摘要:In order to prepare liquid Al-Sn alloy with uniform distribution of Sn,the liquid Al-Sn alloy in crucible with straight blades arranged on inner wall was stirred by electromagnetic stirring.The influences of blade arrangement angles on the distribution of Sn in liquid Al-Sn alloy were investigated,and the processing parameters were determined to obtain liquid Al-Sn alloy with uniform distribution of Sn.The results show that the radial distribution of Sn in crucible is determined by the angle β between blade and the radial of crucible,and the axial distribution of Sn in crucible is controlled by the angle γ between blade and the axes of crucible.With β of 28°and γ of 28°,the liquid Al-20Sn alloy with uniform distribution of Sn in radial and axial direction can be prepared.
关键词:Al-Sn Liquid Alloy;Stirring;Uniform Distribution
摘要:Microstructure and mechanical properties of Mg-1Er-0.6Zr alloys in as-cast,extruded and aged state were investigated by means of optical microscope(OM),scanning electron microscope(SEM)and energy spectrum analysis(EDS).The results show that the tensile strength,yield strength and elongation of as-extrued Mg-1Er-0.6Zr alloy at 300 ℃ with extrusion ratio of 16 reach 206.5 MPa,78.5 MPa and 25%,respectively,improved by 28%,8% and 150%,comparing to those of the as-cast alloy.The strength of the extruded alloy after aging treatment is increased slightly,however,it is greatly decreased after solid solution with re-aging treatment,and elongation is decreased slightly also.
摘要:Technological process of manufacturing sand core for multi-channel hydraulic valve body was described,and qualified sand core was produced by the SLS method.Through using fine pearlite sand as raw sand to prepare coated sand and adding phenolic resin with b proportion,high strength sand core can be sintered with optimized sintering parameters.Using proper spreading powder machine,the interference of spreading powder process on the sand core sintered can be decreased effectively,and pre-heating temperature during sintering process can be decreased also,which are beneficial for reducing clean difficulty of complicated sand core resulting from heat concentration and improving the precision of sand core.
摘要:A novel Al-Ca-C master alloy was fabricated with Al powder and CaC2 powder as raw materials by powder metallurgy method combining with in-situ synthesis process to use for grain refinement of Mg-Al based alloys,and Al4C3,CaAl2,CaAl4 phase can be observed in the master alloy prepared.The results reveal that the master alloy can refine AZ91 magnesium alloy effectively.With the addition of 1% Al-Ca-C master alloy(weight percentage),the grain size of AZ91 alloy is decreased from 120150 μm to 4050 μm.The refining mechanism on grain size in AZ91 magnesium alloy by the Al-Ca-C master alloy was discussed,and it was pointed out that Al4C3 formed could be acted as heterogeneous nucleation substrates for primary Mg,and Ca and C were believed to increase the grain refinement efficiency by the constitutional under-cooling.
摘要:Dynamic compressive fracture behavior of extruded AZ31B magnesium alloy was tested using the Split Hopkinson Pressure Bar apparatus.Dynamic compressive fracture morphology of AZ31B magnesium alloy was observed by optical microscope(OM) and SEM(scanning electron microscope).The results show that the fracture morphology of AZ31B magnesium alloy is characterized by toughness-brittleness mixed model when the alloy is compressed along extruded direction.Through multi-level initiation and propagation,cracks are evolved into fracture in the end.Macro-fracture surface is located at extruding direction with the angle of 45°,exhibiting typical shearing failure.
摘要:Influences of the content of carbon and nitrogen on solidification structure of ferritic stainless steel at three zones were investigated.The results show that with the increase of carbon and nitrogen content,the content of equiaxed grain is increased,and primary dendritic spacing of columnar crystal is enlarged,while the thickness of chilled layer is decreased.
摘要:Cooling plate is an air-tightness part used for the automobile.The processing parameters were determined by analyzing die casting process in die casting die design,and three-dimenstional moulding and design were completed by the CAD software.Based on process analysis and CAD data,filling of cooling plate was visualized by the MAGMA software,and simulated results were approached including filling process,solidification process and die temperature distribution as well as P-Q2map,meanwhile,design optimization of the mould and process was conducted.The experiment and practical production show that the mould design and process design are feasible for cooling plate.
摘要:Filling process of die casting Zn alloy cover plate was visualized by the Flow-3D software.The unrational design of initial gating system was modified by simulation to eliminate effectively flow vent and gas bubble in the Zn alloy cover plate.The results show that flow morphology and filling sequence of liquid metal are closely dependent on the ingate design,which controls the quality of cover plate.Defect distribution possible in the die castings can be predicted effectively by the numerical simulation.
摘要:The temperature field,shrinkage porosity(hole) in the ZL205A alloy shell castings during low pressure casting process were visualized through numerical simulation.The results show that the desirable temperature filed can be obtained and tendency of shrinkage porosity in the defect location of the shell can be reduced by using the chill and riser,adding the number of slit runners from eight to ten and decreasing the length of feeding distance from 200 mm to 157 mm.Comparison with the experimental results indicates that the scheme of chill combining with riser is reasonable and feasible.
摘要:Injection system with inner-set check valve for die casting machine was development to solve the problems of the long establishment-time in three-stage injection system in traditional die casting machine due to use floating piston to pressurization.Inner-set check valve with spring reset which was installed in pressurization piston rod could rapidly switch off cone face with the help of spring to shorten established-pressure time by pressurization.Injected piston buffer mechanism was designed between the right end of injected piston and inner-set check valve,so the size of oil entrance during slow injection process is increased gradually with the move of injected piston,realizing the proportional acceleration of slow injection velocity.
关键词:Die Casting Machine;Injection System;Established-Pressure Time
摘要:Different constituent release agents was sprayed on surface of the mould steel to evaluate the formation of lubricant film and temperature-decrement velocity of release agent at different mould temperature.The experiment and practical application verify that the release agent developed with new constituent proportion can decrease effectively soldering phenomenon at high temperature and improve quality of die castings.
摘要:The demould is a difficult point for castings with screw thread in the design of die-casting die.Aiming at interval inner screw thread in die castings,the screw thread demould mechanism with inner inclined sliding block was designed.While the inner inclined sliding block pushed out the castings with the help of the ejector pin,it moved in and unloads the screw thread along guided-chute of moving half core.Based on analyzing the casting process,mould structure was designed,and the working principle was described,meanwhile,the processing parameters were presented.The die casting die exhibited reliable and high efficiency,meeting the quality requirement.
关键词:Inner Screw Thread;Inclined Sliding Block;Secondary Parting;Die Casting Die
摘要:With the increasingly improvement of function and control of pressurization mechanism in the die casting machine,time-establishment,which has been as a controllable factors,was paid attention to.Through analyzing the working mechanism of accumulator,pressure-increment process of injection and pressurization mechanism,pressurization control mode and time-establishment,the minimum time-establishment and key factors influencing time-establishment were presented.
摘要:Effects of different artificial aging at 150,165,180 and 200 ℃ for different time on hardness of A357 alloy specimens produced by low pressure casting and by counter pressure casting were evaluated.The results reveal that the hardness difference between the specimens produced by low pressure casting and by counter pressure casting can be neglected,however,hardness of the specimens produced by counter pressure casting exhibits more uniform distribution.The hardness of the two specimens is decreased by approximately 20% after solid solution.However,after artificial ageing,hardness of the specimens produced by counter pressure castings is higher than that produced by low pressure casting.In addition,the specimens produced by low pressure casting is different from counter pressure castings in hardness change with the time change at 165 ℃ and 200 ℃.
摘要:A356 melt poured by low superheat was slightly electromagnetically stirred for short time with an electromagnetic stirrer which was controlled by frequency conversion.Effects of electromagnetic stirring time on morphology and distribution of primary phase and eutectic phase in microstructure of semisolid A356 alloy were investigated to obtain the optimized electromagnetic stirring processing parameters.The results indicate that the primary α-Al with 55.70 μm in average equal-area circle diameter and 0.86 in average shape factor can be obtained in semisolid A356 alloy with pouring at 620 ℃,stirring for 15 s at 30 Hz,and holding at 615 ℃ for 10 min.Meanwhile,the fine and compact eutectic phases are uniformly distributed in the alloy.The desirable microstructures in semisolid A356 alloy can be observed with optimized processing parameters.
摘要:Centrifugal composite cast iron roller is a kind of bimetallic solid roll which has good performance with hard surface and tough core.To obtain the high-performance roller,the controlling keys of the metal mold production process control,surface liquid metal control,interval time of surface liquid metal and inner liquid metal pouring control were described in details.The centrifugal composite cast iron roller with286mm × 508mm was produced successfully.Through calculating,selecting and measuring as well as recording the parameters from the controlling keys,the measured data from hardness of the barrel,roll diameter and work layer thickness confirms the effect of the trial roll quality control.
关键词:Rotating Speed;Pouring Temperature;Interval Time
摘要:For complex engine housing,a new design idea of the lost foam mold was presented from the view point of the parametric design method and assembly tree,and the key points of design and development of the lost foam mold were described.The practical production verified that the designing idea could facilitate the modification of the product and mold and improve the efficiency of design of lost foam mold.
关键词:LFC Mold;CAD;Parameterization;Secondary Development
摘要:83 ton oversize heterotypic gray iron crossbeam was manufactured by full mold casting.Aiming at the structure characteristics of the crossbeam,pattern was made.Meanwhile,process parameters were presented.Sand and coating were taken into acount,and pitmoulding was performed.Finally,qualified crossbeam was produced sucesssfully.
摘要:Influences of water-gypsum ratio,soluble glass and CMC on the contractility of the plaster mould for the arc spraying rapid tooling were investigated.The experimental results show that contractility of plaster mould is increased with the increase of the content of the sodium silicate and CMC,and peak value can be oberved in the contractility at a fixed water-gypsum ratio.In addition,the minimum contractility appears with 0.15%0.25% CMC.
摘要:Some cracks appear in the surface of milled K242 alloy fan-shaped positioned parts.Through analyzing crack,chemical composition and microstructure observation,it was presented that the crack on the surface of the fan-shaped positioned parts milled belongs to stress crack.And the factors resulting in the crack were investigated.Through optimizing casting process and machining process,stress crack in the parts during machining process was eliminated effectively.
摘要:In situ Mg2Si/Al composites were modified with pure Bi.The microstructures before and after modification were observed by OM(optical microscope),and tensile properties of the composites modified were measured,and the fracture morphologies were analyzed by SEM(scanning electron microscope) before and after modification.The results show that the addition of proper amount of Bi has significant modification effect on both primary and eutectic Mg2Si in the composites.The morphology of primary Mg2Si is changed from dendritic to polyhedral shape,and the grain size is refined from 70 μm to 6 μm,meanwhile,the eutectic Mg2Si is transformed from flake-like to very short fibrous or dot-like.The tensile strength of the alloy modified by 1.0% Bi is increased from 175 MPa to 260 MPa,and its elongation is increased from 3.5% to 7.0%.
关键词:Al/Mg2Si Composites;Bi;Modification;Primary and Eutectic Mg2Si;Mechanical Properties
摘要:Copper-TiN composites were prepared by powder metallurgy technology.The microstructure and mechanical properties of the composites prepared have been analyzed.Effects of the preparation methods on the characteristics of the composites prepared were approached.The results show that with the addition of the TiN,the electric conductivity of the composites prepared is distinctly decreased,compared with that of the copper.Density,tensile strength and hardness as well as the conductivity of the composites prepared are decreased with the increase of the TiN.The density,hardness and electric conductivity of the composites prepared by vacuum hot pressing sintering is greatly superior to those of prepared by cold isostatic pressing sintering.
摘要:Effects of different hot rolling processes on microstructure of hot-rolling and heat-treatment 7055 aluminum alloy have been investigated by hot rolling,heat-treatment and optical microscope observation,in which the hot rolling processes included general process and the process of severe reduction for per pass.The results show that,after severe reduction for per pass,uniform deformed microstructure in the center part can be observed in 7055 aluminum alloy plate,and the coarse second phase is sufficiently broken up.The second phase is fully dissolved into the center part of the plate rolled by the process of large reduction for per pass after solid-solution at 470 ℃ for 90 min.Compared with those by general rolling process,the recrystallization grain volume fraction is decreased by 15% in the plate rolled by the process of large reduction for per pass after aged at 120 ℃ for 24 hours.
摘要:Through alloy preparation,microstructure observation and the mechanical properties test,effects of heat treatment on microstructures and mechanical properties of the Mg-Zn-Zr magnesium alloy have been investigated.The results show that,the microstructure of Mg-5.5Zn-0.5Zr alloy can be improved by solid solution(380 ℃×12 h) and aging(190 ℃×12 h) treatment,and mechanical properties at room temperature and at high temperature can be increased effectively.Direct aging treatment exhibits the equivalent or even better effects with the solid solution treatment,meanwhile,it has the advantages of simple processing procedure and convenient operation,optimizing efectively the heat-treatment process of Mg-Zn-Zr alloy.
摘要:The compound influence of melt thermal treatment,including melt mixing and melt superheating,and strontium modification on silicon phases in Al-20Si alloy was investigated.The results show that with only strontium modification,the primary silicon in the alloy is modified weakly,and the morphology change of the eutectic silicon can be ignored.The low temperature Sr modified Al-10Si melt mixed with the high temperature Al-30Si melt in the ratio of 1:1,nuclei number in Al-20Si melt is increased,resulting in the significant refinement of primary Si phase.And then,mixed melt is treated by superheating to 1 000 ℃,and the average size of the primary silicon is decreased to approximately 14 μm,and the morphology of the eutectic silicon is changed from long needle-shape into short fiber-like.
摘要:Poor surface quality,slag inclusion,porosity and other casting defects easily appear in the aluminum engine cylinder head produced by traditional top-filling casting.To eliminate the problems which were difficult to control,a new bottom pouring method was proposed based on the structural characteristics and technical requirements of engine cylinder head.Gating system was determined for permanent mold casting aluminum alloy engine cylinder head,and cooling method of waterways combined with compressed air was adopted to achieve a sequential solidification of aluminum alloy melt from the bottom to top,which could ensure a smooth filling of molten metal,good exhaust capacity,and also reduce the slag deposition fully.Comparative analysis on casting quality shows that the bottom pouring design is reasonable and feasible,and good surface quality,few casting defects such as porosity,slag hole,and so on,could be realized,significantly improving quality of cylinder head.
摘要:Microstructure evolution of monotectic alloy Al-Pb during directional solidification with a static magnetic field were investigated by simulation combining with experiment.The results show that the static magnetic field can significantly affect the microstructure evolution of monotectic Al-Pb alloy through restraining the convection of matrixmelt,beneficial for obtaining dispersedly monotectic alloy composites.
关键词:Monotectic Alloy;Static Magnetic Field;Solidification;Numerical Simulation;Liquid-liquid Decomposition
摘要:To simplify the process and improve product efficiency of TA2 Titanium tubes with φ89 mm×2 mm,the process optimization were conducted by re-designing the dimension of tube blank and decreasing the number of rolling passes.Optimized process was presented by checking extrusion ratio,rolling force and bearing capacity of rollers.Through process optimization,the materials losses were reduced by about 1%,and rolling pass was decreased by one pass.Meanwhile,the utilization ratio of equipments was increased,and the service life of the mould was improved.Finally,the productivity was increased by three times.
关键词:TA2 Titanium Tube;Process Optimization;Extrusion Ratio
摘要:In order to understand the influence of different atmospheres on the ignition-proof behavior of spraying deposited magnesium alloy,the morphology,structure and the ignition-proof mechanism of the Mg-5Ca alloy surface film formed under different atmospheres were observed.The results indicate that,after heated at 740 ℃ for 2 h,the surface film formed under commercial nitrogen atmosphere(99.5%)on the alloy exhibits smooth and continuous,while under high-purity nitrogen atmosphere(99.995%),the surface film formed is composed of a large number of irregular particles with observed crack.Meanwhile,the surface film formed in air shows loose structure with cauliflower-like appearance,and the crack and deformation are very serious.Ignition-proof mechanism reveals that,under nitrogen atmosphere,a protective film is composed of the mixed structure of CaO,MgO,and Mg3N2、Ca3N2 at the outer surface and CaO and MgO at the inner layer,where Ca element aggregated on the folds,impurities,cracks and the junction of surface and substrate.The dense structure compensate the loose hole,which is beneficial for preventing the Mg-5Ca alloy from burning.However,the film under high-purity nitrogen is only composed of Mg3N2 and Ca3N2,and it is very thin,so that it can not cover the surface entirely,resulting in the low ignition-proof efficiency.Film formed in air is composed of mixed structure of CaO and MgO with mostly CaO at the free surface,and it is too thick to bear the pressure,so that the film is broken and the surface quality is the worst.
摘要:The alloy microstructure was changed in the process of aging.After 700 ℃×2 h solution treatment,the microstructure of rolling specimens consists of α0 single phase with face-centered cubic crystal.The matrix α0 phase exhibits different phase decomposition depending on ageing time and constituents.At 2 hour aging,the matrix α0 phase exhibits a spinodal decomposition and transform into the α’0 modulation structure.The spinodal decomposition appears with the help of Cu atoms migration due to the generation of many vacancies from the quenching.Early stage of ageing at 400 ℃,the matrix α0 phase transform α’0 modulation structure.With increasing in the ageing time,the α’0 transform into AuCuI ordered phase,age-hardening appears.Finally,all the α’0 is changed into AuCuI ordered phase.
关键词:Color Gold Alloy;Aging;Spinodal Decomposition;AuCu I Ordered Phase
摘要:Based on analyzing controllable pitch propeller hub casting process,the process design、molding、melting and pouring of copper alloy were approached.Through adopting bottom gating system with adding ingate numbers,and proper increasing the pouring temperature,the casting defects in the hub were reduced or eliminated,improving quality of the product.