Basic concepts of forging and detailed is here

forging

1. Forging Forging is the oldest metal working process Production of discrete parts Term forging applied to family of process where deformation is induced by localized compressive force State of stress in the work is primarily uniaxial or multi axial compression Depending upon thermal mode of deformation forging implies (1) hot (2) warm (3) cold (4) isothermal Invariably forging done at hot working temperature Control of metal flow and grain structure enables the forged parts to have goo strength and toughness Forged parts are reliably used in for highly stressed critical application Typical grain flow by three processes Proper control of metal flow enables to produce near net or net shape parts. (little or no secondary operation like machining)

2. Typical application High tensile fasteners Connecting rod Crank shaft Aerospace components Turbine disc Transportation equipment parts Agriculture Spanners and hand tools

3. Common forging processes Open die forging Impression die forging – 1. single impression 2. multi impression Closed die forging Press forging Upset forging

4. Open die forging Features Solid work piece after heating is placed between two flat dies (called plates) and repeated compressive force or blows on the work to induce deformation of desired shape Necessary forming force is attained through mechanical equipment called – press Impact is delivered by mechanical hammers like (i) drop hammer (ii) stem or air hammers (iii) pressure Huge noise and vibration is associated with the process, due to excess energy not absorbed in deformation process. Does not control fully metal flow in open die forging Open die forging is used to orient the plastic flow an minimizes subsequent machining.

5. Shapes commonly forged Bars, slabs, billets Massive turbine blade, shaft of machine turbine Forming convex as concave shape, ring Sizes range from small parts to lengthy shafts

6. Advantages and limitations Advantages Limitations Rough forms produced enables subsequent operation to replace the part geometry Simple, flexible and energy operation with impressive dies Useful for small quantity production Limited to simple shape Difficult to control metal flow Less control over favorable strain flow and metallurgical structure Machining to final shape is necessary Low production rate Relatively poor material utilization Dimensional precision depends on operator skill

7. Impression die forging Workpiece attain the shaping die cavity (impression) Heated work in upset is the die cavity upon striking Hammering causes the metal flow to completely fill the cavity Excess metal in squeezed out around the periphery effectively blocks the formation of additional block Flash formation ensures complete filling of die cavity Higher length to thickness ratio of part, flash is subjected to high pressure Due to greater surface to thickness ratio, flash tools rapidly and it subjects the material in die cavity to high pressure. Encouraging filling of mould cavity

8. Advantages and limitations Advantages Limitations Better material utilization Better properties of the forged parts compared to open die forging High production rate Good reproducibility Fine grains structure upon recrystallization, absence of voids of forged parts provide 20% higher strength/weight ratio High die cost and die setting Removal of flash Equipment expensive Machining operation necessary

9. Applications Connecting rod Crank shaft Crane hock Aerospace turbine blades

10. Closed die forging Metal is deformed in a die cavity that provides total confinement of metal As entire metal is confined within the die cavity, so flash is formed Accurate size of work is required since complete filling of cavity must be assured with no excess metal Accurate positioning is also required along with good die design and control of good lubrication Total elimination of scrap there by material saving between 20 and 45% of starting of material Grain flow that follows the outline of product is in crank or rest or orientation, improving strength, ductility and resistance to impact and fatigue

11. Advantages and limitations Advantages Limitations Flashless forging ensures economical material utilization Good reproductivity of parts Better dimensional and surface finish control Compute filling of metal in the die cavity Ensures net shape production with better surface details Good control of grain flow ensures improved mechanical properties. Rapid production parts High tooling cost Expensive capital investment Skill in die setting

12. Types of closed impression forging Drop forging Press forging Machine forging