The Microstructures and Nonmetallic Inclusion of Heat Treatment AISI420 Stainless Steel
The AISI420 stainless steel, also known as X30Cr13, is a martensitic steel with a relatively high carbon content and contains a small amount of chromium, molybdenum and some other elements. According to the AISI 420 datasheet, the heat treatment of AISI420 stainless steel has a great influence over its mechanical properties, relative hardness and microstructures. Therefore, understanding the microstructures and nonmetallic inclusion of heat treatment AISI420 stainless steel is important.
First of, AISI420 martensitic stainless steel is usually annealed, normalized and hardened through various heat treatment processes. I annealing, AISI420 stainless steel is heated up to 1000℃ - 1250℃, followed by cooling in air or oil depending on the requirements. During the annealing process, the microstructure is full of retained austenite, which has a low hardness and good workability, this is suitable for applications that need high tensile properties, such as aircraft parts or medical equipment. Secondly, the normalized AISI420 stainless steel has a slightly higher hardness than the annealing material, but their workability is similar; The normalized austenite is stable and the martensite structure increases, so it has higher strength and toughness, suitable for parts that need enhanced toughness such as cold-working tools. Thirdly, hardening is the most common heat treatment method for AISI420 stainless steels. The material undergoes quenching, tempering and other processes to obtain a higher hardness and strength than the annealing material. Therefore, hardening is suitable for cutlery and tools that require high hardness and wear resistance.
The nonmetallic inclusion in AISI420 stainless steel can also considered a result of the heat treatment process, which can affect the mechanical properties of AISI420 stainless steels. Nonmetallic inclusions can be divided into three categories: oxide particles, oxysulfide particles, and sulfide particles. Oxide particles, such as alumina and silicate particles, are formed by the oxidation of the steel during the annealing process, which is why oxide particles are the most common nonmetallic inclusions in annealing AISI420 steels. Oxysulfide particles and sulfide particles, on the other hand, are formed by reactions of the molten steel with other elements such as nitrogen during the steelmaking process, and are most common in normalized AISI420 steels. These particles can affect the mechanical properties of the steel in various ways, such as reducing its impact toughness, compressive strength and ductility, and increasing its susceptibility to sulfide stress cracking. Therefore, these nonmetallic inclusions need to be controlled to a certain extent, rather than eliminated completely, in order to optimize the mechanical properties of AISI420 stainless steel.
In conclusion, AISI420 stainless steel is a martensitic stainless steel with a relatively high carbon content. It can be heat treated to change its hardness and strength by annealing, normalizing, and hardening. The microstructure and nonmetallic inclusion of heat-treated AISI420 stainless steel changes due to the heat treatment process and this affects the mechanical properties of the steel. Therefore, it is important to understand the changes in the microstructure and nonmetallic inclusion of heat-treated AISI420 stainless steel.
