Martensitic stainless steel, as a type of stainless steel that can use heat treatment to adjust material properties, is actually a type of stainless steel that can be hardened. Martensitic stainless steel is characterized by high hardness, strong mechanical and anti-rust properties. These characteristics determine that martensitic stainless steel must have two basic conditions. One is that there must be an austenite phase zone in the equilibrium phase diagram. , Secondly, in order for martensitic stainless steel to form a passivation film with strong corrosion resistance, the martensitic stainless steel must have a chromium content of more than 10.5%.

According to the differences in alloy elements in martensitic stainless steel, martensitic stainless steel can be divided into martensitic chromium stainless steel and martensitic chromium-nickel stainless steel. Martensitic chromium stainless steel is also divided into three types: low carbon, medium carbon and high carbon. Martensitic stainless steel has a body-centered tetragonal crystal structure in the quenched state. The material is ferromagnetic and has corrosion resistance in weakly corrosive environments. The chromium content in martensitic stainless steel can reach up to 18%, and the carbon can be greater than 1.2%.

In order to enhance the corrosion resistance of martensitic stainless steel materials and the sharpness of cutting tools, excess carbides can exist in the structure. In order to optimize the tempering effect after quenching, niobium, silicon, tungsten and vanadium can be added in appropriate amounts. Nickel-containing martensitic stainless steel optimizes the corrosion resistance of chromium martensitic stainless steel in certain media and enhances the toughness of the material. Carbon in martensitic stainless steel is an indispensable and important element. It can make the iron-chromium binary alloy elements form a phase zone, which also affects the hardness of martensitic stainless steel in the quenched state.

Tests have shown that the hardness value of martensitic stainless steel with 0.1% carbon is about 35HRC, and the hardness value of martensitic stainless steel with 0.5% carbon can be higher than 60HRC. However, if the carbon element is increased further, the material hardness will not be significantly improved.

Domestic standards include a total of 18 martensitic stainless steel grades, basically two types: 13% chromium and 17% chromium.

Martensitic stainless steel has been widely used in various industrial fields because of its excellent mechanical properties, moderate corrosion resistance and good heat resistance below 650°C. Low-carbon and medium-carbon martensitic stainless steels, such as 1Gr13 and Its improved version is mainly used in steam turbines, jet engines, gas turbines and other fields. Such materials are also widely used in the petroleum and petrochemical industries.

Martensitic stainless steels such as slightly higher carbon 2Gr13 are mainly used for cutting tools, valve parts, gears, pulleys, switch shafts and other mechanical parts, rods and rollers. The application fields of high carbon martensitic stainless steel such as 9Gr18Mo include knives, bearings, surgical and dental instruments, scissors, springs, valves, shafts, cams, etc.

The temper brittleness temperature range of martensitic stainless steel occurs between 425-565°C. At this temperature, the impact toughness of tempered steel will be significantly reduced. For parts that require impact resistance, tempering at this temperature should not be used and should be avoided at this temperature. applied within the scope.