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Effect of V and Sn on microstructure and mechanical properties of gray cast iron

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China Foundry 2022年第5期19卷 427-434页

作者： Yi-li Li Rui-run Chen Qi Wang Wen-chao Cao Xin-xiu Wang Yuan Xia Guo-ping Zhou Ying-dong Qu Guang-long Li School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Yangzhou Wutingqiao Cylinder Liner Co. Ltd.Yangzhou 225000JiangsuChina School of Materials Science and Engineering Shenyang University of TechnologyShenyang 110870China

The cylinder liner is one of the important parts of a diesel engine.gray cast iron is the main material for manufacturing cylinder liners due to its good casting performance,convenient processing performance,good wear resistance and low cost.In the present work,the effects of vanadium(V)and tin(Sn)on the microstructure and properties of gray cast iron were studied.Results show that increasing the contents of V and Sn can not only refine the graphite,but also reduce the pearlite lamellar space.The graphite size and lamellar spacing of pearlite are firstly reduced and then increased.Pearlite quantity reaches over 98%after adding V and Sn.Adding V and Sn can promote the precipitation and solid solution strengthening of gray cast iron,so as to improve the mechanical properties.The Brinell hardness reaches the peak of 424 HB at the contents of 0.21wt.%V and 0.06wt.%Sn,and the sample containing 0.11wt.%V and 0.08wt.%Sn shows the highest compressive strength and tensile strength of 1,699 MPa and 515 MPa,respectively.The main strengthening mechanism comes from the solid solution strengthening and fine grain strengthening of V and Sn.

关键词： V Sn gray cast iron cylinder liner microstructure mechanical properties

Different thermal fatigue behaviors between gray cast iron and vermicular graphite cast iron

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China Foundry 2022年第3期19卷 245-252页

作者： Gui-quan Wang Zhong-li Liu Yan-xiang Li Xiang Chen School of Nuclear Equipment and Nuclear Engineering Yantai UniversityYantai 264005ShandongChina School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationTsinghua UniversityBeijing 100084China

The initiation and propagation of thermal fatigue cracks in gray cast iron and vemicular graphite cast iron were investigated by Uddeholm method to reveal the complex thermal fatigue behaviors of cast iron.Differences of thermal fatigue behaviors of gray cast iron and vemicular graphite cast iron were observed and analyzed.It is found that the observed differences are related to the combination of graphite morphology and the oxidization of matrix.More oxidized matrix is observed in gray cast iron due to its large specific surface area.The brittle oxidized matrix facilitates the propagation of microcracks along the oxidization layer.By contrast,the radial microcracks are formed in vermicular graphite at the edge of graphite due to fewer oxidization layers.It indicates that the thermal fatigue resistance of gray cast iron is dominated by graphite content and morphology while that of vermicular graphite cast iron strongly relates to the strength of the matrix.

关键词： thermal fatigue gray cast iron vermicular graphite cast iron oxidization cracking propagation

gray cast iron With Directional Graphite Flakes Produced by Cylinder Covered Compression Process

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Journal of iron and Steel Research(International) 2007年第5期14卷 52-55页

作者： ZHAO Xin WANG Jin-feng JING Tian-fu The Sixth Department Zhengzhou Institute of Aeronautics Zhengzhou 450015 Henan China State Key Lab of Metastable Materials Science and Technology Yanshan University Qinhuangdao 066004 Hebei China

A new plastic deformation process for gray cast iron named cylinder covered compression （CCC） was developed. By CCC process, gray cast iron （GCI） specimens, which are embedded in steel cylinders, were hot compressed up to 80% reduction in height without the cracking problem. It was clearly observed that the uniform distribution of directional graphite flakes appeared after more than 45 % reduction hot compression. The strength, ductility, and microhardness of GCI after 80% reduction deformation were significantly enhanced： the tensile strength varied from 117 MPa to 249 MPa, while the total elongation varied from 0 to 5.2%, and the microhardness varied from 153 HV to 217 HV. It was shown that the tensile fracture surface presented ductility characters after more than 45% reduction hot deformation.

关键词： gray cast iron hot working tensile strength elongation hardness

Influence of varying forms of bionic units on repairing remaining quenching surface of gray cast iron

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Journal of iron and Steel Research(International) 2021年第2期28卷 201-210页

作者： Hui Li Li Feng Hong Zhou Peng Zhang Ti Zhou Qi Sui Lu-quan Ren Key Laboratory of Automobile Materials(Jilin University) Ministry of EducationChangchun 130025JilinChina School of Material Science and Engineering Jilin UniversityChangchun 130025JilinChina School of Mechanical and Aerospace Engineering Jilin UniversityChangchun 130025JilinChina Key Laboratory of Terrain Machinery Bionics Engineering(Jilin University) Ministry of EducationChangchun 130025JilinChina

In order to repair and reuse remaining quenching surface(RQS)divided into severely worn surface(SWun-S)and mildly worn surface(MWun-S)of abandoned gray cast iron guide rail,inspired by the bionic theory,varying forms of bionic units such as spot(Sp-S),striation(St-S),and reticulation(Re-S)were fabricated on RQS of gray cast iron through laser processing technology.Firstly,the microstructure,phase composition,and microhardness of bionic units and RQS were analyzed by optical microscopy as well as X-ray diffraction instrument and scanning electron microscopy,respectively.Secondly,the oil lubrication wear experiment was performed on homemade line reciprocating wear machine.The results demonstrated that the bionic units had a significant effect on improving wear resistance of RQS of abandoned guide rail due to the microstructure and higher hardness.In addition,the weight loss ratios of MWun-S,Sp-S,St-S,and Re-S samples were decreased by 36.72%,36.78%,62.26%,and 80.39%,respectively,compared with that of SWun-S sample.The mechanism of wear resistance enhancement was also discussed.

关键词： Repairing Laser bionic unit Remaining quenching surface gray cast iron

Effect of inoculating addition on machinability of gray cast iron

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Journal of Rare Earths 2009年第2期27卷 294-299页

作者：任凤章李锋军刘伟明马战红田保红 School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang 471003China Henan Key Laboratory of Advanced Non-ferrous Metals Luoyang 471003China Yituo Foundry Corporation China Yituo Group Corporation LimitedLuoyang 471004China

gray cast irons were inoculated with FeSi75＋RE and FeSi75＋Sr inoculants. The changes of apex angle of the drills before and after being used were used to evaluate machinability of gray cast irons. Effect of FeSi75＋RE and FeSi75＋Sr inoculants on mechanical properties, machinability and sensibility of gray cast iron used in cylinder block were investigated. Experimental results showed that gray cast iron treated with 60%FeSi75＋40% RE inoculants exhibited tensile strength consistently at about 295 MPa along with good hardness and improved metallurgical quality. While gray cast iron inoculated with 20%FeSi75＋80% Sr inoculants exhibited the best machinability, the lowest cross-section sensibility and the least microhardness difference. The tool flank wear of the drill increased correspondingly with the increase of the microhardness difference of the matrix, indicating the great effect of homogeneity of the matrix on the machinability of gray cast iron.

关键词： gray cast iron compound inoculants machinability rnicrohardness difference cross-section sensibility homogeneity rare earths

Microstructure and high-temperature wear properties of in situ TiC composite coatings by plasma transferred arc surface alloying on gray cast iron

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International Journal of Minerals,Metallurgy and Materials 2015年第12期22卷 1273-1282页

作者： Hang Zhao Jian-jun Li Zhi-zhen Zheng Ai-hua Wang Qi-wen Huang Da-wen Zeng State Key Laboratory of Material Processing and Die & Mould Technology Huazhong University of Science & Technology

In this work, an in situ synthesized TiC-reinforced metal matrix composite （MMC） coating of approximately 350-400μm thickness was fabricated on a gray cast iron （GCI） substrate by plasma transferred arc （PTA） surface alloying of Ti-Fe alloy powder. Microhard- ness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy （SEM） and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual anstenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures （473 K and 623 K）, and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the sam- ples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstruc- ture and to the presence of TiC particles.

关键词： gray cast iron composite coatings particle-reinforced composites titanium carbide surface alloying microstructure wear

EFFECT OF NITROGEN ON GRAPHITE MORPHOLOGY IN gray cast iron

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Acta Metallurgica Sinica(English Letters) 1993年第8期6卷 151-155页

作者： ZHAI Qijie HU Hanqi University of Science and Technology Beijing,Beijing,China Faculty of Foundry,University of Science and Technology Beijing,Beijing 100083,China Beijing Univ of Science and Technology Beijing China

The distribution of N and morphology of graphite in gray cast iron containing N were studicd by adopting the man-made specimens of Fe-C-Si-Mn alloys with some N added. The N adsorbed along the interfaces between graphite and matrix together with solid- solutioned in graphite is believed to be the principal cause of morpholongical variation of graphite.

关键词： gray cast iron graphite morphology N

Effects of RE and N on Properties of Corrosion Resistance and Oxidation Resistance of gray cast iron

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Journal of Rare Earths 1998年第3期16卷 30-33页

作者：曾奇翟启杰 Foundry Institute University of Science and Technology Beijing Beijing 100083 China

By means of ladle inoculating, the effects of RE and N on the properties of corrosion resistance and oxidation resistance of gray cast iron were studied. The results show that the properties of both corrosion resistance and oxidation resistance are improved by adding suitable amount of RE, while RE and N are added as a multi inoculant, the oxidation resistance of gray cast iron is remarkably increased.

关键词： Rare earths Nitrogen gray cast iron Corrosion resistance Oxidation resistance

Calculating the effective thermal conductivity of gray cast iron by using an interconnected graphite model

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China Foundry 2020年第3期17卷 183-189页

作者： Guang-hua Wang Yan-xiang Li School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationBeijing 100084China

A new theoretical model of gray cast iron taking into account a locally interconnected structure of flake graphite was designed,and the corresponding effective thermal conductivity was calculated using the thermal resistance network method.The calculated results are obviously higher than that of the effective medium approximation assuming that graphite is distributed in isolation.It is suggested that the interconnected structure significantly enhances the overall thermal conductivity.Moreover,it is shown that high anisotropy of graphite thermal conductivity,high volume fraction of graphite,and small aspect ratio of flake graphite will cause the connectivity effects of graphite to more obviously improve the overall thermal conductivity.Higher graphite volume fraction,lower aspect ratio and higher matrix thermal conductivity are beneficial to obtain a high thermal conductivity gray cast iron.This work can provide guidance and reference for the development of high thermal conductivity gray cast iron and the design of high thermal conductivity composites with similar locally interconnected structures.

关键词： gray cast iron effective thermal conductivity flake graphite interconnected graphite structure