COURSE TITLE : METAL FORMING

(PR-603) LECTURE NOTE

INSTRUCTOR IN- CHARGE: DR. RAJ BALLAV

COURSE TITLE : METAL FORMING (PR-

603) LECTURE NOTE

o The stresses induced during process are greater than the yield strength but less than the fracture strength of the material.

o The type of loading tensile , compressive, bending, shearing or a combination of these.

o The job prepared by this process is economical as the desired shape, size and finish can be obtained without any significant loss of material.

o The forming processes grouped under two broad categories :

1. Cold forming

2. Hot forming

o The typical forming process are :

1. Rolling

2. Forging

3. Drawing

4. Deep drawing

5. Bending

6. Extrusion

DEEP DRAWING

EXTRUSION

TYPE OF ROLLING MILL

ROLLING : o Rolling constitute a group of processes in which

deformation or change in shape of product is brought about by compression between rotating cylindrical rolls.

o Rolling of metals is the most important metal forming process where 95% of production of ferrous and non- ferrous alloys goes through this process.

TWO ROLLING MILL : o This mill consist two rollers.

o Both the rollers rotate in opposite direction for desire movement of work piece.

o Work piece is feed between the rollers which apply a compressive force and tends to plastically deform work piece and convert it into desire shape.

THREE ROLLING MILL :

o This type of rolling mill consist three rollers arrange parallel to each other.

o In this machine the middle roller rotate in opposite direction of other two rollers.

o This machine is used to reduce two times thickness in one pass.

o In this machine, the work piece is feed between bottom and middle roller in one direction and top and middle rollers in opposite direction. This machine can handle two work pieces in single run.

FOUR ROLLING MILL : • These machine consist four rollers (two small and two big).

• Big rollers works as backup rolls and they also rotates in opposite direction with each other and also with contact roller.

• This machine is used for cold rolling where high rigidity required.

CLUSTER ROLLING MILL : • In this type of rolling mill, each of working roller is backup

by two or more of larger backup roller.

• This machine is used for rolling hard material.

FORGING : • Forging is a manufacturing process involving the shaping

of metal using localized compressive forces. • The blows are delivered with a hammer (often a power

hammer) or a die.

• Forging is often classified according to the temperature at which it is performed: cold forging (a type of cold working), warm forging, or hot forging (a type of hot working).

DRAWING : • Drawing is a metalworking process which uses tensile

forces to stretch metal or glass.

• As the metal is drawn (pulled), it stretches thinner, into a desired shape and thickness.

• Drawing is classified in two types: sheet metal drawing and wire, bar, and tube drawing.

DEEP DRAWING • Deep drawing is a sheet metal forming process in which a

sheet metal blank is radially drawn into a forming die by the mechanical action of a punch.

• It is thus a shape transformation process with material retention.

• The process is considered "deep" drawing when the depth of the drawn part exceeds its diameter.

EXTRUSION • Extrusion is a process used to create objects of a

fixed cross-sectional profile. • A material is pushed through a die of the desired cross-

section. • The two main advantages of this process over other

manufacturing processes are its ability to create very complex cross-sections, and to work materials that are brittle.

• It also forms parts with an excellent surface finish.

EXPLOSIVE FORMING : • A shock wave in the fluid medium (normally water) is

generated by explosive.

• Explosive used as source of energy.

• Blank is kept over a die which is kept under water.

• The space between the die and blank is connected to a vacuum pump and evacuated.

• An explosive charge placed at a distance from the upper surface of work piece and still in water is exploded.

• The pressure wave produced in the water deform the blank to the die shape .

• The process is generally used for forming big component.

ELECTROHYDRAULIC FORMING : • Electric discharge in the form of sparks, instead of

explosive can also be used to generate shock wave in fluid.

• An operation using this principle of generating a shock wave is called electrohydraulic forming.

• The characteristics of this process are very similar to those of explosive forming.

• The capacitor bank is charged through the charging ckt subsequently , the switch is closed resulting in a spark within the electrode gap to discharge the capacitors.

• The energy level in this process is lower than that explosive forming.

EXPLOSIVE FORMING

ELECTOHYDRAULIC FORMING

HEAT TREATMENT : Purpose of heat treatment- To improve machinability.

To change or refine grain size.

To relieve the stresses of the metal induced during cold and hot working.

To improve mechanical properties(Tensile strength, Hardness, Ductility, Shock resistance).

To increase resistance to wear heat and corrosion.

To produce a hard surface on a ductile interior.

The most commonly used operation of heat treatment :

Annealing

Normalizing

Hardening

Tempering

Carburizing (case hardening) Cyaniding Nitriding Induction Hardening Flame Hardening ANNEALING: The objective of annealing are: • To soften the metal so that it can be cold worked. • To reduce hardness and improve machinability. • To refine grain size due to phase recrystallization and produce

uniformity. • To increase ductility of metal. • To prepare steel for subsequent heat treatment. • To obtain desired mechanical , physical , electrical and magnetic

property. • To relieve internal stresses . • To produce a desired microstructure.

NORMALIZING: • Normalizing heat treatment is a heat treating process used

to provide uniformity in grain size and microstructure in some steel grades.

• Normalizing is the process of heating a material to a temperature above a critical limit and then cooling in open air.

HARDNING:

• Hardening involves heating of steel, keeping it at an appropriate temperature until all pearlite is transformed into austenite, and then quenching it rapidly in water or oil.

• The temperature at which austentizing rapidly takes place depends upon the carbon content in the steel used.

TEMPERING:

• Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys.

• Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air.

CARBURIZING:

• carburization is a heat treatment process in which iron or steel absorbs carbon while the metal is heated in the presence of a carbon-bearing material, such as charcoal or carbon monoxide. The intent is to make the metal harder. Depending on the amount of time and temperature, the affected area can vary in carbon content.

CYANIDING: • Cyaniding is a case-hardening process that is fast and

efficient. • it is mainly used on low-carbon steels.

NITRIDING: • Nitriding is a case-hardening process in which nitrogen is

introduced into the surface of a ferrous alloy such as steel by holding the metal at a temperature below that at which the crystal structure begins to transform to austenite on heating.

INDUCTION HARDENING: • Induction hardening is a type of surface hardening in which

a metal part is induction-heated and then quenched. • The quenched metal undergoes a martensitic

transformation, increasing the hardness and brittleness of the part.

FLAME HARDENING: • Flame hardening is a common surface hardening method.

Metal surfaces, such as steel, are heated with a high-temperature flame and then quenched.

• The result of flame hardening is a hard surface that is more resistant against wear and corrosion.

FLAME HARDENING FLAME HARDENING

POWDER METALLURGY: • Powder metallurgy is an art of manufacturing commercial

product from the powdered metals and alloys.

• The process consist of compressing the irregularly shaped powdered metal particles in a die of the desired shape of the part to be produced.

• The particle is then heated in an atmosphere controlled furnace at a temperature below the melting point of one or more of the constituents of the powdered metal. this is known as sintering.

• The powdered metallurgy techniques is used

1. For producing parts from certain hard materials or refractory metals which are difficult to work with machine.

2. In fabrication of non ferrous products like alloys of tungsten, carbides etc.