GB562563A - Improvements in or relating to magnetic means for the detection of the quality of steel - Google Patents

Abstract

562,563. Magnetic tests and measurements. APPLEBY-FRODINGHAM STEEL CO., Ltd., and REEVE, L. Dec. 29, 1942, No. 18464. [Class 37] An arrangement for testing the quality of magnetic material such as steel comprises one or more yokes of magnetic material applied to the test piece so as to form therewith a magnetic circuit system, primary and secondary windings arranged on this system, the primary winding being wound in sections which are magnetically in opposition and are such that the flux in one direction preponderates over that in the other, means for energizing the primary winding, and means for measuring the current consequently induced in the secondary winding. Three primary windings 3 are arranged as shown on the yoke 2 applied to the test piece 1 and are connected in series so that two of the windings produce flux in one direction and one produces flux in the opposite direction. A secondary winding 4 is provided at one extremity of the yoke 2. The primary winding is supplied by means of a battery 5 through a switch 6 and the current induced in the secondary winding 4 when the circuit is made and broken is measured by a milliammeter 7. A rheostat 8 and an ammeter 9 are provided for adjustment of the primary current to a standard value. In a modification, the coils are placed on the test piece 1, the three primary sections being arranged end to end and the secondary winding beyond one end of the set of primary sections. Two, yokes may be employed, both applied to the steel piece under test, one carrying the primary winding and the other the secondary winding.. In this case the yoke carrying the secondary winding only receives the leakage flux which fails to pass through the primary magnetic circuit, so that the greater the permeability the less the secondary current. The yoke may be provided with polepieces shaped to fit the surface of the test piece. Alternating current may be employed instead of direct current, the instrument 7 then being modified for use with alternating current.