Pressure Vessels

Each pressure vessel that we manufacture is per the American Society of Mechanical Engineers (ASME) code. As a leading ASME pressure vessels manufacturer, our specialty lies in working with a variety of alloys, pressures, & designs to meet your custom requirements. More »

Weld Overlay and Clad Vessels

Our weld overlay and clad vessels are fully code-compliant. We use our advanced welding techniques to their full capabilities to offer you the finest overlay/clad components and pressure vessels. More »

High Pressure Vessels

We hold the American Society of Mechanical Engineers (ASME) U, U2, and U3 stamps, and have the capabilities and resources to manufacture ASME high pressure vessel to your exacting specifications. More »

Autoclaves

We hold the American Society of Mechanical Engineers (ASME) U, U2, U3, PP, & S stamps, and have the capabilities and resources to manufacture autoclaves to your exacting specifications. More »

Heat Exchangers

We specialize in the design, engineering, and fabrication of Shell and Tube Heat Exchangers, including thermal calculations. All of our units are built in strict accordance with the latest edition and addenda of the A.S.M.E. Code, Section VIII Division 1, 2, or 3 and T.E.M.A.” More »

 

Why is Post Weld Heat Treatment Needed

Post Weld Heat Treatment (PWHT) is used to reduce stress in a piece of metal after it has undergone welding. Welding is an impotent process in many industries, especially manufacturing. It is useful in steel fabrication and construction of metal components. The temperatures used during the welding process are very high. This causes the metal to expand. Once the metal cools down, it shrinks. As a result, a lot of stress is locked in the metal. PWHT redistributes this stress caused by welding.

Importance of Post Weld Heat Treatment

PWHT is needed to make the metal more durable. It keeps the metal from cracking under the stress experienced during the welding operation. This process also offers the following advantages:

  1. PWHT increases the ductility and reduces the hardness of the metal.
  2. Since it reduces the hardness, the chances of stress related fractures are also minimized.
  3. The metal becomes less brittle.
  4. This process offers greater dimensional stability.
  5. PWHT reduces the risk of Hydrogen Induced Cracking (HIC).

Precautions and Considerations

Although PWHT is extremely beneficial to the application and life span of the product, care should be taken to ensure that the method adopted works in the favor of the particular metal.

  1. Consideration should be given to whether the base metal has been heat treated earlier.
  2. Some alloys and metal could experience cracking when undergoing PWHT. Thus, the alloy system needs to be taken into consideration.
  3. The PWHT temperature should never exceed the tempering temperature of the alloy or metal.
  4. The filler material used for welding will also undergo several changes when heat-treated. The compatibility of the filler material should also be taken into consideration.

The duration and range of temperature of PWHT depends on all the above factors.

Post weld heat treatment is critical to the proper functioning and reliability of the metal and application. It is imperative in increasing the life span of most metals. PWHT is one of the most important processes employed in steel fabrication.

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