Quite often our customers will ask us about the different types of steel we sell, and what to look for when picking steel grades, shapes and sizes. While there are many ways to categorize steel, we find it useful to break steel down into four categories (Carbon, Alloy, Stainless and Tool Steel). In this four-part blog series, (Part 2, Part 3, Part 4) we take an in-depth look at some of the most common categories of steels, what makes them different, and what to consider when deciding which type of steel is right for you. Please note that in the UK Alloy Steel is often called Engineering Steel.
According to the American Iron & Steel Institute (AISI), Steel can be categorized into four basic groups based on the chemical compositions:
There are many different grades of steel that encompass varied properties. These properties can be physical, chemical and environmental.
All steel is composed of iron and carbon. It is the amount of carbon, and the additional alloys that determine the properties of each grade.
Types of Steel can also be classified by a variety of different factors:
There are two major numbering systems used by the steel industry in North America, the first developed by the American Iron & Steel Institute (AISI), and the second by the Society of Automotive Engineers (SAE). Both of these systems are based on four digit code numbers when identifying the base carbon and alloy steels. There are selections of alloys that have five digit codes instead. In the UK the British Standards Institute (BSI) has developed British Standards (BS). The European Committee for Standardization (CEN) has the European Norm (EN) standards. Where there is are conflicting standard between BS and EN in the UK BS EN designations are used which identifies a British adoption of a EN standard.
If the first digit is a one (1) in this designation it indicates a carbon steel. All carbon steels are in this group (1xxx) in both the SAE & AISI system. They are also subdivided into four categories due to particular underlying properties among them. See below:
The first digit on all other alloy steels (under the SAE-AISI system), are then classified as follows:
2 = Nickel steels.
3 = Nickel-chromium steels.
4 = Molybdenum steels.
5 = Chromium steels.
6 = Chromium-vanadium steels.
7 = Tungsten-chromium steels.
8 = Nickel-chromium-molybdenum steels
9 = Silicon-manganese steels and various other SAE grades
The second digit of the series (sometimes but not always) indicates the concentration of the major element in percentiles (1 equals 1%).
The last two digits of the series indicate the carbon concentration to 0.01%.
For example: SAE 4140 indicates a molybdenum steel alloy, containing 1% of molybdenum and 0.40% of carbon.
Carbon Steel can be segregated into three main categories: Low carbon steel (sometimes known as mild steel); Medium carbon steel; and High carbon steel.
Low Carbon Steel (Mild Steel): Typically contain 0.04% to 0.30% carbon content. This is one of the largest groups of Carbon Steel. It covers a great diversity of shapes; from Flat Sheet to Structural Beam. Depending on the desired properties needed, other elements are added or increased. For example: Drawing Quality (DQ) – The carbon level is kept low and Aluminium is added, and for Structural Steel the carbon level is higher and the manganese content is increased.
Medium Carbon Steel: Typically has a carbon range of 0.31% to 0.60%, and a manganese content ranging from .060% to 1.65%. This product is stronger than low carbon steel, and it is more difficult to form, weld and cut. Medium carbon steels are quite often hardened and tempered using heat treatment.
High Carbon Steel: Commonly known as “carbon tool steel” it typically has a carbon range between 0.61% and 1.50%. High carbon steel is very difficult to cut, bend and weld. Once heat treated it becomes extremely hard and brittle.
Part 1: The Four Types of Steel
Part 2: Carbon Steel
Part 3: Alloy Steel
Part 4: Stainless Steel
Part 5: Tool Steel
For more information Steel Manufacturer, please get in touch with us!