440C steel is the most representative grade in the high-carbon high-chromium martensitic stainless steel system. With its unique composition design and heat treatment potential, it has become a core material in the industrial field that balances wear resistance and corrosion resistance. In its core composition, the carbon content is stably controlled in the range of 0.95%~1.20%, and the chromium content reaches 16.00%~18.00%. This ratio allows the hardness of 440C steel to easily exceed 58HRC after quenching and tempering, making it a material in the first echelon of hardness performance among all martensitic stainless steels.
The density of 440C steel remains in a moderate range of 7.7~7.8g/cm³. This density characteristic enables it to achieve an excellent balance between lightweight requirements and structural strength. It will not increase the extra load of precision components due to excessively high density, nor will it affect the overall rigidity due to insufficient density. The annealed hardness of 440C steel is ≤269HB. In this state, it can smoothly complete cutting, turning and progressive grinding. The recommended cutting speed of 440C steel is controlled at 30-50m/min to obtain excellent machined surface quality.
The heat treatment process system of 440C steel is mature and stable. After annealing at 800~920℃ and slow cooling, 440C steel can obtain the best machinability. After oil quenching in the range of 1010~1070℃, the martensite of 440C steel can be fully transformed. Then, after low-temperature rapid cooling and tempering at 100~180℃, the final hardness of 58~62HRC can be locked. The dispersed M23C6 type carbides in 440C steel are the core source of its ultra-high wear resistance. The higher the austenitizing temperature of 440C steel, the higher its corrosion resistance will be.
The application scenarios of 440C steel cover many high-end manufacturing fields. It is the preferred material for bearing parts in corrosive environments and non-lubricated strong oxidizing atmospheres. With its excellent high-temperature dimensional stability, 440C steel can also serve as a corrosion-resistant high-temperature bearing steel for a long time. 440C steel can be processed into high-end tool parts such as medical scalpels, precision scissors and industrial nozzles. The high-precision aerospace bearings and valve core parts made of 440C steel can still maintain long-term stable operation under high friction conditions. The derivative grade 440F in the same series of 440C steel further optimizes the machinability and can adapt to the efficient continuous processing of automatic lathes. The full-spectrum performance coverage of the 440C steel family makes 440C steel an irreplaceable core metal material in industrial manufacturing.