The heat-treatment characteristics,mechanical properties,and wear behavior of four cold-forged-roll steels were studied and their microstructural characteristics were analyzed using transmission electron microscopy(TE...The heat-treatment characteristics,mechanical properties,and wear behavior of four cold-forged-roll steels were studied and their microstructural characteristics were analyzed using transmission electron microscopy(TEM),scanning electron microscopy(SEM),X-ray diffractometer(XRD),and an oxygen-nitrogen analyzer.The results show that the introduction of nitrogen facilitates improvement in the mechanical properties of cold-forged rolls.A solid-solution strengthening effect is obtained by interstitial nitrogen,and the hardenability of rolls can be improved as well.A significant effect on grain-size refinement is obtained by highly thermally stable fine M(C,N)carbonitrides,which pin the grain boundaries during austenitization and block the growth of austenitic grains.Compared to conventional roll steels,the optimum quenching temperature of steel with added nitrogen can be increased by 20-30℃ Therefore,the hardening temperature range is expanded,which is beneficial to the heattreatment process.Furthermore,high-hardness carbonitrides can improve the wear performance.展开更多
The deformation and densification laws of preform upsetting and closed-die forging were researched based on experimental results of cold forging of deoxidized Fe powder sintering porous material under different initia...The deformation and densification laws of preform upsetting and closed-die forging were researched based on experimental results of cold forging of deoxidized Fe powder sintering porous material under different initial conditions such as friction factor, ratio between height and diameter and relative density. The fracture limit criteria＂ for powder cold-forging upsetting and the limit strain curve were achieved. The effect of friction facto,, ratlt, between height and diameter and relative density on fracture strain limitation was emphatically analyzed. The limit process parameter curves for the deformation of upsetting were also confirmed. Laws of deformation, densification and density distribution for closed-die forging of powder perform during cold-forging were further analyzed and discussed with the help of experimental phase analysis. As a result, this experiment established theoretical foundations for the design of preform and die as well as optimization of technological process parameters.展开更多
文摘The heat-treatment characteristics,mechanical properties,and wear behavior of four cold-forged-roll steels were studied and their microstructural characteristics were analyzed using transmission electron microscopy(TEM),scanning electron microscopy(SEM),X-ray diffractometer(XRD),and an oxygen-nitrogen analyzer.The results show that the introduction of nitrogen facilitates improvement in the mechanical properties of cold-forged rolls.A solid-solution strengthening effect is obtained by interstitial nitrogen,and the hardenability of rolls can be improved as well.A significant effect on grain-size refinement is obtained by highly thermally stable fine M(C,N)carbonitrides,which pin the grain boundaries during austenitization and block the growth of austenitic grains.Compared to conventional roll steels,the optimum quenching temperature of steel with added nitrogen can be increased by 20-30℃ Therefore,the hardening temperature range is expanded,which is beneficial to the heattreatment process.Furthermore,high-hardness carbonitrides can improve the wear performance.
基金Supported by the National Natural Science Foundation of China (No.50175086)
文摘The deformation and densification laws of preform upsetting and closed-die forging were researched based on experimental results of cold forging of deoxidized Fe powder sintering porous material under different initial conditions such as friction factor, ratio between height and diameter and relative density. The fracture limit criteria＂ for powder cold-forging upsetting and the limit strain curve were achieved. The effect of friction facto,, ratlt, between height and diameter and relative density on fracture strain limitation was emphatically analyzed. The limit process parameter curves for the deformation of upsetting were also confirmed. Laws of deformation, densification and density distribution for closed-die forging of powder perform during cold-forging were further analyzed and discussed with the help of experimental phase analysis. As a result, this experiment established theoretical foundations for the design of preform and die as well as optimization of technological process parameters.
