超超临界转子用钢的镍铬当量比对δ-铁素体析出的影响

采用真空感应炉熔炼不同镍铬当量比的超超临界转子用钢锭,分析镍铬当量比对δ-铁素体析出的影响。研究表明:标准成分范围内铸锭中析出的δ-铁素体是由于冷却过程中非平衡相变引起的,高镍铬当量比的铸锭偏析较轻,δ-Fe呈小块状分布,通过再结晶和热挤压可以被完全吸收;低镍铬当量比的铸锭偏析加重,δ-铁素体含量明显增多,呈网状分布,热加工后呈链条状分布在晶界位置,很难将其完全消除;随镍铬当量比的提高,δ-铁素体含量减少,合金冲击韧性明显改善。

Effect of Nickel Chromium Equivalent Proportion in Ultra-Supercritical Rotor Steel on Precipitation of ��-Ferrites

Different nickel chromium equivalent proportion ultra-supercritical rotor steel ingots were melted by vacuum induction furnace to research the effect of nickel chromium equivalent proportion on precipitation of ??-ferrites. The investigation shows that the precipitation of ??-ferrites is caused by the non-equilibrium phase transformation during cooling of ingots although the composition of alloy is in the standard scope. ??-ferrites were nubby in the cast ingot with high nickel chromium equivalent proportion, and they could be absorbed through recrystallization and extrusion during forging and heat treatment. The quantity of ??-ferrites increased and they were netlike in cast ingot when the nickel chromium equivalent proportion decreased. ??-ferrites became catenulate at grain boundary after forging and heat treatment, and they were difficult to remove. With the nickel chromium equivalent proportion increasing, the impact toughness was improved significantly.