查看更多>>摘要：Heat-resistant alloys with excellent mechanical properties are widely used in various fields,and further improvement in their properties is essential to meet the requirements in new-generation advanced supercritical boilers,nuclear reactors,superheaters,and other new materials applications.To effectively enhance the comprehensive performance of heat-resistant alloys,second-phase particle strengthening has been widely studied,and in the face of different service envi-ronments of advanced heat-resistant steels,the selection of suitable second-phase particles is essential to maximize the performance of these alloys.To this end,three major types of reinforcing phases in heat-resistant alloys such as carbides,rare earth oxides,and intermetallic compounds are summarized.A comparative analysis of the precipitation behavior of the reinforcing phases with different types as well as the risks and means of controlling their use in service,is presented.Key parameters for the application of various types of second-phase particles in heat-resistant alloys are provided to support the design and preparation of new ultrahigh-performance heat-resistant alloys.
查看更多>>摘要：Cu-bearing stainless steel is widely used in the fields of food,medical and household sanitary equipment because of its surface finish and corrosion resistance.However,the growth of bacteria on stainless steel leads to the formation of biofilms,which causes corrosion.Therefore,the antibacterial property of stainless steel is a worthy research topic.Reviews of breakthroughs in the field of corrosion resistance and antimicrobial properties are still lacking.Herein,due to the scarcity of publications on the antibacterial mechanisms and processing methods of antibacterial Cu-bearing stainless steel,we review the current state of relevant research and progress.The toxicity of Cu,corrosion resistance mechanism of stainless steel,and antibacterial mechanism and preparation method of antibacterial stainless steel are reported.In addition,alloying,surface modification and other methods are found to have limitations in balancing the toxicity and antibacterial properties of copper and the relationship between the antibacterial properties and corrosion resistance of Cu-bearing stainless steel.A new preparation method of antibacterial stainless steel associated with selective laser melting(SLM)is proposed.SLM is becoming a powerful additive manufacturing technology that can be used to manufacture customized and complex metals.The research status of SLM applied in antibacterial stainless steel preparation is described.Finally,the future research direction of Cu-bearing antibacterial stainless steel is discussed.
查看更多>>摘要：Based on the stoichiometric method and the free energy minimization method,an ideal model for the reduction of iron oxides by carbon and hydrogen under blast furnace conditions was established,and the reduction efficiency and theoretical energy consumption of the all-carbon blast furnace and the hydrogen-rich blast furnace were compared.The results show that after the reduction reaction is completed at the bottom of the blast furnace,the gas produced by reduction at 1600 ℃ still has a certain excessive reduction capacity,which is due to the hydrogen brought in by the hydrogen-rich blast as well as the excess carbon monoxide generated by the reaction of the coke and the oxygen brought in by the blast.During the process of the gas with excessive reduction capacity rising from the bottom of the blast furnace and gas reduction process,the excessive reduction capacity of the gas gradually decreases with the increase in the dydrogen content in the blast.In the all-carbon blast furnace,the excess gas reduction capacity is the strongest,and the total energy consumption per ton of iron reduction is the lowest.This shows that,for the current operation mode of the blast furnace,adding hydrogen in the blast furnace cannot reduce the consumption of carbon required for reduction per ton of iron,but rather increases the consumption of carbon.
查看更多>>摘要：A room-temperature electrodeposition method with an organic electrolyte was developed to fabricate a HNO3-pretreated graphene paper Cu(GP'-Cu)composite.To improve the interfacial bonding of GP'-Cu composite,magnetron sputtering technology was used to create a"sandwich"structural gradient GP'-Cu composite.The selection of the intermediate transition layer metal was based on two-dimensional disregistry.Scanning electron microscopy,X-ray photoelectron spectroscopy,and other analytical methods confirmed that the addition of an intermediate transition metal(Cr,Ni)layer reduced the gap distance and enhanced the interfacial bonding of the GP'and Cu deposited layers.The GP'-Ni-Cu composite exhibited the largest increase in tensile strength and conductivity.In addition,it had the highest thermal diffusivity and elongation at break among the GP'-Cu,GP'-Cr-Cu and GP'-Ni-Cu composites.
Yan YanGuang-hao ShangLi-ping ZhangShao-ying Li...
74-91页
查看更多>>摘要：A thermodynamic model for predicting the equilibrium oxygens of 304 stainless steel was developed based on the theory of slag-steel equilibrium,the law of mass conservation,and the ion and molecule coexistence theory.In the developed model,the Fe-Cr-Mn-Si-Al-S-O-melts reaction system and CaO-MgO-CaF2-FeO-MnO-Al2O3-SiO2-Cr2O3 slags were considered.The oxygen contents calculated by the model are in good agreement with experimental results and reference data.The equilibrium oxygen contents in 304 stainless steel mainly decrease with increasing binary basicity(w(CaO)/w(Sio2),where w(i)is the mass percentage of component i)and decreasing temperature.Controlling binary basicity at 2.0 while maintaining temperatures lower than 1823 K will keep the oxygen contents in the 304 stainless steel lower than 15 x 10-6.The equilibrium oxygen contents may also be decreased with increasing content of MgO in slags,which is more significant at lower binary basicity.Besides,a small amount of FeO,MnO,and Al2O3(about 0-2.5 wt.％)in slags has little effect on equilibrium oxygen contents.Furthermore,it is found that the[C]-[O]reaction may occur during refining process but will not significantly affect the equilibrium oxygen contents.
查看更多>>摘要：The reduction behavior of iron ore powder by high-volatile coal was investigated,and its kinetic mechanism was clarified.The effect of volatiles in coal on the reduction reaction of iron ore was compared by utilizing a Xinjiang lignite with a high volatile content and its pyrolysis carbon produced by high-temperature pyrolysis to remove volatiles,serving as a reductant.The mass loss and gas composition of the samples during the reduction process were detected using thermo-gravimetric analysis and gas chromatography,and the morphological changes of iron ore powder were observed through scanning electron microscopy.The kinetic parameters of the iron oxide reduction reaction were calculated by the Flynn-Ozawa-Wall method,and the kinetic mechanism of volatile participation in the iron oxide reduction reaction was determined through the Coats-Redfern method.The results indicate that the coupling effect between the high-volatile coal pyrolysis and reduction reactions occurs during the second stage of the entire coupling process,which corresponds to the late stage of coal pyrolysis with a substantial release of H2 and CO.The volatiles in coal actively participated in the reduction reaction,reducing the initiation temperature of the reaction by around 200 ℃.The reduction of iron oxides by high-volatile coal was jointly promoted by the"hydrogen cycle"and"carbon cycle",resulting in a higher reduction extent and metallization rate at the end of the reaction.When high-volatile coal was used as the reductant,the average activation energy for the entire process was 76.5 kJ/mol,a significant decrease compared to the employment of pyrolysis carbon without volatiles as the reductant(1167 kJ/mol).
查看更多>>摘要：A high-temperature reduction roasting method was used to achieve metallic iron and zinc recovery from blast furnace gas ash(BFA).The reduction processes for Zn-containing and Fe-containing oxides were analyzed in detail by using ther-modynamic equilibrium calculation and the principle of minimum free energy.The results showed that the main reaction in the system is the reduction of ZnFe2O4 and iron oxides.Over the full temperature range,iron oxides were more easily reduced than zinc oxides.Regardless of the amount of CO contained in the system,the reduction of ZnO to Zn was difficult to proceed below the boiling point(906 ℃)of Zn.When the reduction temperature is below 906 ℃,the reduction process of zinc ferrate was ZnFe2O4 → ZnO;when the reduction temperature is above 906 ℃,its reduction process becomed ZnFe2O4 → ZnO → Zn(g).The metallization and dezincification rates of the BFA gradually increased with increasing reaction temperature.As the C/O ratio increased,the metallization and dezincification rates first increased and then decreased.The effect of reduction time on BFA reduction was similar to that of reaction temperature.
查看更多>>摘要：The 42 kg industrial H13 castings were prepared by different super-gravity fields with multi-rotation speeds,and the distribution of oxide inclusions in the castings was studied.In addition,the inward movement Reynolds number and inward movement time of oxide inclusions as well as the solidification time of molten steel at different positions in the castings were calculated to clarify the removal mechanism of oxide inclusions in super-gravity field.The results show that the large size(i.e.,greater than 10 μm)oxide inclusions are mainly concentrated in the inner and outer parts of the super-gravity castings with constant rotation speed(500 r min-1)and five-stage rotation speeds(500,600,750,850,and 950 r min-1),respectively,while there are no large oxide inclusions in the super-gravity castings with three-stage rotation speeds(500,600,and 750 r min-1).Although an increase in the particle size of inclusion and the rotation speed in super-gravity field is conducive to the increase in the inward movement Reynolds number of oxide inclusions and reduction in the inward movement time of oxide inclusions,it will reduce the local solidification time of molten steel.In the range of the rotation speed studied,the super-gravity field with three-stage rotation speeds has the best effect on the removal of inclusions in H13 molten steel.
查看更多>>摘要：The morphology,size,quantity,and composition of complex oxide+carbonitride in H13 steel held at 1250 ℃ for 5,10,and 15 h were determined.The results show that the ratio and number of complex carbonitrides with cores in H13 steel are gradually increased when holding at 1250 ℃ compared with those in the original H13 steel,and the core size increases.There are one or more oxide cores in(Tix,V1-x)(Cy,N1-y),including xCaO·zAl2O3,xCaO·yMgO·zAl2O3,and CaO after holding at 1250 ℃,in addition to MgO·Al2O3 and Al2O3 in the original steel.The equilibrium temperature for(Tix,V1-x)(Cy,N1-y)precipitation at the solidification front and decomposition in the solid state was theoretically analyzed,which was affected by the x value and the product of Ti and N contents in H13 steel.Meanwhile,the composition of(Tix,V1-x)(Cy,N1-y)is influenced by the oxide cores.It is convinced that(Tix,V1-x)(Cy,N1-y)with oxide cores has a higher stability,especially for oxides with a high Al2O3 content.Heat treatment at high temperature facilitates a more reasonable analysis of oxide+carbonitride,and the generation mechanism of oxide+carbonitride was discussed.
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