How do we chose between annealing and normalizing?

Annealing and normalizing

The choice of process between annealing or normalizing mainly are based on the type of steel, processing technology (cold, hot), parts of the use of performance and economic considerations.

For carbon content wC <0.25% -0.5% mild steel, usually use normalizing instead of annealing. Because normalizing process has the following advantages:

(1) Faster cooling speed can prevent the low carbon steel along the product boundary precipitating the third cementite, thereby enhancing the ability of cold deformation of stampings.

(2) Can improve the hardness of steel, improve the machinability of low carbon steel.

(3) Grain can be refined to improve the strength of mild steel.

For medium carbon steels with a carbon content of wc = 0.25% -0.5%, normalizing may also be used instead of annealing, although normalizing carbon steel with a carbon content close to the upper limit will result in higher hardness, can also be cutted, and lower the cost and high production efficiency.

However, for medium-carbon alloy steels containing alloying elements, the stability of the supercooled austenite is increased due to the alloying elements, so that martensite or bainitic structure can be obtained even with slow cooling. Therefore, If the use of normalizing will make the hardness is high, is not conducive to cutting, it should be completely annealed.

For the carbon content of wc = 0.5% -0.75% carbon steel, the general use of complete annealing, because of the higher carbon steel, the hardness of normalizing is higher than the annealed, thus it is difficult to carry out cutting. Therefore, the use of annealing can reduce hardness, to improve its cutting performance.

For the carbon content of wc = 0.75% or more of carbon steel or tool steel, the general use of ball annealing as a pre-heat treatment. If mesh re-cementite exists, you should first normalizing eliminate.

In addition, from the use of steel performance considerations, if the steel or pieces of  load is small  and performance requirements is not high, you can directly use the normal heat as a final heat treatment to improve the mechanical properties of steel. From the economic point of view, due to the normalizing than annealing short production cycle, easy operation, low process costs. Therefore, under the premise to meeting the use of steel performance and process performance, normalizing should be used as far as possible instead of annealing process.