淬火钢的高精密切削加工适用于金属铸模部件的精加工

利用高精密度加工法就能使已被高硬度淬火过的模具减低制作成本，而且还能缩短加工时间。东芝公司是利用工具运转的高速化，仇刃包覆材料的选定，包覆膜粘附力的提高，工具轨道的合理化，校正工具刀刃摩耗耗尺寸的误差等方法，开发成功对高硬度锻模材料能进行高精密度切削加工的新技术。

车加工用多球金属铸模夹具

铸造生产耐磨铸球,模具是关键。模具质量的高低直接影响铸球的外表、内在质量和正品率的高低。我公司经过多年的探索,从原来的木模造型、单球金属模造型,最后改进为一模多球金属铸模生产各类规格的耐磨铸球,提高了生产效率,满足了产品质量的要求,取得了令人满意的经济效益。 一模多球金属铸模,可进行车加工亦可铣加工。由于铸模的坯料一般采用铸钢、耐热铸铁制成,其表面硬度较高。在模坯球面内粘砂较多,若用铣削方法加工内球面,刀具的磨损率很高,其辅助工装夹具相对车床加工要复杂些。

球磨机磨球金属型铸模的加工方法

本文在对球磨机磨球金属型铸模的技术要求进行分析的基础上 ,制定出在普通机床上批量生产金属型铸模的切削加工工艺 ,以及专用工装、夹具及特殊刀具 ,取得简化操作程序 ,提高工效 ,降低生产成本的显著效果。

CATIA在金属浇铸模CAD/CAM中的应用

模具CAD/CAM集成技术是一项重要的模具先进制造技术,CATIA作为高端的CAD/CAM软件,具有精准的三维建模功能和强大的数控加工能力,本文以金属浇铸模为主要研究对象,提出了一种基于CATIA为平台的模具设计与加工的方法。

Microstructure and mechanical properties of Mg-Gd-Y-Zr alloy cast by metal mould and lost foam casting

The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr （mass fraction, %） alloy （GW104 alloy） cast by metal mould casting （MMC） and lost foam casting （LFC） were evaluated, respectively. It is revealed that different forming modes do not influence the phase composition of as-cast alloy. In the as-cast specimens, the microstructures are similar and composed of α-Mg solid solution, eutectic compound of α-Mg＋Mg 24 （Gd, Y） 5 and cuboid-shaped Mg 5 （Gd, Y） phase; whereas the average grain size of the alloy produced by metal mould casting is smaller than that by lost foam casting. The eutectic compound of the alloy is completely dissolved after solution treatment at 525 ℃for 6 h, while the Mg 5 （Gd, Y） phase still exists after solution treatment. After peak-ageing, the lost foam cast alloy exhibits the maximum ultimate tensile strength of 285 MPa, and metal mould cast specimen 325 MPa at room temperature, while the tensile yield strengths of them are comparable. It can be concluded that GW104 alloy cast by lost foam casting possesses similar microstructure and evidently lower mechanical strength compared with metal mould cast alloy, due to slow solidification rate and proneness to form shrinkage porosities during lost foam casting process.

乙酸与碳酸盐岩基质酸化注入速率特性研究

碳酸盐油藏常规基质酸化一般使用盐酸来消除近井地带的伤害。许多实验和理论研究都证明在碳酸盐里基质酸化存在最优注入速率,以便形成合理的酸蚀蚓孔,从而使增产效果达到最优。最优注入速率取决于油藏本身情况,岩石物性和化学反应速率。在高温条件下盐酸的反应速率很快,这使得实际的盐酸注入速率通常超出设计的最优注入速率,从而导致施工设计失败。在这种情况下,弱酸如乙酸,就成为高温深井酸化增产的替代性流体。目前的理论模型表明,弱酸的最优注入速率相对强酸的最优注入速率要低得多。

INVESTIGATION OF FOAM-METAL INTERFACE BEHAVIORS DURING MOLD FILLING OF MAGNESIUM ALLOY LFC PROCESS

The visual observation of the mold filling and the standard analysis-of-variance （ANOVA） for the velocity of the filling metal are conducted to study foam-metal interface behaviors during the mold filling of the lost foam casting （LFC） process of the magnesium alloy. Results show that the foam primarily melts into liquid products instead of gasifying at the pouring temperature of the magnesium alloy. Without the vacuum, the metal fills smoothly with a slightly convex metal front, and the velocity of the filling metal is low and continually decreases as the foam is displaced. The mold filling is governed by the removal of foam decomposition products at the foam-metal interface. However, when the vacuum is applied, the mold filling is controlled by the foam decomposition rate at the foam-metal interface. A pronounced irregular and concave metal front is formed. The velocity of the metal front varies tremendously during the mold filling process and is ruleless. The metal velocity increases rapidly, and the vacuum shows a strong interaction effect with the pouring temperature on the metal velocity. As the vacuum continues to increase, the pouring temperature becomes the most significant factor for the mold filling, while both the vacuum effect and the interaction effect between the vacuum and the pouring temperature on the metal velocity are substantially reduced. Based on experimental results, a model for the foam thermal degradation and the removal of decomposition products occurred at the foam-metal interface is presented during the mold filling of the magnesium alloy LFC process under the vacuum.

An Alternative Method for SU-8 Removal Using PDMS Technique

An alternative method for SU-8 removal is proposed.Instead of directly using SU-8 microstructure as the electroplating mold,a polydimethysiloxane (PDMS) replica is employed.The metallic micromold insert obtained through this method can be easily peeled off from the PDMS replica,meanwhile with high resolution and smooth surfaces.

粉末冶金在北美

粉末冶金在北美［美］ＤｏｎａｌｄＧ．Ｗｈｉｔｅ１概述自１９９２年世界Ｐ／Ｍ大会在北美召开以来，回顾过去数年的发展，粉末冶金和粒状材料业已经历了一个惊人的发展和收获时期，并且前景仍然乐观。粉末冶金作为一个行业和一门技术已趋成熟并逐渐显示其预计的前所未有...

G427发动机气缸盖上水套芯热芯合的数控加工

铸模制造一向沿用钳工划线、机加工及钳工修整或由木模铸造的传统工艺方法。随着汽车产品更新换代的加速,要求汽车关键零件(如发动机缸体等)的铸件产品具有更高的尺寸精度和更快的加工周期。为了达到上述目的,只有采用先进的 CAD/CAM 技术,才能从铸造模具的开始阶段确保铸件制造的高质量和低成本。一台工程工作站和一台数控铣床构成我厂的 CAD/CAM 系统,其核心软件是

新型双楔式侧抽芯机构的研制

新型双楔式侧向抽芯机构既不同于斜导柱等机械抽芯机构,又不同于纯液压抽芯机构,而是采用机械与液压相结合的方式,利用液压为动力驱动机械抽芯机构,从而实现合模锁紧与开模抽芯。这种新型侧抽芯机构可大大减小液压缸尺寸,结构紧凑,避免了与注射成型机有关部件的干涉,同时方便侧抽芯型芯的制造、修配和调整。

Microstructural examination and mechanical properties of replicated aluminium composite foams

Open-cell aluminium foams can be produced with the structural replication of dimensional accuracy from polymeric foam patterns through a pressure infiltration casting process.The strength of open-cell foam is much less than that of the closed-cell counterpart,and thereby subjects to mainly functional applications.An improvement in mechanical properties of the foams can be implemented with the addition of ceramic particles.In the present study,the composite foams were produced using AC3A alloy added with varying contents of SiC particles.The resultant foams have ceramic particles embedded in the alloy matrix and on the strut surface.Higher volume fraction of ceramic particles resulted in an increase in the compressive strength,energy absorption and microhardness of the foams.The improvement of these properties is due to the modification of the microstructure of the foams and the increased strength in the node and struts at which the ceramic particles reside.

Simulation and experimental verification of interfacial interactions in compound squeeze cast Al/Al-Cu macrocomposite bimetal

The objective of this work was to investigate the thermal and mechanical interactions between the two components of a compound squeeze cast macrocomposite bimetal. First, an Al/Al-4.5wt.%Cu macrocomposite bimetal was fabricated by compound squeeze casting process. Then, heat transfer, solidification and distribution of the generated stresses along the interface region of the bimetal were analyzed using Thermo-Calc, ProCAST and ANSYS softwares, and structure, copper distribution and microhardness changes across the interface of the bimetal were studied. The results showed no noticeable change in the structure of the Al-4.5wt.%Cu insert and no obvious micromixing and diffusion of copper across the interface. Simulation results were in good agreement with the experimental ones only when an equivalent oxide layer at the interface was defined and its effect on heat transfer was considered. This layer caused up to 50% decrease in local liquid fraction formed on the surface of the insert. Simulation of the generated stresses showed a uniformly distributed stress along the interface which was significantly lower than the compressive strength of the oxide layer, resulting in its good stability during the fabrication process. It was postulated that this continuous oxide layer not only acted as a thermal barrier but prevented the direct metal-metal contact along the interface as well.

Effect of different processing parameters on interfacial heat-transfer behavior in high-pressure die-casting process

Vacuum die casting can reduce the'air entrapment'phenomenon during casting process.Based on the temperature measurements at metal-die interface with different processing parameters,such as slow shot speed(VL),high shot speed(VH),pouring temperature(Tp)and initial die temperature(Tm),inverse method was developed to determine the interfacial heat transfer coefficient(IHTC).The results indicate that a closer contact between the casting and die could be achieved when the vacuum system is used.It is found that the vacuum could strongly increase the values of IHTC and decrease the grain size in castings.The IHTC could have a higher peak value with increasing the Tp from680to720℃or the VL from0.1to0.4m/s.In addition,the influence of the VH and Tm on IHTC could be negligible.

Numerical simulation and experimental verification of large-sized Zr-based bulk metallic glass ring-shaped parts in casting process

An outer ring of 29320 self-aliging roller bearing was used in an experimental study on the casting of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloy.Numerical simulations of mold filling and solidification processes were carried out to determine the velocity fields and temperature fields of the alloy melt during mold filling process as well as the temperature fields and temperature gradient fields in the course of the solidification.According to the results,a cast with a complete shape can be obtained at 1200℃under the condition that the cooling rate is greater than the critical cooling rate.The ring-shaped part with a thickness of 25 mm,an equivalent diameter of 22 mm,and a mass of 1.32 kg was prepared by gravity casting in a copper mold.X-ray diffraction and differential scanning calorimetry data revealed that the produced cast had the amorphous structure.

Microstructures and mechanical properties of Mg-10Ho-0.6Zr-xNd alloys

Mg-10Ho-0.6Zr-xNd (x=0, 1, 3 and 5, mass fraction, %) alloys were prepared by metal mould casting, and the microstructures and mechanical properties were investigated. The results show that the grain size of as-cast alloys reduces and the hardness and strength increase with the increase of Nd content. The alloys are aged followed by solid solution treatment. Mg-10Ho-0.6Zr-3Nd and Mg-10Ho-0.6Zr-5Nd alloys exhibit obvious age hardening response. The hardness value of Mg-10Ho-0.6Zr-5Nd alloy increases from HV104 at as-cast state to HV136 at peak-aged state. The maximum ultimate tensile strength and yield strength of the Mg-10Ho-0.6Zr-5Nd alloy are obtained in at peak-aged state, and the values are 323 MPa, 212 MPa at room temperature, and 258 MPa, 176 MPa at 250 ℃, respectively. The improvement of the tensile strength is mainly attributed to the fine and dispersively distributed plate-shaped β′ metastable phase.

Modelling and Control of Pressurized Molten Metal in Press Casting

This paper presents a modeling and control of molten metal＇s pressure in pressing process using an innovative iron casting developed by our group. In this method, molten metal is directly poured into a lower mold, and then pressed to fill cavity by an upper mold being lowered down. For complex liquid flow during pressing, the liquid＇s pressure changing inside vertical path with various contraction and expansion geometries is newly modeled via the unstationary Bernoulli equation. The mathematical model is derived for a control design of pressing. To conduct the pressing velocity design algorithm, an unknown parameter of proposed model considering viscous flow is identified by using CFD （Computational Fluid Dynamics） with heat flow calculation. Control performance using a multi-switching velocity pattern is confirmed as an effective control design using the pressure model, because the pressure fluctuation has discontinuous variation points. Substituting detailed information for mold shape, poured volume and initial temperature into a developed control input generator, an optimum pressing velocity design and a robust design for defect-free production are proposed by the design algorithm based on the construction of an inverse system comprised of the sequential switching from higher to lower speed. Consequently, the effectiveness of the pressing control with reasonable pressure suppression has been demonstrated through CFD.