黄壤土天然粘土砂湿型铸造工艺的应用研究

当前铸造业所应用的粘土煤粉砂湿型铸造污染大、消耗量多、铸件表面质量差,不适应当前节能降耗减排的产业政策,探索资源节约型绿色铸造工艺具有重要的现实意义.黄壤土天然粘土砂是由黄壤土和矿渣混制而成的型砂,与传统的粘土煤粉砂相比,它在铸铁件的初步生产实践中表现出一系列优点:型砂可循环使用,废砂排放量少;铸件表面不粘砂,尺寸精度高,表面粗糙度低,生产效率高;砂源丰富可就地取材,生产能耗低.为实现黄壤土天然粘土砂湿型铸造工艺的大批量应用,作者用正交试验法,研究了不同种类黄壤土、不同矿渣及水分含量的粘土砂在缝纫机电机壳铸造生产中的适用性,并测试型砂强度、透气性等工艺性能.在此基础上,利用所得配方和工艺,在工厂进行了大批量生产,取得了明显的效果.     

α淀粉对机器造型黄壤土天然粘土砂性能的影响

为解决将黄壤土天然粘土型砂直接应用在机器造型上,有时出现成型困难、起模不完整、表面安定性差的问题。本文开展了附加物对黄壤土天然粘土砂机器造型性能影响的研究。结果表明,在黄壤土天然粘土砂中加入一定量的α淀粉,对黄壤土天然粘土砂的机器造型性能产生积极的影响。     

型砂成分对气流冲击紧实的影响

对型砂的成分，包括粘土的含量、粘土中蒙脱石含量的不同、煤粉及糊精的含量不同对气流冲击紧实过程的影响进行了研究，并用初实层冲击紧实的观点对试验结果进行分析。     

烧结陶瓷铸造砂混制粘土砂的性能及特点

对烧结陶瓷铸造砂和石英砂混制粘土砂时的表现行为进行了试验研究,发现由烧结陶瓷铸造砂和石英砂混制粘土砂的湿压强度随膨润土加入量的增加而提高。在膨润土加入量一定的情况下,型砂的湿压强度和透气性随型砂中水分含量的增加而提高,待达到最大值后,水分继续增加,型砂的湿压强度和透气性降低。在相同膨润土加入量的情况下,由70/140烧结陶瓷铸造砂混制无煤粉和含煤粉粘土砂及由50/100烧结陶瓷铸造砂混制无煤粉粘土砂的湿压强度低于相同条件下由石英砂混制相应粘土砂的湿压强度,由50/100烧结陶瓷铸造砂混制含煤粉粘土砂的湿压强度等于或略低于由石英砂在相同条件下混制含煤粉粘土砂的湿压强度。在相同工艺条件下,由烧结陶瓷铸造砂混制粘土砂的透气性高于由石英砂混制粘土砂的透气性。     

湿型砂透气性影响因素的分析探讨

通过试验对影响湿型砂透气性的砂处理工艺（包括混砂方式、松砂、筛砂工艺等）和分型面、砂层厚度、紧实度等工艺因素进行了定量分析，为生产实践中采取适当工艺措施提高铸型透气性，提供了理论依据。     

加载速度对压实紧砂过程的影响

分析了砂粒间隙中的空气对动压紧砂的影响、粘土膜塑性变形对动压紧砂的影响、加载速度对铸型应力－应变的影响、加载速度对铸型紧实度的影响、动力紧砂与静力紧砂所消耗的紧实功的比较和撞击能量对紧砂效果的影响等问题，指出在压实紧砂过程中，加载速度＜２ｍ／ｓ时和加载速度较大时有不同的应力－应变曲线和不同的紧实度－时间曲线。决定最终紧实效果的主要因素是撞击能量的大小。     

型砂成分与性能关系的数学模型

在紧实率恒定的情况下，利用逐步回归分析的方法，建立了湿型砂中膨润土含量、死土含量与型砂劈裂强度、水分、透气性之间关系的数学模型。据此计算出的膨润土含量的误差小于０．６５％，死土含量的误差小于１％，可以满足生产实际的需要。这种模型可用于砂处理系统中型砂性能的自动控制。     

粘土砂性能及其成分调整的工艺新探索

提出了粘土砂性能及其成分调整的新工艺，通过紧实率调整混砂时加水量；根据型砂的水分和强度分别调整新砂和膨润土的补加量，煤粉的补加量根据型砂的发气量以及铸件表面质量确定；明确了型砂性能与型砂成分补加量间的关系，为调整型砂的性能提供了理论依据和生产指导方法。     

铸元素在含大量覆膜砂芯砂的粘土砂中的应用

针对粘土砂系统因大量覆膜砂芯砂混入使型砂脆性增加,成形性降低,铸造工艺性能恶化的实际情况,用铸元素取代粘土砂系统中的膨润土和煤粉,在不加新砂的情况下,采用含大量覆膜砂芯砂的粘土旧砂混制型砂和加入新砂、膨润土和煤粉后混制的型砂相比,其湿压强度、透气性、紧实率相近,而热湿拉强度明显提高。采用铸元素消除了大量覆膜砂芯砂混入对粘土砂性能的不利影响,实现了在不添加新砂的情况下,稳定了含大量覆膜砂芯砂粘土型砂的性能。     

铸型失压紧实工艺及机理研究

笔者在实验中发现,若将填满型砂的砂箱内,充以0.2—0.5MPa的压缩空气,当压缩空气迅速定向排出,定向排出的气流对型砂具有良好的紧实作用,笔者称之为“失压紧实”。本文概略地介绍了失压紧实工艺过程,实验装置;本文研究了失压紧实的工艺参数对铸型紧实度的影响,及其实砂机理,并对“失压紧实”的前景作了初步的探讨。     

黏土旧砂完全再生技术

分析了旧砂中黏土膜的分离机制,采用不同的再生工艺评估了黏土旧砂再生技术的可行性,确定了700℃焙烧＋机械再生＋微粉分离的黏土旧砂完全再生工艺,研究了黏土完全再生砂的工艺适应性,并介绍了黏土砂完全再生系统的组成。结果表明,视不同的型砂工艺,黏土完全再生砂可分别用于混制水玻璃砂、覆膜砂、冷芯盒砂或热芯盒砂,但不能用于自硬呋喃树脂砂的制备。     

泥分、芯砂混入对粘土型砂质量的影响

在粘土砂铸造生产过程中，不可避免地总有部分粘土失去活性变为泥分，也会有部分芯砂混入旧砂之中，泥分及芯砂的混入，污染了粘土型砂，影响粘土型砂的铸造工艺性能。本文研究了泥分及芯砂的混入对型砂性能的影响，结果表明，粘土旧砂中，粘土含量以不超过8％为宜，树脂芯砂含量以不超过3．5％为宜，水玻璃砂芯含量以不超过4％为宜，否则需要对旧砂进行再生处理。     

静压造型生产线湿型砂质量控制探索

介绍了我厂静压造型生产线湿型砂系统的特点;通过对静压线湿型砂大量实验数据的统计与分析,对湿型砂系统进行了调控,使其达到最优性能。型砂配比,型砂湿混时间,系统旧砂存量,沸腾冷却床冷却水压,除尘系统风量等都是型砂调控的关键点。经过调整的型砂系统,紧实率∶水分稳定在10%～12%,湿压强度稳定在0.16 MPa～0.18 MPa,含泥量控制在11%～12%,有效黏土含量控制在7.5%~8.0%.膨润土及混配土加入量都有所减少,型砂性能不但得到整体提高,产品质量也得到极大改善,而且还节约了成本。     

粘土砂造型线型砂综合添加剂的应用

介绍了膨润土、煤粉、α淀粉、原砂等造型材料的技术要求,分析了紧实率、水分、湿态强度、透气性、型砂粒度等型砂性能对铸件质量的影响情况,提出一种型砂综合添加剂混配方案,并与原砂混配方案进行了生产性试验,结果表明能明显改善型砂性能、提高铸件质量及一次合格率,是改善粘土砂铸造环境和绿色发展的一个较好的措施。     

改善天然湿型砂混砂过程中结团现象的研究

通过加入YZ-1型润滑剂和改变加水顺序等措施,可以有效改善湿型砂混砂过程中的结团现象.当YZ-1型润滑剂加入量比较少时,可以在一定程度上提高湿型砂的抗压强度；当YZ-1型润滑剂含量继续增加时,湿型砂抗压强度又会逐渐降低直至无法造型.采用原砂先加水后加粘土的工艺比传统的原砂先加土后加水的工艺,型砂的强度更高、结团度更低.对加过YZ-1型润滑剂的湿型砂再重新混制反复多次,抗压强度提高,结团度基本不变.     

FS粉在铸铁湿型砂中的应用研究

生产应用表明:在湿型砂中FS粉可全部取代煤粉,且由于其用量仅为煤粉用量的1/4左右,而降低型砂中的细颗粒含量、减少水分、提高透气性、减少发气量、提高型砂湿压强度及热湿拉强度,使型砂具有较好的造型性能。可有效地减少型废及铸件气孔、砂眼等废品,有助于提高铸件的内外质量和改善作业环境。     

多品种铸件湿型砂生产控制工艺探讨

在湿型砂铸造过程中,型砂性能优劣直接影响到铸件的品质。针对由于型砂控制工艺比较单一,造成型砂性能波动大、铸件表面质量差、铸造缺陷增多等问题,通过试验摸索出分机型制定不同型砂物料加入量和旧砂除尘量,以稳定型砂中有效成分含量,使型砂性能波动减小,最终达到减少铸造缺陷的目的。     

Binder jetting 3D printing process optimization for rapid casting of green parts with high tensile strength

Binder jetting 3D printing is a rapid, cost effective, and efficient moulding/core making process, which can be applied to a large variety of materials. However, it exhibits a relatively low green-part strength. This may cause the collapse of the printed parts during de-caking and the pick-up procedure, especially in the case of small-scale structures, such as thin walls, tips, and channels. In this work, polyvinyl alcohol (PVA) was used as the additive in coated sand powder. By exploiting the binding effect between the two composites (thermoplastic phenolic resin and PVA) triggered by the binder, bonding necks firmly form among the sand particles, improving the green-part strength of the coated sand printed parts. Experiments based on the Taguchi method were used to investigate the relationship between the process parameters and the green-part tensile strength. The following set of optimal process parameters was identified:50wt.% alcoholicity of the binder, 75% binder saturation, 0.36 mm layer thickness and 4.5wt.% PVA content. Further, the effect of such parameters on the green-part tensile strength was determined via statistical analysis. The green part of an engine cylinder head sand pattern with complex cavity structures was printed, and the green-part tensile strength reached 2.31 MPa. Moreover, the ZL301 aluminum alloy impeller shape casting was prepared using sand molds printed with the optimal process parameters. The results confirm that the proposed binder jetting 3D printing process can guarantee the integrity of the printed green parts and of small-size structures during decaking and the pick-up procedure. Furthermore, the casting made from the printed sand molds exhibits a relatively high quality.     

Evaluation of green compressive strength of clay bonded moulding sand mix: neural network and neuro-fuzzy based approaches

Abstract

An attempt has been made to develop neural network and neuro-fuzzy based models to predict the green compressive strength of clay bonded moulding sand mixtures and to analyse the properties of the mixed sand. Data for the models were generated following standard experimental procedure in the sand laboratory. Process parameters such as clay content, moisture, coal dust and mulling time were varied. The collected data were used in developing these models. The predicted green compressive strengths by neural network and neuro-fuzzy based models have been found to be in good agreement with the experimental values. Furthermore, it has been observed from the results that the predicted values from the neuro-fuzzy model are more accurate than those predicted from the neural network model.     

Optimization of green sand mould system using Taguchi based grey relational analysis

The strength of the mould cavity in sand casting is very much significant to attain high-quality castings. Optimization of green sand process parameters plays a vital role in minimizing casting defects. In the present research work, the effect of process parameters such as AFS grain fineness number, water, molasses, bentonite, fly ash, and ramming, and their levels on the resultant mould properties were investigated and optimized using Taguchi based grey relational analysis. The Taguchi L18 orthogonal array and analysis of variance(ANOVA) were used. The quality characteristics viz., green compression strength, permeability, bulk density, mould hardness and shatter index of green sand mould were optimized using grey relational grade, based on the experiments designed using Taguchi's Design of Experiments. ANOVA analysis indicated that water content is the most influential parameter followed by bentonite, and degree of ramming that contributes to the quality characteristics. The results are confirmed by calculating confidence intervals, which lies within the interval limits. Finally, microstructure observations and X-ray diffraction analysis have been performed for the optimal sand parametric combination. Results show that presence of maximum amount of SiO_2, which might be the reason for enhancement of the physical properties of the sand.