Microstructure And Properties Of 2115 Hot Rolled Plate Of Non-magnetic Stainless Steel

With the rapid development of national defence industry and transportation in key areas,the demand for producing non-magnetic steel is more and more urgent.As the great parts of precision instrument and special equipment manufacturing,they have high requirement of mechanical properties,nonmagnetic,welding and corrosion resistance,so it is urgent to develop the Cr-Ni nonmagnetic stainless steel.In this paper,the OCr21Ni15(referred to as 2115)steel which is called high Cr-Ni non-magnetic stainless steel is studied.The high temperature compression thermal simulation experiment,hot rolling,solution treatment and room temperature tensile test are conducted in this article.The microstructure is investigated by optical microscopy(OM),scanning electron microscopy(SEM)as well as TEM,the results are as follows:(1)By the high temperature uniaxial compression tests,The hot deformation behavior and microstructure evolution were studied with experimental deformation temperature of 900?1150?and strain rate of 0.1?10s-1.The research showed that under the high-temperature,low strain rate and large deformation,dynamic recrystallization occured easily;the thermal deformation activation energy is 663.48KJ/mol,and the values for each parameter Z in different deformation conditions;in addition,the establishment of deformation resistance model were done,providing a theoretical reference for the actual hot rolling.(2)After hot rolling with different processes,the microstructure evolution was studied by OM and SEM,the macro-hardness and tensile properties were also conducted.The microstructure of 2115 steel after hot rolling is full of deformed austenite.Grain distributions are uneven.The smaller degree of deformation can be obtained when hot rolling with a higher ultimate temperature and a higher cooling rate.In hot rolling process,the recovery is leading,with partial dynamic recrystallization,leading to high dislocation density.so it requires high-temperature annealing to improve the organization and performance.The yield strength is 792MPa and tensile strength is 980MPa,and the elongation is 30%.Fracture analysis results show that that the tensile tested sample exhibits ductile fracture.(3)Carry out the study on the microstructure evolution of 2115 steel in different solution treatment,and tensile properties and macro hardness of 2115 are investigated in this section.The results showed that in the range of 850?1200?,with the temperature increasing,the deformed grains are gradually eliminated after plastically deformed,tissues are gradually homogeneous and carbides are fully dissolved.The finest grains of 2115 steel are obtained after annealing at the temperature of 1050? with 12min.After solution at 1050?,The yield strength is 580MPa and the tensile strength is 889MPa,and the elongation is 42%.The permeability of the steel is 1.0021.(4)The samples were aged at different temperature(500-650?)under different holding time(4-14h),the second phase were found to be precipitated along the grain boundary and in the intragranular.And the fraction of second phase was increased at first and decreased afterwards with the increasing of aging temperature,reaching the peak at 600?.But it was always increased with the increasing of the holding time.The dispersed second phase gradually grew up together,and continued to coarsen,rod-shaped,granular and so on.The precipitated phase contains higher Nb elements,so it can be deduced that these phases are NbC and Cr23C6 by TEM images,in addition the precipitated phase is tended to enrichment at grain boundaries.After aging treatment,the yield strength and the tensile strength are improved to 20-50MPa,while the elongation changes a little.The permeability of the steel is 1.0025 after aging.