铝合金汽车轮毂铸件凝固过程缺陷CAE分析

用对比定量的方法研究了浇注温度、模具预热温度对模具温度场的影响,探讨了冷却方式、浇注速度及模具结构对铸件缺陷的影响.运用某铸造模拟软件对其模具及铸件进行了压铸过程温度场分析和轮毂低压铸造充型及凝固过程做了模拟分析,介绍了铸件缺陷-缩松,缩孔的成因,利用CAE技术分析了铝合金汽车轮毂在凝固过程中浇注速度、冷却方式对缩松,缩孔的影响。     

A new shell casting process based on expendable pattern with vacuum and low-pressure casting for aluminum and magnesium alloys

A new shell casting process, with the adoption of the foam pattern of lost foam casting (LFC) as prototype and the combination of the thin shell fabrication technology of investment casting and vacuum and low-pressure casting process, was proposed for manufacturing complicated and thin-walled aluminum and magnesium alloy precision castings. Loose-sand uniting vacuum was used in the new process to further reinforce the thin shell, and the new process proves to be a process with simple process, low cost, and high thin shell strength. Because the molten metal filling and solidification are completed under air pressure and vacuum level, the filling capability and feeding capacity of the molten metal are greatly improved, and the castings become denser. This paper mainly investigated the fabrication technology of thin shell based on foam pattern prototype, the removing foam and roasting shell process and vacuum and low-pressure casting process. The few-layer compound thin shell of silica sol–sodium silicate was adopted for the new process. Removing foam pattern was carried out at 250°C for 30 min, and the shell was roasted at 800°C for 1 h. Combined with the vacuum and low-pressure casting process, this new shell casting process has successfully produced thin wall and complex aluminum and magnesium alloy parts with high quality. In addition, comparisons in terms of filling ability, microstructure, mechanical properties, porosity, and surface roughness among this new shell casting, gravity casting, and LFC were also made to show the characterization of this new shell casting process.     

Novel technologies for the lost foam casting process

Lost foam casting (LFC) is a green precision casting process categorized as a near net forming technology. Yet, despite its popularity, it still suffers from some technological problems, such as poor filling ability of the castings, coarse and non-dense microstructure, low mechanical properties for the Al and Mg LFC processes, and defective carburization for the low carbon steel LFC process. These drawbacks restrict the development and widespread application of the LFC process. To solve these problems, the present study developed several novel LFC technologies, namely, LFC technologies under vacuum and low pressure, vibration solidification, and pressure solidification conditions; expendable shell casting technology; and preparation technology of bimetallic castings based on the LFC process. The results showed that the LFC under vacuum and low pressure evidently improved the filling ability and solved the oxidization problem of the alloys, which is suitable for producing complex and thinwall castings. The vibration and pressure solidifications increased the compactness of the castings and refined the microstructure, significantly improving the mechanical properties of the castings. The expendable shell casting technology could solve the pore, carburization, and inclusion defects of the traditional LFC method, obtaining castings with acceptable surface quality. Moreover, the Al/Mg and Al/Al bimetallic castings with acceptable metallurgical bonding were successfully fabricated using the LFC process. These proposed novel LFC technologies can solve the current technological issues and promote the technological progress of the LFC process.     

Effect of vibration after filling on mechanical reliability in thin wall investment casting with fillability filling regime—part 1

A vibration technique is used in this study to explore the effect of low frequency vibration on the mechanical reliability of Al-7Si-Mg castings. The quality of castings is related to the number and the size of porosity and oxide film in thin wall investment casting. The quality of each method of casting (casting with and without vibration) was assessed by the density of the defects within the thin strips. Weibull distribution function is used to analyze the tensile strength data. The Weibull modulus is applied as a criterion to assess the mechanical reliability to identify the optimized casting condition. The results show that the effect of the vibration on the mechanical reliability is markedly dependent on acceleration of vibration, and the Weibull modulus is in the range of 12 to 12.7 when the acceleration is in range of 0 to 1 g; however, in more than 1 g, the range is 30–35.     

Plaster casting process for prototyping of die casting based on rapid tooling

Rapid prototyping (RP) combined with a gravity casting process can provide a suitable substitute with steel tool die casting for prototyping metal casting. Due to differences between die casting and gravity casting, there are several drawbacks in RP simulated die casting. This paper is concerned with the development of a new plaster die casting process that combines pressurization and vibration for prototyping of die castings, and with a plaster die casting machine that has a structure similar to that of a die casting machine. The machine utilizes an oil cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the laminated object manufacturing (LOM) process to prepare a plaster mold. In the process, a plunger in the developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine has produced a prototype of an end clutch cover with remarkable improvement in mechanical properties.     

Plaster casting process for prototyping of die casting based on rapid tooling

Rapid prototyping (RP) combined with a gravity casting process can provide a suitable substitute with steel tool die casting for prototyping metal casting. Due to differences between die casting and gravity casting, there are several drawbacks in RP simulated die casting. This paper is concerned with the development of a new plaster die casting process that combines pressurization and vibration for prototyping of die castings, and with a plaster die casting machine that has a structure similar to that of a die casting machine. The machine utilizes an oil cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the laminated object manufacturing (LOM) process to prepare a plaster mold. In the process, a plunger in the developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine has produced a prototype of an end clutch cover with remarkable improvement in mechanical properties.     

Influence of gas flowrate on filling ability and internal quality of A356 aluminum alloy castings fabricated using the expendable pattern shell casting with vacuum and low pressure

In this study, a new casing process named expendable pattern shell casting process with vacuum and low pressure (EPSC-VL) was introduced to produce complicated and thin-walled aluminum alloy castings. The gas flowrate is one of the most important process parameters for manufacturing castings during the EPSC-VL process. In the present work, the influence of gas flowrate on the filling ability and internal quality of A356 aluminum alloy castings fabricated by the EPSC-VL process were investigated. Moreover, the filling ability, internal quality, as well as mechanical properties of A356 aluminum alloy castings obtained by EPSC-VL and lost foam casting (LFC) processes were also compared. The results obtained suggested that the filling length increased with the increase of gas flowrate, and the filling length of the thick section was larger than that of the thin section under the same gas flowrate when the gas flowrate was less than 19 m³/h. Furthermore, the porosity of castings decreased with increasing gas flowrate, and the microstructure of castings became denser, and the internal quality of castings was obviously improved. The comparison experiments showed that the EPSC-VL process had superior filling ability, internal quality, and mechanical properties compared with the LFC process, and the surface quality of castings obtained by EPSC-VL process was also better than that of the LFC process. The casting practice of complicated and thin-walled A356 aluminum alloy intake manifold part also suggested that the EPSC-VL process had an obvious advantage for the fabrication of complicated and thin-walled aluminum alloy castings compared with the LFC process.     

Optimization of high-pressure die-casting process parameters using artificial neural network

High-pressure die casting is a versatile process for producing engineered metal parts. There are many attributes involved which contribute to the complexity of the process. It is essential for the engineers to optimize the process parameters and improve the surface quality. However, the process parameters are interdependent and in conflict in a complicated way, and optimization of the combination of processes is time-consuming. In this work, an evaluation system for the surface defect of casting has been established to quantify surface defects, and artificial neural network was introduced to generalize the correlation between surface defects and die-casting parameters, such as mold temperature, pouring temperature, and injection velocity. It was found that the trained network has great forecast ability. Furthermore, the trained neural network was employed as an objective function to optimize the processes. The optimal parameters were employed, and the castings with acceptable surface quality were achieved.     

复合铸造技术在特种产品上的应用

介绍了将复合铸造技术运用到航空炸弹中的复杂工件,特别是大型薄壁铝合金舱体的优势。分析了石膏型熔模铸造结合真空增压技术的特点,同时,采用该技术研制大型复杂薄壁铝合金铸件,通过合理设计铸件浇注系统,选择铸型工艺,优化浇注工艺参数和严格控制固溶处理温度与校形时机,提高了铝合金的充型能力,改善了铸件的致密度和针孔度,解决了大型薄壁铸件充型及内部质量难以控制的难题。     

Optimization of green sand casting process parameters of a foundry by using Taguchi��s method

An optimization technique for process parameters of green sand casting of a cast iron differential housing cover based on the Taguchi parameter design approach is proposed in this paper. The process parameters considered are green strength, moisture content, pouring temperature, and mould hardness vertical and horizontal. An attempt has been made to obtain optimal level of the process parameters in order to yield the optimum quality characteristics of the cast iron differential housing cover castings. An orthogonal array, the signal-to-noise (S/N) ratio, and analysis of variance are used to analyze the effect of selected process parameters and their levels on the casting defects. The results indicate that the selected process parameters significantly affect the casting defects of grey cast iron differential housing cover castings. A confirmation run is used to verify the results, which indicated that this method is more efficient in determining the best casting parameters for differential housing cover.     

爆发器孔座近凝固点浇注工艺技术研究

针对采用传统浇注工艺生产某产品爆发器孔座中存在的问题,按照为解决浇不满、缩孔、缩松以及夹杂和针孔等问题,而对浇注温度、铸型温度和保温温度等工艺参数进行调整的思路,通过对试验结果进行对比分析,大胆突破了传统浇注工艺中浇注温度和铸型温度要求的束缚,研究形成了爆发器孔座近凝固点浇注工艺,并对其中包含的减少缩孔、缩松,提高充型能力,以及减少氧化夹杂和针孔的机理、工艺过程、效果评价和创新点进行了阐述。     

新型铝硅基铸造壳体凝固成形研究

新型铝合金材料用于薄壁壳体铸件制备,通过向ZL101A合金中增添微量Ni元素,基于ProCAST铸造仿真软件设计液压泵壳体低压铸造工艺,数值模拟铸件不同部位固相出现时间,并预测铸件凝固过程中缩孔缩松现象。实际生产铝合金薄壁壳体铸件,并对壳体棒料进行高温压缩实验,利用结构变形机理以及微观组织特点分析铸件凝固成形机理。分析合理的浇注温度以及热处理工艺,能够对壳体铸件缩孔缩松现象进行有效控制,保证改进铝硅合金薄壁壳体铸件质量。     

Thermodynamic Behavior Research Analysis of Twin-roll Casting Lead Alloy Strip Process

The thermodynamic behavior of twin-roll casting(TRC) lead alloy strip process directly affects the forming of the lead strip, the quality of the lead strip and the production efficiency. However, there is little research on the thermodynamics of lead alloy strip at home and abroad. The TRC lead process is studied in four parameters: the pouring temperature of molten lead,the depth of molten pool, the roll casting speed, and the rolling thickness of continuous casting. Firstly, the thermodynamic model for TRC lead process is built.Secondly, the thermodynamic behavior of the TRC process is simulated with the use of Fluent. Through the thermodynamics research and analysis, the process parameters of cast rolling lead strip can be obtained: the pouring temperature of molten lead: 360–400 °C, the depth of molten pool: 250–300 mm, the roll casting speed: 2.5–3 m/min, the rolling thickness: 8–9 mm.Based on the above process parameters, the optimal parameters(the pouring temperature of molten lead:375–390 °C, the depth of molten pool: 285–300 mm, the roll casting speed: 2.75–3 m/min, the rolling thickness:8.5–9 mm) can be gained with the use of the orthogonal experiment. Finally, the engineering test of TRC lead alloy strip is carried out and the test proves the thermodynamic model is scientific, necessary and correct. In this paper, a detailed study on the thermodynamic behavior of lead alloy strip is carried out and the process parameters of lead strip forming are obtained through the research, which provide an effective theoretical guide for TRC lead alloy strip process.     

Design and Verification of an Auxiliary System for High Vacuum Die Casting

Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this research.The model has an aggregate unit consisted of "vacuum pump + buffer tank" and a cylindrical container(including the shot sleeve,cavity and exhaust channel).The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume models.An auxiliary system for high vacuum die casting is designed based on the above analysis.This system is composed of a vacuum control machine and a new vacuum stop valve.The machine has a human-computer control mode with "programmable logic controller(PLC) + touch screen" and a real-time monitoring function of vacuum degree for buffer tank and die cavity.The vacuum stop valve with the "compressed gas + piston rod + labyrinth groove" structure can realize the function of whole-process vacuum venting.The new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly decreased.The systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.     

镁合金真空低压消失模铸造新技术

介绍了一种新的铸造技术--真空低压消失模铸造的工作原理.建立了其在充型过程中的物理模型与数学模型,分析了其铸造工艺的特点及影响因素,以及在铸造高精度、复杂镁合金铸件方面的优势.作为压力铸造、低压铸造的补充,真空低压消失模铸造新技术在铸造高质量和高精度的镁合金铸件中具有广泛的应用前景,另外还可用于铸造高精度、复杂的铝合金铸件.展示了用该新技术铸造成形的复杂的电机壳体、排气管等镁合金铸件.     

金属压铸模温度场的数值模拟研究

以铝合金的常用浇注温度为基础,研究了浇注温度及预热温度逐步升高或降低时,压铸模温度场的分布和变化情况。以生产中常见的方盒类铝制压铸件为例,运用有限元分析软件ANSYS,对其压铸模进行压铸过程的温度场分析。实验表明,该数值模拟得到了较合理的生产工艺参数,从而达到提高铸件质量、延长模具使用寿命的目的。     

Optimization of green sand casting process parameters by using Taguchi’s method

This paper analyses various significant process parameters of the green sand casting process. An attempt has been made to obtain optimal settings of the green sand casting process in order to yield the optimum quality characteristics of the spheroidal graphite (SG) cast iron rigid coupling castings. The process parameters considered are: green strength, moisture content, permeability and mould hardness. The effect of selected process parameters and its levels on the casting defects and the subsequent optimal settings of the parameters have been accomplished using Taguchi’s parameter design approach. The result indicates that the selected process parameters significantly affect the casting defects of SG cast iron rigid coupling castings. The estimation of the optimum performance characteristics of green sand casting at the optimum levels of parameters is done in this paper and the results are verified by confirming with practical experiments.     

负压实型铸造铸铁件充型过程的研究

从试验的角度出发,设计和探讨适合于研究负压实型铸造高熔点铸铁合金充型过程的研究方法.根据负压实型铸造的工艺方法,分别设计了电阻模拟法、激冷法和电极触点法.结果显示,电极触点法是一种研究负压实型铸造铸铁件充型过程的较好方法.     

STUDY ON NUMERICAL SIMULATION OF MOLD-FILLING AND SOLIDIFICATION PROCESSES OF SHAPED CASTING

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Design optimization of clutch housing mold by fluid flow and solidification simulation

Aluminum die casting is so complex where flow momentum is critical matter in the mould filling process due the high velocity of the liquid metal. Actually, in complex parts the exact calculation of mould filling performance with using experimental knowledge is almost impossible. Aluminum die castings play a definitive role in the manufacturing of lightweight automobile bodies. Hence it is more essential today that these castings be produced with the high quality methods. In this condition the simulation is becoming more important in the designing procedure. This saves time and reduces the cost of the casting system design, which is an advantage of using simulation programs. Also, economical utilization of materials can be obtained when the quantity of test castings is decreased. This paper describes the advantages of the clutch housing die casting mold simulations to achieve better casting system design in High pressure die castings (HPDC). Filling analysis is used to determine the size and location of the gate as well as proper runner system design for ensuring a complete and balanced filling of the clutch housing part.