METAL FORGING PROCESS

METAL FORGING PROCESS 

            metal forming process are used to achieve optmum mechanical properties in the metal . metal working reduces any internal voids or cavities present and thus make the metal dense . the impurities present in the metal also get elongated with the metal also get elongated with the grains and in the process get broaden and dispered througout the metal. this decrease the harmful effect of the impurities and improves the mechanical strength
      forming operation are those in which no cutting of the metal takes place. in these operation only counter of the workpiece is clamped to get the desired product . the stress is applied are below the ultimate strength of the metal . the forming process can be cold working
- Hot working is a forming proves in which woking temp. is above the recrystallization temp. of the material
- Cold working :-
        it is a forming process in which working temp. is below the recrystallisation temp. of the material

@ Forging :-

      forging is the operation wherre the metal is heated and then affose is applied to maniculate the metal in such a way that the required final shape is obtained . it consist essentially of altering the shape and section of a steel specimen by pressing or hammering it at a temp. of order of 1000 degree celcius at which the steel is entirely plastic and will flow under pressure

# Forging process :-

        it may be grouped under two heading :-

- Open die forging :-

        this process is also known as smith forging. this involves heating the stock in the black smiths heart and then heating it over the anvil. open type forging is employed where smaller quantities do not justify the cost of closed impurities die and where sections are so large or so irregular so as to make close impression dies in practical

- Closed or impression dir forging :-

       open die forging is not capable of producing complex shapes to great accuracy . special dies are required to shape complex components to extract sizes of forms fot the purpose closed dies are used . in closed dies cavity or impression are cut in the die block in whichthe metal is form to take its final shape and dimensions. these dies are classified into two groups
* Single impression die :-
     the die contain only one impression or cavity which is the finishing impression
* Multi impression die :-
         this die contain finshing operation and one or more auxillary impression for preliminary

@ Cold and hot forging :-

              the cold forging operation is carried out beelow the crystallisationj temp. by mech. or hydraulic processes . this process is applicable to low carbon and low alloy steels and axis symetric components formed by a combination of exclusion and upset like bonds pins screws and riverts etc are produced by the cold forging techniques
      the hot forging operation is carried out above the crystallisation temp. in this process metals are plastically deformed size or shape by using compressive force applied by the hammer or presses

@ Rolling :-

     the process of rolling consist of pressing  a piece of metal between two revolving cylinders called rolls. these compressed the metal increasing its length and reducing its cross-sectional area. the friction between the surfaces of the rolls and the piece of the metal being enable the rolls the to grip the piece and draw it between them

@ Principle :-

       rolling is a process of possing the hot ingot through two rolls which are rotating in opposite direction at a peripheral speed. the space between the rolls the adjusted to confirm  to the desired thickness of the rolled section an the some is always less than the thickness of ingot being fed . the rolls thus squeeze the passing ingot to reduce its cross section  and increase its length as a result of squeezing the grains are elongated in the direction by rolling and the velocity of material at exit is higher than at the entry . after crossing the stress zone.  the grain start refinning . but this is the case only in hot rolling . in cold rolling day 10 to retain the shape acquired by them during rolling

@ Types of rolling mills :-

        - Two high rolling :-
                   it comprises of two rollers rotating in opposite direction. the direction of rotation of these rollers can be reversed to reduce a big ingot by a two high reversible mill severalk passes are needed
          - Three high rolling mill :-
          this mill consist of three roller mounted one above the other . in this arrangement the top and bottom rollers revolves in a samedirection and the middle work in the opposite direction it eliminate the need of reversing the rolls
           - Four high rolling mills :-
           it consist of 4 rolls two small in size and 2 bigger. the bigger rolls back up up the rolling operation by small rolls . these are commonlly used for both hot and cold rolling of plates and sheets. the operation rolling after slab production rolling after slab production is generally carriedout in four high mills. this tendency of rools to 60 and stock . which is thicker at the centre
- Cluster rolling mill ;-
      the outer two rolls the backup rolls are used for providing the necessary rigidity to the small rolls
- Continous rolling mill :-
           in this type of rolling mill a number of non- reversing to high mills are arrangement in series and material is passed through each rolling mill one after the other, the rolls of each successive mills rotate at a fasrter speed than that of the preseeding in order to accomodate the increasing length of metal piece is being cold