Method for manufacturing oriented silicon steel product with high magnetic-flux density

Abstract

A method for manufacturing an oriented silicon steel product with high magnetic-flux density comprises the following procedures: 1) smelting and casting, wherein the oriented silicon steel is composed of, by weight, 0.035˜0.065% of C, 2.9˜4.0% of Si, 0.05˜0.20% of Mn, 0.005˜0.01% of S, 0.015˜0.035% of Al, 0.004˜0.009% of N, 0.005˜0.090% of Sn, 0.200˜0.800% of Nb, the rest being Fe; and after being smelted, molten steel is secondarily refined and continuous casted into steel slabs; 2) hot rolling; 3) normalizing; 4) cold rolling; 5) decarburization annealing; 6) MgO coating; 7) high temperature annealing: said sheets are firstly heated to 700˜900° C. and then secondarily heated to 1200° C. at temperature rise rate of 9˜17° C./hr and maintained at 1200° C. for 20 hr; 8) coating an insulation layer. According to the present invention, steel sheets can be fully nitrided during high temperature annealing, which can ensure a secondary re-crystallization to take place perfectly, thereby, the oriented silicon steel sheets with high magnetic-flux density can be achieved. The present invention solves the problem of nitriding that is encountered in production of high-magnetic-induction oriented silicon steel by the technique to heat steel slabs to a lower temperature.

1 . A method for manufacturing an oriented silicon steel product with high magnetic-flux density comprising the following steps:
 casting oriented silicon steel into steel slabs after the silicon steel is smelted and secondarily refined, wherein the oriented silicon steel is composed of, by weight, 0.035˜0.065% of C, 2.9˜4.0% of Si, 0.05˜0.20% of Mn, 0.005˜0.01% of S, 0.015˜0.035% of Al, 0.004˜0.009% of N, 0.005˜0.090% of Sn, 0.200˜0.800% of Nb, the rest being Fe and unavoidable inclusions;   heating said steel slabs in a heating furnace to 1090˜1200° C.;   hot rolling said steel slabs into steel plates at a beginning temperature of 1180° C. and finishing hot rolling said steel slabs at a finishing temperature of 860° C.;   cooling said steel plates using laminar flow of water to below 650° C.;   coiling said steel plates into coiled-shape plates;   normalizing said coiled-shape plates at a normalization temperature of 1050˜1180° C. for 1˜20 sec and at a normalization temperature of 850˜950° C. for 30˜200 sec, and then immediately thereafter cooling down the plates at a cooling rate of 10˜60° C./sec;   wherein after being normalized, cold rolling said steel plates into steel sheets with a thickness of a finished sheet at a rolling compression ratio not less than 75%;   decarburizing said steel sheets to a temperature of 800˜860° C. at a temperature rise rate of 15˜35° C./sec and maintained at the temperature for 90˜160 sec;   coating said steel sheets with a coating including, by weight, 0.1˜10% of NH 4 Cl and 0.5˜30% of P 3 N 5 , and MgO as the rest component where the MgO is a main component;   heating said steel sheets to a temperature of 700˜900° C., and then heating said steel sheets to 1200° C. at a secondary temperature rise rate of 9˜17° C./hr and maintained at 1200° C. for 20 hr; and   coating surfaces of the steel sheets with an insulation layer.