11 knowledge points of heat treatment industry!

Heat treatment refers to a metal thermal processing process that changes the chemical composition and structure on the surface or inside of materials by means of heating, heat preservation and cooling in the solid state to obtain the required properties.

1. Normalization: Heat the steel or steel parts to the appropriate temperature above the critical point Ac3 or Acm for a certain time and then cool them in air to obtain pearlite like structure.

2. Annealing: heat the hypoeutectoid steel workpiece to 20~40 ° C above AC3, and after a period of heat preservation, slowly cool it in the furnace (or bury it in sand or lime for cooling) to below 500 ° C and cool it in air.

3. Solution heat treatment: heat the alloy to the high-temperature single-phase area and maintain the constant temperature, so that the surplus phase can be fully dissolved into the solid solution, and then rapidly cool to obtain the heat treatment process of supersaturated solid solution.

4. Aging: After solution heat treatment or cold plastic deformation, the properties of the alloy change with time when it is placed at room temperature or kept slightly above room temperature.

5. Solution treatment: fully dissolve various phases in the alloy, strengthen the solid solution, improve the toughness and corrosion resistance, eliminate stress and soften, so as to continue processing and forming.

6. Aging treatment: heat and keep the temperature at which the strengthening phase precipitates to harden and improve the strength.

7. Quenching: a heat treatment process in which the steel is austenitized and cooled at an appropriate cooling rate to make the workpiece undergo martensite and other unstable structural transformation in the whole or a certain range of the cross section.

8. Tempering: Heat the quenched workpiece to an appropriate temperature below the critical point AC1 for a certain period of time, and then cool it with a qualified method to obtain the required structure and properties.

9. Carbonitriding of steel: Carbonitriding is the process of simultaneous infiltration of carbon and nitrogen into the surface of steel. Commonly, carbonitriding is also known as cyanidation. Medium temperature gas carbonitriding and low temperature gas carbonitriding (i.e. gas soft nitriding) are widely used. The main purpose of medium temperature gas carbonitriding is to improve the hardness, wear resistance and fatigue strength of steel. The main purpose of low temperature gas carbonitriding is nitriding, which is to improve the wear resistance and anti seizure of steel.

10. Quenching and tempering: generally, the heat treatment combining quenching and high temperature tempering is called quenching and tempering. Quenching and tempering treatment is widely used in various important structural parts, especially those connecting rods, bolts, gears and shafts working under alternating loads. Tempered sorbite is obtained after quenching and tempering, and its mechanical properties are better than that of normalized sorbite with the same hardness. Its hardness depends on the high temperature tempering temperature and is related to the tempering stability of the steel and the section size of the workpiece, generally between HB200-350.

11. Brazing: the heat treatment process of heating, melting and bonding two kinds of workpieces with filler metal