Heat Treatment Trade Language

I. Basic Terms

Heat treatment: the process of changing the microstructure of a metal or alloy by heating, holding and cooling to obtain desired properties.

Heart: the area inside the workpiece that is not affected by surface heat treatment and usually retains its original structure and properties.

Overall heat treatment: the process of heating and cooling the workpiece as a whole (such as quenching, annealing).

Chemical heat treatment: by infiltrating carbon, nitrogen and other elements to change the chemical composition and properties of the surface of the workpiece (such as carburizing, nitriding).

Compound layer: compound formed on the surface after chemical heat treatment.

Diffusion layer: the transition layer formed by the diffusion of elements into the matrix during chemical heat treatment.

Surface heat treatment: a process that only changes the performance of the surface of the workpiece (such as high frequency quenching).

Local heat treatment: heat treatment of specific parts of the workpiece.

Preheating treatment: a process (such as annealing, normalizing) that prepares for subsequent processing (such as cutting, final heat treatment).

Vacuum heat treatment: a heat treatment process in which heating is carried out in a vacuum environment to avoid oxidation and decarburization.

Bright heat treatment: a process of heating in a protective atmosphere or vacuum to keep the surface of the workpiece bright and oxide free.

Magnetic field heat treatment: heat treatment in a magnetic field to improve the magnetic or mechanical properties of materials.

Controllable atmosphere heat treatment: the process of controlling the surface reaction of workpiece by adjusting the gas composition in the furnace (such as carburizing).

Electrolyte heat treatment: the process of heating the workpiece in the electrolyte to achieve surface modification (such as electrolytic quenching).

Ion bombard thermal treatment (glow discharge thermal treatment/plasma thermal treatment): a process of using ion bombardment on the surface of workpiece for infiltration or surface strengthening (such as ion nitriding).

Fluidized bed heat treatment: the process of heating workpieces in fluidized solid particle medium, heat transfer is uniform and rapid.

Stabilization treatment: eliminate residual stress or stabilize the tissue (such as stress relief annealing).

Shape changing heat treatment (hot mechanical treatment): a process combining plastic deformation with heat treatment (such as direct quenching after forging).

2. Heating type

Heat treatment cycle: the total time of heating, holding and cooling in the heat treatment process.

Heating system (heating specification): standardized process of parameters such as heating temperature, speed and time.

Preheating: Low temperature preheating is performed before final heating to reduce thermal stress.

Heating time: The time required from the start of heating to reach the target temperature.

Heating rate: the rate of temperature increase per unit time (℃/min).

Penetrating heating: heating in which the cross section of the workpiece is uniformly heated.

Surface heating: a process that only heats the surface of the workpiece (such as induction heating).

Control heating: the process of precise control of heating temperature and speed.

Temperature difference heating: a heating method that produces temperature gradient in different parts of the workpiece.

Local heating: heating only a specific area of the workpiece.

Vertical moving heating (scanning heating): Continuous heating along the length of the workpiece by moving the heat source (such as laser scanning).

Rotating heating: the workpiece is heated when rotating to achieve uniform heating.

Impulse heating: rapid heating with high energy density in a short time (e.g. electric pulse heating).

Induction heating: use the principle of electromagnetic induction to generate eddy current heating on the surface of the workpiece.

Insulation: maintain a constant temperature after reaching the target temperature to make the tissue uniform.

Effective thickness: the equivalent workpiece thickness used in calculating heating or cooling time.

Austenitization: the process of heating steel above Ac₃ or Ac₁ to form austenite.

Controlled atmosphere (control atmosphere): a protective atmosphere that controls the reaction of the workpiece by adjusting the composition of the gas in the furnace.

Heat absorption atmosphere: the gas (such as CO, H₂) generated by heat absorption reaction is used for carburizing.

Exothermic atmosphere: gases (such as N₂, CO₂) generated by exothermic reactions are used for oxidation protection.

Protective atmosphere: neutral or reducing gas (such as nitrogen, argon) to prevent oxidation or decarburization of workpiece.

Neutral atmosphere: a gas environment (such as high purity nitrogen) that does not chemically react with the workpiece.

Oxidizing atmosphere: a gas (such as air) that causes the surface of a workpiece to oxidize due to high oxygen content.

Reducing atmosphere: containing reducing gas (such as H₂, CO) to prevent the oxidation of workpiece.

3. Cooling type

Cooling system: specifications of cooling medium, speed, time and other parameters.

Cooling rate: the rate of temperature decrease per unit time (℃/s).

Air cooling: natural cooling in still air.

Air cooling: forced airflow to accelerate cooling.

Oil cooling: oil is used as the cooling medium (such as quenching oil).

Water cooling: water or salt water as the cooling medium.

Spray cooling: Cooling of a workpiece by spraying a liquid (such as water, polymer solution).

Cooling furnace: workpiece is slowly cooled with the furnace (such as annealing).

Control of cooling: Control of microstructure transformation (e.g., graded cooling) by adjusting cooling parameters.

4. Annealing type

Annealing: heating above the critical temperature and then cooling slowly to eliminate internal stress or soften the material.

Recrystallization annealing: eliminate cold work hardening and restore plasticity through recrystallization.

Isothermal annealing: after heating, it is cooled to a certain temperature and kept for a while to complete pearlite transformation.

Spheroidizing annealing: to spheroidize carbides and improve machinability (for high carbon steel).

Prevention of white spot annealing (elimination of white spot annealing/dehydrogenation annealing): Eliminate white spot defects in steel by slow cooling or dehydrogenation treatment.

Bright annealing: anneal in a protective atmosphere to maintain a bright surface.

Intermediate annealing: softening annealing carried out during multiple cold working processes.

Homogenization annealing (diffusion annealing): high temperature and long time holding to eliminate component segregation.

Stabilization annealing: to eliminate residual stress or stabilize the structure (such as annealing of cast iron).

Forging annealing (black core forging annealing): decompose the cementite in white cast iron into graphite to improve toughness.

Strain relief annealing: low temperature annealing (500-650℃) to eliminate residual stress.

Complete annealing: heat to Ac₃ and then slow cooling to obtain equilibrium structure.

Incomplete annealing: heating to Ac₁~Ac₃ and then slow cooling, partial recrystallization.

Packaging annealing: the workpiece is packed into a closed box and filled with protective media (such as charcoal) for annealing.

Vacuum annealing: Annealing in a vacuum to prevent oxidation.

Grain refinement treatment: grain refinement is achieved by annealing or deformation heat treatment.

Normalizing: heating to austenitization and air cooling to obtain uniform pearlite structure.

5. Quenching type

Quenching: rapid cooling after heating to obtain martensitic or bainitic structure to improve hardness and strength.

Local quenching: quenching only on a specific area of the workpiece.

Surface hardening: only hardens the surface of the workpiece (such as induction hardening).

Bright quenching (bright quenching): quenching in a protective atmosphere or vacuum to maintain a bright surface.

Water cooling quenching: water as the cooling medium (suitable for low carbon steel).

Oil cooling quenching: using quenching oil as the cooling medium (reduce deformation and cracking).

Air cooling quenching: cooling in air (for high hardening steel).

Double medium quenching (intermittent quenching/controlled time quenching/double liquid quenching): two media (such as water to oil) are used to cool successively.

Mold pressing quenching: press quenching in a mold to control deformation.

Spray quenching: cooling by spraying a liquid medium.

Spray quenching: the atomized droplets are sprayed to accelerate cooling.

Air cooling: forced air cooling.

Lead bath quenching: using molten lead as the cooling medium (used for isothermal quenching).

Salt bath quenching: the molten salt is used as the cooling medium (control the cooling rate).

Salt water quenching: salt water (such as NaCl aqueous solution) is used to increase the cooling rate.

Transmutation: the section of the workpiece is completely quenched.

Insufficient quenching: Insufficient cooling speed leads to incomplete formation of martensite.

Bainite isothermal quenching: Bainite structure is obtained at the same temperature in the transformation zone of Bainite.

Martensitic graded quenching: first quench into a low temperature medium (such as salt bath), and then air cooled to room temperature.

Aerothermal quenching (critical zone quenching): quenched after heating to Ac₁~Ac₃, retaining part of the ferrite.

Self-cold quenching: the martensite transformation is completed by using the residual heat of the workpiece itself (such as post-forging residual heat quenching).

Impulse quenching: rapid heating and cooling with high energy density (e.g., laser quenching).

Electron beam quenching: heating the surface with electron beam and then quenching by self-cooling.

Laser quenching: the laser beam is used to rapidly heat and self-cool hardening.

Flame quenching: heat and quench with an oxygen-acetylene flame.

Induction heating quenching (induction quenching): quenching after heating the surface by induction current.

Contact resistance heating quenching (electric contact quenching): using contact resistance heating surface and then quenching.

Electrolyte quenching (electrolyte fire): quenching after heating by passing electricity in the electrolyte.

Shape deformation residual heat quenching: the residual heat generated by plastic deformation is directly quenched.

Cryogenic treatment: quench and then cool to below-80℃ to reduce residual austenite.

Hardening (hardening capacity): the highest hardness that steel can achieve after quenching.

Hardening: the ability of steel to obtain the depth of martensite during quenching.

Quenched layer: the hardened part of the surface of the workpiece.

Effective hardened depth (hardened depth): the vertical distance from the surface to the specified hardness value.

Sixth, tempering

Tempering: the workpiece after quenching is heated to a certain temperature below Ac₁, kept and then cooled to reduce brittleness and residual stress and stabilize the structure.

Vacuum tempering: tempering in a vacuum environment to prevent oxidation and decarburization.

Pressure tempering: tempering under pressure to control workpiece deformation.

Self-heating tempering (self-tempering): the tempering process is completed by using the residual heat of the workpiece after quenching (such as the diffusion of the residual heat in the local quenched area).

Spontaneous tempering (spontaneous tempering effect/self-tempering): Local tempering phenomenon caused by temperature gradient during quenching cooling.

Low temperature tempering: 150-250℃ tempering to reduce quenching stress and maintain high hardness (used for tools, gauges).

Medium temperature tempering: 350-500℃ tempering to obtain elasticity and toughness (for springs).

High temperature tempering: 500-650℃ tempering to obtain comprehensive mechanical properties (tempering treatment).

Multiple tempering: multiple tempering of the same workpiece to fully eliminate residual austenite (such as high speed steel).

Refractory tempering (refractory tempering resistance/refractory tempering stability): the ability of a material to resist the decrease in hardness during tempering.

Tempering: a composite process of high temperature tempering after quenching, used to improve the comprehensive mechanical properties.

Vii. Solid solution heat treatment

Solid solution heat treatment: the alloy is heated to a high temperature so that the solute element is dissolved in the matrix and then cooled rapidly to obtain supersaturated solid solution (such as stainless steel solid solution treatment).

Water toughening treatment: solid solution treatment for high manganese steel to eliminate carbide and improve toughness.

Cementation hardening (extraction hardening/extraction strengthening): The supersaturated solid solution is precipitated to strengthen the phase (such as aluminum alloy) through aging treatment.

Aging: the process of natural change of material properties with time after solution treatment (natural aging and artificial aging).

Transformation time: the time effect phenomenon after cold plastic deformation.

Time treatment: precipitate strengthening phase (such as Al-Cu alloy) by heating to promote the precipitation of supersaturated solid solution.

Natural aging treatment: aging is completed after long time at room temperature.

Artificial aging treatment: heating to a certain temperature to accelerate the aging process.

Graded aging treatment: Aging is carried out in stages at different temperatures to optimize performance.

Over time treatment: the strength decreases and toughness increases due to the excessive temperature or time.

Martensitic aging treatment: aging strengthening in martensitic state (such as martensitic aged steel).

Natural stabilization treatment (natural aging): long-term natural placement to eliminate residual stress or stabilize size.

Regression: The aged alloy is reheated below the solution temperature to reverse the aging effect.

8. Heat treatment defects

Oxidation: when heated, the metal surface reacts with oxygen to form an oxide scale.

Decarbonization: When steel is heated, the surface carbon element is lost, resulting in a decrease in hardness.

Carbon black: free carbon particles deposited on the surface due to high carbon potential during carburizing.

Quenching cooling cracking: cracks caused by excessive cooling stress (common in complex shaped parts).

Quenching cooling distortion (quenching deformation): shape or size change caused by uneven stress during cooling.

Dimensional distortion (dimensional deformation/volume deformation): the overall volume or size change of a workpiece (such as expansion or contraction).

Shape distortion (bending deformation/shape deformation): the workpiece is bent, twisted and other geometric shape changes.

Quenching cooling stress: internal stress generated by temperature gradient and phase change difference during cooling.

Thermal stress: thermal expansion and contraction stress caused by temperature inhomogeneity during heating or cooling.

Phase change stress (tissue stress): Stress generated by volume changes during phase change (e.g., austenite to martensite).

Residual stress (residual internal stress/internal stress): the stress remaining in the workpiece after heat treatment.

Soft spot: the area with insufficient local hardness after quenching (due to uneven cooling or oxidation scale obstruction).

Overheating: the crystal boundary is oxidized or melted due to excessive heating temperature (irreversible defect).

Overheating: the grain is coarse due to excessive heating temperature (which can be repaired by normalizing).

Asymmetry: the uneven distribution of chemical composition or tissue in a material.

Cold brittleness (low temperature brittleness): the phenomenon of a sharp decrease in toughness of a material at low temperatures.

Blue brittleness: brittleness of steel in the range of 200-300℃ due to aging phenomenon.

Hot brittleness (red brittleness): brittleness caused by the concentration of impurities such as sulfur at grain boundaries at high temperature.

Hydrogen embrittlement: Hydrogen atoms penetrate the metal lattice resulting in brittle fracture (common in high strength steel).

White spot: internal microcrack formed by hydrogen accumulation in steel (silver white spot on section).

σ Phase brittleness: brittleness caused by the precipitation of σ phase in stainless steel or heat resistant steel.

Temper brittleness: brittleness caused by impurity concentration or microstructure change during tempering.

The first type of temper brittleness (irreversible temper brittleness/low temperature temper brittleness): irreversible brittleness after tempering at 250-400℃ (related to phosphorus bias).

The second type of temper brittleness (reversible temper brittleness/high temperature temper brittleness): brittleness caused by slow cooling after tempering at 450-650℃ (which can be avoided by rapid cooling).

9. Carburizing type

Carburizing: carbon is infiltrated into the surface of low carbon steel to improve surface hardness and wear resistance.

Solid carburizing: Carburizing is carried out by heating in a solid carburizing agent (charcoal + carbonate).

Carbon infiltration paste: the carbon infiltration paste is coated on the surface of the workpiece and then heated for carbon infiltration.

Salt bath carburizing (liquid carburizing): Carburizing in a molten salt bath (such as cyanide).

Gas carburizing: Carburizing by heating in a carbon-containing gas (such as propane).

Drip carburizing (drop carburizing): drop organic liquid (such as methanol + acetone) into the furnace to generate carburizing atmosphere.

Ion carburizing (glow discharge carburizing): Carburizing through ion bombardment in plasma.

Carburizing in fluidized bed: carburizing in fluidized solid particle medium.

Electrolytic carburizing: carburizing through electrochemical reaction in electrolyte.

Vacuum carburizing: carburizing is carried out by introducing carburizing gas into a vacuum environment.

High temperature carburizing: a rapid carburizing process carried out at 900-1050℃.

Local carburizing: only the specific area of the workpiece is carburized (other areas are protected by copper plating or coating).

Re-carburization: Re-carburizing the surface of a decarbonized workpiece to restore carbon content.

Carbon potential (carbon position): the carbon concentration in the furnace atmosphere when equilibrium is reached with the steel surface.

Carburized layer: the surface area where the carbon concentration increases after carburization.

Carburized layer depth: the vertical distance from the surface to the specified carbon content (e.g., 0.4%C).

Effective carburized hardened layer depth: vertical distance from the surface to the specified hardness (e.g. 550HV).

Nitriding

Nitriding (nitridation): Nitrogen is infiltrated into the surface of steel to form a high hardness nitride layer.

Liquid nitriding: Nitrogen is infiltrated in nitrogen-containing molten salts (such as cyanide).

Gas nitriding: Nitrogen is infiltrated in the atmosphere of ammonia (NH₃) decomposition.

Ion nitriding (ion nitriding): using plasma bombardment of the surface for nitriding.

A single nitriding: Nitriding carried out at a single temperature and time.

Multi-stage nitriding (multi-stage nitriding): a process of multi-stage temperature or nitrogen potential adjustment.

Denitrogenation (denitrogenation): Reducing the nitrogen content of the surface by heating or chemical treatment.

Nitride: compounds formed in the nitriding layer (e.g., Fe₄N, Fe₂₃N).

Nitrogen potential: a quantitative index of nitrogen infiltration ability in furnace atmosphere.

Nitrogen implantation layer depth: the vertical distance from the surface to the original matrix structure.