Mechanical Properties of Metals - I CHAPTER 6 Mechanical Properties of Metals - I 1 1

Processing of metals & alloys Most metals are first melted in a furnace. Alloying is done if required. Large ingots are then cast. Sheets and plates are then produced from ingots by rolling Wrought alloy products. Products manufactured by hot and cold working the metal from large ingots are called wrought alloy products Channels and other shapes are produced by extrusion. Some small parts can be cast as final product. Example :- Automobile Piston. 2 2

Blast Furnace 3 3

Ingots 4 4

Hot Rolling of Steel Hot rolling Greater reduction of thickness in a single pass. Rolling carried out at above recrystallization temperature. Ingots preheated to about 12000C. Ingots reheated between passes if required. Usually, series of 4 high rolling mills are used. 5 5

Cold Rolling of Metal Sheet Cold rolling is rolling performed below recrystallization temperature. Hot rolled slabs have to be annealed before cold rolling. Series of 4 high rolling mills are usually used. Less reduction of thickness. Needs high power. 6 6

Extrusion A plastic forming process in which a material under high pressure is reduced in cross section by forcing it through an opening in a die.

Extrusion Metal under high pressure is forced through opening in a die. Common Products are cylindrical bar, hollow tubes from copper, aluminum etc. Normally done at high temperature. Indirect extrusion needs less power however has limit on load applied Die Container Metal Direct Extrusion Container Metal indirect Extrusion 8 8

Melt leaving the extrusion die 9 9

Forging Metal, usually hot, is hammered or pressed into desired shape. Types:- Open die: Dies are flat and simple in shape * Example products: Steel shafts Closed die: Dies have upper and lower impresion * Example products: Automobile engine connection rod. Forging increases structural properties, removes porosity and increases homogeneity. Direct Forging Metal Indirect Forging Die 10 10

Basic Shapes for Open -die Forging 11 11

A set of closed forging dies used to produce an automobile connecting rod 12 12

Forging A primary process method for working metals into useful shapes in which the metal is hammered or pressed into shape.

Drawing Wire drawing :- Starting rod or wire is drawn through several drawing dies to reduce diameter. Deep drawing:- Used to shape cup like articles from flats and sheets of metals Change in cross-sectional area % cold work = X 100 Original area Wire or rod Carbide nib 14 14

Wire drawing Wire is pulled from the die

Casting Casting mold Cast parts Casting Process 16 16