The hardness and residual stress in the forging for cold roller during low temperature tempering,and the relationship of residual stress and cooling temperature of high temperature tempering for heavy forgings were st...The hardness and residual stress in the forging for cold roller during low temperature tempering,and the relationship of residual stress and cooling temperature of high temperature tempering for heavy forgings were studied.The stress relaxation constant at low temperature tempering and the elasto-plastisity inversion temperature at high temperature tempering were found.The results are of great importance to determine rational tempering cooling process of heavy forgings.展开更多
A whole analysis model including forging and flat platens is built,which is used to analyse the process of upsetting a cylinder between flat platens.The influence of surface friction and transient temperature are comp...A whole analysis model including forging and flat platens is built,which is used to analyse the process of upsetting a cylinder between flat platens.The influence of surface friction and transient temperature are comprehensively considered.By means of ANSYS software,the elasto plastic FEM analysis of the whole upsetting process is carried out.From the point of view of numerical calculation,the correctness of the centre region tension stress theory about upsetting a cylinder between flat platens is tested and verified.The concept of plasto nucleus is presented to explain the forming of double dumps.The efffect of temperature is inspected.The relation curves between the radial stress of the symmetry centre point and the relative pression ratio are given.展开更多
While relationship between fracture mechanism and homogeneous microstructures has been fully understood,relationship between fracture mechanism and inhomogeneous microstructures such as the mesosegregation receives le...While relationship between fracture mechanism and homogeneous microstructures has been fully understood,relationship between fracture mechanism and inhomogeneous microstructures such as the mesosegregation receives less attention as it deserves.Fracture mechanism of the high-strength low-alloy(HSLA)steel considering the mesosegregation was investigated and its corre s ponding micro structure was characterized in this paper.Mesosegregation re fers to the inhomogeneous distribution of alloy elements during casting solidification,and leads to the formation of positive segregation zones(PSZ)and negative segregation zones(NSZ)in ingots.The fracture surface of impact sample exhibits the quasi-cleavage fracture at-21℃,and is divided into ductile and brittle fracture zone.Meanwhile,the PSZ and NSZ spread across ductile and brittle fracture zone randomly.In ductile fracture zone,micro-voids fracture mechanism covers the PSZ and NSZ,and higher deformation degree is shown in the PSZ.In brittle fracture zone,secondary cleavage cracks are observed in both PSZ and NSZ,but present bigger size and higher quantity in the NSZ.However,some regions of the PSZ still present micro-voids fracture mechanism in brittle fracture zone.It reveals that the microstructures in the PSZ exhibit a higher resistance ability to crack propagation than that in the NSZ.All observations above provide a better visualization of the microstructural factors that resist the crack propagation.It is important to map all information regarding the fracture mechanism and mesosegregation to allow for further acceptance and industrial use.展开更多
文摘The hardness and residual stress in the forging for cold roller during low temperature tempering,and the relationship of residual stress and cooling temperature of high temperature tempering for heavy forgings were studied.The stress relaxation constant at low temperature tempering and the elasto-plastisity inversion temperature at high temperature tempering were found.The results are of great importance to determine rational tempering cooling process of heavy forgings.
文摘A whole analysis model including forging and flat platens is built,which is used to analyse the process of upsetting a cylinder between flat platens.The influence of surface friction and transient temperature are comprehensively considered.By means of ANSYS software,the elasto plastic FEM analysis of the whole upsetting process is carried out.From the point of view of numerical calculation,the correctness of the centre region tension stress theory about upsetting a cylinder between flat platens is tested and verified.The concept of plasto nucleus is presented to explain the forming of double dumps.The efffect of temperature is inspected.The relation curves between the radial stress of the symmetry centre point and the relative pression ratio are given.
基金This work was financially supported by the National Natural Science Foundation of China(No.51801126).
文摘While relationship between fracture mechanism and homogeneous microstructures has been fully understood,relationship between fracture mechanism and inhomogeneous microstructures such as the mesosegregation receives less attention as it deserves.Fracture mechanism of the high-strength low-alloy(HSLA)steel considering the mesosegregation was investigated and its corre s ponding micro structure was characterized in this paper.Mesosegregation re fers to the inhomogeneous distribution of alloy elements during casting solidification,and leads to the formation of positive segregation zones(PSZ)and negative segregation zones(NSZ)in ingots.The fracture surface of impact sample exhibits the quasi-cleavage fracture at-21℃,and is divided into ductile and brittle fracture zone.Meanwhile,the PSZ and NSZ spread across ductile and brittle fracture zone randomly.In ductile fracture zone,micro-voids fracture mechanism covers the PSZ and NSZ,and higher deformation degree is shown in the PSZ.In brittle fracture zone,secondary cleavage cracks are observed in both PSZ and NSZ,but present bigger size and higher quantity in the NSZ.However,some regions of the PSZ still present micro-voids fracture mechanism in brittle fracture zone.It reveals that the microstructures in the PSZ exhibit a higher resistance ability to crack propagation than that in the NSZ.All observations above provide a better visualization of the microstructural factors that resist the crack propagation.It is important to map all information regarding the fracture mechanism and mesosegregation to allow for further acceptance and industrial use.
