Why P91 material used for welding procedure?

by Dinesh


Posted on Augus 22, 2017 at 1:00 PM



The P91 material is one of the popular choices for welding process that has been used for the last two decades for different applications. This material has unique characteristics so it can be widely preferred for the construction process and this contributes to the great thermal fatigue life at any point of the time. Apart from that, this material is popularly used in a thermal power plant to increase the efficiency.

Why is P91 different?

In general, grade 91 contains following components:

  • 9% Chromium
  • 1% Molybdenum

Usually, chromium improves high temperature as well as increases strength in addition to this molybdenum ensures the creep resistance. On the other hand, this material also contains a very smaller amount of Nickel and Manganese that completely ensures the harden ability of the steel. On the whole, this steel is perfect for welding applications and not tolerant to variations in its microstructure.

Unlike P22 grade or any other materials, P91 works in a different way and it has great qualities so it can be perfect for the heat treatment requirements.

Welding P91:

Welding is the key factor which can be used during the construction; most importantly it will affect the microstructure. Normally, preheating, inter-pass temperatures, as well as the post-weld heat treatments are really critical for P91 grade material. To get better control on the thick walled pipes it is important to introduce the heating system. P91 grade material is perfect for welding because it helps to maintain inter-pass temperatures as well as ensures worker friendly heating process. Apart from that, it is the perfect material for complex shapes including weldolets and tees.

Besides, the presence Nickel and Manganese content ensure the strength of the material as well as these also have great effects on the critical temperatures, these components decide the heat treatment temperature and cooling rates. Normally, the composition of the welding electrodes used in line with the respective parent material which decides those factors so P91 is perfect for welding.

P91 is the major construction material that can be utilized for different applications when it comes to suing this material for welding it is important to apply particular methods for welding. Power Plants utilized P91 material to receive better effeminacy. Normally, grade P91 weld joints also cool to below 200 degrees F so it is perfect for a complete transformation of austenite materials.

The Uniqueness Of P91 Grade Material:

P91 material preferred for its unique properties, the un-heat treated steel has great qualities as well as has an immense affinity to Hydrogen. In most conditions, Hydrogen can cause stress corrosion cracking so it is important to complete the preheating process to remove any moisture. In addition to this, the post welds heat treatment also done in a quick manner. However, this wills problems created by moisture condensation, rainfall and etc so it can be useful in different conditions. Now, most construction companies accept the use of 91-grade steel and now it continues to its successful journey.


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