Manufacturing process

Heat Treatment

Heat treatment changes the hardness, strength, toughness or internal stress of metal parts through controlled heating and cooling — often the step that makes a machined or forged part fit for service.

Process overview

Heat treatment uses controlled heating and cooling cycles to modify the mechanical and metallurgical properties of metal components. Processes may include annealing, hardening, tempering, stress relieving and case-hardening treatments depending on the material and performance target. Requirements can specify material grade, hardness range, treatment standard, case depth, distortion limits and verification testing.

Through-hardening steels are austenitised, quenched in oil, polymer, water or gas, and then tempered to balance hardness and toughness. Case hardening — carburising, carbonitriding, nitriding or induction hardening — creates a hard, wear-resistant surface over a tougher core, which is common for gears, shafts and bearing surfaces. Annealing, normalising and stress relieving soften material, refine its structure or reduce residual stress after welding, forming or rough machining. Aluminium alloys and precipitation-hardening stainless steels gain strength through solution treatment and ageing; that is how tempers such as T6 are produced.

Heat treatment can distort parts and change dimensions, so it is usually placed between rough and finish machining or followed by grinding. Vacuum furnaces limit oxidation and are often used for tool steels and precision parts. Results are verified through hardness tests, case-depth measurement, microstructure checks and, for some applications, mechanical testing and furnace records.

In aerospace and some automotive programs heat treatment is a controlled special process, and customers may require specific furnace qualification — for example AMS 2750 pyrometry — or Nadcap accreditation.

Typical capabilities & what manufacturers can produce

What manufacturers can produce

  • Hardened and tempered shafts, pins and tool parts
  • Carburised or nitrided gears and wear parts
  • Induction-hardened bearing seats and cam surfaces
  • Stress-relieved weldments and castings
  • Solution-treated and aged aluminium and 17-4 PH parts
  • Vacuum-hardened tool-steel dies and inserts

Capabilities under this process

Suitable materials

Materials commonly used with this process — an editorial reference, not a statement about facilities in the Metraxio network. Suitability always depends on the part and its application.

Relevant industries

Industries whose Metraxio industry guides list Heat Treatment as a common process, with the typical use in each.

What buyers should specify

The details that make Heat Treatment quotes comparable and let facilities be assessed on the right criteria.

Material grade and incoming condition
For example 42CrMo4, 16MnCr5, 1.2379 or 17-4 PH, and the condition parts arrive in.
Treatment
Through-hardening, carburising, nitriding, induction hardening, annealing, stress relieving or ageing.
Hardness
Target range and scale (HRC, HV or HB), and where on the part it is measured.
Case depth
Effective case depth and its definition (for example depth to 550 HV) for case-hardened parts.
Distortion and soft areas
Allowable straightness or flatness change, and areas that must stay soft or be masked.
Standard and records
Applicable treatment standard, furnace charts and pyrometry requirements, if any.
Test reports
Hardness reports, microstructure examination and test coupons.

On Metraxio these details become a structured manufacturing requirement. Processes, capabilities, materials, certifications and part size are checked against facility profiles; tolerances, finishes and inspection details travel with your drawings and are reviewed during quoting rather than used as automatic filters.

Frequently asked questions

Should heat treatment come before or after machining?

Usually after rough machining and before finish machining or grinding, because heat treatment can distort parts and make them harder to machine.

Carburising or nitriding?

Carburising gives deeper cases and is common for gears in case-hardening steels. Nitriding works at lower temperature with less distortion and a thinner, very hard layer. Load, material and allowable distortion decide.

What does T6 mean on aluminium?

T6 is a temper: solution heat treated and artificially aged. It describes the condition of an alloy such as 6061 or 6082, not a separate material.

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