How to reduce ladle nozzle clogging during continuous casting

The article explains how to prevent ladle nozzle blockage, what causes ladle spout blockage. Learn how to prevent ladle nozzle blockage and the factors that lead to ladle nozzle blockage.

How to reduce ladle nozzle clogging, as the following:

Preventing ladle nozzle clogging is not successfully completed by one simple action but rather many actions working together: inclusion count reduction, inclusion modification by the use of calcium, protecting from re-oxidation of the steel, proper tundish geometry, and proper tundish and nozzle refractories. While the concept of making only liquid inclusions appears simple in application, it can be rather difficult to maintain these liquid inclusions throughout the entire casting process.

Nozzle clogging during steel pouring in the continuous casting process is a long-standing problem for Al-killed steels. During casting the flow rate of liquid steel through the nozzle is reduced due to the nozzle clogging, which leads to serious operational problems. Even though the ladle slide gate is fully open, the molten steel flow rate can hardly meet the demand of the tundish, causing the level in the tundish to drop. To continue the casting sequence the casting speed must be reduced. In some cases casting is terminated if clogging takes place at early stage of ladle opening and the ladle returns with the remaining steel poured in the EAF/ other ladles for reprocessing or lost as ladle loss. Ladle nozzle clogging reduces productivity, decreases process yield and impacts the steel quality. 

Ladle Nozzle Clogging can be divided into three classes and is grouped according to their sources:

Class 1: Oxide formation :

Category -1.1 by air aspiration, 1.2 by reaction between nozzle refractory and steel.

Class 2: Transportation of oxides to the nozzle wall :

Category – 2.1 deoxidation products, 2.2 reoxidation products, 2.3 exogenous inclusions, 2.4 products of inclusion modification.

Class 3: low temperature chilling of steel

A way to solve ladle nozzle clogging.The concluded that:

The bigger diameter of a nozzle or less nozzle clogging could effectively generate an enough flow rate for a CC process and maintain the target casting speed. We can predict if nozzle clogging is happening by comparing the actual value and the theoretical one of the percentage of a slide gate opened

The main inclusions which caused the nozzle clogging during a CC process of the silicon steel were Al2O3 and its composite inclusions.

Ca-treatment can be a method that transform inclusions into C12A7 by adding Si-Ca wires and prevent nozzle clogging of the silicon steel theoretically. And the amount of Si-Ca wires for Ca-treatment of the silicon steel, with different dissolved Al and total O can be calculated. Ca-treatment can prevent the nozzles from clogging during a CC process of the silicon steel.

Ladle Nozzle Manufacturer

Ladle nozzle clogging during a continuous casting process

To figure out the reason causing ladle nozzle clogging during a continuous casting process for the silicon steel and get away to solve it, the theoretical calculation of flow rates during casting, inclusions around the ladle slide gate where ladle nozzle clogging happened, and Ca-treatment on refining units for producing the silicon steel. 

The bigger diameter of a nozzle or less nozzle clogging can guarantee an enough flow rate for reaching the target casting speed. Ladle nozzle clogging can be predicted by analyzing the percentage of a slide gate being opened. Al2O3 and its composite inclusions were the main ones which cause the nozzle clogging during the CC process of the silicon steel. Ca-treatment could transform those high melting point inclusions into C12A7 by adding Si-Ca wires and prevent the ladle nozzle clogging of the silicon steel.

Due to nozzle clogging, a casting speed often decreased, and even an entire cast would be canceled in severe cases. The transformation of inclusions, electroslag remelting process (ESR for short), and ceramic filters were effective methods to reduce the clogging. And calcium-treatment for transforming inclusions was thought as a lower cost and a simpler process than the others, and thus there were many studies on it for solving the clogging of submerged entry nozzles. 

Some steel with high silicon, such as welding steel, calcium should be not be added into the steel, because it can increase the welding cracks of the steel. That meant that not all steel can use calcium-treatment for solving the clogging, and there has no been a research on ladle nozzle clogging of silicon steel. But there has been being ladle nozzle clogging during CC of silicon steel, which is deoxygenated by using Al. Moreover, silicon steel has unique properties and its processes are more complicated compared to other steel. Therefore, it is necessary to study what causes ladle nozzle clogging for casting silicon steel, figure out a effective method to solve the problem, and confirm that the method would not obviously affect the properties of silicon steel. The theoretical calculation for flow rates that could affect nozzle clogging, analyzed the inclusions causing the ladle nozzle clogging, validated the effects of Ca-treatment on solving ladle nozzle clogging of the silicon steel both theoretically and practically, without a decrease of the magnetic properties.

FAQ:

What is ladle nozzle?

Ladle-nozzle – a type of refractory products used in the process of non-stop casting of steel. They are part of the components of refractories to a steel casting slide gate. They are an integral replaceable part of the nest block.

What is the difference between tundish and ladle?

The tundish allows a reservoir of metal to feed the casting machine while ladles are switched, thus acting as a buffer of hot metal, as well as smoothing out flow, regulating metal feed to the moulds and cleaning the metal.

Which is the connector pipe between tundish and steel ladle?

Shroud Tube Manipulator (Semi-Automatic)

In steel making, the shroud tube creates a connection between the ladle and tundish of the continuous casting plant allowing molten metal to flow between the two.

What are the three nozzle types?

Different types of spray nozzles

Flat Fan Nozzles.

Hollow Cone Nozzles.

Full Cone Nozzles.

Solid Stream Nozzles.

What are the different types of refractory nozzles?

The refractories for continuous casting are mainly classified into the following types: tundish refractories, flow control system refractories and teeming system refractories.

To summarize, read the article to learn how to prevent ladle nozzle blockage and what causes ladle nozzle blockage. Our factory produces ladle nozzle, tundish nozzle and other refractory products. If there is any interest, please feel free to contact us!

Tundish Nozzle Manufacturer