GB474544A - Improvements in and relating to methods of increasing the permeability of silicon iron - Google Patents

Abstract

In a method of increasing the permeability and lowering the coefficient of loss of commercial silicon iron the ingot is first hot rolled to from 4 to 9 times its final thickness at a temperature which gradually decreases and which during the early stages is from 1000 to 1200 DEG C., and during the later stages is from 700 to 1000 DEG C. is then quickly cooled or quenched from a temperature of from 900 to 1100 DEG C. is next cold rolled to the final thickness and is finally annealed in a non-oxidizing atmosphere for 2 to 12 hours at a temperature of from 1050 to 1350 DEG C. In a modification, the ingot is hot rolled to about 8 to 20 times its final thickness, is then quickly cooled or quenched from a temperature which falls gradually from 850 to 450 DEG C. is then cold rolled to its final thickness and is finally annealed for from 2 to 12 hours at a temperature of from 1050 to 1350 DEG C. After being hot rolled the material may be annealed for one hour at 1000 DEG C and then quenched in water. The material preferably contains from 3 to 5 per cent. of silicon and may also contain small quantities of other constituents such as manganese and aluminium, and in an example containing 3,5 per cent. of silicon and 0,15 per cent of manganese the ingot is rolled to a thickness of 5 mm. at a temperature of 1100 DEG C. and is then rolled down from 5 mm. to 2 mm. at a temperature of 850 DEG C. with repeated annealings. The material is then heated for one hour at 1000 DEG C. is next quenched in water, then cold rolled to a final thickness of 0,35 mm. and is finally annealed in hydrogen at 1250 DEG C. In another example, iron containing 3,5 per cent of silicon, 0,1 per cent of manganese and 0,1 per cent of aluminium is treated in the same way, the first example giving an initial permeability of 1,900, a maximum permeability of 35,500 and a coefficient of loss of 0,57 watts per kilogram whilst the second example gives figures of 1700, 23,300 and 0,57 respectively.