How to select current frequency for steel pipe heating?

When the steel pipe is heated by induction, the selection of frequency must follow two conditions:

1，f≥3000/ d*d

2，0.35b

d—— tube inner diameter (cm)

a—— tube wall thickness (cm)

b—— Extent of metal internal current penetration

In determining the heating time of steel pipe, the steel pipe can be considered as solid cylindrical blank. At this point, the thickness of the pipe wall should be regarded as the radius of the cylindrical blank.