检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

PMO对高速钢枝晶组织及碳化物的影响

钢铁 2024年第2期59卷 119-128,156页

作者：刘海宁陈杨珉陈湘茹李莉娟翟启杰上海大学先进凝固技术中心上海200444

脉冲磁致振荡(Pulse Magneto-oscillation,简称PMO)是上海大学先进凝固技术中心原创的凝固均质化技术,该技术成功已应用于多家冶金企业数十种特殊钢生产,在改善铸坯质量方面取得了理想效果。高速工具钢(简称高速钢)作为一种高合金钢,其... 详细信息

脉冲磁致振荡(Pulse Magneto-oscillation,简称PMO)是上海大学先进凝固技术中心原创的凝固均质化技术,该技术成功已应用于多家冶金企业数十种特殊钢生产,在改善铸坯质量方面取得了理想效果。高速工具钢(简称高速钢)作为一种高合金钢,其铸态组织中树枝晶组织及共晶碳化物发达,宏观偏析严重,不仅影响了其质量和性能,同时制约了该类钢种采用连铸工艺生产。为了探究PMO改善高速钢凝固组织的可行性,采用双电源真空感应熔炼装置,研究PMO对其枝晶组织、共晶碳化物的影响。研究结果表明,在PMO作用下,高速钢铸态组织中粗大的柱状晶组织转变为全等轴晶组织,并且共晶碳化物网交汇区及共晶碳化物颗粒平均尺寸大幅度减小,碳化物分布均匀性得到显著改善。PMO对4个钢种的共晶碳化物网交汇处尺寸有明显细化作用,以M2高速钢共晶碳化物网交汇处尺寸细化程度为例,1/8D、1/4D和1/2D(D为铸坯径向直径)处的碳化物交汇处的平均尺寸较未施加PMO处理的铸锭依次减小48.5%、47.1%和43.4%;同时,PMO可以进一步细化共晶碳化物颗粒尺寸,以M2Al高速钢为例,1/8D、1/4D和1/2D处的共晶碳化物颗粒平均尺寸依次减小49.1%、54.5%、40.2%。研究结果为提高高速钢铸态质量提供了一种新思路及新方法,并有助于高速钢实现连铸和避免高速钢大变形量压力加工过程中产生开裂现象,为改善高速钢连铸过程中遇到的心部碳化物聚集、粗大碳化物等问题提供了一种新的方向。

关键词： PMO 高速钢凝固铸态组织枝晶组织共晶碳化物

Cementite Decomposition in Spherical Graphite Iron by Electropulsing

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2009年第2期25卷 199-202页

作者： Qingchun Li Cuowei Chang qijie zhai Department of Materials and Chemical Engineering Liaoning University of Technology Jinzhou 121001 China Department of Materials Science and Engineering Shanghai University Shanghai 200072 China

The influence of electropulsing on cementite decomposition in the spherical graphite iron has been studied. The results indicated that the cementite was decomposed in a short time by high current density electropulsing. With increasing electropulsing time, the in situ nucleation of graphite in cementite was accompanied with the quick decomposition of cementite. The dislocation accumulation adjacent to the cementite and the quick diffusion of carbon atom by electropulsing were main reasons for the quick decomposition of cementite. The in situ nucleation of graphite in the cementite resulted from the dislocation climbing crossing the cementite lamellae.

关键词： Pulse electric current Spherical graphite iron Cementite Decomposition

Review of grain ref inement methods for as-cast microstructure of magnesium alloy

在线全文

学校读者我要写书评

暂无评论

China Foundry 2009年第2期6卷 93-103页

作者： Song Changjiang Han Qingyou zhai qijie Shanghai Key Laboratory of Modern Metallurgy ＆ Materials Processing Shanghai University Shanghai 200072 China Mechanical Engineering Technology Department Purdue University West Lafayette IN 47907 USA

As the lightest structural metal,Mg and Mg-based alloys have great potential applications in the aerospace,automotive and nuclear ***,such applications have been limited by low ductility and ***,small grain sized structure can synchronously improve its ductility and ***,universally reliable grain ref inement techniques for the magnesium alloys are still under investigation and some are in strong *** paper presents a brief review of development of grain ref inement methods for magnesium alloys,which would contribute to a better understanding of the factors controlling grain ref inement and provide an outlook of future research in this fi eld.

关键词： magnesium alloy grain refinement microstructure

Study on undercooling of metal droplet in rapid solidification

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2005年第6期48卷 632-637页

作者： GAO Yulai GUAN Wanbing zhai qijie XU Kuangdi School of Materials Science and Engineering Shanghai University Shanghai 200072 China School of Materials Science and Engineering Shanghai University Shanghai 200072 China School of Materials Science and Engineering Shanghai University Shanghai 200072 China School of Materials Science and Engineering Shanghai University Shanghai 200072 China

A mathematical model for the undercooling of the metal droplet during the rapid solidification is established, by which the factors that influence the undercooling of the metal droplet during the rapid solidification are analyzed, and the parameter $\zeta = \sigma _{SL} ^3 /\left( {T_L \Delta H^2 } \right)$ is defined as the impact factor of the undercooling for the droplet solidification. Different undercoolings of droplets induced by various rapid solidification conditions are mainly ascribed to the change of the impact factor. Moreover, it is shown that the larger of ζ, the higher the relative undercooling can be gained. Meanwhile, the parameters such as solid-liquid interfacial energy σ SL and latent heat of solidification ΔH also vary with the rapid solidification conditions of droplets.

关键词： droplet, rapid solidification, relative undercooling, impact factor.

在线全文

学校读者我要写书评

暂无评论

电磁辅助优化高速钢组织与性能研究进展

中国冶金 2024年第8期34卷 1-10,19页

作者：叶承欢张世民朱守豪陈湘茹翟启杰上海大学先进凝固技术中心上海200444

制造业的迅猛发展对高速钢品质提出了更高的要求,对高品质高速钢的需求也逐步提升。高速钢的力学性能主要取决于其微观组织,尤其是其中碳化物的形貌、尺寸、数量、分布。随着物理和材料科学与技术的进步,电磁场在材料制备中的应用受到... 详细信息

制造业的迅猛发展对高速钢品质提出了更高的要求,对高品质高速钢的需求也逐步提升。高速钢的力学性能主要取决于其微观组织,尤其是其中碳化物的形貌、尺寸、数量、分布。随着物理和材料科学与技术的进步,电磁场在材料制备中的应用受到了冶金与材料工作者的关注,并成为近年来研究的热点。总结了国内外通过外加电磁场改善高速钢微观组织和性能的研究成果,包括利用电磁场调控高速钢凝固组织、优化高速钢热处理微观组织和高速钢刀具服役性能,并展望了这一领域未来研究重点和应用前景。

关键词：高速钢凝固热处理碳化物电磁场

Fast calorimetric scanning of micro-sized SnAgCu single droplet at a high cooling rate

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2009年第6期52卷 1707-1711页

作者： GAO YuLai ZOU ChangDong YANG Bin zhai qijie School of Materials Science and Engineering Shanghai UniversityShanghai 200072China

The undercooling of the single micro-sized droplet of Sn-3.0Ag-0.5Cu(wt%)alloy has been studied via the newly developed fast calorimetric scanning technique,by which the fast heating and cooling treatment for a single droplet can be realized,with the maximum heating or cooling rate being 1×104K/*** to the nearly spherical shape of the single droplet upon heating and cooling and the resul-tant geometric stability,the influence of the droplet size on the solidification process could be *** a result,the puzzled issue on how to separate the mutual effects of droplet size and cooling rate in the field of rapid solidification has been primarily solved,making it possible to study separately the effect of droplet size and cooling ***,the in-situ observation on deep undercooling could be actualized in this condition,differing from that obtained only by theoretical *** results showed that the undercooling was increased with the increasing cooling rate,and the maximum in-situ measured undercooling reached *** undercooling of the single droplet,however,was increased abruptly when cooled at the rate of 2×103K/*** undercooling increased slightly as the cooling rate was increased continuously to 1×104K/s,implying the infeasibility for gaining large undercooling only by increasing the cooling rate.

关键词： fast scanning calorimetry single droplet large cooling rate undercooling

冷却速率对ZG40CrNi2Mo大型铸件凝固组织及元素偏析的影响

在线全文

学校读者我要写书评

暂无评论

热加工工艺 2024年第15期53卷 135-140页

作者：邹富康仲红刚李莉娟龚永勇陈湘茹翟启杰上海大学先进凝固技术中心上海200444

为了研究铸件凝固过程中不同冷却速率对其凝固组织与元素偏析的影响,利用铸件凝固过程数值模拟方法和自研的高通量凝固过程热模拟实验装置,开展了ZG40CrNi2Mo优质调质钢在不同冷却速率下的凝固模拟实验。结果表明:ZG40CrNi2Mo调质钢的... 详细信息

为了研究铸件凝固过程中不同冷却速率对其凝固组织与元素偏析的影响,利用铸件凝固过程数值模拟方法和自研的高通量凝固过程热模拟实验装置,开展了ZG40CrNi2Mo优质调质钢在不同冷却速率下的凝固模拟实验。结果表明:ZG40CrNi2Mo调质钢的二次枝晶臂间距λ_(2)与局部凝固时间t的关系符合λ_(2)=36.03 t0.26;随着冷却速率的降低,Cr元素偏析呈现上升趋势,Ni元素偏析先上升后降低;Mo元素偏析最为严重,但是对于冷却速率的变化不敏感。

关键词：热模拟数值模拟冷却速率凝固组织二次枝晶臂间距元素偏析

Undercooling evolution of pure Sn droplets in various atmospheres based on fast scanning calorimetry

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2014年第20期59卷 2455-2459页

作者： Bingge Zhao Linfang Li qijie zhai Yulai Gao Laboratory for Microstructures Shanghai University School of Materials Science and Engineering Shanghai University

Undercooling of Sn droplets in different atmospheres was studied by fast scanning calorimetry(FSC)at cooling rate of 1,000 K/*** is found that the undercooling decreased with increasing partial pressure of *** distributed SnO2islands were observed to form on the droplet surface,which likely has promoted the heterogeneous surface *** the partial pressure of oxygen changes,the nucleation rate and growth of SnO2led to different oxide islands,which resulted in various potential catalytic sites for the nucleation of the molten Sn *** results showed that the nucleation process of the Sn droplets was sensitive to the solidification environment,and therefore the atmosphere should be taken into account in the study of the nucleation behavior of the single Sn droplets.

关键词：扫描量热法环境敏感过冷度纯锡快速扫描演化 SnO2 成核速率

Effect of cooling rate on solidification structure and linear contraction of a duplex stainless steel

在线全文

学校读者我要写书评

暂无评论

China Foundry 2012年第3期9卷 239-243页

作者： Zhong Honggang Chen Xiangru Ao Lu zhai qijie Shanghai Key Laboratory of Modern Metallurgy&Materials Processing Shanghai UniversityShanghai 200072China

Cooling rate is a key factor that can drastically affect the phase transformation and thermal stress of duplex stainless steels. Therefore, in this research, different sand moulds were used to explore the influence of cooling rate on the solidification of the 2304 duplex stainless steel (DSS). The macro and micro structures of the 2304 DSS were investigated. Small equiaxed grains are obtained in chromite sand mould sample with a lower pouring temperature and a higher cooling rate, whereas coarse columnar and equiaxed grains are found in silica sand and refractory powder mould samples. The size of austenite phase is significantly increased with decreasing cooling rate, while the ferrite phase content ranging from 51.6% to 53.9% does not change obviously. In addition, the linear contraction of the 2304 DSS decreases from 2.34% to 1.09% when the mean cooling rate above 1,173 K increases from 0.99 K·s-1 to 3.66 K·s-1.

关键词： duplex stainless steel solidification structure linear contraction cooling rate