Heat treatment in industrial furnaces – All there is to know

In industry, it is common to use heat treatment to modify the properties of certain materials by applying heat inside furnaces. However, choosing the appropriate treatment option for your company can be challenging, as technical and specialized knowledge is required to achieve the desired results.

This article will guide you on everything you need to know about heat treatment in industrial furnaces. With this information, you will be able to understand this process and its different applications in the industry.

What is the purpose of heat treatment?

The main objective of heat treatment is to alter the conditions of a piece's internal or surface microstructure, whether ferrous (such as steel or iron) or non-ferrous (such as copper or aluminum), to give it specific properties.

Among these are better hardness and resistance, malleability, suppression of residual stresses, and more.

Two factors determining appropriate heat treatment techniques are the correct temperature uniformity for the process and the efficiency of the equipment where said treatment is carried out (e.g., the efficiency of the combustion system used in the process, quality and condition of the furnace, etc.).

Fig. 1 Thermal treatment efficiency

These treatments are widely used in various industries, such as automotive, construction, and aerospace, to improve the quality and performance of the materials used to manufacture products such as crankshafts, brakes, gears, and turbine parts, among others.

Industry applications

Some of the most common applications we can highlight are:

• Providing a structure with better hardening and malleability. The aim is to give the material a greater hardness without generating a brittleness that makes it prone to cracks, which allows it to be more easily machined later for its final finish.
• Eliminate internal stresses and avoid deformation after machining. This objective is usually fundamental in forged or shaped parts and/or those subject to welding. Eliminating internal stresses prevents parts from deforming after being subjected to loads or pressures.
• Provide a more homogeneous structure. That is, to obtain a structure with the same physical characteristics in all parts of the piece. This is to achieve the maximum condition of hardness required and the desired level of resistance so that the material can withstand the loads and conditions for which it is designed.
• To alter some of the physical properties: Whether their thermal conductivity, their electrical resistivity, or their coefficient of thermal expansion, to adapt them to the specific needs of each application.

Heat treatment processes

Heat treatments can be classified into two major categories; those that generate a change in the product's chemical composition and those that do not.

• Heat treatments with change in chemical composition

These processes are related to controlled atmospheres and vacuum furnaces. Some of those that fall into this category are: carburizing, carbonitriding, and cyanide hardening.

• Carburizing: its objective is to increase the concentration of carbon on the piece's surface, thus creating a hard layer that is resistant to wear.
• Carbonitriding: this process has the same objective as carburizing but differs in using an atmosphere containing carbon and nitrogen.
• Cyanide Hardening: its objective is the same as carbonitriding, except that carbon and nitrogen are introduced using a cyanide salt solution in this case.

• Heat treatments without change in chemical composition

In this category, we find treatments carried out in non-controlled atmosphere furnaces. The best known are: annealing, normalizing, tempering, and quenching. The change induced in the product is specifically related to a physical phase change.

• Annealing: the piece is softened to facilitate its subsequent machining or working, regenerate the grain and eliminate internal stresses.
• Normalizing: returns to the piece the properties and structure considered regular and homogeneous characteristics of its composition, eliminating internal stresses.
• Tempering: this is a process of heating followed by rapid cooling to harden and increase the piece's resistance.
• Quenching: this is a sequential and complementary treatment to tempering. It allows you to decrease the hardness, increase the toughness, and eliminate the internal tensions produced in the tempering stage.

Fig. 2 NUTEC Bickley Aluminum Treatment Furnace

Most common failures

There are several reasons why heat treatment can face problems. Here we mention the most common ones.

• Temperature uniformity: this situation can be caused by various factors, including poor thermal insulation or lack of calibration of the equipment, which allows air to enter the furnace.
• Furnace inefficiency: this can be a common problem in older equipment that can no longer keep up with the current demand and production cycles required.

At NUTEC Bickley, we have a large team expert in engineering, development, manufacturing, and modifications that can help you solve failures in your heat treatment processes.

Consequences of suffering heat treatment failures

Without a suitable heat treatment process, there can be severe consequences when it comes to manufacturing your products.

One of the most important implications is the premature or immediate failure of components that cannot then withstand the conditions they are exposed to. This can put the safety and integrity of your equipment or the personnel that uses said product at risk.

For example, if an aircraft turbine component is not properly heat treated, it will likely fail in flight, which could have extremely serious consequences.

Solutions offered by NUTEC Bickley

At NUTEC Bickley, we have a deep understanding of heat treatment processes, which allows us to optimize the efficiency of your current or new furnaces, adapting them to the process necessary to treat your parts effectively.

We offer various services and spare parts through technical visits and component changes, including your equipment's calibration and temperature adjustment.

Are you interested in learning more about heat treatment processes and industrial heating solutions? Find more of it on our Newsroom!