| 254SMO super austenitic stainless steel is widely used in seawater desalination,chemical industry,flue gas desulfurization and other strong corrosive environment,but its application is limited by its poor thermal deformation performance,high deformation resistance and great difficulty in field production.In this study,the deformation behavior of254SMO super austenitic stainless steel at high temperature and the dissolution behavior of original as cast structure at high temperature are studied,which provides theoretical basis for field production.In this study,the Gleeble-3500c thermal simulation experiment machine was used to test the temperature at 950°C?1250°C.The hot compression deformation behavior of 254SMO super austenitic stainless steel was measured in the strain rate range of 0.1 s-1-20 s-1.High temperature heat treatment furnace was used to test the quality of billet at 1220??1280?.The effects of different heat treatment temperatures on the microstructure and precipitates of as cast alloy were investigated.The effects of homogenization treatment conditions on as cast microstructure of 254SMO were studied by homogenizing 254SMO at different temperatures and holding times.Through the analysis of Cr equivalent and Ni equivalent,when Creq/Nieq<1.25,it is confirmed that the crystallization path is L?L+???,Finally,a single austenite phase is formed.In the process of the experiment,the samples of the center and edge of the slab were selected,and the samples of the center were tested by 1280°C×9 h homogenization treatment.Different samples were tested at 950°C?1050°C?1150°C?1250°C.1 s-1,1 s-1,10s-1,20 s-1.Based on the hyperbolic sine model proposed by Sellars and tegart,the constitutive equation of 254SMO super austenitic stainless steel under uniaxial compression was established.The constitutive equation of sample No.1 is as follows?=1.24030×1038[sinh(0.00332?)]10.490exp(-918.57/RT)The constitutive equation of sample 2 is as follows?=1.42853×1028[sinh(0.00390?)]7.221exp(-764.85/RT)The constitutive equation of sample 3 is as follows?=8.56940×1027[sinh(0.00488?)]6.930exp(-647.67/RT)The results show that the microstructure of as cast at room temperature is all austenite with a small amount of precipitates.There is obvious dendrite structure in the as cast structure,the dendrite structure in the center is coarse,and the secondary dendrite spacing is 100?m.The secondary dendrite spacing is 25?m.The average secondary dendrite spacing is 35.5?m.It shows that the cooling rate decreases from the edge to the center,and the secondary dendrite spacing increases.After homogenization treatment at 1220?and 1250?.The results of homogenization treatment of 254SMO at different temperature and time show that a small part of the original as cast dendrite structure is eliminated,while the precipitates are almost insoluble.At 1280?,after homogenization for 6 h and 9 h,the dendrite structure is almost completely eliminated and the precipitates are almost completely dissolved.The mechanisation of?-phase disoluton was received from backscarttered electron test.With the homogenization process going on,?-phase gradually dissolves and transforms into Ferrite.The constitutive equation of the alloy was obtained by hot compression experiments at different temperatures and strain rates.After homogenization treatment,the Q and N values of the core sample are the lowest,and the deformation's difficulty is the lowest.The Q and N values of the edge sample are the highest,and the deformation's diffculty is the highest.The Z value of the edge sample is the largest and the recrystallization trend is the highest,while the Z value of the center sample is the lowest and the recrystallization trend is the smallest. |
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