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Annealing at ADI


ADI Treatments have always been proud to offer a wide range of annealing treatments and we have seen a steady growth in the department year on year.

Our expertise and specialised plant allow us to offer a wide range of annealing processes including stress relieving, sub-critical annealing, normalising and controlled atmosphere full annealing.

Our plant allows us to offer treatments between the temperatures of 200 and 970 degrees Celsius and achieves a throughput of over 1200kg per hour offering quick turnaround to meet customer needs.

Please click on the links to the left-hand side to read more about the processes and plant at ADI.


Annealing Processes


ADI Treatments offer a wide range of annealing processes. Our specialised plant, with the option of controlled atmosphere treatments via dedicated exothermic gas generators, allow us to treat parts in the sub critical and full annealing ranges without the possibility of oxidation and scale whilst maintaining the flexibility to provide lower temperature stress relieving processes. Our experienced team of staff can offer advice and guidance on the processes we offer, and these include, but are not limited to:


Stress Relieving

Materials which have undergone machining or cold working will often have residual stresses which could cause unwanted dimensional changes if the material were to undergo a further machining or heat treatment process. Stress relieving can help to minimise the risk of these dimensional changes occurring and is often performed on items which have been roughly machined before the final machining processes take place in temperature ranges from around 500 to 650 degrees Celsius. 

The reduction in the possibility of dimensional change makes stress relieving all but essential for components which have tight tolerances, or ones that will receive further treatments such as carbo nitriding. The Heat Affected Zones (HAZ) around weld sites can also benefit greatly from the stress relieving process as the structure of the material in the HAZ can often be full of residual stresses due to the different materials and cool rates of the parent material and the weld. 

The stress relieving process does not change the structure of the material or affect its hardness, and the uniform, slow cooling of components is paramount to ensure dimensional differences are taken into account. 


Sub Critical Annealing

These processes, normally performed in the 680 – 780 degree temperature range, focus on creating a microstructure where there is an even distribution of spheroidal carbides making the material softer, tougher and easier to machine. This structure will improve the cold formability in steels and allows processes such as cold or deep drawing, where severe deformation takes place, to be carried out. The effect of this type of treatment will depend heavily on the original material and microstructure.



As the name suggests, normalising is used to create a homogenous, fine grain microstructure. The hot rolling, forging or casting processes can often result in a material where the microstructure is not homogenous containing large grain sizes and unwanted components such as carbides. The normalising process is carried out in temperature ranges between 800 – 950 degrees Celsius, normally under a controlled atmosphere to avoid oxidation, and refines the microstructure of the material by allowing finer austenitic grains to be formed at the higher temperature which allow fine ferritic grains to form upon cooling. These new grains will be finer and more homogenous than the original microstructure, will allow machining operations to be performed more easily and will give confidence in the mechanical properties of the material.


Full Annealing

This process is normally performed on components which have cooled rapidly after forging or hot rolling. The components will be hard to machine and may risk the possibility of cracks forming during further hardening processes. The annealing process will soften the metal by creating spheroidised cementite from the pearlitic structure held in a soft ferritic matrix. This will allow the material to be machined more easily and reduce the risks of cracking occurring during other processes. The process will normally be carried out between 800 – 950 degrees Celsius under a controlled atmosphere to prevent oxidation.

Plant & Capacity

The annealing department at ADI Treatments consists of three continuous belt annealing furnaces which are all capable of providing the full spectrum of annealing processes from stress relieving through to controlled atmosphere full annealing. All lines can take components up to around 0.2m in height.


Our slightly narrower (0.6 m wide, throughput of approx. 250kg/hr), gas powered furnace is often used for smaller components such as rivets. These components will often require a “bright” finish and this furnace is set up to provide this treatment. Exothermic gas is used to provide the controlled atmosphere required for this treatment and is monitored closely to ensure a high quality finish is maintained at all times. Our smaller furnace excels in providing the very best of what would often be referred to as a “bright anneal”.


Our two wider furnaces are both electric powered and allow us to offer flexibility in the process temperatures we can run simultaneously ensuring down time due to changes in process temperature is kept to a minimum. 


The older of the two furnaces (0.85m wide, throughput of approx.. 500kg/hr) is a high-powered electric furnace which we consider to be a “jack of all trades”. Its dimensions allow us to treat a wide range of components effectively and the high-power electric heating means the furnace can heat rapidly from cooler temperatures when different process parameters are required. This power also serves to ensure parts reach temperature quickly, are heated homogenously, and have a good time spent at the process temperature whilst maintaining throughput.


Our second electric powered furnace (0.9m wide, throughput of approx. 500kg/hr) is specifically designed to offer a longer soak time at temperature and a slower cool. This line is extended beyond the length of the other two furnaces to allow a heating zone which is roughly twice the size of that seen on the other furnaces and a cooling zone which is also much longer and allows a steadier cooling of components. This furnace excels at treating parts which would benefit form a longer soak time to ensure the microstructure has transformed correctly and the slower cool allows this transformation to take place in the best way possible. 

Our 4 exothermic generators provide high quality gas to our annealing furnaces allowing us to offer controlled atmosphere processes which ensure oxidation and scale is eliminated so our customers can perform machining or plating operations without fear of unwanted surface elements causing issues.


We can also offer a batch annealing process for components which are either too large to fit down one of continuous belt annealing lines or where the treatment requires a long and precisely controlled temperature gradient either on heating or cooling of components. We can again offer both controlled and open atmosphere treatments for our batch annealing process.


Below you will find a selection of papers, mainly focussing on the Austempering process, to give a deeper understanding of the benefits and use cases for Austempered products. 

Please click on the links below to download the papers.

You will also find a link to a copy of our Conditions of Business at the bottom of the page.

(Please check the downloads folder in your browser once the download is complete).


ADI Solutions in Europe 

A paper outlining the work done to devlop new axle parts with close collaboration between foundry, designer and heat treater.


Crankshaft Design for TVR

A collaborative paper outling the work done between ADI treatments, Applied Processes and TVR to develop a Crankshaft in ADI for the high performace TVR Tuscan.



ADI in Large Diesel Engines

Part 1                                                                  Part 2

An article published in two consecutive issues of the Institue of Cast Metals Engineers Foundry Trade Journal discussing the advantages of ADI for applicatioons in High-Performance Diesel Engines 


World Foundry Congress 2016 Presentation

Notes from the joint talk given at the World Foundry Congress in 2016 giving some excellent test data and comparisons between as cast and heat treated materials.


Carbidic ADI

Paper published in the Institute of Cast Metals Engineers Foundry Trade Journal explaining some of the many advantages of using CADI in wear resistant applications.

Conditions of Business