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Jiang Y.,Kunming University of Science and Technology | Cen Q.-H.,Kunming University of Science and Technology | Jiang Y.-H.,Kunming University of Science and Technology | Zhou R.,Kunming University of Science and Technology | Zhou R.,Research Center for Advanced Materials Processing of Yunnan Province
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2013

In order to study the effect of cooling rate on microstructure of high boron high speed steel roll ring produced by centrifugal casting, roll rings were produced through air cooling and water cooling using different moulds. The results show that the as-cast microstructure of high boron high speed steel roll ring consists of dendritic matrix and borocarbides. In rapid cooling condition, the microstructure is composed of martensite matrix and borocarbides of M2(B, C), M3 (B, C) and M23 (B, C)6. As increasing the cooling rate, the grain size of matrix is decreased, the number of carboborides is reduced, the carboborides are changed from fishbone form to cribriform shape, and local necking and grain refinement is observed. Increasing cooling rate changes the distribution of alloy elements in matrix and hard phase. Microhardness of matrix increases slightly and microhardness of the hard phase remains un-changed as inoreasing the cooling rate. When roll ring is produced through air cooling for sand mould, chrysanthemum-shaped peritectic structure appears and its amount increases with increasing distance from outside edge of the roll ring. Source


Deng P.,Kunming University of Science and Technology | Deng P.,Research Center for Advanced Materials Processing of Yunnan Province | Li Z.,Kunming University of Science and Technology | Li Z.,Research Center for Advanced Materials Processing of Yunnan Province | And 3 more authors.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2013

The solidification process and characteristic of solidification microstructure of Fe-C-B alloy were analysed. Combining the research results of phase diagram, the types and formation mechanism of hard phases in the alloy were discussed, and the effect of composition on the microstructure and properties of Fe-C-B alloy was introduced primarily. A direction to promote the research and application of Fe-C-B alloy was pointed out, which that based on further improving phase diagram of Fe-C-B ternary system, to launch in-depth study on the effect of solidification condition and composition on the microstructure and properties of Fe-C-B alloy without chromium addition, and explore the way to further improve on the microstructure and properties of Fe-C-B alloy. Source


Deng P.-K.,Kunming University of Science and Technology | Deng P.-K.,Research Center for Advanced Materials Processing of Yunnan Province | Li Z.-H.,Kunming University of Science and Technology | Li Z.-H.,Research Center for Advanced Materials Processing of Yunnan Province | And 3 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2013

In order to investigate the effect of chromium content(Cr≤3.80%) on microstructure and properties of Fe-C-B hypoeutectic alloys, the microstructure of the alloys was observed by optical microscopy(OM), quantitative metallography analysis and X-ray diffraction(XRD), their hardness and impact toughness were analyzed and tested. The results show that chromium can accelerate precipitation of primary austenite and pearlitic transformation of the alloy, decrease volume of eutectic ledeburite and eutectic hard-phase, and improve the distribution of hard-phases. The impact toughness of as-cast and heat-treated alloys improves with increasing of chromium content. However, the hardness of the alloys firstly increases and then decreases with the increasing chromium, and it reaches the maximum when Cr content is 3.23% in present experiment. The impact toughness of the sample containing 3.80% Cr increases by about 50% compared with that of the sample without chromium. Source


Li R.-L.,Kunming University of Science and Technology | Li R.-L.,Research Center for Advanced Materials Processing of Yunnan Province | Cen Q.-H.,Kunming University of Science and Technology | Cen Q.-H.,Research Center for Advanced Materials Processing of Yunnan Province | And 4 more authors.
Mocaxue Xuebao/Tribology | Year: 2013

To investigate the relationships between quenching cooling ways and microstructure transformation of the high boron medium carbon alloy (HBMCA), the samples were prepared by quenching HBMCA at 1000°C in three media, i.e., air, oil and water, followed by tempering at 500°C. The microstructure transformation of the samples was analyzed by using X-ray diffraction. The hardness and high temperature tribological performance were investigated. The results show that the matrix of air cooled sample consisted of tempered sorbite, small amount of pearlite and M3(B, C) precipitates. The oil cooled and water cooled samples were composed of tempered sorbite as the matrix and MB and M2B type hard phases. As the cooling rate increased, volume fraction of the hard phase slightly decreased while the hardness and wear resistance increased. The main wear mechanism of air cooled sample was oxidation wear. Oxidation spalling was alleviated for oil cooled sample. For water cooled sample, the wear mechanism was mainly caused by the combined action of furrow deformation and oxidation-removal. Source


Jiang Y.,Kunming University of Science and Technology | Jiang Y.,Research Center for Advanced Materials Processing of Yunnan Province | Jiang Y.-H.,Kunming University of Science and Technology | Jiang Y.-H.,Research Center for Advanced Materials Processing of Yunnan Province | And 5 more authors.
Zhuzao/Foundry | Year: 2013

Aiming at the high production costs of high speed steel roll, a new kind of wear-resistant material was designed through adding the cheap boron elements to partly replace expensive element, and roll ring was produced by centrifugal casting. The microstructure of high boron high speed steel roll ring was researched by means of scanning electron microscopy and X-ray diffraction, etc, which laid a foundation for high boron high speed steel composite rolls. The results show that as-cast high boron high speed steel roll ring comprises martensite, a small amount of residual austenite and borocarbides. Borocarbides consisting of M2 (B, C), (W, Mo)2 (B, C), M3 (B, C) and M23 (B, C)6 are distributed in fishbone, screen and bulk along the grain boundaries. Under rapid cooling, there is almost no segregation of alloying elements. After water quenching at 1050°C, the morphology and distribution of eutectic borocarbides do not change. Some secondary borocarbides dissolve, and broken borocarbides are found. The tiny and diffuse second precipitation appears in the matrix; the amount of second precipitation increases significantly after tempered at 525°C. After heat treatment, hardness achieves HRC 60.8, and impact toughness can achieve 8.4 J/cm2. Source

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