The order of adding various ferroalloys during steelmaking—once you see it, you’ll be amazed! (III)

The boron recovery rates of the two methods are comparable, typically ranging from 45% to 85%, and may be even higher in certain cases. From the perspective of boron homogeneity in the steel and its intrinsic quality, the latter addition method is preferable.

The main factors affecting titanium recovery rate are:

1) The effect of slag quantity in the furnace. Titanium burn-off is primarily governed by the slag; thus, when the slag volume in the furnace is low, its impact is minimal and the recovery rate remains relatively stable. When the slag quantity is substantial, slag deoxidation is effective, and slag fluidity is appropriate, titanium burn‑off is also low and consistent. Conversely, if the slag volume is excessive and its condition is poor, titanium burn‑off becomes significant and highly unstable. If the slag is too dilute, the interaction between ferrotitanium and the slag intensifies, leading to a decline in recovery; however, if the slag is overly viscous, ferrotitanium tends to float on the slag surface, resulting in increased burn‑off and reduced recovery. Poor slag deoxidation, with high iron oxide content, causes substantial oxidation losses of titanium and lowers the recovery rate. High temperatures—especially elevated slag temperatures—promote ferrotitanium burn‑off and reduce recovery. Moreover, when the steel contains a high titanium content, the recovery rate is correspondingly high; similarly, a higher concentration of other deoxidizing elements in the steel also enhances recovery. For instance, pre‑inserting aluminum–titanium before adding titanium can further improve and stabilize the recovery rate. Adding ferrotitanium directly at the furnace top, leveraging gravity, allows it to enter the molten steel more efficiently, thereby boosting the recovery rate.

2) The effect of titanium iron lump size. As long as it’s not entirely in fragments, it generally isn’t a major factor; however, if it’s in powder form, the recovery rate of ilmenite can drop significantly, sometimes falling below 25%.

3) The effect of the addition method. After slag‑removal operations, titanium‑iron is added: once the slag has been scraped off with an iron rake and the reducing slag in the furnace‑door area has been pushed aside to reveal the exposed molten steel, titanium‑iron is introduced immediately. The recovery rate—particularly for stainless steels—can be maintained at 60%–65%, with relatively little variation due to slag conditions or temperature. For structural steels containing silicon and vanadium, which exhibit a higher degree of deoxidation than stainless steels, the recovery rate can reach approximately 70%.

Electric arc furnace steelmaking uses electrical energy as its heat source, thereby avoiding sulfur contamination of the steel that can arise from gaseous heat sources. The process is highly flexible, allowing both the slag and the furnace atmosphere to be adjusted to either oxidizing or reducing conditions. A strongly reducing atmosphere minimizes the loss of valuable alloying elements—such as chromium, nickel, tungsten, molybdenum, vanadium, and titanium—present in the charge. Moreover, the furnace operates at high temperatures that are easy to control, resulting in superior product quality.