Effect of cooling speed on solidification segregation in 20MnCr5 gear steel
Gear steel,as a key material in aerospace,railroad transportation and mechanical transmission,its per-formance directly affects the service life and reliability of gears.Aiming at the properties deterioration problem of gear steel due to banded organization during solidification at lower cooling rates,the microstructure and microseg-regation behavior of solute elements of 20MnCr5 gear steel at different cooling rates were investigated by a combina-tion of experimental and theoretical calculations using in-situ laser confocal scanning microscopy(CLSM),electron probe X-ray microanalysis(EPMA),and JMatPro software.The results show that the secondary dendrite arm spacing decreases from 318.63 μm to 138.08 μm with the acceleration of the cooling rate.During the solidification process of 20MnCr5 gear steel,the phase transformation of L→L+δ→γmainly occurs.With the decrease of tem-perature,chromium and manganese elements have a tendency to be polarized at the grain boundaries,while MnS,TiN and carbides are precipitated successively.A microscopic segregation model of solute elements is constructed to predict the segregation behavior of elements in the solidification process of gear steel,and the results are consistent with the distribution of elements in the EPMA surface sweep,which provides a basis for the optimal control of the continuous casting process and the quality control of billet casting.
gear steelin-situ observationsolidification microstructurecooling ratesegregation model
NETL
NSTL
万方数据
