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00 Introduction The effect of nitrogen on the properties of steel is complex and multifaceted, encompassing both favorable and unfavorable effects. The following is a detailed analysis of the impact of nitrogen on the properties of steel: 01 Adverse effects 1.1 Reduction in plasticity and toughness: As the nitrogen content increases, the plasticity of steel, and particularly its toughness, decreases significantly. This causes the steel to be more prone to fracture under stress, thereby reducing its safety and reliability. 1.2 Increased brittleness: Nitrogen increases the cold and hot brittleness of steel. Cold brittleness refers to the significant reduction in the toughness of steel at low temperatures, making it more prone to brittle fracture. Thermal brittleness refers to the reduction in the ductility and toughness of steel at high temperatures, making it prone to thermal cracking. 3 Impact on welding properties: Nitrogen reduces the welding properties of steel, increasing the risk of cracks during welding. 1.4 Reduction in corrosion resistance: When the mass fraction of nitrogen exceeds 0.16%, it deteriorates the steel’s oxidation resistance, thereby affecting its corrosion resistance. 02 Positive effects 2.1 Increased strength: Nitrogen can significantly enhance the strength of steel, due to the solid solution strengthening effect resulting from nitrogen dissolved in ferrite. 2.2 Refining grain structure: Nitrogen can form fine, dispersed nitrides with elements such as aluminum (Al), vanadium (V), titanium (Ti), and niobium (Nb) in steel; these nitrides help to refine the grain structure of the steel, thereby enhancing its strength and toughness. 2.3 Stable austenite: Nitrogen is a very effective element for forming and stabilizing austenite, with an effectiveness roughly 20 times that of nickel. To a certain extent, nitrogen can replace some nickel in steel, thereby reducing costs. 03 Applications and Control 3.1 Applications: Nitrogen is widely used in the steel industry, such as in nitrided quenched and tempered steels, ordinary low-alloy steels, stainless and acid-resistant steels, as well as heat-resistant steels that do not develop scale. Especially in heat-resistant, skinless steel, the use of nitrogen can improve the creep strength and high-temperature endurance strength of the steel. 3.2 Control: Since nitrogen has a dual effect on the properties of steel, it is necessary to strictly control its content during the steel production process. It is generally specified that the nitrogen content should not exceed 0.018% to ensure that the properties of the steel meet the requirements for use. In certain special cases, such as in the production of heat-resistant, non-peeling steel, the nitrogen content can be increased appropriately, but it also needs to be strictly controlled to avoid adverse effects. 04 Summary: The impact of nitrogen on the properties of steel is multifaceted, with both favorable and unfavorable effects. In the steel production process, it is necessary to control the nitrogen content appropriately based on specific application requirements and process conditions, in order to maximize its beneficial effects and avoid any adverse effects.