High Quality Ks Sncm220 Steel Lf Refining Process - China

KS SNCM220 steel belongs to the nickel-chromium-molybdenu m low-alloy structural steel family, corresponding to the American standard 8620 steel and the Chinese standard 20CrNiMo steel.

The core objective of its LF refining is to reduce the content of impurities such as sulfur and oxygen, precisely fine-tune the alloy composition of nickel, chromium, and molybdenum, and reduce non-metallic inclusions.

This is to match the strength and toughness requirements of key components such as gears and drive shafts.

The specific process is as follows: 1 - Preparation before refining - Steel pretreatment: The KS SNCM220 steel molten steel after primary refining is transferred to a ladle.

It undergoes bottom-blowing argon pretreatment to remove surface slag.

Simultaneously, rapid temperature measurement and sampling are performed to determine the initial temperature, oxygen content, and initial contents of alloying elements such as nickel, chromium, and molybdenum, providing a basis for setting subsequent refining parameters.

- Material and Equipment Inspection: Prepare high-basicity synthetic slag, lime, aluminum granules, calcium silicate wire, and other slag materials and deoxidizers, as well as alloy materials such as ferronickel, ferrochrome, and ferromolybdenum, ensuring the composition meets the required proportions.

2 - Slag Formation and Preliminary Deoxidation - After the molten steel is transferred to the refining station, synthetic submerged arc slag is first added to the ladle, controlling the slag layer thickness to approximately 75mm.

Then, the electrodes are lowered to ignite the arc and heat the ladle.

- During this stage, a high-basicity (CaO/SiO₂ ratio of 3-5) reducing white slag needs to be formed, with the slag amount controlled at 3%-7% of the molten steel mass.

Simultaneously, aluminum granules are added in batches at 0.2-0.5 kg/t of steel to achieve preliminary precipitation deoxidation.

The purity of the aluminum granules must be >99.0%, with a particle size of 0.5-1.0mm, to avoid leaving a large amount of deoxidation inclusions.

3 - Heating and Enhanced Refining - Submerged Arc Heating Temperature Control: A graphite electrode submerged arc heating method is used, inserting the electrode into the slag layer for heating.

This reduces heat radiation loss and allows CO to be generated through the reaction of the electrode with oxides in the slag, enhancing the reducing atmosphere within the furnace.

- Argon Gas Stirring Optimization: The argon gas flow rate is adjusted according to the refining stage.

Medium-intensity stirring is used during the slag-forming period to ensure sufficient contact between slag and steel; the flow rate is appropriately reduced during the heating stage to prevent molten steel splashing.

4 - Fine-tuning of Alloy Composition - After the slag forms a stable white slag and the molten steel temperature stabilizes, alloy materials are precisely added according to the target composition.

Ferronickel and ferrochrome are added first, as these alloys are easily dissolved and have stable recovery rates; ferromolybdenum is added last, as its higher melting point reduces burn-off due to delayed addition.

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• Posted By: Dongguan Songshun Mould Steel Co., Ltd.

• Phone: 076985475596

• Address: 1st Floor, No. 1, Dongda Fourth Street, Shatou Community, Chang'an Town, Dongguan , Guangdong , China

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• Website: https://songshunsteel.com/

• Business Description: Established in 2009,Songshun Steel supplies a wide range of carbon, alloy and tool steel products, including high speed tool steel, cold work tool steel, hot work tool steel, plastic mould steel, engineering steel and machine structural steel etc.
  
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