Converter production - technical measures to be taken for low phosphorus steel:
1. Temperature control:
The molten pool of the converter should be heated evenly. In the middle of the blowing process, the amount of coolant added should be adjusted to control the heating temperature. It is reasonable to control the molten steel temperature at the end of the converter at 1630-1650 °C.
2. Alkalinity control:
In the early stage of smelting, it is necessary to ensure that the basicity of the slag is greater than or equal to 1.7, and it is reasonable to control the basicity of molten steel at the end of the converter to 3.0-4.0.
3. Control of w(FeO) content in slag:
For smelting low carbon steel slag w (FeO) content control between 18% -30% is more favorable for dephosphorization.
4. Slag quantity control:
Generally, 1/3-1/2 slag is reserved, which can facilitate the rapid formation of the slag in the early stage, can improve the basicity of the slag in the early stage, and is conducive to the dephosphorization in the early stage.
5. Control of slag under tapping:
1) The converter produces high basicity slag, and try not to control the slag or reduce the slag. In this way, even if there is a small amount of slag in the converter, the slag can be thickened due to the decrease in the temperature of the molten steel, which reduces the activity of P in the slag.
2) When tapping, add 150-300kg lime to the steel to thicken the slag from the converter, further improve the basicity of the slag, and make up for the change in slag properties caused by system cooling and strong deoxidation.
3) After the slag blocking fails, the amount of argon blowing at the bottom of the ladle should be reduced to weaken the dynamic conditions provided by the outside world. That is to avoid the further melting of the thickened slag, and reduce the diffusion of phosphorus back in the molten steel.
4) After refining, for the heats with a large amount of slag and the slag is obviously thinned, an appropriate amount of lime should be added to thicken the slag to change the slag properties, and then further deoxidation.
6. Reduce the phosphorus increase of the alloy:
Low-cost, low-phosphorus alloys are preferred to minimize the effect of alloys on increasing phosphorus in molten steel. If ferrosilicon is used, the effect is better than that of ferrosilicon.
7. Others:
For ultra-low phosphorus steel, molten iron pre-dephosphorization and out-of-furnace deep dephosphorization technology should be adopted to realize ultra-low phosphorus steel production.