PROCESSES : HOT WORKING AND COLD WORKING PROCESES

   

    
      HOT WORKING AND COLD WORKING PROCESSES

       1) COLD WORKING PROCESS :

                                                   Working of alloys or metals below the re-crystallization temperature is called as cold working process, note that the re-crystallization temperature range for alloys and metals may 340°c to 400°c and 400°c to 700°c respectively.in cold working process the grains of the material is twisted or destroyed.
                              The tensile strength and hardness of the material is increases by cold working process. The main advantage of hot working process is to control dimensions under tolerance. No formation of crystals during process   Surface finish in cold working process is good, cost required for cold working process less as compared to hot working process. This process required more force as compared to hot working process.

      Some of process of cold working shown below,

1    ACold Rolling Process :
          
           Pic01


                                     This process in which the sheet metal is squeezed between rollers. This process increase the yield and hardness of the material.

    Advantages :
                              I) Fast speed of material forming
                             II) Produced large plastic deformation.
                            III) Improve yield

       B) Bending Process : 

           Pic02



                                    Bending is the process in which the V shape, U shape or any required shape of material so the bending process is change the shape of the material as per requirement but volume is remain same.
  
 Advantages :
                           I) We can make shape of the material as per requirement.
                          II) Cost effective process.

      C) Wire Drawing Process :

           Pic03


                                                   Wire drawing process is differed from other processes by reducing the cross section of the wire by single or multiple dieses. This process find their application in many areas. The wire is pulled through die and cross section of wire is reduces.

Advantages :  
                                                                                                           I) Provide require shape of the material as per requirement.
                 II) Improving tensile strength of the material


   2) HOT WORKING PROCESS :

                                     working of alloys or metals above the re-crystallization temperature is called as hot working process. In hot working process the micro-structure of material shows refine grains.
                              The energy required for deformation of material less because at high temperature as result the material becomes soft by . The main disadvantage in this process is due to oxidation at high temperature due to which the surface finish is not good, cost required for hot working process high as compared to cold working process. The lower limit of hot working temperature determine by re-crystallization temperature main point in hot working process is maintaining the temperature of the material.

                 Shown below some of hot working processes,

1   A) Hot  Rolling Process:
             
           Pic04



                                        As per discuss above the  material is heated above the re-crystallization temperature in operation By this process we can make required dimensions and geometry of objects with same volume of metal . Large number of industries is making the hot rolled steel and row material for different application and operation.

    Advantages :

              I) Improve ductility, formability and weldability                 II) Increase toughness and strength of the material.
                            
     B) Extrusion process :
         
         Pic05



                                         The specific fixed cross section of objects create by extrusion process.in other words the process in which forcing the material in preshaped die to create the required shape of objects.

    Advantages :

      I) Many types of row material used in extrusion process.
     II) Good surface finish of formed material by this process.

     C) Forging process :
        
           Pic06



                                The object formed by comprehensive forces with required shape is called forging. Different types of forging processes used as per requirement. With help of die or power hammer the desire shape of object is formed by forging process.

    Advantages :

         I) The product formed by forging is stronger.
        II) Improve mechanical properties & impact resistance.





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