运用均衡凝固理论解决英国铸件的缩孔问题

用实例给出运用均衡凝固理论,特别是薄、宽、短矩型冒口颈解决英国铸造厂球墨铸铁件的缩孔问题.表明均衡凝固理论作为工艺设计的理论和方法对生产高品质铸件有普遍意义.对计算机凝固模拟进行了讨论.计算机凝固模拟软件可以帮助设计人员改进工艺设计,提高铸件品质.但是认为购置和应用了计算机凝固模拟软件就能产生立竿见影的效果是对计算机凝固模拟软件的误解.在未来很长时期内,计算机凝固模拟作为一个有力的工具,仍然需要有实际铸造工艺设计经验的专家使用才能发挥其作用与潜力,才能达到预期效果.计算机凝固模拟软件与铸造工艺设计的专家系统软件和人工智能软件相结合将能够更好地解决铸造工艺设计问题.     

应用均衡凝固解决砧座缩孔问题

1．原铸造工艺概况砧座是C41－400B空气锤的关键零件，它在空气锤作业过程中，承受着空气锤锤头的打击力。因此，对站座要求吸震、耐疲劳、能承受空气锤作业时锤头多次连续的打击。C41－400B砧座的材质为HT150，重6吨，为实体大件，其结构如图1所示。图1C41－400B砧座示意图砧座的质量问题主要是缩孔。据1983统计，缩孔占当年40OB砧座废品的78％。当时我们生产4OOB砧座的工艺是采用地坑干型，根据顺序凝固的原则，将冒口放在最后凝固的热节处，其冒口采用热节圆法设计，考虑到放“示”字形内冷铁两个（重600kg），冒口尺寸适当放小，…     

基于均衡凝固理论设计球墨铸铁件冒口

介绍均衡凝固的基本原理，叙述铸件结构、冒口位置和冷铁对补缩的影响。结合铸件实例，说明合理设计冒口和利用冷铁使球铁铸件实现均衡凝固，防止缩孔、缩松的工艺方法。     

球铁曲轴显微组织模拟及缩孔缩松预测

球铁曲轴生产中 ,一般要求铸态基体组织中珠光体含量要大于 80 % ,铸态抗拉强度不小于 70 0 MPa,伸长率不小于 2 %。同时要求曲轴关键受力部位——曲拐处不能出现缩孔缩松。为了优化曲轴的生产工艺 ,本文采用 FTStructure软件对不同铸造方案的球铁曲轴铸态微观组织、力学性能及缩孔缩松形成倾向进行了模拟 ,对球铁曲轴的组织与性能进行了预测。1　工艺方案要进行模拟的是 6拐曲轴铸件 ,总长 84 3mm,主轴颈 5 0 mm,材质为 QT70 0 - 2 ,质量 5 4kg,采用 GF高压造型线生产。炉后成分为 :3.7%～ 3.9% C,1.8%～ 2 .2 % Si,碳当量 4 .3%～ …     

均衡凝固理论大铁模覆砂铸造大型空心球墨铸铁曲轴上的应用

介绍了铁模覆砂铸造大型空心球铁曲轴的工艺。采取平做，平浇，平冷和复合运用微量合金元素及多次孕育等技术措施，利用无衡凝固理论解决央轴内部缩松，获得合格曲轴铸件，并得到铸态珠光体组织。     

球铁差速器壳的均衡凝固铸造工艺

球铁差速器壳是泰山-12拖拉机的重要零件,其品质不仅影响到主机的性能,而且关系到铸造生产的经济效益.原采用传统的冒口补缩铸造工艺,成品率只有75%.作者对原工艺及其铸造缺陷进行分析,改用扁形内浇口、冒口、采用均衡凝固的铸造工艺,保证了铸件品质,提高了铸件成品率及工艺出品率,降低了生产成本,收到理想的效果.     

应用均衡凝固理论设计风电球铁轴承座铸造工艺

原热侧冒口热节放冷铁工艺设计的耐低温风电球铁轴承座,探伤检查废品率在20%以上,应用均衡凝固技术重新设计工艺,冒口离开热节,冒口颈处加冷铁,改中注为顶注,轴承座的探伤废品率降低到1.0%².0%之间。     

应用均衡凝固大孔出流技术消除球铁支承座缩凹缺陷

支承座是载重车的一个零件,质量3.3 kg,轮廓尺寸160 mm×100 mm×55 mm,平均壁厚16 mm,材质为QT600-3,不允许有缩孔、大面积缩陷、冷隔、浇不足及渣眼等缺陷.     

球铁后盖铸件缩孔缺陷的消除措施

分析认为球铁后盖铸件热节部位产生缩孔的原因是：原工艺在热节部位设置冒口,使热节增大;而且由于冒口颈偏小,早于铸件热节凝固封闭,使铸件热节不可能通过冒口颈获得补缩。为此采取如下改进措施：1）使冒口远离铸件热节,避免热节增大;2）在热节处设置厚大冷铁,使热节提早凝固收缩,从而可以通过冒口颈获得补缩。改进工艺后,缩孔问题得到了解决。     

Discussion on "proportional solidification technology" for nodular iron casting method

H ow should the graphitization expansion be reasonably utilized to feed nodular iron castings? H ow should the consideration be given to both feeding from feeders and self-feeding by expansion? These two problem s are the hot spotsofdiscussion on feeding m ethod ofnodulariron castings at present. In this regard, reference [1] published som e viewpointswhich cause differentcom m ents.W ith the wish to prom ote the discussion on shrinkage problem sofnodulariron castings and based on his investig…     

Hydrogen embrittlement of nodular cast iron

Ferritic nodular cast iron, intended for use as the material for inserts of canisters for long-term geological disposal of spent nuclear fuel, was studied for hydrogen sensitivity. In the canisters, the insert provides the mechanical strength against external loads. Hydrogen was charged from 0.1 N H₂SO₄ solution in free-corrosion tests and under controlled cathodic potential. Hydrogen uptake and trapping were then measured using thermal desorption spectroscopy. The hydrogen desorption rate after hydrogen charging manifests two distinct peaks. Plastic deformation during hydrogen charging increases the hydrogen uptake considerably. Hydrogen reduces the elongation to fracture and time to fracture in slow strain rate testing and constant load testing (CLT), respectively. Especially, the strain rate in CLT is dramatically increased. The appearance of hydrogen-induced cracking in the ferrite phase changes from ductile dimple fracture to brittle cleavage fracture due to hydrogen charging, which initiates from the interphases of the graphite nodules. The results are discussed in terms of the role of hydrogen and the graphite nodules in hydrogen embrittlement of ductile cast iron.     

On solidification and shrinkage of brass alloys

Abstract

The solidification process was investigated in brass alloys containing a wide range of zinc, between 32·5 and 47·1 wt-%. A series of solidification experiments was performed under different cooling rates using differential thermal analysis (DTA) and a confocal mirror furnace. The cooling rate and the solidification under cooling temperature were evaluated from cooling curves. Furthermore, the peritectic reaction was studied in view of the starting and the ending temperatures and shrinkage behaviour. The volume change was measured in the peritectic alloys using a dilatometer which was developed to investigate the melting and solidification processes. A theoretical analysis was developed to evaluate the volume change effect on the peritectic reaction.     

Strength distribution at interface of rotary-friction-welded aluminum to nodular cast iron

The morphology, size and composition of intermetallic compound at the interface of AI 1050 and nodular cast iron were studied by electron microprobe analysis（EMPA） and scan electron microscopy （SEM）, respectively. The bond strength of the interface was measured by the tensile tests and the morphology of the fracture surface was observed by SEM. The observation of the interface reveals that there are two distinct morphologies： no interrnetallic compound exists in the central area at the interface; while numbers of intermetallic compounds （FexAly） are formed in the peripheral area due to the overfull heat input. The tensile tests indicate that the distribution of strength in radial direction at the interface is irdaomogeneous, and the central area of the interface performs greater bond strength than the peripheral area, which proves directly that the FexAly intermetallic compounds have a negative effect on the integration of interface. The morphology on the fracture surface shows that the facture in the central area at the interface has characteristic of the ductile micro-void facture. So it is important to restrain the form of the intermetallic compound to increase the bond strength of the AI 1050 and nodular cast iron by optimizing welding parameters and the geometry of components.     

Structural analysis considering shrinkage defect of cast part

Abstract

Flow and solidification of fusion metal at high temperature may introduce defects in cast components. As a results, many components have unsound internal areas. However, most engineers do not consider the effect of shrinkage defects when designing components; it is generally assumed that the material is completely sound. The material property reduction method is one approach to taking into account the effect of unsound areas, but it cannot consider stress concentration effects around the shrinkage. To compensate for this limitation, a shape simplification method is proposed. The method reconstructs shrinkage defects as hollow spheroid primitives based on shrinkage shape data obtained from industrial computerised tomography. The shape simplification method offers a smaller number of elements than other methods for modelling of shrinkages, and is also able to calculate the stress concentration. The present study examines the effect of shrinkage on a component structure subject to practical loads. It is possible to improve the productivity and reliability of cast products by such considerations.     

高硼低碳铁基合金凝固组织研究

借助光学显微镜、扫描电镜、电子探针显微分析仪和X衍射分析等手段,研究了B含量＞1wt%和C含量＜0.2wt%的Fe-B-C铸造合金的凝固组织及合金元素的分布特征.研究发现,Fe-B-C铸造合金的凝固组织由硼化物、铁素体和珠光体组成,而且硼化物全部是Fe2B,显微硬度达到1430-1480HV,硼化物沿晶界呈网状分布.随着凝固冷却速度增加,凝固组织和硼化物明显细化.研究还发现,快速冷却条件下,硼化物数量减少,铁素体有增加趋势.另外,硼主要分布在硼化物中,基体中分布甚微.     

Influence of inoculation on solidification in cast iron

Abstract

Inoculation of cast iron has been mainly studied for the nucleus materials and the development of new inoculants. The effect is widely recognised; nevertheless, the mechanism was not fully understood. Inoculation leads to a decrease in chill depth, depressed the formation of D type graphite to form A type graphite and increase in the eutectic cell number. The transition from A type to the D type graphite is also accelerated by Ti addition; therefore we used Ti added samples for the study of D type graphite formation. The increase in the eutectic cell number produces a decrease in the cell size, namely the radius; nevertheless, the solidification time of the castings does not change by inoculation. Therefore, the solidification rate of the cell, namely the linear solidification rate, should decrease with inoculation and the decrease produces a depression in the chill and D type graphite due to the smaller undercooling. Therefore, we have to consider the three-dimensional solidification rate for discussing the cooling curve.