A36 Steel: A Grade Guide

The global market for structural steel is enormous, valued at 100 billion dollars USD yearly. It’s easy to see why steel is such an appealing choice for construction due to its qualities: high strength, toughness, formability and ease in welding. And among the many types of structural steels, grade A36 stands above the crowd.

Key Attributes of A36 Steel

A36 is a low carbon steel, which means its composition contains less than 0.3% carbon by weight. At its most basic, steel is formed when alloying iron with carbon. Carbon grants more strength and hardness to the alloyed metal in comparison to pure iron. However, as the percentage of carbon in the steel grows larger, the hardness can become brittle. That same hardness also produces steel with lower ductility and less workability.

In contrast, low carbon steels like A36 are relatively soft and not quite as strong compared to other steels. But their greatest attribute is ductility: that same softness means low carbon steel is much more formable and malleable. This makes low carbon steel an excellent choice for machining and welding. So it’s not surprising to learn that this category is the most widely used type of carbon steel – and A36 is the most utilized type of low carbon steel.

A36 steel is unique in its grading: unlike many other steels whose number is determined by their chemical composition, A36 is designated by its mechanical properties. What this means is that most grades have alloys that must be added in specific percentages in order to qualify as that steel type; meanwhile, A36 steel must meet the set mechanical standards for its grade. So while it does need to conform to certain chemical composition standards, the most important characteristic of A36 steel as established by ASTM International is its yield strength. In order to be graded as A36, the steel must meet a minimum yield strength requirement of 36,000 pounds per square inch. The metal must be able to withstand that amount of pressure with only 0.2% or less deviation to its shape under stress.

A36 is also a relatively ductile steel, able to elongate to around 20% of its original length during tensile testing. Along with its yield strength, this ductility gives A36 steel a high degree of impact strength at room temperature. This toughness helps prevent the metal from fracture and other damage.

Uses for A36 Steel

As you might tell from its attributes, A36 is quite a versatile material. It comes in a variety of shapes suited for riveted, bolted, and welded construction. Many of these shapes are designed for structural applications such as bridges and buildings. Wide flange beams (shaped like an “H”) are used as columns or beams. Tee bars (formed in a “T” shape) can be found used as beams or bracing. Angles are generally used as bracing or finishing elements. However, its uses are not limited to large construction projects. The versatility of A36 steel lends itself to other uses such as ship building, heavy equipment manufacturing, and automotive parts.  Whatever its purpose, it’s clear why grade A36 steel is so popular: tough, strong, easily welded…and all this at a relatively low cost!