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Grades Of Steel

Posted on Thursday, May 13, 2021

Grades Of Steel

What does “Grade of steel” mean?  

Grades are used to differentiate between types of steel based on their chemical compositions and properties. There are standards set nationally and internationally so you can be sure you’re getting the same thing, no matter where you get it from.  


How many grades of steel are there?  

According to the World Steel Association, there are over 3,500 grades of steel. Wow, that’s a lot. No problem, we’ll talk about what to look for and how to narrow it down from 3,500 to a much more manageable number to choose from.  


What goes into determining a grade of steel? 

The amount of carbon the steel contains, if any, if the steel has any other alloying elements and how much, and the way the steel has been processed.  


Where do I begin?  

It might help to understand the four main types of steel. The steel grades are often categorized into carbon, alloy, stainless, and tool groups.  


Roughly 90% of steel falls into this group. They only contain small amounts of elements other than carbon and iron. Subgroups- low/mild carbon steel (up to 0.3% carbon), Medium carbon steel (0.3-0.6% carbon), and High carbon steel (more than 0.6% carbon).  


Added alloying elements into the steel such as nickel, copper, chromium, or molybdenum. Addition of alloys in different quantities influence properties such as strength, ductility, corrosion resistance, or machinability. Our post on 11 elements dives deeper into what each alloy does to steel.  


Everyone’s heard of stainless steel- it’s common in medical equipment, appliances, cutting tools, and piping. Stainless steel has a concentration of chromium ranging between 10-20%, which gives it a high corrosion resistance rating.  


Contain tungsten, molybdenum, cobalt, and vanadium for increased heat resistance and a higher durability. It’s good for cutting and drilling equipment.  


How do I know it’s all the same?  

Governing Bodies – Some of the well-known ones include ASTM (American Standard for Testing Materials)ASME (American Society of Mechanical Engineers) SAE (Society of Automotive Engineers) ANSI (American National Standards Institute), and AISI (American Iron & Steel Institute). So, there are quite a few different options, but they all follow roughly the same outline. Their goals are also typically the same—to standardize steel production to be universally applied across many industries. These governing bodies give consumers of steel products confidence that the steel they are using will meet the requirements of their applications.


What do the numbers mean?

In carbon grades of steel, the numerical designation usually follows some sort of variation of 10XX, where the “XX” describes the amount of carbon within that steel. For example, 1045 has a nominal carbon content of 0.45. 

 For grades of steel with particular physical property requirementssuch as a tensile strength, yield strength, elongation, or hardness, there is a qualifier in the name. Each governing body uses something a little different, so we’re going to use ASTM as an example. ASTM uses a naming convention that typically begins with the letter “A (like A36, A572 Grade 50, or A514). In this case, A36 means the steel has a minimum of 36,000 PSI of yield strength.   


How do I know if I am buying the right grade for my application?  

Steel has been produced since the mid 1800’s. Luckily, scientists and engineers have been able to improve and innovate the steel making process since those days. The governing bodies above have earned the respect and confidence of steel consumers through their countless hours of studying the chemistries of steel. When choosing the grade of steel for your application, it’s best practice to go with what was specified by the blueprint’s designer. If you don’t have those, or it hasn’t been established yet, talk to a Clifton Steel representative for help. Steel is our life, and we’ll be able to guide you in the right direction.