Research And Application Of Converter-smelting Of N80 Oil Well Pipe

This paper reviews the development and current status of micro-alloyed steels in China and abroad. Then it discusses the approach to improve its strength and toughness.By analyzing of kinetics and thermodynamics of nitriding, it is known that when oxygen level is low, the nitriding is controlled by the nitrogen transfer diffusion layer in liquid steel, and oxygen level is high, by the chemical reaction in gas-liquid interface. Actually, in majority steelmaking process, the nitriding is controlled by the nitrogen transfer diffusion layer in liquid steel and the chemical reaction in gas-liquid interface. Chief factor of influence nitriding is temperature, the grain size of material, the component of alloy, gas pressure and purity. While a thermodynamics condition (chemical constitution, temperature, etc.) of the nitriding in liquid steel is steady, the more time of nitrogen flush, the more amount of nitriding.Because of oxidizing atmosphere in converter-smelting, carbon reaction with oxygen is drastic, nitrogen content in liquid steel is lower. Therefore, the nitriding is required. The measures of the nitriding in liquid steel are blowing N₂ and adding nitric-alloy in ladle. Using the nitriding method of adding nitrogenous alloy, the nitrogen content is steady. But the cost is higher. Anshan first steel company produces N80 oil well pipe in converter-smelting with bowing N₂ in ladle, final nitrogen content extent of casting blank is 90ppm≤[N]≤140ppm, and the economic performance is notable.