In part one of this two-part blog series, we went over some of the basics and history involved in the SAE steel grading system. Perhaps the most common system used today, the SAE grading format actually came about as a combined effort between two major steel groups back in the 1930s and 1940s – it is not universally used, but is widely recognized in North America as the standard grading metric.

At Wasatch Steel, we’ll help you understand the grading system for any of our steel products or steel services offered. Whatever your project’s requirements, we’ll point you in the direction of the proper steel grade to fit your needs. In today’s part two, we’ll go over some of the details of the specific numbers used in the system, plus how stainless steel is graded a bit differently than other types within this method.

Number Grading Basics

As we discussed in part one of our series, steel alloys and carbon steel formats are expressed using a four-digit number to represent their grade. We already went over the first digit in any such number, which represents the primary alloy element involved in the steel. Certain options, such as 8xxx designations that contain nickel, chromium and molybdenum, come with multiple alloys in one.

This is not the only relevant number here, however. In cases where secondary elements are also utilized within the steel, the second number in the sequence will dictate this additional element. A few examples:

• 10xx: Refers to plain carbon steel
• 13xx: Manganese steel (generally with 1.75% manganese)
• 32xx: Nickel-chromium steel (higher amounts of chromium)
• 34xx: Nickel-chromium steel (higher amounts of nickel)
• 72xx: Tungsten-chromium steel

In addition, the final two numbers in the four-digit sequence refer to the alloy’s carbon percentage. If you see 55 as the last two digits, for instance, you know the carbon content is 0.55 wt%.

Stainless Steel Grading

Stainless steel is graded separately by the SAE system, using three digits instead of four. This is because there are fewer alloys to consider overall. However, like the standard system, the first digit in the number is the primary alloy. Here are the primary stainless steel categories to be aware of:

• 100 series: Austenitic general purpose alloys
• 200 series: Austenitic chromium-nickel-manganese alloys
• 300 series: Austenitic chromium-nickel alloys, often used in major industries like marine applications and even the production of nuclear reprocessing plants
• 400 series: Ferritic and martensitic chromium alloys, great for corrosion resistance and stain resistance
• 500 series: Heat-resisting chromium alloys, often used in space applications
• 600 series: Originally for proprietary alloys, this section is not generally used much anymore because such alloys are not given SAE grade numbers today
• 900 series: Austenitic chromium-molybdenum alloys, similar to the 300 series but with better corrosion resistance

For more on the various grades of steel under the SAE grading system, or to learn about any of our steel bar, steel tube or numerous other steel products, speak to the staff at Wasatch Steel today.