| 摘要 |
PROBLEM TO BE SOLVED: To judge and adjust the condition of slag foaming and to enable stable production of a low nitrogen steel by measuring NOx content in exhaust gas at refining and temp. raising period of molten steel in producing the molten steel from iron scrap in an arc type electric furnace. SOLUTION: Main raw material composed of iron scrap and one or more kinds among molten pig iron, solid pig iron, reduced iron and iron carbide, are heated and melted in the arc type electric furnace 1 with the arc 4 generated between an upper electrode 2 and furnace bottom electrodes 3. At this time, in the melting period of the main raw material, a slag removing hole 5 in the furnace is fully closed and the sucking quantity of the air into the furnace is restrained to the min. limit and the absorption of nitrogen into the molten steel 10 is made to the min. In the melting and temp. raising period, gas consisting essentially of CO in the furnace is generated and NOx is generated at the spot part, too. A part of the exhaust gas is sucked and the NOx content in the gas is measured with an NOx meter, and the invasion of the air into the arc spot is detected. |
