Heat Treatment Services
AIE provides heat treatment services from its Kawerau workshop, supporting fabrication, machining and maintenance work across a range of industries.
Carrying out heat treatment in-house allows components to be processed without leaving site, improving control over handling, sequencing and quality, particularly for large or complex work.
The workshop is set up to manage both full component and localised heat treatment, with equipment and processes suited to a range of applications and material requirements.
Our Specialist Heat Treatment Services
We provide three core heat treatment services: Post Weld Heat Treatment (PWHT), stress relieving, and thermal expansion fitting. Each service is performed in compliance with ASME codes, with calibrated monitoring systems ensuring precision and complete traceability.
Post Weld Heat Treatment (PWHT) — controlled heating of welded components to relieve residual stress, restore ductility and improve mechanical properties after fabrication.
Post Weld Heat Treatment (PWHT) applied to a rotor shaft after journal weld repair to restore material properties and relieve residual stress.
Stress Relieving — heat treatment used to reduce internal stresses in machined, formed or fabricated parts, improving dimensional stability and long-term performance.
Controlled stress relieving of a fabricated component in our gas-fired oven to minimise distortion and ensure machining accuracy.
Thermal Expansion Fitting — precision assembly of interference-fit components using controlled heating and cooling to achieve clean, accurate fits without damage.
Ceramic heating elements installed on a bronze sleeve (Ø550mm x 2.3m) to achieve controlled thermal expansion for interference fitting onto a mild steel shaft.
Our Advanced Heat Treatment Capabilities
Direct-Fired Gas Ovens - Our direct-fired gas ovens are powered by Cooperheat control systems and are ideal for PWHT, stress relieving and thermal expansion fitting of large components. The built-in oven measures 2 m (W) × 2 m (H) × 5.6 m (L), and we supplement it with modular oven panels in 2.4 m × 2.4 m and 6 m × 2.4 m sizes, allowing us to build a custom oven around components that would not fit a standard chamber. Operating temperature is up to 640 °C.
Electric Ceramic Heating Elements - For localised heat treatment and precision thermal expansion work, we use electric ceramic heating elements powered by a 63 A Cooperheat Coopermatic control unit. The system supports up to twelve ceramic elements simultaneously and can reach temperatures of 800 °C. This approach is ideal for site work, repairs and applications where a full oven is not practical or where heat needs to be focused on a specific zone.
Thermal Expansion Fitting - Thermal expansion fitting allows us to achieve precision interference fits between mating components by carefully controlling their temperature differential at assembly. We combine heating and cooling techniques — including dry ice and liquid nitrogen — to suit a wide range of materials and sizes, from small bushes through to large sleeves and shafts.
Stress Out. Strength In.
Whether you have a one-off PWHT requirement, a recurring stress-relief programme, or a complex thermal expansion fit on a critical component, the AIE team can assess the work, determine the appropriate process and carry it out with full control of quality and traceability. For specific requirements or to discuss a job, contact the team to review your query.