6 kinds of refractory materials for trough tapping structure

The tapping groove is connected to the furnace shell, and its masonry methods include ramming, pouring, bricklaying or comprehensive masonry. The masonry method of the tapping hole is relatively consistent. Generally, tapping bricks of various shapes are used for masonry or a steel pipe in the center, surrounded by high-quality magnesia castables for overall casting, and ceramic tubes with a wall thickness of 25mm and 2 to 3 pieces are also used. It's made of high-grade fused magnesia bricks. 

Usually, after 50 to 70 furnaces are used, the new tapping hole needs to be replaced. When the tapping groove is used for tilting tapping, the main damaged parts are the molten steel line, the slag line, and the bell mouth at the front of the groove. The refractory material is required to have good wear resistance, slag corrosion resistance, and thermal shock resistance. Prevents cracking and minimizes wear.

Foreign electric furnace tapping grooves are generally made of high-alumina, magnesia-aluminum, zirconium, magnesia-carbon, wax stone, etc. or add SiC, Si3N4 and C and oxidants and have a service life of more than 100 times after maintenance and repair. of more than 300 times.

The material of the electric furnace tapping groove

1. Brick steel channel

Japan adopts high-durability CFC-ZRN-15X zirconium brick, which uses pure zircon as the main raw material, supplemented by silicon nitride resistant to molten steel erosion, so that it has good adhesion to molten steel, erosion and erosion of molten slag. The anti-corrosion effect of this brick is more expensive. This brick is built in a 50t electric furnace and has a 1.95m long tapping groove. The life of ordinary steel smelting can reach 300 furnaces. Used for 100t electric furnace, 2.8m long tapping groove, smelting special steel with a life span of 200 furnaces.

In addition, CFC-ZRN-15X semi-zircon bricks are also used, which use pure zircon as the main raw material, and use some high-silicon raw materials at the same time to make it have the properties of semi-zircon bricks, and the price is higher than that of pure zircon and silicon nitride. Bricks are much lower. Used for 40t electric furnace, 0.9m long tapping groove, the life of smelting ordinary steel can reach 300 furnaces.

2. Precast block tapping channel

The use of prefabricated large blocks to build the tapping channel has the smallest brick gap, which is beneficial to prolong the life of the tapping channel, while reducing the construction time. It can be mechanically hoisted and can be used after installation. In the 1980s, prefabricated tapping channels with high alumina and low cement castables were widely used in Japan. The castable uses alumina as the aggregate, silicon carbide and flake graphite as the main raw materials, and adds special ultrafine powder and dispersant.

The 80t electric furnace uses low-cement castables and aluminum-carbon prefabricated blocks to build the tapping grooves, with a service life of 118 furnaces. The original use of resin combined with ramming forming tapping grooves has a service life of only 20 to 40 times.

3. Integral tapping groove

The tapping channel is generally made of unshaped refractory material, which has good integrity, high service life and low cost. The materials used are ramming material using phenolic resin as binder or vibration castable using non-cement as binder, which can generally be prepared and constructed on site.

4. Comprehensive masonry tapping channel

Osaka Kiln Refractory Brick Co., Ltd. of Japan switched to high-pressure pressed Al2O3-C non-fired bricks to build the main part of the tapping channel, and the end of the tapping channel still adopts the original Al2O3-SiO2-C-SiC ramming structure.

The use results show that the service life of the main part of the tapping groove (Al2O3-C quality) is as long as 6 weeks (613 furnaces), and the service life of the end of the tapping groove is about 2 weeks. The overall usage is that the melting loss rate of the Al2O3-C tapping slot is 1/6~1/7 of the original high-alumina tapping slot.

In addition, the Japanese tap channel also uses MgO-C bricks. The MgO-Cr2O3 bricks produced by Osaka Company are used in electric furnace tapping slots due to their high strength at high temperature, good volume stability, corrosion resistance and thermal shock resistance.

5. Compound tapping channel

The tapping channel consists of working layer (magnesium carbon brick MgO≥75%, C≥15%, apparent porosity ≤6%, bulk density ≥2.8g/cm3, normal temperature compressive strength>32MPa) and non-working layer (refractory castable )composition. Non-working layers are assembled with prefabricated blocks.

The composite tapping groove is used in a 5t electric furnace (the actual tapping volume is 18t), the tapping temperature is 1600~1650 ° C, 66 tapping grooves are used, the maximum use is 93 times, the average life is 80 times, and the average erosion rate is 1mm.

The material of the composite tapping groove is reasonable and the cost is low. It can reduce the thermal downtime in synchronization with the age of the furnace, improve the operation rate, and increase the life of the tapping groove by 3 to 4 times compared with the high-aluminum refractory castable.

The assembled and lined overall structure is adopted, which is convenient for storage and transportation.

Al2O3-SiC-C castable tapping groove, used for 5t (tapping volume 10t) electric furnace, with a service life of 121 times, the inner diameter of the tapping groove is 0.3m, the wall thickness is 0.2m, the castable for the whole tapping groove is 1.7t, the groove The bottom permanent lining is bauxite cement refractory concrete (material 0.7t), and the upper working layer of the groove is made of Al203-SiC-C castable (material 1.0t). Erosion, the working surface is smooth after use, it is an ideal castable.

6. Integral tapping channel for low cement castables

Chongqing Special Steel's 10t electric furnace uses an integral tapping slot, and the smelting temperature is as high as 1650~1750℃. No cracks and structural peeling occurred during use, the corrosion rate of the copper groove is 1.8~2.4mm/furnace, and the one-time service life without repair can reach more than 50 furnaces. The tapping groove adopts vibrating forming and feeding in batches. After standing and curing for 24 hours, it is demolded. After demolding, it is naturally cured for more than 48 hours, and the final baking temperature is 600 °C.