Research On High Temperature Thermal Deformation Behavior Of Domestic P92 Steel Pipe

P92 thick-walled seamless steel pipe is a new type of ferritic heat-resistant steel.At present,the manufacturers represented by Inner Mongolia North Heavy Industry Group all adopt the hot extrusion method to produce P92 steel.The P92 steel has been researched and developed for many years in my country.But there is still a certain gap between domestic P92steel and foreign P92 steel,and the output of domestic P92 steel cannot fully meet the market demand.This paper studies the high-temperature thermal deformation behavior of domestic P92 thick-walled seamless steel pipes.Which can provide a theoretical reference for optimizing the production process parameters of domestic P92 steel,shortening the research and development cycle,and improving product quality and competitiveness.First,use a thermal simulation testing machine to conduct high-temperature thermal compression deformation experiments on domestic P92 steel,draw the true stress-strain curve of domestic P92 steel,reveal the influence of deformation temperature and strain rate on high temperature thermal deformation behavior of materials.Then,based on the true stress-strain curve of domestic P92 steel,the Z parameter is introduced to calculate the constitutive equation of domestic P92 steel under different strain conditions.Secondly,based on the dynamic material model,the thermal processing map of domestic P92 steel is calculated and drawn.And the processing safety zone and rheological instability zone of domestic P92 steel under different strain conditions are obtained.Finally,the microstructure of domestic P92steel under different deformation parameters is observed and analyzed.Comprehensive analysis of the constitutive equation,thermal processing map and microstructure of domestic P92 steel,and further determine the range of hot processing parameters suitable for domestic P92 steel.The true stress-strain curve of domestic P92 steel under different deformation parameters shows that:at the same deformation temperature,the flow stress of domestic P92 steel increases with the increase of strain rate.For example,when the deformation temperature is850?,the strain is 0.7,if the strain rate increases from 0.01s^-1to 10s^-1,the flow stress of domestic P92 steel increases by 41.4%;at the same strain rate,the flow stress of domestic P92steel increases with the deformation temperature.However,when the strain rate is 0.01s^-1and the strain is 0.7,if the deformation temperature increases from 850?to 1250?,the flow stress of domestic P92 steel decreases by 88.56%.By calculating the constitutive equations of domestic P92 steel under the three strain conditions of peak stress,strain of 0.35 and strain of 0.7,the relationship between flow stress,deformation temperature and strain rate of domestic P92 steel is explored.Take the constitutive equation calculated under the condition of a strain of 0.7 as an example to verify it.The correlation coefficient between the flow stress predicted by the constitutive equation and the flow stress measured by the experiment is R=0.98878,indicating that the calculated value is The theoretical value is in good agreement.In this paper,the thermal processing diagrams of domestic P92 steel under different strain conditions of 0.1-1.2 are calculated and drawn.Thermal processing diagrams under different strain conditions correspond to different processing safety zones and rheological instability zones.Taking the thermal processing diagram obtained under the condition of a strain of 0.7 as an example.It can be seen that the strain rate and deformation temperature range are 0.1s^-1-0.3s^-1,1120?-1200?and 0.01s^-1-0.03s^-1,1200?-1250?and 0.01s^-1-1100?,the dissipation efficiency factor of domestic P92 steel is greater than 0.35 and the value of ?((?)) is greater than zero.It indicating that domestic P92 steel is more prone to dynamic recrystallization within this parameter range,and processing performance Better,it is not easy to produce defects such as voids and adiabatic shear bands.In the processing range where the deformation temperature is 850-1250?and the strain rate is 0.01-10s^-1,the average grain size and recrystallization volume fraction of the dynamically recrystallized grains increase with the increase of the deformation temperature and reduce with the increase of the strain rate decreases.When the strain rate is 0.01s^-1and 10s^-1,the deformation temperature increases from 850?to 1250?,the average grain size of dynamic recrystallized grains increases by 28.59?m and21.09?m,and the recrystallized volume fraction increased by 52.12%and 42.11%.When the deformation temperature is 850?and 1250?,the strain rate increased from0.01s^-1to 10s^-1,the average grain size of the dynamic recrystallized grains decreased by1.39?m and 8.89?m smaller,and the recrystallization volume fraction is reduced by2.33%and 12.34%.