Nozzle Refractory For Continuous Casting System
Nozzle Refractory Description
Nozzle series refractory can be divided into long nozzle, metering nozzle, submerged nozzle and separation ring.
Long Nozzle
Long nozzle is the connection part between steel ladle and tundish. Head end of long nozzle connects to steel ladle down nozzle, bottom end embeds into tundish steel liquid. Long nozzle can keep steel liquid from contacting with air during transferring from ladle to tundish, so steel liquid won’t splash, impurity won’t enter into steel liquid. The working condition suggests that long nozzle should not only endure strong thermal shock, steel liquid scouring and corrosion, but also suffer the corrosion of tundish cover flux. With the increasing requirement on steel quality, protecting casting ratio is continuously growing, so long nozzles using ratio is surging.
Quartz long nozzle is earliest used, which has very low linear expansion rate or nearly no thermal expansion, excellent thermal shock resistance, but it’s corrosion resistance is weak, especially for the casting of special steel such as high Mn steel, the service life is even shorter. With the developing of continuous casting technique, especially the casting of special steel, quartz long nozzle can also have unfavorable effect on steel quality, so new type of alumina carbon long nozzle is developed. Alumina carbon long nozzle’s service life is significantly longer than quartz long nozzle, but alumina carbon long nozzle’s main components are corundum, mullite, graphite and molten quartz, although mullite and quartz can large scale increase thermal shock resistance, the corrosion resistance to Mn steel and other special steel is not very good.
To solve this problem, composite long nozzle is developed, i.e., slag line magnesia carbon material, zirconia carbon material, main body adopts alumina zirconia carbon material, to meet low carbon steel casting needs, inner layer adopts alumina magnesia and Sialon ceramic carbon free material.
In recent years, unshaped long nozzle is also developed. Casting molding method is used to replace isostatic pressing molding for the production of alumina carbon quartz long nozzle and alumina magnesia long nozzle.
Long Nozzle Physiochemical Index
| Item | Alumina carbon long nozzle | Alumina carbon long nozzle | Quartz nozzle | Quartz nozzle | Al2O3-C long nozzle | |
| Main body | Purging ring | |||||
| Al2O3 % | 43.81 | ≥40 | ≥85 | / | / | ≥50 |
| F．C % | 30.65 | ≥27 | / | / | / | ≥25 |
| SiO2 % | / | / | / | ≥99 | ≥99 | / |
| Bulk density g/cm3 | 2.24 | / | / | ≥1.82 | ≥1.84 | / |
| Apparent porosity % | 17 | ≤20 | / | ≤19 | ≤18 | 12~20 |
| Compression strength Mpa | 25.2 | ≥20 | / | ≥40 | ≥40 | ≥15 |
| Rupture strength Mpa | 7.82 | ≥6 | / | / | / | ≥4 |
| Air flow rate L/min | 229 | / | 100 | / | / | / |
| Thermal shock resistance/times | 229 | / | 100 | / | / | / |
| Item | Alumina carbon quartz long nozzle | Alumina magnesia carbon long nozzle | Alumina zirconia carbon long nozzle | Alumina carbon long nozzle | ||
| Main body | Slag line | Main body | Purging part | |||
| Material | Alumina carbon | Alumina carbon | Magnesia carbon | Alumina zirconia carbon | Alumina carbon compound | Alumina carbon compound |
| Al2O3 % | 50 | ≥40 | MgO, 74 | ≥40 | 50 | 90 |
| F．C % | 30 | ≥27 | 25 | ≥27 | 31 | / |
| SiO2 % | 14 | / | / | / | / | / |
| ZrO2 % | / | / | / | 6~10 | / | / |
| Bulk density g/cm3 | 2.50 | 2.38 | 2.40 | ≥2.50 | 2.25 | / |
| Apparent porosity % | 14 | ≤20 | 16 | ≤18 | 17 | / |
| Compression strength Mpa | / | ≥20 | / | ≥20 | 24.4 | / |
| Rupture strength Mpa | / | ≥6 | / | ≥6 | / | / |
| Air flow rate L/min(0.1Mpa) | / | / | / | / | / | 210 |
| Thermal shock resistance/times | / | ≥5 | / | ≥5 | 5 | / |
Metering Nozzle
Metering nozzle is mainly used for the continuous casting of small billet. It is installed at the bottom of tundish. Metering nozzle should not have diameter enlargement or erosion under the strong scouring and corrosion of steel liquid. Inserting metering nozzle’s inner layer is made from zirconia ceramic refractory, which has excellent performance, outer layer is made from high alumina refractory. Inserting metering nozzle’s performance cost ratio is very high, so is popularly used. Integral metering nozzle is made by single type of refractory material, but performance cost ratio is not so high as inserting type metering nozzle. Worthy to be mentioned is that, a lot of steel mills insert pocket bricks and metering nozzles together and form a whole body, which is convenient for construction and safer for production.
To prolong metering nozzle’s service life, zirconia content and zirconia ceramic’s density should be improved. The content of zirconia is raised from 65% to 94%, the density is increased from 3.4g/cm3 to 5.0g/cm3. To improve thermal shock resistance, semi stable zirconia is usually adopted, CaO is used as stabilizer.
Metering Nozzle Physiochemical Index
| Item | DJ-65 | DJ-70 | DJ-75 | DJ-80 | Zirconia metering nozzle | Zirconia metering nozzle | WG-70 | WG-80 |
| Position | Whole body and inner core | Outer layer and pocket block | ||||||
| ZrO2%≥ | 65 | 70 | 75 | 80 | 90 | 94 | / | / |
| Al2O3 % | / | / | / | / | / | / | ≥70 | ≥80 |
| Apparent porosity% ≤ | 20 | 21 | 21 | 22 | 22 | 23 | 19 | 19 |
| Bulk densityg/cm3≥ | 3.70 | 3.75 | 3.90 | 4.10 | 4.30 | 4.50 | 2.60 | 2.80 |
