Nouns Related To Heat Treatment Of Steel

1. Annealing of steel

Heating steel to a certain temperature, holding it warm for a period of time, and then allowing it to cool slowly is called annealing. Annealing of steel is a heat treatment method in which the steel is heated to a temperature where phase change or partial phase change occurs, and then slowly cooled after heat preservation. The purpose of annealing is to eliminate structural defects, improve the structure, homogenize the components and refine the grains, improve the mechanical properties of the steel, reduce residual stress; at the same time, it can reduce the hardness, improve the plasticity and toughness, and improve the cutting performance. Therefore, annealing is not only to eliminate and improve the structural defects and internal stress left by the previous process, but also to prepare for the subsequent process. Therefore, annealing is a semi-finished product heat treatment, also known as pre-heat treatment.2. Normalizing steelNormalizing is a heat treatment method in which the steel is heated above the critical temperature to transform all the steel into uniform austenite, and then cooled naturally in the air. It can eliminate the network cementite of hypereutectoid steel. For hypoeutectoid steel, normalizing can refine the crystal lattice and improve the comprehensive mechanical properties. It is more economical to use normalizing instead of annealing for parts with low requirements.3. Quenching of steelQuenching is to heat the steel to above the critical temperature, keep it warm for a period of time, and then quickly put it into the quenching agent to cause the temperature to drop suddenly and cool rapidly at a speed greater than the critical cooling rate to obtain an imbalance dominated by martensite. Methods of heat treatment of tissues. Quenching can increase the strength and hardness of steel but reduce its plasticity. Commonly used quenching agents in quenching include: water, oil, alkaline water and salt solution, etc.4. Tempering of steelReheating the quenched steel to a certain temperature and then cooling it using a certain method is called tempering. Its purpose is to eliminate the internal stress generated by quenching and reduce the hardness and brittleness to obtain the expected mechanical properties. Tempering is divided into three categories: high temperature tempering, medium temperature tempering and low temperature tempering. Tempering is often used in conjunction with quenching and normalizing.⑴Quenching and tempering treatment: The heat treatment method of high-temperature tempering after quenching is called quenching and tempering treatment. High temperature tempering refers to tempering between 500-650℃. Quenching and tempering can greatly adjust the properties and materials of steel. Its strength, plasticity and toughness are all better, and it has good comprehensive mechanical properties.⑵Aging treatment: In order to eliminate changes in size and shape of precision measuring tools, molds, and parts during long-term use, the workpiece is often reheated to 100-150°C after low-temperature tempering (low-temperature tempering temperature 150-250°C) and before finishing. ℃, keep it for 5-20 hours. This treatment to stabilize the quality of precision parts is called aging. It is particularly important to perform aging treatment on steel components under low temperature or dynamic load conditions to eliminate residual stress and stabilize the steel structure and size.

5. Surface heat treatment of steel⑴Surface quenching: The surface of the steel part is rapidly heated to above the critical temperature, but the heat is quickly cooled before it can be transferred to the core. In this way, the surface layer can be quenched in the martensitic structure, and the core does not undergo quenching. Phase transformation, which achieves the purpose of surface hardening without changing the core, and is suitable for medium carbon steel.⑵Chemical heat treatment: refers to the penetration of atoms of chemical elements into the surface layer of the workpiece by virtue of the ability of atomic diffusion at high temperatures to change the chemical composition and structure of the surface layer of the workpiece, thereby making the surface layer of the steel have specific properties. A heat treatment process that requires the organization and properties. According to the types of infiltrated elements, chemical heat treatment can be divided into four types: carburizing, nitriding, cyanidation and metal infiltration.Carburizing: Carburizing is the process of penetrating carbon atoms into the surface layer of steel. It also makes the low carbon steel workpiece have a surface layer of high carbon steel, and then undergoes quenching and low temperature tempering to make the surface layer of the workpiece have high hardness and wear resistance, while the central part of the workpiece still maintains the toughness and toughness of low carbon steel. Plasticity.Nitriding: Also known as nitriding, it is the process of penetrating nitrogen atoms into the surface layer of steel. Its purpose is to improve the hardness and wear resistance of the surface layer as well as improve fatigue strength, corrosion resistance, etc. At present, gas nitriding method is mostly used in production.Cyanidation: Also known as carbonitriding, it refers to the process of simultaneously infiltrating carbon atoms and nitrogen atoms into steel. It makes the steel surface carburized and nitrided.Metal penetration: refers to the process of penetrating metal atoms into the surface layer of steel. It alloys the surface layer of steel so that the surface of the workpiece has certain characteristics of alloy steel and special steel, such as heat resistance, wear resistance, oxidation resistance, corrosion resistance, etc. Commonly used in production include aluminizing, chromizing, boronizing, siliconizing, etc.