440C Stainless Steel Sheet

440C stainless steel is a high-carbon martensitic stainless steel known for its excellent hardness, wear resistance, and corrosion resistance. It exhibits superior strength and toughness properties compared to other grades in the 400 series stainless steels. 440C is commonly used in applications requiring high hardness and abrasion resistance, such as bearings, cutting tools, and surgical instruments.

Mechanical Properties

Hardness

440C stainless steel plate exhibits relatively high hardness in its untreated state, making it one of the harder grades among stainless steels. For applications such as cutting tools and bearings, the recommended hardness after heat treatment is HRC 57-59. With deep cryogenic treatment, hardness can reach around HRC 60. In the annealed condition, the hardness is ≤ 269 HB, while after quenching and tempering, it is ≥ 633 HV.

Strength

The mechanical properties include an internal stress of 250 N/mm², tensile strength of 560 N/mm², elongation (EL) of 18%, and Brinell hardness (HB) of 250.

Toughness

440C stainless steel exhibits strong toughness, which, along with its corrosion resistance, makes it widely used in applications that require a combination of multiple properties, such as the manufacturing of high-quality cutting tools.

Fabrication Characteristics

Grinding Properties

When grinding 440C, it tends to have a high degree of stickiness and heats up quickly. It is recommended to use chrome corundum or microcrystalline corundum wheels for grinding.

Other Properties

Corrosion Resistance

440C stainless steel has strong corrosion resistance, making it suitable for manufacturing bearing components that operate in corrosive environments and under strong oxidative atmospheres without lubrication. Its corrosion resistance is attributed to its high chromium content. Additionally, due to its corrosion resistance and high strength, it is used in various fields, including chemical equipment, food processing equipment, medical devices, and marine applications.

Magnetism

440C stainless steel is magnetic, which is a typical characteristic of martensitic stainless steels.

1. Knife Manufacturing

440C stainless steel is commonly used in the production of high-quality knives, including surgical scalpels and scissors. Its blade components benefit from 440C's hardness and corrosion resistance. After quenching, 440C achieves a higher hardness than 440A steel, and deep cryogenic treatment is often employed in the heat treatment process for knife production.

2. Bearing Manufacturing

This steel is primarily used to manufacture bearing components that operate in corrosive environments and under strong oxidative atmospheres without lubrication. 440C exhibits good high-temperature dimensional stability, making it suitable as a corrosion-resistant high-temperature bearing steel.

3. Other Applications

440C stainless steel is also utilized in the production of turbine blades, nozzle bodies, valves, rulers, and cutlery (such as knives and scissors). Its applications extend to various fields, including metal products, precision electronics, elevators, and food processing machinery. Additionally, it is used in chemical equipment, medical devices, marine applications, as well as in the manufacturing of pneumatic valves and molds.

1. Annealing

The annealing temperature for 440C stainless steel is between 800 - 920°C with slow cooling. The resulting microstructure after annealing is martensitic.

2. Quenching

Quenching is performed at temperatures ranging from 1010 - 1070°C, followed by oil cooling.

3. Tempering

Tempering is conducted at temperatures between 100 - 180°C with rapid cooling. For applications where 440C is used as stainless bearing steel, it is generally recommended to perform deep cryogenic treatment before the tempering operation. This deep cryogenic treatment can enhance the hardness of the steel, improve wear resistance, and increase dimensional stability.

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