Influence Factors on σ-Phase Precipitation of FeCr16 Corrosion-resistant Soft Magnetic Alloy

In order to investigate the influencing factors of the precipitation of σ phase in the solidification structure of FeCr16 corrosion-resistant soft magnetic alloy during electroslag remelting process， a series testes has been conducted to study the solidification process and precipitation of FeCr16 corrosion-resistant SMA （Soft Magnetic Alloy） from 1 600 ℃ to 1 400 ℃ at different cooling rates of 5， 10， 20 ℃/min by using 1 LM21H-SVF17SP LSCM （Laser Scanning Confocal Microscopy）. Meanwhile combining with thermodynamic calculation via JMatPro software， the relationship between segregation of Cr and σ-phase precipitation was studied. In addition， the test was performed with different melting rates during ESR process ， and the relationship between σ-phase precipitation and ESR speed was also investigated. The results showed that while the cooling rate of solidification was low， the segregation degree of Cr element in the alloy was relatively high. With the increase of cooling rate， the maximum segregation rate and average segregation rate of Cr element both decreased； The segregation of Cr element provided favorable kinetic conditions for the precipitation of σ-phase. The higher ESR speed was， the slower the solidification rate， the higher the segregation， the more easily the σ-Phase precipitated. When ESR speed was set as 3.5 kg/min-4.5 kg/min， no σ Phase was found in the microstructure of ESR ingot after heat treatment， while the ESR speed was adjusted to 5.0 kg/min-6.0 kg/min， σ-Phase precipitation was detected. The optimal ESR speed was 3.5 kg/min-4.5 kg/min.