The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lam...The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lamellae and ferrite recrystallisation for a range of deformation temperatures(600–700℃),cooling/soaking time(water quenching,air cooling,10 and 30 min of soaking time)and interpass time(0–10 s)was analysed.During deformation,the spheroidisation of pearlite is dynamically accelerated mainly by boundary splitting mechanism together with the rapid dissolution of cementite,while ferrite softening is attributed to dynamic recovery and continuous dynamic recrystallisation.The strong microstructural evolution during cooling/soaking time indicates that deformation energy accumulated is sufficient to activate metallurgical phenomena in both phases also statically.Static spheroidisation is a diffusive process,with rate controlled by the diffusion of vacancies,as suggested by the estimated activation energy.Ferrite refinement is the result of the evolution of continuous recrystallisation and pinning effect exerted by fine,globulised and homogeneously dispersed cementite particles.Increasing temperature causes accelerated kinetics in metallurgical phenomena;therefore,cooling/soaking time becomes key parameters to achieve ultrafine grained and spheroidised microstructures.Interpass time favours spheroidisation and promotes continuous recrystallisation;however,it must be carefully controlled to find a balance between recrystallisation and Ostwald ripening to optimise microstructural development.展开更多
Spheroidiser is an important middle alloy for producing ductile iron. Now only chemicalcompositions of spheroidiser was presented by producers in detail. It is just reflecting reactive thermodynamic factors of spheroi...Spheroidiser is an important middle alloy for producing ductile iron. Now only chemicalcompositions of spheroidiser was presented by producers in detail. It is just reflecting reactive thermodynamic factors of spheroidiser in melt. But some reactive kinetic factors of spheroidiser in melted iron and its quality stability in melting are not paid attention enough. According to reactive thermodynamics and kinetics of spheroidiser in melt and stability of quality of manufactured spheroidisers during application by statistics. This paper presents evaluated standards for quality of spheroidisers by pyrogenic production under atmosphere fully.展开更多
Laminar plasma jet(LPJ)generated by laminar plasma torch(LPT)has a favorable temperature and velocity distribution.Thus,it is superior to the turbulent plasma jet in material processing.However,most of the reported LP...Laminar plasma jet(LPJ)generated by laminar plasma torch(LPT)has a favorable temperature and velocity distribution.Thus,it is superior to the turbulent plasma jet in material processing.However,most of the reported LPTs usually operate at a relatively low output power with a relatively low arc voltage and thermal efficiency,which limits its capabilities.In this context,this paper attempts to design a new type of high-power LPT with a relatively low arc current and a high thermal efficiency.In the first section,the design principle of the main components is studied and discussed in detail,and a new high-power LPT is proposed.Then,the experimental characteristics of the proposed high-power LPT are examined.Experimental results reveal the following characteristics of the proposed LPT.(1)The max jet length of the proposed LPT reaches at 540 mm.(2)Its mean arc voltage is higher than 290 V when the LPT works with arc currents lower than 200 A.leading to an output power greater than 50 kW.(3)The mean thermal efficiency is higher than 509f.Lastly,the proposed LPT has been applied to spheroidize the aluminum oxide powers.The experiment results for the production of spherical powders show that the proposed LPT hits a good characteristic for material processing.展开更多
The spheroidiser is a necessary additive to manufacture ductile iron.Sometimes with the same hot metal,spheroidisers and treated technology,reactions differ greatly from each other.The reaction may be quite normal in ...The spheroidiser is a necessary additive to manufacture ductile iron.Sometimes with the same hot metal,spheroidisers and treated technology,reactions differ greatly from each other.The reaction may be quite normal in one case,but very intensive for another one.The effects of kinetic factors such as size,surface area and morphology o f spheroidiser on the reaction of spheoidization are studied.展开更多
Magnesium oxide in spheroidiser is harmful to the production of ductile iron for decreasing active magnesium content. To obtain quality ductile iron, the effects of magnesium oxide content in spheroidisers on spheroid...Magnesium oxide in spheroidiser is harmful to the production of ductile iron for decreasing active magnesium content. To obtain quality ductile iron, the effects of magnesium oxide content in spheroidisers on spheroidising treatment, microstrucure and properties of ductile iron were researched, and the critical magnesium oxide in spheroidisers was determined.展开更多
基金financially supported by the European Coal and Steel Community(RFCS-2015.No.709828).
文摘The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lamellae and ferrite recrystallisation for a range of deformation temperatures(600–700℃),cooling/soaking time(water quenching,air cooling,10 and 30 min of soaking time)and interpass time(0–10 s)was analysed.During deformation,the spheroidisation of pearlite is dynamically accelerated mainly by boundary splitting mechanism together with the rapid dissolution of cementite,while ferrite softening is attributed to dynamic recovery and continuous dynamic recrystallisation.The strong microstructural evolution during cooling/soaking time indicates that deformation energy accumulated is sufficient to activate metallurgical phenomena in both phases also statically.Static spheroidisation is a diffusive process,with rate controlled by the diffusion of vacancies,as suggested by the estimated activation energy.Ferrite refinement is the result of the evolution of continuous recrystallisation and pinning effect exerted by fine,globulised and homogeneously dispersed cementite particles.Increasing temperature causes accelerated kinetics in metallurgical phenomena;therefore,cooling/soaking time becomes key parameters to achieve ultrafine grained and spheroidised microstructures.Interpass time favours spheroidisation and promotes continuous recrystallisation;however,it must be carefully controlled to find a balance between recrystallisation and Ostwald ripening to optimise microstructural development.
文摘Spheroidiser is an important middle alloy for producing ductile iron. Now only chemicalcompositions of spheroidiser was presented by producers in detail. It is just reflecting reactive thermodynamic factors of spheroidiser in melt. But some reactive kinetic factors of spheroidiser in melted iron and its quality stability in melting are not paid attention enough. According to reactive thermodynamics and kinetics of spheroidiser in melt and stability of quality of manufactured spheroidisers during application by statistics. This paper presents evaluated standards for quality of spheroidisers by pyrogenic production under atmosphere fully.
文摘Laminar plasma jet(LPJ)generated by laminar plasma torch(LPT)has a favorable temperature and velocity distribution.Thus,it is superior to the turbulent plasma jet in material processing.However,most of the reported LPTs usually operate at a relatively low output power with a relatively low arc voltage and thermal efficiency,which limits its capabilities.In this context,this paper attempts to design a new type of high-power LPT with a relatively low arc current and a high thermal efficiency.In the first section,the design principle of the main components is studied and discussed in detail,and a new high-power LPT is proposed.Then,the experimental characteristics of the proposed high-power LPT are examined.Experimental results reveal the following characteristics of the proposed LPT.(1)The max jet length of the proposed LPT reaches at 540 mm.(2)Its mean arc voltage is higher than 290 V when the LPT works with arc currents lower than 200 A.leading to an output power greater than 50 kW.(3)The mean thermal efficiency is higher than 509f.Lastly,the proposed LPT has been applied to spheroidize the aluminum oxide powers.The experiment results for the production of spherical powders show that the proposed LPT hits a good characteristic for material processing.
文摘The spheroidiser is a necessary additive to manufacture ductile iron.Sometimes with the same hot metal,spheroidisers and treated technology,reactions differ greatly from each other.The reaction may be quite normal in one case,but very intensive for another one.The effects of kinetic factors such as size,surface area and morphology o f spheroidiser on the reaction of spheoidization are studied.
文摘Magnesium oxide in spheroidiser is harmful to the production of ductile iron for decreasing active magnesium content. To obtain quality ductile iron, the effects of magnesium oxide content in spheroidisers on spheroidising treatment, microstrucure and properties of ductile iron were researched, and the critical magnesium oxide in spheroidisers was determined.
