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Annealing metals

Annealing is used to reduce hardness and stresses resulting from mechanical or thermal machining. It is characterized by longer duration than other types of heat treatment and very high temperature.

There are two types of annealing:

  • Soft annealing is performed to reduce the hardness of steel parts that require mechanical machining. They are heated below the transformation temperature and maintained within it for 5 to 10 hours and then slowly cooled down.
  • Stress relief annealing is used to remove or reduce the stresses created by welding, cutting out, or cold forging, and heavy mechanical cutting. The steel is heated to above the tempering temperature, kept there for 4 to 6 hours, and then slowly cooled.

Annealing metals with Sacher

One of the key processes in the field of thermal machining of steel and alloys is annealing. Sacher offers comprehensive metal annealing services to ensure a personalized approach to every project. Our projects are carried out using state-of-the-art equipment in our own machinery park, supported by a team of experienced experts who monitor all stages of the process. We invite you to take a look at our offer and to submit requests for annealing steel and its alloys.

Metal annealing – what is it?

Annealing is a process of heating the metal to a specified temperature, then holding it at that temperature and cooling it. This procedure produces a structure as close as possible to balanced. During the process, alotropic transformations may occur within the workpiece which may affect the quality of the resulting machining.

Why is steel annealing used?

The primary goals of annealing metals such as steel are to reduce the hardness of the material and to reduce the stresses resulting from heat or mechanical machining. Compared to other treatments, annealing has an extended duration and a much higher temperature.

Types of metal annealing

Steel alloys can be annealed in many different ways. The choice of the optimal machining method depends on i.e. the desired physical, chemical and durability properties of the material. The type of procedure also determines the temperature range and the duration of the entire process.

Normalization annealing

The purpose of this procedure is to achieve a uniform fine grain metal structure by heating, holding and cooling. Normalization annealing is characterized by very low air flow, which improves the mechanical properties of the metal. This type of annealing is most commonly used in cast steel and non-alloy steels.

Uniform (diffusion) annealing

This type of machining involves heating up the material to approx. 1200 °C, followed by holding it at that temperature and intensive cooling. This ensures that the nature of the resulting structure is also maintained at ambient temperature.

Stress relief annealing

Another type of high-temperature machining is stress relief annealing which, unlike diffusion annealing, focuses on very slow cooling of the material. This removes all molding, welding, and thermal stresses. The duration of the process depends on the mechanical properties of the steel or alloy that the manufacturer wishes to obtain. This is how annealing of stainless and austenitic steel is often done.

Recrystallization Annealing

Recrystallization is a process which involves annealing metals at a temperature of about 550-650 °C. This method is very often selected for parts that have been previously cold-treated to remove dents.

Complete Annealing

For alloy steels, one of the most common heat machining methods is complete annealing. Its purpose is to remove internal stresses and achieve a structure that is close to balanced. In addition, the material becomes more machinable, more ductile, and more malleable. Complete annealing involves heating the metal to about 30-50 °C from Ac3 and slowly lowering the temperature while exposing the steel to air.

Isothermal annealing

Alloy steels may also be subjected to the isothermal annealing process, which involves heating and holding the material at a given temperature, followed by isothermal cooling and cold machining.

Annealing metals and welded joints

One of the properties of welded joints is the instability of their structure. This can reduce the durability of the welded components. The durability of welded joints and their stability can be increased by using normalization annealing. Connection points subjected to this treatment increase their durability and resistance to external factors. Welded metals can also undergo stress relief annealing.

In both cases, the heat treatment may be partial or complete depending on the degree of risk of additional stresses. Partial annealing is carried out using gas technology, whereas complete annealing is carried out in a specially adapted furnace.

How to request steel annealing?

When selecting the correct annealing type, always use the parameters that the metal should posses after heat treatment. Our specialists are here to help you choose the right method. To work with us on metal annealing, simply submit a request or contact our office. We will be happy to provide you with all the information you need and we will provide you with an individual offer along with comprehensive pricing. We invite you to contact us!