The Optimization Of Converter Process Of Non-quenched And Tempered N80 Steel For Oil Well Pipe

The thesis is briefly about the analysis and the comparison of the steelmaking process between the converter and the electric arc furnace. Through the comparison, the certain superiority of the converter to the electric arc furnace is shown in most scopes.The inexpensive nitrogen is used instead of the V. N. alloy in the course of adding nitrogen in the molten steel.To produce non-quenched and tempered N80 steel with low cost, the difficulty is how to add the nitrogen and how to control the content of the nitrogen in the molten steel. Nitrogen is harmful to most steel grades, but it is a useful alloying element in the blowing N₂ alloying steel, for example, the N-containing non-quenching and tempering low-alloyed steel. In the present steelmaking process of N-containing steel, nitriding alloy is generally added in the later period of fining to alloy of nitrogen. When the nitrogen is alloying, the rate of effectively using nitrogen is low, and the content of nitrogen is difficult to control. The molten steel is easily contaminated by adding nitriding alloy in the later period of fining. It will largely reduce the production cost using the method of blowing N₂ into the molten steel to alloy of nitrogen.The experimental result proved that the nitrogen content can meet the requirement of the non-quenched and tempered N80 steel, and that the end point value in the molten steel can be controlled by the time and the intensity of blowing nitrogen. Another emphases of the laboratory research is to examine the affection results by several main factors affecting the nitrogen increase in the molten steel. The results showed the following several points. (1) With the increase of the oxygen content in the molten steel, the molten steel's absorption speed of nitrogen is falling. (2) With the increase of the sulfur content in the molten steel, the molten steel's absorption speed of nitrogen is falling. (3) Though, with the increase of the initial nitrogen content in the molten steel, the molten steel's terminal nitrogen content is accordingly becoming higher, the molten steel's absorption speed of nitrogen is falling. (4) As the intensity of blowing N₂ is enhancing, the molten steel's absorption speed of nitrogen is advancing. (5) As the reaction temperature is higher, the molten steel's absorption speed of nitrogen is also advancing.The experimental research has given direction to the practical production process to no-quenched and tempered NS0 steel. From the practice of the practical production, using the craft of bottom blowing nitrogen to add nitrogen content, the nitrogen content can meet the requirement of all kinds of the no-quenched and tempered N80 steel, and can obtain well economic benefits.