水电站座环及导叶用钢SXQ500/550DZ35热力学计算及析出相分析

水电建设的发展，对水电站座环及导叶用SXQ500/550DZ35特厚板的性能提出了更高的要求，其成分中加入合金元素多，各种相的析出复杂，而析出相与钢的组织性能密切相关，因此利用Thermo Calc软件对SXQ500/550DZ35水电用钢进行了热力学计算及平衡相分析。结果表明，FCC_A1#2、FCC_A1#3及FCC_A1#4相析出温度区间集中于900~1 400 ℃之间，属于微合金元素V、Nb、Ti与C、N元素结合生成的碳化物以及碳氮化物，其能钉扎奥氏体晶界，细化奥氏体晶粒。通过钢板在970、1 020、1 070 ℃保温22 min后水淬至常温，并采用场发射电镜对其进行检测，析出相主要为NbC、TiC、Ti（C,N），与热力学软件计算相符合。

Thermodynamic calculation and precipitation phase analysis of SXQ500/550DZ35 steel for seat ring and guide vane of hydropower station

With the development of hydropower construction,the performance of SXQ500/550DZ35 heavy thickness plate for stay ring and guide vane of hydropower station is put forward higher requirements.There are many alloy elements in its composition,and the precipitation of various phases is complex,while the precipitation phase is closely related to the structure and performance of steel.Therefore,Thermo-Calc software is used to carry out thermodynamic calculation and equilibrium phase analysis of SXQ500/550DZ35 steel for hydropower station.The results show that the precipitation temperature range of FCC_ A1#2、FCC_A1#3 and FCC_A1#4 A1 is between 900 ℃ and 1 400 ℃,which belongs to carbides and carbonitrides formed by the combination of V,Nb,Ti and C,N elements,which can nail austenite grain boundaries and refine austenite grains.Through the test,the plates were water quenched to normal temperature at 970,1 020,1 070 ℃,and the field emission electron microscope was used to detection its microstructure.The results show that the main precipitates are NbC,TiC and Ti (C,N),which are consistent with the calculation of thermodynamics software.