Re-crystallization Annealing

Re-crystallization Annealing:

• The process consists of heating steel above the recrystallization temperature, holding at this temperature and cooling thereafter. 
• It is used to treat work hardened parts made out of low carbon steels (< 0.25%) carbon). This allows the parts to be soft enough to undergo further cold working without fracturing. 
  
• Re-crystallization temp (T_r) is given by T_r = (0.3-0.5)T_mp 
• As little scaling and de-carburization occurs in re-crystallization annealing, it is preferred over full annealing 
• No phase change takes place and the final structure consists of strain free, equiaxed grains of fine ferrite produced at the expense of deformed elongated ferrite grains. 
• However it would produce very coarse grains if the steel has undergone critical amount of deformation. In such cases, full annealing is preferred. 

Aims of re-crystallization Annealing: 

• To restore ductility 
• To refine coarse grains 
• To improve electrical and mechanical properties in grain oriented Si steels

A typical re-crystallization curve at constant temperature: 

Related post:

• Annealing
• Full Annealing
• Process Annealing