What is The Temperature Difference Between Slag and Liquid Metal In a Ladle Furnace?

A ladle furnace, also known as a ladle refining furnace (LF/LRF), is an important secondary refining equipment in modern steelmaking processes. 

It is primarily used to further adjust the composition, control the temperature, and remove inclusions from molten steel after primary refining in a converter or electric arc furnace, to meet the production requirements of high-quality steel grades.

Basic Functions of a Ladle Refining Furnace

1. Heating & Holding
2. Fine-tuning of Composition
3. Desulfurization
4. Removal of Inclusions and Purification of Molten Steel
5. Homogenization of Composition and Temperature

Ladle Furnace: Temperature Difference Between Slag & Liquid Metal

In an LF refining furnace, the temperature difference between the slag and the liquid metal (molten steel) is typically very small, generally controlled within ±20℃, or even close to thermal equilibrium. Specific analysis is as follows:

1. Typical Temperature Range of Molten Steel and Slag

Based on available data:

• Molten Steel Temperature: Typically above 1600℃ (generally 1600～1650℃, possibly higher during refining).
• Liquid steel slag temperature: Approximately 1500℃～1700℃, depending on composition and basicity.

In actual refining processes, the slag covers the surface of the molten steel and comes into full contact with it through electric arc heating and argon blowing agitation, thus quickly reaching thermal equilibrium.

2. Why is the temperature difference so small?

• Good heat conduction: Although steel slag has lower thermal conductivity than metals, its heat transfer efficiency at the interface with molten steel is high in its high-temperature molten state.
• Agitation effect: Bottom-blowing argon gas is often used in ladle refining to promote slag-steel mixing and reduce local temperature differences.
• Process requirements: To ensure efficient metallurgical reactions such as desulfurization and deoxidation, LRF needs to maintain the slag and molten steel temperatures identical; if the slag temperature is too low, it will solidify and form a crust, hindering the reaction; if it is too high, it will exacerbate refractory material erosion.

3. Actual measurements and operational experience: 

In LF/LRF operation, temperature measurement is usually only performed on the molten steel temperature, assuming the slag temperature is basically the same.

Significant teperature differences (e.g., >50℃) often indicate: 

• Slag layer is too thick or has poor fluidity; 
• Uneven heating; 
• Or newly added cold slag material has not melted completely.

The temperature difference between the slag and molten steel in a ladle furnace typically does not exceed 20℃. Under normal refining conditions, this can be considered a state of thermal equilibrium, with temperatures around 1600–1650℃.

This small temperature difference is beneficial for achieving efficient slag-steel reaction while protecting the ladle refractory materials.

For any questions or needs regarding ladle refining furnaces such as LF and LRF smelting equipment, please feel free to contact Sanrui Electric Furnace.

E-mail: alice@srfurnace.com  / Tel: +86 15686041999 (Alice)

E-mail: anna@srfurnace.com  / Whatsapp: +86 159 2955 5868 (Anna)

Website: www.srfurnace.com / www.srmeltingfurnace.com / 

Xi'an Sanrui Electric Furnace