GB184215A - Apparatus for the determination of the percentage of carbon in iron and steel - Google Patents

Abstract

184,215. Malmberg, C. J. G., and Holstr÷m, J. G. March 11, 1921. Magnetic measure - ments.- The percentage of carbon in a specimen of iron or steel is obtained by apparatus provided with means for subjecting the specimen to re. peated magnetizations and demagnetizations between two chosen values of magnetizing-force and for then measuring the difference of magnetic flux at these two values. In one arrangement for carrying out the invention, shown in Fig. 2, the specimen is inserted into a coil 2, and is of such a length and shape that it form a magnetic circuit with screens 5. 6 and core-piece 8. The magnetizing - coil 1 is wound around the core-piece and is in series with a rheostat 12. A second rhecstat 13 may be shunted across this circuit which is completed when a lever 14 operated by clock-work described below makes contact with the projection 19 carried by a blade spring 15. Instead of using a magnetizing-coil permanent magnets geared up to the clock-work for rotation may be employed. One such arrangement is shown in Fig. 4 wherein the screens 5, 6 project through the box 61 constructed of insulating-material. Soft-iron pieces 51, 52 are slidably mounted with a bolt 56 to increase or decrease as desired, air gaps between the rotating magnet and screens. A softiron plate 66 prevents any leakage of magnetizing-forces at the half-revolution periods. Instead of rotating the magnet as shown the shaft may be displaced through 90‹ so that the magnetizing- force fluctuates between a positive and a negative value. In a further arrangement a soft-iron armature is geared to the clock-work and rotates between extensions of the magnet which in this case is stationary, and the adjustable air gap consists of a spring plate depressed and elevated by a thumb-screw. In another modification both softiron pieces between the magnet and screens are mounted on a drum which is rotated by the clockwork, and the air gaps are adjusted by moving the magnet itself. The coil 2 may be placed on other parts of the magnet itself. The parts of the magnet circuit, which is, with all its constituent parts, enclosed in an iron box. Clock-work for automatically effecting the measurement has a shaft 18 upon which are mounted a pinion 16 and cams 25, 32. and it is started by pressing the button 44, which movement is transmitted through spring-retained levers, and allows a catch 36 to lift over a tooth 34 on the cam 32. Rotation of the pinion and cams then proceeds until the catch 36 is brought up against a tooth 33 on the cam 32. The button 44 is then again depressed and the galvanometer circuit is completed by the cam 25, forcing the lever 21 against a contact 28 carried by a blade spring 22. This operation takes place first after the final magnetization has taken place and when completed, the lever 21 drops behind the cam projection 26 and damps the galvanometer by short-circuiting it through a resistance 31.