ASTM 4140 JIS SM440 DIN 42CrMo4 Carbon Alloy Solid Round Bar Round Steel
What is carbon steel used for?
Also called mild steel, it's commonly used structurally in buildings and bridges, axles, gears, shafts, rails, pipelines and couplings, cars, fridges and washing machines. High carbon steel has a much better tensile strength, used to make cutting tools, blades, punches, dies, springs and high-strength wire.