Chemical Composition of Martensitic Chromium Stainless Steel 7Cr17(440A), 8Cr17(440B), 11Cr17(440C)

Chromium Martensitic stainless steel 7Cr17 (440A), 8Cr17 (440B), and 11Cr17 (440C) are all martensitic stainless steels commonly used for cutlery, solenoid valves, specialty instruments and medical tools. All of them are characterized by good corrosion resistance, wear resistance, toughness, and high temperature strength.

7Cr17 (440A)

7Cr17 (440A) is the most commonly used martensitic steel in cutlery. It contains 7% chromium and possesses a great balance of hardenability and corrosion resistance. Among all the martensitic grades, 7Cr17 (440A) has the least amount of carbon in it. The chemical composition of 7Cr17 (440A) is as follows:

Element contents (%) by weight

Carbon (C) -- 0.65 – 0.75

Manganese (Mn) -- 0.60 - 1.00

Phosphorus (P) -- ≤ 0.035

Sulfur (S) -- ≤ 0.030

Silicon (Si) -- 0.60 - 1.00

Chromium (Cr) -- 16.00 - 18

Molybdenum (Mo) -- 0.75

Nickel (Ni) -- ≤ 0.50

8Cr17 (440B)

8Cr17 (440B) is the second most commonly used martensitic steel for cutlery. Compared to 7Cr17 (440A), 8Cr17 (440B) has slightly higher carbon content and higher corrosion resistance. 8Cr17 (440B) contains 8% chromium and its chemical composition is listed below:

Element contents (%) by weight

Carbon (C) -- 0.75 - 0.95

Manganese (Mn) -- 0.6 - 1.00

Phosphorus (P) -- ≤ 0.040

Sulfur (S) -- ≤ 0.030

Silicon (Si) -- 0.60 - 1.00

Chromium (Cr) -- 16.00 - 18

Molybdenum (Mo) -- 0.75

Nickel (Ni) -- ≤ 0.50

11Cr17 (440C)

11Cr17 (440C) is the most commonly used martensitic steel in cutlery, however it is not as popular as the above two steels because of the higher cost. 11Cr17 (440C) has higher carbon content than 7Cr17 (440A) and 8Cr17 (440B), which gives it superior hardness and wear resistance. 11Cr17 (440C) contains 11% chromium and its chemical composition is listed below:

Element contents (%) by weight

Carbon (C) -- 0.95 - 0.95

Manganese (Mn) -- 0.7 - 1.00

Phosphorus (P) -- ≤ 0.040

Sulfur (S) -- ≤ 0.030

Silicon (Si) -- 0.8 - 1.00

Chromium (Cr) -- 16.00 - 18

Molybdenum (Mo) -- 0.75

Nickel (Ni) -- ≤ 0.50

All of the above martensitic stainless steel grades have similar physical and mechanical properties, including high hardness, toughness, wear resistance, and corrosion resistance. However, the higher carbon content of 11Cr17 (440C) gives it superior hardness and wear resistance compared to the other two grades. These steels can be heat treated to achieve different properties, such as enhanced toughness or improved wear resistance.

The martensitic stainless steel grades 7Cr17 (440A), 8Cr17 (440B), and 11Cr17 (440C) are all popular steels for cutlery, solenoid valves, specialty instruments, and medical tools. They offer good corrosion resistance, wear resistance, toughness, and strength at elevated temperatures. Due to their superior properties, they are widely used in various applications.

7Cr17(440A), 8Cr17(440B) and 11Cr17(440C) are martensitic stainless steels, belonging to the family of steel containing high levels of chromium.

7Cr17, commonly known as 440A, is the basic martensitic stainless steel, containing 17% chromium, 0.15% carbon and 0.60% manganese. This steel, though rarely used in its pure form, is frequently used in combination with other elements to improve its properties and produce a wide range of grades with high corrosion resistance properties.

8Cr17, commonly known as 440B, is a higher carbon version of 7Cr17, containing 14.5-16%chromium -0.75%-1.20% carbon and 0.60% manganese. It possesses more improved corrosion resistance and wear resistance compared with 7Cr17 and it is commonly used in such applications as valve bodies, pumps and fasteners.

11Cr17, commonly known as 440C, is the higher carbide stainless steel containing 16-18% chromium, 0.95-1.20% carbon and 0.60% manganese. It contains more carbide and provides the highest hardness and wear resistance of the 440 series. It is extensively used in the production of knives, measuring instruments and medical tools.

All the three steels are magnetic and have distinct differences in their microstructures, which allows them to be used for different applications based on their advantage characteristics.