16Mo3 boiler steel heat treatment

16Mo3 boiler steel is a low-alloy steel grade used for the fabrication of boilers and pressure vessels. 16Mo3 boiler and pressure vessel steel offers good weldability and high-temperature resistance, making it a popular choice in the power generation and petrochemical industries. However, to achieve the desired mechanical properties, 16Mo3 boiler steel requires appropriate heat treatment.

Heat treatment is a process used to alter the physical and chemical properties of a material by heating and cooling it. The purpose of heat treatment is to improve the material's hardness, strength, toughness, and ductility. In the case of 16Mo3 boiler steel, the heat treatment also helps in relieving the internal stresses caused by welding and fabricating.
 

The heat treatment of EN10028 16Mo3 boiler steel involves three steps:

1. Annealing

The first step is annealing, which is done to soften the steel and remove any internal stresses. Annealing is done by heating the steel to a temperature of 640-680°C and holding it at that temperature for a specific amount of time. The holding time depends on the thickness of the 16Mo3 boiler and pressure vessel steel and can range from one to several hours. After the holding time, the steel is slowly cooled down to room temperature in the furnace.

Annealing helps in improving the weldability of the steel by reducing its hardness and enhancing its ductility. 16Mo3 pressure vessel steel also helps in removing any residual stresses caused by welding or forming.

2. Normalizing

The second step is normalizing, which is done to improve the steel's strength and hardness. Normalizing is done by heating the steel to a temperature of 870-900°C and holding 16Mo3 steel at that temperature for a specific amount of time. The holding time depends on the thickness of the steel and can range from a few minutes to several hours. After the holding time, the steel is cooled down in still air.

Normalizing helps in enhancing the mechanical properties of the steel, including its strength, hardness, and toughness. 16Mo3 boiler and pressure vessel steel also helps in refining the grain structure of the steel by promoting the formation of fine-grained microstructures.

3. Tempering

The third step is tempering, which is done to reduce the hardness and improve the toughness of the steel. Tempering is done by heating the steel to a temperature of 500-620°C and holding it at that temperature for a specific amount of time. The holding time depends on the desired properties of the steel and can range from a few minutes to several hours. After the holding time, the steel is cooled down in still air.

Tempering helps in reducing the brittleness of the steel by increasing its ductility and toughness. It also helps in relieving any residual stresses caused by the previous heat treatment steps.