Continuous Casting Process
Introduction to Continuous Casting Process
In this section, the lecturer introduces the continuous casting process and its history. The process is used to cast long ingots, square billets, and complex sectioned components.
Continuous Casting Process
- Continuous casting was first conceived by December in 1958 and gained popularity in the 1960s.
- The process involves pouring molten metal from a ladle into a tundish (reservoir).
- The molten metal then passes through a water-cooled mold where it solidifies.
- Rollers are used to move the solidifying metal along the mold.
- Once fully solidified, the metal is cut using a torch or saw to create finished slabs of various shapes.
Classification of Continuous Casting Process
This section discusses the classification of continuous casting processes based on their orientation.
Types of Continuous Casting Processes
- Vertical Continuous Casting:
- Sub-classified into vertical downwards continuous casting and vertical upward continuous casting.
- Vertical downwards continuous casting involves solidified billets or bars traveling downwards.
- Vertical upwards continuous casting involves solidified bars moving upwards for faster manufacturing of thin bars or wires.
- Curved Continuous Casting
- Horizontal Continuous Casting
- Strip Continuous Casting
Vertical Downwards Continuous Casting
This section focuses on vertical downwards continuous casting, explaining its principle and applications.
Principle of Vertical Downwards Continuous Casting
- Molten metal from a ladle is poured into a tundish.
- The molten metal flows through a graphite mold with cooling systems and crystallizers.
- As it moves down, rollers support its movement until it fully solidifies.
- Periodic cutting of the solidified bar occurs, and the cut bars are further processed.
Applications of Vertical Downwards Continuous Casting
- Used for manufacturing copper, brass, and bronze bars, tubes, and sections.
Vertical Upward Continuous Casting
This section discusses vertical upward continuous casting as a method for faster manufacturing of thin bars or wires.
Principle of Vertical Upward Continuous Casting
- Molten metal is poured from a ladle into a tundish.
- The metal passes through a graphite mold and solidifies with cooling systems and crystallizers.
- Rollers support the upward movement of the solidified bar.
- Periodic cutting occurs to obtain desired lengths.
Advantages and Applications of Vertical Upward Continuous Casting
- Higher casting speed compared to other methods.
- Better physical properties of alloys produced.
- Applied for casting bronze components with smaller diameters (8 to 30 millimeters).
The transcript is already in English.
Vertical Downward Continuous Casting
This section discusses the process of vertical downward continuous casting, where molten metal is poured downwards into a mold and solidifies as it passes through.
Principle of Vertical Downward Continuous Casting
- Molten metal is poured downwards into a mold.
- The metal does not bend or curve during the process.
- Solidification occurs as the metal passes through the mold.
- Cooling systems are used to facilitate solidification.
- The solidified bar is cut at desired intervals.
Curved Continuous Casting
This section explains curved continuous casting, where molten metal takes a curved path before becoming horizontal and solidifying.
Principle of Curved Continuous Casting
- Molten steel is poured into a ladle.
- The steel flows from the ladle to a tundish (local reservoir).
- The steel then passes through a curved mold, taking a horizontal shape.
- Cooling systems aid in solidification.
- The solidified bar is cut at desired positions.
Horizontal Continuous Casting
This section describes horizontal continuous casting, where the solidified bar moves horizontally throughout the process.
Principle of Horizontal Continuous Casting
- Molten metal flows from furnaces to a ladle and then to a tundish.
- The metal passes through a graphite mold and undergoes crystallization and solidification.
- Secondary cooling further facilitates solidification.
- Roller supports pull the solidified bar away from the mold.
- The bar is cut at equal intervals or desired locations.
Applications of Horizontal Continuous Casting
- Thin wires, rods, tubes, strips, and custom sections can be produced using horizontal continuous casting.
- Nonferrous alloys like copper alloys are commonly cast using this method.
Strip Continuous Casting
This section discusses strip continuous casting, which is used to produce thin and wide strips.
Principle of Strip Continuous Casting
- Molten metal is transferred from a furnace to a tundish.
- The metal passes through rollers with a cooling system, solidifying into a thin strip.
- The casting rate ranges from 0.5 to 10 meters per minute.
- Maximum width of the cast slab is 1.75 meters.
- Slab gauge (thickness) ranges from 10 to 40 millimeters.
Applications of Strip Continuous Casting
- Strip continuous casting is used to produce bars, tubes, and maximum diameter strips up to 40 centimeters.
The transcript was provided in English language.
Casting Process and Advantages of Continuous Casting
This section discusses the advantages of continuous casting in terms of casting yield, cost-effectiveness, surface finish, grain structure regulation, and labor requirements.
Advantages of Continuous Casting
- Continuous casting provides a 100% casting yield, meaning that the weight of the casting is equal to the weight of the poured metal.
- It is cheaper to produce ingots through continuous casting compared to rolling.
- Continuous casting results in good surface finish and allows for regulation of grain structure.
- The process is automatic and requires less labor.
Applications of Continuous Casting
- Long billets with various cross sections can be obtained through continuous casting.
- Solid and hollow ingots can be produced using continuous casting.
- Bushing and pump gears can be produced through this process.
- Copper bars or wires can be easily and economically produced using continuous casting.
Advances in Continuous Casting: Electromagnetic Stirring
This section focuses on the advances in continuous casting, specifically electromagnetic stirring (EMS), which improves product quality and production efficiency.
Electromagnetic Stirring (EMS)
- EMS involves generating a rotating magnetic field inside the steel during continuous casting.
- Eddy currents are produced within the molten metal due to the rotating magnetic field, resulting in Lorentz force and subsequent rotation inside the metal.
- EMS promotes the formation of an equiaxed crystallitic zone in the strand, leading to better mechanical properties.
- Grain refinement and reduction in the content of inclusions are achieved through EMS.
- EMS minimizes surface and sub-surface cracks, reduces pinhole and blowhole defects, and helps reduce centerline segregation.
- EMS also aids in reducing breakouts during the solidification process.
The transcript is already in English, so there is no need to respond with the language.
New Section
This section discusses the different zones of electromagnetic stirring (EMS) in continuous casting and their advantages.
Mould EMS (MEMS)
- MEMS is installed in the lower part of the mould for stirring the liquid steel.
- It can be round or square in design and can be installed internally or externally.
- Advantages of MEMS include reduction of pinholes, center porosity, and segregation in the cast product. It also improves solidification structure, reduces surface roughness, and increases heat delivery rate.
Secondary Cooling Zone EMS (SEM)
- SEM produces a stirring force that pushes the liquid steel horizontally along the cast product width.
- It is usually used in combination with MEMS.
- Advantages of SEM include promoting equiaxed structure, grain refinement, reducing shrinkage cavity center segregation and internal cracks, and effective removal of superheat.
Final Solidification Zone EMS (FEM)
- FEM is generally installed in combination with MEMS or SEM to reduce peaks in central carbon segregation.
- It is particularly efficient when casting high carbon or high alloy steel grades.
- Advantages of FEM include reducing shrinkage and central carbon segregation, improving secondary dendrite arm spacing and central equiaxed grains resulting in finer grains.
New Section
This section covers common mould fluxes used in continuous casting and their functions.
Common Mould Fluxes
- Mould fluxes are synthetic slags composed of oxides, minerals, and carbonaceous materials.
- They can be added manually or automatically through the top of the mould on the liquid steel.
- Common fluxes include silicon dioxide, calcium oxide, sodium oxide, lithium oxide, and titanium dioxide.
Functions of Mould Fluxes
- Thermal insulation: Provides thermal insulation to prevent heat wastage and solidification before desired.
- Prevention of reoxidation: Prevents oxidation and reoxidation of the liquid steel.
- Entrapment of inclusions: Traps inclusions present in the liquid steel.
- Lubrication: Acts as a lubricant between the solidified shell and the mould, preventing sticking and breaking.
- Control of heat transfer rate: Regulates the solidification process at the required place and time.
New Section
This section discusses continuous casting defects.
Continuous Casting Defects
- Various defects can occur during continuous casting.
- Some common defects include surface cracks, internal cracks, centerline segregation, porosity, and misruns.
- Defects can be caused by improper process parameters, equipment issues, or material-related factors.
The transcript does not provide further details on each defect or their causes.
New Section
This section provides an overview of how mould fluxes are added in continuous casting and their functions.
Addition of Mould Fluxes
- Mould fluxes are added manually or automatically through the top of the mould on the liquid steel.
- They can be added in the tundish where molten metal is poured from the furnace or ladle just above it.
Functions of Mould Fluxes
- Thermal insulation: Provides thermal insulation to prevent heat wastage and premature solidification.
- Prevention of reoxidation: Prevents oxidation and reoxidation reactions in the liquid steel.
- Entrapment of inclusions: Traps undesirable inclusions present in the liquid steel.
- Lubrication: Acts as a lubricant between the solidified shell and the mould to prevent sticking and breaking.
- Control of heat transfer rate: Regulates the solidification process at the desired place and time.
The transcript does not provide further details on the specific types of mould fluxes used or their compositions.
New Section
This section discusses the importance of understanding and controlling defects in continuous casting.
Common Continuous Casting Defects
- Sticking of the fluxes: The shell sticks to the mold, causing damage to the shell.
- Slag entrapment: Slag is not properly removed from the molten metal, leading to discontinuities in the cast billet.
- Longitudinal cracks: Uneven heat removal, turbulent flow of metal, meniscus level variation, secondary cooling, high casting temperature, and inappropriate behavior of casting powder can cause longitudinal cracks.
- Transverse cracks: Thermal stresses due to uneven solidification of the crust, meniscus level variation, and friction of the strand in the mold contribute to transverse crack formation.
- Star cracks: Intense local cooling and presence of copper at austenitic grain limit result in star-shaped cracks.
- Longitudinal depressions: Unequal development of marginal crust, steel level fluctuation in the mold, excessive metal flux between mold wall and strand space, turbulent steel flow at sub-meniscus level, and uneven wear of the mold cause longitudinal depressions.
- Transverse depressions: Formed in transverse directions and may cyclically occur along with oscillation marks. Peritectic steels with low carbon content and high manganese content are sensitive to this defect.
- Blowholes: Arise due to insufficient steel deoxidation, presence of gases (hydrogen, nitrogen, oxygen), humidity and quality of casting powder, variation of steel level in mold, moisture in refractory lining of tundish, or presence of argon during injection.
New Section
This section continues discussing common continuous casting defects.
Blowholes
- Insufficient steel deoxidation
- Presence of gases (hydrogen, nitrogen, oxygen)
- Humidity and quality of casting powder
- Variation of steel level in the mold
- Moisture in refractory lining of tundish
- Presence of argon during injection
New Section
This section covers longitudinal depressions, transverse depressions, and blowholes.
Longitudinal Depressions
- Unequal development of marginal crust
- Steel level fluctuation in the mold
- Excessive metal flux between mold wall and strand space
- Turbulent steel flow at sub-meniscus level
- Uneven wear of the mold
Transverse Depressions
- Formed in transverse directions and may cyclically occur along with oscillation marks.
- Peritectic steels with low carbon content and high manganese content are sensitive to this defect.
Blowholes (Continued)
- Insufficient steel deoxidation
- Presence of gases (hydrogen, nitrogen, oxygen)
- Humidity and quality of casting powder
- Variation of steel level in the mold
- Moisture in refractory lining of tundish
- Presence of argon during injection
Defects in Continuous Casting Process
This section discusses two common defects in the continuous casting process: interruption and shrinkage cavity.
Interruption in Physical Continuity
- Interruption is an ah physical interruption in the physical continuity of the bar.
- Causes of interruption include high casting temperature, high extraction speed, and intense secondary cooling.
- Shortening the bar that contains the interruption can remove it.
Shrinkage Cavity
- Shrinkage cavity represents a gap of material visible in the cross-section at the end of a bar.
- Causes of shrinkage cavity include high casting temperature, high extraction speed, and intense secondary cooling.
- Shrinkage cavity can be removed by cutting off the end of the bar and rejecting the defective portion.
Important Terms in Continuous Casting
This section introduces important terms related to continuous casting: liquid steel transfer, tundish overview, and mold.
Liquid Steel Transfer
- Two steps involved in transferring liquid steel from ladle to molds: ladle to tundish and tundish to mold.
Tundish Overview
- Tundish is a local reservoir that accommodates molten metal before sending it through the mold.
- The shape of the tundish is typically rectangular or delta-shaped.
- Functions of tundish include enhancing oxide inclusion separation, providing continuous flow during ladle exchanges, maintaining steady metal height above nozzles for constant steel flow and casting speed, and providing stable stream patterns to molds.
Mold
- The main function of the mold is to establish a solid shell sufficient in strength to contain its liquid core.
- The mold is an open-ended box structure with a water-cooled lining made from a high purity copper alloy.
- The working surface of the copper face is often plated with chromium or nickel to provide a harder working surface.
- Mold oscillation is necessary to minimize friction and sticking of the solidifying shell and prevent liquid steel breakouts.
- Oscillation can be achieved hydraulically or via motor-driven cams or levers.
- Mould lubricants such as oils or powdered fluxes are used to reduce friction between the shell and mold.
Types of Continuous Casting Process
This section discusses the different types of continuous casting processes: vertical continuous casting (downwards and upwards) and strip continuous casting.
Vertical Continuous Casting
- Divided into vertical downwards continuous casting and vertical upwards continuous casting.
Strip Continuous Casting
- Another type of continuous casting process, but no further details provided in the transcript.
Electromagnetic Stirring in Continuous Casting
This section introduces electromagnetic stirring (EMS) applications in continuous casting: mold EMS, secondary cooling zone EMS, and final solidification zone EMS.
Mold EMS
- First type of EMS application in continuous casting.
- No further details provided in the transcript.
Secondary Cooling Zone EMS
- Second type of EMS application in continuous casting.
- No further details provided in the transcript.
Final Solidification Zone EMS
- Third type of EMS application in continuous casting.
- No further details provided in the transcript.