关于直流机换向的探讨

直流机换向是相当复杂的问题,产生火花的原因是多方面的。但是无论什么原因产生的火花集中表现在:①在刷子与整流子之间通过的电流超过允许值;②刷子与整流子之间的接触不良。不少人从电流方面来研究换向问题,这是研究换向问题的理论基础。本文则从刷子与整流子之间的接触状态来讨论换向问题,着重阐述刷子与整流子表面之间的接触电阻、氧化膜形成、摩擦、湿度、刷子压力等对换向的影响。     

轧钢厂直流电机的维护与管理

根据现场多年的检验经验,通过分析直流电机的结构,介绍了轧钢厂直流电机的定子绕组、转子绕组和整流子的维护方法,并着重介绍了充子的氧化膜的形成和整流子车削的工艺标准,在直流电机设备管理方面,通过建立电机设备档案,强化电机状态检测,加强检验人员的业务培训,提出了一套先进的管理模式。     

直流电机换向故障分析与处理

对坑口提升用直流电机换向器表面氧化膜的形成、性能、作用以及影响它的因素进行了分析和讨论。充分认识和了解氧化膜性能，对直流电机换向故障维修提供了依据和帮助。     

2800mm冷轧主传动电机冷却风机的节能改造

主要阐述变频器对大功率直流电机冷却风机电机控制的实际应用.采用变频器控制,既保证了大功率直流电机的冷却效果以及换向极氧化膜的保护,同时节能显著.     

大型直流电机整流子的带电车削

影响大型轧钢直流电对机换向的因素很多．但造成整流子换向火花增大的主要原因是整流子表面偏摆超标。为解决上述问题．对整流子进行了带电车削，取得成功。切削速度为1～1．5mm／s，切削深度0．2～0．3mm，每次进刀速度0．1～0．15mm／s。     

励磁机整流子的现场维修车削

我厂热电站的励磁机与其它直流电机一样，它的电刷与整流子表面之间是滑动接触的。在长期运行中整流子表面工作状态不断发生变化，如整流子铜片磨损、片间云母凸出、电刷过度磨损、弹簧压力不够、以及发电机组轴瓦检修调整，造成励磁机电枢动平衡不良等变化；都将造成电刷与整流子之间无法保持稳定的滑动接触，电刷下面的火花逐渐增大，使整流子表面出现有规律的烧伤，如呈麻点状的烧灼点、条痕，这些烧伤和磨损是不均匀的，所以使整流子表面形成轴向波浪度。上述整流子表面工作状态恶化现象，直接影响励磁机正常运行和发电机发电，严重者会…     

3号飞剪高速剪切大火花的成因及解决办法

广钢连轧线3号飞剪在高速剪切线速度大于15m／s的棒材时，造成驱动它的直流电机整流子与碳刷接触面瞬间大火花，这样对整流子造成较大的伤害，严重影响了电机的寿命．文章对其火花的成因及相应的抑制方法提出初步的探讨．     

四辊轧机直流电动机整流子表面烧损原因分析及改进措施

本文针对四辊轧机电动机拖动系统存在的问题进行了介绍和分析,找出了改进后直流电机整流子表面烧损的原因,提出了相应的改进措施.     

走向21世纪的炼铁技术

本文介绍一种通过磁场换各来取代原有的直流电机中电刷换向，从而获直流电机特性的新型电机。     

直流电机换向火花的原因分析及处理

本文详细分析了直流电机换向火花的原因，介绍了具体的检查处理方法，并作了举 例说明。对从事直流电机管理和维检工作的人员有一定的指导意义。     

8407钢渗铝氧化处理形成的氧化膜组织与结构

对渗铝后的8407钢试样进行常温硬质阳极氧化处理,使其表面形成氧化膜。通过金相显微镜观察氧化膜横截面组织,并探讨了氧化膜的形成机制;采用扫描电镜观察氧化膜表面形貌,并检测氧化膜沿厚度方向的化学成分及其分布;利用X射线衍射仪对氧化膜相组成进行分析。结果表明,渗铝8407钢经过常温硬质阳极氧化后,试样表面分为3层,从基体向外侧依次为基体、渗层、氧化膜。氧化膜连续致密,厚度均匀,与基体结合紧密,其主要成分为O、Al和Fe,且各元素分布均匀,主要相组成为Fe3O4和Al2O3。     

阳极氧化用3003铝合金冷轧带材组织条纹的成因分析与改进措施

试验研究了3003铝合金冷轧带材阳极氧化后表面条纹的产生原因,结果表明:表面条纹缺陷是一种组织条纹,其产生的根本原因是带材内部存在沿着轧制方向、间断分布的异常粗大晶粒组织。异常粗大的晶粒影响氧化膜的形成和形态,使氧化膜的大小、形态、数目异常,宏观表现为条纹。另外,第二相粒子会起到抑制、阻碍晶粒长大的作用,从而影响阳极氧化膜的形成,间接对组织条纹的产生起到影响和抑制作用。解决组织条纹的根本途径在于通过调整熔炼、在线处理、铸造、均匀化加热各工序的工艺要素来细化合金晶粒。     

Effect of oxide film structure of grain oriented silicon steel on depth of nitriding layer

Nitriding treatment after decarburization annealing is one of the key technologies to produce low temperature high permeability silicon steel. By controlling decarburization atmosphere, different oxide film structures were obtained; and then, the effect of oxide film structure on depth of nitriding layer with approximate nitrogen content was studied. The results show that oxide film is divided into two parts: the outer granular oxide film and the inner layered oxide film. As the dew point of decarburization atmosphere increases, the oxygen content of the decarburization plate increases, the thickness of the oxide film increases, the thickness ratio of layered oxide decreases, and the depth of nitriding layer increases. When the thickness ratio of layered oxide film is relatively high, ［N］ accumulates on the extreme surface of the sample, forms a unimodal distribution of ［N］ along the thickness direction, and the nitriding layer is relatively thin. When the layered oxide film ratio is relatively low, ［N］ crosses this layer and accumulates again in the subsurface; thus, in addition to the ［N］ peak on the extreme surface, one or more ［N］ peaks form in the subsurface, and the nitriding layer is relatively thick.     

取向硅钢氧化膜结构对渗氮层深度的影响

摘要：低温板坯加热技术生产取向硅钢,其关键点之一在于脱碳退火后要进行渗氮处理。通过控制脱碳气氛,获得不同的氧化膜结构;并进一步分析在近似渗氮量条件下,氧化膜结构对渗氮层深度的影响。结果表明：氧化膜分为外层颗粒状氧化膜和内层层片状氧化膜两部分。随着脱碳气氛露点增加,脱碳板O含量增加,氧化膜厚度增厚、层片状氧化膜占氧化膜总厚度的比例下降,渗氮层深度增加。当层片状氧化膜厚度占比较高时,［N］原子积聚在试样的极表层,形成氮沿厚度方向的单峰分布,渗层较浅。当层片状氧化膜厚度占比较低时,［N］原子会越过该层,而在次表层再次发生积聚;从而除了极表层的氮峰外,在次表层形成一个或多个氮峰,渗层较深。     

电液比例控制技术在开卷机机组中的应用

着重介绍电液比例控制技术在液压驱动开卷机组控制中的成功运用。运用电液比例控制技术是机列恒速度和恒张力功能得以实现的关键保证。电液比例控制液压驱动与传统的直流电机驱动相比,体现了当今世界机、电、液一体化的发展方向。其机械设备结构简单、控制方便     

Structure Analysis of Oxidation Film of Ignition-Inhibition AZ91D Magnesium Alloy Added with Cerium

The effect of cerium on ignition temperature of AZ91D magnesium alloy was studied. By the addition of cerium of 1%, the ignition temperature is raised by 180℃, so the magnesium alloy added with cerium can be melted in air. The burning temperature increases with the increasing of cerium. The structure and chemical compositions of the surface oxide film were investigated by XRD and Auger electron spectrometry(AES). The results of XRD indicate that the oxide film of the surface of ignition-inhibition magnesium alloy can change from loose structure of simple magnesia to compact composite structure consisting of magnesia, cerium oxide, Mgl7 A112 and aluminum oxide, which has excellent ignition-inhibition effect. AES depth profile analysis shows that the oxide film can be divided into three layers. The outside layer is mainly made up of magnesia, the middle layer, which consists of cerium oxide, magnesia, and aluminum oxide, is compound and compact. Thermodynamic analysis indicates that the structure of the surface oxide film is accordant to the change of free energy and high vapor pressure of magnesium.     

马钢CSP高铬铁工作辊表面氧化膜控制研究

热轧工作辊的在线氧化膜对带钢表面质量影响很大,轧辊表面氧化膜剥落直接导致带钢表面产生二次压氧缺陷。通过大量的现场试验及相关理论,本文分析了高铬铁轧辊氧化膜的动态变化过程、轧辊氧化膜形成及剥落的原因,并提出相应控制措施,取得了较大成效。     

The Effect of Anodic Oxide Films on the Nickel-Aluminum Reaction in Aluminum Braze Sheet

The influence of an anodic oxide surface film on the nickel-aluminum reaction at the surface of aluminum brazing sheet has been investigated. Samples were anodized in a barrier-type solution and subsequently sputtered with nickel. Differential scanning calorimetry (DSC) and metallography were used as the main investigative techniques. The thickness of the anodic film was found to control the reaction between the aluminum substrate and nickel coating. Solid-state formation of nickel-aluminum intermetallic phases occurred readily when a relatively thin oxide film (13 to 25 nm) was present, whereas intermetallic formation was suppressed in the presence of thicker oxides (~60 nm). At an intermediate oxide film thickness of ~35 nm, the Al₃Ni phase formed shortly after the initiation of melting in the aluminum substrate. Analysis of DSC traces showed that formation of nickel-aluminum intermetallic phases changed the melting characteristics of the aluminum substrate, and that the extent of this change can be used as an indirect measure of the amount of nickel incorporated into the intermetallic phases.

     

Effects of lanthanum ion-implantation on microstructure of oxide film formed on Co-Cr alloy

Isothermal and cyclic oxidizing behavior of Co-40Cr alloy and its lanthanum ion-implanted samples were studied at 1000 ℃ in the air by thermal-gravimetric analysis （TGA）. Scanning electronic microscopy （SEM） and transmission electronic microscopy （TEM） were used to examine the morphology and structure of oxide film after oxidation. Secondary ion mass spectrum （SIMS） method was used to examine the binding energy change of chromium caused by La-doping and its influence on the formation of Cr2O3 film. laser Raman spectrum was used to examine the stress changes within the oxide film. It was found that lanthanum implantation remarkably reduced isothermal oxidizing rate of Co-40Cr and improved anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement were mainly that the implanted lanthanum reduced the grain size and internal stress of Cr2O3 oxide and increased high temperature plasticity of the oxide film. Lanthanum mainly existed on the outer surface of Cr2O3 oxide film in the form of fine La2O3 and LaCrO3 spinel particles.