Influences of Manganese on Internal Friction and Carbon Solubility Determined by Combination of Infrared Absorption in Ferrite of Low-carbon Steels

The influence of Mn on the solubility of C in ferrte in equilibrium with cementite was investigated in low-carbon steels containing Mn rangeing from 0 to 1 mass% over the temperature range from 573 to 973 K. The internal friction method was employed together with chemical analysis of C by means of infrared absorption after combustion. It has been clarified that Mn hardly changes the solubility of C in ferrite in equilibrium with cementite (about 0.018 mass% at 973 K), whereas Mn reduces the Snoek peak height despite the fact that the amount of C in solid solution is constant. The proportionality constant K in the equation, Sol. C (mass ppm)=K×Q-1max·(10-4), was experimentally determined as a function of the Mn content. K increases with increase in Mn content; this is speculated to be caused by the lattice strain introduced by Mn atom and/or the chemical interaction between Mn and C atoms.