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Annealing furnaces & ovens

Carbolite Gero offers a wide range of annealing furnace and annealing oven solutions, from standard to fully custom designed units. Below you will find suitable products sorted by atmosphere as well as a general introduction.

Please choose air atmosphere, inert atmosphere or vacuum to view a list of suitable annealing furnace and oven solutions:
 

Modified Atmosphere: Contact us!

Contact us for a free consultation and talk to a product specialist to find the most suitable solution for your application needs!

Modified Atmosphere: Contact us!

Contact us for a free consultation and talk to a product specialist to find the most suitable solution for your application needs!

Modified Atmosphere: Contact us!

Contact us for a free consultation and talk to a product specialist to find the most suitable solution for your application needs!

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Introduction to annealing with furnaces and ovens

Annealing is a heat treatment process that alters the physical properties of a metal in order to increase its ductility and make it easier to work with.

Metals are heated above their recrystallisation temperature and are kept at a steady temperature for a required length of time, before being allowed to cool. This method changes the internal microstructure of the metal as the atoms diffuse through the solid material, reducing the number of dislocations (linear defects within the metal's crystalline structure), increasing the size of the grains within the structure, and reducing stresses, resulting in a more workable material.

There are three stages to the process: recovery, recrystallization, and grain growth.

Stage 1: Recovery

The recovery stage involves heating the metal to soften it and remove dislocations and internal stresses. The process of heating provides the energy required to break bonds and increases the rate at which atoms diffuse through the solid material.

Annealing furnaces & ovens - Stage 1: Recovery

Stage 2: Recrystallization

During the recrystallization stage new “strain-free” grains will nucleate (form) and replace those deformed by dislocations and internal stresses. If the process is allowed to progress to the “grain growth” stage, the grains will continue to increase in size.

Annealing furnaces & ovens - Stage 2: Recrystallization

Stage 3: Grain Growth

If the annealing process continues beyond the recrystallization stage, the grain growth stage occurs. A piece of metal with large grains has higher ductility and machinability, but lower yield strength than a piece of the same material with smaller grains. The size of the resulting grains depends on both the temperature and processing time. Once the annealed metal has been worked, it is possible to increase its strength by subjecting it to other processes such as hardening and tempering.

Annealing furnaces & ovens - Stage 3: Grain Growth

Removing dislocations via annealing processes

When stress is applied to a metal, plastic deformation can occur, which generates defects in the crystalline structure, known as “dislocations”. The higher the number of dislocations within the material structure, and the more they move against each other, the harder the material becomes. Thus the aim of annealing is to prevent this by reducing the number of dislocations.

Industries that use annealing furnaces

Annealing is used throughout various metalworking industries, such as steel production, sheet metal manufacturing, and jewellery making. The overall process is the same, but the scale at which it is carried out depends on the industry.

Manufacturing facilities will utilise large units to anneal batches of material, whilst jewellers may use a smaller annealing oven, or even gas-powered blowtorches to anneal bespoke pieces of jewellery.

Although blowtorches may be convenient for some, a digitally controlled furnace or oven will always offer greater precision, temperature uniformity, and repeatability.

Annealing temperatures required for different metals

Different metals have different annealing temperatures. The table below shows examples of metals commonly used within manufacturing and jewellery making, alongside both their anneal and melting ranges.

Metal Annealing temperature* Melting temperature*
Aluminium 300 – 410°C 660°C
Brass 500 – 550°C >930°C
Copper 371 – 649°C 1084°C
Gold (24k) 200°C 1064°C
Platinum 700°C 1768°C
Stainless steel >1000°C 1400 – 1510°C
Sterling silver 649°C 894°C

*Please note that the values shown are approximate, and exact values are wholly dependent on the individual composition of the alloy.

Annealing under modified atmosphere

To prevent oxidation during processing, it is often necessary to anneal metals in a modified atmosphere environment. This could involve either an inert, reducing, or vacuum atmosphere, depending on the type of material.

Most steels are annealed in atmosphere consisting of a mix of nitrogen and hydrogen, which promotes decarburization (a reduction in the carbon content of the metal), however this is not desirable for some steel alloys in which the carbon content is crucial e.g., carbon steel. In these instances, a protective inert gas atmosphere may be more appropriate.
Annealing furnaces & ovens - Annealing under modified atmosphere

Annealing with Mesh Belt Furnaces

Continuous Mesh Belt Furnaces can be adapted for annealing processes under both hydrogen and inert atmospheres.

We offer custom systems with a maximum operating temperature of 1100°C, which can be designed for single or multi-zone operation.

Annealing with Mesh Belt Furnaces

Contact us for a free consultation

Whether it is a standard product with modified atmosphere capability or a fully customised system, Carbolite Gero has manufactured thousands of furnaces over the years and realised projects around the globe.

Contact us for a free consultation and talk to a product specialist to find the most suitable solution for your application needs!

Modified Atmosphere: Contact us!

Annealing furnaces & ovens - FAQ

What is the benefit of annealing metal in an annealing furnace or oven?

In an annealing furnace or oven, the heat treatment process makes hard, brittle metals softer and more ductile, which in turns makes them easier to work and form. This is especially beneficial for manufacturers as there is less risk of fracturing when the material is being bent or pressed.

At what point in a metalworking process should an annealing furnace or oven be used?

Depending on the metal and the desired result, heat treatment processes can vary, however, annealing is usually one of the earliest steps as it prepares the metal to be worked by increasing ductility. Once it has been formed into the desired shape, it may then be “hardened” then “tempered” to increase its strength and flexibility. Cold-worked metal can be annealed several times to relieve stresses and reduce the risk of material failure.

What industries make use of heat treatment via annealing?

Steel manufacturers, metalworkers, and jewellers all use annealing heat treatment to make the metals that they work with easier to manipulate, due to the reduction in dislocations and internal stresses. Annealing typically reduces the yield strength of the metal, therefore the material is usually subjected to a quenching and/or tempering process to restore any lost strength.

At what temperature should an annealing furnace or oven be used?

Precise annealing temperatures are dependent on the metal. The material will take on different properties depending on the temperature at which it is annealed, therefore the correct annealing temperature is defined by the desired properties. Both ferrous and non-ferrous metals can be annealed at a range of temperatures, provided these are below their respective melting points, and should be allowed to cool slowly in air.