Effects of Austempering on Microstructure and Mechanical Properties of the Low Carbon Ductile Iron
In this paper,the effects of austempering on microstructure and mechanical properties of the low carbon ductile iron,under the same austenitizing(890 ℃×40 min),were investigated and the test samples were designed in two groups of chemical compositions(A and B).The results showed that after austenitizing and austempered at 340 ℃×60 min,the best mechanical properties achieved in group A was σb=1 103.98 MPa,δ=6.84%;austempered at 320 ℃×120 min,the best mechanical properties in group B was σb=1 352.58 MPa,δ=10.67%.Comparing the microstructures,it showed that the group B which was austempered at the lowest temperature was the best.Strengthened by the post inoculation after spheroidizing treatment,the level of nodularity and grade of nodular size were raised,while the graphite nodular distributed more uniformly.