What is LRF Process in Steelmaking?

LRF process also know as ladle refining furnace, is a secondary refining technology based on electric arc furnace (EAF) steelmaking.This process aims to further improve steel quality. 

LRF effectively removes impurities such as sulfur from steel through gas blowing and other operations within the ladle, and precisely controls the steel's chemical composition and temperature, thereby producing higher purity and higher quality steel. It plays a crucial role in modern steel production.

LRF Process Flow

LF refining furnaces steelmaking varies depending on the steel mill, furnace type, and target steel grade.

1. Premixing & Steel Preparation

• Introduce molten steel from a secondary steelmaking system such as a converter/electric furnace into the ladle.

• Initial Temperature & Composition Target Setting: Set the target temperature, target ranges for elements such as carbon, silicon, and manganese, and the content of impurities to be removed.

• Initial Degassing Preparation: If necessary, initiate the degassing process in advance to reduce the initial content of gases such as nitrogen and hydrogen.

2. Cooling/Heating & Thermal Equilibrium

• Stabilize the molten steel temperature through gas blowing and heat exchange within the ladle refining furnace.

• If necessary, add appropriate alloying elements (such as Cr, Mo, Ni, V, Nb, Ti, etc.) in the LF refining furnaces for secondary alloying to achieve the composition range of the target steel grade.

• Maintain the molten steel temperature within the allowable range to avoid overheating or undercooling, which could lead to segregation or inclusion redistribution.

3. Blowing, Gas Reaction, and Degassing

• Blowing parameters: blowing time, type of blowing gas, flow rate, blowing location, etc.

• Degassing process: Blowing removes dissolved gases (especially nitrogen, hydrogen, oxygen, etc.) from the molten steel, reducing the gas content and improving toughness and purity.

• Desulfurization/Oxide Control: Reduce the content of S, O, N, and inclusions by controlling the redox conditions during blowing and adding desulfurizing agents or alloying elements.

4. Dehydrogenation, Inclusion Removal, and Control of Titanium, Nitrogen, and Nitride Content

• Low-content targets for nitrogen and hydrogen in molten steel are controlled through blowing conditions and gas strategies.

• Inclusions in molten steel (such as SiO2, Al2O3, etc.) are controlled and their aggregation and flotation are achieved through temperature, chemical reactions, and hydrodynamic conditions.

5. Refining Chemical Composition Control

• Major chemical components (C, Si, Mn, S, P, etc.) are determined online or semi-online and compared with target ranges.

• Trace element supplementation or adjustment (Cr, Mo, Ni, V, Nb, Ti, etc.) is performed as needed during the LRF process to ensure the final composition falls within the required steel grade spectrum.

• Strength, toughness, and formability are adjusted using carbon content and temperature as the main control variables.

6. Temperature & Heat Treatment

• The temperature of molten steel is controlled to ensure that the casting temperature and mechanical operating temperature requirements are met.

• Short-term holding and pre-annealing treatments are performed according to the process requirements of the ladle refining furnace to improve microstructure uniformity.

7. Final Inspection & Tapping

• Final composition and temperature confirmation, meeting the ladle tapping range.

• Final sampling and analysis are performed before transferring the molten steel to the continuous casting or forging system.

• LRF process parameters are recorded for traceability and quality analysis.

Regarding the LF refining furnaces, if you have specific steel grades, target performance requirements, or specific melting furnace type needs, please let us know. Sanrui Electric Furnace is committed to providing more detailed process parameters to every customer.