High-alloy 18Ni(300) Martensitic Age-hardening Steel F141/C300 - Features and Environmental Applications
18Ni300 mold steel is a low carbon, martensitic时效hardening plastic mold steel. The alloy elements that play a role in the时效hardening process are titanium, aluminum, cobalt, and molybdenum. The carbon content is low by mass fraction (about 0.03%), aimed at improving the steel's toughness. Impurities have a significant impact on the properties of martensitic时效hardening steel, with a more pronounced effect on steel with higher yield strength. This necessitates vacuum melting for this type of steel, to reduce impurities, segregation, and gas content in the ingots, ensuring the steel has good toughness and fatigue resistance.
Chemical Composition:
C ≤0.03
Ti 0.5-0.8
Mn ≤0.10
P ≤0.01
S ≤0.01
Co 8.5-9.5
Mo 4.6-5.2
Ni 18.0-19.0
Primary Application:
1) Primarily used for precision forging dies.
2) Produce high-precision, ultra-polished, complex mold cavities, large cross-sections, and mass-produced plastic molds.
Martensitic Age-Hardening Steel 18Ni(200) Ultra-Low Carbon Steel 18Ni(250) Mold Steel 18Ni(300) Chemical Composition 18Ni(350) Mechanical Properties Heat Treatment
Properties and Applications of 18Ni Martensitic Age-Hardening Steel:
Representative steel grades of 18Ni steel include 022Ni18Co8Mo3TiA [18Ni(200)], 022Ni18Co8Mo5TiA [18Ni(250)], 022Ni18Co9Mo5TiA [18Ni(300)], and 00Ni18Co13Mo4TiA [18Ni(350)].
18Ni steel is a typical martensitic age-hardening steel with a low carbon content. The alloy elements Ti, Al, Co, and Mo are responsible for the age-hardening effect, and impurities have a significant impact on the properties of martensitic age-hardening steel, with a more pronounced effect on steels with higher yield strength. This necessitates vacuum melting for such steel to reduce impurities, segregation, and gas content in the ingot, ensuring the steel possesses good toughness and fatigue resistance.
In 18Ni steel, carbon significantly affects the strength, even with a minimal carbon content, it can significantly increase the martensite strength. However, once the carbon mass fraction is increased to 0.03%, it will decrease the yield strength of the steel. Therefore, the carbon mass fraction in 18Ni maraging steel should not exceed 0.03%.
Sulfur in 18Ni steel is harmful. It exists in the form of sulfides within the steel, distributed along the hot rolling direction, causing anisotropy in the steel. Therefore, it is required to minimize the sulfur content in the steel as much as possible.
Alloyed with a high content of Ni in 18Ni steel, the primary role is to ensure the formation of a single martensite after solution heat treatment. Secondly, Ni's effect on Mo is to form the age-hardening phase Ni3Mo. When the Ni mass fraction exceeds 10%, it also enhances the fracture toughness of the martensitic age-hardening steel.
After solution heat treatment, 18Ni 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, the hardness can increase to 50HRC. This type of steel maintains good ductility and high fracture toughness under conditions of high strength and toughness. Additionally, it does not undergo cold work hardening, has minimal deformation during aging heat treatment, excellent weldability, and can be subjected to nitriding on the surface.
18Ni class low carbon martensitic时效 steel is primarily used for manufacturing high-precision, ultra-smooth surface, complex mold cavity, large cross-section mechanical parts and plastic molds for mass production. However, due to its high cost, its usage is limited.
