| Due to its non-magnetic and corrosion-resistant properties,non-magnetic stainless steel is commonly used to manufacture the structural component of special equipment.With the rapid development of China's equipment technology,the processing capacity of advanced equipment has become stronger,and the demand for raw materials has became higher and higher.However,The performance of traditional non-magnetic stainless steel has been unable to meet the design needs.In this paper,a Cr-Ni-Mn-Al-Ti non-magnetic stainless steel(abbreviated as 211 5A experimental steel)was designed for manufacturing special ships.The hot deformation behavior of 2115A experimental steel was studied through high temperature compression thermal simulation experiment.The changes in organization and performance durning heat treatment of 2115A experimental steel were investigated through hot rolling,solution treatment and aging treatment experiments by microstructure analysis(SEM,EPMA,EDS,TEM)and mechanical properties tests(hardness test,tensile test,low temperature impact test).The main original works of this thesis are presented as follows:(1)By high temperature uniaxial compression tests,the hot deformation behavior of 2115A experimental steel during high temperature compression was investigated with experimental deformation temperature of 950?1150? and strain rate of 0.1?10s-1.The flow stress curve of 2115A experimental steel was measured,and the microstructure evolution of 2115A experimental steel during high temperature compression was studied.The thermal deformation activation energy is 663.48KJ/mol.The high temperature constitutive equation of 2115A experimental steel was established and the mathematical model of deformation resistance was regressed,which provides a theoretical reference for the actual hot processing.(2)Carry out the study on the microstructure of 2115A experimental steel after hot rolling and different solution treatment,and the mechanical properties were tested.The microstructure after hot rolling was single phase austenite,which the size and uniformity of the grain depended on the deformation of different positions.The yield strength of the hot-rolled plate is 816MPa,the tensile strength is 1053MPa,and the elongation is 19.7%.In the range of solution treatment temperature from 1020 to 1120?,with temperature increasing,the grains becamed fine and uniform first,and then grew sharply.With the increase of the holding time,the static recrystallization was sufficient,and then the grains grew slowly.When the holding time was too long,there would be a large number of precipitation phases on the grain boundary.It was the best solution treatment process that annealing at the temperature of 1060? with 2 hours.After optimal solution treatment,the yield strength is 385MPa,the tensile strength is 695 MPa,and the elongation is 46%.(3)The second phase precipitation law of 2115A experimental steel after different aging treatment was investigated.With the increase of aging temperature and time,The second phase preferentially grew from the grain boundary and then dispersed in the grains.When the temperature was too high or the aging time was too long,it grew again at the grain boundary.The main components of the bulk second phase in the aged structure were TiC and NbC,which were formed during the smelting process and could not dissolve in the solution and aging treatment.The main component of the fine precipitates on grain boundaries and in the grains was Ni3Ti.(4)At the same aging time,with aging temperature increasing,the hardness of 2115A experimental steel showed a trend of rising first and then decreasing.At the same ageing temperature,the hardness,tensile strength and yield strength of 2115A experimental steel increased first and then decreased with aging time,while the elongation and impact toughness continued to decline.Comprehensively considering the strength,plasticity and toughness,annealing at the temperature of 750? with 4 hours was the best aging treatment process.After optimal aging treatment,the yield strength is 655MPa,the tensile strength is 910 MPa,the elongation is 29.2%,and the impact toughness at-20? is 92J·cm-2.The relative permeability of the 2115 A experimental steel after optimal aging treatment is 1.0068,which is in accordance with the requirement of non-magnetic stainless steel.The precipitation phase appeared during the aging process does not affect the non-magnetic properties of the experimental steel. |
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