steel making: lecture secondary steel making

MY: 301 Steel Making Processes

Secondary Steel Making /Special Steel Making / Clean Steel: For most application, the surface quality, internal quality, micro-

cleanliness quality and mechanical property of the steel produced by primary steel making (open hearth, LD, EAF, BOS etc) are satisfactory and hence these processes meet the specification and the customer’s requirements.

However the quality requirements of special steels in terms of cleanliness, grain size, hardenability range etc have become quite stringent in recent year.

E.g. rotor, special forgings, aircraft and space-craft components, plates for ships and submarines, pipeline, electrical steel and so on.

The secondary steel making is the critical step in the steel production between the primary and the casting.

Some elements are added and some have to be remove during secondary steel making, Several type of furnaces and equipments are used for this purpose.

Each has a specific role to play and their use is selected depending upon the particular requirement of the type of steel being made.

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Secondary Steel Making Operation/Process Varieties:It involves the following options.

1)Stirring treatmentsi. Lanceii. Bottom Pouring Plugiii. Electromagnetic Stirring(EMS)

2)Synthetic Slag Refining with stirring.3)Ladle Furnace4)Decarburisation Techniques

i. Argon-Oxygen-Decarburisation (AOD Process)ii. Vacuum-Oxygen-Decarburisation (VOD Process)

5)Injection Metallurgy (Ladle Injection)i. Powderii. Wire

6)Post-Solidification Treatmenti. Vaccum Arc Remelting (VAR)ii. Electro Slag Remelting (ESR)

7)Vacuum Treatment / Degassing

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1)Ladle Furnace(LF)

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2)Stirring treatments/techniques Ladle Stirring is an essential operation during secondary steel making in order to achieve.

i. Homogenize bath temperature.ii. Homogenize bath composition.iii. Facilitate slag-metal interaction essential for the

processes such as desulfurization iv. Accelerate the removal of inclusion in the steelv. Cleanliness improvement

In practice stirring is achieved byi. Argon/Nitrogen gas bubbling in the refined steel

bath either via a submerged lance or by porous plugs in the bottom of the ladle.

ii. Electromagnetic Stirring (EMS)

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steel making: lecture secondary steel making

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