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Influence of shrinkage porosity on fatigue performance of iron castings and life estimation method

China Foundry 2016年第1期13卷 47-53页

作者： Wei Liu Wei-hao Zhai Jun-feng Zhao School of Mechanics Civil Eng.&ArchitectureNorthwestern Polytechnical UniversityXi'an 710129China China Helicopter Research and Development Institute Jingdezhen 333000China

shrinkage porosity exists more or less in heavy castings, and it plays an important role in the fatigue behavior of cast materials. In this study, fatigue tests were carried out on the QT400-18 cast iron specimens containing random degrees of shrinkage porosity defect. Experimental results showed that the order of magnitude of life scattered from 103 to 106 cycles when the shrinkage percentage ranged from 0.67% to 5.91%. SEM analyses were carried out on the shrinkage porosity region. The inter-granular discontinuous, micro cracks and inclusions interfered with the fatigue sliding or hindering process. The slip in shrinkage porosity region was not as orderly as the ordinary continuous medium. The shrinkage porosity area on fracture surface(SPAFS) and alternating stress intensity factor(ASIF) were applied to evaluate the tendency of residual life distribution; their relationship was fitted by negative exponent functions. Based on the intermediate variable of ASIF, a fatigue life prediction model of nodular cast iron containing shrinkage porosity defects was established. The modeling prediction was in agreement with the experimental results.

关键词： shrinkage porosity iron castings fatigue life alternating stress intensity factor equivalent initial crack

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Effects of shrinkage porosity on Mechanical Properties of a Sand Cast Mg-Y-RE （WE54） Alloy

Effects of Shrinkage Porosity on Mechanical Properties of a ...

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中国材料大会2012

作者： Jilin Li Yuequn Ma Rongshi Chen Wei Ke State Key Laboratory for Corrosion and Protection Institute of Metal Research Chinese Academy of Sciences

ISBN: (纸本)9783037856086;3037856084

The distribution of shrinkage porosities in sand cast Mg-Y-RE （WE54） alloy castings was characterized through density measurement and calculated by Archimedes’s principle. The effect of porosity on mechanical properties of sand cast WE54 alloy was investigated through tensile tests and microstructure observation. It was found that the shrinkage porosities distributed mainly in the middle of the plate where the liquid feeding was quite inconvenient. And the porosities were formed along grain boundaries when secondary phases formed at the end of solidification. Hardness tests showed that the vikers hardness declined linearly with increasing porosity volume fraction. While the tensile strength and nominal yield strength declined exponentially as the porosity volume fraction increased. Microstructure observation showed that the fracture cracks propagated along the grain boundaries where porosities and secondary phases gathering together in as-cast WE54 alloy. The tiny porosities distributed in the secondary phases were observed, which could reduce the tensile strength of cast specimens significantly. The heat treatment strengthening effects were significantly weakened by porosities, and even no heat treatment strengthening effect was detected when the porosity volume fraction was higher than 1%. The microstructure observation also proved that no heat treatment strengthening effect existed in samples containing porosities.

关键词： shrinkage porosity Mechanical property We54 alloy Sand cast

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Optimization of investment casting process for K477 superalloy aero-engine turbine nozzle by simulation and experiment

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China Foundry 2022年第4期19卷 351-358页

作者： Xin Hao Guo-huai Liu Ye Wang Shi-ping Wu Zhao-dong Wang AECC South Industry Company Limited Zhuzhou 412002HunanChina State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China School of Materials Science and Chemical Engineering Harbin University of Science and TechnologyHarbin 150001China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

In order to reduce the shrinkage porosity of nickel-based superalloy castings in the investment casting process,the effects of different gating systems on mold filling,solidification process,and prediction of shrinkage porosity of aero-engine turbine nozzle castings were investigated by simulation and experimental *** show that the design of the vertical runner would cause greater turbulence of the melt in the riser during the mold filling process,and the outer runner is not *** the decrease in number of runners,the hot spot moves down towards the casting,and the shrinkage and porosity defects are formed in the casting below the *** the original designs,a certain tendency of shrinkage and porosity defect is found in the vanes,inner rings,and outer rings of the castings by both simulation prediction and ***,based on the processing optimization,the aero-engine turbine nozzle casting with no shrinkage and porosity defects is obtained.

关键词： nickel-based superalloy investment casting shrinkage porosity simulation optimization

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Effect of Mold Hardness on Microstructure and Contraction porosity in Ductile Cast Iron

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Journal of Iron and Steel Research(International) 2011年第4期18卷 44-47,67页

作者： Jafar Khalil-Allafi Behnam Amin-Ahmadi Faculty of Materials Engineering Sahand University of Technology Department ofMaterials Science and Engineering Sharif University of Technology

The effect of mold hardness on the microstructure of ductile iron and the contraction porosity was *** with different hardnesses（0.41,0.48,0.55,0.62 MPa）and a sand mold prepared by Co2 method were *** influence of silicon content on the induced expansion pressure owing to the formation of graphite was also *** contraction during solidification can be compensated by an induced expansion owing to the graphite relief when the hardness of mold increases;therefore,the possibility of achieving a sound product without using any riser increases.

关键词： ductile iron graphite preheating temperature carbide shrinkage porosity

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Defect elimination in green sand casting using simulation techniques:A case study

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International Journal of Modeling, Simulation, and Scientific Computing 2020年第5期11卷 1-19页

作者： Sarabjit Singh Neeraj Sharma Rajesh Khanna Department of Mechanical Engineering DAV University Jalandhar 144012PunjabIndia Department of Mechanical Engineering Maharishi Markandeshwar(Deemed to be University)Mullana 133207 AmbalaIndia International Tractors Ltd. HoshiarpurPunjabIndia

The Reynolds number of molten metal flowing mold cavity causes bulk turbulence and is the main cause of defects like shrinkage porosity and sand *** housings with shrinkage porosity at critical bearing bores and surface made the casting *** old gating casting areas of perimeters 290mm and 264mm of transmission housing,Reynolds numbers were observed as 16307 and 13806,respectively using simulation *** were collected from experiments to change casting area perimeters from 785mm and 785mm along with the addition of overlap *** Reynolds numbers at two locations were observed as 3705 and 3393,*** metal pressure,velocity and temperature results were related for final shrinkage results of the components on full *** purpose of the study is to reduce shrinkage and porosity defects in green sand casting part using MAGMAS simulation *** outcome was the reduction of casting machining rejection in transmission housing casting from 5.8%0.7%with savings of approximately 0.13 million USD over the period of 14 *** of this work include casting defects study and reduction in different grades and weight range.

关键词： Green sand casting gating system Reynolds number grey cast iron shrinkage porosity MAGMAS software

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