You may notice there are different numbers surrounding the materials on the website here. Most of this will not matter to the everyday fabricator or garage builder, however, they are important for certain applications. We stock both ASME and AISI/SAE grade materials for certain shapes of bar stock and most others, will be ASME certified.
Differences in materials can come down to application. SAE/AISI is the grouping of 4 numbers behind the material size and description, typically 1018 or 4140 for our stock. These numbers represent certain qualities of the material including the alloying elements and how much carbon has been added. The table here shows that the first number represents alloying elements in the steel. This shows 1018 is carbon steel and 4140 is a molybdenum alloy. The next numbers represent any changes to the material and they are specific to the first number. For 1018 there are no other elements added to the material than that of the standard steel, for 4140 there is Chromium added to make a chrome molybdenum alloy.
The last two numbers represent the carbon content of the steel to hundredths of a percent (.18% and .40%). These numbers will correlate to the hardness and 1018 is on the end of Mild steel whereas 4140 is a Mid-grade hardness. When looking for material to machine or potentially heat treat these numbers will be a major factor in the purchase.
For the ASME designations, all our square tubing, flat bar, channel, beam, or angle comes as A36 or 44W/50W. These grades are used in virtually all structural applications with few exceptions.
You can buy our steel in confidence that you are receiving a high-quality product made from a high-quality mill.