(MT 207) B.Sc (ENGINEERING) LEVEL 2 (Semester 2) METAL FORMING (MT 207) B.Sc (ENGINEERING) LEVEL 2 (Semester 2)

Introduction The production of particular products include many stages starting from, Design Manufacturing Storing Sale Out of these processes manufacturing process is the most important process for the materials engineer. The manufacturing process is defined as “ The making of goods and articles by hand or, especially by machinery, often on large scale and division of labor.”

Change the material character Create the form Change the form Change the material character Primary shaping Retain the mass Constant material amount Reduce the mass Reduction in material amount Increase the mass Increase in materials amount Change the mechanical properties -Metal casting -Powder metallurgy -investment -die & centrifugal casting Metal forming -forging -drawing -rolling -bending etc. Metal cutting -turning -drilling -milling -grinding etc. Joining -welding -brazing -adhesive etc. Surface coating -painting -plating -powder coating -Heat treatment -Mechanical working -hardening -tempering -nitriding etc. -Work harden.

In this lecture series we consider about the Metal Forming & Machining Processes. In metal forming processes the volume of the work piece is kept constant & mainly the geometrical dimensions will be changed. (deform the metal plastically) In the machining process the mass of the work piece is reduced by removing (also plastically deformed) the substance using a tool. Note: During plastic deformation of a metal naturally the mechanical properties will also be changed (therefore proper control of process parameters are needed )

During this plastic forming process, volume & mass of the metal are displaced from one place to another, the deformation zone is concerned with a distribution of; Overall stress required to perform the deformation Local stresses strain strain Particle velocity Pictures of metal forming processes

It is important that the overall pressure (needed for deformation) Must develop yielding Must not develop local facture (strain hardening effect) Must create optimum flow stress which is again a function of; Strain Strain rate Temperature of the working piece Note: the work piece also contact with non deforming (only elastically deform) tool or die.

Because of the interaction between tool/die & work piece create; Friction – unnecessary energy loss, high wear rate of the tools. Temperature increase due to friction –unnecessary energy loss, change of process parameter. Wear of the die & work piece interface – difficult to maintain tolerance, cost for the tools.

Classification of metal forming processes………….. Bulk forming The whole volume of the work piece is deformed. Sheet forming Only localized plastic deformation typically change in sheet thickness. (responsible forces are tensile, shear, & bending)

Bulk forming divided into two categories. Direct compression type Primary apply load compressive. Directly responsible for the deformation. Material flow is perpendicular to the direction of compression. Indirect compression type Primary apply load compressive or tensile Indirect compressive force will create a combined stress state. (makes the plastic deformation ) Wire drawing, extrusion, deep drawing, etc.

Classification of metal forming process:

Mechanical aspect of metal forming…………….. It is important to control the mechanical properties during metal working process. Mechanical properties depend up on; Type of metal working process Process temperature Strain rate

Required force to deform the metal is influenced by; Homogeneous deformation (theoretical deformation) Inhomogeneous deformation (occurs in complex stress conditions it is difficult to calculate using conventional theories) Friction at work piece/tool interface

forging In this method metal will be worked into a useful shape by hammering or pressing. Most forging operations are carried out at high temperatures (hot working). Cold working can also be done some materials. Open die forging – allows free deformation of at least one direction. Thereby dies are either flat or having simple shape Impression die forging – complex with great accuracy cannot be forged by open die forging. Specially prepared dies are used. It is important to use enough metal in a forging billet. So that die cavity will be completely filled. Excess material known as “Flash” Close die forging –

Rolling Flat rolling Shape rolling Process of plastically deforming metal by Passing it between rolls is known as rolling. Work piece is subjected to a high compressive stress as a result of friction between rollers & work piece. Flat rolling Shape rolling

What happen in rolling? .X N - Neutral point X - Entrance point N. .X V0 Vf V0<Vf At the neutral point speed of the rollers & the work piece is equal. A to N speed of the work piece is lower than the rollers. A to N friction force acting along the rollers rotating direction & this force led the work piece into the rollers.

Rolling load (P) P = σ0b√R∆h b – sheet width R – radius of the rollers ∆h – h0 - hr