GB870220A - Non oriented silicon-iron sheet stock and process of making it - Google Patents

Abstract

A process for the manufacture of nonoriented silicon-iron sheet comprises hot rolling to an intermediate gauge e.g. 0.07 inch a silicon-iron containing from 0.5% to 3.8% silicon, from 0.02% to 0.08% carbon, and not more than 0.5% aluminium the balance being iron, except for unavoidable impurities, pickling the hot rolled material, cold rolling it to final gauge e.g. between 0.014 and 0.025 inch without intermediate annealing, and then annealing at a temperature of 1950 DEG to 2200 DEG F. in a decarburizing atmosphere thereby removing a part of the carbon therein, while leaving a total carbon content in excess of 0.01%, and then pickling the stock, the said stock being susceptible to further decarburization after punching into laminae in an annealing treatment in a decarburizing atmosphere at a temperature of 1400 DEG to 1700 DEG F. to a total carbon value of less than 0.01%. The first annealing is carried out in an atmosphere oxidizing to iron and silicon. In an example the annealing is carried out on a siliconiron containing from 1.5% to 2.0% silicon and not more than 0.03% carbon which produces a phase change fom gamma to alpha iron at the surfaces of the material, the said phase change resulting in the production of new grains of columnar form at said surfaces and in which the second annealing treatment produces an enlarged grain size as a derivative of said columnar grams. Stock having magnetic properties not completely developed and not yet subjected to the second annealing operation may be sold as semi-processed stock and the purchaser carries out the second anneal to fully process the stock after he has stamped out the required laminae. Specification 558,558 is referred to.