ANNEALING
A heat treatment method that typically involves heating steel to a specific temperature, holding it at that temperature, and then cooling it in order to achieve structures close to equilibrium state.
We distinguish between recrystallization annealing, homogenizing annealing, stress-relief annealing, full annealing, isothermal annealing, and spheroidizing. In the field of annealing, we fulfill orders covering the entire range of services.
Annealing – Additional Information
Annealing can be classified into operations as follows:
During which allotropic transformations do not determine the essence of the process (such as in homogenizing annealing),
During which allotropic transformations do not occur (recrystallization annealing, stress-relief annealing),
During which allotropic transformations occur, determining the final structure (normalizing annealing, full annealing, isothermal annealing, spheroidizing annealing).
Types of Annealing:
Recrystallization Annealing involves heating a metal that has been previously cold-deformed to a temperature above the recrystallization temperature, holding it at this temperature, and then cooling it at any rate.
Recrystallization annealing, often used as an intermediate process during cold rolling or drawing of metals, removes work hardening, resulting in a reduction in hardness and strength while increasing the metal’s ductility, which enables further cold plastic deformation.
Homogenizing Annealing involves heating steel to a temperature of 1050–1200°C, about 100–200°C lower than the solidus temperature, holding it at this temperature for an extended period, and then cooling it.
The purpose of this operation, primarily used for steel ingots, is to reduce the chemical composition heterogeneity caused by microsegregation, and to some extent, by liquation.
Stress-Relief Annealing involves heating steel to a temperature below Ac1, holding it at this temperature, and then slowly cooling it. The purpose of this operation is to relieve internal stresses.
Stress-relief annealing is almost unrelated to structural changes in the material.
The temperature range and duration of stress-relief annealing are broad, and these parameters depend on the type of material and the causes of the stresses.
Full Annealing, used for alloy steels, involves heating the steel to a temperature 30–50°C above Ac3 or Accm (GSE line), holding it at this temperature, and then cooling it very slowly, for example, in a furnace, within the temperature range between Ac3 and Accm, down to Ac1.
Further cooling can take place in air.
Isothermal Annealing, a variation of full annealing, involves heating the steel to a temperature 30–50°C higher than Ac1, holding it at this temperature, rapidly cooling it to a temperature slightly lower than Ac1, maintaining it isothermally at this temperature until the pearlitic transformation is complete, and then cooling it in air.
Isothermal annealing is used in the heat treatment of alloy steels that exhibit excessive hardness after full annealing.
Spheroidizing Annealing, also known as softening, involves heating the steel to a temperature close to Ac1, holding it at this temperature, then slowly cooling it to around 600°C, followed by any cooling method to room temperature.
As a result of the spheroidizing process, the steel structure consists of globular cementite, known as spheroidite, embedded in a ferrite matrix.
This structure provides low hardness, good machinability, and excellent plastic deformability during cold plastic deformation processes.
It is also the proper structure for hypereutectoid steels before subsequent hardening.
Max. dimensions of the working chamber for ANNEALING:
We offer the execution of annealing processes in vacuum furnaces with a maximum capacity of 1200 kg, in atmospheric furnaces with a maximum gross capacity of 1800 kg, and in pit furnaces. The size of the working chamber is as follows.
a = max 1200mm
b = max 900mm
c = max 750mm
The dimensions apply to processes such as hardening and carburizing (cooling in oil or gas), aging, solution heat treatment, tempering, annealing, and brazing in a vacuum chamber furnace.
Aging, tempering, and annealing in an atmospheric furnace:
a = max 1500mm
b = max 1000mm
c = max 900mm
Nitriding, sulfonitriding, tempering, aging, and annealing in a pit furnace:
h = max 1900mm
r = max 1000mm
