The punch life of hot punching for high-alloy steel is related to die and product cost,production efficiency,use of automatic equipment,therefore the choice of punch material,billet preparation and punch manufacture should be paid attention.3Cr3Mo3VNb is used in hot punching of high-alloy steel. In order to improve the punch life the punch material composition are optimized. Electroslag remelting is used in refining and the impurity is reduced. The billet is forged twice with large forging ratio. Vacuum furnace is used in heat treatment. Temper is conducted three times. The hardness after heat treatment is taken as HRC 42~46.Chrome-plating is used as surface treatment. Hot punching experiment is conducted. It shows that the average life of punch by 3Cr3Mo3VNb is over 800.

Based on collecting knowledge of shell body hot forming,the shell body hot extrusion-draw forming database is constructed,and the database manage system is developed. The accumulation,sharing,reusing of technology data is realized by applying the system to the design of shell body hot forming. Optimization of technology and die is realized. Design and efficiency are improved.

The characteristics of cylinder shell forming are analyzed. The cabbaging,piercing and draw processes are simulated by finite element software. Orthogonal experiment is designed by billet heating temperature, working speed of cabbage and pierce punch, working speed of draw slide, outer diameter of piercing blank as factors. Simulations are conducted according to the orthogonal experiment scheme. The weighted sum of damage and forming force is taken as optimization target. Influence of factors on optimization target is analyzed. The optimized technology factors are obtained.

Thixoforging requires feedstock having a non-dendritic, equiaxed microstructure, which in some cases can be obtained by the recrystallization and partial (RAP) melting route. Based on the RAP route, squeeze casting-solid extrusion followed by partial melting is proposed to obtain the semi-solid feedstock for thixoforging. After squeeze casting-solid extrusion, unrecrystallized grains were elongated along the extrusion direction. As the temperature rises into the semi-solid regime, there is a sudden increase in the appearance of spheroidal grains. The occurrence of recrystallized grains is closely associated with the location of the first liquid to form above the solidus. Grain coarsening in the semi-solid state can be described by classical LSW equation in Ostwald ripening. The coarsening rate does decrease with increasing solid fraction. L, for L less than approximately 0.70, and then increases again with further increasing L. With prolonged holding time, the grains coarsen and mechanical properties of thixoforged components decrease. Moreover, the AZ91D-RE thixoforged from starting materials produced by squeeze casting-solid extrusion followed by reheating at 570 degrees C for 5 min have extremely fine and uniform microstructure. The tensile mechanical properties of squeeze casting-solid extrusion formed AZ91D-RE are better than those of AZ91D-RE thixoforged from starting materials produced by squeeze casting-solid extrusion followed by partial melting. (C) 2012 Elsevier B.V. All rights reserved.

This paper is an overview for the situation and future of semi-solid die casting technology in China and abroad,and the advantages and disadvantages of the major technology in each stage are introduced in order of the development from semi-solid to semi-molten,then back to semi-solid.Meanwhile their technology and equipment characteristics are also compared and analysed.Finally come to the conclusion that with the trend that semi-solid die casting is developing exceedingly rapidly becoming clearer and clearer,its application prospect will be inestimable.

According to the production requirements of high quality and low cost for car cup class piston product, the ro bust design of warm and cold compound forming parameters based on multiple response surface methodology is given in this paper. The quadratic satisfaction function and quality loss function model based on signal-to-noise ratio are constructed, and the optimum process parameter combination combined with orthogonal test is that the warm forming temperature is （795±5） ℃, the billet deformation ratio through warm forging is 0.45, the cold extrusion punch working zone dimension is 2.5 mm, and the cold extrusion punch fillet dimension is 7 mm. The small batch test assessment shows that the piston product quality stability control ability is very strong through using the optimum warm and cold compound forming parameters, and the engineering production capacity of piston product is got completely.

Machined chips of Mg-Zn-Y-Zr alloy were consolidated by cold pressing and then hot extrusion under various processing temperatures and extrusion ratios. The results show that the microstructure of the chip-extruded alloy is marked by a large number of recrystallized grains and some unrecrystallized grains, which results in high strength but low ductility at temperatures below 320 °C. With increasing processing temperature up to 360 °C, entirely recrystallized and equiaxed grains are obtained. Mg-Zn-Y-Zr alloy with low strength but high ductility is obtained compared with the alloy processed at low temperature. At 420 °C, coarse and equiaxed grains are formed, which results in the drastic decrease of mechanical properties. With increasing extrusion ratio from 8 to 16, the grain refinement is more obvious and the mechanical properties at room temperature are improved effectively. However, the yield strength and ultimate tensile strength are improved a little with further increasing extrusion ratio.

Liquid infiltration was used to prepare magnesium matrix composites reinforced by Al2O3 short fibers and SiC particles. Effects of pressure during liquid infiltration on the mechanical properties and microstructures were also investigated. Results show that when the pressure increased from 0.4 MPa to 60 MPa,the mechanical properties of magnesium matrix composites were increased due to the densification of microstructure. With further increasing pressure,because the preformed body was subjected to compression and short fibers were broken down,the mechanical properties of magnesium matrix composites were decreased.

Thixoextrusion involves processing alloys with a spheroidal microstructure in the semi-solid state. Before thixoextrusion, repetitive upsetting-extrusion (RUE) is introduced into the strain induced metal activation (SIMA) process to predeform AZ80 magnesium alloy. Microstructure evolution of RUE formed AZ80 magnesium alloy during partial remelting is studied at temperatures for times. Tensile mechanical properties of thixoextruded components are determined and compared with those of AZ80 magnesium alloy thixoextruded from starting material produced by casting. The results show that with increasing number of RUE passes solid grain size decreases and the rate of liquation is improved. Prolonged holding time results in grain coarsening and the improvement of degree of spheroidization. The variation of the solid grains with holding time obeys the Lifshitz, Slyozov and Wagner law. Increasing the heating temperature is favorable for the formation of spheroidal solid grains. The tensile properties for AZ80 magnesium alloy thixoextruded from starting material produced by RUE are better than those of AZ80 magnesium alloy thixoextruded from starting material produced by casting.

To promote the application of semi-solid processing in the field of forming magnesium-based composites,in this paper,AZ91D composites reinforced with alumina fibers(5%) were manufactured by the liquid infiltration and then were deformed by equal channel angular extrusion(ECAE).The microstructures and mechanical properties of samples were studied by optical microscope,SEM and tensile testing machine,respectively.Based on those,deformation mechanisms of the samples were also discussed during ECAE.The results show that the basal body of composites undergoing one pass shear deformation consists of dynamic recrystallisation structures after ECAE.However,there are both shear deformation and compression deformation,when there are some defects in samples.The inhomogeneous deformation of samples at turn angle of the die leads to eliminating casting defects and at the same time generating some new deficiencies,such as crack.Therefore,in order to eliminate casting defect during preparation,composites need to be compacted by low pressure infiltration and high pressure solidification before ECAE.

Three kinds of magnesium-matrix composites with different sizes reinforced by 1.1%(volumetric fraction) Al2O3 micro-particles were prepared by the mixture-compression-sinter method.The characteristics of the material microstructure show that the reinforcement of Al2O3 micro-particles uniformly disperses and the particles bring about a striking reinforcement effect.The mechanical properties show that the hardness,yield strength(0.2%),ultimate tensile strength and toughness of magnesium significantly increase with the Al2O3 micro-particles dispersing in the magnesium-matrix composites.Compared with AZ91 magnesium alloy reinforced by SiC micro-particles with a higher volume fraction,the magnesium alloys reinforced by nano-sized and sub-micrometer Al2O3 particles offer comparatively higher yield strength(0.2%),ultimate tensile strength and toughness.

Magnesium ZK60-RE semi-solid billets were prepared by conventional cast and equal channel angular extrusion respectively. Microstructure evolution of as-cast and extruded semi-solid billets during isothermal heat treatment was studied by optical microscope. The results show that in comparison with grains of semi-solid billets prepared by conventional casting,those of semi-solid billets prepared by equal channel angular extrusion are more fine and spherical and better suited for semi-solid forming. During isothermal heat treatment,the grain coarsening mechanisms of two billets are coalescence and Ostwald ripening. The intragranular liquid droplets in grains for as-cast materials originate from eutectic structure during non-equilibrium freezing and entrapped liquid during coalescence of grains. With increasing in holding time,the grain size of the as-cast billets increases initially,then decreases and increases again,while the grain size of the extruded billets increase monotonously.

Based on conventional extrusion and equal channel angular extrusion (ECAE), a new severe plastic deformation (SPD) method called compound extrusion is developed to fabricate fine-grained AZ91D magnesium alloys. The fine grain size of 6 μm is obtained as the accumulated strain increased to 9.146. The AZ91D alloy treated by compound extrusion exhibits good mechanical properties, with a yield strength of 202.2 MPa, a tensile strength of 323.1 MPa and an elongation to fracture of 14.8%. The good mechanical properties of AZ91D alloy treated by compound extrusion are due to grain refinement and to the homogeneous distribution of intermetallic particles. The success in development of compound extrusion proves that compound extrusion can offer a good opportunity for the development of good mechanical properties of as-cast magnesium alloys.

This paper demonstrates the effect of equal channel angular extrusion(ECAE) process on the microstructure and mechanical properties of cast magnesium alloy AZ91D.In terms of mechanical properties,the yield strength,ultimate strength,elongation rate,and elastic modula of AZ91D were increased from 86.3 MPa,146.3 MPa,1.84%,and 42.5 GPa to 144.1 MPa,222.8 MPa,15.15%,and 47.7 GPa after one ECAE pass,and to 109.1 MPa,268.3 MPa,25.48%,and 48.9 GPa after two ECAE passes at room temperature.In terms of microstructure,the dendritic crystal had been crushed because of sliding and rotation motion after the first pass of ECAE process,the crystal and black eutectic phase(Mg17Al12) of AZ91D has been elongated along the direction of extrusion.When the second pass was applied,the black eutectic phase began to remelt,and was reduced and distributed discontinuously.

This paper aimed at a kind of cylinder with multi-hole,put up the research of extrusion.By means of numerical simulation,multifold technical projects were compared,the flowing behavior of the material and the forming defects were analyzed,then the technical project was optimized,and the engineering tests were carried out based on it.The result indicated that the part with multi-hole after extrusion was formed with good filling,avoiding the defect of bell mouth,and the dimension of the part also satisfied its requirements.

The paper introduces the characteristics,design cycle and main functions of each program module of the digital design system of cartridge case forming process.Rule-based reasoning and case-based reasoning are combined in the system.Calculation of process parameters and parameterization modeling of half blank and die can be finished by the system.The system can give knowledge and experience of design of cartridge case forming process and improve design efficiency.

The paper introduces knowledge-based numerical simulation of metal forming which includes building knowledge base for storage and inquiry of simulation preprocessing knowledge and cases which comprise preprocessing parameters and simulation results,collecting large amount of flow stress models of materials by papers and experiments,developing knowledge-based numerical simulation system by which preprocessing parameters can be put in a table once.The knowledge and cases in the knowledge base are referenced well as preprocessing parameters are put into the system.A special interface is developed to put the preprocessing parameters into the simulation software.The simulation efficiency and accuracy are improved evidently.

According to characteristic of shell body forming,KBE technology was applied.By way of integrating knowledge,data and experience of forming in database,the digital design system of shell body forming was developed.The principle and characteristic of the system are introduced.A heavy calibre shell body forming process was designed by using the system.The design efficiency was improved and development cost was reduced.

Warm extrusion was simulated by finite element software for an aluminium alloy deep tapered shell.The forming technology and die design were analysed.Measures were put forward to the problems of larger wall thickness difference and ragged orifice.

本文对异型内孔的冷挤压成形工艺进行了分析,提出了一些应注意的问题和解决的方法,并在生产中得到了实际的应用,取得了良好的社会和经济效益。