Effect of casting process on the inner-wall band segregation of high-strength antisulfur pipes

Controlling inner-wall band segregation is one of the difficulties in the production of high-strength antisulfur pipes.Comparative tests were carried out on different casting processes(superheat,mold electromagnetic stirring,end electromagnetic stirring,casting speed and soft reduction)for the smelting of high-strength antisulfur pipes.The microstructures of continuous-casting billets and hot-rolled or tempered pipes were analyzed using a metallographic microscope and scanning electron microscope.The mechanism and evolution law regarding the inner-wall band segregation of high-strength antisulfur pipes were studied,and the influence of different casting processes was explored.

基于ProCAST的铜合金通海阀铸造工艺优化

目的结合ZCuAl7-7-4-2合金的铸造特性,研究复杂薄壁铸件通海阀的铸造成形工艺,探究初始浇注方案下的充型、凝固规律,优化工艺并提出合理的铸造工艺方案。方法根据通海阀的结构特点,设计出底注雨淋式浇注系统,并利用流体力学理论和截面积比值法确定浇注系统的具体参数,使用ProCAST软件研究不同工艺参数、冒口尺寸对铸件质量的影响,以得到最优的浇注方案。结果在底注雨淋式浇注系统的充型过程中,金属液温度分布均匀、流速平稳,凝固顺序合理,所得铸件缺陷较少,其中疏松缩孔体积为0.63 mm3,且集中分布在阀盖处。优化浇注温度和浇注速度能够有效减少铸造缺陷,优化出的最佳浇注工艺参数组合如下:浇注温度为1180℃,浇注速度为3.5 kg/s。结合该模拟结果改进冒口尺寸后,彻底消除了铸件的铸造缺陷。结论优化工艺参数和浇注系统设计能够有效提高铸件的生产质量,便于铸件的一次成形,对实际生产提供指导。

Data-driven casting defect prediction model for sand casting based on random forest classification algorithm

The complex sand-casting process combined with the interactions between process parameters makes it difficult to control the casting quality,resulting in a high scrap rate.A strategy based on a data-driven model was proposed to reduce casting defects and improve production efficiency,which includes the random forest(RF)classification model,the feature importance analysis,and the process parameters optimization with Monte Carlo simulation.The collected data includes four types of defects and corresponding process parameters were used to construct the RF model.Classification results show a recall rate above 90% for all categories.The Gini Index was used to assess the importance of the process parameters in the formation of various defects in the RF model.Finally,the classification model was applied to different production conditions for quality prediction.In the case of process parameters optimization for gas porosity defects,this model serves as an experimental process in the Monte Carlo method to estimate a better temperature distribution.The prediction model,when applied to the factory,greatly improved the efficiency of defect detection.Results show that the scrap rate decreased from 10.16% to 6.68%.

基于ProCAST铝合金压板铸造工艺优化设计

利用铸造模拟软件ProCAST对承力索座压板凝固过程进行模拟,通过对铸件成形过程当中的速度场与温度场的变化规律进行分析,得出铸件内部缺陷所在位置及产生的原因,对铸造工艺进行优化设计。通过公式计算,将内浇口的横截面积增大到135 mm^(2),直浇道的高度增加到120 mm。对优化后的方案进行模拟验证,结果表明:优化浇注系统的结构和横截面积,确保了铝液在充型凝固时,有良好的补缩通道使高温铝液对缺陷部位能够及时进行补缩,从而消除铸件内部缺陷,使产品合格率得到大幅提高;通过使用ProCAST软件,不仅大大缩短了试验周期,降低了生产成本,也为产品后续的改进提供了理论依据,实现了良好的经济效益。

Study on Numerical Simulation of Mold Filling and Heat Transfer in Die Casting Process

A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.

Fabrication of AA2024−TiO2 nanocomposites through stir casting process

Given the nonuse of TiO2 nanoparticles as the reinforcement of AA2024 alloy in fabricating composites by ex-situ casting methods,it was decided to process the AA2024−xTiO2(np)(x=0,0.5 and 1 vol.%)nanocomposites by employing the stir casting method.The structural properties of the produced samples were then investigated by optical microscopy and scanning electron microscopy;their mechanical properties were also addressed by hardness and tensile tests.The results showed that adding 1 vol.%TiO2 nanoparticles reduced the grain size and dendrite arm spacing by about 66%and 31%,respectively.Also,hardness,ultimate tensile strength,yield strength,and elongation of AA2024−1vol.%TiO2(np)composite were increased by about 25%,28%,4%and 163%,respectively,as compared to those of the monolithic component.The agglomerations of nanoparticles in the structure of nanocomposites were found to be a factor weakening the strength against the strengthening mechanisms.Some agglomerations of nanoparticles in the matrix were detected on the fractured surfaces of the tension test specimens.

Optimization of casting process based on the theory of inventive problem solving

Optimization of casting process involves the adjustment of parameters as well as the improvement of process schemes and measures.This paper proposes a new method based on the Theory of Inventive Problem Solving(TRIZ) for casting process optimization,and realizes the idea of applying TRIZ to optimize the casting process of a magnesium alloy intake manifold.By this method,the casting process is optimized so as to remove the shrinkage pores.The successful optimization of casting process demonstrates the feasibility of the proposed method.

Effect of melting temperature on microstructural evolutions, behavior and corrosion morphology of Hadfield austenitic manganese steel in the casting process

In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium silicate/CO_2 method, using a blind riser, and then the desired molten steel was obtained using a coreless induction furnace. The casting was performed at melting temperatures of 1350, 1400, 1450, and 1500°C, and the cast blocks were immediately quenched in water. Optical microscopy was used to analyze the microstructure, and scanning electron microscopy(SEM) and X-ray diffractrometry(XRD) were used to analyze the corrosion morphology and phase formation in the microstructure, respectively. The corrosion behavior of the samples was analyzed using a potentiodynamic polarization test and electrochemical impedance spectroscopy(EIS) in 3.5 wt% NaCl. The optical microscopy observations and XRD patterns show that the increase in melting temperature led to a decrease of carbides and an increase in the austenite grain size in the Hadfield steel microstructure. The corrosion tests results show that with increasing melting temperature in the casting process, Hadfield steel shows a higher corrosion resistance. The SEM images of the corrosion morphologies show that the reduction of melting temperature in the Hadfield steel casting process induced micro-galvanic corrosion conditions.

基于AnyCasting的磨辊辊皮铸造模拟与工艺优化

针对磨辊辊皮铸造过程中易出现缩孔等缺陷问题,运用AnyCasting软件对其充型、凝固过程进行模拟。首先,分析铸件金属液的凝固规律,预测缩孔缺陷产生的部位;其次,通过在型腔底部下方增设冷铁,对初始铸造工艺进行优化。结果表明,上移缩孔在冒口中的位置可有效防止在铸件上发生缩孔。按此工艺生产的辊皮铸件无缩孔、组织致密且硬度高。

Finite element analysis for die casting parameters in high-pressure die casting process

The gating system and the overflow system were designed according to the casting structure during high pressure die casting(HPDC) process. The simulation was carried out by ProCAST software to visualize the injection chamber pre-crystallization and the flow of molten metal. The main work is to research four die casting process parameters, i.e. injection temperature, low-pressure velocity, high-and low-pressure velocity’s switching position, and high-pressure velocity. Experimental results show that the higher injection temperature and lowpressure velocity can mitigate the pre-crystallization of the injection chamber. However, when the low-pressure velocity exceeds 0.2 m·s-1, the air entrapment in the chamber occurs. Besides, when the high-pressure velocity is greater than 2.5 m·s-1, the overflow channel at the final filling position is covered by the liquid metal too early. Finally, the injection temperature of 650 °C, the low-pressure velocity of 0.2 m·s-1, the high-and low-pressure velocity’s switching position of 320 mm and the high-pressure velocity of 2 m·s-1 are obtained as the optimal parameters by the software simulation, which has been verified by actual production.

Microstructure and mechanical properties of AZ91-Ca magnesium alloy cast by different processes

The microstructure and mechanical properties of magnesium （Mg） alloys are significantly influenced by the casting process. In this paper, a comparative study on microstructure and mechanical properties at ambient and elevated temperatures of AZ91-2wt.% Ca （AZX912） Mg alloy samples prepared by gravity casting （GC）, squeeze casting （SC） and rheo-squeeze casting （RSC）, respectively, was carried out. The results show that mMg grains in SC and RSC samples are significantly refined compared to the GC sample. The average secondary dendritic arm spacing of AZX912 alloy samples decreases in the order of GC, SC and RSC. As testing temperature increases from 25 ~C to 200 ~C, strength of AZX912 alloy samples is reduced, while their elongation is increased continuously. Compared to GC and SC processes, RSC process can improve the mechanical properties of AZX912 alloy at both ambient and elevated temperatures. The enhancement of mechanical properties of RSC sample over GC and SC samples mainly results from grain refinement in the as-cast microstructure of AZX912 alloy.

Novel methodology for casting process optimization using Gaussian process regression and genetic algorithm

High pressure die casting (HPDC) is a versatile material processing method for mass-production of metal parts with complex geometries,and this method has been widely used in manufacturing various products of excellent dimensional accuracy and productivity. In order to ensure the quality of the components,a number of variables need to be properly set. A novel methodology for high pressure die casting process optimization was developed,validated and applied to selection of optimal parameters,which incorporate design of experiment (DOE),Gaussian process (GP) regression technique and genetic algorithms (GA). This new approach was applied to process optimization for cast magnesium alloy notebook shell. After being trained,using data generated by PROCAST (FEM-based simulation software),the GP model approximated well with the simulation by extracting useful information from the simulation results. With the help of MATLAB,the GP/GA based approach has achieved the optimum solution of die casting process condition settings.

Microstructural characteristics and mechanical properties of bronze/steel bimetallic laminated composite prepared by protective atmosphere casting process

The bonding quality of bronze/steel bimetallic laminated composite is the key factor to whether it can be used in poor working conditions.In this study,bimetallic billets were prepared by the protective atmosphere casting process.The microstructural characteristics,mechanical properties and interface bonding mechanism of the bronze/steel bimetallic composites were analyzed comprehensively through a series of microstructure analysis(inicluding OM,SEM,and EDS)and mechanical properties tests.The experimental results demonstrate that the vaporization of lead(Pb)element in the bronze is only 0.4%in weight,and alloy elements are diffused into both sides at the interface.Moreover,the hardness in the bronze region exceeds 100.0 HV which indicates excellent wear resistance.Tensile and shear tests indicate that the fractures mainly occur on the bronze side with the interaction of the brittle fracture of Pb particles and the ductile fracture of Cu-Sn solid solution.The maximum tensile strength and shear strength reach 204.0 MPa and 211.0 MPa,respectively.These results demonstrate that the protective atmosphere casting process is applicable for the preparation of bronze/steel bimetallic laminated composite with high quality.

CAST工艺在污水处理中的应用

污水处理工作决定着日常生活质量,要提高污水处理效率,避免污水给生活带来严重影响。CAST工艺作为城镇污水处理的主要方法,其是以SBR工艺为基础进行研发,是目前最新型的污水处理工艺,增设了污泥选择器、回流设施等设备,提高城市污水处理效果。基于此,文章以东风农场为主要研究对象,将CAST工艺应用到污水处理中,充分发挥CAST工艺污水处理作用,提高当地水资源质量。

NUMERICAL SIMULATION OF CASTING'S MOLD FILLING PROCESS

Numerical simulation of casting＇s mold filling process is the main and the most important aspect of the foundry CAE technology. But it is time-consuming; it may take dozens of hours or several days. While with the development of computer hardware, numerical simulation of casting＇ s mold filling process has made rapid progress. The simulation results, therefore, have become more and more practical. This study tries to find some clues of the computational time of mold filling process. Firstly, this paper introduces mathematic model and the basic route of numerical simulation of casting＇s mold filling process. Then the computational time of mold filling process has been carefully studied, and some new and useful results have been gained from the study of the computational time. Finally, this paper has given some real applications of numerical simulation of casting＇s mold filling process.

Effect of Process Factors on Microstructure of Semisolid Continuous Casting Billets

Semisolid continuous casting (SSCC) is a new technology to produce billets for semisolid metal forming (SSMF). The effect of process factors, such as pouring temperature, stirring rate, preheating temperature and thermal conductivity of stirring chamber, on the microstructure of SSCC billets was studied by means of the factorial experimental method. The results show that the microstructure of SSCC billets can be controlled by the above-mentioned four process factors. In order to obtain fine and rounded granular grains in an SSCC billet, the pouring temperature, preheating temperature and stirring rate should be kept in a moderate range, and the thermal conductivity of stirring chamber should be high. The regression equations with the process factors connecting the microstructure was also set up based on experimental data.

Construction and analysis of dynamic solidification curves for non-equilibrium solidification process in lost-foam casting hypoeutectic gray cast iron

Most lost-foam casting processes involve non-equilibrium solidification dominated by kinetic factors, while construction of a common dynamic solidification curve is based on pure thermodynamics, not applicable for analyses and research of non-equilibrium macro-solidification processes, and the construction mode can not be applied to nonequilibrium solidification process. In this study, the construction of the dynamic solidification curve(DSC) for the nonequilibrium macro-solidification process included: a modified method to determine the start temperature of primary austenite precipitation(T_(AL)) and the start temperature of eutectic solidification(T_(ES)); double curves method to determine the temperature of the dendrite coherency point of primary austenite(T-(AC)) and the temperature of eutectic cells collision point(T_(EC)); the "technical solidus" method to determine the end temperature of eutectic reaction(T_(EN)). For this purpose, a comparative testing of the non-equilibrium solidification temperature fields in lost-foam casting and green sand mold casting hypoeutectic gray iron was carried out. The thermal analysis results were used to construct the DSCs of both these casting methods under non-equilibrium solidification conditions. The results show that the transformation rate of non-equilibrium solidification in hypoeutectic gray cast iron is greater than that of equilibrium solidification. The eutectic solidification region presents a typical mushy solidification mode. The results also indicate that the primary austenite precipitation zone of lost-foam casting is slightly larger than that of green sand casting. At the same time, the solid fraction(f_s) of the dendrite coherency points in lost-foam casting is greater than that in the green sand casting. Therefore, from these two points, lost-foam casting is more preferable for reduction of shrinkage and mechanical burntin sand tendency of the hypoeutectic gray cast iron. Due to the fact that the solidification process(from the surface to center) at primary austenite growth area in the lost-foam cylinder sample lags behind that in the green sand casting, the mushy solidification tendency of lost-foam casting is greater and the solidification time is longer.

Optimization of processing parameters for rheo-casting AZ91D magnesium alloy

A design of experiment technique was used to optimize the microstructure of the AZ91D alloy produced by rheo-casting. The experimental design consists of four parameters(pouring temperature,shearing temperature,shearing time and shearing rate) with three levels.The grain size and shape factor measurements of primaryα-Mg particles were conducted to determine the microstructure.The contribution of each parameter shows that pouring temperature is the most significant parameter affecting the grain size,and the shape factor highly depends on the shearing temperature.The optimized rheo-casting processing parameters are 650 C for pouring temperature,585℃for shearing temperature,40 s for shearing time,and 600 r/min for shearing rate.Under the optimized processing parameters,the average grain size is 28.53μm,and the shape factor is 0.591.

Effect of process parameters on density of magnesium alloy parts by low-pressure expendable pattern casting

The combination of magnesium alloys with the low-pressure expendable pattern casting(LP-EPC) process would bright future for application of magnesium alloys. The researches are focused on the effect of process parameters on the internal casting quality of magnesium alloy parts. AZ91D magnesium alloy castings were produced for different combinations of the LP-EPC process parameters. Specifically,pouring temperature,vacuum,filling velocity and coupling action of these factors were manipulated to observe their effect on the casting porosity and density distribution. The results indicate that the pouring temperature with LP-EPC process is lower than it in gravity casting. The selected process parameters,such as vacuum,filling velocity and coupled modes of them,must ensure melt metal flowing front profile exhibiting smooth and convex shape. The optimal process parameters for the castings are pouring temperature 983-1 023 K,vacuum 0.02-0.03 MPa,filling velocity 60-95 mm/s,and simultaneous filling with sucking.

Effect of Processing Paramters on Metal Matrix Composites: Stir Casting Process

Conventional stir casting process has been employed for producing discontinuous particle reinforced metal matrix composites for decades. The major problem of this process is to obtain sufficient wetting of particle by liquid metal and to get a homogenous dispersion of the ceramic particles. In the present study, aluminium metal matrix composites were fabricated by different processing temperatures with different holding time to understand the influence of process parameters on the distribution of particle in the matrix and the resultant mechanical properties. The distribution is examined by microstructure analysis, hardness distribution and density distribution.