Effect Of Cold Deformation And Solution Treatment On The Precipitation Of ? Phase In HR3C Steel

At present and in the future,coal-fired power generation still occupies an important position in the power generation field.Ultra-supercritical units are an important means for the development of China's electric power in the direction of efficient,energy-saving and environmentally friendly energy clean utilization.HR3C steel is austenitic heat-resistant steel that is widely used in ultra-supercritical units and has excellent high-temperature durability and high-temperature corrosion resistance.However,HR3C steel will precipitate?brittle phase under certain conditions.When the research team analyzed the HR3C steel produced by different companies in the early stage,it was found that there was no significant difference between the two steel components,but there were significant differences in the kinetics of?phase precipitation during the aging process.Considering the possibility of the influence of HR3C steel production process on the precipitation of?phase,this paper analyzes the effect of cold deformation and solution treatment on the precipitation behavior and brittleness of HR3C steel during long-term aging,in order to improve steel.In this paper,the hot rolled HR3C steel billet was used as the research object,and the material was cold rolled to 8%cold deformation and 50%cold deformation,and then pretreated at 1093°C,1143°C and 1193°C for 20 min.The pretreated samples were aged for a long time at 700°C and 750°C.The precipitation morphology and composition of the?phase in HR3C steel were observed and confirmed by optical microscope,scanning electron microscope and electron probe.The effect of cold deformation and solution treatment temperature on the precipitation content and kinetics of the?phase during aging of HR3C steel was analyzed by chromogenic corrosion method combined with JMA model.At the same time,the relationship between the precipitation of the second phase and the brittleness is discussed by the method of Vickers hardness measurement and impact test.The results show that the cold deformation promotes the precipitation of?phase in HR3C steel.With the increase of cold deformation,the time for precipitation of?phase is 1300 hours before aging at 750°C,and the precipitation of grain boundary M₂₃C₆ and Nb phase in the grain also has an effect.Increasing the solution treatment temperature can effectively delay the precipitation of the?phase.8%of the sample with a deformation of 1093°C after 750°C aging 1500 hours?phase precipitation content close to 1%.The sample with deformation of8%increases the solution temperature at 100°C,and the precipitation time of the?phase at700°C and 750°C is delayed by at least 1500 hours.The difference between cold deformation and solution treatment will also affect the behavior of grain boundary M₂₃C₆ and intragranular precipitation phase during aging of HR3C steel.The hardness of the sample having a deformation amount of 50%was increased in the solid solution state and the 700°C aging process as compared with the hardness of 8%of the deformation amount.The effect of solution temperature on the hardness of steel is aging 500hours ago,the higher the solution temperature is,the lower the hardness is.After 500 hours of aging,the hardness of the sample treated with high solution temperature is higher,and the precipitation of a small amount of?phase is for HR3C.The effect of steel hardness is small.The increase of cold deformation will make the impact absorption work before and after aging of the material decrease obviously.The fracture mechanism after aging changes from transgranular fracture to transgranular and intergranular mixed fracture.The precipitation of?phase after aging also promotes the expansion of the crack during the impact process.The increase of solid solution temperature will make the impact toughness of the solid solution sample better,but the impact toughness will be worse after aging,and the fracture mode is intergranular fracture.