Carbon steel is a misleading term -- all steel has carbon in it. Likewise, it’s hard not only to keep track of what’s considered carbon steel, but also which grades possess the qualities your project needs. That’s why we’ve compiled a carbon steel grades chart or two for you.
Use the information below to get the best use out of carbon steel. Despite its shortcomings, it’s got a lot to offer your component!
Carbon Steel Defined
Carbon steel is an alloy of iron and carbon (shocking, we know). This steel type may also include traces of other elements, like manganese, up to a 1.65% maximum; silicon, with a 0.6% maximum; and copper, up to 0.6%.
Most folks divide this steel type into three levels of carbon content:
- Low-carbon steel (mild steel): Typically consists of 0.04% to 0.3% carbon. Depending on the properties you need, you can opt for a type with a certain element added or increased. (Ex.: In structural steel, carbon and manganese content is higher.)
- Medium-carbon steel: Generally contains between 0.31% and 0.6% carbon, plus 0.06% to 1.65% manganese. Stronger than low-carbon steel, but harder to weld, form, or cut. Often hardened and tempered via heat treatment.
- High-carbon steel: Commonly known as “carbon tool steel.” Typically has a carbon range between 0.61% and 1.5%. Very difficult to bend, weld, or cut. Once heat-treated, it becomes quite hard and brittle.
Carbon Steel Grades Chart: The Most Popular Metals
Here are the most common carbon steel grades, in chart form. If you don’t want to put a lot of effort into your material picking, stick with these common types -- your vendor will know all about them.
You can download the full, printer-friendly PDF version here or by clicking on the image.
Carbon Steel Grades Chart: Best of the Rest
You’re probably wondering what all these intimidating numbers mean.
#1: General Grouping
In general, the first number of each grade depicts a general category of steels. They are:
- 1XXXX: Simple carbon steel
- 4XXXX: molybdenum steel
- 5XXXX: chromium steel
- 6XXXX: chrome-vanadium steel
- 8XXXX: nickel-chromium -molybdenum steel
- 9XXXX: silicon -manganese steel
Here's a more detailed look, in chart form, at what these categories look like. You can download the full, printer-friendly PDF version here or by clicking on the image.
#2 Elemental Attributes
The second number indicates the presence of elements that affect the steel’s traits.
For example, the zero in a 10XX grade indicates there are no major secondary elements, such as sulfur, inside. Why would this matter? Sulfur, lead, and other elements in steel can increase machinability. Yet they can also cause pockets or other faults that can hamper some applications.
#3 and #4: Carbon Content
The last two characters represent the steel’s carbon content.
A piece of 1018 steel contains 0.18% carbon. Note that standards will actually show an allowable carbon range of 0.15-0.20% for this grade. That’s because it’s impossible for steel makers to control carbon and alloy contents with flawless precision.
Need More Help Optimizing Your Project?
We get it. There’s a lot to consider when choosing a material for your component -- even if price is your chief concern. Carbon steel can work beautifully for projects that need to be cost-effective, but there’s more to it than just grabbing a cheap metal.
If you’re still lost in the woods on how to maximize your company’s dollars, read up on steel costs and how they affect your supply chain.