Some definitions of eddy current flaw detection

I don't know what you're asking about the steel pipe/steel bar injury. Let me take the steel pipe/steel bar as an example first:

1. The higher the vortex frequency, the smaller the penetration depth and the coarser the stainless steel grain. In order to reduce the influence of noise, the penetration detection frequency of stainless steel is generally higher than that of carbon steel, generally above 6k, and at most 12k (because the zero potential of the penetration probe has affected the detection at higher frequencies). Point probes, whether carbon steel or stainless steel, generally choose tens or even hundreds of K, regardless of frequency. No matter what eddy current flaw detection method, according to the standard requirements, it is generally enough to reliably detect the artificial defects on the sample and have sufficient signal-to-noise ratio.

2. Whether manually or automatically, the blind spots at the head and tail are generally judged according to the distance from the head and tail to the nearest detectable artificial defect (refer to YB/T 4083). This equipment can distinguish the minimum distance between the artificial defects of the head and tail of the workpiece and the head and tail of the workpiece (for eddy current, the change of the head and tail of the workpiece is a big defect), which is the blind spot of the head and tail.