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Zhongchi
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Zhongchi
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| Bulk heat treatment | A heat treatment process involving the penetration heating of metallic materials or workpieces. |
| Local heat treatment | A process in which heat treatment is applied only to a specific part or several parts of a workpiece. |
| Surface heat treatment | A process in which heat treatment is applied only to the surface layer of a workpiece to alter its microstructure and properties. |
| Thermo-chemical treatment | A heat treatment process in which a metallic material or workpiece is heated and held in a suitable reactive medium to allow one or more chemical elements to diffuse into its surface layer, thereby altering its chemical composition, microstructure and properties. |
| Conditioning heat treatment | A heat treatment carried out prior to final heat treatment to adjust the original microstructure, thereby ensuring the workpiece’s final heat treatment and/or machinability. |
| Heat treatmen in-controlled atmosphere | A heat treatment process involving heating and cooling in a furnace atmosphere where the composition can be controlled, with the aim of achieving oxidation-free and decarburisation-free conditions, whilst carbonising as required. |
| Vacuum heat treatment | A heat treatment process carried out in a heating furnace under a certain degree of vacuum, enabling oxidation-free treatment of the workpiece. |
| Ion heat treatment | A heat treatment technique utilising glow discharge in a plasma between the workpiece (cathode) and an anode, carried out in a specific atmosphere under a certain degree of vacuum. |
| High energy density heat treatment | A heat treatment technique that utilises high-power-density energy sources such as lasers, electron beams, plasma arcs, induction pulses, eddy currents and flames to heat the workpiece. |
| Quenching media | The medium used for quenching and cooling workpieces. Commonly used media include water, salt, alkali, aqueous solutions of organic polymers, oil, molten salt, fluidised beds, air, hydrogen, nitrogen and inert gases. |
| Hardenability | A material property characterised by the hardness distribution achievable through quenching under specified conditions. |
| Hardening capacity | A material property characterised by the maximum hardness achievable by steel under ideal conditions. |
| Austenitizing | A process in which steel is heated to Ac3 or above, causing the original microstructure to transform wholly or partially into austenite. |
| Annealing | A heat treatment process in which steel, non-ferrous metals or alloys are heated to a suitable temperature, held for a certain period, and then slowly cooled. |
| Full annealing | An annealing process in which steel materials or workpieces are slowly cooled after complete austenitisation to obtain a microstructure close to equilibrium. |
| Incomplete annealing | An annealing process in which a eutectoid steel or workpiece is heated to the ferrite-austenite two-phase region, held for a certain period, and then slowly cooled. |
| Stress relieving annealing | An annealing process designed to eliminate residual stresses resulting from plastic deformation, machining or welding, generally carried out below the phase transformation point of the steel. |
| Spheroidizing | An annealing process designed to spheroidise carbides in steel. Generally, to achieve spheroidisation, steel is austenitised and then cooled to the Ar1 temperature, where it is held isothermally for an extended period. |
| Normalizing | A heat treatment process in which steel materials or workpieces are austenitised, held for a certain period, and then cooled in air. |
| Isothermal normalizing | A process in which steel materials or workpieces are heated to the austenitising temperature, held for a certain period, rapidly cooled to the pearlitic transformation temperature, held isothermally for an appropriate time, and then cooled in air. |
| Quenching hardening | A heat treatment process in which steel components are austenitised and then cooled in an appropriate manner to obtain a martensitic or (and) bainitic microstructure. |
| Austempering | A quenching process in which steel components are heated to austenitise, rapidly cooled to the bainitic isothermal transformation zone and held at that temperature, causing the undercooled austenite to transform into bainite; also known as bainitic isothermal quenching. |
| Martempering | A quenching process in which a steel component, after austenitisation, is first immersed in a heat bath at a temperature slightly below the Ms point and held for a certain period; once the entire component has reached the heat bath temperature, it is removed and air-cooled to obtain a martensitic microstructure, also known as martensitic graded quenching. |
| Intercritical hardening | A quenching process in which a hypoeutectoid steel component is austenitised in the Ac1–Ac3 temperature range and then quenched to obtain a martensitic and ferritic microstructure. |
| Subzero treatment | A heat treatment process in which a steel component, after being quenched to room temperature, is further cooled in a rapid cooling device or medium (at temperatures of -100°C or higher). |
| Cryogenic treatment | A process in which a steel component, after quenching, is further cooled in liquid nitrogen (-196°C) or its vapour. |
| Effective hardening depth | The vertical distance measured from the surface of a hardened workpiece to the point where a specified hardness value (550 HV) is reached. |
| Tempering | A heat treatment process in which a steel component, after hardening, is heated to a temperature below Ac1, held at that temperature, and then cooled to room temperature. |
| Low temperature tempering | Tempering of a workpiece at a temperature below 250°C. |
| High temperature tempering | Tempering of a workpiece at a temperature above 500°C. |
| Self tempering | Utilising the residual heat within a workpiece that has been hardened locally or on the surface to temper the hardened section. |
| Temper brittlement | A brittle condition arising from the tempering of quenched steel within a specific temperature range and its subsequent slow cooling. |
| Hydrogen embrittlement | A phenomenon in which the toughness and delayed fracture strength of a workpiece are reduced due to hydrogen absorption or an excessively high hydrogen content in the raw material. |
| Residual stresses | Stress present within a workpiece in its free state at room temperature. |
| Thermal stresses | Internal stress generated by uneven expansion and contraction resulting from temperature differences in various parts of the workpiece during heating and/or cooling. |
| Transformation stresses | Internal stresses arising during heat treatment due to asynchronous microstructural transformations in different parts of the workpiece and differences in the specific volume of transformation products. |
| Solution treatment | A heat treatment process in which a workpiece is heated to a specific temperature and held there to allow excess phases to dissolve fully, followed by rapid cooling to obtain a supersaturated solid solution; generally used for non-ferrous alloys. |
| Ageing | The process of holding a workpiece at room temperature or above after solution treatment to allow second-phase particles to precipitate, thereby achieving precipitation hardening. |
| Oxidation | The process whereby oxygen, carbon dioxide and water vapour in the heating medium react with the surface of the workpiece to form oxides. |
| Decarburizing | The phenomenon whereby the carbon content at the surface of the workpiece decreases during heating, due to the reaction between the heating medium and the carbon in the steel, as well as the self-diffusion of carbon from the interior to the surface. |
| Internal oxidation | The process during heat treatment whereby oxygen generated by the reaction in the heating medium diffuses along the grain boundaries of the workpiece’s surface layer, causing the oxidation of alloying elements at the grain boundaries. |
| Carburizing | A chemical heat treatment process in which a workpiece is heated in a carburising medium and held for an extended period to increase the carbon content on the surface of the steel and create a specific carbon concentration gradient. |
| Pack carburizing | A chemical heat treatment process in which a steel component is placed in a sealed chamber filled with granular carburising agent for heating and carburisation. |
| Gas carburizing | A process in which a steel component is heated in a carbon-containing gas for carburisation. |
| Liquid carburizing | A process in which steel components are heated in a carbon-containing molten salt for carburisation, also known as salt bath carburisation. |
| Vacuum carburizing | A chemical heat treatment process in which carburisation is carried out under conditions of less than 0.1 MPa (1 atmosphere). |
| Plasma carburizing | A process in which carburisation is carried out in a carburising atmosphere of less than 0.1 MPa (1 atmosphere) using plasma discharge generated between the workpiece (cathode) and the anode. |
| Dew point | The temperature at which water vapour begins to condense in an atmosphere. The higher the water vapour content in the atmosphere, the higher the dew point. Controlling the carbon potential can be achieved by regulating the dew point (moisture content) of the atmosphere. |
| Carburizing period | The stage during which steel components are carburised under high carbon potential conditions in the carburising atmosphere, causing the steel surface to rapidly attain a high carbon concentration. |
| Diffusion period | A stage of carburising in which the carbon potential of the furnace gas is reduced, allowing the carbon from the surface of the workpiece—which has attained a high carbon concentration during the intensive carburisation phase—to diffuse into the interior, thereby appropriately reducing the surface carbon concentration. |
| Nitriding | A chemical heat treatment process in which nitrogen atoms are diffused into the surface layer of a workpiece at a specific temperature and within a specific medium. |
| Liquid nitriding | A process for nitriding carried out in a molten salt containing a nitriding agent. |
| Gas nitriding | A process for nitriding carried out in a gas capable of supplying reactive nitrogen atoms. |
| Ion nitriding | A process for nitriding carried out in a nitriding atmosphere at a pressure below 0.1 MPa (1 atmosphere), utilising plasma discharge between the workpiece (cathode) and the anode. |
| Denitriding | A process carried out to remove excess nitrogen from the surface layer of nitrided components. |
| Metal cementation | A chemical heat treatment process in which steel and non-ferrous alloy components are heated to a specific temperature in a diffusion agent containing various metals, causing metallic elements to diffuse into their surface layers. |
| Phase | Constituents within the microstructure of a metal alloy that share the same chemical composition, crystal structure and physical properties. These include solid solutions, metallic compounds and pure elements. |
| Structure | A general term referring to the overall structure observed by metallographic examination, comprising one or more phases of varying morphology, size and distribution, as well as various material defects and damage. |
| Grain | Small crystals within a polycrystalline material, separated by grain boundaries and having the same crystal orientation. |
| Grain boundary | The interface between adjacent grains in a polycrystalline material. |
| Grain size | Refers to the size of grains within a polycrystalline material. It can be quantitatively expressed using grain size number, average grain diameter, or the number of grains per unit area or volume. |
| Grain size number | A numbering system for expressing grain size established by the American Society for Testing and Materials (ASTM) and adopted by countries worldwide. The relationship between the grain size grade N and the number of grains per square inch (n) in a field of view magnified 100 times is given by n = 2N – 1. In practical inspection, the determination is generally made by comparing the microstructure at 100× magnification with standard grain size grade charts. |
| Eutectic-structure | A microstructure formed during the solidification of a metal, consisting of two or more different phases that precipitate simultaneously from the liquid phase and are closely adjacent to one another. |
| Eutectoid structure | A microstructure formed when a solid metal cools from a high temperature, consisting of two or more different phases that precipitate simultaneously from the same parent phase and are closely adjacent to one another. |
| Lamellar- structure | A microstructure comprising two or more thin, lamellar layers of eutectic or eutectoid phases that alternate and overlap, as well as other microstructures. |
| Dispersed phase | A fine, uniformly distributed solid phase that precipitates from a supersaturated solid solution or forms in the diffusion zone of a chemically heat-treated material. |
