球磨机ZGMn13衬板的失效分析

采用化学成分分析、金相检验等方法,对高锰钢衬板在使用中的碎裂进行分析.分析表明,衬板中存在严重的疏松,晶界上有大量未溶块状碳化物并析出针状碳化物以及球状氧化物;热处理工艺不当、铸造疏松以及非金属夹杂物的超标是导致球磨机衬板早期失效的主要原因,并提出了改进措施.     

流动液体中夹杂物超声去除的影响因素

以高密度聚乙烯（HDPE）颗粒和水形成的悬浮液为研究体系。考察了有无超声波作用下。介质流量、夹杂物数量以及夹杂物的粒径对总去除率、上浮去除率、壁面粘附去除率的影响。实验结果表明，在短时间内（30s)超声波对流动液体中的夹杂物具有明显的去除效果。总去除率达93％。夹杂物的总去除率随着超声波输入电功率的增大而提高；超声波对较多数量或较大粒径的夹杂物去除效果更显著。超声波作用下流动液体中的夹杂物比静止液体中的更容易去除。超声波对流动液体中夹杂物去除效果的去除机理主要是通过气泡捕获夹杂物，超声空化效应产生直接包裹夹杂物的气泡以及通过夹杂物碰撞凝聚使夹杂物容易上浮实现去除。     

ZGMn13钢HAZ液化裂纹的研究

本文通过几种焊接方法的工艺因素试验,用热塑性试验和焊接热模拟试验等方法,用光镜、电镜、能谱、电子探针等显微分析手段,探讨了ZGMn13钢焊接热影响区(HAZ)裂纹的性质、形成机理和影响因素。结果表明:ZGMn13钢HAZ 裂纹为液化裂纹及其扩展的结果。这种液化裂纹主要是由于P、S 等杂质元素所形成的低熔点相、非金属夹杂物和碳化物导致晶界液化或弱化,在较大的焊接应力作用下形成的。采用小线能是CO_2气体保护焊能明显减少ZGMn13钢HAZ 的液化裂纹倾向。     

OXIDE METALLURGY-ITS PURPOSES AND PRACTICAL APPROACHES

1.IntroductionNonmetallicinclusionssuchasoxides,sulfides,oxysulphides,nitridesandcarbonitridesareharmfultosteelservicepropertiesaccordingtotheconventionalviewandexperience.Theincreasingdemandsforqualityofsteelnecessitateacurrentimprovementofsteelcleanlless.Manyeffortshavebeenundertakentoremoveoxidealldsulfideinclusiollsbysecondarymetallurgy,tundishmetallurgyandladlemetallurgyandsomespecialmethodssuchasfiltrationduringthecastingprocesslll.However,theeliminationofnonmetallicinclllsiollscanneverb…     

不同退火工艺对H13钢组织和力学性能的影响

用OM、SEM研究了亚温退火、等温退火、缓慢冷却退火3种工艺对H13钢组织和力学性能的影响。结果表明,亚温退火后碳化物粒度最小,缓慢冷却退火后碳化物粒度较大,退火硬度较低;等温退火及缓慢冷却退火对提高碳化物尺寸、分布均匀性有一定作用,同时碳化物均匀性的提高对提升H13钢退火态及淬、回火态冲击韧性有一定作用,但组织中夹杂物、一次碳化物制约着H13钢韧性的提高。     

20Cr2MoV钢焊缝金属微观分析

２０Ｃｒ２ＭｏＶ高强度热强钢用埋弧自动焊进行多道多层焊,经调质热处理后,焊缝金属的冲击性值急剧下降,不能满足使用要求。用扫描电镜分析的结果表明：焊缝金属中有较多的非金属夹杂物,特别是夹杂物附近存在微裂纹及晶界碳化物析出是造成焊缝金属低温冲击韧性值低的主要原因。     

汽车发动机进气门断裂原因分析

以断裂的汽车发动机进气门底盘为例,分析了其化学成分、硬度、显微组织、非金属夹杂物、碳化物和断口形貌。结果表明,该汽车发动机进气门断裂的诱因是B类氧化铝夹杂冶金缺陷,降低了材料的使用性能,当加载到材料自身极限荷载时,气门底盘发生断裂。     

ULTRASONIC SEPARATION OF MICRO-SIZED INCLUSIONSIN MOLTEN METAL

1. IntroductionMicro-sized non-metallic inclusibns in metal are usually detrimental to the metal ma-trix from the points of precise machining, deformation and corrosion. Therefore, theseinclusions should be removed from molten metal by using an efficient separation method.The routine methods involve floatation-separation methodology based on natural densitydifferences, ceramic filters or fine~bubble-assisted floatation-separation, and new separa-tion methods using electric or magnetic flelds h…     

回火温度对大线能量焊接用钢组织和性能的影响

通过常规力学性能测试设备、光学显微镜和扫描电镜研究了不同回火温度对一种大线能量焊接用钢性能和组织的影响。结果表明:试验钢在TMCP状态下的组织为铁素体+贝氏体+少量马氏体;高温回火后的组织主要为铁素体+回火索氏体,且析出了部分碳化物。断口呈韧窝特征,夹杂物一般为Al2O3、MnS和TiO2的两种或多种复合型夹杂物。随着回火温度升高,铁素体基体上的碳化物聚集长大。经过回火处理后,试样抗拉强度急剧下降,而冲击韧性得到大幅改善,延伸率逐渐升高,其最佳回火温度范围是600～630℃。     

The effect of impurity inclusions on the pitting corrosion behaviour of beryllium

An electrochemical polarisation study has been conducted to determine the effect of impurity inclusions on the pitting corrosion behaviour of beryllium. Three grades of commercial beryllium differing in impurity levels were used. This work showed a strong relationship between the pitting potential of the beryllium and the level of impurity inclusions, the grade with the least number of overall inclusions being the most resistant to pitting corrosion. The work also revealed the preferred sites for pit initiation, with most corrosion pits initiating at intermetallic Fe/Al/Be inclusions, and to a smaller extent at inclusion sites containing either elemental silicon or carbides.     

STUDY OF PREVIOUS POWDER-PARTICLE BOUNDARY CARBIDES

本文研究了粉末镍基高温合金FGH95中PPB问题.结果指出,PPB碳化物在雾化过程中已开始形成,在热等静压过程中继续大量析出.由于PPB碳化物化学成分及组成复杂,不同类型碳化物可发生相互作用。热处理使PPB问题更加严重.PPB碳化物的形成主要是和合金中残留氧量有关.     

Double oxide film defects in Ni-based super-alloy castings

A new class of defects has been recently discovered, which are regarded as double oxide film defects. In this study, a number of Ni-based vacuum-cast test bars were investigated. The fractures in the broken test bars were observed by Scanning Electron Microscopy （SEM）. Energy Dispersive Spectroscopy （EDS）, as well as Wavelength Dispersive Spectroscopy （WDS） were used to characterize the chemical elements of the fracture＇s surface. Observation by SEM revealed the presence of inclusions identified as films that appeared to have initiated the growth of carbides. This study has added to the evidence that oxide film defects do exist in Ni-based super-alloy in certain vacuum casting conditions. It provides a reference for researchers＇ further study on the defects, and provides a possible direction for researchers to improve casting technology so as to remove these defects.     

热处理对电冶钢结硬质合金DGJW50显微组织的影响

对DGJW50合金不同热处理状态下的组织进行了研究。结果表明:由于电冶熔铸及后续热处理加热温度很高,使碳化物相溶解并析出,从而使不同热处理的组织具有各自的特点。此材料具有三种类型的碳化物,一类碳化物与二类碳化物的性质与物理状态均不相同。本工作还测试分析了合金微观组成单元的显微硬度和不同热处理下的宏观洛氏硬度及冲击韧性。     

用EPR法评价奥氏体不锈钢的敏化程度——材质因素及敏化条件的影响

用电化学方法(EPR 法)研究了不同材料和各种敏化条件对奥氏体不锈钢敏化程度的影响,并采用摸拟贫铬区的 Fe-11%Ni-Cr(6～18%)钢,研究了 EPR 法的特性.发现对不含 Mo 的钢而言,贫铬区的铬含量在16%以下时,就发生再活化溶解,因此,EPR 法比 Strauss 法更灵敏。试验后试样表面的金相观察发现:在晶界或夹杂物周围,首先发生方向性侵蚀点,然后,连结成腐蚀沟.     

Influence of nitridation on surface microstructure and properties of graded cemented carbides with Co and Ni binders

The influence of a nitridation treatment on the microstructure and the properties of (W,Ti)C-based cemented carbides with Co and Ni binders is investigated. Nitridation results in the formation of a very fine-grained (Ti,Ta,Nb)(C,N) phase (γN-phase) with inclusions of binder and WC clusters in the near-surface region of the cemented carbides. Rietveld refinements of X-ray diffractograms reveal differences in the domain size and the microstrains of the γN-phase for cemented carbides with Co-binder and Ni-binder. Nitridation reduces the domain size and increases microstrains in the γ-phase. The chemical composition, the morphology and defects of the binder were investigated by TEM/EDX before and after the nitridation treatment. The results reveal that a high nitrogen activity leads to the preferred dissolution of the core-rim structure of the mixed cubic carbide grains during the formation of the γN-phase. The nitridation heat treatment improves the wear and corrosion resistance of cemented carbides with both Co-binder and Ni-binder.     

AN INVESTIGATION OF CERTAIN INTERGRANULAR CRACKS IN THE CORE OF A 20Cr2Ni4A STEEL BILLET

对20Cr2Ni4A钢200毫米方坯的低倍试片所出现的轴心晶间裂纹进行了观察,结果说明:轴心晶间裂纹是一种低倍酸蚀现象。它是由分布于树枝晶间的低熔点夹杂物,在低倍酸蚀过程中优先溶解而引起的。实验室内25公斤感应电炉试验,证实了轴心晶间裂纹和低熔点夹杂物有关。     

CRYSTALLIZATION AND HARDNESS CHANGE OF RAPIDLY SOLIDIFIED Fe-C-Si-Mo ALLOYS

Crystallization behavior of rapidly solidified Fe-C-Si-Mo alloy ribbons made by single rol-ler method together with their changes in phase and hardness have been studied by X-raydiffraction and SEM.The results show that the alloys attribute their very high Vickershardness to numerous fine carbides formed during crystallization.     

IN SITU OBSERVATION OF LOWER BAINITIC CARBIDES PRECIPITATION

The lower bainitic carbides precipitation in 40CrMnSiMoV steel previously austempered at310℃ was observed in situ by employing a high temperature stage of an ultra high voltageTEM(JEM-1000).The typical lower bamitic carbides were found to have precipitated fromwithin the carbide-free bainitic ferrite after tempering for certain period at a temperaturehigher than that of the isothermal transformation.This revealed that the lower bainitic ferriteis supersaturated with carbon to some extent.The carbide may also precipitate from austenite,but they have no typical morphological features of lower bainitic carbide.     

K465高温合金铝化物涂层Ni/Al互扩散系数计算

根据铝化物涂层形成过程中Al原子浓度分布，采用有限差分法反求铝化物外层Ni／Al互扩散系数．结果表明：相同温度下，铝化物外层Ni／Al互扩散系数随Al原子浓度增加而增大，表现出与Al浓度相关性；合金表面渗铝外层Ni／Al互扩散系数明显小于纯Ni表面渗铝外层Ni／Al互扩散系数．     

预热处理对FGH95高温合金粉末中碳化物的影响

对等离子旋转电极雾化(PREP)FGH95高温合金粉末颗粒在不同温度下进行预热处理，并对热处理粉末中碳化物的变化规律进行分析，结果表明：经预热处理，粉末颗粒中的MC′型亚稳碳化物发生分解和转变，析出稳定的MC，M23C6及M6C型碳化物，明显改变碳化物的稳定性和分布状态。