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按工艺要求配制的磁悬液,经现场大批量零件的磁粉探伤后,由于零件带走了部分磁粉,使磁悬液浓度降低,从而降低探伤灵敏度。因此,工艺要求探伤人员每天在探伤前先检查磁悬液浓度,若不符合工艺要求时应添加磁粉,以保持相对固定的磁悬液浓度。传统检查现场使用的磁悬液浓度是采用测量磁粉容积的梨形沉淀管法。但实践中,该方法在很多场合是无法使用的,荧光磁悬液和非荧光磁悬液情形都一样。在大批量零件的探伤中,由于零件上的污物,如沙土和氧化锈等带入磁悬液中,而用该方法测定的结果是,使用一段时间后的磁悬液浓度反而比原先的磁悬液浓度大。为此,我国磁粉探伤工作者进行了一些研究,如北京内燃机总厂无损探伤室于80年代中期,用光电转换法研制了荧光磁悬液浓度测定仪;西安交大用电磁感应法研制了既可测定荧光磁悬液浓度,又可测定非荧光磁悬液浓度的测定仪;航空工业部北京621所研究用磁粉检验(MT)标准缺陷试块法检查磁悬液性能并纳入标准等。
Magnetic suspension prepared according to process requirements, the field of large quantities of parts after the magnetic particle inspection, the parts take away part of the magnetic powder, so that the magnetic suspension concentration is reduced, thereby reducing the detection sensitivity. Therefore, the process requires testing personnel to inspect the concentration of magnetic suspension before testing, if not meet the process requirements, magnetic powder should be added to maintain a relatively fixed magnetic suspension concentration. The concentration of magnetic suspension used in the conventional inspection is the pear-shaped sedimentation tube method that measures the volume of magnetic powder. However, in practice, this method can not be used on many occasions. Fluorescent magnetic suspensions and non-fluorescing suspensions are the same. In the detection of large quantities of parts, due to the dirt on the parts, such as sand and oxidation rust into the magnetic suspension, and the results of this method is determined by the use of magnetic suspension after a period of time rather than the original concentration Magnetic suspension concentration. To this end, China’s magnetic particle inspection workers conducted some research, such as non-destructive testing chamber of Beijing Internal Combustion Engine Plant in the mid-1980s, the use of photoelectric conversion method developed fluorescent magnetic suspension concentration detector; Xi’an Jiaotong University by electromagnetic induction developed either Determination of the concentration of fluorescent magnetic suspension, but also the determination of non-fluorescent magnetic suspension concentration of the instrument; Aviation Industry Beijing 621 study with magnetic particle testing (MT) standard defect test block method to check the magnetic suspension properties and included standards.