In the Japan railway company group, magnetic particle inspection is performed as the final inspection for rail welds by flash and gas pressure welding. Approximately 50% of rails are welded by these methods every year. Then, we have proposed a new magnetic particle inspection procedure to improve the accuracy of inspection. There are two kinds of magnetic particles. One is a fluorescent magnetic particle and the other is a nonfluorescent particle. Fluorescent magnetic particles are now generally used for better perception of indication. Then, new nonfluorescent magnetic particles have been recently developed for the inspection of rail welds based on the studies concerning the size and concentration of magnetic particles in order to improve daytime workability.

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