Some Facts About Annealing
Annealing is a process of heat-treating steel. In this process, the steel is heated very carefully in the austenite area and then it is slowly cooled down. The process produces many derivatives. It is a slow and cool process.
One of the derivatives of this process is sub-critical annealing. The requirement of this process is soaking at a temperature which must be less than the lower conversion line. The approximate value of this is something in between 1,200xF and 1,300xF. This is done till the steel is stabled across the cross-section of the temperature, which is then followed by a slow cooling. The speed of gradual cooling is somewhere in between 5xF/hour to 50xF/hour. The cooling process eats up quite a considerable amount of time. Steel mixed with nickel requires very slow cooling as fast cooling may produce undesired results.
Some of the types of annealing are as follows-
• Bright annealing- In this method, a protective environment is used to prevent oxidation of the steel surface.
• Process annealing- This process requires a temperature which must be near to the less critical line in the iron carbon chart. In certain occasions, it is confused with sub-critical annealing. It is usually done before a major cold job.
• Recrystallisation annealing- This process is confused a many times with sub-critical annealing. It is usually carried out after the cold work to obtain a distinctive grain structure.
The other methods are sub-critical annealing, spheroid annealing, isothermal annealing and full annealing.
