Heat treatment supplementary concept

1. Annealing: refers to a heat treatment process in which metal materials are heated to an appropriate temperature, kept for a certain period of time, and then slowly cooled. Common annealing processes are: recrystallization annealing, stress relief annealing, spheroidizing annealing, complete annealing and so on. The purpose of annealing: mainly to reduce the hardness of metal materials, improve plasticity, to facilitate cutting or pressure processing, to reduce residual stress, to improve the uniformity of structure and composition, or to prepare the structure for subsequent heat treatment.

2. Normalizing: refers to the heat treatment process of heating steel or steel parts to or above (the upper critical point temperature of steel), keeping it at 30～50℃ for an appropriate time, and then cooling it in still air. The purpose of normalizing is to improve the mechanical properties of low-carbon steel, improve machinability, refine grains, eliminate structural defects, and prepare for the subsequent heat treatment.

3. Quenching: refers to heating the steel to a temperature above Ac3 or Ac1 (the lower critical point temperature of steel), keeping it for a certain period of time, and then obtaining a martensite (or bainite) structure at an appropriate cooling rate Heat treatment process. Common quenching processes include single-medium quenching, dual-medium quenching, martensite graded quenching, bainite austempering, surface quenching and partial quenching. The purpose of quenching: to obtain the required martensitic structure of the steel part, to improve the hardness, strength and wear resistance of the workpiece, and to prepare the structure for the subsequent heat treatment.

4. Tempering: refers to the heat treatment process in which steel parts are quenched and then heated to a temperature below Ac1, kept for a certain period of time, and then cooled to room temperature. Common tempering processes include: low temperature tempering, medium temperature tempering, high temperature tempering and multiple tempering.

The purpose of tempering: mainly to eliminate the stress generated by the steel during quenching, so that the steel has high hardness and wear resistance, and has the required plasticity and toughness.

5. Quenching and tempering: refers to the compound heat treatment process of quenching and high temperature tempering of steel or steel parts. The steel used for quenching and tempering is called quenched and tempered steel. It generally refers to medium carbon structural steel and medium carbon alloy structural steel.

6. Carburizing: Carburizing refers to the process of infiltrating 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 after quenching and low-temperature tempering, the surface layer of the workpiece has high hardness and wear resistance, while the central part of the workpiece still maintains the toughness and toughness of low-carbon steel. Plasticity.

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