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Steel stress relieving after cutting. why do it?


In the context of processing metal or steel-based products, one of the interventions that must be carried out to ensure that the product does not undergo further compressions in the structure or variations during subsequent processing, is the treatment that allows the material to be tempered and stress relieved after cutting. We will analyse below what are the advantages that are obtained from this process, on which materials it is applied and how this process takes place in detail.

What are the advantages of stress relieving the material?

Any company that works on steel or metal products needs to work with raw materials that are of excellent quality. This feature is very important as during cutting and other processing on the material a series of compressions are exerted which could lead to a series of deformations of the same that could be uncontrolled, especially during subsequent processing. To avoid these problems and to minimise the risk of dimensional changes and compressions, it is advisable to subject the metal material or steel to stress relieving.

Thanks to this treatment, any deformation of the material is therefore avoided, which can be used for subsequent uses without any problem. Stress relieving usually takes place immediately after roughing and before the final polishing or grinding steps are performed.

This operation is particularly important for those metal pieces that have well-defined dimensional tolerances and which, in order to be used subsequently, will have to be subjected to subsequent heat treatments.

Specifically, the materials subjected to tempering have a shorter processing time and greater resistance of the resulting tools, properties that enable optimising of the working times in other activities. In particular, if the metal pieces that have undergone this process are not subjected to other heat treatment they will present reduced distortions with even greater advantages.

Another advantage that is obtained is that resulting from automation, especially regarding the clamping systems.

What happens during the stress relieving treatment of metals?

The stress relieving treatment does not make any changes to the composition of the materials nor does it affect its hardness. The metal pieces are treated and subjected to tempering so that stress relieving occurs at a temperature that is around 50 degrees centigrade lower than the temperature reached for the previous tempering, in order to avoid impacts on hardness. All metallic materials, including those in copper and brass and excluding those in steel, must be subjected to stress relieving before nitrocarburising at temperatures above 580 degrees. Stainless steels, instead, undergo stress relieving, which takes the name of solubilisation, at temperatures that are usually above 1000 degrees.

How the process takes place in detail

The temperature to be reached to stress relieve the material, especially steel, is between 550 and 650 degrees. Once this temperature limit has been reached, it must be maintained for one or two hours and immediately afterwards the material must be slowly cooled in an oven or in the open air. The cooling process is in no way less important as the speed of this operation must be very slow in order to avoid the tensions that can be generated by the differences in the temperature of the material. Following this phase with particular care is particularly delicate, especially in the case in which the materials subjected to the treatment are large.

In some cases, stress relieving can also be carried out in an inert gas oven, whose particular environment prevents the risk of oxidation of the external surfaces. If specific treatments are required, it is also possible to perform the operation in a vacuum oven.

To be sure that the operation is optimally executed, the stress relieving process must preferably be performed in a closed oven for approximately 24 hours, with slow and constant cooling at 35 degrees so that the same is proportional to both the core and for the edges in order to avoid tension in the material and to prevent the structure and strength of the same from being altered.