Presentation on theme: "Forging Oldest metal working process. History : Sponge iron was heated and beat into a useful implement by hammering with a stone. Now : High powered hammers."— Presentation transcript:
Forging Oldest metal working process. History : Sponge iron was heated and beat into a useful implement by hammering with a stone. Now : High powered hammers and mechanical presses have replaced the arm. Controlled heating and handling of the metal.
Definition Forging is the operation where the metal is heated and then a force is applied to manipulate the metal in such a way that the required final shape is obtained. Note : Forging is generally a hot working operation though cold forging is used sometimes.
Classification : Pressure Applied Forging machines mainly divided into two categories : on the basis of pressure applied. a)A forging machine that applies a impact load is called a forging hammer. b)Other that applies gradual load/pressure is called a forging press.
Classification : Constrained Metal Flow Open Die Forging Impression Die Forging Flash less Forging
Contd… Open Die Forging : The work is compressed between flat (or almost flat) dies, thus allowing the metal to flow without constraint in a lateral direction relative to the die surfaces.
Contd… Impression Die Forging : The die surfaces contains a shape or impression that is imparted to the work during compression, thus constraining metal flow to a significant degree. Note : In impression die forging the flash (extra metal) flows beyond the die impression.
Contd… Flash less Forging : Work is completely constrained within the die and no excess flash is produced.
Open Die Forging Simplest case of open die forging involves compression of cylindrical cross-section between two flat dies. This forging operation is known as upsetting or upset forging, reduces the height of the work and increases its diameter.
Analysis of open die forging Assumption/s : Forging is carried out under ideal conditions of no friction between the work piece and die surfaces, then homogenous deformation occurs and radial flow of metal is uniform throughout the height.
Under ideal conditions, the true strain experienced by the work during the process can be determined by : where h o, h f are starting & ending compression heights in mm.
Contd… The force required to compress the workpart can be given as : F = Y f A, where F = Force in Newton (N), Y f = Flow stress corresponding to strain in MPa, A = X-sectional area of part, mm 2
Contd… Considering the barreling effect as shown in the figure :
Contd… Applying the shape factor to account for D/h ratio and friction : F = K f Y f A, K f = Forging Shape Factor,
Problem no. 1 A cylindrical work part is subjected to upset forging operation. The starting piece is 75 mm in height and 50 mm in diameter. It is reduced to a height of 36 mm. The work material has a flow curve defined by K = 350 MPa and n =0.17. Assume a coefficient of friction of 0.1. determine the force as the process begins, at intermediate height of 62 mm, 49 mm and at the final height of 36 mm. Also, draw the load stoke curve.