Annealing - Heat Treatment Procedure

    Graversen Hopkins
    By Graversen Hopkins

    Annealing is a heat treatment procedure by which we can make changes to a material by causing changes in its specific properties such as hardness and strength of the material. This process can be implied on the materials such as steel, silver, copper and brass and is performed by considerably heating the material for a specific time period and then it's allowed to cool. The machinability requirements of steel are different and thus, this process is used to enhance the properties of steel to meet the specific requirements. In case of steel, it is heated to 723 degrees Centigrade of temperature, after which it is allowed to cool.

    Stages of the Procedure:

    The process is conducted under three stages:

    1 Recovery Phase
    2 Recrystallization
    3 Grain Growth

    The environment which is required for this process to occur is extremely decisive as during the procedure, the material needs a carbon rich atmosphere facilitating carburization.

    Types of this Heat Treatment Process:

    Various types of this heat treatment process are available:

    1. Process Annealing
    2. Full Annealing
    3. Stress Relief
    4. Isothermal
    5. Spherodise

    The first method of the heat treatment process generally suits for low carbon steel and is mainly passed on cold rolled steel such as wire drawn steel etc. This method tends to improve the characteristics such as ductility and hardness which otherwise makes the process difficult.

    In Heat Treatment Furnaces , the steel involves heating to about 30 to 50 degrees centigrade above a significant temperature of the material. The temperature is then holed for a specified time period and then inside a furnace the material is allowed to cool without any forced ways of cooling. This process can be applied to: castings made from high carbon and medium steels, hot worked sheets and forgings etc.

    The Stress Relief process can be used for large welded structures and castings.
    High carbon and alloy steel uses the Spherodise method and isothermal procedure is mainly appropriate for alloy steels and for low carbon.

    Setup and Equipment:

    For this process of heat treatment, special large ovens are used which are huge enough to store the work piece in the right position in order to get maximum exposure to the heated air in the oven. Special gas fired conveyor furnaces are mainly used for high volume process annealing. Carbon bottom furnaces are used for especially for high quality parts or for large work pieces. Once the process is completed, these work pieces are often quickly cooled.