P91: make this type of steel even more useful

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You might be familiar with P91 steel from various industrial applications, such as in different power plants. It is a type of alloy steel known for its high strength and excellent resistance to high temperatures and pressure. In this article, you can read more about the heat treatments that can strengthen material P91.

What makes material P91 a useful material?

Material P91, a type of advanced alloy steel known as ASTM A335 P91, is particularly useful in various industrial applications due to its unique set of properties. These properties make it an ideal material for high-stress, high-temperature environments.

  • High Temperature Strength: P91 steel retains its strength at temperatures where many other materials would weaken or fail. This makes it suitable for applications involving high temperatures, such as in power plants or boiler applications.
  • Good Creep Resistance: Creep resistance is the ability to resist deformation under mechanical stress over time, especially at high temperatures. P91’s excellent creep resistance makes it reliable for long-term use in harsh environments.
  • Enhanced Oxidation Resistance: This material can withstand exposure to oxidizing atmospheres at high temperatures, which is crucial in preventing corrosion and prolonging the life of components.
  • Improved Weldability: Despite its strength, P91 steel has relatively good weldability compared to other high-alloy steels. This is important for the fabrication and repair of large structures where welding is necessary.
  • Thermal Conductivity and Heat Transfer: P91 has favorable thermal conductivity, which is beneficial in applications where heat transfer is essential, such as in heat exchangers.
  • Cost-Effectiveness: In comparison to other materials offering similar performance, P91 can be more cost-effective, especially considering its durability and lifespan under extreme conditions.
  • Resistance to Thermal Fatigue: P91 can withstand frequent temperature changes without significant degradation, which is important in cyclic operations where temperatures fluctuate regularly.

These characteristics make P91 a highly sought-after material in industries like power generation, petrochemical, and any other field requiring materials that can endure high temperatures, pressures, and challenging environmental conditions.

Which preheating methods can be extended on material p91?

The question is not about what methods can be applied to Material P91, but rather the purpose of treating this type of steel. Once you have the goal in mind, the corresponding heat treatment for P91 can be carried out. Delta Heat Services performs the following heat treatments:


Purpose: Annealing is used to reduce internal stress in a metal, homogenize the structure, and lower hardness to improve machinability.
Process: In annealing, the material is heated to a specific temperature, usually above the critical temperature, and then slowly cooled in the oven. This results in a softer structure.


Purpose: The goal of normalizing is to refine the steel’s microstructure and create a uniform structure.
Process: Similar to annealing, the steel is heated, but in normalizing, the cooling is done in air, resulting in faster cooling than annealing. This leads to a harder and stronger material than post-annealing.

Pre-Weld Treatment

Purpose: Pre-weld heat treatment often involves preheating the material to minimize thermal stress and reduce the risk of cracking during welding.
Process: This process can take various forms, such as electric resistance heating or induction heating, and is aimed at raising the material’s temperature to a specific level before welding.

Post-Weld Treatment

Purpose: The purpose of post-weld heat treatment is to improve the properties of the welded material, such as relieving stresses that have arisen during welding and reducing hardness in the heat-affected zone.
Process: This can include stress relief annealing, where the material is heated to a lower temperature than the normal annealing process and then slowly cooled.

Each of these processes plays a crucial role in metalworking and is chosen based on the material properties and the requirements of the final product.

Preheating material P91 at Delta Heat Services

You can find different heat treatments at Delta Heat Services. It’s all covered under Electrical Heat Treatment or Induction Heating. Ask us what’s the best for your material p91 steel or other types of steel. Our heat treatment experts can provide you with all the necessary advice. In addition to that, you can also purchase or rent the required equipment from us. Please fill in our contact form and get personal advice about the heat treatments of material p91 or another piece that needs it.

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