize precisely what each material is. An engineer, a scientist, an architect, a manufacturer and a bureaucrat can all look at the grade of steel and know exactly what that material is made of, how it was made, and for what it would be best used.

Since steel grades tell us so much about the steel properties, it’s much more valuable than a simple ranking system. Steel grades don’t rank one steel over another (often, the best steel for one application is not the best steel for another). By giving us the essential information about each material, steel grades help us determine which steel works best for each specific use.

Classification of Steel

To classify steel, two grading systems are used: the ASTM and SAE systems. These tell us about the attributes of a material, as well as its composition and the process that was used to produce the steel. It’s not uncommon for two materials with the exact same composition to have different grades due to the way they were processed.For example, hot-rolled steel and cold finished steel could have the same alloy composition, but the additional processing undergone by cold finished steel will classify each material differently.

ASTM Grading System

The American Society for Testing and Materials (ASTM) grading system labels materials based on the qualities and properties of the steel. ASTM grades will begin with a letter (A is for iron and steel) and be followed by a number, which directly references that particular steel’s qualities per ASTM standards.

SAE Grading System

The Society of Automotive Engineers (SAE) grading system, often used together with the American Iron and Steel Institute (AISI) system, specifically outlines the chemical composition of steel. The first two digits of each four-digit number tell us the type and prevalence of the alloy and the last two digits tell us the carbon concentration. Take a look at our hot-rolled bar selection to see the many low-carbon, mid-carbon, and high-carbon grades available.

Steel Grades Across Industries

Because steel is such a versatile material that can have so many different attributes, any chosen steel grade often applies to multiple industries. Selecting the right steel considers the application more than the industry. Still, here are some of the most commonly used steel grades and the various industries that use them:

  • Carbon steels are frequently used in the construction and automotive industries, as well as in machinery. Carbon steels are economical and can be fabricated to possess many desired attributes, such as easy weldability in a low-carbon grade like A36, strength and hardness in a medium-carbon grade like 1045, or immense hardness and wear-resistance like 1095.
  • Alloy steels can be used in just about any industry and application as the alloys are created to generate a specific steel quality or attribute. Frequently used alloy steels include 316L (a nickel-chromium steel that resists corrosion) and a pair of molybdenum steels, 4140 for toughness or strength, and 4340 for wear resistance or high tensile strength.
  • Stainless steel is common in many industries as it is a strong material that resists corrosion and extreme temperatures. The most common grade of stainless steel is 304 (austenitic stainless steel) and is used in everything from machinery, utensils, and food handling to exterior construction components. Many household appliances go with 430 (ferritic) and surgical instruments are often made of 410 (martensitic).
  • Tool steels are primarily used in, yes, tools. Wear-resistant, heat-resistant, and tough (in general, that is, as different grades have different or more prevailing attributes), common grades for tool steels are D2, A2, and M2.

This is merely a small sample of some of the common steel grades and uses. It doesn’t necessarily mean any of these particular steel specifications are the best for your project, but they very well could be. It’s important to discuss with your steel provider exactly what properties you need in your materials so you can find the perfect grade.

How to Choose the Right Steel Grade

Knowing the basics of how steel grades work, you can already start to narrow down the aforementioned 3,500 different steel grades to determine what you need from your steel. Enlist the help of our experts at Capital Steel & Wire, who are experienced in finding precisely the best steel for each application.

When you’re ready to get your project moving, contact us and we’ll discuss what you’re trying to accomplish and which grade of steel is right for you.