The Effect of Total Carbon and Manganese on the Mechanical Properties and Structure of Welded Joints in Plain Low-Carbon Steel,

Maganese is one of the alloying elements in steel that promote air hardening. That is, manganese lowers the critical cooling speed required to produce martensite. Air hardening in welds is usually dangerous because the air-hardened region is brittle and because the low-temperature martensite expansion favors cracks. The present review of literature was begun in the hope that a study of all published experimental work on the mechanical properties and microstructure of welds in plain carbon-manganese steels might reveal that there were critical ratios of carbon to manganese in the weld and base metal that could be depended upon to lead to air hardening or brittleness under given welding conditions. For brittleness may be induced in welded joints by other factors than air hardening, for example, nitrides and coarse grain structure. It is not unexpected that welds in steels containing high manganese and carbon have higher tensile strengths than low-carbon, low-manganese welds. Undoubtedly, differences in welding procedures among the investigators account for the differences in mechanical properties rather than differences in carbon and manganese content. No comprehensive investigation has been made of the effect of different combinations of carbon and manganese on the mechanical properties of welds.