Heat treatments – find manufacturers and suppliers

Heat treatments are controlled thermal processes in which materials - especially metals - are specifically heated and cooled in order to improve or specifically adjust their mechanical, physical or chemical properties such as hardness, toughness, strength, ductility or corrosion resistance.

They are a key tool in materials technology for specifically adapting metals and other materials to their conditions of use.

Below you will find an overview of how heat treatments work and important types of heat treatments, their use, advantages and the challenges they present:

How heat treatments work:

The mode of operation is based on the targeted influence of temperature and time on the microstructure of a material. In the case of metals, the crystal lattice is changed, phase transformations are specifically controlled and stresses in the workpiece are reduced or generated. By heating to certain temperatures and defined cooling (fast or slow), new microstructures can be created that improve or specifically adapt the properties of the material.

The main principles are

1. Heating to a defined temperature,often in specific ranges depending on the material.
2. Holding (austenitizing, solution annealing, etc.) for a defined period of time in order to achieve equilibrium states.
3. Targeted cooling in air, water, oil or furnace - the cooling rate has a decisive influence on the microstructure.

Important types of heat treatment:

1. Annealing:
   A slow heating and cooling process to relieve stresses, regulate grain sizes or improve machinability.
   Variants are stress relief annealing, normalizing or soft annealing.
2. Hardening:
   Heating to hardening temperature and rapid quenching, e.g. in water or oil, to produce martensite or other hard microstructures.
   Increases hardness and strength, but often makes the material more brittle.
3. Tempering:
   Usually carried out after hardening.
   Reheating to lower temperatures to reduce brittleness and restore toughness.
4. Tempering:
   Combination of hardening and tempering - the aim is to achieve high strength combined with sufficient toughness.
5. Solution annealing and quenching:
   For non-ferrous alloys such as aluminum or stainless steel: the material is heated to a temperature at which alloying elements go into solution, then quenched to "freeze" this solution.
   This is often followed by ageing.
6. Precipitation hardening (or age hardening):
   Solution annealing is followed by selective heating to moderate temperatures to produce finely dispersed precipitates that increase strength.
   Typically used for aluminum, nickel or titanium alloys.
7. Case hardening:
   Surfaces are carbon-enriched and then hardened.
   The result is a hard surface with a tough core.
8. Nitriding:
   Surfaces are hardened in a nitrogen-rich atmosphere.
   Leads to wear-resistant, hard surface layers without major distortion.

Use of heat treatments:

Heat treatments are essential in industry and are used in a variety of applications:

1. Mechanical engineering:
Gears, shafts and bearings are hardened or tempered to prevent wear and breakage.

2. Toolmaking:
Tools need to be hard but tough. Hardening, tempering and surface hardening improve their service life.

3. Aerospace:
High-strength aluminum or titanium alloys are solution annealed and precipitation hardened for structural components.

4. Automotive engineering:
Crankshafts, axles or gear wheels are quenched and tempered or nitrided.

5. Pipeline construction:
Heat treatment can relieve stresses from weld seams.

6. Stainless steel processing:
Solution annealing avoids intercrystalline corrosion.

7. Medical technology:
Stainless steels are heat treated for optimum strength and corrosion resistance.

Advantages of heat treatment:

• Optimization of mechanical properties depending on requirements.
• Improvement of machinability or formability.
• Increased wear resistance and service life.
• Stress relief to avoid distortion or cracks.
• Corrosion resistance through structural adjustment.

Challenges of heat treatments:

• Requires precise temperature control and time control.
• Risk of distortion, cracks or uneven properties if treated incorrectly.
• High energy and equipment costs.
• Expertise and experience required to achieve the desired result.

Heat treatments make it possible to individually adjust properties such as hardness, toughness, strength or corrosion resistance and are therefore indispensable in practically all industrial sectors. Careful planning, precise process control and the right knowledge of materials are crucial to achieving the desired results.

Here you will find the most important aspects to consider when commissioning heat treatments.

Careful planning is crucial when commissioning heat treatments, as they significantly determine the mechanical properties and quality of a component. Only through clear specifications and close coordination with the service provider can the desired results be achieved reliably and economically.

• The first and most important step is a precise understanding of the material to be treated. Not every material reacts to heat in the same way: depending on the alloy, structure and previous processing, different heat treatment processes may be necessary or even harmful. Precise knowledge of the material is essential, especially for high-alloy steels, aluminum, titanium or nickel alloys.
• Before the heat treatment is commissioned, it should be clearly defined which property is to be achieved: higher hardness, better toughness, dimensional accuracy, corrosion resistance or low stress?
• The choice of process, temperature control and cooling strategy depends directly on the desired result.
• All relevant parameters must be clearly communicated to the heat treater. These include
• The desired process such as tempering, hardening, nitriding.
• The treatment areas or specific zones, e.g. only the surface.
• Further details such as hardening depths, hardness values, desired structural condition.
• Temperature ranges, holding times and cooling method.
• Tolerance limits to be observed for distortion, dimensional accuracy or surface quality.
• Unclear or incomplete specifications often lead to misunderstandings or unusable results.
• Not every company is equipped for every type of heat treatment or every material. The following points should be taken into account when selecting a partner:
• Experience with the desired material and process.
• Verifiable quality standards, e.g. ISO 9001, IATF 16949.
• Certifications for critical industries, e.g. aviation or medical technology.
• Reproducibility and traceability of processes.
• Possibility of documenting and issuing test reports.
• Heat treatments almost always lead to dimensional changes - through thermal expansion, transformation of the microstructure or stress release. These effects must be taken into account during component design, production and the tolerance chain.
• For critical components, an intermediate measurement or even post-processing after heat treatment is recommended.
• Before heat treatment, components should be clean, burr-free and free of oil, grease or scale. Residues can severely impair the result or cause chemical reactions.
• Welded joints should be stress-relieved or completely through-welded to prevent cracking. For sensitive geometries, it may be advisable to fix or pack the parts during treatment.
• Defined tests should be carried out after heat treatment - depending on the objective, for example:
• Hardness test e.g. according to Rockwell, Vickers or Brinell.
• Microstructure test by microsection.
• Dimensional check or roundness test.
• Crack testing, e.g. magnetically or by means of dye penetrant testing.
• Documentation of the process parameters.
• For safety-critical components, e.g. in aviation or vehicle construction, complete documentation and a test certificate are mandatory.
• Close coordination with the service provider is crucial. Particularly in the case of series components or initial sample approvals, there should be close communication and, if necessary, sampling and adaptation.
• A joint evaluation of test parts can help to achieve optimum results and establish process reliability.
• Components that are heat-treated should be packaged appropriately so that they are not damaged or contaminated during transportation. After treatment, protection against corrosion, e.g. oiling, may be necessary - especially for freshly hardened or bright surfaces.
• Heat treatments require energy, time and well-organized processes. In order to keep costs and throughput times under control, time windows should be coordinated with the processor as early as possible, batch sizes planned and delivery dates fixed.
• Unexpected rework or waiting times can jeopardize project plans.

The successful awarding of heat treatment contracts requires a sound technical understanding, clear specifications and close cooperation with a qualified heat treater. Only careful planning, communication and control can ensure that the desired properties are achieved and that the components can be used functionally, dimensionally stable and reliably.

Heat treatments can be ordered from various providers. Comprehensive information on heat treatment providers from all over the world can be found at Exportpages.