Carbon Steel Bar - Flat bar, Hex bar, Round bar, Square bar Carbon steel bar is stocked in flat, hex, round and, square at Future Metal. Carbon steel is ideal for many industrial products and applications where strength and durability are required. Characteristics of carbon steel bars are based on the carbon content. Increased carbon content will raise carbon steel’s hardness and strength. Inversely, lower carbon content results in a softer (mild) carbon steel that is easier to machine and weld. The type of carbon steel needed is generally based on the application requirements. What Are the Different Types of Carbon Steel? Carbon steel is divided into three main groups as follows: low carbon = .06% to .25% carbon content (mild steel) medium carbon = .25% to .55% carbon content (medium steel) high carbon = >.55% to 1.00% carbon content (hard steel) Carbon Steel Bar Available in Multiple Grades 10XX = non-resulpherized carbon steel, with manganese 1.00% maximum (for example 1018, 1044, 1045 and 1050). 11XX = resulpherized carbon steel (for example 1117, 1141, 11L17, and 1144). 12XX = rephosphorized and resulpherized carbon steel (for example 12L14 and 1215).