反差增强剂在磁粉检测中的应用

反差增强剂应用在实际磁粉检测中受到一定的约束。通过对比试验结果,分析总结了反差增强剂的施加厚度与施加速度、距离之间关系以及对检测灵敏度的影响,为实际生产中正确推广应用反差增强剂提供了经验依据。     

反差增强剂在蒸压釜釜齿磁粉检测中的应用

蒸压釜釜齿易产生裂纹,釜齿磁粉检测中磁痕与釜齿颜色接近,对比度差,易漏检。介绍了反差增强剂应具有的一些特性和施加方法。给出了反差增强剂使用时的要点,如表面预处理、薄膜光泽度、喷罐搅拌、喷涂方法、风干成膜、成膜厚度、磁悬液喷洒要点、触头法要点、重点检测部位等。     

矿用提升容器重要承载件的现场磁粉探伤

论述了矿用提升容器重要承载件表面检测方法的选择和工艺。根据MT684—1997《矿用提升容器重要承载件无损探伤方法与验收规范》标准规定,对三环链、矿车连接插销、楔形连接器、U型环、离合器齿圈等重要部件进行磁粉检测,能有效地检测出裂纹等危害性缺陷。     

提高荧光磁粉对液化气槽车缺陷的检出率

对汽车罐车以往的检验情况进行分析，对其探伤工艺进行了改进，使用改进后的工艺不仅提高了对缺陷的检出率，而且也提高了对微小缺陷的检出能力。     

磁粉检测反差增强剂的施加环节

磁粉检测需要进行水断(润湿性能)试验和标准试片系统灵敏度验证,而施加反差增强剂的环节,将对检测结果及检测流程造成一定的影响。分析这三者在检测过程中的目的及作用,优化检测工艺,保证了检测结果的准确性。     

复合钢板结合部位缺陷的磁粉检测

介绍了采用直流磁轭方法检测表面覆盖有不锈钢的复合钢板缺陷的工艺、过程、结果以及返修方法。证明了采用磁粉方法,透过不锈钢覆盖层,检测基体为铁磁性材料中缺陷的可行性。所得检测结果可与射线和超声波检测结果形成印证,具有实际应用价值。     

曲面工件近表面缺陷的磁粉检测

介绍利用磁粉检测发现在用含碱性柴油精制管道近表面缺陷如何选择便捷式直流磁粉探伤机、磁轭调整和磁化方法,并分析了裂纹产生的原因。     

主蒸汽管道表面缺陷的磁粉检测研究

介绍电站锅炉主蒸汽管道磁粉检测可行性,对其磁特性进行了较详细的分析,在实验基础上给出了主蒸汽管道磁场强度的有效选择。     

典型缺陷磁粉检测数据的统计与分析

针对在锅炉压力容器无损检测Ⅱ级MT人员资格考核中的标准试板典型缺陷的检测数据，进行了统计与分析，得出了一些很有意义的结论。     

锻件磁粉检测缺陷性质的分析

1 问题的提出 某批用于加工精密关键零件的0Cr17Ni4Cu4Nb锻件(尺寸约为55 mm×35 mm×30 mm),在完成锻造及热处理工序,并对外表面进行铣加工后进行磁粉检测(MT).     

4140悬挂器磁粉探伤裂纹检验分析

材料4140悬挂器锻件经精加工后进行表面磁粉探伤,发现其端面有裂纹.为查明裂纹原因,对其进行解剖取样检验分析.结果表明:裂纹是在淬火或回火之前形成的,属于淬火组织应力引起的端部裂纹,裂纹大部分处于深色偏析条带中,表明深色偏析条带是裂纹形成原因之一,裂纹主要以沿晶扩展,并与深色偏析条带区中微量有害元素沿晶界析出有关.     

42CrMo钢曲轴连杆颈磁痕显示的成因分析

利用磁粉探伤对42CrMo钢曲轴锻件的连杆颈部位进行检测,发现明显的类似发纹的磁痕显示。通过OM、SEM形貌观察和EDS成分分析发现,连杆颈表层部位基体的显微组织不均匀,出现明显的成分偏析带,宽度约20~50 μm,C、Mn、S、Al、Cr元素含量相对基体较高,并含有少量的MnS夹杂。42CrMo钢棒状原料的中心偏析在模锻时沿着金属流动方向发生转动,偏析流线“遗传”至终态连杆颈表层而造成显微组织和化学成分的不均匀,进而导致磁导率的差异而出现磁痕显示。锻后的调质处理和表面感应淬火在一定程度上可以改善但不能消除这种宏观成分偏析。     

试样厚度对韧脆转变温度区间的影响

根据BSI 7448 Part I标准,测定了海洋平台用钢E36以裂纹尖端张开位移(CTOD)为表征的韧脆转变温度曲线. 通过改变试样厚度,研究面外拘束对韧脆转变温度区间的影响并分析了其变化规律. 结果表明,E36钢具有典型的韧脆转变特征,其韧脆转变温度曲线可以用Boltzmann函数进行拟合,具有良好的相关性;试样厚度越大,韧脆转变温度越高,断裂性能下降. 通过有限元模拟分析三维裂纹尖端应力状态,选择了面外拘束参数Tz,用来阐述厚度效应对韧脆转变温度的影响,具有良好的相关性.     

不锈钢调整垫圈线性磁痕显示的分析

对某调整垫圈(9Cr18不锈钢)进行磁粉检测时,内孔发现线性磁痕显示,通过荧光渗透检查及金相法检查,确认线性磁痕显示与碳化物偏析有关。对磁化工艺进行分析,以及制作特殊样件并进行试验,结果表明:对于该调整垫圈,经验公式法计算得到的磁化电流偏大。通过控制零件表面切向磁场强度,可以有效地排除偏析磁痕显示的干扰。     

Effect of plasma fluctuations on in-flight particle parameters

The influence of arc root fluctuations in direct current (DC) plasma spraying on the physical state of the particle jet is investigated by correlating individual in-flight particle temperature and velocity measurements with the instantaneous voltage difference between the electrodes. In-flight diagnostics with the DPV-2000 sensing device involve two-color pyrometry and time-of-flight technique for the determination of temperature and velocity. Synchronization of particle diagnostics with the torch voltage fluctuations are performed using an electronic circuit that generates a pulse when the voltage reaches some specific level; this pulse, which can be shifted by an arbitrary period of time, is used to trigger the acquisition of the pyrometric signals. Contrary to predictions obtained by numerical modeling, time-dependent variations in particle temperature and velocity due to power fluctuations induced by the arc movement can be very large. Periodic variations of the mean particle temperature and velocity, up to ΔT=600 °C and Δv=200 m/s, are recorded in the middle of the particle jet during a voltage cycle. To our knowledge, this is the first time that large time-dependent effects of the arc root fluctuations on the particle state (temperature and velocity) are experimentally demonstrated. Moreover, large fluctuations in the number of detected particles are observed throughout a voltage cycle; very few particles are detected during parts of the cycle. The existence of quiet periods suggests that particles injected at some specific moments in the plasma are not heated sufficiently to be detected.     

某螺栓锻件表面平行线状磁痕显示原因分析

某螺栓锻件磁粉检测时发现磁痕显示,通过金相观察、能谱分析及X射线衍射分析等试验后确认,该磁痕为原材料微观偏析组织导致材料磁导率出现差异而形成的非相关显示。     

Effect of alternative magnetic field on the diffusion layer growth in Al／Zn couple

The influence of an alternative magnetic field on the growth of the diffusion layer in A1-Zn diffusion couple was studied. The thickness of the diffusion layer was examined. The results show that the alternative magnetic field increases the thickness of the diffusion layer and the effect increases with the intensity and frequency of the alternative magnetic field increasing. The growth of the diffusion layer obeys the parabolic rate law and the growth rate increases with the application of the alternative magnetic field. This growth rate change is manifested through a change in the frequency factor ko and not through a change in the activation energy Q. The frequency factor k0 for the diffusion layer growth with the alternative magnetic field is 5.03cm^2/s and the one without the magnetic field is 3.84cm^2/s.     

Effect of Ti layer thickness on microstructure and magnetic properties of Ti/Co/Ti films

TiCoTi granular films were prepared by DC facing-target magnetron sputtering system onto glass substrates and subsequently in situ annealing in vacuum. Structural of Ti ( t nm)/Co (40 nm)/Ti ( t nm) films were investigated in detail, which shows that the majority Co nanograins are formed as the hexagonal-close-packed (HCP) structure. Vibrating sample magnetometer (VSM) and scanning probe microscope (SPM) were applied to study the magnetic properties, morphologies and domain structures of these samples. It has been found that the structure and magnetic properties of the Ti/Co/Ti films depend strongly on the Ti layer thickness. The out-of-plane coercivities ( Hc) of the film is maximum about 78.8 kA·m-1 when t =5 nm with annealing at 300 ℃; the distributing of grains of the sample is uniformity; and the average size of particles is about 13 nm. The obtained results suggest that this system is perpendicular anisotropy and might be applicable to perpendicular magnetic recording media.     

Effect of spray particle trajectory on the measurement signal of particle parameters based on thermal radiation

The influences of the dimensions of optical components and the trajectories of spray particles on the variations of the waveforms of the radiation signals from the spray particles were studied both theoretically and experimentally for correct simultaneous measurement of the particle parameters including particle velocity, surface temperature, size, and spatial distribution. Two types of filtering masks, including single-windowed and dual-windowed, were used as models in the current study. The evolution of the radiation pulse from a moving thermal spray particle was simulated through the change of the projected area of the particle image spot on the filtering mask window. The experimental detection of the thermal radiation pulses was performed for the high velocity oxygen fuel (HVOF) process using an optoelectronic measurement system. The theoretical simulation clearly showed that the characteristic waveforms of the thermal radiation signals from the spray particles are varied with the distance and orientation of the trajectories of thermal spray particles with respect to the ideal image plane of the filtering window plane. The typical variations of the characteristic waveforms obtained theoretically have been observed experimentally with HVOF spraying. The waveforms expected theoretically were correlated well with those observed experimentally. The characteristic waveforms of the radiation signals from the spray particles in a trapezoid shape with a saturated top platform contain the information for spray particle parameters including velocity, surface temperature, size, and spatial distribution. With the dual-windowed filtering mask, the particle velocity can be correctly measured with the bi-peak radiation signal in triangle-like shape, and the surface temperature may be estimated reasonably. However, the particle size cannot be estimated correctly. It was revealed that the characteristics of the waveforms were remarkably influenced by the image spot size. Therefore, the expansion of the image spot based on the relation between the image spot size of an in-flight particle and optical lens parameters obtained optically was discussed. The influence of the image spot size on the waveform characteristics was examined.