Heat Treatment & PWHT

Subodh Material Technologists provides heat treatment and post weld heat treatment (PWHT) services for welded components, steels, alloys and engineering materials.

Our heat treatment capabilities include PWHT, stress relieving, normalizing, tempering, aging, quenching and step cooling, with controlled furnace cycles and computerized temperature-time graph recording.

Heat treatment can be used to control residual stresses, hardness, microstructure, strength, toughness and other metallurgical properties depending on the material, welding condition and applicable specification.

Post Weld Heat Treatment (PWHT)

Post Weld Heat Treatment (PWHT) is a controlled heating and cooling process applied to welded components to reduce residual stresses and modify metallurgical properties following welding.

PWHT can be important for welded pressure equipment, piping, process equipment and other critical components where the applicable design code or material specification requires controlled heat treatment.

The PWHT cycle can involve:

• Controlled heating

• Specified heating rate

• Soaking at the required temperature

• Controlled holding time

• Controlled cooling

• Temperature monitoring

• Computerized temperature-time graph

• Heat treatment documentation

PWHT requirements depend on factors such as material grade, thickness, welding procedure, service conditions and the applicable design or fabrication code.

Stress Relieving

Stress relieving is a heat treatment process used to reduce residual stresses introduced by welding, machining, forming, fabrication or other manufacturing processes.

Controlled heating below the relevant transformation temperature followed by controlled cooling can reduce internal stresses while minimizing unwanted changes to the material microstructure.

Stress relieving may be applicable to:

• Welded components

• Pressure vessels

• Boilers

• Piping components

• Fabricated structures

• Machined components

• Heavy engineering components

Normalizing

Normalizing is a heat treatment process generally used for ferrous materials to refine and homogenize the microstructure.

The process involves heating the material to an appropriate temperature above its critical transformation range, holding it for the required period and subsequently cooling it in air.

Normalizing can be used to:

• Refine grain structure

• Improve microstructural uniformity

• Modify mechanical properties

• Reduce effects of previous thermal processing

• Prepare material for subsequent heat treatment

The exact normalizing cycle depends on the material grade, section thickness and applicable specification.

Tempering

Tempering is generally performed after hardening or quenching to obtain a desired combination of hardness, strength and toughness.

Controlled reheating below the relevant transformation temperature allows the microstructure and mechanical properties to be adjusted according to the intended application.

Tempering parameters depend on:

• Material grade

• Previous heat treatment

• Required hardness

• Required mechanical properties

• Component geometry

• Applicable specification

Quenching

Quenching involves controlled heating followed by relatively rapid cooling to obtain the required metallurgical transformation.

Depending on the material and application, quenching media can include:

• Water

• Oil

• Polymer solutions

• Forced air

• Other specified cooling media

The appropriate quenching process depends on the material chemistry, section thickness, required properties and risk of distortion or cracking.

Aging Heat Treatment

Aging is used for certain precipitation-hardening alloys to develop the required mechanical properties through controlled precipitation reactions.

Depending on the alloy, aging may be performed naturally or through controlled artificial aging at elevated temperature.

Aging treatments may be applicable to:

• Aluminium alloys

• Precipitation-hardening stainless steels

• Nickel-based alloys

• Maraging steels

• Other precipitation-hardening materials

The temperature and holding time are selected according to the material and applicable specification.

Step Cooling Testing

Subodh Material Technologists provides step cooling services for applicable materials.

Step cooling involves controlled thermal exposure followed by impact testing at specified stages to evaluate changes in toughness and determine the impact energy transition characteristics of the material.

Our step cooling service includes:

• Controlled heating

• Step cooling cycle

• Temperature monitoring

• Impact testing

• Impact energy evaluation

• Transition temperature determination

• Required graphical representation

Step cooling activities can be witnessed by TPI agencies and customers, where required.

Computerized Heat Treatment Graphs

Controlled documentation of the heat treatment cycle is an important part of PWHT and other thermal processing requirements.

Our heat treatment process uses automatic furnace systems with computerized temperature-time graph recording.

Heat treatment records can document:

• Heating cycle

• Heating rate

• Soaking temperature

• Holding time

• Cooling cycle

• Temperature versus time

• Multiple thermocouple channels where applicable

These records provide traceability of the actual thermal cycle applied during testing or heat treatment.

Heat Treatment of Welded Components

Heat treatment is particularly important for welded components because welding can introduce:

• Residual stresses

• Localized hardening

• Microstructural changes

• Changes in toughness

• Changes in ductility

PWHT and other controlled heat treatment processes can therefore be used where required to achieve the specified metallurgical and mechanical condition.

Applications include:

• Pressure vessels

• Process equipment

• Boilers

• Piping

• Oil & Gas equipment

• Petrochemical equipment

• Power plant components

• Heavy engineering fabrications

• Critical welded structures

Heat Treatment & Mechanical Property Evaluation

Heat treatment is often followed by mechanical or metallurgical testing to verify the resulting material condition.

Depending on the requirement, evaluation may include:

• Tensile testing

• Yield strength

• Elongation

• Impact testing

• Hardness testing

• Microhardness testing

• Metallographic examination

• Chemical analysis

This allows the heat treatment condition to be correlated with the resulting mechanical and metallurgical properties.

Metallographic Evaluation After Heat Treatment

Metallographic examination can be used to evaluate microstructural changes resulting from heat treatment.

Depending on the material and requirement, examination may assess:

• Grain structure

• Phase transformation

• Carbide morphology

• Weld metal microstructure

• HAZ microstructure

• Heat-treatment effects

• Microstructural uniformity

Metallography can complement hardness and mechanical testing during heat treatment qualification and evaluation.

Applications of Heat Treatment Services

Our heat treatment and PWHT services support applications in:

• Oil & Gas

• Petrochemical

• Power Generation

• Nuclear

• Heavy Engineering

• Pressure Equipment

• Boilers

• Piping

• Marine

• Infrastructure

• Automotive

• Aerospace

• Defence

• Research & Development

Why Choose Subodh Material Technologists?

Controlled Heat Treatment

Our heat treatment services use controlled furnace cycles and temperature monitoring for repeatable thermal processing.

Computerized Graph Recording

Temperature-time cycles can be recorded using computerized systems to provide traceable heat treatment documentation.

Integrated Metallurgical Testing

Heat treatment can be combined with tensile, impact, hardness, microhardness and metallographic evaluation.

Welding & PWHT Expertise

Our laboratory supports welding-related testing, weld qualification and PWHT-related material evaluation.

NABL Accredited Laboratory

Subodh Material Technologists operates as a NABL accredited laboratory as per ISO/IEC 17025:2017, Certificate TC-8225.

Related Material Testing Services

Explore our related services:

• Welder Qualification & PQR Testing

• Welding Consumable Qualification

• Mock-Up Testing

• Tensile Testing

• Charpy Impact Testing

• Hardness Testing

• Microhardness Testing

• Metallography

• Creep & Stress-Rupture Testing

• Chemical Analysis

• Corrosion Testing

• Fracture Mechanics & Fatigue Testing

Frequently Asked Questions

What is PWHT?

PWHT, or Post Weld Heat Treatment, is a controlled thermal treatment performed after welding to reduce residual stresses and achieve the required metallurgical and mechanical properties.

Why is PWHT performed?

PWHT may be required to reduce residual stresses, control hardness, modify microstructure and achieve specified mechanical or service-performance requirements.

What is stress relieving?

Stress relieving is a controlled heat treatment used to reduce residual stresses produced by welding, machining, forming or other manufacturing processes.

What is normalizing?

Normalizing is a heat treatment generally applied to ferrous materials to produce a more uniform and refined microstructure and achieve the desired mechanical properties.

Do you provide computerized PWHT graphs?

Yes. Our heat treatment capability includes computerized temperature-time graph recording for applicable heat treatment cycles.

Do you provide step cooling testing?

Yes. Subodh Material Technologists provides step cooling services with the associated impact testing and graphical evaluation required for applicable materials.

Can heat treatment be followed by mechanical testing?

Yes. Depending on the requirement, heat-treated materials can be evaluated using tensile, impact, hardness, microhardness and metallographic testing.

Can PWHT be performed for welded components?

Yes. PWHT services can be provided for applicable welded components according to the specified heat treatment procedure and project requirements.