Better heat treatment process than high frequency quenching

Integral heat treatment Integral heat treatment is a kind of metal heat treatment process which heats the workpiece as a whole and then cools it at an appropriate speed to change its metallographic structure, thus changing its overall mechanical properties. The integral heat treatment of steel has four basic processes: annealing, normalizing, quenching and tempering. "

Annealing Annealing is to heat the workpiece to a suitable temperature, adopt different holding time according to the material and size of the workpiece, and then slowly cool it to make the internal structure of the metal reach or approach the equilibrium state, or release the internal stress generated in the previous process, so as to obtain good technological performance and service performance, or make structural preparations for further quenching. Take 45 steel as an example. The metallographic structure after annealing is austenite, which becomes too soft after annealing. 45 steel is generally not annealed. Professional explanation: heat treatment process, heating mode, heating mode, heating mode, heating mode, heating mode, heating mode, heating mode, heating mode, heating mode.

Normalization Normalization is to heat the workpiece to a suitable temperature and then cool it in the air. The effect of normalizing is similar to annealing, but the obtained microstructure is finer, which is often used to improve the cutting performance of materials and sometimes as the final heat treatment of some parts with low requirements. The normalized metallographic structure of No.45 is austenite+pearlite. Professional explanation: The heat treatment process of heating steel or steel parts to the critical point of AC3 (for sub-* * * steel precipitation) or Accm (the final temperature of secondary cementite dissolving into austenite during heating, for over-* * steel precipitation) is 30℃-50℃, keeping the temperature for a proper time, and then uniformly cooling and normalizing in free flowing air. After normalizing, the precipitate of sub-steel is F+.

Quenching is to heat and preserve the temperature of the workpiece, and then quickly cool it in quenching media such as water, oil or other inorganic salt solution, organic water solution, etc. The rear steel parts become hard, but at the same time they become fragile. Take No.45 steel as an example, it is rarely quenched alone, because it is difficult to obtain the required hardness. Professional explanation: the heat treatment process of cooling the austenitized steel at an appropriate cooling rate, so that all or a certain range of unstable structures such as martensite change in the cross section of the workpiece.

Tempering tempering is to reduce the brittleness of steel parts. The quenched steel parts are kept at an appropriate temperature higher than room temperature but lower than 650℃ for a long time, and then cooled. This process is called tempering. Professional explanation: Heat treatment process that the quenched workpiece is heated to an appropriate temperature below the critical point AC 1 (the initial temperature of pearlite transforming into austenite during heating) for a certain period of time, and then cooled in a satisfactory way to obtain the required structure and properties.

Quenching-tempering is a process that combines quenching with high temperature tempering to obtain certain strength and toughness. Taking No.45 steel as an example, martensite is obtained after quenching and sorbite is obtained after tempering. In this way, the material can obtain higher strength and excellent toughness, plasticity and cutting performance.

In aging treatment, some alloys are also called solid solutions (in solid state, other components in one component dissolve to form a single uniform crystalline solid metal, and stainless steel is a typical solid solution), and then they are quenched to form supersaturated solid solutions, which are kept at room temperature or a slightly higher temperature for a long time to improve the hardness, strength or electromagnetic properties of the alloys. For example, in order to eliminate the size and shape changes of precision measuring tools or molds and parts in long-term use, aging treatment is needed.

Austenite thermomechanical treatment is an effective and close combination of pressure deformation and heat treatment to obtain good strength and toughness of the workpiece, which is also equivalent to hot forging. The most common example is the old blacksmith shop.

Vacuum heat treatment The heat treatment in negative pressure atmosphere or vacuum is called vacuum heat treatment, which can not only prevent the workpiece from oxidation and decarbonization, but also keep the surface of the workpiece smooth and improve the performance of the workpiece. After vacuum heat treatment, the deformation of parts is small, the quality is high, and the process itself is flexible and pollution-free Therefore, vacuum heat treatment is not only a necessary means for heat treatment of some special alloys, but also suitable for heat treatment of general engineering steels, especially tools, molds and precision couplings. After vacuum heat treatment, the service life is greatly improved compared with general heat treatment.

Thermalized surface heat treatment is a metal heat treatment process that only heats the surface layer of the workpiece to change its mechanical properties. In order to heat only the surface layer of the workpiece without transferring excessive heat to the interior of the workpiece, the heat source used must have high energy density, that is, the heat energy given to the workpiece per unit area is large, so that the surface layer or part of the workpiece can reach high temperature in a short time or instantly. The main methods of surface heat treatment are flame quenching and induction heating heat treatment, and the commonly used heat sources are flame such as oxyacetylene or oxypropane, induced current, laser and electron beam. For example, some shafts, gears and parts that bear variable direction load have high wear resistance on the surface, but they need good toughness and strength inside. The overall performance requirements of the workpiece can be met by surface heat treatment.

Thermochemical treatment chemical treatment is a metal heat treatment process by changing the chemical composition, microstructure and properties of the surface layer of the workpiece. The difference between chemical heat treatment and surface heat treatment is that the latter changes the chemical composition of the surface of the workpiece. Chemical heat treatment is to heat the workpiece in a medium (gas, liquid, solid) containing carbon, nitrogen or other alloying elements, and keep the temperature for a long time, so that the surface of the workpiece is infiltrated with carbon, nitrogen, boron, chromium and other elements. After the elements are infiltrated, sometimes other heat treatment processes such as quenching and tempering are needed. The main methods of chemical heat treatment are carburizing, nitriding and metallization.

Surface modification technology is a combination of chemical heat treatment and physical methods. A heat treatment technology that changes the chemical composition or structure of the surface of a material or workpiece to improve the performance of a machine part or material. It includes chemical heat treatment (nitriding, carburizing, metallization, etc.). ); Surface coating (low pressure plasma spraying, low pressure arc spraying, laser remelting composite film coating, physical vapor deposition, chemical vapor deposition, etc.). ) and nonmetallic coating technology. These technologies used to strengthen the surface of parts or materials endow parts with various new characteristics such as high temperature resistance, corrosion resistance, wear resistance, fatigue resistance, radiation resistance, electrical conductivity and magnetic permeability. To improve the reliability and prolong the service life of parts that used to work in high speed, high temperature, high pressure, heavy load and corrosive medium environment. The most common is the non-stick pan at home. Special industries and special metal products (such as gears, castings, non-stick pans, etc.) are excluded. ), most mechanical design and manufacturing do not need additional heat treatment, because steel mills have replaced designers with overheating treatment, leaving mechanical metal raw materials in a heat treatment state. Mechanical designers only need to choose.