Research Center for Advanced Materials Processing of Yunnan Province

Kunming, China

Research Center for Advanced Materials Processing of Yunnan Province

Kunming, China
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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.


Li Q.,Kunming University of Science and Technology | Li Q.,Research Center for Advanced Materials Processing of Yunnan Province | Cen Q.,Kunming University of Science and Technology | Cen Q.,Research Center for Advanced Materials Processing of Yunnan Province | And 4 more authors.
Tezhong Zhuzao Ji Youse Hejin/Special Casting and Nonferrous Alloys | Year: 2012

Effect of electric pulse on the solidification structure of high-boron middle-carbon alloy steel was investigated by exerting electric pulse on the alloy steel during solidification process. The results indicate that, after electric current pulse treatment, grains of high-boron middle-carbon alloy steel are refined and spheroidized with more uniform distribution. Martensite lamellar spacing is decreased, and volume fraction of hard phase is decreased from 10.6% in non-electric pulse treatment to 8.3%, however, alloying elements, such as W, Cr, Mo, V in matrix are increased. In addition, hardness of matrix is improved from HV664 to HV739. Net-like hard phase exhibits discontinuous and isolated spheroidization. The co-action of Joule heat, magnetic-electric force and electric migration of electric pulse is responsible for the above effects.


Huang R.-Q.,Kunming University of Science and Technology | Huang R.-Q.,Research Center for Advanced Materials Processing of Yunnan Province | Sui Y.-D.,Kunming University of Science and Technology | Sui Y.-D.,Research Center for Advanced Materials Processing of Yunnan Province | And 6 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2013

Thermal fatigue performance of WC+Ni6025WC/steel matrix surface composites obtained by the V-EPC infiltrating process and mechanism of thermal fatigue crack initiation and propagation in the composites were studied by thermal shock test. The results show that the composites with the addition of 15vol% Ni6025WC powder exhibits a good thermal fatigue performance, and only some uncontinues fine cracks are observed in the composites after thermal shock test for 60 cycles. The factors including quality, thermal conductivity and distribution of the ceramic carbide particle, thermal stress and alternating at the interface between WC particles and matrix produced during thermal shock test influence the initiation and propagation of thermal stress fatigue crack in the surface composites. The thermal fatigue performance of the composites can be improved by proper design of composition and microstructure.


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.


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.


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.


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.


Bao Y.-L.,Kunming University of Science and Technology | Bao Y.-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 8 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2012

A novel high-boron high speed steel was developed by addition of boron to replace the expensive alloying elements in commerical high speed steel material. The effect of quenching temperature on microstructure of high-boron high speed steel containing 0.3-0.5%C and 0.5-2.5%B was studied. The results show that the as-cast microstructure of the high-boron high speed steel consists of ferrite(F), pearlite(P) and a small amount of martensite(M) and borocarbides of M 23(B, C) 6, (W, Mo) 2(B, C), M 3(B 1.5, C 0.5) and M(B 0.7, C 0.3), distributing in network and herringbone along grain boundaries. After quenching, the matrix microstructure changes to lath martensite containing 4% residual austenite. There is no change in the type of borocarbide, but its quantity decreases. Quenching from temperature of 950-1100°C, the network pattern is broken because of partial dissolution of borocarbides. As the quenching temperature increases, phenomenon of the network breaking become more and more obvious, which reduces the dissevering to the matrix of high-boron high speed steel.


Li Q.-Y.,Kunming University of Science and Technology | Li Q.-Y.,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 6 more authors.
Journal of Iron and Steel Research | Year: 2013

The effect of electric pulse with different pulse width on the solidification structure of high-boron middlecarbon alloy steel was investigated. The experimental results indicate that after electric pulse, the martensite lamellar spacing become smaller. With increase of alloying elements such as W, Cr, Mo and V contenting in matrix, hardness of matrix can be improved. Hard phase volume fraction is reduced, slice layer hard phase disappears, mesh hard phase is broken network and hard phase distribution became even. Along with the increase of pulse width, broken network first become apparent, and then decreases. In the experimental conditions, pulse width for 30μs, the phenomenon of broken network is the most obvious and hard phase distribution the most evenly.

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