What are the differences between different heat treatment processes?

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01 What is heat treatment? Heat treatment is a method by which I improve the performance of a workpiece by altering its internal microstructure or the chemical composition of its surface. 01 When is heat treatment needed? After the customer places an order, the sawing workshop cuts the die steel to the desired dimensions based on the customer’s requirements, and then it is sent to the machining department where a series of grinding or milling operations are carried out. Heat treatment is carried out at the factory on the molds after rough shaping, based on specific requirements; different heat treatment processes are selected according to the properties of the materials used. 01 Classification of heat treatment processes: The heat treatment processes we are discussing today include quenching, tempering, nitriding, cryogenic treatment, oxidation, and other such processes. So what do all these processes mean? The answer is revealed below~ I. Quenching 1. What is quenching? A heat treatment process in which steel is austenitized and then cooled at an appropriate cooling rate, causing the workpiece to undergo a transformation into unstable microstructural phases such as martensite throughout its cross-section or within a certain area. 2. What is the purpose of quenching? 1) Improve the mechanical properties of the metal products or components. For example: improving the hardness and wear resistance of tools, bearings, etc., increasing the elastic limit of springs, and enhancing the overall mechanical properties of shaft components. 2) Improve the material or chemical properties of certain special steels. Such as improving the corrosion resistance of stainless steel and enhancing the permanent magnetism of magnetic materials. II. Tempering 1. What is tempering? A heat treatment process in which the quenched workpiece is heated to an appropriate temperature below the critical point AC1 and held there for a certain period of time, after which it is cooled using suitable methods in order to achieve the desired microstructure and properties. 2. What is the purpose of tempering? 1) Reduce internal stress and decrease brittleness. Quenched parts have high levels of stress and brittleness; if they are not tempered in a timely manner, they may deform or even crack. 2) Adjusting the mechanical properties of the workpiece: After quenching, the workpiece has high hardness but is also brittle. To meet the various performance requirements of different workpieces, tempering can be used to adjust their hardness, strength, plasticity, and toughness. 3) Stabilize the workpiece dimensions. Tempering can stabilize the microstructure to ensure that no further deformation occurs during subsequent use. 4) Improve the machinability of certain alloy steels. III. Nitridation 1. What is nitridation? Nitriding is a chemical heat treatment process in which nitrogen atoms are diffused into the surface layer of a workpiece at a certain temperature in a specific medium. 2. What is the purpose of nitridation? It endows the product with excellent wear resistance, fatigue resistance, corrosion resistance, and high-temperature resistance. Nitriding is a chemical heat treatment process in which nitrogen atoms are diffused into the surface layer of a workpiece at a certain temperature in a specific medium. IV. Cryogenic Treatment 1. What is cryogenic treatment? Deep cryogenic treatment involves treating metals at temperatures below -160°C, thereby converting almost all of the soft residual austenite into high-strength martensite. 2. What is the purpose of cryogenic treatment? Eliminating residual austenite – after quenching and tempering, the amount of residual austenite is around 8-20%. Since austenite is very unstable, it tends to transform into martensite when subjected to external forces or changes in ambient temperature. Martensite has a larger volume than austenite, which leads to irregular expansion of the material and reduces the dimensional accuracy of the workpiece. Deep cooling reduces the amount of residual austenite to below 2%, thereby reducing residual stresses, stabilizing the metal matrix, increasing the strength and toughness of the metal material, and significantly enhancing its red hardness. V. Oxidation What is oxidation? Steel parts undergo oxidation treatment to form a dense, protective oxide film on their surface; its main component is magnetic iron oxide (Fe3O4), which provides anti-adhesion properties. The FeS film obtained through surface sulfidation offers both anti-friction and anti-adhesion effects. It can also improve resistance to etching and high-temperature oxidation. 01 What are the differences between workpieces with different processes? Guys, do you still not quite understand the few processes mentioned above? So, Xiao Ao will show you visually what the differences are between products made using different manufacturing processes 1. Quenched and tempered: the color is grayish-blue. 2. Deeply cooled: there is a white frost on the surface, and it cannot be touched directly with the hand. 3. Nitrided: the surface is whiteish or grayish; for example, a mold that could originally produce only 10,000 samples can now, through heat treatment to increase its hardness, produce 100,000 or even 1,000,000 samples, thereby greatly improving efficiency.