Nb合金化对高Cr铸铁轧辊组织的影响

Effect of Nb alloying on microstructure of high-Cr cast iron rolls

微合金化是细化高Cr铸铁轧辊的凝固组织、提高轧辊的性能和使用寿命重要手段。研究了Nb微合金化对高Cr铸铁轧辊组织和硬度的影响,并采用Thermo-Calc软件分析了Nb对高Cr铸铁凝固组织的细化机制,结果表明,Nb合金化能够显著细化高Cr铸铁的轧辊的凝固组织,提高轧辊的硬度。Nb微合金化对高Cr铸铁的组织改善作用取决于MC型碳化物析出温度及其对奥氏体和共晶M_(7)C_(3)碳化物的形核的促进作用。当Nb质量分数为0.5%时,高Cr铸铁轧辊硬度最大;进一步提高Nb含量能显著细化高Cr铸铁轧辊组织,但使硬度降低。

Microalloying is an important method to refine the solidification microstructure and improve the mechanical properties and service life of high-Cr cast iron rolls.The effect of Nb microalloying on the microstructure and hardness of high-Cr cast iron was studied.Meanwhile,the refining mechanism of Nb on the solidification microstructure of high-Cr cast iron was analyzed by Thermo-Calc software.The results show that Nb microalloying can significantly refine the solidification microstructure and improve the hardness of high-Cr cast iron rolls.The improving of Nb microalloying on microstructure of high-Cr cast iron depends on the precipitation temperature of MC type carbide and its promotion of nucleation for austenite and eutectic M_(7)C_(3)carbides.As Nb mass fration is 0.5%,the hardness of high-Cr cast iron rolls is the highest.Further increase of Nb content can significantly refine the microstructure of high-Cr cast iron rolls,but reduce the hardness.