对比了小螺距螺栓清洗前后的荧光渗透检测结果，发现螺栓根部表面开口裂纹缺陷无荧光显示的主要原因是裂纹开口污染物阻碍了渗透液的有效渗入。对螺栓表面进行彻底清洗，能够有效提高裂纹缺陷的检出率；采用高灵敏度和超高灵敏度的渗透液能提高裂纹的检出能力。综合考虑检测准确性和成本等因素，采用高灵敏度的渗透液进行检测更为适宜。

By comparing the results of fluorescence penetration detection before and after cleaning of the small pitch bolts, it was found that the main reason why the cracks on the surface of the root of the bolts did not show fluorescence was that the dirt at the opening crack impeded the effective penetration.The detection rate of crack can be effectively improved by thoroughly clearing the bolt surface. Furthermore, crack detection ability can be improved by using high-sensitivity and super-high-sensitivity penetrant. Considering the accuracy and cost of detection, it is more suitable to use high-sensitivity penetrant for small-pitch bolt detection.