The Effects of the Punching Process Upon the Magnetic Properties of Steel Laminations

Abstract

The punching process used to stamp out iron laminations
Causes a deterioration in the magnetic properties of the
lamination material. This investigation is concerned with an
experimental examination of the deterioration and finding the
magnitude of the change in material properties due to punching.
The punching effect is considered in terms of the ratio of
total surface area of the lamination to the punched area, the material
thickness and the punching tool clearance.

Annular laminations of various sizes are punched out of sheet
material and their magnetic properties measured under static and
dynamic conditions. The material is then annealed and the tests
repeated. A particular feature of the investigation is the
equipment used for the dynamic tests. This consists of an
electronic hysteresigraph, which maintains the rate of change of
flux density constant for each hysteresis loop, used in conjunction
with a specially designed test rig and an on-line digital
computer.

A metallurgical analysis of the material is made so as to
obtain the optimum temperature for annealing and also to assist in
determining the extent of the plastic deformation. The deformation
of the punched edge is also examined in terms of its micro-hardness
and the Kerr optical method is used to investigate the reduction
in permeability in the region of the punched edge.

Date of Award	1972
Original language	English