Manufacturing Processes Rolling and Forging Manufacturing Processes

Outline Temperature Rolling Forging Flat Rolling Shape Rolling Operations Thread Rolling Seamless Tubing and Pipe Rolling Nonmetallic Materials Forging Open-Die Forging Closed-Die Forging Roll Forging Heading Rotary Swaging Forging Machines Dies Economics

Rolling and Forging Rolling The thickness of a slab of a slab or plate is reduced by cylindrical rolls which rotate to pull the material between them and compress it Forging A workpiece is compressed between opposing dies so that the material is forced into the die shape

Temperature in Metal Forming Cold working (room temperature or slightly higher) Warm working (30% - 50% of the melting temperature) Hot working (50% - 75% of the melting temperature) Isothermal forming Tools are preheated to prevent surface cooling during forming

Structure/Property Modification

Cold Working Advantages No heating required Better surface finish Better dimensional accuracy Parts are interchangeable Better strength, fatigue and wear properties Directional properties can be imparted Minimal contamination problems

Cold Working Disadvantages Higher forces required More powerful equipment required Less ductility is available Surfaces must be clean Intermediate anneals may be needed to restore ductility Directional properties may be detrimental May produce undesirable residual stresses

Typical Rolled Products

Typical Rolled Products

Rolling Process

Rolling Process

Rolling Process

Rolling Process

Rolling Process

Example of a Hot Rolling Line

Rolling Defects

Shape Rolling Uses a series of specially shaped rolls to form a beam with a specific cross section (such as an I-beam)

Ring Rolling Uses rolls to form a thick, small-diameter ring into a thin, larger-diameter ring

Ring Rolling

Thread Rolling Uses moving dies with grooves to form threads on cylindrical parts

Thread Rolling

Material Property Changes

Roll Piercing Uses compressive stresses on a cylindrical part to cause tensile forces at the interior, creating a hole to form a thick-walled tube

Example of a Tube Rolling Mill

Rolling Nonmetallic Materials Paper Plastic sheets Rubber products Reinforced fabric Calendering Passes material through a series of gaps between rolls to form a thin sheet

Calendering

Example of a calendered rubber sheet with two layers Calendering Example of a calendered rubber sheet with two layers Courtesy Cooper Tire

Calendering of Rubber

Coated Products

Coating on both sides of reinforcing material Reinforced Materials Coating on both sides of reinforcing material coating material spools comb reinforcing material coating material windup

Example of a polyester-reinforced rubber sheet with fibers exposed Reinforced Materials Example of a polyester-reinforced rubber sheet with fibers exposed Courtesy Cooper Tire

Example of a steel-belted rubber sheet with the belt exposed Reinforced Materials Example of a steel-belted rubber sheet with the belt exposed Courtesy Cooper Tire

Calender Control Systems

Calendering Thickness Sensors Emitter X rays or beta radiation (electrons) some radiation is blocked, depending on thickness Detector

Milling Squeezes material between rolls to mix or preheat it for further processes

Forging Forging A deformation process in which the material is compressed between dies, using impact or gradual pressure to form the part

Forging

Example of a Forging Machine

Example of a Forging Machine

Working Temperature Hot Forging Material is above its recrystallization temperature Cold Forging Increased strength from strain hardening

Forging Billet A piece of material with a square or circular cross section; usually produced by a deformation process such as rolling or extrusion

Open Die Forging Compresses the work between flat or nearly flat dies

Open Die Forging

Open Die Forging

Open Die Forging Advantages Simple, inexpensive dies; wide range of sizes; good strength Limitations Simple shapes only; difficult to hold close tolerances; machining necessary; low production rate; poor utilization of material; high skill required

Closed Die Forging Also called impression-die forging; compresses the material into the shape of the die cavity

Closed Die Forging

Closed Die Forging Advantages Good utilization of material; better properties than open die forging; good dimensional accuracy; high production rate; good reproducibility Limitations High die cost for small quantities; machining often necessary

Roll Forging Uses grooved rolls to reduce thickness and increase length of round or flat bars

Roll Forging

Roll Forging

Roll Forging

Coining Uses dies to press fine detail into both sides of the workpiece

Upsetting/Heading Decreases the length and increases the diameter of the workpiece; often used to form heads on nails, bolts, etc.

Orbital Forging Uses a die that moves in various directions to compress the workpiece

Swaging Uses hammering dies to decrease the diameter of the part

Swaging

Forging Dies and Die Inserts Separate inserts may be used for forging complex shapes; this may be less expensive than a complex single-piece die

Forging Defects

Forging Machines

Forging Machines

Example of a Forging Machine

Economics

Summary Rolling and forging shape parts by deforming the material into the desired shape