铸件充型凝固过程的数值模拟研究在国际学术界已占有一席之地

研究了各种铸造条件下缩孔，缩松形成规律及机理，并建立相应判据。提出了定量预测球墨铸铁件缩孔的新方法，即动态收缩膨胀叠加法，并建立了数学模型。根据结晶及相变动力学理论，建立了预测球墨铸铁件铸态组织及机械性能的数学模型。     

球墨铸铁制压力容器国内外法规标准比较

球墨铸铁因其良好的力学性能和铸造性能,被越来越多地应用于制造压力容器,球墨铸铁制压力容器相关标准也开始引起业内的重视。基于美国ASME Ⅷ-1和欧盟EN 13445—6的球墨铸铁制压力容器标准,结合国内相关标准和TSGR0004-2009《固定式压力容器安全技术监察规程》,分析比较各国球墨铸铁制压力容器法规标准在适用范围、材料、设计、制造、检验与验收等方面的异同,指出了欧盟标准EN13445—6所采用的应力分析设计、疲劳分析及无损检测方面的先进之处,同时对我国制订球墨铸铁制压力容器相关标准提出了一些建议。     

Comparative research on wear characteristics of spheroidal graphite cast iron and carbon steel

Wear characteristics of a spheroidal graphite cast iron and a carbon steel were studied under atmospheric conditions at 25–400 °C. The spheroidal graphite cast iron presented obviously different wear behaviors from the carbon steel, which may be attributed to the presence of graphite. With an increase of ambient temperature, tribo-oxides of carbon steel substantially increased and its substrate softened, thus severe wear, oxidative mild wear, oxidative wear and extrusive wear took turns to prevail. However, compared with carbon steel in the same case, tribo-oxides were markedly reduced in the spheroidal graphite cast iron, thus oxidative mild wear and oxidative wear did not appear due to the lack of oxides. It is suggested that less tribo-oxides in the spheroidal graphite cast iron may be attributed to the reduction of graphite to tribo-oxides during sliding.     

回归分析在活塞环石墨球径控制上的应用

根据对球墨铸铁活塞环碳硅当量CE值与球状石墨大小的数据分析,建立以球墨铸铁活塞环CE值为自变量、球径大小为因变量之间的回归模型,得到回归方程。采用最小二乘法解出回归参数,并检验线性关系的显著性,最后实现对被解释变量球径大小的区间进行预测,以及通过控制碳硅当量来得到要求的球径大小。     

凝固过程应力场模拟技术在大型铸钢件中的应用

基于FDM／FEM方法，对某水轮机下环铸件的整个铸造过程中的热应力进行了模拟计算。模拟中采用接触单元法处理铸件与砂芯之间力的作用，改进了传统的铸件／铸型边界条件处理方法。根据应力场模拟结果，分别采用不同的判据，对铸件整个凝固、冷却过程中的热裂和冷裂倾向性进行了预测。揭示了铸件从凝固到冷却至室温的变形规律，为控制铸件收缩尺寸提供了参考。实际生产结果与预测结果相吻合。     

A metallurgical evaluation of tool wear and chip formation when machining pearlitic grey cast irons with dissimilar graphite morphologies

The need for superior in-service strength has meant that an increasing number of engineering components are now being made from pearlitic cast irons containing spheroidal graphite, rather than the more traditional cast irons containing flake graphite. Such changes of workpiece material have resulted in a rapid decline in tool life in many machining operations, particularly turning and facing.An investigation into the factors involved during chip formation which result in the observed patterns of tool wear is described in the work presented here. A series of turning tests were made on pearlitic grey cast irons containing flake (GA iron) and spheroidal (SG iron) graphite morphologies with cemented carbide (coated and uncoated) and ceramic tool materials. Built-up edge persisted to higher cutting speeds when cutting SG iron than GA iron, its periodic detachment causing attrition or fracture of the cutting edge. Smooth wear processes, probably caused by dissolution-diffusion and small strain discrete plastic deformation, were predominant on the rake and flank faces of the coated and ceramic tools when cutting both cast irons at high speed. Smooth wear was less rapid when cutting GA iron than SG iron because tool temperatures were reduced and “protective” nonmetallic layers, deposited from the chip-workpiece, interrupted dissolution-diffusion. When cutting SG iron, rapid wear of the uncoated cemented carbides was caused by attrition, while the relatively slower smooth wear, when cutting GA iron, was caused by dissolution-diffusion.     

铸铁中石墨形态和石墨结构的研究

采用扫描电子显微镜,通过深腐蚀和热腐蚀方法,研究了铸铁中各种典型石墨（片状石墨、蠕虫状石墨和球状石墨）的立体形貌和内部结构特征。对于片状石墨来说,A、C、D型均属同一种石墨形态,它们都是由分枝而又互相联系的石墨片组成,它们主要是沿着[1010]方向长大。对于球状石墨来说,用纯镁、纯钇、纯铈和工业球化剂均能得到球状石墨。热腐蚀结果表明,石墨球呈年轮状结构,它是由许多角锥体组成的多面体。这说明,石墨球的外表是（0001）面,石墨球的长大是由中心沿[0001]方向进行。蠕虫状石墨是介于片状和球状石墨之间的中间石墨形态。它的长大方式也介于片状和球状石墨之间。就石墨片的互相联系和彼此分枝情况来看,它与片状石墨相似,但就每个石墨片局部的长大方式来看,它又与球状石墨有某种程度的相似,即沿着[0001]方向长大较充分。     

Cavity optimization for investment casting die of turbine blade based on reverse engineering

A cavity optimization method based on the principle of reverse deformation was prompted in this paper. In the reverse deformation method, the displacement which represents the nonlinear shrinkage was superposed on the initial profile of cavity and compensated the shrinkage of wax and alloy solidification. Moreover, an estimation algorithm was prompted to calculate the displacement based on reverse engineering, and its key technologies such as blade measurement, model registration, and statistical analysis of the displacement were investigated. Finally, a sample application was presented for demonstration in this paper.     

铸件凝固过程的微型计算机模拟及铸件缩孔、缩松预测

本文作者在IBM PC/AT、XT微型计算机系列上开发铸件凝固2维数值模拟软件。计算中采用了变时间步长计算模型,使计算速度提高1～2倍以上。文中对铸件缩孔、缩松的预测方法做了进一步分析和讨论,并针对一铸钢件的凝固进行了计算和验证。     

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。     

Effect of structural features on erosion resistance of cast irons

Erosion resistance of four types of cast iron of different microstructures and graphite morphologies (viz., grey cast iron, compacted graphite iron, spheroidal graphite iron and austempered ductile iron) was evaluated in three different erosive media. Results indicate that austempered ductile iron has the highest erosion resistance in all three media, followed by spheroidal graphite iron, compacted graphite iron and grey cast iron, in that order. Graphite morphology has a significant effect on the erosion resistance of these irons in quartz-water and iron oxide-oil slurry. However, the matrix microstructure determines the erosion resistance of these irons in quartz-oil slurry. The parameter H/E (which is the ratio of the Brinell hardness number to Young's modulus of the material) has been found to be a good indicator of erosive wear in quartz-oil slurry.     

片状石墨铸铁的异质形核

采用液淬微分热分析法研究了片墨铸铁中片状石墨的形核过程。结果表明,片状石墨的初始形态为团球状,孕育剂的作用主要是增加石墨的异质形核能力。对片墨雏晶的检测分析说明：可作为片墨结晶的异质核心主要有锰的硫化物、硅的氧化物和钙的碳化物三类,其中复合硫化物是最为有效的异质晶核。并由此提出了设计较为理想的灰口铸铁用孕育剂的合理原则,根据这些原则研制的孕育剂经使用效果是理想的。     

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.     

Abrasion and impact properties of partially chilled gray iron

This paper reports the results of laboratory tests carried out to evaluate the abrasion wear resistance and impact properties of partially chilled gray iron (PCGI). Even though the impact property may not be an important characteristic for this type of material, the purpose of this characterization is to compare it with the one obtained for partially chilled ductile iron (PCDI). This allows to evaluate the influence of graphite morphology on the impact resistance of a chilled matrix and also, based on this knowledge, to choose for the lower cost variant when possible. The versatility of the casting process allows the use of chills (also referred as coolers) at specified locations in the mold, in order to increase the solidification rate and, in consequence, to promote the precipitation of carbides for an improved abrasion resistance. Two different heats, alloyed and unalloyed, were studied. Besides abrasion and impact properties, an exhaustive microstructural analysis was carried out, evaluating the carbide content, matrix phases and graphite morphology. The impact toughness was low due to the high carbide content and graphite type, but only a bit lower than that determined for similar microstructures and carbide content with spheroidal graphite (PCDI). The abrasion resistance of PCGI under the current experimental conditions (ASTM G 65 standard) was of the same level as determined for PCDI for the regions close to the cooler (<20 mm), but lower for regions located at a higher distance (>20 mm) due to the wear concentration promoted by the graphite morphology.     

球墨铸铁件微观组织的数值模拟

根据凝固动力学理论,建立和完善了球墨凝固过程中各阶段组织形成的数学模型。用试验试件进行了验证,并对实际生产球墨铸铁件的球墨数量和大小、珠光体和铁素体数量、硬度等进行了模拟,与定量金相分析结果进行了比较。结果表明模拟结果与分析结果吻合较好,同时,共析模型尚有待进一步改进以更准确地预测珠光体和铁素体数量。研究表明：球墨的形核与生长主要与过冷有关,共析阶段产生的珠光体与铁素体体积分数则由过冷度与球墨个数两者所决定。     

面向大型压铸模型腔壁厚的模糊优化设计

运用多目标模糊优化设计的原理,结合大型压铸模的工作条件,建立了逼近实际工况的型腔壁厚数学模型。采用最优水平截集法求解,并用复合形法进行优化。并给出了这种设计方法应用于潜望镜镜身铸件压铸模的工程实例。     

球墨铸铁齿轮的寿命试验

本文综合了作者最近进行的近100对球铁齿轮寿命试验的结果数据,从而得到了各种球铁齿轮接触疲劳和弯曲疲劳的S－N曲线以及具有一定失效概率的疲劳极限值σ (Hlin)和σ (Flim)。本试验得到的软氮化球球铁齿轮和贝氏体球铁齿轮的σ (Hlin)和σ (Flim)值,可供增补ISO60/6N200E和ISO60/6N201E数据不足的参考。     

蠕虫状石墨铸铁的结构

本文对蠕墨铸铁进行深腐蚀和热氧腐蚀,并用扫描电子显微镜进行观察研究,揭示了蠕虫状石墨的三维立体形貌和内部晶面取向特征。通过共晶团腐蚀,观察了这种铸铁的共晶团数量和结构特点。结果表明,用各种含有稀土元素的变质剂处理均可得到蠕虫状石墨,其端部具有球状石墨的生长特征,在同一共晶团内部,各蠕虫石墨片间互相联系,这又类似于片状石墨。热氧腐蚀试验表明,蠕虫状石墨端部（0001）面沿圆周方向分布,呈年轮状排列。在枝干分部,则（0001）面沿着枝干方向分布,但其方向变化频繁,呈多晶体。据此,作者提出了蠕虫状石墨晶面取向的模型。蠕墨铸铁的共晶团数量介于灰铸铁和球墨铸铁之间,共晶团的结构也兼有片状石墨和球状石墨两者共晶团的特征。为此,作者也提出了相应的模型。     

连铸球墨铸铁扭转缺口强度的研究

研究了一种用水平连铸技术生产的球墨铸铁型材的扭转强度和缺口扭转强度。实验发现光滑扭转试样是沿４５°方向开裂,开裂面是最大拉应力面,表现为典型的脆性断裂。缺口试样的断裂模式分两种情况：当为钝缺口时（即（ρ≥０．７５ｍｍ,Ｋｔ≤１．６）,其断裂特征与光滑试件相同;而当为尖锐缺口时（即ρ＜０．３７５ｍｍ,Ｋｔ＞２．１）的开裂出现在缺口根部,并且开裂面垂直于轴线方向,是剪应力作用。实验结果还表现出扭转缺口强度与应力集中系数的关系,即应力集中系数越大,扭转缺口强度反而越高。该球墨铸铁的缺口敏感性（ＮＳＲ）大于１,故缺口完全不敏感。     

数字图像复原技术中点扩展函数的改进

研究了在提高显微图像复原效果的过程中对光学系统点扩展函数测量方法的改进。采用自制点光源的方法,先后利用长焦距镜头远距离成像以及显微镜头近距离拍摄,分别获得光学系统的点扩展函数灰度图,并用于球墨铸铁表面金相结构图的复原,结合最大似然反卷积算法,验证了后一种点扩展函数测量方法的优越性。