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Effect of Niobium in Steel and Its Influencing Factors

By Thomas Huang March 9th, 2024 108 views

I The role of niobium in steel and its characteristics

Niobium in steel is a commonly used microalloy element.  The quality of steel will be highly improved by adding a certain amount of niobium.
1. Increase the strength of steel. 
The yield strength of steel can be increased by more than 30% only by adding 0.03% ~0.05% niobium.  
Niobium can also adjust the toughness level of steel in a wide range by inducing precipitation and controlling cooling rate to achieve a dispersed distribution of precipitates. 
 2. Improved corrosion resistance of steel: 
Niobium can reduce oxidation, corrosion, and wear of steel, thus improving the corrosion resistance of steel. 
 3. Improve the workability of steel: 
The addition of niobium can improve the workability of steel, reduce the hardness of steel, and improve the plasticity and workability of steel. 

II. Influencing factors of niobium in steel

1. Niobium addition:

The addition of niobium has a greater impact on the quality of steel, generally adding 0.05%-0.15%. 

2. Heat treatment process of steel:

The heat treatment process of steel will also affect the role of niobium, usually according to the composition, shape and use of steel and other factors to choose the heat treatment process.

III. Application fields of niobium in steel

 Niobium in steel is widely used in many fields, such as pipelines, ships, construction, machinery, and automotive industries.  In shipbuilding industry, the use of niobium in steel can improve the corrosion resistance and tensile strength, while reducing the weight of the hull, has been widely used in ship design. 

 The application grade of niobium steel in chemical equipment 

3.1 18MnMoNbR is a steel with the highest strength grade in the steel pressure vessel standard.

Low alloy steel with yield strength of 500MPa for pressure vessels.  At 300°C allowable stress can be provided to 197MPa(thickness 30~60mm).   The upper temperature limit can be increased to 525°C. 
 It is mainly used for manufacturing high pressure container cylinder, such as ammonia synthesis tower, urea synthesis tower, etc. 

3.2 13MnNiMoNbR is a steel grade with better comprehensive properties in single layer coil welded thick wall pressure vessels.

 At 400°C, the yield strength can still reach 300MPa.  Steel plate toughness, plasticity is very high, also has high impact absorption energy at low temperature.
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