Experiment on Dephosphorization of Hot Metal with Converter Slag Pre melting Dephosphorization Agent

With the rapid development of China’s steel industry, the output of converter slag, as a derivative of the steelmaking process, has also significantly increased. The amount of converter slag is generally 15% to 20% of the crude steel production. In 2007, China’s steel production was 489 million tons, and the proportion of converter steel was calculated at 80%.

Therefore, the annual production of converter slag is over 60 million tons. If such huge waste slag cannot be well treated and utilized, it not only causes great waste of resources, but also poses great pressure and harm to environmental protection. Currently, Low comprehensive utilization rate of converter slag in China The utilization rate of steel slag is only 36%, and the level of utilization is relatively backward. Most of it belongs to primary utilization, usually used for road construction, cement production, backfill engineering materials, microcrystalline glass, and return to sintering.

The remaining amount is still discarded as waste and continues to accumulate, and these applications have not fully utilized the value of converter slag, which has serious drawbacks. However, the effective composition of converter slag and the composition of dephosphorization agent for hot sheet metal pretreatment are relatively close, which can be considered Consider using converter slag to replace some of the calcium oxide and iron oxide in the dephosphorization agent, and apply it in the pretreatment of hot metal for dephosphorization.

This not only achieves ideal application value of converter slag, reduces environmental pollution, but also greatly reduces the cost of dephosphorization agent and improves the effectiveness of hot metal pretreatment. Considering the high melting temperature of converter slag and the presence of harmful substances such as P2O5 and SiO2 that are not conducive to the pretreatment and dephosphorization of molten iron, this paper conducted a pre melting treatment of the dephosphorization agent containing converter slag under laboratory conditions.

Based on this, a detailed study was conducted on the dosage of converter slag, the amount of dephosphorization agent added, and the treatment temperature of the pre melting dephosphorization agent containing converter slag.

1、 Experiment

（1） Experimental equipment

The experiment of using pre melted dephosphorization agent containing converter slag for hot metal pretreatment and dephosphorization was conducted in a molybdenum silicide resistance furnace with nitrogen protection (with a maximum temperature of 1600 ℃), as shown in Figure 1. The experimental temperature was selected to be between 1300 and 1400 ℃. Use a corundum crucible with a capacity of 100mL as the experimental crucible, and a graphite crucible (with an inner diameter of 65mm and a height of 120mm) as the protective crucible Φ 6mm quartz tube sampling and stirring.

（2） Experimental materials

The experimental pig iron material is made by mixing electrical pure iron, high-purity graphite powder metallurgy mold, and phosphorous iron according to the listed target components, and melting them in a graphite crucible in a medium frequency induction furnace.
The dephosphorization agent uses iron oxide and Fe2O3, MnO, etc. in converter slag (as shown in Table 2) as oxidants, pure CaO and CaO, MgO in converter slag are analyzed as fixatives, and pure CaF2 is analyzed as flux. The raw materials of each dephosphorization agent are ground and screened until the particle size is less than 0.15mm, and then prepared according to a certain proportion relationship.

（3） Experimental methods

1. Preparation process of pre melted dephosphorization agent containing converter slag
Grind the raw materials to a powder below 0.15mm, mix thoroughly after preparing according to a certain ratio, weigh 100g and load it into a 100mL corundum crucible, and then perform pre melting treatment in a molybdenum silicide resistance furnace to raise the furnace temperature to 1250-130