A36 steel is a common structural steel alloy used in building construction, furniture fabrication and pipe manufacturing. A36 is a low-carbon steel alloy, meaning it contains a relatively small percentage of carbon relative to iron. Like other low-carbon steels, A36 is relatively easy to machine, weld and bend.
Low-carbon steel alloys are easier to weld and machine because the low ratio of carbon to iron atoms results in a product with greater ductility but lower tensile strength. In a blast furnace, molten iron gets mixed with carbon. When the iron and carbon mixture cools, carbon atoms become trapped in the crystal matrix and iron atoms naturally form. These trapped carbon atoms make it more difficult for the entire crystal matrix to move, resulting a harder material. The more carbon atoms trapped in the matrix, the harder the steel.
A36 steel is very similar to 1018 steel, with the primary differences being A36's slightly higher carbon content and the fact while A36 is hot-rolled, 1018 is cold-rolled. Manufacturers form hot-rolled steel into sheets at very high temperatures by passing it through huge, heavy metal rollers that gradually reduce the steel to the desired thickness. Steel companies make cold-rolled steel in much the same way, but at normal temperatures. Because heating steel reduces its tensile strength, hot-rolling is cheaper and faster than cold-rolling, but it results in a less attractive sheet with a rough, uneven surface.