Difference Between Sintering and Annealing

The key difference between sintering and annealing is that sintering is the process of applying heat to remove internal stress from certain materials, whereas annealing is the process of applying heat to agglomerate metal particles.

Sintering and annealing are important industrial processes that involve heat treatments. These processes include different operating steps and different operating conditions as well.

CONTENTS

1. Overview and Key Difference
2. What is Sintering
3. What is Annealing
4. Side by Side Comparison – Sintering vs Annealing in Tabular Form
5. Summary

What is Sintering?

Sintering is the process of welding together small particles of a metal by applying heat below the melting point of the metal. It involves the application of heat to remove internal stresses from certain materials. This process is mainly useful in manufacturing steel. The uses of sintering process include the formation of complex shapes, production of alloys and the ability to work easily with metals having high melting points.

In the manufacturing process, we have to use a bed of powdered iron from iron ore. This iron has to be mixed with coke before using it. Then the bed of iron is ignited using a gas burner. The burned portion is then passed along a travelling grate. Here we have to draw air through the grate in order to initiate a combustion reaction. Then a very high heat is generated, which causes tiny particles of the metal to form lumps. These lumps are suitable to be burnt in a blast furnace in order to form steel. In addition, the sintering process is important in the manufacture of ceramic and glass as well.

What is Annealing?

Annealing is a heat treatment process in which we have to heat a metal to a predominant temperature, hold for some time, and then cool it down to improve ductility. Annealing is the process of softening a material to obtain desired chemical and physical properties. Some of these desirable properties include machinability, weldability, dimensional stability, etc.

The annealing process involves the heating of a metal to or near critical temperature (critical temperature is the temperature at which the crystalline phase of metal changes). Heating to such a high temperature makes it suitable to fabricate. After heating, we need to cool the metal to room temperature using an oven.

The slow cooling of metal produces a refined microstructure. This may partially or completely separate constituents. The annealing treatment process is applicable to pure metals and alloys as well. According to this process, there are two types of ferrous metals as below:

1. Full annealed ferrous alloys (use very slow cooling process)
2. Process annealed ferrous alloys (cooling rate may be faster)

Other metals such as brass, silver, and copper can be fully annealed, but they need to be cooled quickly using the method of quenching in water.

What is the Difference Between Sintering and Annealing?

Sintering and annealing are important industrial processes that involve heat treatments. The key difference between sintering and annealing is that sintering is the application of heat to remove internal stresses from certain materials, whereas annealing is the application of heat to agglomerate metal particles.

Sintering is the process of welding together small particles of a metal by applying heat below the melting point of the metal. Annealing is a heat treatment process in which we have to heat a metal to a predominant temperature, hold for some time and then cool it down in order to improve ductility.

Below is a tabulation of the difference between sintering and annealing.

Summary – Sintering vs Annealing

Sintering and annealing are important industrial processes that involve heat treatments. The key difference between sintering and annealing is that sintering is the application of heat to remove internal stresses from certain materials, whereas annealing is the application of heat to agglomerate metal particles.

Reference:

1.“Annealing.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 25 Sept. 2011, Available here.
2. “Sintering.” Wikipedia, Wikimedia Foundation, 25 Oct. 2019, Available here.

Image Courtesy:

1. “Iron powder” By Anonimski – Own work (CC0) via Commons Wikimedia
2. “Full annealing temp range” By georgelade – Own work (Public Domain) via Commons Wikimedia