Characteristics and uses of martensitic aging steel:
The representative steel grades of Maraging include：
- 022Ni18Co8Mo3TiA (Maraging200)
- 022Ni18Co8Mo5TiA (Maraging250)
- 022Ni18Co9Mo5TiA (Maraging300)
- 00Ni18Co13Mo4TiA (Maraging350)
Maraging steel is a typical martensitic age hardening steel with a low carbon content. The alloying elements that play a role in age hardening are Ti, Al, Co, and Mo. Impurities have a significant impact on the properties of martensitic age hardening steel, with a more significant impact on steel with higher yield strength. This requires this type of steel to undergo vacuum smelting to reduce impurities, segregation, and gas content in the ingot, in order to ensure that the steel has good toughness and fatigue resistance.
In Maraging steel, carbon has a significant impact on the strength of the steel, and even with very little carbon content, it can significantly increase the strength of the martensite. However, increasing the mass fraction of carbon to 0.03% will also reduce the yield strength of the steel, so the mass fraction of carbon in Maraging martensitic aging steel should not exceed 0.03%.
The S in Maraging steel is harmful. S exists in the steel as sulfides and is distributed along the hot rolling direction, resulting in anisotropy of the steel. Therefore, it is required to minimize the sulfur content of the steel as much as possible.
The addition of a large amount of Ni to Maraging steel mainly ensures that a single martensite can be obtained after solid solution quenching. Secondly, the effect of Ni on Mo is to form the aging strengthening phase Ni3Mo. When the mass fraction of Ni exceeds 10%, it can also improve the fracture toughness of martensitic aging steel.
After solid solution, Maraging steel forms ultra-low carbon martensite with a hardness of 28-30HRC; After aging treatment, due to the precipitation of various types of intermetallic compounds, aging hardening can be achieved, and the hardness can increase to 50HRC. This type of steel still has good toughness and high fracture toughness under high strength and toughness conditions. At the same time, this type of steel has no cold work hardening, small deformation during aging heat treatment, good weldability, and can also be nitrided on the surface.
Maraging low-carbon martensitic aging steel is mainly used for manufacturing high-precision, ultra mirror, complex cavity, large cross-section, and large-scale production of mechanical parts and plastic molds. However, due to its high price, its use is limited.
