SUS440C Stainless Steel
—High Hardness and High Toughness Stainless Steel
What is SUS440C material?
A: SUS440C stainless steel is a Japanese steel grade, known as a high-hardness and high-toughness stainless mold steel. The imported SUS440C material contains chromium content as high as 16%-18%, making it excellent in corrosion resistance and high-strength toughness. It is widely used in surgical knives and the shipbuilding industry, and is currently a common stainless mold steel in the high-end knife market. With the development of sub-zero treatment processes, the toughness of SUS440C steel has been significantly enhanced. During grinding, the drawback of SUS440C stainless steel is its high viscosity and rapid heat generation, but it is easier to grind than any other carbon steel.
What does the "C" in SUS440C mean?
A: The letter "C" in SUS440C steel represents the carbon content. The 440 series stainless steel includes 440A, 440B, 440C, and 440F. 440A has a carbon content of C-0.75%, 440B has C-0.9%, and both 440C and 440F have a carbon content of C-1.2%.
What are the characteristics of the chemical composition and properties of SUS440A, SUS440B, SUS440C, and SUS440F stainless steels?
A: SUS440A, SUS440B, SUS440C, and SUS440F all belong to martensitic stainless steels. The chemical composition of martensitic stainless steels is characterized by carbon content ranging from 0.1% to 1.2% and chromium content from 12% to 27%, with possible additions of molybdenum, tungsten, vanadium, niobium, and other elements. Due to their body-centered cubic structure, their strength decreases rapidly at high temperatures. However, below 600°C, they exhibit the highest high-temperature strength among all stainless steels and also have the highest creep strength. Among stainless steels, SUS440A has the best rust resistance, while SUS440C has the lowest.
SUS440A has excellent hardening properties after quenching and higher toughness compared to SUS440B and SUS440C steels.
SUS440B has excellent wear resistance, higher hardness than SUS440A steel, and higher toughness than SUS440C steel.
SUS440C has the highest hardness among all stainless and heat-resistant steels.
SUS440F is a steel grade developed to improve the machinability of SUS440C.
Does SUS440C material have magnetism before and after heat treatment? Can it be attracted by a magnet?
A: Heat treatment changes the hardness of the steel but does not alter its inherent material properties. Generally, stainless steel is not attracted by magnets, but SUS440C stainless steel bars belong to martensitic stainless steel. Their metallographic structure is martensitic, giving them ferromagnetic properties. Therefore, they can be attracted by magnets both before and after heat treatment. Among stainless steels, only austenitic stainless steels are paramagnetic, meaning they are not attracted by magnets.
