Abstract: A method for pretreating a sintering material using as a material at least two types of iron ore containing coarse grains and fine powder, using a first granulator to make the fine powder stick to coarse grains forming core grains so as to produce S-type granules, and using a second granulator to granulate only fine powder or mainly fine powder to produce P-type granules, which method producing the S-type granules by adjusting an amount of fine powder supplied into said first granulator so that the average stuck thickness of fine powder to the core grains becomes 50 to 300 ?m and supplying the remaining fine powder not supplied to said first granulator to the second granulator.

Abstract: A method for pretreating a sintering material using as a material at least two types of iron ore containing coarse grains and fine powder, using a first granulator to make the fine powder stick to coarse grains forming core grains so as to produce S-type granules, and using a second granulator to granulate only fine powder or mainly fine powder to produce P-type granules, which method producing the S-type granules by adjusting an amount of fine powder supplied into said first granulator so that the average stuck thickness of fine powder to the core grains becomes 50 to 300 ?m and supplying the remaining fine powder not supplied to said first granulator to the second granulator.

Abstract: A process for producing a grain-oriented electrical steel sheet excellent in the glass film and the magnetic properties by coating a steel sheet with an annealing separator, finish annealing the steel sheet, and baking an insulating coating agent, which comprises coating the steel sheet having been decarburization annealed with an annealing separator prepared by allowing 100 parts by weight of MgO to contain, in the course from the step of producing MgO to the stage of preparing a slurry in the step of coating the steel sheet with MgO, halogens selected from F, Cl, Br and I or compounds of the halogens in an amount of 0.015 to 0.120 part by weight in terms of F, Cl, Br and I, and finish annealing the steel sheet.

Abstract: The present invention relates to an improvement in the technique of heating an electrical steel slab at a low temperature. A grain-oriented electrical steel sheet having excellent magnetic characteristics and film characteristics is prepared by the process characterized in that a slab comprising, as main ingredients, up to 0.012% by weight of S, 0.010 to 0.060% by weight of acid-soluble Al, up to 0.010% by weight of N, 0.08 to 0.45% by weight of Mn, and 0.015 to 0.045% by weight is used as the starting slab, and after the decarburization annealing, the nitriding treatment is carried out at a temperature of 500.degree. to 900.degree. C. in an atmosphere having an NH.sub.3 gas concentration of at least 1000 ppm, while running the strip.

Abstract: A method of producing grain-oriented electrical steel sheet with a very high magnetic flux density, is characterized by increasing the partial pressure of the N.sub.2 in the annealing atmosphere at the intermediate stage between the start and the finish of the secondary recrystallization, and by ensuring the temperature differential in the coil does not exceed 100.degree. C. during changes to the annealing atmosphere. In addition, the rate of temperature increase at the hottest part of the coil is kept to a maximum of 13.degree. C./hr at least part of the time the coolest part of the coil is between 850.degree. C. and 1100.degree. C.