What is the Use of LRF in Steelmaking?

 

LRF is a crucial piece of equipment in secondary metallurgy for steelmaking. It is primarily used to refine and temperature-regulate molten steel produced in primary refining furnaces (such as electric arc furnaces and converters) to improve steel quality.

Its main uses can be summarized as: deep refining, precise adjustment, and temperature control of molten steel after primary refining, providing high-quality, homogenized steel for continuous casting.

It is not used for melting metal, but rather for quality improvement and process buffering before casting, meeting the requirements of continuous casting and rolling.

Functions and Uses of LRF

1. Deep Desulfurization & Deoxidation

• Desulfurization: The ladle refining furnaces possesses a highly reducing slag system (high basicity, low oxidizing power), enabling efficient desulfurization, reducing sulfur content to below 0.005%, meeting the extremely low sulfur content requirements of high-quality steels (such as pipeline steel and gear steel).
• Deoxidation: By adding deoxidizers such as aluminum and calcium silicate, and utilizing a reducing atmosphere and slag washing, oxygen in the molten steel is deeply removed, reducing oxide inclusions.

2. Precise Control of Chemical Composition & Microalloying

• Composition Fine-tuning: Various alloys (such as chromium, nickel, molybdenum, vanadium, niobium, etc.) can be precisely added within the LF furnace, adjusting the steel composition to a very narrow target range.
• High Alloy Yield: Adding alloys under a reducing atmosphere and submerged arc heating results in minimal element loss and stable, high yield.

3. Precise Temperature Control & Homogenization

Arc Heating: This is a key advantage of the LF refining furnace. Heating the molten steel through electrodes can:

• Compensate for heat losses from the primary refining furnace to continuous casting.
• Precisely adjust the molten steel temperature to within ±5℃ of the target temperature required for continuous casting.
• Provide thermal energy for processes requiring long refining times (such as desulfurization).

Gas Agitation: Argon gas is blown in through the permeable bricks at the bottom of the ladle, strongly agitating the molten steel and achieving:

• Rapid homogenization of temperature and composition.
• Promote the flotation and removal of inclusions by top slag.
• Accelerate the chemical reaction between steel and slag.

4. Inclusion Morphology Control and Purification

• Slag Washing Refining: 

Utilizing high-basicity, high-reducing refining slag to absorb floating deoxidation products and sulfides.

• Calcium Treatment: 

By feeding calcium wire, high-melting-point Al₂O₃ inclusions are modified into low-melting-point calcium aluminates (12CaO·7Al₂O₃), preventing nozzle blockage and improving the toughness and fatigue properties of the steel.

5. Production Rhythm Buffering and Coordination

• The ladle refining furnaces acts as a flexible buffer station, coordinating the production rhythm between the primary refining furnace and the continuous casting machine.
• In the event of a malfunction in the primary refining furnace or continuous casting machine, molten steel can be held at a suitable temperature within the LF furnace, ensuring continuous operation of the entire production line.

Role in the Process Flow

In the typical short process of "electric arc furnace/converter → LRF furnace → continuous casting," the LF refining furnace undertakes the majority of refining tasks, allowing the primary refining furnace to focus on rapidly melting scrap steel or decarburizing, thus improving overall production efficiency.

The Core Value of Ladle Refining Furnaces

• It achieves deep desulfurization and deoxidation, precisely controls composition, reduces and modifies inclusions, and significantly improves the cleanliness and uniformity of molten steel.
• It provides precise heating and temperature control, supplying molten steel at the correct temperature for continuous casting.
• It buffers and matches the rhythm of upstream and downstream processes, improving the overall production flexibility and efficiency of the steel plant.
• Through alloy fine-tuning within the LRF refining furnace, it increases the yield of expensive alloying elements and reduces costs.

In short, the ladle refining furnaces are the "quality controller" and "rhythm regulator" of the modern steelmaking process. 

It is a key piece of equipment for upgrading ordinary molten steel to high-quality molten steel and an indispensable link in the production of most high-value-added steel products.

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

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

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Xi'an Sanrui Electric Furnace