Hot Deformation Behavior Of Low Carbon High Manganese Steel

The development of modern science and technology has promoted the production and use of liquefied gases,especially with the widely application of petrochemical and air separation equipment,the demand for low temperature pressure steel is increasing.At present,Aluminum Alloy,austenitic stainless steel,3-9% nickel steel and invar alloy are commonly used as cryogenic material,but all of these materials have disadvantages such as high cost,low design strength and poor welding performance,therefore,High manganese austenitic steel with low cost and good performance has attracted more and more attention.At present,the research of high manganese austenitic steel mainly concentrated in the chemical composition design,strengthening mechanism,mechanical properties and heat treatment process.However,there are few studies on its mechanical behavior and microstructure evolution during hot working,and the microstructure of the material has an important influence on the mechanical properties of the material at low temperature.Therefore,it is of great significance to study the high temperature deformation behavior of high manganese austenitic steel and obtain its thermal processing parameters,which can improve the internal structure of the material and improve the service performance of the material at low temperature.In this paper,single pass hot compression simulation experiment was carried out on Fe-35Mn-0.04 C steel steel.Variation rule of stress-strain curve of the experimental steel was studied at temperature of 800-1200℃ and strain rates of 0.01-10s-1under true strain of 0.7.The constitutive model based on the peak stress is established.Hot processing maps of the experimental steel was also obtained,and the microstructure evolution of the experimental steel was analyzed based on hot processing maps.The effects of grain refinement on the properties of the experimental steel were investigated by room temperature impact,low temperature impact and micro hardness test under different hot working conditions.The main results are as follows:(1)The effects of different deformation conditions on the flow stress of the experimental steel were analyzed through single pass hot compression test.The constitutive model based on the peak stress,the characteristic parameter model,the dynamic recrystallization kinetics model and recrystallization grain size model of the experimental steel were established.On the basis of these models,recrystallization diagram were also established and analyzed to reflect the recrystallization of the experimental steel.(2)The eight pass groove rolling experiments and 1h solid solution treatment experiments were carried out on the experimental steel,and the microhardness,room temperature impact and low temperature impact test were carried out on all specimens under hot working conditions.By analyzing the microstructure and mechanical properties of the steel under different hot deformation process,it is found that the single pass compression,solid solution treatment and rolling can refine the grain,and the mechanical properties of the experimental steel are better after the grain refinement.(3)Based on the dynamic material model and the plastic instability criterion,the hot processing maps of the experimental steel under different strain were established.The variation law of rheological instability zone during deformation was analyzed.Combined with the microstructure,the optimum parameters for hot woring of the experimental steel were obtained.