| 摘要 |
THE PRESENT INVENTION CONCERNS A METHOD FOR PRODUCING STEEL FOR LARGE MOLDS. ACCORDING TO THE INVENTION, THIS STEEL IS OBTAINED BY BEING MELTED IN AN ELECTRIC FURNACE FOLLOWED BY A SECONDARY METALLURGICAL OPERATION IN A HEATING LADLE, THIS OPERATION BEING FOLLOWED BY A DEGASSING UNDER VACUUM OF LESS THAN 1 TORR, IN FACT 0.2 TORRS OF A MIXTURE HAVING THE FOLLOWING COMPOSITION: MANGANESE 1 AT 3%, SILICON < 0.400%, PHOSPHORUS < 0.015%, CHROMIUM 1.50 AT 3.5%, MOLYBDENUM 0.25 AT 1%, NIOBIUM 0.100 -0.250%, 100 TO 300PPM TITANIUM OR ZIRCONIUM IF NECESSARY, COPPER < 0.300%, NICKEL < 0.300%, NITROGEN < 80 PPM, OXYGEN < 80 PPM, CALCIUM < 30 PPM, 15 TO 50 PPM BORON, 0.10 TO 0.25% CARBON, SULFUR < 0.050%, ALUMINUM < 250 PPM.
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