A387 Gr.91 steel chemical elements

A387 Gr.91 (A387 Grade 91) steel is a chromium-molybdenum alloy steel, which can be used in large nuclear power plants. The Chromium-Molybdenum combination gives these plates corrosion-combating skills along with an enhanced tensile strength at raised temperatures.
The influence of five elements in A387 Gr.91 steel on the function of steel plate:
A387 Gr.91 steel consists of chromium, molybdenum, manganese, silicon, etc. which moulds them into stronger, harder, heat tolerant and weldable.
a. Carbon (C): When the carbon content of the steel is added, the yield point and tensile strength increase, but the plasticity and impact resistance decrease. When the carbon content exceeds 0.23%, the welding function of the steel deteriorates, so it is used for welding Low-alloy structural steel, the carbon content generally does not exceed 0.20%. High carbon content will also reduce the steel's ability to resist atmospheric corrosion. High-carbon steel in open yards is prone to corrosion; in addition, carbon can add steel's cold brittleness and aging sensitivity. 
 
b. Silicon (Si): Silicon is added as a reducing agent and deoxidizer in the steelmaking process, so the killed steel contains 0.15-0.30% silicon. If the silicon content in the steel exceeds 0.50-0.60%, silicon is considered as an alloy element. Silicon can significantly improve the elastic limit, yield point and tensile strength of steel, so it is widely used as spring steel. Joining 1.0-1.2% of silicon in quenched and tempered structural steel, the strength can be improved by 15-20%. The combination of silicon and molybdenum, tungsten, chromium, etc., has the effect of improving corrosion resistance and oxidation resistance, and can be made into heat-resistant steel. Low-carbon steel containing 1-4% silicon, with extremely high magnetic permeability, is used for silicon steel sheet in the electrical industry. Addition of silicon will reduce the welding function of steel.
c. Manganese (Mn): In the steelmaking process, manganese is an outstanding deoxidizer and desulfurizer. Generally, manganese in steel contains 0.30-0.50%. Even if it is more than 0.70% in carbon steel, it is regarded as "manganese steel". Compared with the general steel, it not only has satisfactory resistance, but also has higher strength and hardness, improves the hardenability of the steel, and improves the hot working function of the steel. For example, 16Mn steel is 40% higher than the A3 compliance point. The steel containing 11-14% of manganese has extremely high wear resistance, and is used for excavator buckets, ball mill lining boards, etc. Increasing the amount of manganese reduces the corrosion resistance of steel and reduces the welding function.
d. Phosphorus (P): Under general conditions, phosphorus is a harmful element in steel. Adding the cold brittleness of steel deteriorates the welding function, reduces the plasticity, and deteriorates the cold bending function. Therefore, the phosphorus content in steel is generally required to be less than 0.045%, and the requirements for high-quality steel are lower.
e. Sulfur (S): Sulfur is also a harmful element under normal conditions. It makes the steel hot brittle, reduces the ductility and resistance of the steel, and forms cracks during casting and rolling. Sulfur is also tarnished to the welding function, which reduces the corrosion resistance. Therefore, sulfur content is generally required to be less than 0.055%, and high-quality steel is required to be less than 0.040%. The participation of 0.08-0.20% sulfur in steel can improve the machinability, and is generally called free-cutting steel.

A387 Gr 91 plates heat treatment: normalizing + tempering.
 

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