利用扫描电镜(SEM)结合能谱仪(EDS)分析研究了非金属夹杂物对620℃等级超超临界汽轮机用CB2耐热铸钢冲击性能的影响.结果表明,CB2铸钢的冲击吸收能量平均值为36.0 J,冲击断口为典型的脆性断口.钢中的夹杂物主要为角状的Al2O3、不规则的氮化物-氧化物复合夹杂和白色的铬钼相.Al2O3夹杂物和氮化物-氧化物的尺寸在5～10μm,数量较多,铬钼相单个尺寸在10 μm左右,聚集分布并呈链状.通过改进CB2铸钢的冶炼工艺,改善了铸钢中非金属夹杂物的水平,使冲击吸收能量提高到了59.3 J,从而提升了CB2铸钢件在超超临界汽轮机中的使用性能,为实现CB2铸钢的自主生产提供了参考.
The influence of non-metallic inclusions on the impact property of CB2 heatresistant cast steel for 620 ℃ ultra supercritical steam turbines was studied by using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).The results showed that the fracture for CB2 cast steel was a typical brittle fracture and its average impact absorption energy was measured to be 36.0 J.The main inclusions in CB2 cast steel included horn-shaped Al2O3,irregular composite nitrideoxides and white chromium molybdenum phases.The sizes of Al2O3 inclusions and nitride-oxides ranged from 5 μm to 10 μm,they were existed in great numbers.The chromium molybdenum phases were about 10 μm in size,and gathered together like chain.The level of non-metallic inclusion in CB2 cast steel was optimized effectively by improving smelting process,and the average impact absorption energy was increased to 59.3 J.These measures improved the application performance of CB2 cast steel in the ultra supercritical steam turbine and gave a reference to realization of the independent production of CB2 steel.
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