CHANGES IN THE COMPOSITION OF NON-METAL INCLUSIONS AND CONTAMINATION STEEL D DURED BY ALUMINUM

Using optical and electron microscopy methods, the pollution of grade D carbon steel by nonmetallic inclusions in samples taken at the stages of metallurgical redistribution (EAF → LF → VOD → Casting). Metal contamination and chemical composition of non-metallic inclusions are determined. It was shown that deoxidation at the stage of production of the intermediate by aluminum leads to the formation of nonmetallic inclusions of corundum (Al2O3) in the metal melt, the proportion of which in total over all redistributions is 52%. Identification and assessment of contamination by non-metallic inclusions showed that subsequent stages of out-of-furnace treatment lead to a decrease in total pollution by inclusions. After evacuation and addition of Al and SiCa, corundum inclusions acquire a globular shape with a maximum size of not more than 6 μm. During solidification, the total contamination by non-metallic inclusions does not change, however. Contamination with silicate inclusions decreases, and the inclusion of corundum increases. The inclusions of corundum are irregular in shape, the high contamination with the inclusions of corundum is caused by secondary oxidation of aluminum during casting, as well as the ingress of products by overgrowing of the casting nozzle into the solidified continuously cast billet.

Study of Calcium Treatment in Steel Ladles for the Modification of Alumina Inclusions to Avoid Nozzle Clogging during Casting

Presence of non-metallic inclusion deteriorates quality of steel and causes nozzle clogging during casting. Nozzle clogging eventually leads to a disruption of normal casting operations. This happens when solid alumina inclusions get accumulate in the nozzle of submerged entry nozzle (SEN). Therefore, it is required to understand the inclusion characteristics (shape, size and chemistry), which forms during the steelmaking process. Calcium is added in the steel ladle furnace (LF) in the form of CaSi wire to modify inclusions and to desulphurize steel. The range in which all the oxides become liquid and no solid sulphides begin to form is regarded as the "optimum window" or “liquid inclusion window” for calcium treatment. It is a target to obtain this calcium addition window, during calcium addition in the ladle furnace. This window mainly depends on the sulfur and total oxygen contents of the liquid steel bath. In the present study, inclusions characteristics such as volume fraction of inclusions, inclusion rating and EDS analysis of inclusions has been carried out using SEM-EDS. Thermodynamic study is carried out using thermodynamic software FACTSAGE and databases to find out formation of various calcium aluminates and the precipitation of CaS. Results show that liquid inclusion window mainly depends mainly on the sulphur level, total oxygen and aluminum content in the steel. These windows will help in calculation of calcium addition range for optimizing the addition of calcium in the ladle. These nomograms have been validated with actual plant condition to reduce the nozzle clogging during continuous casting.

Numerical Simulation for Fluid Flow of Flow Channel Structure in the Injection-Rolling Nozzle during Polymer Continue Injection Direct Rolling

IRN (injection-rolling nozzle) is the key component of the new Polymer CIDR (Continue Injection Direct Rolling) process, and it has higher requirements than the metal roll-casting nozzle. In order to achieve uniform exit velocity, a new type of structure of the flow channel which is called IRN flow channel structure is designed by combining with the two traditional flow channel characteristics, i.e. the fishtail and coat-hanger flow channel. Then numerical simulation was used to calculate the fluid field in IRN flow channel and analyze 3D flow phenomenon and characteristics. The simulation results show that it has a uniform exit velocity of the IRN flow channel with the value of about 0.06m/s.

Numerical Simulation Research on Wide Casting Nozzle of Twin-Roll Magnesium Alloy

Casting nozzle structure is the decision factor for the formation process of the fluid field of magnesium alloys melt, and the distribution uniformity of the casting nozzle has an important influence on the process stability and the billet quality. In this research, the casting nozzle structures used in producing AZ31 magnesium alloys slab with width of 1500 mm by using horizontal twin-roll continuous casting were taken as research object, and the fluid field of magnesium alloy melt in different casting nozzle structures were simulated, and the influences of the numbers, position, shape and size of the divergent fluid block on the fluid velocity were analyzed. The results show that the fluid velocity distribution obtained by seven divergent fluid blocks were superior to five or three divergent fluid blocks, the streamline divergent fluid blocks were superior to the linear ones, and the small divergent fluid blocks were superior to big ones. At the same time, a new casting nozzle structure was presented, the difference between the maximum and minimum fluid velocity by using the new casting nozzle was 4.69%, and the distribution uniformity of fluid velocity meets the requirement of production.