18Ni (200) is an maraging steel with a high yield-strength ratio, good cutting processability and welding performance. The hardness can be significantly improved through aging treatment. Low-cobalt, cobalt-free, and low-nickel maraging steel reduces costs, and low-alloy age-hardened steels such as 25CrNi3MoAl steel and PMS steel also have excellent properties. These steels play an important role in mold manufacturing and will continue to develop in the future.

18Ni (200) is an age-hardening plastic mold steel whose chemical composition includes carbon, silicon, manganese, molybdenum, nickel, cobalt, titanium and aluminum. This kind of steel has the characteristics of two categories: maraging hardening steel and precipitation (precipitation) hardening steel. Among them, maraging steel is favored because of its high yield-to-strength ratio, good machinability and welding performance, and simple heat treatment process.

Take 18Ni (200) as an example, which is a typical high-alloy maraging hardening steel. After solution treatment, it can form ultra-low carbon martensite with a hardness of about 30~32HRC. However, after aging treatment, its hardness can significantly increase to above 50HRC due to the desorption and precipitation of various types of intermetallic compounds. This kind of steel still maintains good plasticity, toughness and high fracture toughness under the conditions of high strength and high toughness, making it an ideal choice for manufacturing high-strength and high-toughness molds.

In order to reduce material costs, low-cobalt, cobalt-free, and low-nickel maraging steels have been developed in recent years, such as 06Ni (06Ni6CrMoVTiAl) steel and AFC-77 (1Cr14Co13Mo5V) steel. These steels reduce the content of cobalt and nickel while maintaining excellent properties, thereby effectively reducing manufacturing costs.

In addition, there is also a type of low-alloy age-hardened steel, such as 25CrNi3MoAl steel and PMS (1Ni3MnMoCuAl) steel developed by my country. After solution treatment, the hardness of these steels is about 30HRC. After aging treatment, the hardness can rise to 38~42HRC due to the precipitation of the intermetallic compound Ni3Al. If nitriding treatment is performed, the surface hardness of the mold can reach about 110HV, further improving the wear resistance and service life of the mold.

In summary, 18Ni (200) and its related age-hardening plastic mold steels play an important role in the mold manufacturing industry with their excellent properties and wide range of applications. As technology continues to advance and costs decrease, these steels will continue to have greater potential in the future.