铬铁矿砂在大型铸钢件上的应用

通过对铬铁矿呋喃树脂砂的基础试验和生产实践,发现在大型铸钢件的厚大表面、热节及冒口根部采用铬矿呋喃树脂砂作面砂能有效的防止金属渗透粘砂,且型砂成本变化不大。     

Properties of silica sand and GBF slag moulds practiced by Nishiyama process

ABSTRACT

Investigations were carried out to use Granulated Blast furnace (GBF) slag as mould material for either full or partial replacement of existing silica sand in foundry industry. Nishiyama process was adopted for evaluating the same. A series of sand tests were carried out on sand and slag individually and also combinations of these two. Three types of moulds were made with sand, slag individually and combination of these two. Both laboratory and industrial castings of ferrous and non ferrous materials were performed. Results of mould permeability, compression and shear strength of GBF slag reveal that is a suitable candidate for either partial or full replacement of molding sand. During casting of both laboratory and industrial, neither fuse, dripping nor collapse of the mould walls was observed; this is true for both ferrous and non ferrous castings. Castings with good surface finish, no surface defects and porosity were made by slag moulds.     

A verification of the thermal stress analysis,including the furan sand mold,used to predict the thermal stress in castings

The restraint exerted on a casting by a furan sand mold on the casting and the contraction of the casting during cooling was dynamically and simultaneously measured using a device that we developed. The measurements were compared during cooling with thermal stress analyses. The thermal stress analyses were based on the representative mechanical models for the furan sand mold, i.e., the elastic and elasto-plastic models used in previous studies. The comparison demonstrated that the elasto-plastic model simulates the restraint force more accurately than the elastic model. In the thermal stress analysis, it was important to describe the development of inelastic deformation and the fracture of the sand mold. However, the simulated restraint force was still twice as large as the measured force even in the elasto-plastic model. This error is most likely attributable to using the temperature-independent mechanical properties of the furan sand mold and the mechanical model of the casting alloy, which neglected the viscoplasticity at high temperature in the thermal stress analysis.     

呋喃树脂砂工艺生产薄壁铸钢件表面热裂纹对基体疲劳寿命的影响

对呋喃树脂砂工艺生产薄壁铸钢件表面热裂纹形态和产生的原因进行了阐述。通过实验的方法重点研究了其对铸件的疲劳寿命的影响程度,为铸件的安全使用和修理提供了实验参照。     

Thermal stress analysis method considering geometric effect of risers in sand mold casting process

Solidification and fluid flow analysis using computer simulation is a current common practice. There is also a high demand for thermal stress analysis in the casting process because casting engineers want to control the defects related to thermal stresses, such as large deformation and crack generation during casting. The riser system is an essential part of preventing the shrinkage defects in the casting process, and it has a great influence on thermal phenomena. The analysis domain is dramatically expanded by attaching the riser system to a casting product due to its large volume, and it makes FEM mesh generation difficult. However, it is difficult to study and solve the above proposed problem caused by riser system using traditional analysis methods which use single numerical method such as FEM or FDM. In this paper, some research information is presented on the effects of the riser system on thermal stress analysis using a FDM/FEM hybrid method in the casting process simulation. The results show the optimal conditions for stress analysis of the riser model in order to save computation time and memory resources.     

Numerical study of macrosegregation formation of ingot cast in normal sand mold and water-cooled sand mold

Formation of macrosegregation of 5 t steel ingots cast in sand molds with and without water-cooled copper tube is simulated by solving macroscopic mass,momentum,species and energy conservation equations with the consideration of shrinkage formation.Predicted macrosegregation pattern of the ingots shows a fair agreement with the experimental data.Both calculations and experiments reveal that some positive segregation patches are formed at the bottom of ingot.With the water-cooled copper tube inserted in the ...     

防渗硫涂料的开发与应用

分析了现行的呋喃树脂砂生产K2转向架侧架铸造工艺和熔铸工艺条件对铸件表面质量的影响,结果表明,呋喃树脂砂引起铸件表面裂纹的主要原因是表面渗硫,为消除因渗硫引起的铸件表面裂纹缺陷,开发了防渗硫涂料。利用对比试验的方法对拟开发的防渗硫涂料的组分进行了优化,进而对防渗硫涂料的配方进行了优化,给出了最佳配方。对开发的防渗硫涂料进行了中试应用,证实开发出的防渗硫涂料可操作性强,性能可靠,防渗硫效果显著,防止裂纹产生效果好。     

The role of the pressure index in porosity formation in A356 alloy castings

Porosity formation in A356 aluminium plate castings was studied experimentally and theoretically. Analysis of a model introduced in this paper led to the formulation of a pressure index, P*, which was expressed in terms of the thermal parameters G, V_s and t_f (where G is the thermal gradient, V_s is the solidus velocity and t^ris the local solidification time), and the alloy's physical constants. The index, determined from the effects of local pressure drops based on Darcy's law and surface tension within the interdendritic liquid, was employed to estimate the formation of porosity in A356 alloy castings. The experimental and theoretical results indicated that porosity content is inversely proportional to P*, and that porosity content tends to decrease with increasing G^0.38/V^1.62 when this parameter is less than 0.05°C^0.38 min^1.62 cm^?2. As the value of G0.38/V1.62 is increased over approximately 0.05 °C^0.38 min^1.62 cm^?2, the porosity content was found to be independent of this parameter.     

消失模铸造直浇道掉砂问题的研究

运用伯努力方程计算出负压消失模铸造在浇注时直浇道与浇口杯接口处会出现比砂箱内的负压还高的真空度,在这一高真空度的作用下很容易把直浇道与浇口杯之间接口处的干砂吸入直浇道中,给铸件造成白色缺陷.解决的办法是:由于这一真空度高于砂箱内的值,故可不考虑该处涂层的透气性,增加其涂层厚度及强度以阻挡型砂流动,或者把直浇道与浇口杯制成一体,这样问题就得以解决了.     

选择性激光烧结工艺参数对影响铸造砂型精度的优化设计

阐述了选择性激光烧结(SLS)的成型原理,并将此成型方式运用于直接砂型制作。通过用自主研制的快速成型机进行烧结试验,采用正交试验和方差分析,对影响铸造砂型精度的工艺参数进行了优化设计,得到激光功率、扫描速度、扫描间距及铺粉厚度工艺参数的最佳组合,可为基于选择性激光烧结铸造砂型的制造提供指导和参考。     

Influence of furfuryl moulding sand on flake graphite formation in surface layer of ductile iron castings

The influence of the use of moulding sand with furan resin, prepared both with fresh sand and reclaimed matrix, on the formation of a flake graphite formation at the surface layer of ductile iron castings has been investigated. A series of experimental heats of ductile iron cast in moulds made of moulding sand characterised by different levels of surface active elements (sulphur, oxygen) were performed. The effect of the wall thickness and the initial temperature of the metal in the mould cavity on the formation of flake graphite in the surface layer of the casting is shown in the paper. Investigations carried out by means of scanning electron microscopy (energy dispersive X-ray spectroscopy and wavelength dispersive X-ray spectroscopy) showed concentration of gradient profiles of surface active elements in the castings surface layer, which are responsible for their quality. Finally, it has been shown that there exists a significant effect of the quality of the sand on the formation of the flake graphite layer and the surface characteristics of ductile iron castings.     

铸件充型过程数值模拟的实验验证及工程应用

采用ＳＯＬＡ－ＶＯＦ法,开发了Ｗｉｎｄｏｗｓ９８／ＮＴ环境下的铸件充型过程数值模拟软件ＦＴ－ＦＬＯＷ,模型中考虑了紊流流动。用标准测试件和阶梯试件对软件进行了验证,实验结果与数值模拟结果比较吻合。目前,铸件充型过程数值模拟软件ＦＴ－ＦＬＯＷ已经在许多厂家的实际生产中得到了应用。     

汽车门内板拉伸成形的数值模拟研究

使用UG对零件数模进行了工艺补充面设计,利用动态显式软件Dynaform对门内板拉伸成形进行了数值模拟研究;并根据模拟结果,分析了引起零件缺陷的原因,提出了工艺模具的优化方案.     

铸造3D喷墨打印砂型尺寸精度测量评定方法研究

随着铸造行业的转型发展,3D打印技术已经成熟的应用于制造铸造砂型,所制作的砂型不再单单作为铸造过程中的半成品,而是可以作为产品面向各铸造厂进行销售。但是目前对于砂型的检验标准存在缺失,对于砂型质量的把控和评定缺少依据。针对铸造砂型的尺寸精度,通过设计制作测量试块,给出了一种3D喷墨打印砂型的测量方法及评定标准,填补了目前铸造行业中这一领域在标准上的空白,对推动3D打印技术在铸造行业的应用以及砂型的产品化有着重要的意义。     

Numerical simulation for mold-filling of thin-walled aluminum alloy castings in traveling magnetic field

1 .IntrOdUction High一strength,light一weight and large一size alumimimalloy eastings are widely used in aviation,astronavigation,gUided missile and 50 on.With the develoPment of neweasting teehnology,it 15 imPortant     

数值模拟技术在新产品模具设计中的应用

对于新产品的模具设计主要是凭借丰富的生产实践经验，新产品的模具设计不可能一次成功，或多或少存在一些缺陷，使产品不能顺利成型。为了解决这个问题，利用Dynaform软件模拟了新产品的模具设计到产品成型的全过程，弥补了经验设计的不足，大大的缩短了模具设计制造周期，提高了工作效率，而且对类似新产品的模具设计具有一定借鉴作用。     

呋喃树脂砂酸催化剂催化活性的评估与测定

常用酸强度的表征方法不能反映呋喃树脂砂酸催化剂催化能力的强弱。根据酸催化原理，利用自行设计装置，测定酸催化甲酸分解生成一氧化碳的模拟反应的速度常数ＫＭ。理论分析与实测结果表明，ＫＭ值反映了酸的催化活性的大小，可作为制备或选用新的催化剂的依据。     

变模温模具温度场数值分析与加热参数选取

以缩短加热阶段时间、提高生产效率及产品质量为目的,以流体动力学为基础,应用数值计算与分析技术,分析了变模温注塑模具的温度场,比较了模具加热介质的流速,加热介质入口温度及加热时间。得到了合理的快速加热模具的参数,并获得了均匀的模具温度场,为提供良好的注塑成型条件打下基础。     

发泡模具射料充填过程的数值模拟

本文利用商业流体分析软件对多种情况下发泡模具的射料充填过程进行了数值模拟,物理模拟利用数码摄像机记录下射料充填的全过程,数值模拟结果与物理模拟结果对比表明,模拟的结果与实际情况基本上是一致的.