Do you know the types of annealing heat treatment?

Annealing is a heat treatment process in which steel parts are heated to a certain temperature, held at that temperature for a period of time, and then slowly cooled to room temperature. This process helps to relieve stresses, improve mechanical properties, and refine the structure of materials. There are three main types of annealing: Full Annealing, Spheroidizing Annealing, and Stress Relief Annealing.

1.Full Annealing

Full annealing involves heating the steel to a temperature above its critical point (usually between 710-750°C, but some alloy steels may reach 800-900°C), holding it at this temperature for a specific duration, and then slowly cooling it, either in the furnace or in sand. The purpose of full annealing is to:

Refine the grain structure.

Homogenize the material.

Lower the hardness.

Eliminate internal stresses.

This type of annealing is commonly used for steel materials with a carbon content of 0.8% or less, such as forgings and cast steel parts.

Annealing heat treatment

2.Spheroidizing Annealing

Spheroidizing annealing involves heating the steel to a temperature just above the critical point (usually 20-30°C higher than the critical temperature), holding it for a specific time, and then slowly cooling it down to below 500°C before air cooling. The goal is to:

Reduce the hardness of the steel.

Improve its machinability.

Prepare the material for subsequent hardening, helping to reduce distortion and cracking during quenching.

Spheroidizing annealing is typically used for carbon steels and alloy tool steels that have a carbon content greater than 0.8%.

3.Stress Relief Annealing

Stress relief annealing involves heating steel to a temperature between 500°C and 650°C, holding it for a specified time, and then slowly cooling it, typically by furnace cooling. The purpose of stress relief annealing is to:

Eliminate internal stresses that arise during welding, cold straightening, or machining processes.

Prevent future distortion or deformation during further processing or use.

This type of annealing is commonly used for castings, forgings, welded parts, and cold-extruded components.

Annealing heat treatment is a vital process in the manufacturing and processing of steel materials. Each type of annealing—full annealing, spheroidizing annealing, and stress relief annealing—has specific applications depending on the material and the intended outcome. Understanding these types helps to optimize material properties and performance, ensuring the longevity and reliability of components across various industries. Email:sales@haihaogroup.com