Various types of rolling mill

 A wide range of rolling mill configurations are available to address a wide range of applications and technical issues in the rolling process.

Mill with two levels of rolling

• A twohigh rolling mill is the most basic type of rollingmill, consisting of two opposed rolls.
• The diameters of the rolls in these mills range from 0.6 to 1.4 metres.
• Reversible or non-reversible two-high configurations are available.
• The rolls in a non-reversing mill always revolve in the same direction, and the work is always fed from the same side.
• The work can be passed through the reversing mill in either direction since the direction of roll rotation can be reversed.
• This allows a sequence of reductions to be produced using the same set of rolls by travelling through the task many times from different directions.
• The downside of the reversing arrangement is the huge angular momentum of big spinning rolls, as well as the associated technological difficulties in reversing the direction.
  

Rolling Mill with Three Levels

• Three rolls are arranged in a vertical column in the three-high configuration, and the direction of rotation of each roll remains constant.
• The work can be run through from either side to create a sequence of reductions by elevating or lowering the strip after each pass.
• Because an elevator mechanism is required to raise and lower the work in a three-high rolling mill, the equipment becomes more complicated.
• Reducing roll diameter has advantages, as numerous of the previous formulae show.
• Fewer roll radius reduces roll-work contact length, resulting in lower forces, torque, and power.

Four-High Rolling Mill

The four-high rolling mill uses two smaller-diameter rolls to contact the work and two backing rolls behind them. Owing to the high roll forces, these smaller rolls would deflect elastically between their end bearings as the work passes through unless the larger backing rolls were used to support them. Cluster Rolling Mill Another roll configuration that allows smaller working rolls against the work is the cluster rolling mill.

Mill with two rollers

• A tandem rolling mill is frequently used to increase throughput rates in standard products. As shown, this setup is made up of a succession of rolling stands.
• A typical tandem rolling mill may have eight or ten stands, each reducing the thickness or refining the shape of the product passing through.
• The difficulty of synchronising the roll speeds at each stand is significant since work velocity rises with each rolling step.
• Continuous casting operations are frequently used to supply modern tandem rolling mills.
• The procedures required to transform initial raw materials into finished products are highly integrated in these settings.
• The removal of soaking pits, the decrease of floor space, and the decrease of manufacturing lead times are all advantages.
• For a mill capable of continuous casting and rolling, these technical advantages translate into financial gains.

ROLLING THREAD DEFORMATION PROCESSES OTHER ROLLING THREAD DEFORMATION PROCESSES

Thread rolling

• Thread rolling is a process that involves rolling cylindrical pieces between two dies to create threads.
• It is the most important commercial process for creating external threaded components in large quantities (e.g., bolts and screws).
  
• Cold working in thread rolling machines is used for the majority of thread rolling operations. Special dies are used in these machines to determine the thread’s size and shape.
• There are two types of dice: (1) flat dies that reciprocate relative to one another and (2) round dies that spin relative to one another to achieve the rolling action.
• Thread rolling has high production rates, up to eight components per second for small bolts and screws.
• These rates are not only higher than thread cutting, but they also have other advantages over machining: (1) improved material use, (2) stronger threads due to work hardening, (3) a smoother surface, and (4) improved fatigue resistance due to compressive stresses induced by rolling.

Rolling Rings

• Ring rolling is a deformation technique that involves rolling a thick-walled ring with a smaller diameter into a thin-walled ring with a bigger diameter.
• The deformed material elongates when the thick-walled ring is crushed, increasing the ring’s diameter.
• Ring rolling is often done as a hot process for larger rings and as a cold procedure for smaller rings.
• Ball and roller bearing races, railroad wheel steel tyres, and rings for pipes, pressure vessels, and rotating machinery are all examples of ring rolling applications.
• The method allows for the rolling of more complex shapes than only rectangular cross sections on the ring walls.
• Ring rolling has various advantages over other ways of producing the identical parts, including cost savings, grain orientation that is optimal for the application, and cold working strength.

Rolling out the gear

• Gear rolling is a cold working technique for creating specific gears.
• These goods are extensively used in the automotive sector.
• Gear rolling is similar to thread rolling in that the deformed characteristics of the cylindrical blank or disc are orientated parallel to the axis (or at an angle in the case of helical gears) rather than spiralling.
• Gear rolling has similar advantages to thread rolling when compared to machining: greater production rates, better strength and fatigue resistance, and less material waste.

Piercing of the Roll

• Ring rolling is a specialised hot working procedure for producing thick-walled tubes with a smooth seam. It uses two opposing rolls and is hence classified as a rolling process. The method is based on the idea that when a solid cylindrical object is crushed along its circumference, it develops significant tensile stresses in the centre. An interior crack forms when compression is high enough.
• This technique is used in roll piercing by the configuration depicted. Two rolls apply compressive loads to a solid cylindrical billet, with their axes positioned at a little angle ( 6°) from the billet’s axis, so that their rotation pulls the billet through the rolls.
• The size and finish of the hole generated by the operation are controlled by a mandrel. This tube-making procedure is also known as rotary tube piercing or Mannesmann procedure.