 Today, we are going to discuss purposes of annealing heat treatment. I am Mr. P. P. Mitragootri working in Mechanical Engineering Department of Valshan Institute of Technology, Solaapur. Outcome of learning for today's session will be to understand the purpose of annealing heat treatment process and student will be able to apply the process for achieving desired outcomes. Now, heat treatment because annealing is one of the heat treatments. So heat treatment is a treatment given to metals and alloys so as to bring change in structure and properties of the steel or any material, thereby we can change the properties of steel and by that we can get desired properties. And there are basically three types of heat treatments. One is annealing heat treatment, second is normalizing heat treatment, and third one is hardening and tempering. Today we are going to focus on purposes of annealing heat treatment. In annealing heat treatment, we have to heat the steel either above a three temperature or in between a one and a three temperature or below a one temperature. That is if we draw the graph of temperature versus time, we will find that this is a three temperature, this is a one temperature. Some of the annealing treatments can be shown like this. Some of the annealing treatments are carried out by heating the steel above a one temperature and few of the annealing treatments are carried out by heating the steel below some critical temperature. And we have to study the purposes of annealing. There are more than seven to eight purposes of annealing and the first and foremost purpose of annealing is to refine grain structure. Now grain structure refinement is required basically when we carry out casting, forging or extruded product, when we produce a casting and if our customer has specified grain size number four, ASTM grain size number four and our due to constraints in casting process, if we are getting the coarse grain structure either grain size of two and half or three, we have to refine the grain structure to satisfy the need of customer. This is also true for forging and in case of extrusion depending upon extrusion ratio, grain size will change and if our extrusion ratio is lower, our grain size will be coarser and our customer may demand finer grain size under such circumstances, extruded product has to be subjected for refinement in grain structure. Second objective of annealing is to recrystallize, to restore the ductility in cold work parts. Cold working is one of the basic processes of manufacture and after cold working, ductility of material is seized and further processing of that component is not possible. So if you want to further process it, you have to restore the ductility and for that restoration of ductility is essential and one of the purposes of annealing is to restore the ductility. Second and foremost important purpose is to relieve the stresses after manufacturing developed in the product, after manufacturing developed in the product and I am giving stress on the word after manufacturing. Suppose you have welded structure or suppose you have forging that you have produced, it may have stresses and you have to reduce the stresses after manufacturing and for that you have to carry out annealing treatment. So before I go for the next purposes, I will pose a question before you that is are we not able to relieve the stresses when we carry out annealing to refine the grain structure and dear students please also give a thought whether stresses will be relieved in an annealing treatment carried out to restore the ductility. So thank you now we will go for the next purpose of annealing and that purpose is to improve electrical and magnetic properties of steel, electrical and magnetic properties of steel. Basically we are considering annealing of steel or heat treatment of steel. So this is the purpose and this is called as recovery. Then next purpose basically annealing is a softening treatment to soften the steel annealing is carried out. Then in many cases especially in hyper eutectoid steels and tool steels we find cementite or carbide network surrounding the grains of pearlite and due to which structure becomes very hard and unmachinable. So to improve the machinability of such hyper eutectoid steel and tool steel we have to carry out annealing. Then many a times when we produce heavy casting containing heavily alloyed elements in it we may find that during solidification there may be heterogeneity of structure developed. In some portion of the casting we may find bulk of alloying elements present and in another part of the casting we may have very little amount of alloying elements present. Such type of heterogeneity developed in the component or casting during manufacturing if we allow to remain it as it is it will create a casting with inferior mechanical properties our casting may fail to provide required services. So we have to homogenize the structure of such steel and for that we have to carry out annealing and one more purpose of annealing which is very important is that to prepare the structure for hardening. Hardening is one of the most important treatment in treatment given to the steel so as not only to improve hardness and strength but to get better mechanical properties that is better combination of strength and toughness after hardening and tempering we can get it. So if we want to bring best set of properties after hardening it is absolutely necessary that the component which is to be hardened must have refined grain structure component must have must be free of stresses and for that it is advisable to carry out annealing treatment to the component which is subjected to hardening so that after hardening and tempering we may get desired set of properties. Now we have studied these eight purposes of annealing and after studying these eight purposes of annealing we have to discuss various types of annealing by which in which we will study which purpose is satisfied by the required annealing process today we will stop here and for further reading material science and metallurgy by Dr. Kodgire metallurgy for engineers by EC Roleson and introduction to physical metallurgy by Avner which is TMH publication dear students hope you have understood the purposes of annealing thank you we will meet again.