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PT. Bainita Heat Industries in executing its services. Due to the need for on-site pre heat and post weld heat treatment services. From this modest beginning in heat treatment, PT Bainita Heat Industries has grown to become to leading supplier of heat treatment equipment and services, offering electrical and gas or oil fired heat treatment system to customer. Our services include local PWHT (for Pressure Vessel, Storage Tank, and Pipe), Preheating Local, Electrical Resistance Heating, Internal Firing by Gas, Internal Firing by Oil, Furnace ( Electrical, Oil Firing, Gas Firing ). We also provide field services for pre and post weld heat treatment to four main industry sectors-general engineering fabrication, power generation, petrochemical/refinery, and offshore/marine. PT Bainita Heat Industries a consider able experience on serving the customer. Our goal is to be heat treat solution for your steel. In our services, we are supported by professional engineer, qualified and experienced personel in Post Weld Heat Treatment Engineering and Strength Knowladge in Metallurgy and Material.

WHAT IS Post Weld Heat Treatment (PWHT) ?

Post Weld Heat Treatment (PWHT) is the process of reheating a weld to below the lower transformation temperature at a controlled rate, holding for a specific time and cooling at a controlled rate.

WHY NEED FOR POST WELD HEAT TREATMENT (PWHT)?

Residual Stress
The development of residual stresses approaching or even exceeding the yield stress is possible when welding thick sections. These stresses are created when a weld cools and its contraction is restricted by the bulk of the material surrounding it. . For certain industry sectors, eg. Petrochemical, Chemical, Oil and Gas, etc. the existence of residual stress of this magnitude is completely unacceptable. Residual Stress can cause damage and failure for material. A small hydrogen crack, was sufficient to cause catastrophic failure under test conditions. It is therefore important when considering PWHT or its avoidance, to ensure that all possible failure modes and their consequences are carefully considered before any action is taken.

Tempering Effect
Post Weld Heat Treatment (PWHT) will generally result in a modification of the microstructure of both the weld metal and heat affected zone.

Effect on Mechanical Properties

  • The consequences of Post Weld Heat Treatment (PWHT) compared with the as-welded condition
  • Yield strength is decreased slightly, the effect falling off fairly rapidly with time.
  • The tensile strength is decreased.
  • The ductility is increased.
  • Hardness levels are reduced.
  • Toughness is slightly reduced at short times but the effect can be significant over longer times

Effect on Creep Properties
For creep resisting material, Post Weld Heat Treatment (PWHT) is required in order to fully develop the creep strength. This is especially true for thicker components such as headers. But a variety of conditions have to be met

Other benefits

  • Improving the diffusion of hydrogen out of weld metal
  • Softening the heat affected zone and thus improving toughness (although not weld metal toughness)
  • Improving dimensional stability during machining.
  • Improving ductility.
  • Improving the resistance to stress corrosion cracking.
  • Reducing the effects of cold work.

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