7-8% Apparent Porosity High Temperature Tundish Nozzle for Metallurgical Flow Control

Factors affecting the blockage of the tundish nozzle

Factors affecting the blockage of the tundish nozzle

When the temperature of the molten steel is not high enough or the thermal conductivity of the nozzle material is large, the molten steel is clogged in the pores of the nozzle. During the continuous casting process, the high-melting-point non-metallic inclusions in the molten steel gradually thicken on the inner wall of the nozzle hole, causing blockage. These two reasons may also exist at the same time and cause blockage. Among them, due to the low temperature of the first package of molten steel poured in the tundish and the freezing of the molten steel in the pouring stage caused by the poor baking of the tundish, it is a common reason that the continuous casting machine is forced to stop pouring. Therefore, when casting with a new tundish, in addition to appropriately increasing the temperature of the first furnace steel, the full baking of the tundish is also very important.

Since the alloying elements in the molten steel react chemically with the refractory material to form refractory oxides, which are deposited on the inner wall of the nozzle hole to cause nozzle nodulation, it is also a common cause of nozzle clogging, for example, when casting a vessel with a high aluminum content. In the case of sheet steel or aluminum killed steel, the reaction of aluminum in the molten steel with the refractory material can be expressed by the following chemical reaction formula:

2Al+3/2Si02—Al203+3/2Si

2A1+Fe2O3—Al2O3+2Fe

The reaction product Al2O3 is a fine solid particle which tends to adhere to both the nozzle surface and the molten steel. However, due to the presence of fine pores on the surface of the nozzle, it is easy to adsorb the aluminum oxide inclusions deposited on the nozzle wall. In addition, the secondary oxidation caused by the contact between the molten steel and the air, and the supersaturated precipitation of Al2O3 in the molten steel due to the decrease in the nozzle temperature, etc. Both may accelerate the nodulation of the nozzle and cause blockage.

The inner surface of the nozzle is rough, such as aluminum carbonaceous nozzle. Due to carbon oxidation, the inner surface of the nozzle is rough and corrugated, and the flow of steel is blocked to increase the accumulation of Al2O3.

Application performance of tundish nozzle brick

The faucet brick is a refractory steel water outlet that is embedded in the bottom brick of the steel drum. When the nozzle is not poured, the nozzle brick and the plug brick are in line contact, so as to ensure no steel leakage. The upper mouth of the nozzle brick is curved, which is convenient for opening and closing the nozzle and reducing the resistance of the molten steel flow. The lower section is a straight section to stabilize the flow. When the capacity of the steel drum is constant, the inner diameter of the nozzle brick directly affects the pouring speed.

(1) Sheung Shui. Its position is directly embedded in the brick, and the material is required to be resistant to high temperature, erosion and erosion, so the service life is longer than that of the skateboard. The water inlet is structurally permeable and airtight. The venting nozzle is mostly used in the sliding nozzle of the tundish. Its function is to reduce the clogging of the nozzle and improve the quality of the molten steel. The venting hole is mostly in the form of a porous structure, which can produce uniform bubbles under the premise of reducing the gas volume, and is beneficial to The bubbles float up in the crystallizer. The material is generally made of aluminum carbon, corundum or mullite. In order to improve the performance of the water inlet material, a small amount of Cr2O3 and ZrO2 are sometimes added to improve the corrosion resistance of the nozzle brick. The main factors of the damage of the water inlet are: chemical erosion and erosion of molten steel and molten slag; mechanical damage during installation; damage caused by oxygen cleaning at the nozzle.

(2) Sewer. It is mainly used to control the flow rate and flow rate of molten steel, and it requires good erosion resistance and high temperature volume stability at high temperatures. The material is mainly high alumina, aluminum carbon and aluminum zirconium. The main causes of damage are: erosion and erosion of molten steel, slag, cracking or fracture caused by temperature change, and melting loss caused by oxygenation. In order to improve the thermal shock resistance of the drain, the drain is installed in the iron sleeve to prevent cracking. Try to avoid oxygenation and pouring when using.

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Henan hongtai kiln refractory co., LTD. Main products are high alumina brick, clay brick, fused zirconium corundum brick, fireproof ball lightweight insulation brick, wear-resistant pouring material, corundum pouring material, low cement high strength pouring material, impermeable material, self-flowing material, plastic material, and various types of refractory materials.For different industries, the cement industry with anti-flaking high-alumina bricks, alkali resistant bricks, phosphate bricks;Boiler industry USES all kinds of brand wear-resisting brick, corundum brick, mullite brick and other finalizing materials.The company insists on "product quality is the life, enterprise integrity is the foundation", in the fierce market competition, won many users' trust and praise.The products are sold all over the country, as far as Vietnam, India, Korea, Pakistan, kazakhstan, other southeast Asian countries and regions.

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