1018 Chemical Composition (%): C: 0.17 ~ 0.24 Mn: 0.70 ~ 1.00 P: ≤0.035 S: ≤0.035 Si: 0.17 ~ 0.37 Cr: ≤0.25 Cu: ≤0.25 Ni: ≤0.25 1018 is U.S. material, including his higher than manganese, and domestic 16Mn or 15Mn, 20Mn chemical composition similar, and the 20th Q235 carbon steel and almost, but he sent a lot manganese content of .10 represents a carbon-manganese steel 18 representatives carbon content.